Overview ²

• North American BT-9/BT-14/NA-64
• Role: Trainer
• Manufacturer: North American Aviation
• First flight: April 1936
• Primary user: United States Army Air Corps
• Number built: +260
• Unit cost: $20,000
• Developed from: North American NA-16

The North American Aviation BT-9 was a low-wing single piston engine monoplane primary trainer aircraft that served with the United States Army Air Corps (USAAC) and other allied countries during World War II. It was a contemporary of the Kaydet biplane trainer and was used by pilots in Basic Flying Training following their completion of Primary in the Kaydet. In United States Navy (USN) service it was designated the NJ-1.

Design and Development ²

The BT-9, designated NA-19 by the manufacturer, evolved from the North American NA-16, which first flew in April 1935. The BT-9 design first took to the skies in April 1936.

Fabric covered the movable surfaces on the tail and wings, as well as the sides of the fuselage from just behind the firewall to the tail. The remainder of the aircraft was metal-covered and featured fixed (non-retractable) landing gear. The Army Air Corps purchased a total of 199 BT-9’s, BT-9A’s and BT-9B’s. Many foreign countries also used variants of this aircraft under North American’s NA-16 designation.

The BT-14 (NA-58) and the similar NA-64 Yale I represented a major aerodynamic improvement over the NA-16 series, with a longer all metal fuselage replacing the fabric covered fuselage of the earlier NA-16’s. The BT-14 featured a Pratt & Whitney R-985 engine versus the Wright R-975 used on the BT-9 and NA-64. As well as metal skin replacing the fabric on the fuselage, the fin was changed from having a corrugated surface on the BT-9’s to being a smooth stressed skin structure and was moved aft slightly, lengthening the rear fuselage while the engine was moved forward to maintain the CG. The rudder was also changed from the rounded shape used previously to one with a roughly triangle shape with the broadest part being at the bottom, and the canopy was redesigned. The new fuselage would provide the basis for the entire AT-6 family, when fitted with the larger Pratt & Whitney R-1340 engine, a new wing with retractable undercarriage and minor changes for a gunners position.

The BT-9 and NA-64 suffered from stall/spin problems and a variety of fixes were tried. The USAAC temporarily settled on using slats on the later versions of the BT-9 however these did not work well, and later developments would have the outer wing panels swept forward slightly so that they no longer had the straight trailing edges of the BT-9 and NA-64. The later swept forward wings were fitted to the BT-14.

Operational History ²

The NA-64 retained the fixed undercarriage layout and was built for the French Armée de l’Air and Aéronavale in 19391940. Just under half were delivered before France surrendered to the Nazis and the remaining aircraft were purchased by the British Purchasing Commission for the Royal Canadian Air Force (RCAF). The RCAF named the type the Yale, and were used initially as intermediate pilot trainers and later as airborne wireless radio trainers. All were sold as scrap post-war but approximately 40 survive today, with about 15 in airworthy condition.

The NA-26, an improved model with retractable landing gear which became the prototype for AT-6 Texan advanced trainer, was developed from the NA-16 design. The Australian CAC Wirraway was also developed from the NA-16.

Variants ²

• North American NA-16: Prototype aircraft, one built.
• North American NA-18: Pre-production aircraft, one built.
• North American BT-9: Two-seat primary trainer for the USAAC, 42 built.
• North American BT-9A: Armed with two 0.30 in (7.62 mm) machine guns, 40 built.
• North American BT-9B: Improved version, 117 built.
• North American BT-9C: Similar to the BT-9B, but with some equipment changes, 97 built.
• North American BT-9D: One prototype only, which lead to the development of the BT-14.
• North American NJ-1: Two-seat primary trainer aircraft for the USN, powered by a 600 hp (447 kW) Pratt & Whitney R-1340 radial piston engine, 40 delivered.
• North American NA-57: France, 230 delivered. Export version of BT-9. First 30 served with French Navy. Most were captured and used by the German Luftwaffe.
• ASJA/SAAB Sk 14, Sk 14A, Sk 14N: Sweden, 136 built. License built version of NA-16-4M. The three only Sk 14N was converted with tricycle landing gear as a trainer for SAAB 21 pilots.
• North American BT-14: Advanced version with lengthened metal fuselage and T-6 outer wing panels, powered by a 450 hp (336 kW) Pratt & Whitney R-985-25 radial piston engine, USAAC, 251 delivered.
• North American BT-14A: 27 BT-14’s were converted to take the 400 hp (298 kW) Pratt & Whitney R-985-11 radial piston engine.
• North American NA-64 Yale: As per BT-14 but with a 420 hp Wright R-975-E3 radial engine and earlier straight wings. Operated by France, Germany, Canada and the United Kingdom, Of 230 ordered, 111 were in France before the invasion and were then used by the Germans. Remaining 119 delivered to RCAF as the Yale.

