The Aviation Historian — January 2018

48 THE AVIATION HISTORIAN Issue No 22

needed to feel they were going somewhere fast:

fast communications, fast cars, fast boats and

particularly, for a few golden years, fast aero-

planes. Design influences travelled in all direc-

tions, but aviation usually seemed to lead. In the

1930s the shape of things to come was a pointy

egg. However, there were signs that, whatever

it did for pencil sharpeners or toasters, this form

alone was no longer the answer to going faster.

Into the windtunnel

Aircraft builders were becoming inspired —

and agitated — by the flow of new information

coming from newly-established windtunnels.

Up until the 1920s, a designer could rely on the

“if it looks right it will fly right” maxim, and as

long as the resulting object flew at all there was

nobody to say “it would have been better if.. .” It

may have been the ability of “boffins” to second-

guess the hands-on engineers that made the latter

hostile to this new breed of experimental scientist

— the “tunnel jockey”. According to Matthew

Freudenberg’s Clear Air Turbulence: The Life of

Anne Burns (Charlton, 2009), these engineers

and scientists were referred to throughout the

British aircraft industry as “narks”, in the sense

of an annoying person or thing; for example, an

engineer engaged in solving a particular design’s

aileron flutter was a “flutter nark”.

Hawker designer Sydney Camm is said to

have blamed the narks at the UK’s National

Physical Laboratory (NPL) — which had been

operating arguably the most reliable and accurate

windtunnels in the world since 1902 — for his

Hurricane fighter turning out to be slower than

anticipated. Roland “Roy” Chaplin (who was on

the Hawker design team at the time) said: “We

were told by the NPL that no improvement in

drag could be obtained by reducing the thickness/

chord ratio [t/c ratio] of the wing below 20 per

cent”.^1 The established version is that this was

an error, and that Camm shouldn’t have listened

to the “experts”.^2 Some of the latter were even

accused by Harry Knowler of Saunders-Roe,

quoted in an article by F.B. Bradfield and D.L.

Ellis of the NPL (The Use of Wind Tunnels, Flight

January 12, 1939), of “cooking the data”.^ In the

same article, Ellis stated that tests had indeed

shown a drag rise; much of the testing was for

propeller-blade research, in which lift/drag

ratio was paramount, and these drag curves do

not change much below 20 per cent. Camm was

being told that his choice of wing was efficient,

not specifically that it was fast. His interceptor

would be good at converting power into take-off

and climb performance, with a good strong wing;

exactly what he wanted to hear.

A far larger problem for the Hurricane arose at

the wing root. A 1940 Royal Aeronautical Estab-

lishment (RAE) study of a full-size Hurricane

mounted in its 24ft windtunnel at Farnborough

showed 9·9lb interference drag where the fuselage

faired into the wing, at only 68 m.p.h. (110km/h)

and at 0° incidence.^3 There was also an expansion

of the boundary layer (see glossary, pages 50–51),

again described as inexplicable. For comparison,

the completely unfaired twin-engined Westland

Whirlwind fighter gave 2lb in the same test in the

same windtunnel, at 2° off the horizontal.

With increased flow-separation at speed, the

Hurricane’s interference problem could only

get worse. Whether or not the wing itself was a

significant cause of inordinate drag-rise, the wing

root definitely was. When the propeller was spun

and the velocity over the wing root increased,

the drag shot up. The report was something of a

ABOVE Named in honour of Mussel Manor, the clubhouse near the Short brothers’ first aeroplane factory on the

Isle of Sheppey, the Short S.7 Mussel I, G-EBMJ, is seen here at Rochester in July 1926. The pinnacle of stream-

lined design at the time, the metal two-seat floatplane was transformed by simple fabric fillets, clearly visible here.

PHILIP JARRETT COLLECTION