mooney 231 cruise speed

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Mooney M20K, 231/252

Mooneys m20k demands careful engine management and maintenance, but the payback comes in the form of impressive speed and efficiency..

If age mellows people, the same might be said for airplanes, at least if the airplane in question is Mooney’s M20K series. The airplane arrived in the GA market at a time when turbocharging was relatively new and the demand for high-flying aircraft was thin.

Mooney didn’t get the M20K’s turbocharging system right on the first try and the airplane developed a reputation as a maintenance hog. Thirty years later, that reputation has been mostly burnished and the fact that the M20K bores along between 160 and 200 knots on relatively little fuel has improved the model’s used price.

Still, the cabin is small and with a single door, hard to get into. For that reason and others, Mooneys have a bit of cult status to them. They are in no way everyman’s airplane in the way that a Cessna or a Piper is. But if cruising fast yet miserly is your desire, the Mooney M20K models—the 231, the 252 and the Encore—are strong contenders.

Mooney M20K Model History

Mooney came into the turbocharging game relatively late compared to other manufacturers. In 1966, Cessna pioneered the market with the T210 and made a strong showing in the single-engine, high-altitude market. Beech brought out the V35TC in 1966, but it was never as strong a seller as the A36.

Mooney wasn’t completely flat footed during the 1960s, introducing the 310-HP M22 Mustang in 1967, a big brute of an airplane that was, to some, as ugly as it was unsuccessful.

Through the 1970s, Mooney did well with small, efficient airplanes powered by Lycoming four-bangers. Mooney’s big breakthrough came in 1977, when the Mooney M20J 201 was introduced as the fruit of a clever Roy LoPresti-led aerodynamic cleanup of the venerable F-model. The Mooney 201—named for its maximum speed in miles per hour—marked a turning point for Mooney, even if the claimed speed was somewhat optimistic. In 1977, Piper had the Turbo Arrow and Mooney realized it needed to compete in this market.

The result appeared in 1979 as the Mooney 231—again, named for its top speed—or Mooney M20K. It was essentially a Mooney 201 with a six-cylinder, 210-HP Continental TSIO-360-GB in place of the 201’s 200-HP Lycoming IO-360.

The Mooney 231 airframe had a lot going for it. It was strongly built of welded 4130 steel, the gear system was all but indestructible and the handling was mannerly, easily flown by a pilot with minimal retrac experience. By modern standards, Mooney had a smash hit on its hands. It sold 246 airplanes the first year, outdistancing the 201 by nearly two to one. The fact that the two airplanes were so similar simplified the build process and likely made the project profitable from the first year.

The differences are in minor aerodynamic refinements. The K-model’s fuel capacity is 10 gallons more than the J-model, and both empty and gross weights are 160 pounds higher. Design-wise, the Mooney 231 was exactly what the buyers were looking for: a turbocharged 201.

But if buyers were hoping for the 201’s excellent dispatch rate, they got something less. Problems with the Mooney 231’s Continental engine were several fold and hurt the model’s initial reputation. The new cowling didn’t cool the engine adequately; the fixed-wastegate turbo required constant attention and was easy to mismanage; overboosting and high heat put undue stress on the engine, and it was prone to cracking cylinders and cases.

The connecting rods were prone to failure and the original magnetos were unpressurized, and would arc at high altitude. On top of all this, the TBO of the first engines was a miserly 1400 hours, later upped to 1800 hours, where it still stands.

Even with all these faults—and they were considerable—some owners achieved impressive maintenance reliability by obsessive attention to operating technique. Specifically, that meant careful leaning and attention to cowl flaps and preventive maintenance of the turbo. But not all owners were so careful—premature engine crumps were common.

Mooney 231 Refinements

With a couple of years of experience under its belt, Mooney undertook some improvements, adding a split rear cargo seat in 1982, while in 1984, a new variant of the engine—the LB1B, which is approved as a replacement for the GB—was introduced with better cooling and overboost protection. Mooney also included some aerodynamic tweaks that added 3 to 5 knots: sealed nose gear doors, a belly pan, a more streamlined tailcone and removal of one of the vent intakes. The alternate air intake system changed to address reports of icing-induced power loss.

While these fixes certainly helped, the improvements were hardly night and day. By 1986, further retooling produced the Mooney 252TSE for Turbo Special Edition. The Mooney 252, while still an M20K, is significantly different from the Mooney 231. Another variant of the engine was fitted, the -MB1. The induction and cooling systems were reworked and a new intercooled, density-controlled, variable wastegate AiResearch turbocharger replaced the original, fixed wastegate Rajay/Rotomaster unit. Other changes included infinitely adjustable electric cowl flaps to replace the original dual manual flaps. There was a vernier throttle control, more elbow room and new-look radiused windows.

The Mooney 231’s original 60-amp, 14-volt electrical system was upgraded to a 70-amp, 28-volt system. This was much needed, since a fully loaded K-model could max out the electrics long before the days of moving maps. An electrically driven backup vacuum pump was made standard equipment.

The Mooney 252 also got further aerodynamic tweaking in the form of gear doors that fully enclose the wheels when retracted and cover the wells when the gear is extended. The 252 also got an increase in gear-extension speed to 140 knots, up from 132 knots. Maximum speed with gear extended is 165 knots for the 252. In all, 889 231s were produced between its introduction in 1979 and 1985. The 252, introduced in the middle of the GA slump of the 1980s, is less numerous. Production totaled, ironically, 231 airplanes. The K-model made a brief resurgence in 1997 as the Encore, when Mooney was going through yet another of its many reorganizations. But it was not to be and the model was dropped again in 1998. Meanwhile, the so-called long-body models, specifically the M20M TLS and later the M20R Ovation and Acclaim eventually came to dominate the Mooney line.

Mooney M20K Performance

The K-model lives in a league of its own when measured against the narrow market segment of four-place, turbo retractables. At cruise, the Mooney 231 outstrips its competitors—the turbo Arrow, the 182 RG and Commander TC—by roughly 20 knots, despite the fact that the 231 MPH (196 knots) top speed isn’t reachable under real-world conditions and probably at all.

Realistic max cruise is about 190 knots for the 231, but 170 to 175 knots is more like it. The 252 is about 10 knots faster, thanks to intercooling. Both M20Ks win the altitude battle as well, with a maximum operating altitude of 24,000 feet for the 231 and 28,000 feet for the 252, versus 20,000 feet for the Cessna and Piper. The Mooneys outclimb the others by about 150 FPM.

Due to physiological considerations, however, high teens to low 20s are the airplane’s best envelope. At lower altitudes, turbocharged airplanes aren’t much faster than their normally aspirated siblings.

In fact, the Mooney 231 is actually slower than the 201 below 8000 feet, due to cooling drag. The J-model will also outclimb the K-model below 8000 feet.

Many owners operate 252s conservatively. One owner told us that 65 percent power yields 170 knots at 10,000 feet and 200 knots at FL210, burning 11.5 GPH. The 231’s numbers are proportionately lower at high altitudes, although the difference lessens the lower one goes.

With 75.6 gallons of usable fuel, the 252 can climb to FL280 and operate a total of 4.9 hours, or just under 990 nautical miles still-air range with reserves. The 231 has comparable range and endurance, but can’t fly as high.

How the Mooney 231 Differs from the Mooney 252

The improved powerplant installation makes for a significant operational difference between the 231 and 252. The engine still produces 210 HP, but it does so at a markedly lower manifold pressure: 36 inches for the 252 versus 40 inches for the 231, thanks to the improvements in the tuned induction, cooling and the turbo system.

The 252’s induction and cooling air intakes are separate from one another. Induction air enters through a NACA scoop on the side of the cowling, is turned 90 degrees to minimize induction icing through inertial separation and passes through a larger, less-restrictive air filter. It’s then compressed and run through a 42-square-inch intercooler.

The result is dramatically lower temperatures for the induction air, from 60 degrees F at lower altitudes to 120 degrees F up high. That means more power at higher altitudes and a wider detonation margin. The 231’s critical altitude is only 14,000 feet, while the 252’s critical altitude is 24,000 feet. In practical terms, this means that the 252 can continue to climb at about 1000 FPM into the mid-20s, can fly higher and is faster once up there.

The most important difference between the Mooney 231 and 252 lies in engine management. The revised powerplant installation in the 252 made an enormous difference and makes the 252 a more desirable airplane. Because the Mooney 231 has a fixed wastegate, the pilot must constantly monitor manifold pressure and fiddle with the throttle to keep it within limits. Bootstrapping and overboosting are constant worries. Thanks to its automatic wastegate, the Mooney 252 doesn’t suffer these foibles.

Mooney 231/252 Handling

The 231/252 series handle like typical Mooneys: relatively heavy in roll and pitch, with good stability. The K-models have greater pitch authority, thanks to a slightly larger elevator and the longer engine makes it somewhat nose heavy. That can make flaring a challenge with a forward CG, but nothing like, say, a Cessna 182.

Pitch change with gear extension/retraction is slight, but flap extension produces a nose-down moment. Transition from full flaps to trimmed for go-around takes heavy pressure on the yoke and fast action on the trim. Using the electric trim, anticipation of configuration changes helps reduce pilot effort.

Speed control is essential when approaching and landing any Mooney. Approach too fast and the K-model will float. Try to plant it on the ground and it will fight back, porpoising vigorously and striking the prop if uncorrected. This is a common accident for all Mooneys, not just the K-model.

Because of its ability to fly fast, some owners say the best addition ever devised for Mooneys are speed brakes. These are especially useful for the Mooney 231, which doesn’t have the 252’s higher gear limits. (Speed brakes are standard on Mooney 252s.)

Ground handling isn’t great. The airplane is low slung and the Mooney’s stretched-out seating position hinders visibility on the ground. It also makes gaining purchase on the brakes difficult. The wing span (36 feet, 1 inch), combined with the wide turning radius of 41 feet, makes negotiating a crowded ramp challenging. One other caution: Many Mooneys suffer damage to the nose gear trunion when towing turn limits are exceeded via power towing. Owners learn to watch the ramp rats carefully.

