A Model A powered Pietenpol

Bernard Pietenpol was focused on the issue of affordable power for his affordable airplane. His early interest in the Ford Model T engine was prompted by the success of Ford in making motoring affordable and available to the general public, even rural farm communities. His success in this venture is undeniable. Powerplants designed and built for aircraft use were rare and very expensive; a problem for the average aviation enthusiast.

In his earliest efforts, the Model T could not be coaxed into producing enough power. A Gnome rotary was tried, but was also a disappointment. An "Ace" engine, a modified Ford, made the first breakthrough in Pietenpol's first monoplane design. Then with the availability of the Model A engine, his efforts came together to produce a powerplant that could do the job. He was able to overcome the weight handicap by keeping the airframe small and light and get the right combination to fly two people in a fashion equal to the commercial Swallow. One that flew in a manner described as being "between a Jenny and a Waco". The rest is history.

Bob Taylor's AAA Scout and Air Camper powered by Ford

It is interesting that he did not give up on the Model T engine. With the success of the Model A "two place" (its pre-Air Camper name), he returned to consider an even lighter single place version which the Model T could handle. He built and flew just such a plane, the Scout, and thereby proved a point that was important to him. The quest for affordable power was evidently always in the back of his mind. This was to emerge again years later when General Motors introduced the Corvair in 1960.

The Corvair powered Pietenpol

Pietenpol was fascinated by the aircraft style layout of the Corvair engine. A flat six with air cooled cylinders and aluminum case and heads, its design was similar to the Continentals, Lycoming and Franklin engines. He proceded to experiment with converting the Corvair for aircraft use and this was mentioned in the Bob Whittier article. EAA Chapter 89 provided another resource in the form of a member who had collected three Corvair engines but was now willing to part with them for, as I recall, $25. Soon we were disassembling them in the basement of our residence hall, with the fumes from the cleaning fluids causing consternation to some of the other residents.

These were all the early 145 cu. in. engines, and what others were writing, including Pietenpol himself, was that the 1964 and later 164 cu. in. model was preferred. He had flown the 145, but was in a position to know. For comparison purposes, the Continental 65 has 170 cu. in. Because it also had a rear-mounted flat air cooled engine, the Volkswagen could be thought of as the Corvair's European cousin. In France, enthusiasts had put the VW to work powering the Jodel and the Turbulent single-seaters and in England there was the Taylor Monoplane. All were even smaller than the Pietenpol Scout, but at roughly half the displacement of the Corvair the VW was not considered big enough.

Besides Pietenpol's work on the Corvair, R. Huggins had developed a plan for aircraft conversion along with his version of the VW. A Corvair conversion which appeared clean and workable was Bob Rofshus' installation on his Heath Parasol which he brought to Oshkosh. It used eyebrow scoops in place of the factory fan shroud and had a Stromberg aircraft carb with intake tubes grafted directly into the rear of the manifolds on the Corvair heads. In recent years the Corvair has found a new advocate in Wm. Wynne who has gained a new generation of enthusiasts for this engine.

The Rofshus Corvair Heath

Besides its aircraft style layout, the Corvair engines I was examining had four mounting flanges on the base of the crankcase which were unused in the automobile application. When I retrieved the Franklin J-3 mount from Abe as mentioned earlier, I was surprised to find a near-perfect fit! Later, I read that Pietenpol was similarly surprised. I have never read of G.M.'s purposes or design procedures for the Corvair engine relative to aircraft use, but these mountings meant something.

Later we acquired a 164 inch engine which appeared clean and bright but had suffered internal failure resulting in a badly bent rod. The scrounging instinct reached a new level when we towed home an abandoned 1964 Monza which did have an intact 164 engine. Neighbors again took a dim view of proceedings. Ultimately we had a new Troyer prop on this engine but did not solve the severe weight and balance problems in the GN-1 application or get functional carburation.

Babysitting son John and Corvair at Skunk Works II

Vintage Enterprises, the proprietorship under which the skunk works now operated, may have over-expanded in Stromsburg. A 1941 Chief project had joined the Pietenpol in an adjacent hangar, and its A-65 engine had undergone a major overhaul to new tolerances at Iowa Western College aviation school. We were undertaking a major expansion at work, and when the offer to buy a Chief airframe for a price we had paid for both airframe and engine materialized, we got out of the Aeronca business. The Chief went to Aeronca enthusiast Irv Woodhams, to be delivered to Wag Aero in Wisconsin. We later learned that a plan was in the works to offer homebuilt plans for the Chief along the lines of their "Cubby."

The Iowa Western Continental A-65-8 - after twenty five years

Now we were left with a like-new A-65, the Continental motor mount already supplied by Giff Gillingham, and the Sensenich prop from the '41 Chief. Although the Corvair was always an attractive alternative and we would have liked to experience first hand what Bernard called "the smoothest engine he had ever flown", we sold off the Corvair engine complete with mount, prop and manuals. The Continental went on with minor changes to the cowling, and weight and balance were back on track.

The Corvair Pietenpol that never was

The final FAA inspection does not stand out in memory, probably because it was uneventful. No discrepancies were found and the inspector quipped words to the effect "it looks like an airplane". A test area was outlined for the 25 hour test period and that was that.

When we first fired up the Continental powered Pietenpol, the plane was transformed from a quiet and inert object which we had spent much time around, into a fire-breathing, quaking monster of a thing. At least it certainly seemed so. 65 horsepower does not seem like much, but when it batters the air with a six foot propeller and barks through a straight exhaust it can satisfy any appetite for noise! That sound retreats somewhat when the plane lifts away from the ground, which N7152 did for the first time in 1978. It was a red letter day to be sure. It flew very similarly to the Champs we were used to. We went up to 3,000 feet, did turns and various throttle settings, and after an hour went spiralling down to a rather good landing. No one reported hearing any whooping on the ground.

Since no passengers are allowed during the test period, the front cockpit was covered during this period. A three surface flat panel windscreen about ten inches high gave very good protection from the slipstream and a similar one installed in the front cockpit when it was opened later. Some owners report slipstream discomfort, so an adequate windscreen is important. A baseball cap stays on in flight and goggles are not really necessary in N7152. The first flight was done with crash helmet and nomex suit! The test period flights were completed in the first year. The only structural weakness uncovered was in the left engine eyebrow scoop. An aluminum attachment strap failed and was replaced by a stainless piece.

This striking Piet has radios recessed in the center section!

No significant changes were ever made to N7152 for the next 25 years. It always started right up after winter layovers and the only trim adjustment was to raise the stabilizer leading edge one-quarter inch. Most work consisted of washing off the winter accumulation of dirt and dust. The spark plugs were cleaned and gapped once. The fabric tested green at the 18 year mark. It was flown mostly to amaze its owner and to look at the ground...not many hours have accumulated. It had to compete with a Cherokee 180 from the Stromsburg Flying club for flying time. Chet Peek reports in his recent book that no Pietenpol builder registered regrets in making this airplane his choice. I would have to agree.
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