Beech Lightning
6 min read

The hallmark of a successful airplane builder is the ability to evolve its designs. Starting from scratch to create an all-new airplane must be a rare event. Real success comes through finding ways to stretch, enlarge and enhance airplanes already in production. And no company, at least in the personal and business aviation sector, has been better at that then Beech.

In 1947 Beech introduced the revolutionary Bonanza that is the foundation of a host of models including the A36 Bonanza and Baron 58 still in production today, more than 70 years later. Then came the Twin Bonanza in 1952. Despite the name, the Twin Bonanza borrowed little from the original other than the wing planform. But the “Twin Bone,” though not a huge success in its own right, was the foundation of the Queen Air, which with turboprop engines added in 1964, became the King Air, and the rest, as they say is history.

Given its string of success in evolutionary model design it was natural for people at Beech to continue to look for more ways to evolve their airplanes in new directions. In the early 1980s somebody, or perhaps a small group of people, realized they had the basis for a very good single-engine turboprop. That airplane was the pressurized Baron 58.

Beech Lightning

Add a turboprop engine to a Baron and you get the Lightning.

I don’t know how long it took, but probably months, not years, to remove the piston engines from the wings of a Baron 58P and install a single turboprop in the nose. The prototype was an elegant looking airplane with the classic lines of the Bonanza/Baron, and by all accounts, the same excellent flying qualities those airplanes have always been admired for. Beech named the new airplane the Lightning. I remember thinking at the time the name was a perfect match for the way the airplane looked, and the performance it promised.

The reason the Lightning looked so good, and came together so smoothly, was selection of the Garrett TPE331 turboprop engine. The 331 is a compact engine measuring just over three feet long. And it’s light. At under 400 pounds it weighs less than a big-bore Continental piston engine. The 331 also has the best fuel efficiency of the small turboprop engines, and its throttle response is quick, very much like a piston engine responds so pilots transitioning from piston to turboprop would need to adjust their flying techniques very little.

I hung around Beech and Cessna and the other manufacturers a lot in those days, and both Richard Collins and I heard good reports about the Lightning development. The prototype was flying frequently and performing well. There were said to be no “show stoppers.”

That was dead wrong. There was a show stopper. A big one. And it was in the nose of the Lightning. When word got around that Beech was using the Garrett engine, the Beech dealers went crazy. Not only no, but hell no. They wouldn’t sell an airplane with a Garrett engine, no matter how well it flew or attractive its capabilities.

As the firestorm from the dealers built, Beech management relented and sawed up the Lightning prototype to put a Pratt & Whitney PT6 turboprop engine in the nose. The graceful and elegant Lightning grew a schnoz that an army of plastic surgeons couldn’t fix. I don’t know how something grows a pot belly on its nose, but that’s what the PT6 powered Lightning looked like to me.

The problem is the PT6 engine draws intake air at the rear and exhausts its hot gases out the front of the engine. The Garrett 331 takes air in through a classic “smile” inlet in the front and exhausts out the rear.

With a Garrett in the nose, the Lightning nacelle was sleek and compact. And the propeller plane was right where you want it. When a cowling was created that could take air in the front and turn it 90 degrees to enter the rear of the PT6, the girth of the cowling grew enormously. And the much longer PT6 engine shoved the propeller plane far forward, which is very destabilizing to flying qualities and would have almost certainly required a larger horizontal tail, or other significant design changes.

Compared to the PT6, the Garrett 331 is lighter, more fuel efficient, and more durable with thousands of hours longer interval between overhauls.

Because the 331 is a fixed-shaft engine it has one major drawback compared to the PT6 and that’s starting. To start a 331, everything in the engine, including the propeller, must be rotated fast enough to move air through the engine when you lite the fire. That requires lots of battery power, or better yet, a ground power cart.

TPE 331

Garrett engines are light and fuel efficient, but have a reputation for being noisy.

To keep the propeller pitch flat during start, the Garrett requires “start locks,” a complexity the PT6 doesn’t require, And the compressor and turbine sections of the 331 rotate very fast, somewhere around 40,000 rpm, so the engine emits a banshee howl on the ramp that is loathed by line crew and other pilots everywhere.

In contrast, the PT6 is a free turbine engine, meaning there is no mechanical linkage between the gas generating section and the power section that rotates the propeller. To start a PT6, you need only rotate the gas generator section which takes comparatively little effort. You can even start a PT6 with the propeller feathered. The engine doesn’t care. Because everything is turning so much slower in a PT6, the noise level is far lower and not remotely as annoying as the Garrett engine.

But it wasn’t the starting challenges or ground noise level of the Garrett that put the Beech dealers into a rage. It was the history of turboprop market competition. For decades Beech people had been selling against the Turbo Commander, Mitsubishi MU2, Cessna 441 Conquest and the Swearingen Merlin, all Garrett powered. The King Air is a great airplane, the PT6 is a great engine, and, well, Garrett engines and the airplanes they power aren’t as popular. Beech sales people simply weren’t going to change their pitch for the Lightning.