Mooney 213/252 Payload and Cabin

On paper, the Mooney 231 and 252 have the same loading characteristics. In reality, however, the typical 252 weighs more, simply because it has more equipment. Neither airplane is a stellar load-hauler. Gross weight is 2900 pounds and basic empty weight is 1800 pounds, usually more. Real-world, full-fuel payloads are on the order of 400 to 500 pounds, making the M20K a useful two-place airplane, with generous baggage. Thanks to its fuel efficiency and good endurance, however, there’s flexibility built into the load-carrying equation. The latest Mooney M20K, the Encore, has about 200 pounds of additional load, thanks to beefier landing gear. Staying within the CG is easy and there’s no worry of aft-tending CG as fuel is burned off.

The baggage compartment is large, with a capacity of 120 pounds, although the high sill door makes it difficult to wrestle large objects into the airplane. Baggage capacity can be increased by folding the rear seat backs down together or individually.

Mooneys are fast and efficient because they have low-drag airframes with a small frontal area. That translates into cramped quarters. The seating position is quite different from that of most airplanes. It’s more of a sports-car posture than an upright seating regime. There’s plenty of leg room fore and aft, but less lateral room. Those of below-average height may find that they can’t reach the rudder pedals without a booster cushion behind their backs or pedal extensions.

Early Mooneys tended to be Spartan in interior arrangements. But by the time the 231/252 appeared, Mooney recognized the need for more modern if not luxurious appointments. Thanks to a bit more elbow room and somewhat plusher finish, the 252 is more comfortable than the 231. The 252 is also quieter and many feel it’s the quietest of all Mooneys, thanks in part to the induction system and the fact that things quiet down the higher you fly.

The panel layout is quite good, with one seemingly obvious feature that has probably averted many incidents: The gear selector is located high in the middle of the panel so it’s hard to miss. The flap switch is located low on the center console, along with the trim/flap indicators and, in the 252, cowl flap controls.

The power gauges are on the far right and angled toward the pilot. Engine gauges are well-placed, right under the glareshield in front of the pilot. The panel also has a good selection of annunciator lights at the top of the radio stack.

Mooney 231/252 Maintenance

Airframe-wise, Mooneys are relatively trouble-free. Long-standing caveats include the potential for corrosion of the cabin frame tubes—particularly if the windows develop leaks—and the typical fuel tank leaks that plague all Mooneys. Systems in general are simple and robust. The steel gear legs gear have no oleo struts, relying instead on rubber donuts for shock absorption. These need to be replaced periodically. There’s no complex electro-hydraulic system driving the gear as is found on Cessnas—Mooneys are electromechanical. The flaps, too, are electric, and both are relatively trouble-free.

The Mooney powerplant, however, is another matter. Difficulties fall into several categories: magnetos, con rods, cylinders and turbos. Most airplanes have been retrofitted with pressurized mags, but check any used model to be sure. The same applies to connecting rods. The suspect rods are Continental part number 626119 and have a C logo with a circle around it. Only a barn dweller would still have the old ones.

Many turbocharged models encounter mid-run cylinder problems of some sort and the K-model is no different. These include the full litany: worn valves and guides, broken rings and cracked jugs. Mid-time turbo and magneto replacements aren’t uncommon, but they aren’t a sure bet, either. The 231’s fixed wastegate means the turbo is working constantly and the engine is susceptible to overboosting.

The Mooney 252 doesn’t suffer these problems, although it had trouble with cracked tubes in the induction system before Continental came up with flexible tubing. Even though the 252’s engine installation is less troublesome than the 231, temperatures and stresses on turbocharged engines are greater than on normally aspirated engines. Regular inspections and proactive maintenance is a must for reliable dispatch rates.

Mooney 231/252 Mods and Clubs

By far the most desirable mods for the Mooney 231 are those that make it more like the 252. These include intercoolers from Aircraft Modifications, Inc. (253-851-6440) and the Merlyn Black Magic upper deck controller; contact www.merlynproducts.com or 800-828-7500. Both work as advertised and help eliminate the 231’s engine problems. They also make the 231 perform almost as well as a 252. We consider the Merlyn a must-have for the 231.

There are fewer speed mods for the K-model than for earlier Mooney types, such as the C, F and J models. Single-piece belly skins, minor speed mods, rudder and elevator hinge covers and oversized bushing kits for the nose gear are available from Lake Aero Style and Repair ( www.lasar.com , 800-954-5619).

Precise Flight ( www.preciseflight.com , 800-547-2558) offers speed brakes for the K-models. LoPresti Speed Merchants ( www.speedmods.com , 800-859-4757) has an HID landing light for the K-model and hub caps with filler valve access holes Mod Works, another well-known Mooney house, retains some 39 STCs for Mooneys. However, the facility was wiped out during Hurricane Charley in 2004 and is out of operation indefinitely. Mod Works can still be reached at 941-637-6770.

A big-dollar mod, the Rocket conversion, replaces the TSIO-360 with a 305-HP Continental TSIO-520-NB, yielding 220-knot-plus cruise speeds. Although the conversion is discontinued, these turn up on the used market. Contact www.rocketengineering.com. The thirstier engine in that mod will benefit from larger fuel tanks. Monroy Aerospace ( www.monroyaero.com ) has an STC to raise capacity to 106 gallons. Hartzell offers three-blade prop conversions ( www.hartzellprop.com ).

Currently, there are two Mooney Associations, the Mooney Aircraft Pilots Association and Mooney Owners of America. Both have membership benefits, technical support and magazines. Contact MAPA at www.mooneypilots.com and MOA at www.mooneyowners.com .

Mooney 231/252 Owner Feedback

I purchased my 1981 Mooney 231 when I lived in Colorado. A turbocharged plane was necessary to fly west over the mountains. This made it possible to go to Steamboat Springs for breakfast or lunch, plus it enabled a more direct route to Scottsdale, Arizona.

My 231 has built-in oxygen for all seats and a large oxygen bottle which must be periodically removed from the battery compartment for recertification. This is not an inexpensive proposition and may keep the airplane on the ground, or at least at lower altitudes, until it’s accomplished.

One of the pleasures is seeing the GPS recording in excess of 200 knots ground speed returning from the mountains to the flatlands under normal power settings. Speed brakes are essential to come down from 17,000 without super cooling the engine. However, I used around 150 to 165 knots for normal flight planning.

Learning to land the Mooney was problematic for some reason. Coming in with half flaps and adding a little power prior to touchdown seemed to help, but I am still working on consistency without ballooning or dropping it in. Sometimes it is difficult to judge how high you are above the runway compared to other airplanes. The rudder pedals are small and one needs to make sure that you are not landing with your feet on the brakes.

Michael Williams

Horseshoe Bay, Texas

After renting Mooneys for almost 20 years, I became involved in a flying club that had Piper Cherokee 180s (108 knots on 8.2 GPH). My wife scared me on a Cherokee flight asking, “What’s wrong with the plane?” After I checked everything, she responded that it was taking so long to arrive at our destination. That’s why in 2001 we purchased a 1980 Mooney 231.

It has several upgrades, including a three-blade McCauley prop, electric standby vacuum pump, intercooler for the turbocharger, the Garmin GNS530/430 combination in lieu of the standard BendixKing radios and an Aspen PFD.

As this is primarily a go-higher, go-faster plane with a reputation for an engine that runs hot, I changed to GAMI fuel injectors and took out the old mechanical engine gauges after installing a JPI EDM930. The EDM930 is a critical change and allows me to operate LOP in cruise, which totally controls the propensity for hot CHTs. During ROP in cruise, it was not uncommon to see cylinders in the 385-425 degree range. Operating LOP, the temps are 345-380. Flying at 12,000 feet, LOP and at 65 percent power I experience 160-165 knots at 9.7-10.1 GPH. At 14,000 feet the fuel burn is almost the same, but the speed is bumped to 166-170 knots.

The fuel tanks on Mooneys seem to leak at 20-year intervals so I had mine resealed, while also adding two 20-gallon aux tanks. The fuel selector remains simple—left and right—so there is no added complexity. If I can accommodate the weight, I could fly 1400 NM nonstop. I make several six-hour nonstop trips a year from Tampa, Florida, to Traverse City, Michigan, on about 72-76 gallons (no-wind flight planning). That leaves plenty of fuel reserve.

Mechanically, the aircraft is very robust with major components like the landing gear requiring few if any repairs. The landing gear in all the Mooneys I’ve flown has been bulletproof; the electric gear is rapid actuating and useful to slow things in the pattern if the aircraft is not fitted with speed brakes. The K-model can be fitted with either long-range tanks or speed brakes, but not both.

Annual inspections are typically less than $1600 unless there is an issue (which thankfully hasn’t happened in several years). Parts availability has always been good.

As it is hangared in Florida, I had the tubular steel structure checked for rust and corrosion and none was found. The aluminum had only two places of corrosion smaller than the size of a dime around the fuel filler cap. The TSIO-360LB engine was a source of issues, including Continental cylinders which developed cracks between the valves and become non-repairable. My current cylinders have over four years in service without a problem. Zephyr Engines here in Central Florida has been excellent both during and after the installation of the rebuilt engine, offering outstanding support.

Alternators (there is only one on the early 231 models) tend to be a sore spot and I have installed three in 10 years. It is the gear-driven design on the rear of the engine which is subject to heat. Finally, there is an STC for a modern model, which is much lighter and hopefully more durable.

As this is a slick, relatively high-performance machine, I take recurrent training offered through MAPA. It offers a two-day course in various locations, and the course and instructors are truly outstanding. If you plan to operate an aircraft like this, recurrent training is a must.

I really like my 231. It is fun to fly, it can fly approaches at 130-plus knots when required to sequence in with the jets, it is durable—with great parts availability—and it can sip gas (while LOP) and still make decent speeds.

Bob Cochell

Tampa, Florida

My Mooney 231, N10162, was originally showcased in a Mooney company product photo shoot. Purchased approximately eight years ago following an extensive renovation in Texas and ferried to Connecticut, I quickly completed type-specific training with local designated examiner Wally Moran. Our 231 had approximately 700 hours total time when we took delivery, plus it had new paint and a new interior.

We fly the airplane approximately 50 hours per year, and as an instrument-rated commercial pilot I typically complete a minimum of two IPCs annually, as well as at least one FAA Wings program phase.

