The Boeing/Stearman Model 75 primary trainer is probably the best known bi-plane in aviation history. Commonly referred to as the Stearman PT-17, it was manufactured by the Stearman Aircraft Co. in Wichita, KS, from 1934 through 1945. Boeing publicity claims a total of 10,346 Stearman “Kaydet” trainers built, but this figure includes equivalent spare parts. The actual total of Model 75s that were completed from the prototype X-75 to the final E75 built in 1945 was 8428.

In 1938 the Stearman Aircraft Co. became the Stearman Aircraft Division of the Boeing Aircraft Co., so in actuality, the majority of the airplanes manufactured were designated as Boeings. However, they are still almost universally known as Stearmans.

Generally, all the Stearman airframes built are the same with the only major difference being the engine installed. Original engines included the Lycoming R-680 (225 hp); Continental R-670 (220 hp) and the Jacobs R-755 (225 hp). Post-war modifications include the Lycoming R-680 (300 hp), Pratt & Whitney R-985 (450 hp) and the Jacobs R-775 (275 hp).

The propellers generally in use on Stearmans are the Sensenich wooden prop; the ground adjustable McCauley steel blade prop and the fixed pitch Hamilton Standard propeller.

The Stearmans manufactured for the U.S. Army Air Corps were the PT-13; PT-13A; PT-13B; PT-17; PT-18; PT-27 and PT-13D. The U.S. Navy airplanes were the N2S-1; -2; -3; -4; and -5. The primary difference between the Army and Navy airplanes, other than engines installed, was the tail wheel. Army airplanes had a fully steerable tail wheel while the Navy airplanes were equipped with a full swivel type with a lock. Most Stearmans today have subsequently been modified with the steerable tail wheel.

The final version of the Stearman was the E75, designated PT-13D/N2S-5. It was the only complete standardization of an Army and Navy production design during World War II and was totally the same for both services.

Post-war civil requirements for surplus military Stearmans is covered by Aircraft Specification A-743. This document lists all the approved equipment allowed on a standard category Stearman and the items that must have been removed, replaced or modified when the military surplus Stearman was first licensed as a civilian airplane.

Stearman Model 75 Designations

Model            Military Designation            Engine

75                  PT-13                    Lycoming R-680-5

A75                PT-13A                  Lycoming R-680-7

A75                PT-13B                  Lycoming R-680-11

A75B4            N/A
To Venezuela

A75J1             PT-18                    Jacobs R-755

A75L3 and      N/A
A75L5            To various foreign countries

A75N1            PT-17                    Continental R-670-4 & -5

A75N1            N2S-1                   Continental R-670-4

A75N1            N2S-2                   Lycoming R-680-8

A75N1            N2S-4                   Continental R-670-4 & -5

B75                N2S-2                   Lycoming R-680-8

B75N1            N2S-3                   Continental R-670-4

D75N1            PT-27                    Continental R-670
To Canada

E75                PT-13D/N2S-5            Lycoming R-680-17

Engine note:  It was required that all Continental R-670 engines, when transferred to civilian use, be re-designated and have the engine identification plate changed to show the civilian designation.

Continental Engines

Military Designation            Civilian Designation

R-670-5                               W670-6A

R-670-4, -11A                      W670-6N

R-680-8                               W670-17

Aircraft Specifications

Gross Weight – 2950 lb.
Maximum Baggage – 60 lb.
Fuel – 46 gal. (gravity feed) (4-7 gal. not available in flight)
Oil – 4.4 gal.
Power Off Stall Speed – 55 mph (48 kts)
Power On Stall Speed – 51 mph (44 kts)
Do Not Exceed Speed – 186 mph (163 kts)
Normal Cruise Speed – 95 mph (83 kts)
Fuel consumption – 12-13 gal./hour
Endurance – 3.4 hours (approx.) (most pilots plan 2½ hours)
Maximum Range – 300 sm (260 nm) (no reserve) (most pilots plan 200 sm)
Service Ceiling – 13,300 ft.
Initial Rate of Climb – 800 ft./min.
Take-Off Distance – 600 ft.
Landing Distance – 300-500 ft.

Permissible Aerobatics

Spins
Inside loops
Snap rolls under 106 mph (92 kts)
Slow rolls under 124 mph (108kts)
Immelmann turns
Inverted flight
Inverted spins

Airworthiness Directives

Airframe

The Boeing/Stearman Model 75 has had five airworthiness Directives issued for it. Only two of these apply to the stock airplane while the other three apply to agricultural duster/sprayer airplanes.

A.D. 46-24-01

Due to inadequate drainage forward of the ailerons, water drain holes must be drilled in the dural angle forming the lower rear edge of the wing at the aileron gap.

A.D. 50-06-02

Upon initial certification as a civilian aircraft and at each subsequent annual inspection the fuel tank in the center section must be removed and the spars inspected for moisture damage. The drain holes must be ascertained to be open.

Repeated removal of the fuel tank is not required if after the initial inspection of the center section the gap between the fuel tank and the upper surface of the center section is sealed by doping on fabric to prevent moisture from entering the fuel tank compartment.

Propellers

A.D. 54-12-02

McCauley steel blade propeller Models 41D5926 and D-1093. Each 100 hours of operation a magnetic (magnaflux) inspection of hub and blade shanks for cracks must be completed.

Aircraft tachometer must be placarded “Avoid continuous operation at 1500 to 1650 rpm.”

A.D.50-12-1

Hamilton Standard Model 5404. Blades Model 11C1 (Navy 4350, 4350F, 4350F1)

To minimize the possibility of propeller blade shank fatigue failures as a result of noncompliance with a mandatory engine operation restriction, the following precautionary measures should be taken:

1.  Check the marking on the engine tachometer and correctly mark it, if necessary, with a red arc which covers the entire rpm range above 1900 rpm.

2.  Install placard in aircraft to read:
“Avoid all engine operations above 1900 rpm except during takeoff.”

3.  Check position of the propeller and correctly index, if necessary, in the zero degree position (blades in line with crank throw).

Stearman Type Club

Stearman Restorers Association
7000 Merrill Ave., Suite 90
Chino, CA 91710-8800
E-mail: Davco@stearman.net
SRA web site: www.stearman.net

National Stearman Fly-In

National Stearman Fly -n
c/o National Stearman Foundation, Inc.
370 Lloyd Stearman Drive
P.O. Box 1937
Galesburg, IL 61402
E-mail:  Stearman@stearmanflyin.com
Web site:  www.stearmanflyin.com

National Stearman Fly-In held annually the first week of September beginning on Labor Day.