Beech flew the PT6-powered Lightning some, but I didn’t hear much positive about the testing. When the extra weight, complexity and cost of switching to the PT6 were added up, the Lightning no longer made sense as a derivative of the P Baron so the project was shelved.

Would a Garrett-powered Lightning have succeeded in the market? I don’t know. It would have had a few years head start on the TBM, Pilatus PC12 and Piper Meridian that are so popular and successful in the market. And the PT6 reputation for being bullet proof still makes pilots feel comfortable flying behind that single engine.

The TBM, PC12 and Meridian prove that a nice looking and efficient cowling can be designed for a PT6 engine. And the PT6 is probably the most revered turbine engine ever, at least the most admired turboprop in terms of reliability and simplicity. But creating a PT6 cowling that looks and fits naturally on the nose of a Baron may not be possible, or at least not simple and easy.

So if you want to know what doomed the Lightning, it was the people who would have sold it. With a Garrett in the nose, they could no more do that than a Red Sox fan can say anything good about the Yankees. One thing is certain: airplane development programs seldom proceed in a straight line, and technical issues are only one consideration, and often not the first.

Mac McClellan
20 replies
  1. Vinton
    Vinton says:

    It’s great to hear your perspective on the demise of the lightning.. I spent my career in sales and it always amazed me how the strongest members of my team would sometimes fall into the trap of saying “That will never sell” before they allowed the end user customer to make Up his own mind. If they made 10 calls and then it didn’t sell, then I knew the developers had more work to do. I bet this would have been a heck of an airplane if it ever reached the market.

    SKYKON says:

    What an interesting perspective on the 331 vs. the PT-6. I’ve always “heard” the 331 on the flight line but never paid much attention to them. As a sales guy had always flown behind a PT-6 powered TBM 700 (SN 29) during my business career during the era that TBM became innovators in the single engine turboprop business.

    It’s just my sales instinct that had Beech hung in there with the Garrett designed Bonannza that it would have achieved success years ahead of theTBM in spite of the noise and starting issues – and probably at a price point that would have given TBM a real run for their money!

  3. Rows Detwilet
    Rows Detwilet says:

    Fascinating story.
    I was flying the basic Garrett core in the early 80’s (Falcon 10). There was a lot of “bad mouth” about the grenades at the time, especially since the chief corporate competition was using Rolls on their product. I wonder if that was part of the problem the dealers had.
    We flew those engines or their derivatives in the 10, 50 and later versions of the 900. In decades of flight and thousands of hours of flight time, we had one precautionary landing which turned out to be an indication problem.

  4. Dan
    Dan says:

    Most of my flying is with fan jets but I have flown a TPE331 on a Thrush spray plane about 1200 hours and love the engine. 20% less fuel burn than a PT6, 5000 hour TBO. Multiply those two and at 5000 hours you have enough savings to pay the overhaul. It is only noisy on the ramp about equal in the air. The noise on the ground has one benefit, you don’t have to listen to all the BS stories from “experts” on the TPE331.

  5. Phil D.
    Phil D. says:

    The airplanes noted for noise are the military fighters (that “A-B BOOM!”), the Rolls Royce Dart (“screamin’ mimi”), the UH-1 (“wop-wop-wop”) … and the Garrett TPE-331.

    Yup, noise gets the Garrett a “thumbs-down” as a “neighborly” G/A aircraft in “sleepy-town” USA.

  6. Jeff
    Jeff says:

    The TPE-331 is a great engine. They are flying every day all over the world 24 hours a day on the Air Force MQ-9 Reapers. The engines have had outstanding reliability and the aircraft routinely flies 20+ hour missions daily. They are a little louder at 100% RPM (1591 RPM) and the prop tips go supersonic. Keeping the speed lever back at 65% on the ground for start and taxi, they are reasonably quiet. Albeit not as quiet as the PT6.

  7. Terry Spath
    Terry Spath says:

    Of course Beech did end up using the Garrett in the B100 and even experimented with it on a 331 version of the F90. I saw it when I worked at Beech in 1983. I don’t believe it ever got into production.

    • Mac McClellan
      Mac McClellan says:

      The King Air B100 was powered by the TPE331. The only King Air with Garrett power. The primary reason was a worker’s strike, or at least the threat of a strike, at Pratt & Whitney Canada. Beech realized all it’s turboprop production was dependent on availability of the PT6 engine so management decided to at least try diversification.
      The B100 was not very popular with the traditional King Air owner, or the Beech dealers. But the airplane found an enduring place in the charter fleet because of the fuel efficiency and TBO advantages of the 331 engine.

  8. Duane Mader
    Duane Mader says:

    That was really interesting Mac!
    Maybe Raytheon should try again, the Lightning is beautiful and the work has mostly already been done. Given a choice I like the 331.
    Listen to a Commander or Conquest fly over, they are quiet. Also as I remember, the PT6 sometimes had to be at high idle in a King Air in order to run air conditioning or supplemental heat on the ground making it quite noisy too.