We base the aircraft at Hartford Brainard Airport in Connecticut and have it maintained by Total Aircraft Maintenance on the field. N10162 boasts an intercooler, RayJay turbocharger, King KFC200 autopilot, a Garmin GNS430, plus an HSI system.

We make good use of the oxygen system, since the aircraft can cruise up to 24,000 feet. We typically cruise at 170 knots at 58 percent power while burning roughly 10.5 GPH.

The aircraft is always hangared. Including hangar fees, insurance, annual inspections, plus our careful attention to avionics and maintenance work, the hourly cost of operation is approximately $275.

With a comfortable interior—and with styling similar to a sports car—my wife Cheryl and I typically enjoy flights from Connecticut to Maine and Nantucket, Massachusetts. So far our longest flights have been to Michigan and Minnesota.

Like so many Mooney pilots we adore our 231’s speed and efficiency. We live by the Mooney creed: We love to fly—fast.

Tony Crespi

Hartford, Connecticut

Because of its ability to fly fast, some owners say the best addition ever devised for Mooneys are speed brakes. These are especially useful for the 231, which doesn’t have the 252’s higher gear limits. (Speed brakes are standard on 252s.)

Payload/cabin

On paper, the 231 and 252 have the same loading characteristics. In reality, however, the typical 252 weighs more, simply because it has more equipment. Neither airplane is a stellar load-hauler. Gross weight is 2900 pounds and basic empty weight is 1800 pounds, usually more. Real-world, full-fuel payloads are on the order of 400 to 500 pounds, making the M20K a useful two-place airplane, with generous baggage. Thanks to its fuel efficiency and good endurance, however, there’s flexibility built into the load-carrying equation. The latest M20K, the Encore, has about 200 pounds of additional load, thanks to beefier landing gear. Staying within the CG is easy and there’s no worry of aft-tending CG as fuel is burned off.

The powerplant, however, is another matter. Difficulties fall into several categories: magnetos, con rods, cylinders and turbos. Most airplanes have been retrofitted with pressurized mags, but check any used model to be sure. The same applies to connecting rods. The suspect rods are Continental part number 626119 and have a C logo with a circle around it. Only a barn dweller would still have the old ones.

The 252 doesn’t suffer these problems, although it had trouble with cracked tubes in the induction system before Continental came up with flexible tubing. Even though the 252’s engine installation is less troublesome than the 231, temperatures and stresses on turbocharged engines are greater than on normally aspirated engines. Regular inspections and proactive maintenance is a must for reliable dispatch rates.

By far the most desirable mods for the 231 are those that make it more like the 252. These include intercoolers from Aircraft Modifications, Inc. (253-851-6440) and the Merlyn Black Magic upper deck controller; contact www.merlynproducts.com or 800-828-7500. Both work as advertised and help eliminate the 231’s engine problems. They also make the 231 perform almost as well as a 252. We consider the Merlyn a must-have for the 231.

A big-dollar mod, the Rocket conversion, replaces the TSIO-360 with a 305-HP Continental TSIO-520-NB, yielding 220-knot-plus cruise speeds. Although the conversion is discontinued, these turn up on the used market. Contact www.rocketengineering.com . The thirstier engine in that mod will benefit from larger fuel tanks. Monroy Aerospace ( www.monroyaero.com ) has an STC to raise capacity to 106 gallons. Hartzell offers three-blade prop conversions ( www.hartzellprop.com ).

Owner feedback

Michael Williams Horseshoe Bay, Texas

Bob Cochell Tampa, Florida

Tony Crespi Hartford, Connecticut

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1979 - 1985 MOONEY M20K 231

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Single engine piston aircraft with retractable landing gear. The M20K 231 seats up to 3 passengers plus 1 pilot.

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Total Variable Cost ( 83.8 Hrs ) Cost Per Hour = $127.23 Cost Per Mile = $0.67

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Socata tb-21 tc trinidad (1986 - 2005).

Typical Price: $151,384.00 Total Cost of Ownership: $25,417.20 Best Cruise: 187 KIAS ( 4 ) Best Range: 981 NM ( 1 ) Fuelburn: 16.4 GPH ( 3.1 )

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Mooney 231 and 252 M20K

Mooney Website

Albert Mooney and his brother Arthur founded the Mooney International Corporation in 1929. Together, they established the company in Wichita, Kansas. However, they faced the perils of a crashing economy. When the Great Depression struck in 1930, Mooney went bankrupt. While the brothers worked other jobs, Albert fed into Mooney Aircraft Incorporated – eventually bringing in financial bankers Charles Yankey and W. L. McMahon.

Mooney’s first aircraft was the Mooney Mite M-18, a single-seater aircraft designed to entice ex-fighter pilots post-military service. This plane remained in production until the 1950s. By 1953, Mooney moved to Kerrville, Texas. From there, the M20 sped production and took its first flight in 1953. It received its certification in 1955. Sales started slow but picked up as the aircraft became known for its speed through its Lycoming O-320 engine.

Since its founding, Mooney has experienced many setbacks and hardships, mostly due to the economy. Mooney has filed several bankruptcies and has had many different owners. Mooney once even operated under Chinese leadership through its ownership by Soaring America. While production resumed in Kerrville, Chinese investors had other developments and projects in mind. One such project included the introduction of two new M10 models in 2014. However, the entire project was canceled in 2017.

Mooney shut down in 2019 and again in 2020 – furloughing or laying off its employees due to the pandemic. Even after reopening, Mooney continued to search for an investor. By the fall of 2020, a group of aircraft owners and pilots named US Financial, LLC, bought a majority share of Mooney from Soaring America. Mooney’s current owner and CEO is Jonny Pollack.

Early Wood Construction

Before its metal til appeared in 1958, Mooney’s earlier M20 models featured wooden wing and tail construction. These models showcase their strength and durability in earlier advertisements and marketing campaigns. However, these aircraft are becoming rare as their wood properties require careful inspection and expensive maintenance. Furthermore, wood-made components are susceptible to rot, which is catastrophic to the plane’s integrity.

Mooney’s wooden wing and tail construction allow the aircraft to fly at a faster pace, but there are a confirmed number of incidents of wooden tails breaking up in flight due to water damage and resulting rot. The breakup of these parts while in flight proves it to be more dangerous than a similar model made of metal and other fortified materials. Because of the severity of these incidents, Mooney delivered 166 M20As before halting production.

Country of Origin: America

Mooney 231 M20K Statistics (1985)

• Maximum Speed: 200 kts
• Maximum Range: 980 nm
• Maximum Occupants: 4
• Range Of Years Manufactured: 1979-1985
• Total Aircraft Build: 1,118
• Current Operational Aircraft: Unknown
• Useful Load: 950 lbs
• Average Sale Value: $140,967
• Average Days On Market For Sale: Unknown

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Mooney M20K 252TSE Statistics (1990)

• Maximum Speed: 219 kts
• Range Of Years Manufactured: 1986-1990
• Useful Load: 778 lbs
• Average Sale Value: $207,039

Operational Resources

Operations manual, maintenance document, local resources.

• Mooney Aircraft Pilots Association
• Mooney Contact & Support

Manufacturer

• BWI Aviation Insurance
• Mooney Aircraft Insurance
• Travers Aviation Insurance
• AOPA Insurance
• Global Aerospace

Mooney 231 M20K & M20K 252TSE Details

In addition to its improved performance, the interior of Mooney’s 231 seats four with optional leather upholstery. It has 17 cubic feet of baggage space that extends to nearly double the size when its rear seats are down. Panel updates include internally-lit instrumentation, more accurate oil-pressure, and fuel-pressure transducers, and other small changes.

Mooney’s turbocharged M20K 252TSE seats 4 with an increase in shoulder and elbow room and center armrests for front and rear passengers. Side window treatments match the rest of the aircraft’s theme with accent paint.

Mooney’s 231 is a two-blade propeller aircraft powered by a turbocharged TSIO-360LB1B engine that runs cooler for added performance. A major upgrade to its engine includes zinc and phosphate-coated cylinder walls, which protects them from corrosion. This aircraft also has cylinder walls enhanced with nitrite, a hardening agent, and a cast steel compression ring guide in each piston.

The M20K 252TSE is a single-engine retractable aircraft with a turbocharged Continental TSIO-360-MBI engine. The engine for this aircraft improves the flow of air and fuel through the engine so that it runs cooler. The turbocharged version also has a two-blade propeller and a single electrically-operated cowl flap for better climb and descent.

A 1985 Mooney M20K 231 may or may not contain the following standard avionics:

• King Silver Crown Avionics Equipment
• KFC 200 Flight Control System
• Sperry WeatherScout Color Weather Radar
• 3M Storms Cope
• Texas Instruments 9100 Loran Receiver
• 76-Cubic-Foot Oxygen System (Optional)
• Propeller Deicing System (Optional)

A 1990 Mooney M20K 252TSE may or may not contain the following standard avionics:

• Garmin 430 Nav/Com WAAS GPS
• Apollo MX20 MFD
• King 155 Nav/Com with ILS
• S-TEC 60 Autopilot with Altitude Select
• PMA 7000S Audio Panel
• Insight TAS 1000 System with Wind Indicator
• GTX 330 Transponder
• D&M 121.5 ELT

Specifications

Mooney 231 m20k:.

• Max Seats: 4
• Max Take-Off Weight: 2,900 lbs.
• Configuration: Single Engine, Piston, Retractable Gear
• Wing Span: 36 ft. 1 in.
• Length: 25 ft. 5 in.
• Height: 8 ft. 3 in.
• Take-Off Run (50 ft.): 2,200 ft.
• Cruise: 174 kts
• Range: 1,182 nm
• Take-Off Run: 1,250 ft.
• Landing Roll: 1,147 ft.

Mooney 252 M20K:

• Height: 8 ft. 4 in.
• Length: 26 ft. 8 in.
• Wing Span: 36 ft. 6 in.
• Gross Weight: 2,900 lb.
• Empty Weight: 1,800 lb.
• Fuel Capacity: 75 US gal
• Range: 890 nm
• Max Speed: 219 kts
• Cruise Speed: 201 kts
• Stall Speed: 59 kts
• Take-Off Ground Roll: 1,250 ft.
• Take-Off Ground Roll (50 ft.): 2,200 ft.
• Landing Ground Roll: 1,140 ft.
• Landing Ground Roll (50 ft.): 2,300 ft.
• Rate Of Climb: 1,080 fpm
• Service Ceiling: 28,000 ft.

