The Douglas O-46 was an observation aircraft utilized by both the United States Army Air Corps and the Philippine Army Air Corps.
The O-46A, which marked the end of a lengthy series of Douglas observation aircraft, was a casualty of technological advancement.
Originally designed to operate from established airfields situated behind relatively static battle lines, as was the case during World War I, the O-46A was deemed too slow and heavy to evade and outmanoeuvre enemy fighter aircraft, too cumbersome to operate from small, wet, unprepared fields, and too large to conceal beneath trees in a report issued in 1939.
This report proved to be prophetic, as the rapidly changing battle lines of World War II necessitated the use of light, manoeuvrable observation aircraft capable of operating from unimproved airstrips.
As a result, the “O” (observation) designation was changed to “L” (liaison) in 1942.
The O-46 was a derivative of the earlier Douglas O-43.
The 24th airframe of the O-43A contract was completed as the XO-46 prototype, featuring a revised wing and an engine switch from the O-43’s inline engine to a radial engine, specifically the Pratt & Whitney R-1535-7.
The Air Corps placed an order for 90 O-46As in 1935, which were constructed between May 1936 and April 1937.
A minimum of 11 O-46 aircraft were deployed for overseas duty, with two being destroyed during the Japanese raid on Clark Field in the Philippines on 8 December 1941.
The Maryland Air National Guard utilized O-46As for anti-submarine operations off the coast of New Jersey.
The remaining aircraft were deemed obsolete in late 1942 and subsequently utilized primarily for training and utility purposes.
A proposed O-48 variant, featuring a Wright R-1670-3 engine, was designated but ultimately not constructed.
Specifications
O-46A
Crew
2
Length
34 ft 6.75 in (10.5347 m)
Wingspan
45 ft 9 in (13.94 m)
Height
10 ft 8.5 in (3.264 m)
Wing area
332 sq ft (30.8 m2)
Empty weight
4,776 lb (2,166 kg)
Gross weight
6,639 lb (3,011 kg)
Powerplant
1 × Pratt & Whitney R-1535-7 Twin Wasp Junior,
14-cylinder two-row air-cooled radial piston engine,
725 hp (541 kW)
Propellers
3-bladed metal propeller
Performance
Maximum speed
200 mph (320 km/h, 170 kn) at 4,000 ft (1,200 m)
Cruise speed
171 mph (275 km/h, 149 kn)
Range
435 mi (700 km, 378 nmi)
Service ceiling
24,150 ft (7,360 m)
Rate of climb
1,765 ft/min (8.97 m/s)
Wing loading
20 lb/sq ft (98 kg/m2)
Power/mass
1.087 hp/lb (1.787 kW/kg)
Armament
Guns
2 × .30 Cal (7.62 mm) Browning machine guns
(One wing-mounted and one flexible).
Sources
McDonnell Douglas Aircraft Company 1st 75 Years Aviation Book-McDonnell Douglas.
McDonnell Douglas Aircraft since 1920, Volume 1-René J Francillon.
San Diego Air and Space Museum Archive.
The National Museum of the U.S. Air Force.
