Aeroplane – June 2018

Los Angeles

Philadelphia

New York

Houston

Chicago

Fuselage Metal semi-monocoque

construction (some load carried by

the skin). No need for internal

bracing saves weight and clears

space for payload/passengers.

Streamlined design reduces drag

and exudes modernity

Wings Cantilever outer panels

joined to constant-chord centre

section with three main spars and

streamlined engine nacelles.

Structure is strong, aerodynamically

clean and relatively light

Landing gear

Retracts into nacelles,

reducing drag

Split flaps Safely lower

landing speed and distance

Propellers Constant

speed mechanism

automatically swivels

blades to optimum

angle for set rpm

NACA cowlings Direct cooling

airflow to hottest engine

components and reduce drag,

improving fuel efficiency

Engines Reliable and

efficient air-cooled radials

with enough surplus power

to drive auxiliary systems

Hydraulic system

Engine-driven

pumps supply

pressure to operate:

Wheel brakes

Wing flaps

Landing gear

Pump

Controls

Cowl flaps

Autopilot

Heat and ventilation system

Exhaust heat exchangers supply hot air

to cabin. Vents supply cool air

De-icing system Exhaust

air from engine vacuum

pumps inflates shoes on

wing and tailplane leading

edges to break up ice

How the DC-3 performed against

contemporary types

Production of the DC-3/C-47

and other variants dwarfed that

of other transport types in WW2

Service ceiling (m)

Cruising speed (km/h)

Passengers Seven

rows of seats carry

21 passengers in

relative comfort,

making the DC-3

economically viable

Sperry autopilot

Maintains heading

and pitch, relieving

pilot workload

The DC-3: a thoroughly modern airliner Performance compared Production

Ranges (km)

100 150 200 250 300 350

5000

6000

7000

8000

DC-3 and main variants

Total 16,079

L2D (Japanese licence-

built version) 487

Li-2 (Russian licence-

built version) 4,937

C-47 and other US-built

military variants

10,048

Ju 52 4,845

C-46 3,181

C-54 1,170

DC-3 607

2

3

1

5

4

Vacuum pump

De-icing shoes

Air supply

Cold Hot Conditioned

Heat exchanger

Mixer

Boeing 247

1,296

Trimotor

885

DH86

1,223

DC-3

2,400

1

(^23)
4
5
Boeing 247
10 passengers
Ford Trimotor
17 passengers
DH86 Express
10 passengers

DC-3

21 passengers

T

he DC-3 was initially

developed as a widened

sleeper version of the

successful DC-2 airliner,

being called the Douglas Sleeper

Transport or DST. Reconfi gured as

a straight airliner with 21 passenger

seats, rather than 14-16 sleeper

berths, it became the ‘Douglas

Commercial Three’. With a wider

cargo door and greater fl oor

strength, it was further developed

into a range of military versions,

the most numerous being the

C-47. At the time, and crucially

also after World War Two, the

DC-3 family offered unbeatable

payload effi ciency fi gures that

enabled profi table freight

and airline work. It expanded

commercial aviation into new

environments, which aircraft had

previously not been able to serve

for physical or cost reasons. In

this Briefi ng File we consider the

technical elements and capability of

the DC-3 family, in what proved

to be an ideal, balanced design.

When the DC-3 fi rst fl ew

in 1935, several technological

aspects enabled the type’s success

because they had just reached a

stage of development that was

reliable and effective. Some factors

were as much social as technical:

biplanes — such as the Curtiss

Condor — were viewed as being

‘old’ in contrast to the new metal

monoplanes, while wooden

airframes and, less reasonably,

tri-motors were being avoided

by the public and airlines after

the notorious 1931 Fokker F.VII

crash in which all eight on board

died, including famous American

football coach Knute Rockne.

The Boeing 247 just preceded

the DC-3 into service. It was a

sound design, but certain choices

made in relation to its airframe —

such as the thick wing — saw to it

that the DC family boasted better

performance. The obstruction of

the 247’s cabin by the wing spar

was a compromise, affecting ease

of loading and proving unpopular

with passengers. Though the

DC-3 did not beat the 247 in

altitude capability, it had enough

operating height for its users and

their requirements, including

the hot, high and engine-failure

performance reserve demands laid

down by the fi rst customers. More

BRIEFING FILE The technology that combined to make the DC-3 an unbeatable success

Under the skin of aviation technology and tactics

DOUGLAS DC-3

82 http://www.aeroplanemonthly.com AEROPLANE JULY 2018

This pre-war image of a United Airlines DC-3 at Oakland, California,

shows several aspects of the type discussed here including the all-

metal structure, a major selling point for the airlines in the era.

VIA JAMES KIGHTLY

82-83_AM_BriefingFile_July18_CC C.indd 82 04/06/2018 07:17