Mooney M20 Models

Early Mooney models featured wooden structures in the wings and tail that proved to be a safety hazard after several incidents resulted in broken tails while in flight. 1960 saw the last of these wooden features. This particular model has a Lycoming O-320 engine, and Mooney made a total of 200.

This 1958 variant saw an engine change to the Lycoming O-360 – kicking up its horsepower to 180 from 150. 499 of these were created from 1958 to 1960.

The first Mooney aircraft without wood parts, this 1961 model kept the same engine as the M20A. After getting rid of its older wooden features, all future M20s include materials made of all metal and other necessary elements.

M20C Ranger

In this 1962 model, the M20C made a few tweaks to reduce some of the issues the M20B had. It changed to the Hartzell 74″ Constant Speed HC-C2YK/7666-2 propeller with Hartzell governor, D-l-4, and a reduced cowl flap opening. The Ranger’s sound and lighting improved. Other changes include its weight, balance, and a few other alterations. This aircraft’s exhaust system becomes a Hanlon & Wilson exhaust, which is more lightweight and efficient.

M20D Master

The 1963 M20D featured a Lycoming O-360 engine with 180 horsepower. Mooney made a total of 161 of these models.

M20E Super 21 / Chaparral

Horsepower on this 1964 aircraft increased to 200. Additionally, it featured a Bendix fuel injection and altitude power boost. It also saw an engine shift to the Lycoming IO-360.

M20F Executive 21

The 1966 M20F kept the same horsepower as its predecessor. Furthermore, its fuselage extended by 1 foot and its cabin by 10 inches. This model maintains the same engine as the Super 21 with the Lycoming IO-360, but now with Power Control.

M20G Statesman

The 1968 Statesman M20 model returned to a Lycoming O-360 engine, returning its horsepower to 180. The M20G also had an upgraded long (F model) fuselage, fuel capacity of 52 gallons, power control, and a one-piece windshield.

The introduction of the M20J is when many started to take notice of Mooney in the aviation industry. The M20J model was often referred to as the Mooney 201 because it could fly at 201 miles per hour (323 km/h) using its 200 horsepower (150 kW) engine. Here, the propeller is squared off and has a drag reduction similar to that of the F model.

Deemed “the right approach to the eighties” by The AOPA Pilot Magazine (March 1980), Mooney’s 231 adjustments include addressing its heat-management problem with a reworked Continental TSIO-360 engine to run cooler during operation. The base price for this aircraft in 1984 started at $86,950 with add-ons available.

M20K 252TSE

Also supercharged, this 1986 M20K model came with a Continental TSIO-360-MB engine with the same configuration as its 1979 M20K relative.

M20K Encore

This 1997 M20K Encore model featured a supercharged engine through the Continental TSIO-360-SB. This kicked up its horsepower to 220 compared to its predecessor at 210. Only 27 of these were made.

This 1988 M20 model had a horsepower of 217 but was not turbocharged. This model is unique as it has a Porsche PFM 3200 engine, created using the engine design of Porsche’s 911 Carrera. This model saw a few changes to its throttle with a replacement mixture and propeller controls using single power control. The M20L PFM’s mixture and propeller rotation speed was adjusted automatically based on the setting of this single control. This particular model lasted only a short time, and only 41 were ever made.

M20M TLS / M20M Bravo

Unlike the M20L, the 1989 M20M made an engine switch to the Lycoming TIO-540. This turbocharged aircraft had a horsepower of 270 until 2006, with a total of 314 units.

M20R Ovation / Ovation 2

The 1994 Ovation saw a rise in horsepower to 280 using a Continental IO-550-G engine. This model featured an extra long body until 2001 with 266 units.

M20S Eagle / Eagle 2

The 1999 M20S continued using the same Continental IO-550-G engine as the Ovation with a reduced horsepower of 244. This model also featured a long body, 2-axis STEC autopilot, and 75-gallon capacity.

M20TN Acclaim

This 2006 model changed engines to the Continental TSIO-550-G and had a horsepower of 280. Mooney only produced this turbocharged model from 2006 to 2008.

M20U Ovation Ultra

As one of the most recent models, the 2017 Ovation Ultra has a Continental IO-550-G engine and 280 horsepower. Mooney’s starting price for this model is $689,000.

M20V Acclaim Ultra

This 2017 model uses a Continental TSIO-550-G engine with a horsepower of 280. It is turbocharged and has a set price of $769,000.

Top Mooney M20 Questions

The following are FAQs for Mooney’s M20.

How much does it cost to operate a Mooney M20K?

The average Mooney operating cost is between $60 to $80 per hour, depending on the exact make and model.

How fast is the Mooney M20K?

Mooney’s M20K has a maximum speed of 200 knots.

How fast is the M20K cruise?

At 75% power, Mooney’s M20K has a cruise speed of 191 knots with a maximum operating altitude of 24,000 feet.

Is Mooney’s M20K fast and efficient?

Because Mooney offers turbocharged variations, pilots favor its speed and responded fairly quickly in the past to be more responsive to customers’ wishes. Of course, after ditching its wood features for an all-metal structure and meshing its M20J airframe with a turbocharged engine, its speed, and additional features continued to impress pilots and aviation enthusiasts.

Related VREF Resources

Mooney Mark 21 M20C And Ranger M20 BCG Aircraft Spotlight Mooney M20J 201/205 Is Buying An Aircraft To Build Flight Time A Good Idea?

Find Extensive Data On Mooney’s M20 Series

Find all of the information you need at VREF Online.

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M20K 231 High Altitude Cruise

By jlunseth June 6, 2011 in Modern Mooney Discussion

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I have been on a mission to figure out how to operate my 231 in all the parts of its envelope.  The certified ceiling is 24,000.  We tried FL230 last year and had some excitement with "high altitude miss" where improper pressurization of the magneto leads to arcing across the cap in the thin air in the flight levels.  Got that fixed at annual over the winter, but just have not had the right circumstances to go that high again.  This weekend my copilot and I went to Kalispell from Flying Cloud in Minneapolis.  We had the usual share of adventures.  The vacuum pump pooped out on the first leg of our trip to KGPI, fortunately in VMC.  I made the mistake of leaving the plane on autopilot for a little bit while we decided what to do and then told ATC we needed to divert to KBIS (Bismarck).  As the AI wound down, the plane started bucking and gained a little altitude, which concerned ATC (because they knew our circumstances by then), but I disconnected the AP and made an uneventful landing.  Lots of flooding at Bismarck and throughout ND.  Bismarck Aero found a mechanic and the pump was changed in short order, but it was too late to continue so we stayed the night in the FBO at BIS.  For future information, they have a sleeping room with two single beds, worked out really well.  The trip out was at FL220, the winds aloft were not too bad, but another 2,000 feet to the service ceiling and they were screaming and in the wrong direction, so we did not have a chance to try FL240.

On the way back we got our chance.  ATC gave us FL240 for the leg from KGPI to our refueling stop at BIS.  As those of you know who have been on this site for awhile, my 231 has the Merlyn wastegate and Turboplus intercooler.  The Merlyn increases the critical altitude (the altitude at which the aircraft can no longer generate 100% HP), but I had never tested out where this happened with the Merlyn.  The critical altitude on the 231 as it came from the factory with the fixed wastegate was 15,000 +/- 500.  We found it at 22,500 with the Merlyn, using the numbers generated by the JPI's %HP algorithm.  It was quite a bit warmer than a standard day, -24C at FL240 which is around 10 deg. warm, so I suspect we would get better on a standard day or a cold winter one.  It was not until the last 1,000 that the climb rate reduced from my standard 500 fpm cruise climb.  We hit about 300 fpm from 23,000 to 24,000.

At altitude the plane quickly accelerated to about 182 TAS before I pulled it back to cruise.  We cruised at 27.4 MP and 13.7 gph.  The 13.7 seems to be the magic figure for my aircraft in a cruise range of 75-80%.  I am at the point where it does not seem worth it to go through the lean procedure with the JPI, I just pull it back to 13.7 and all the cylinder temps fall in line in the 370' and 380's at altitude.  Bear in mind that in the high thin air, cooling is not as good as lower down, so those are good working temps.

We made the trip from KGPI to KBIS in a flight time of 3:00.  We hit a ground speed at one point at cruise of 234 knots.  My copilot got a picture of a 233 or maybe the 234 that I will post when I get it.  Not too shabby for a fuel mileage of close to 20 mpg. 

I have a couple of goals to work on with the plane's envelope this summer.  One is to run a tank dry, or nearly dry.  At landing, if my gauges show zero on one tank or the other, there is still somewhere around 6-10 gallons in the tank.  Normally we land nowhere near dry in either tank, even for a long trip, but I would like to know how far my plane really will go on full fuel.  I have done some testing on the fuel flow meter with the JPI, and it is very accurate, much more so than the tanks.  I know within a tenth of a gallon what I have used.  Just need the right circumstances, I don't want to try this at FL240.  If I blow it and the engine stops, so does the turbo, and it will be quite awhile and several thousand feet before the engine will want to start again.

The other is to try LOP.  I flew some LOP last year, and have taken the Advanced Pilot Seminar, but the plane really did not like LOP, just ran rough.  I had it tweaked some at annual, so am anxious to try that again.  Wouldn't it be great if I could cruise at FL240 and 225 GS, at 11 or so gph?

Only a couple of other notes on the trip.  I filed for FL240 leaving BIS to FCM and they wanted me at an odd altitude.  The controller offered me FL210 and 230 and I took 210, but he questioned that altitude.  His exact statement was, "We don't see many Mooneys at that altitude."  So I don't know, maybe we need to organized a turbo Mooney group and buzz Salt Lake Center's facility at FL240 so they understand turbo Mooneys better. 

The other was the departure from KGPI.  For those who don't know the place, there are Rockies on both sides, and the ridge on the east is around 10,000.  Normally, we have plenty of time to climb over it, but this time my friendly winds aloft were pushing us pretty good.  I had to go Vx at 9,000 and at that, had to fly through a "notch" in the crest ridge.  Made for a pretty view though.  Copilot noted the "TERRAIN ADVISORY" on the GPS.  At least  now she knows what that is for.  She got some spectacular pictures.

