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ABSTRACT:     Article and related photos about the Knight Twister and Col. Marion Unruh's modification of it into the Pretty Prairie Special series. Includes good 3-view of Knight Twister design.
The Colonel's Pretty Prairie Special
Back in the thirties it wasn't uncommon to name airplanes after cities -- like Oshkosh and Los Angeles. Colonel Unruh started his little biplane in 1937, and named it after the little town of Pretty Prairie, Kansas. Twenty nine years later, with another plane in between, the Knight Twister-based design took to the air for the first time.
 
(From Homebuilt Aircraft (Air Progress), Summer 1968, Page 28)
 
By Staff

 

The Colonel's Pretty Prairie Special

Cover Pretty Prairie Specials brighten sky over Rockford at last EAA fly-in. PPS-II on left was started in 1937 by Marion Unruh, finished in 1966. PPS-III was built by him during mid-1950's.

Back in the thirties it wasn't uncommon to name airplanes after cities -- like Oshkosh and Los Angeles. Colonel Unruh started his little biplane in 1937, and named it after the little town of Pretty Prairie, Kansas. Twenty nine years later, with another plane in between, the Knight Twister-based design took to the air for the first time.

Retired Air Force Colonel Marion D. Unruh of Pretty Prairie, Kansas, reports he made his first flight with PPS II-Model 1 on June 27, 1966, but the single seater bipe was 29 years (repeat, 29 years) in the construction stage. It was started in 1937 at France Field in the Panama Canal Zone with Marion using basic Knight Twister plans. At the time, he decided upon a stiff leg landing gear and a conventional wing structure with both internal and external bracing.

Smooth lines and extremely short wings are apparent in these photos. Fuselage was lengthened behind cockpit to provide better stability.

However WW-2, Korea, raising a family and numerous transfers necessitated sidetracking PPS II, but Marion did commence design of PPS III while stationed in Japan in 1950, and wound up making a first flight in Texas in 1957. The Menasco powered two-seater was designed to fit into a crate no more than 12-ft long for storage/shipping purposes. About two years ago, Marion sold his PPS III to Russell C. Brown, Emporia, Kan., and then returned to completing the PPS II. Experience with "III" indicated some changes in design would be beneficial -- most important being a 16-inch increase in fuselage length. A pylon type cabane structure, a larger vertical tail surface, as well as a shock absorbing landing gear were fitted. Marion says, "There is no doubt PPS II has a lot of Knight Twister looks in it. The wing size and taper are direct copies of the KT and the fuselage structure was copied from the original plans. However, it was sawed in two just aft of the cockpit and 16-inches added at this point. This probably had a considerable effect on taming the bird. From there on out, the plans were out the window."

Menasco powered Pretty Prarie III, at left, was built while PPS II was in its construction stages. Wing leading edges were filled with Styrofoam blocks, shaped to contour, and covered with fiberglass skin.

Weight and balance calculations dictated the need from an engine mount 35-1/2 inches long! As the Colonel says, "There's enough room behind the engine to stow survival gear for a trip around the world."

Wing and ailerons are all-wood structures, fuselage and tail are steel tube. Covering is a combination of fiberglass and fabric. Wheel pants, engine cowling, fairings, wing leading edge and tips are of molded fiberglass. Engine 75-hp Continental A-75. Wingspan 15-ft, area 54.2-sq ft, chord MAC 26-27/32-in; overall length 15-ft 5-in; height 5-ft 6-in, Max speed (estimated) 150-mph plus, cruise 120, landing 70. Climb 900-ft/min; range 200 miles. Empty weight 565-lbs, gross 850-lbs. Project cost about $1,500.

Pretty Prairie Special II N8635E was begun in 1937 by Colonel Marion Unruh of Pretty Prairie, Kansas, and made its first flight in 1966. Based originally on Knight Twister plans, the fuselage has been lengthened 16-inches for improved longitudinal stability. Maximum speed with 75-hp Continental is 150-plus, cruise 120. 3-View of Knight Twister

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