Granville Gee Bee Model Z Super Sportster

Suffering from the effects of the Great Depression, the Granville Brothers decided in July 1931 to build an aircraft to compete in that fall's Thompson Trophy competition at the National Air Races in Cleveland, Ohio. They hoped that a victory in the prestigious race would lead to additional orders for their line of sporting aircraft.[1]

Constructed in less than five weeks at a cost of under $5,000 USD, the Gee Bee (for "Granville Brothers") Model Z, named City of Springfield, was a small, tubby airplane. It was essentially the smallest possible airframe constructed around the most powerful available engine of a suitable size,[2] a supercharged Pratt & Whitney Wasp Junior (R-985) radial engine, producing 535 horsepower (399 kW).[1]

First flying on August 22, 1931, the Gee Bee Z quickly proved to be tricky to fly, but fulfilled every expectation with regards to its speed. Flown by pilot Lowell Bayles, the Gee Bee Z attained the speed of 267.342 miles per hour (430.245 km/h)[3] at the National Air Races during the Shell Speed Dash qualifying on September 1, then went on to win the Goodyear Trophy race, run over a course of 50 miles (80 km), the next day at an average speed of 205 miles per hour (330 km/h). On the September 5, the aircraft's engineer, Bob Hall, flew the Gee Bee Z to victory in the General Tire and Rubber Trophy race, then won again the next day in a free-for-all event.[4]

In the Thompson Trophy Race on September 7, Bayles was triumphant, winning with an average speed of 236.24 miles per hour (380.19 km/h), winning over competitors including Jimmy Doolittle, James "Jimmy" Wedell, Ben Howard, Dale Jackson, Bill Ong, Ira Eaker, and Hall, who finished fourth in a Gee Bee Model Y.[4]

Following the Thompson Trophy race, the Gee Bee Z was re-engined with a larger, 750-horsepower (560 kW) Wasp Senior radial, in preparation for an attempt at establishing a world speed record for land planes at Wayne County Airport in Detroit, Michigan.[1] Unofficially clocked at 314 miles per hour (505 km/h) on a trial run, it surpassed the previous record of 278 miles per hour (447 km/h) by attaining 281.75 miles per hour (453.43 km/h) on December 1, 1931, but the margin was too small for the record to be officially registered.[4] A further record attempt on December 5, 1931, ended in tragedy, the aircraft suffering a failure of its right wing on its final approach. The air racer quickly rolled over several times, out of control, and crashed amid a large fireball, killing Bayles.[2]

It was suspected that the Model Z's crash during the December 1931 speed run was due to an unexpected failure of the gasoline tank cap, which may have come loose and passed through the windshield. A bullet-proof windscreen and internal fuel caps were part of the later Gee Bee designs. Analysis of motion picture film of the event, examined frame-by-frame, is inconclusive. Aileron flutter was thought to be the cause of the wing's failure.[5] It was theorized that the gas cap struck the pilot and incapacitated him, causing a sudden upset in pitch that led to uncontrolled flutter in the right aileron, exerting undue high vibration stress on the right wing, causing it to fail. The air racer immediately pitched up out of control. [4] Tests of an exact reproduction aircraft has since shown that the Gee Bee Z was susceptible to aerodynamic flutter at high speeds.[1] The 1932 R-1 and its sister ship, the R-2, were the successors to the previous year's Thompson Trophy-winning Model Z.

Data from [4][7]

General characteristics

• Crew: 1 (pilot)
• Length: 15 ft 1 in (4.60 m)
• Wingspan: 23 ft 6 in (7.16 m)
• Height: 7 ft (2.1 m)
• Wing area: 75 sq ft (7.0 m²)
• Airfoil: M-6
• Empty weight: 1,400 lb (635 kg)
• Gross weight: 2,280 lb (1,034 kg)
• Fuel capacity: 103 US gallons (390 L; 86 imp gal)
• Powerplant: 1 × Pratt & Whitney Wasp Junior radial, 535 hp (399 kW) supercharged
• Propellers: 2-bladed Curtiss Reed fixed pitch, 8 ft 2 in (2.49 m) diameter

Performance

• Maximum speed: 232.314 kn (267.342 mph, 430.245 km/h)
• Cruise speed: 200 kn (230 mph, 370 km/h)
• Range: 780 nmi (900 mi, 1,400 km)

Kermit Weeks, founder of Fantasy of Flight, used a Gee Bee Model Z as his main character "Zee" in a series of children's books set around the interwar period. [8]

A modified, flying replica of the Gee Bee Model Z appeared in several scenes in the 1991 Walt Disney feature film, The Rocketeer.

Related development

• Gee Bee Model R

Aircraft of comparable role, configuration, and era

• Hughes H-1 Racer