The Aviation Historian — January 2018

Issue No 22 THE AVIATION HISTORIAN 53

big push, designing the future from the California

coast (as often happened in the last century),

essentially getting so close to the optimum for

a multi-engined airliner that evolution slowed

considerably thereafter. It is notable that, three

years after the development of the Northrop

Gamma, Camm’s Hurricane was given, if not the

“wrong” fillet, something far short of optimum.

As an aside, George Klein took part in a 1934

discussion of Arthur Klein’s 1931 work on the

Northrop Alpha, stating that there were two other

ways to get around the problem of a “pocket” at

the trailing root, apart from the installation of a

fillet. These were:

n raising the wing to a higher position on the

fuselage to eliminate the pocket effect;

n giving the fuselage flat sides, making an angle

of 90° to the wing, as on the Supermarine S.5

floatplane racer.^12

The second of these raises the intriguing

possibility that the S.5, model-tested at the

NPL while Ower was in a senior position there,

had a deliberate “anti-interference” shape,

appearing the year after the Short Mussel was

given flat sides via the addition of a fillet. The

S.5 certainly had low interference drag, but the

brief discussion of interference in the published

reports on the aircraft from the NPL seems to

owe more to Muttray’s early over-thinking about

lift-matching than any reference to longitudinal

pressure changes.^13

While Muttray was writing his 1928 article, one

of Parkin’s very first PhD students at Toronto,

and a keen windtunnel user, was Canadian

Beverley Shenstone, who was to preside over the

Spitfire’s superb wing and its “optimum” fillet

in his first proper job since graduation. Super-

marine specialist (and TA H contributor)

Ralph Pegram has incisively called Shenstone

“Mitchell’s Truffle Hound”, but given Shen-

stone’s connections he wouldn’t have had to root

too far for information about fillets. The NACA

Langley visitors’ book, for example, shows that

“B.S. Shenstone of Supermarine, Southampton”

signed in on May 1, 1934, while the McDonnell

wing-root tests were being written up on site.

At the same time, NACA staff translators

were working on another Muttray article, The

Aerodynamic Aspect of Wing/Fuselage Fillets,

which referenced Arthur Klein, and included

an illustration of an idealised wing and fairing,

which looked, in plan form, remarkably like that

of the future Spitfire.^14 Shenstone would not have

to wait for the translation, being fluent in German.

The “tunnel jockeys” were being listened to, and

the results were to become legendary. A photo-

graph dated February 1935, allegedly taken by

Shenstone himself, shows the “right” fairing

under test for flow separation on the root of the

Supermarine F.7/30. John Ackroyd has claimed

that Mitchell was inspired to put big fairings on

the Spitfire as the result of a chat with the pilot of

ABOVE Jack Northrop’s all-metal

Alpha design of 1930 was a classic

example of a fuselage of what was

then considered “good aerodynamic

design” running into trouble over the

wing. Note the small wing fillet, similar

to that of the Hurricane.

LEFT The second of the two Northrop
Betas, with a Pratt & Whitney Wasp
Junior engine. The Beta incorporated
Arthur Klein’s elegant “expanding
fillet”, as used later on the Douglas
Commercials. Klein meticulously
VIA AUTHOR calculated “right” and “wrong” fillets.

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