Operators ²

• Canada: Royal Canadian Air Force
• France: French Air Force (Armée de l’Air); French Naval Aviation (Aéronavale); Vichy French Air Force
• Germany: Luftwaffe used captured NA.57 and NA.64 for flight training and to familiarize aircrew with U.S. aircraft
• United Kingdom: Royal Navy (on loan from RCAF in 1941)
• United States: United States Army Air Corps (until June 1941); United States Army Air Forces (after June 1941); United States Navy
• Sweden: Swedish Air Force

Survivors/Aircraft on Display ²

There are many surviving NA-64 Yales today because of Ernie Simmons, a farmer from near Tillsonburg, Ontario. Simmons bought over 30 Yales in 1946 and kept them on his farm until he died in 1970. These aircraft were subsequently auctioned in 1970, and have been restored by museums and warbird enthusiasts. Most of the Yales currently in existence came from the Simmons collection.

• Museo del Aire de Honduras at Toncontín - BT-9C exported to Honduras as NA-16-2A.

• No original aircraft, but several Yales have been painted or partially modified as BT-14’s.
• Commemorative Air Force - ex RCAF Yale 3450 to be restored as a BT-14.
• National Museum of the United States Air Force - ex RCAF Yale 3417 displayed as a BT-14.

• Swedish Air Force Museum - replica using parts from a Yale, Wirraway, and a real Sk 14.

• Canadian Harvard Aircraft Association - ex RCAF 3399 - airworthy
• Canadian Warplane Heritage Museum - ex RCAF 3350 and 3400 (airworthy) and 3411 (on static display)
• Commonwealth Air Training Plan Museum - ex RCAF 3396 - under restoration
• Bomber Command Museum of Canada - ex RCAF 3404 - under restoration to airworthy
• Pima Air & Space Museum - ex RCAF 3397 - on display
• Reynolds-Alberta Museum - ex RCAF 3458 - on display
• Western Canada Aviation Museum - ex RCAF 3430 - on display
• Legend Of Aces Aviation - ex RCAF 3383 - under restoration to airworthy wireless trainer
• Legend Of Aces Aviation - ex RCAF 3456 - under restoration to airworthy
• Plus a couple dozen privately owned in Canada, the US, and Europe

Specifications (NA-64 Yale I) ^3,4

Type

• Single-seat fighter monoplane

Wings

• Low-wing cantilever monoplane.
• Wings in five sections, two-spar center-section, two removable single-spar outer sections and two detachable wing-tips.
• Spars and ribs of aluminum-alloy with smooth stressed skin.
• Balanced and differentially-controlled ailerons have aluminum-alloy frames and fabric covering.
• Split trailing-edge flaps.

Fuselage

• Forward section is of welded chrome-molybdenum steel-tubing with removable side panels.
• Rear section of semi-monocoque metal alloy construction.
• Suitable inspection doors are provided in rear section.

Tail Unit

• Cantilever monoplane type.
• Aluminum-alloy framework.
• Fixed surfaces are metal-covered in non-adjustable.
• Elevator and rudder are fabric-covered, balanced and fitted with adjustable trimming-tabs.

Undercarriage

• Retractable cantilever single-leg half-fork type.
• Air-oil shock absorbers.
• Hydraulically-operated differential brakes and parking brake.
• Wheel-type skis may be installed.
• Steerable tail-wheel with full 360° swivel.

Power Plant

• One 840-hp Wright "Cyclone" R-1820-77 nine cylinder radial air-cooled engine on welded steel-tube mounting. ⁴
• NACA cowling.
• Three-bladed constant-speed airscrew.
• Two fuel tanks in center-section (170 US gallons capacity).
• Oil tank (15.5 US gallons) on top of engine-mounting.

Accommodation

• Pilot’s cockpit over wing with sliding and closure.
• Windshield of Plexiglas, side panels of shatter-proof glass.
• Baggage space in rear monocoque section.
• Provision is made for installation of 114 lb (51.71 kg) of radio equipment.
• Two synchronized Colt 0.30-cal or 7.67 mm machine guns.
• North American flush-type bomb-racks in outboard wing-sections.

Dimensions ⁴

• Wing span: 37 ft 4 in (11.38 m)
• Length: 27 ft 6 in (8.38 m)
• Wing area: 227.5 ft² (21.14 m²)

Weights ⁴

• Weight, empty: 4,650 lb (2,109 kg)
• Crew: 190 lb (86 kg)
• Weight, loaded: 6,850 lb (3,107 kg)

Armament ⁴

• Guns: Four 0.30-in machine guns, two in cowl and one in each wing
• Cannon: Two 20-mm cannons housed in underwing pylons
• Bombs: Underwing racks for four 100-lb bombs

Performance ⁴

• Maximum speed: 280 mph (450.6 km/h)
• Cruising speed: 235 mph (378.2 km/h)
• Landing speed: 70 mph (113 km/h)
• Climb rate: 2,381 ft/min (725.7 m/min)
• Service ceiling: 30,000 ft (9,144 m)
• Range: 660-690 miles (1,062-1,110 km)