WI Steve Wittman designed a primary trainer airplane?

[riggerrob]

As the title suggests, what would a primary trainer airplane look like if it was designed by Steve Wittman?
Remember that Steve managed a busy civilian school that trained pilots for the USAAF during WW2.
Steve was famous for designing a series of dirt-simple planes that won a lot of races during the 1930s. Post-War Steve continued racing in Goodyear Formula 1 and the later Formula V (VW engine) classes. Steve's most prolific airplane was the post-war Tailwind 2-seater touring airplane. Hundreds of Tailwinds were built by amateurs who bought plans from Steve.

Would the fictitious primary trainer have high wings? ..... mid-wings? ...... or low-wings?
Wooden wings? ....... fabric wings? ...... sheet aluminum wings?
Strut-braced wings? ........ wire-braced wings? .... cantilever wings?
Tandem seating? ........ side-by-side seating?

The only predictable component is the undercarriage which would be spring-steel .... or spring aluminium?

 

[Dynasoar]

Here we go!

While virtually all trainers of that period were tandem, I think Wittman was practical enough to visualize the advantages of side by side seating in a primary training situation. With much improved communication and no change in CG location and handling with the instructor absent (crew located on CG) the side by side seating is ideal. Since speed is not an objective (first time for Steve) the increased cross section of the fuselage and a relatively thick cantilever ply covered wing would not be a problem. Wing thickness and weight could be reduced if the wing was stressed for a lower load factor- negative G, and the higher positive load factor obtained with wires or a strut in tension on the underside of the mid located wing. Flaps and slots.

Fuselage steel tube, fabric covered. The surprise is the proposed engine, which would be a Ford V-8 (desirably the aluminum block variant from the Arrow-Sport program). Direct drive, since a noisy prop would add to the fun. Lower than peak RPM would be necessary to avoid a gearbox, so an existing McCullough centrifugal blower and reduced compression would probably permit about 80-85 HP at maybe 3300 RPM. Alternatively, a simple reduction drive, possibly using T style planetary gearing, would allow 100 or so HP into a larger diameter prop, for better takeoff and climb.

Will work up dimensions and performance in more detail if desired, but believe stall at a little under 50 MPH and ROC of no more than 800 FPM would work for a loaded trainer.

Dynasoar

 

[marathag]

So a slightly larger. more powerful Aeronca C3 that was an early side by side two seater, with Struts rather than wires to get around the 1937 FAA regulations on no more wire bracing?

 

[Dynasoar]

"marathag, post: 15821334, member: 68581"]So a slightly larger. more powerful Aeronca C3 that was an early side by side two seater, with Struts rather than wires to get around the 1937 FAA regulations on no more wire bracing?

The requirement was for a Primary trainer. Something to go solo and basic XC. Looking for something cheap so Steve could make a profit, and maybe even build them in locally. The Ford flathead with $98.00 blower should produce the equivalent of Lycoming O-235 performance (tho heavier). As for the airplane I was visualizing something more like the Andersson/MBB/SAAB shoulder wing configuration. The flaps would give the student at least a taste of a more complex airplane, while the slots would tame slow flight. Conventional gear (steel leaf) with lockable tailwheel to prevent falling asleep on the runway. Radiator either below and behind crew, or in wing roots. Plywood wing surfaces- a little more weight, but less maintenance. Well baffled fuel tanks a little further out on the wings than most aircraft (except Grumman AA-1 series where they are full span) to provide a measure of fire safety and add a little systems complexity for the student.

Dynasoar

 

[Dynasoar]

Addition to my previous post. Trying to come up with a primary trainer which would mimic some of the characteristics that an air cadet type would encounter in later aircraft. Not a "Floater" on landing, but adequate power for reasonable maneuvers.

Looking into the proposed powerplant, the 239 cubic inch Ford V-8 was cast in aluminum a number of times, starting in early 1935 for the Preston Tucker/Harry Miller Indianapolis Speedway project (production cast iron blocks used), at least two Department of Commerce "cheap airplane" programs (which also demonstrated acceptable performance by Plymouth and Studebaker cast iron engines). I understand that the cores for casting aluminum blocks allowed cylinder bores sufficient for dry steel liners with larger bore than standard, and tho I have never seen photos, forward and aft exhaust ports departing front and rear of the block and wider center porting. I believe that a longer stroke crankshaft was also available, so engine displacement could be increased substantially, to around 270-280 cubic inches. The prewar McCullough centrifugal supercharger had a vertical impeller axis so cockpit visibility wouldn't be impaired. Liquid cooling would facilitate a safe cockpit heater, which would be welcome in Steve's Wisconsin.

Revise direct drive HP up to 105 at 2950 RPM, and reduction drive to 120 at 3250, with the major benefit of lower prop RPM being increased diameter and efficiency. Neither aircraft or engine would require any CAA approvals if considered military aircraft.

Dynasoar