The Douglas DC-4E was an experimental American airliner that underwent development before World War II.
However, it did not progress to production as it was replaced by a completely new design, the Douglas DC-4/C-54, which proved to be highly successful.
Following the sale of the sole DC-4E prototype to a Japanese airline, it was covertly dismantled for examination by Nakajima at the request of the Imperial Japanese Navy.
As a result, numerous innovative design elements of the aircraft were incorporated into the Nakajima G5N bomber.
The genesis of the design can be traced back to 1935 when United Air Lines identified a need for a larger and more advanced aircraft to replace the DC-3, even before the latter had taken to the skies.
The project garnered significant interest from other airlines, including American Airlines, Eastern Air Lines, Pan American Airways, and Transcontinental and Western Air (TWA), who each contributed $100,000 towards the development costs.
However, as expenses and complexity escalated, Pan American and TWA withdrew their funding in favour of the more cost-effective Boeing 307 Stratoliner.
The DC-4, as it was initially named, was designed to accommodate up to 42 passengers in a day configuration (13 rows of two or more seats with a central aisle) or 30 passengers as a sleeper transport, similar to the DST.
It boasted several innovative features, including a nosewheel, auxiliary power units, power-boosted flight controls, alternating current electrical system, air conditioning, and planned cabin pressurization.
The unique tail design, featuring three low vertical stabilizers, allowed the aircraft to fit into existing hangars and provided sufficient vertical fin area to enable take-off with only two engines on one side operating.
The wing planform was similar to that of the DC-3, with a swept leading edge and almost straight trailing edge.
The four Pratt & Whitney R-2180-A Twin Hornet 14-cylinder radials, each with a power output of 1,450 hp (1,080 kW), were mounted with noticeable toe-out, particularly the outer pair.
The prototype (NX18100, s/n 1601) first flew, without incident, on June 7, 1938, from Clover Field in Santa Monica, California, piloted by Carl Cover.
Testing issues, however, delayed the Approved Type Certificate until May 5, 1939.
It was used by United Air Lines for in-service evaluation in 1939. On June 9, 1939, when the DC-4 was in Dayton, Ohio, along with Carl Cover, Orville Wright was a passenger on a flight over the city.
Although the aircraft was relatively trouble-free, the complex systems proved to be expensive to maintain and performance was below expectations, especially with an increase in seating to 52 and gross weight to 65,000 lb (29,484 kg).
The design was abandoned in favour of a marginally smaller, less-complex four-engined design, with a single vertical fin and 21 ft (6.4 m) shorter wingspan.
This newer design was also designated DC-4, leading the earlier design to be redesignated DC-4E (E for “experimental”).
In late 1939, the DC-4E was sold to Imperial Japanese Airways, which was buying American aircraft for evaluation and technology transfer during this period; at the behest of the Imperial Japanese Navy, it was reverse-engineered, becoming the basis for the unsuccessful Nakajima G5N bomber.
To conceal its transfer to the Nakajima Aircraft Company for study, the Japanese press reported shortly after purchase that the DC-4E had crashed in Tokyo Bay.
Specifications Crew
3 Capacity
42 passengers Length
97 ft 7 in (29.74 m) Wingspan
138 ft 3 in (42.14 m) Height
24 ft 6 in (7.48 m) Wing area
2,155.01 sq ft (200.207 m2) Empty weight
42,564 lb (19,307 kg) Gross weight
61,500 lb (27,896 kg) Max take-off weight
66,500 lb (30,164 kg) Powerplant
4 × Pratt & Whitney R-2180-S1A1-G Twin Hornet 14-cyl,
Two-row air-cooled radial piston engines,
1,450 hp (1,080 kW) each Propellers
3-bladed metal variable-pitch propellers Performance Maximum speed
245 mph (394 km/h, 213 kn) at 7,000 ft (2,134 m) Cruise speed
200 mph (322 km/h, 174 kn) Range
2,200 mi (3,500 km, 1,900 nmi) Service ceiling
22,900 ft (7,000 m) Rate of climb
1,175 ft/min (5.97 m/s) Wing loading
28.5 lb/sq ft (139 kg/m2) Power/mass
0.0943 hp/lb (4.8kW/kg)
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. Charles Daniels Photo Collection.