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• Parker_Woodruff

Do you have GAMIs?  Don Maxwell said my soon-to-be 252 doesn't wanna run LOP at 65% power.  No GAMIs on it, but that will be my first upgrade.

I have the same configuration, the wastegate and the Turboplus intercooler and have been wondering how people operate these.  I have had the plane for 3 months now and haven't had much time to experiment.  Do you ever look at the guage for the intercooler or do you just use some know configuration (ie: 38inches for takeoff, 28 in cruise). I usually see a 40 difference gauge at takeoff which works out to a little under 38 if you follow the formula.  Any information would be appreciated.

FAST FLIGHT OPTIONS LLC

I have gotten my 231 up to FL 180.  At about 28" and 2500 RPM I was buring 10 GPH @ about 50 degrees LoP T.I.T.  It was warm out so I had the cowl flaps in trail. I dont have a wastegate or intercooler by the way and run with stock injectors.  I would think a 252 would do even better not sure why you could not run LoP?

I have GAMI's.  Your (almost your's) 252's induction system is balanced better than the 231's.  One of the issues with my aircraft I think, is that the MP, fuel flow, and consequent %HP and airspeed are constantly moving around according to my JPI.  Not much, but the tolerance is smaller on the lean side than on the ROP side.  ROP, I follow the APS recommendation of somewhere between -100 and -125 degrees, so I have a pretty good cushion if the engine settings move around.  On the lean side I would be setting for 60 LOP (APS recommendation), and it is not nearly as far back to the "red box" from there.  Also, the throttle linkage is maybe telling me something.  It takes quite a bit of throttle movement to go from "LEANEST" to -125 ROP.  It takes not much throttle movement to go from "LAST TO LEAN" to -60 LOP on the lean side. 

With the tweaks at annual, I am going to experiment with LOP again. But I learned the hard way with the "high altitude miss" to experiment when I am alone in the plane.  The copilot got pretty excited when the engine started bucking and spitting and thinking about quitting at FL230.

One comment I would make on the 252 (and I have to add I have never flown one), is that I would question the value of taking it to its service ceiling of 28,000.  Maybe it is set up way better than the 231.  But the effects of lack of cooling because of the thinness of the air become rapidly apparent at about FL210, and when you hit critical altitude and the climb rate starts to drop, getting up higher just happens at a crawl.  If you have a long way to go and a great wind at the higher altitude, it may be worth it.  But I think you would have to be looking at a trip of at least three hours, or you would have to start down as soon as you hit FL280.  That said, if I owned the plane, we would be up there giving it a try.

One thing to bear in mind, if you have not flown a nonpressurized aircraft in the flight levels, is that you need to start down alot sooner than you are used to with a normally aspirated aircraft.  If you are cruising along at FL240 at a GS of 240 thanks to a tailwind, you will have quite a bit less than 30 minutes to get down to landing altitude from 90 miles out.  If you just tip the nose over and throttle back a little to maintain MP at your cruise setting, you will be coming in even faster at, say, 260.  You will slow some in the lower altitudes, but you will still make your airport really fast. Unpressurized, you need to descend at about 500 fpm, and not more than 700 for the sake of passengers ears.   Thirty minutes at 500 fpm only gets you 15,000.  So you need to give the whole descent process some thought ahead of time.  This is when the approach controller picks you up and refers to you as "Mooney jet," assumes you are pressurized, and wants you to dump altitude at 2-3,000 fpm.  The plane can do it.  Your passengers' ears may not be so happy. 

FBCK asked if I look at the gauge for the intercooler.  When I first got the plane I had the "differential temp" gauge, but I installed a JPI 930 and took the "diff. temp" gauge out.  I have readings for Compressor Discharge Temperature and Induction Air Temperature on the JPI, and the difference between the two is what would read out on the diff. temp gauge.  I could do the mental math.  But the JPI has an algorithm that produces %HP, and I generally just use that.  It is pretty close to the result I get if I do all the mental math and look at the Turboplus chart.

On the standard 231 without the intercooler, I would warn you that the CDT goes redline at WOT ( and you should be at WOT, meaning whatever setting gives you 100% HP)above about FL210.  It is not important in the intercooled aircraft, because the purpose of the original redline was to protect the engine from high induction air temps and the intercooler drops those temps quite a bit.  I was seeing a differential temp of around 135 F, or about 75 C, on this last trip at FL240.  You should not allow the CDT to go over redline in the nonintercooled 231.

PS on "standard configurations" for the intercooled 231, I just use one and that is on takeoff.  I generally use just a little over 36", say 36.3-36.5.  The JPI generally says I am over 100% HP if the MP is higher than that, and I find that 36 is really all I need anyway.  One footnote is that when I first got my plane the intercooler was old and dusty.  I was not getting much cooling from it, so I had it cleaned at annual two years ago by Willmar.  Turboplus can also do it.  Made quite a difference. 

Quote : jlunseth  It takes quite a bit of throttle movement to go from "LEANEST" to -125 ROP.  It takes not much throttle movement to go from "LAST TO LEAN" to -60 LOP on the lean side. 

Jlunseth...thanks for high altiude pirep....Parkers concern about flight above 23k a real concern...period of useful conscioness rapidly degrades after 23k in average adults.You are quite correct about cooling at 25k,the highest I have flown...temp control to about 380,i achieve with cowl flaps.(2900/2400)TIT 1600.....214 tas.Where they can be closed in cruise @ 19k,I have to somtimes open them up again.The Bravo I fly isnt equipped with inlet or outlet air temp guages so it just tit and cvl hd temps to watch.The thing you did not touch on but in my opinion is most important is condition of pilot and passengers...I check for mask fit,use a pulse oxyimeter and make sure everyone is in good health with no breathing issues.I also try to err on side of too much o2 when setting flowrate.Descents are made at 20in ,airbrakes out,800/900 ft per min.I teach all passengers the valsalva manuver (scuba divers clear)and remind atc when its time to start down(I program a vnav descent profile on the 530)...most of the time they have me cleared for lower before I have asked.Lastly,you have probably noticed how empty the high teens to middle twenties are...they belong to us turbo guys...the kerosene burners are 10k higher and the nonturbo traffic  10klower...all and all a greatride above the weather with a smooth ride...regards kp couch

Quote : Parker_Woodruff

Sorry guys, I didn't post this or the following message, but I can't delete them so I'll just edit in apologies.

Sorry guys, I didn't post this or the preceding message, but I can't delete them so I'll just edit in apologies.

Some years ago, when I had my Trophy 261 Conversion, my 231 became in effect a 252 with a 12 volt electrical system, and the POH was that of the factory 252.  I'm sure that some forum members know of other differences, but during the 16 or 17 years I owned her, I flew her in accordence to the 252 POH.  I found that the critical altitude was just about 24,000',(Flight Level 240), and I made many cross country flights (West to East) between 23,000 and 27,000' (with a one time ATC approved) 29.000' run of about 500 miles. There were two reason for going so high.  One, to get above (most of the) weather, and two, for the fastest ground speed possible.  I had 115 gallons usable (why I ended up with more than the standard Monroy conversion is beyond me, but we tested it several times), and so once I was up there, I seldom flew lower until my destination. This is a hostile environment, and I used good quality (read expensive) masks with built in microphones, flow meters, and a hooked up second oxygen tank with its own duplicate masks.  Handling gets, in my opinion, marginal at 27,000', let alone 29.000'.  I always added Prist to the fuel, and changed to the "pressurized" magnetos. During the winter months, I could just about reach the lower edges of the jet stream, and this gave incredible ground speeds - 315 knots confirmed by ATC on one crazy run.  Truly a tiger by its tail.  So far as let downs to destination, I would plead with ATC to let me start down 125 miles from my destination, but mostly they held me until about 75 miles to go.  Of course coming back, I seldom flew above 14,000' or 16,000' because of the winds.  For what it is worth, at the high altitudes I flew WOT, and ROP of about 125 degrees.  CHTs were under 390 degrees, but I had to watch TIT closely, and there were times when I had to reduce throttle, and even open the cowl flaps a bit. Nowadays I fly a 201, and generally stay below 14,000' .  I'm not so much in a hurry now, and I like flying without oxygen. Sure I will use a cannula at 12,000' or above in daylight, and about 8,000' and above at night on a long trip, but flying is more fun (for me) now, and a naturally aspirated 201 is quick enough for my current purposes.

Quote : Parker_Woodruff  Don Maxwell said my soon-to-be 252 doesn't wanna run LOP at 65% power.  No GAMIs on it, but that w ill be my first upgrade.

donshapansky

Hey Parker, glad to hear you're about to get a 252! I agree with your personal limit, anyone above Fl230 better be a jet jock with high altitude chamber experience because it's 2 minutes to lights out at FL250! A couple of flights back I climbed to FL200 from FL180 at 1000'/min LOP was 15.5 gph smooth at 214 KTAS, ground speed was up there at 265 KTS in light snow.

• 4 weeks later...