    • Kevn teller
      Kevn teller says:

      As a lineman when I wore a younger mans clothes the 331 sound on the ramp would actually make you nauseated if you got to close even if you were getting a low sound level because of a good tight headset.

  9. Juan D.
    Juan D. says:

    Very interesting article. I wonder why can’t Textron pull this project from the shelf and present it to the market.

  10. Hans Friedebach
    Hans Friedebach says:

    Interesting insight regarding development at Beech. I am disappointed that no one from the former product development / engineering /marketing side has picked up the pen to write about those events.
    I sold and flew the twin Turbomeca Astazou powered Beech Model 95 airframe built by Sud Aviation called “Marquis” in Europe. Amazing performance 55 years ago. A Garrett like scream on the ground assured you attention upon arrival. Three minutes from sea level to FL100 assured you attention on departure.
    Performance sold these airplanes. Except the hoped for US Military interest in this package did not materialize. King Air’s arrival in the market cut it’s life as a business airplane short.
    Maybe we can entice some old Beechcrafters at Tullahoma this fall to pick up the pen.


    JOHN SWALLOW says:

    I have just over 1300 hours behind a couple of 331s in a Commander 1000.

    Yes, they were noisy.

    Yes, they were hard to start if you let the oil go below 0 C.

    Bu were they ever nice for short field work, bad crosswinds, and on a contaminated runway.

    And they made fuel at altitude!


  12. James Nichols
    James Nichols says:

    I was in BE99 school in Wichita back in 1985 when someone from Beech Test Flight stuck his head in the door to talk with our instructor and one of us in the class asked him about the Lightning.

    At the time the rumor was Beech was having difficulties getting the stall speed down to single engine certification standards of 61 knots or is it 63 knots.

    The guy from Beech Test Flight said, “Right now it has stalled out at 1 million dollars.”

    It seems cost along with engine selection doomed the Lightning.

  13. ju teint
    ju teint says:

    Fantastic story! A36 pressurized with a G 331 would have been a blast! A tbm before time! Some times even a very good idea, perfect match, does not work commercialy! We have so many examples!
    Thanks for the article!

  14. Norman Earlw
    Norman Earlw says:

    Here is a similar aircraft that I built with a Walter 601 (very similar to PT-6) on a Baron airframe. Cowling problem solved. Not producing the BE38P Lightening was a colossal mistake by Linden Blue. The real reason was the company’s financial health during an aviation recession and Linden Blue’s poor choice to double down on the overweight and over budget Starship program.

  15. Tom Nash
    Tom Nash says:

    As the project aerodynamicist on the development team for the Beech PD336 / 38P Lightning, I beg to differ as to the cause of the project cancellation. I worked for Beech from 1977 to 1984. I was responsible for the aerodynamic analysis and verification of the 38P, from stability and control, to the predicted performance, to flight test analysis.

    What cancelled the project was the horizontal stabilizer. In those days, according to FAR Part 23, application of go-around power at final approach speed in a single-engine airplane in landing configuration. i.e, gear down and full flaps, had to result in a pilot control wheel force of no more than 50 pounds. Because the 38P was derived from the 58P Baron, a twin-engine aircraft that did not have to meet this single engine requirement, the horizontal stabilizer was not adequate to the task. The value I predicted for the 38P by analysis was 76 pounds of stick force. Lou Johansen, the project test pilot, measured 77 pounds. I later flew the airplane with Lou and verified this myself. The airplane wanted to do a spectacular back-flip on go-around. Of course in those days of aviation accident litigation, nobody at Beech wanted this known for fear that it would be brought into Beech Baron accident lawsuits.

    I designed a new horizontal stabilizer for the airplane, but in those days the good ole boys in the manufacturing department ran Beech, not the engineers. The cost of designing, manufacturing, structural and flutter testing, and stability and control testing an entire new tail was deemed to be too expensive an investment in an airplane that was facing a depressed economic market with low sales predictions. THAT is what killed the 38P. The whole TPE331 versus PT6 argument was (a) a smoke screen, and (b) the result of Pratt & Whitney throwing some wild parties for the 38P development team and convincing people that Beech really should be loyal to its main engine supplier. Pure politics supported by alcohol and BBQ. We had fun at P&W’s expense and re-designed the nose. No big deal. Then the Beech sales people whined because the TPE-331 jet-black exhaust stain would have been out of sight on the bottom of the airplane, and now the messy PT-6 exhaust stain would be right across the cabin entry door. Du-uh! Be careful what you ask for.

    I am retired now after a long and wonderful aviation career. The 38P was one of my first validations of my engineering education, and I will always have a soft spot for what might have been. I still have a copy of the November 1982 issue of Flying Magazine with the cover article: “Lightning Strikes! Beech Flies a Turbine Single,” an article written by a guy named J. Mac McClellan. Wanna buy it, Mac?

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