From Road to Sky: The Porsche FlugMotoren, Auto Engines that Fly

Engines from road-going vehicles often prove to be good for powering aircraft.  

Porsche PFM 3200

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The Porsche FlugMotoren (Porsche Aero Engines) was either sort of a disaster, or a total disaster, depending on who you ask.

At least they look cool. PFM in a Mooney M20L.

Derived from the road-going 911’s 3.0 liter flat six, you’d think the PFM would make the planes it flew in seem like P-51 Mustangs. Instead, it was the answer to a question that no one asked: can someone build a heavy, complicated, expensive, and unreliable engine for my light plane? Porsche's PFM 3200 was a six-cylinder horizontally-opposed air-cooled aircraft engine developed from their air-cooled line of automobile engines from the famous Porsche 911 sports car. The PFM designation was derived from the name of the division that designed the engines, Porsche-Flugmotoren (~ Porsche Flight Engines).

Air-cooled six-cylinder, horizontally-opposed piston engine

In the 1950s, European light aircraft builders began adapting the air-cooled automobile engines from Porsche and Volkswagen into aircraft engines with a series of limited modifications. Porsche cooperated with some of these builders and produced a series of factory-built engines for about six years between 1957 and 1963, the Porsche 678 series. These relatively small engines displaced about 1.6 litres (97 cubic inches) and produced between 55 and 70 horsepower, depending on the version.

Porsche decided to re-enter the aviation market with much larger engines derived from the Porsche 911, starting development in 1981.   As the engines ran at higher speed than most aircraft engine designs, the propeller drive used a 0.442:1 reduction gearing so it could drive common propellers. The high operating speed meant the engine ran more smoothly than older designs, and the use of a muffler meant it was quieter as well. With about 3.2 litres (195 cubic inches) displacement, the normally-aspirated N-series models produced about 210 hp, while the turbocharged T-series produced about 240 hp. This was roughly twice the horsepower of a conventional lower-rpm design of the same size. With single-lever operation, fully aerobatic fuel and oil supplies, direct fuel injection with automatic altitude compensation and optional turbocharging, the PFM 3200 series were some of the most advanced engines on the market.

After being introduced in late 1985 and starting to generate increasing interest in the general aviation (GA) market, Porsche exited the field during the massive downturn in the market in the late 1980s, closing the lines in 1991. It is suggested that the program cost them US$75 million to develop and produce the small number of engines delivered (about 80).  Although marketed for only a short period, the PFM was found on a variety of aircraft as the primary powerplant, or as one-off modifications. These included the Extra 330, Mooney M20L, Socata TB-16, Robin DR400, Ruschmeyer MF-85 and others. Only the M20L went into production, with 40 produced in 1988, and one more in 1989.

Porsche PFM 3200 aircraft engine in Technik Museum Speyer

 

Under United States law, where most of the engines were used, Porsche was required to continue to supply parts and maintenance for the engines. Instead, they claimed to have destroyed all spare parts and refuse to support the very engines they put into the marketplace. The company has even gone so far as to try and render the planes worthless by claiming the engines need certain parts replaced after a number of flight hours and then refusing to provide technical information so such parts could be privately manufactured.

 

So the PFM, ultimately, is the not-so-flugmotoren. It’s not really a good choice to put in anything, let alone an airplane. Surely there is some who would defend this engine.

[For more, see: Sequair.com, Wikipedia]

 

 

 

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