Quote : jlunseth I have been on a mission to figure out how to operate my 231 in all the parts of its envelope.  The certified ceiling is 24,000.  We tried FL230 last year and had some excitement with "high altitude miss" where improper pressurization of the magneto leads to arcing across the cap in the thin air in the flight levels.  Got that fixed at annual over the winter, but just have not had the right circumstances to go that high again.  This weekend my copilot and I went to Kalispell from Flying Cloud in Minneapolis.  We had the usual share of adventures.  The vacuum pump pooped out on the first leg of our trip to KGPI, fortunately in VMC.  I made the mistake of leaving the plane on autopilot for a little bit while we decided what to do and then told ATC we needed to divert to KBIS (Bismarck).  As the AI wound down, the plane started bucking and gained a little altitude, which concerned ATC (because they knew our circumstances by then), but I disconnected the AP and made an uneventful landing.  Lots of flooding at Bismarck and throughout ND.  Bismarck Aero found a mechanic and the pump was changed in short order, but it was too late to continue so we stayed the night in the FBO at BIS.  For future information, they have a sleeping room with two single beds, worked out really well.  The trip out was at FL220, the winds aloft were not too bad, but another 2,000 feet to the service ceiling and they were screaming and in the wrong direction, so we did not have a chance to try FL240. On the way back we got our chance.  ATC gave us FL240 for the leg from KGPI to our refueling stop at BIS.  As those of you know who have been on this site for awhile, my 231 has the Merlyn wastegate and Turboplus intercooler.  The Merlyn increases the critical altitude (the altitude at which the aircraft can no longer generate 100% HP), but I had never tested out where this happened with the Merlyn.  The critical altitude on the 231 as it came from the factory with the fixed wastegate was 15,000 +/- 500.  We found it at 22,500 with the Merlyn, using the numbers generated by the JPI's %HP algorithm.  It was quite a bit warmer than a standard day, -24C at FL240 which is around 10 deg. warm, so I suspect we would get better on a standard day or a cold winter one.  It was not until the last 1,000 that the climb rate reduced from my standard 500 fpm cruise climb.  We hit about 300 fpm from 23,000 to 24,000. At altitude the plane quickly accelerated to about 182 TAS before I pulled it back to cruise.  We cruised at 27.4 MP and 13.7 gph.  The 13.7 seems to be the magic figure for my aircraft in a cruise range of 75-80%.  I am at the point where it does not seem worth it to go through the lean procedure with the JPI, I just pull it back to 13.7 and all the cylinder temps fall in line in the 370' and 380's at altitude.  Bear in mind that in the high thin air, cooling is not as good as lower down, so those are good working temps. We made the trip from KGPI to KBIS in a flight time of 3:00.  We hit a ground speed at one point at cruise of 234 knots.  My copilot got a picture of a 233 or maybe the 234 that I will post when I get it.  Not too shabby for a fuel mileage of close to 20 mpg.  I have a couple of goals to work on with the plane's envelope this summer.  One is to run a tank dry, or nearly dry.  At landing, if my gauges show zero on one tank or the other, there is still somewhere around 6-10 gallons in the tank.  Normally we land nowhere near dry in either tank, even for a long trip, but I would like to know how far my plane really will go on full fuel.  I have done some testing on the fuel flow meter with the JPI, and it is very accurate, much more so than the tanks.  I know within a tenth of a gallon what I have used.  Just need the right circumstances, I don't want to try this at FL240.  If I blow it and the engine stops, so does the turbo, and it will be quite awhile and several thousand feet before the engine will want to start again. The other is to try LOP.  I flew some LOP last year, and have taken the Advanced Pilot Seminar, but the plane really did not like LOP, just ran rough.  I had it tweaked some at annual, so am anxious to try that again.  Wouldn't it be great if I could cruise at FL240 and 225 GS, at 11 or so gph? Only a couple of other notes on the trip.  I filed for FL240 leaving BIS to FCM and they wanted me at an odd altitude.  The controller offered me FL210 and 230 and I took 210, but he questioned that altitude.  His exact statement was, "We don't see many Mooneys at that altitude."  So I don't know, maybe we need to organized a turbo Mooney group and buzz Salt Lake Center's facility at FL240 so they understand turbo Mooneys better.  The other was the departure from KGPI.  For those who don't know the place, there are Rockies on both sides, and the ridge on the east is around 10,000.  Normally, we have plenty of time to climb over it, but this time my friendly winds aloft were pushing us pretty good.  I had to go Vx at 9,000 and at that, had to fly through a "notch" in the crest ridge.  Made for a pretty view though.  Copilot noted the "TERRAIN ADVISORY" on the GPS.  At least  now she knows what that is for.  She got some spectacular pictures.

Thanks for the post dmevans!  I never really thought of that angle and I guess I don't have to with a non-turbo bird...but seems valid enough!

dmevans...thanks for the controllers pov.I see you state your location as Hayward so I assume you work oakland center or one of the norcals and you might have even worked me .I frequently file for high teens low twenties and my climb is typically 500 ft per min in a cruise climb to altitude.These altitudes are chosen (as you are no doubt aware)to climb on top of weather or for terrain avoidance/smooth ride.I have noted that I am always cleared as filed at these altitudes but your mention of transitioning of turbine a/c from enroute to terminal through them is interesting.I assume you could always turn a merging target left or right if you ended up with a conflict??Anyway sorry if us little guys increase your workload but us with turbocharged equipment run best at these altitudes and as another controller pointed out to me ,no body but turbocharged piston aircraft are using...thanks for the input..kp couch

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This Day in Aviation

Important dates in aviation history, tag archives: mooney 231, 7 january 1980.

7 January 1980: In response to a challenge, Alan W. Gerharter, Chief Flight Instructor of Logan and Reavis Air, Inc., Medford, Oregon, flew a four-place, single-engine Mooney M20K, N231LR, serial number 25-0025, from San Francisco International Airport (SFO) to Washington National Airport (DCA) in 8 hours, 4 minutes, 25 seconds.

This qualified as a new Fédération Aéronautique Internationale (FAI) and U.S. National Speed Record of 486.20 kilometers per hour (302.11 miles per hour).¹

Gerharter had beaten the previous record held by a Malvern Gross, Jr., ² flying a Cessna T210, N5119V, by 3 hours, 3 minutes, 23 seconds. When Gerharter arrived at DCA, Gross was there to meet him.

Gerharter had made temporary modifications to the Mooney for this flight. He had two 25 gallon (94.6 liter) fuel tanks mounted in place of the rear seats, bringing the airplane’s total fuel capacity to 122 gallons (462 liters). The right front seat was removed and two oxygen tanks installed. In an effort to reduce aerodynamic drag, he removed the boarding step at the trailing edge of the right wing.

The Mooney M20K was marketed as the Mooney 231, a reference to its top speed of 201 knots at 16,000 feet (4,877 meters), or 231.3 miles per hour (372.25 kilometers per hour). The M20K has a Maximum Structural Cruising Speed (V NO ) of 200 miles per hour (321.9 kilometers per hour), and a Never Exceed Speed (V NE ) of 225 miles per hour (362.1 kilometers per hour). The airplane has a maximum operating altitude of 24,000 feet (7,315 meters).

The M20K was certified in 1979, 24 years after the original M20 entered production, and it was produced until 1998. The M20 series continued in production with follow-on models until 2008.

Mooney M20K N231LR was issued an Airworthiness Certificate on 27 December 1978. It is currently registered to a private party in West Sacramento, California.

¹ FAI Record File Number 13854: Speed Over a Recognised Course, 486.20 kilometers per hour (302.11 miles per hour), 7 January 1980. Current Record.

² FAI Record File Number 965: Speed Over a Recognised Course, 352.36 kilometers per hour (218.95 miles per hour). FAI Record File Number 966: Speed Over a Recognised Course, 384.03 kilometers per hour (238.63 miles per hour). Both records were set 1 January 1977.

© 2023, Bryan R. Swopes

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Mooney Acclaim Type S: Still The Fastest!

If speed is your thing, The Acclaim Type S may be at the peak of the production pyramid

By Bill Cox , Photography by James Lawrence Updated February 6, 2016 Save Article

The outside air temperature is about minus-30 degrees C, and the air is so thin at this height, we mere mortals would be tempting fate without our masks. If we were scaling K2 or Everest, we’d be only 1,000 feet below what climbers call the death zone. Technically, atmospheric pressure at FL250 is only about a third of that at sea level, and humans don’t do well at such heights without supplemental O 2 .

The new, production Acclaim Type S that has us surrounded doesn’t seem to mind the conditions. The airplane’s big Continental TSIO-550G engine features twin turbos and dual intercoolers; it thrums happily in the cold, high sky.

Loaded up with full standard fuel and two big pilots up front, the airplane is nearly at gross weight as it gradually sneaks up on its max cruise number. I watch the true airspeed readout on the Garmin G1000, and the numbers slowly count up to 239 knots. That’s 275 mph in nonpilot speak, about four times legal freeway speeds and faster even than a Bugatti Veyron. Normally, 239 knots is the beginning of turbine country, recorded by C90 King Airs and the like, but the fastest of the Mooneys takes truly high cruise in stride.

Speed has always been Mooney’s strongest suit. The type has consistently manifested among the highest knot count per hp in general aviation. In today’s world of $6-per-gallon avgas, the airplane’s ability to wring every possible knot out of each gallon serves it well. The gold standard of performance was previously one mph per hp, and a Mooney is one of very few production airplanes to realize that goal (achieved 30 years ago on the 201, flying 200 mph on 200 hp). Better still, the turbocharged Mooney 231 came close to realizing one knot per horsepower in 1979, delivering more than 200 knots on only 210 hp.

Alas, the days of the 200 hp Mooneys are long gone, though some of Mooney’s old guard still regard the 201 as the best Mooney ever built. Today’s Mooneys fly behind engines with far more power, but because drag increases at the square of speed, what was possible with 200 hp is highly unlikely with 280 hp. The current state of the aerodynamic art isn’t up to 280 mph on 280 hp.

Still, by any standard, the new Mooney consistently achieves more with less. The Acclaim Type S is the second iteration of the Acclaim, and it’s arguably the fastest production, piston single in its class, period. Even if you’re not inclined to file for the flight levels on every flight, you can see impressive numbers at lower levels. At 15,500 feet, plan on 220 knots, and down at 10,000 feet, the Acclaim Type S should still trip along at 205 knots or more.

Mooneys weren’t automatically born to such speed. The Texas company’s original Acclaim was a notably quick airplane, but Columbia Aircraft used to claim that its Columbia 400 was a knot or two quicker. Accordingly, Mooney launched into a speedup campaign to raise the ante and reassert its claim as fastest airplane. Cessna (which purchased the Columbia 350/400 assets and type certificates when Columbia went bankrupt last year) no longer fuels the competition. Cessna now claims the 400 as simply the fastest, fixed-gear, production piston single, with a top speed of 235 knots. Mooney suggests a top speed of 242 knots, and no one disputes the claim.

Top speeds are pretty worthless numbers, as hardly anyone is dumb enough to flog an engine at continuous max power unless they’re turning the pylons, even if the engine is rated for it (as is the Mooney’s). The Acclaim Type S spec is 237 knots at 75%, and I’ll take 239 as a close approximation of that any day.

Such brevity isn’t possible without plenty of horses out front. The Acclaim Type S features a Continental TSIO-550-G, considerably derated on the fastest Mooney, but pushed to as much as 350 hp in other applications. Mooney claims the engine is turbonormalized, which might suggest a manifold pressure red-line of 30 inches. Instead, twin Kelly Aerospace blowers provide the big Continental with a limit of 33.5 inches all the way to the critical altitude of 25,000 feet.

However you choose to define “turbonormalized,” power is copious and may be limited only by the size of the airplane’s vertical stabilizer. A former president of Mooney suggested that it was unlikely the airplane’s comparatively small tail could accept a 310 hp engine, like the one mounted on the Cessna 400 or Cirrus SR22-G3. (Obviously, any major aerodynamic change, such as a larger vertical stabilizer, would require a completely new—and very expensive—flight-test regimen for certification.)

Of course, pure power installed in any airplane is rarely an end in itself unless the airplane is named Rare Bear. [For more about Rare Bear and the Reno Air Races, read “Days Of Thunder” in Pilot Journal March/April 2008.] Power can introduce all kinds of expensive problems—higher fuel burn, a more forward CG, reduced range, lower payload—and doesn’t come close to generating a proportional, offsetting benefit. (The formula suggests that the speedup is roughly equivalent to the cube root of the power increase.) Given enough power, you could probably blast the Queen Mary into orbit, but power has never been Mooney’s overriding philosophy.

The most efficient answer may be a combination of power and improved aerodynamics, and Mooneys have always offered more than their share of slick designs, a tough task with a predominately all-metal airplane that’s, by definition, more difficult to mold and shape than composites.

His eldest son, Curt, along with mom Peggy and brothers David and Jim have been working on Piper/Cessna/Beech/ Cirrus/Grumman American products, along with older Mooneys, for the last 20 years, and Curt was happy to apply his considerable aerodynamic skills to the new, ultimate Mooney.

“All the Mooneys are very clean designs, so there’s not a lot left to improve,” says LoPresti. “We analyzed the airplane’s drag profile and did find a few areas where we could clean up the airplane. Our calculations suggested the changes would generate about five knots more speed, and that’s about what they got.

“We discovered the most significant areas of excess drag were the nosegear and main landing-gear doors. The stock nosegear door had a bulge that was causing air to separate, creating burble,” LoPresti explains. “Mooney faired that in, creating a smoother passage for the air. The main gear doors also were a little too fat where the gear trunnion extends. Mooney also solved that problem.

“Additionally, we recommended installing a flap gap seal to keep air from leaking through the slot between the flap leading edge and wing trailing edge,” LoPresti continued. “Our final recommendation was that they remove their current flap hinge fairings, as they were causing more drag than they were curing.”

Before you can log the big numbers in cruise, you have to reach the flight levels, and the Acclaim Type S does that with dispatch. Flying from near-sea-level at Plant City, Fla., a few miles west of Lakeland, we lifted off and started the stopwatch on our climb to the flight levels.

I held a modified cruise climb of 110 knots pointed uphill, rather than Vy, in the interest of better engine cooling and improved over-the-nose visibility. ATC was willing on the day of our flight, and we were able to high jump all the way to FL250 without any level-off at interim altitudes. When I clicked the button at the top, time was 25 minutes and nine seconds, almost exactly 1,000 fpm. The rate varied from about 1,200 fpm initially to 900 fpm when I pushed over at 25,000 feet.

With such climb on tap, many Bravo and Acclaim pilots tend to fly high much of the time, especially eastbound, where the prevailing winds usually give you a push. Flying in the opposite direction, you can always opt to stay low where winds are lightest.

Opt for the 128-gallon tanks, and that translates to 8.5 hours of endurance and 1,700 nm of range, provided, of course, that you’re willing to sit in the seat for a full work day. Even I’m not that masochistic, but the message is clear: Any reasonable mission you can conceive, the Acclaim Type S can probably fly. Perhaps even better, if the cabin load will allow, you can buy the long-range tanks, fill them with the cheapest fuel you can find and fly an out-and-back without having to refuel.

If comfort is better than you expect, avionics sophistication is also equal to anything in the class. Mooney has embraced the Garmin G1000 dual flat-screen avionics suite, along with the Garmin G700 autopilot. The level of avionics sophistication is only slightly below that of a Gulfstream, and the Mach number is just under 0.40.

Make no mistake, no matter what its other talents, the Mooney Acclaim Type S is all about speed. It makes no compromise with comfort, yet flies behind less horsepower and still manages to go faster than anything else in its class. It’s designed for the pilot for whom nothing but the fastest will do. Roy LoPresti would be proud.

SPECS: Mooney M20TN Acclaim Type S

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Two Turbo Retrofits

Turbonormalizers for mooneys and bonanzas are well-engineered and deliver both higher speed and fuel economy..

The pilots sacred trinity: Higher, faster, farther. Not to be vulgar, but to that precious list, its our duty to add one more item: More money. Lots of it. In single-engine airplanes, think of the money-to-speed ratio as a predictably gentle curve out to about 160 knots. Beyond that, it rockets upward steeply such that every additional knot costs at least a grand or two. (The general rule of thumb that speed mods deliver 1 knot per $1000 spent is remarkably reliable.) While speed mods trickle on added knots by nibbling away at drag, the big gains come from turbocharging, which allows an engine to deliver rated power up into the thin air, where true airspeeds inch upward. Every major manufacturer has offered turbocharged models of some sort, occasionally across most of the product line. In parallel, aftermarketers have offered retrofit turbo systems to a handful of engines, a business that seems to run according to its own unpredictable cycle. With the recent introduction of a new turbonormalizer for the popular Mooney M-20 series and the re-invigoration of the system formerly marketed by FliteCraft for Bonanzas and recently taken over by the group producing GAMIjector balanced fuel nozzles, the cycle is back on the upswing. The former FliteCraft system is now being pitched as the Whirlwind Bonanza under a new company name, Tornado Alley Turbo, Inc. Whats Normal? First, a clarification of terms: Turbocharging has traditionally been done in one of two ways: ground boosting or turbonormalizing, which is sometimes called altitude turbocharging. As the term implies, ground boost turbocharging is capable of driving manifold pressures above 30 inches of mercury at sea level, often to values well above 40 inches. Ground boost systems have generally remained the province of the engine and airframe manufacturers, since adding ground boosting after the fact opens up a tangle of certification issues related to an engines maximum certified power. Traditionally, most ground-boosted engines have been designed for that purpose from the outset, with low-compression pistons, more durable valves and guides, beefier crankshafts and additional lubrication for cooling. Turbonormalizing systems, on the other hand, limit boost to 30 inches or so, virtually the same value a normally aspirated engine can manage at sea level. But boost is regulated to maintain the engines MP at 29 to 30 inches all the way to a defined or critical altitude, above which power declines below 100 percent, just as in a normally aspirated engine. The beauty of turbonormalizing is that it can deliver high altitude and performance on about the same fuel as the equivalent non-turbocharged engine would burn. Thus the fuel specifics are better than the typical ground-boost system can claim. Further, with lower peak cylinder pressures and potentially lower temperatures, turbonormalized engines are theoretically less prone to high cylinder, valve and guide wear that plague some turbocharged engines. Loss of cooling efficiency at high altitude is still a concern, but intercoolers address that issue. (And so does aggressive leaning.) Engine and airframe makers have generally stuck to ground boost systems (although not universally) and some of these have earned good service histories. Still, others have driven their owners screaming into the night with high maintenance bills and downtime. An owner can reasonably expect slightly higher operating costs with turbocharged engines, but most are put off by top overhauls at 500 hours and a mid-run turbocharger overhaul. Does turbonormalizing avoid all that? No guarantees, but its logical that limiting boost exacts less wear and tear and heat-related stress on an engine, especially with intercooling, which both of these systems have. Whether that impacts reaching TBO is an open question. A Faster Mooney Mooneys popular M-20 line-the C, E, F and J-models, specifically-have a reputation for speed and efficiency. But the truth is, with cruise speeds in the 140 to 160-knot range, theyre more economical than blistering fast. Mooneys answer was to re-engine the M-20 long-body with a Continental TSIO-360-GB, yielding the 231, a ground-boost design with a fixed wastegate. At high altitude, the 231 was fast enough but it earned a checkered service history, leaving thousands of Lycoming-powered M-20s ripe for an aftermarket turbo system. When Bill Sandman, a retired industrialist and principle in M-20 Turbos, set out to turbonorm alize his own 201 a couple of years ago, he initially intended it only for his own and his partners use. However, Sandman told us his project generated so much interest that he formed M-20 Turbos and pursued the STC, which was awarded last summer. The M-20 system, which sells for $23,389 for the kit plus another $2500 to $3500 for installation, is about as simple as turbocharging gets. It uses a Rayjay/Consolidated turbo with a fixed wastegate but no turbo controller. Boost is fixed at 30 inches, controlled entirely by a pressure relieve or pop-off valve on the outlet side of the turbocharger. (Lycoming developed a similar design for the Seminole and Comanche.) The designs chief advantage is simplicity; there are fewer parts to install and maintain and, especially, no turbo controller to fuss with. On the other hand, the system depends entirely on a single mechanical valve to regulate and prevent overboosting and at low altitude, the fixed wastegate can constipate exhaust flow, sapping performance. Heat is a problem, too, since the turbocharger is whirring away pumping up the manifold pressure and increasing the induction inlet temperature and, theoretically at least, reducing the engines detonation margins, especially if it has high-compression pistons, which the IO-360 does. The M-20 Turbo kit addresses this problem with intercooling, essentially a radiator that cools the turbochargers compressed air before its pumped into the induction system. Over the years, weve heard tall claims of dramatic power and speed increases attributed to aftermarket intercoolers but the undeniable best reason for having them is to reduce operating temperatures and prolong engine life. The Mooney M-20 Turbo kit is all-inclusive, providing the turbo and all related hardware, a new exhaust system, intercooler and induction airbox, plus new oil lines for the turbocharger plumbing. The fuel system retains the Bendix/RSA servo, but the kit includes an altitude-compensating fuel pump and injectors with upper deck air reference fittings. The 201 cowling is hardly expansive but the turbo and intercooler fit comfortably without introducing any maintenance access nightmares. The turbo is attached not to the engine but to the motor mounts, which should reduce vibration-related cracking in the mount hardware. Bruce Jaeger of Willmar Air Service, a respected Mooney shop, inspected and flew one of M-20 Turbos initial conversions and found only one beef: The stock exhaust system muffler is removed and with it goes the airplanes generous heat muff. The new muff delivers insufficient warm air, making for a chilly cabin. Sandman told us hes aware of the problem and is working on fixes, which might include a supplemental electric heater of some sort. The M-20 Turbo mod subjects the cowling to major surgery: To improve cooling-what Sandman calls after cooling-the lower cowling gets a fixed center cowl flap and cheek louvers to improve air flow. The left cowl flap is also trimmed in length for the same reason. Last, for intercooler inlet air, a new opening is cut on the left side of the cowling, opposite the landing light. The stock ram air door goes away and the control cable is converted to set an adjustable oil cooler shutter. If you own a pre-201 Mooney, by the way, youll have to convert to a 201-style cowling, which will add significantly to the bottom line. Cool in the Climb All that attention to cooling evidently paid off, at least in the climb. For takeoff and climb through the low altitudes, the turbonormalized M-20 behaves like the stock airplane. On a warmish Florida day during peak performance, low speed climbs, we noted that the CHTs remained in the 350- to 380-degree range, noticeably warmer than our stock 201 but hardly cause for concern. Above 3000 feet, where the full-power MP would normally have started its decline, the turbonormalized engine continues to deliver full power so the speed increases and climb rate remains at a brisk 700 to 1000 FPM. We leveled at various altitudes and let the airplane gather itself to cruise speed. At 12,500 feet, we recorded 170 knots TAS at 11.5 gallons per hour, leaned to 100 degrees F rich-of-peak, as per Lycoming best power recommendations. (Not that we necessarily agree with that.) Continuing the climb, we leveled at 16,500 feet and noted a TAS of 177 knots, also at 11.5 gallons with the same leaning. Ron Saeger, a North Dakota J-model owner who bought one of M-20 Turbos first conversions, told us he has seen airspeeds of 186 knots at 10.1 gallons at 21,000 feet; an impressive number if youre willing to suck oxygen to go that fast. How Lean? Sandman says M-20 Turbo recommendsLycomings best economy leaning advice, which is 25 degrees rich of peak. We experimented only briefly with lean-of-peak TIT operation and this engine seems to do it without complaint. Saeger told us he found that the engine operated smoothly as lean as 30 degrees lean of peak TIT. Frankly, we think with some tweaking of the fuel/air ratios, this engine can and should be operated in that regime. That would solve one minor problem we noted: In the thinner air at 16,500 feet, we noted the number 3 CHT at just over 400 degrees F. Although Lycoming sets the redline at 475 degrees (500 degrees on some engines), anything over 400 degrees is cause for concern, in our view, based on General Aviation Modifications research that shows cylinder out of roundness and piston scuffing occurs at CHTs above 400 degrees, especially if the cylinder is unevenly cooled. We would like to see it 20 degrees cooler, at least. The most expedient way of doing this is lean-of-peak operation, as Tornado Alley recommends for its Whirlwind Bonanza conversion. Failing that, perhaps some work on the baffling might suffice. As it is now, 185-plus knots on 10 gallons per hour puts this conversion into a league of its own as far as raw efficiency. The Mooney 231 will do that kind of speed but on two to three gallons more fuel and at the expense of poorer climb and low-altitude performance. In the low oxygen altitudes, say 16,500 feet, the M-20 conversions additional speed extends the stock airplanes range by a solid 10 percent at 65 percent power; more if youre willing to throttle back. The M-20 Turbo system adds 23 pounds to the stock Mooney airframe, a modest hit in our view. Theres little or no impact on center of gravity. The system has a pass-through warranty based on coverage provided by the manufacturers of each individual component. Tornado Alley Extended range and efficiency-plus speed, of course-is undeniably the selling point of Tornado Alleys Whirlwind Bonanza. A little history here: This is the very same Bonanza conversion formerly marketed by FliteCraft of Pagosa Springs, Colorado, a company well respected for solid engineering and good customer service. Last year, General Aviation Modifications, Inc. (of GAMIjector fame) formed Tornado Alley Turbo and bought the FliteCraft STCs. Theyre now marketing the system as the Tornado Alley Whirlwind Bonanza, a twist of marketing hype that actually has a discernible philosophy. Tornado Alleys George Braly told us that turbocharging in general and specifically the sort of aftermarket systems sold by FliteCraft and others have traditionally been pitched toward pilots flying in mountainous areas. Braly says the Whirlwind package certainly applies to mountain flying but its also aimed as a speed enhancer for flat land pilots lusting for 180-knot or higher speeds, with the added attraction of not having to climb into the oxygen altitudes to go that fast. Heres the idea: In a TCM IO-520 equipped Bonanza, a Tornado Alley turbonormalizer delivers 30 inches of manifold pressure to its critical altitude of 20,000 feet. For a Bonanza that means it will true in the mid-180s on just less than 15 gallons per hour, if leaned aggressively. Thats about 14 to 16 knots faster than the normally aspirated version will fly at its best altitude, normally between 7000 and 8000 feet. Since the fuel flows are the same, the turbonormalizing effectively extends the Bonanzas range by 10 to as much as 20 percent. Climbing into the high teens and low 20s will yield yet higher airspeeds, again at the same fuel flows. Weve flown the GAMI/TAT turbonormalized IO-550 Bonanza on several occasions and noted true airspeeds just shy of 200-knots at 20,000, aggressively leaned and burning 13 to 14 gallons per hour. At higher altitudes and fuel flows, it will true in the 210-knot range. Aggressive leaning, according to Braly and company translates to lean-of-peak TIT operation at any power settings up to 75 percent. To achieve that, Tornado Alley equips all of its conversions with turboGAMIjectors, improved fuel injection nozzles that balance the poor fuel/air ratios in most TCM engines. The TAT System Tornado Alley bought the FliteCraft system lock, stock and turbo controller and other than some tweaking of the upper deck cooling and the turboGAMIjectors, the system remains unchanged. Cost: $34,500 installed, plus minor additional charges for air conditioned models and relocation of components on some airframes. (For now, installations are done only at TATs Ada, Oklahoma shop.) The Tornado Alley conversion applies to all IO-520/550 models found in Beechcraft 33, 35 and 36 series airframes. In addition, TAT took over the STC that FliteCraft developed for the Cessna 185. Although its a turbonormalizer, the Tornado Alley system is a bit different than the M-20 Turbo design. It has a Garrett turbocharger, an automatic variable waste gate and an absolute pressure controller. In addition to those components, the kit also includes a new exhaust system with greater wall thickness, a Teflon hose package, an altitude-compensating fuel pump and an intercooler which lives below the right side cylinder bank. Having been through several iterations, the TAT install is one of the most organized weve seen, with easy access to both the turbo and the intercooler and related hardware. Cosmetically, its nicely gussied up with enameled piping to and from the turbocharger and eye-catching silicon rubber baffling gaskets to replace the factory stuff, which becomes an eyesore after a few years of service. The TAT system adds 67 pounds to the airframe and although that reduces payload a bit, it all but eliminates the aft-tending CG problem that 33 and 35-series Bonanzas suffer. TATs warranty is a generous two years and 250 hours on the turbo components and four years/1000 hours on exhaust and induction air components. TAT says it will continue to support FliteCraft systems still in the field, of which there are some 250. What to Do? In our view, both of these conversions are well-engineered and well supported and we dont see any significant red flags against either, including M-20 Turbos anemic heater. Both appear to be as good as if not better than factory turbo set-ups. The Tornado Alley system was well-proven in the FliteCraft iteration and amassed a good service history and happy customers. If anything, TAT has improved it. The M-20 Turbo system is a relative newcomer with little service history in the field. Although Sandman reports that the company plans to continue improving it, he was also upfront with us about his future plans: The M-20 Turbo partners never intended to make a full-blown business of their project and will eventually sell the STC to another company. Sandman says he doesnt know when that sale will occur but we think a buyer ought to be aware of it. In lumping these two systems together, were not implying a side-by-side choice where none exists. If you have a Bonanza, the choice is Tornado Alley; if a Mooney, M-20 Turbo is it. If you have neither and want to buy a step-up airframe and then convert it, some careful shopping is in order. Lets talk money and whether you want any of it back after investing in a high-dollar mod. Figure on recovering half to two-thirds the cost of a major mod at resale. If youre in toys-for-boys mode, dont give this a second thought. Pay the money, fly high, be happy. Otherwise, shop some. Given the nature of the airframe and costs involved, we think the M-20 Turbos system is best applied to the J-model. If you own one, adding this conversion will cost about $27,000, bringing the total investment in a clean 201 to some $112,000, about 25 percent above market value for an unmodified airplane. Before springing for the conversion, its worth considering what else $112,000 will buy in high-flying turbocharged performance in a single. There are other picks: An early 1980s 231, Cessna T210 or turbo 182 are possibilities. These may seem out-of-class comparisons but if you dont care about seats, speed is speed. All airplanes have warts, of course: The 231 is a poor low-altitude performer and, compared to the turbonormalized 201, all the other picks are gas hogs. Further, our bet is that even a turbonormalized IO-360 will require less engine maintenance than the TSIO-520 in a Cessna 210. On fuel economy alone the M-20 conversion shines. Our view is add up the numbers and make your choice. The same considerations apply to the Tornado Alley conversion, although theres more price variability in the used Bonanza market due to the range of models and large numbers of airframes. Figuring a mid-$70,000 to $90,000 as an S- to V-35 starting place, youll still have $105,000 to $125,000 invested. The same shop-around advice applies, but expand the list to include an early A36TC, if you can tickle a little more money out of the bank. Buying an airplane already equipped with what you want-including a turbocharger-will usually yield the better deal valuewise and the airframe will doubtless continue to appreciate. The same cant be said of a high-dollar mod. But you have a nice V-tail or Mooney 201 that you plan to keep for awhile, these two mods will indeed make it go higher, faster and farther and at a fair buck. Also With This Article Click here to view the Turbo Retrofit Checklists . Click here to view the Turbo Performance Comparisons . Click here to view “Demon Detonation: Missing in Action.” Click here to view Turbo Retrofit Addresses . -by Paul Bertorelli

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