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IN T H I S
ISSUE:
African Air Survey - The Technician's
Dilemma
Up, Out and Down- Elastic Navigator
- Aircraft Intelligence- Swedish Aeronautical
Research
"Source of all Fower"
View Halloo!- - - The Commercial Future
of Helicopters - - -
606
611
612
614
615
616
617
618
620
FRIDAY. 14 NOVEMBER 1952
Hushing the Helicopter
MAURICE A. SMITH, D.F.C.
ASSISTANT EDITOR
No. 2286 Vol. LXII.
IGHTEEN months ago we called for a realistic approach to the problem of aircraft
noise—the exterior noise, more particularly from the engine—and we treated
rotorplanes as one special case. Subsequently, when discussing the matter with
engineers and operators, we have been a little disconcerted to find that for the most part,
far from having given consideration to solving the problem, few of them realized—or
at any rate were prepared to admit—that the problem existed. One or two of the designers
not unnaturally passed the buck by remarking that, until the operators wrote-in a requirement, they had no call to add silencers to helicopters. With the desire to avoid more
accessories and reduce the somewhat marginal payload of the present small helicopter
we can sympathize, but not with the ostrich-like attitude. On commercial helicopters
the cost and weight of silencing should be faced; soon it will have to be.
Rotating-wing aircraft have really come into their own for military roles in Korea
(even America has no rotorplane airline as yet). What is the attitude towards noise
under war conditions ? Opinions from ground observers in Korea are hardly to be expected,
but we may quote again one anonymous statement, based on airborne experience,
which is by no means irrevelant. It seems that troops taken into battle in helicopters
". . . have settled down to the fight at once because they are both pre-deafened and
inured to vibration."
In bis lecture last week (summarized on pages 620-623) Mr. Peter Masefield stated
that "for some reason as a people we, the British, seem to be particularly susceptible
to, or specially intolerant of, noise from the air . . ." Later he said that if the noise
problem could not be solved—or diverted—we should have to think again about the transport helicopter. He added that the maximum amount of silencing tolerable from the payload point of view must come from detail design of the aircraft. In the discussion which
followed, Dr. Hislop, head of B.E.A.'s Helicopter Group (who had a good deal to do
with noise-measurement during the trials of the Westland S.51 and Bristol 171 helicopters
from the Waterloo Site), implied that the noise problem was being over-rated. On the
other hand, Mr. Briscoe of the Ministry of Civil Aviation said that there was official
concern about noise.
Mr. Lennox-Boyd, Minister of Transport and Civil Aviation, in the course of the
recent Civil Aviation Debate in the House, was more forthright. He said ". . . helicopters might well be the complete answer to the problem of transport between cities
if only the frightful noise-factor could be overcome." Our comment at this stage might
well be "Hooray !" for our first purpose has been to help to bring about the recognition
that aircraft noise in and over cities does constitute a problem, this being the first essential
step towards getting something done about it. The task of incorporating engine-silencing
equipment in new helicopters at the design or early-development stage would be as
nothing compared with that of modifying existing fixed-wing transports (with their clean,
close-cowled power units) to incorporate silencers.
We wish that Mr. Hafner had expressed an opinion about noise when he, too, took
part in the discussion after Mr. Masefield's lecture, for his Bristol 173 may be the first
helicopter to operate over London and other cities. Presumably it is about twice as
noisy as the 171 (which has been described by one authority as acceptable) having two
engines, whence most of the noise comes. The Bristol Aeroplane company are apparendy
noise-conscious, for even if they did not intentionally build exterior quietness into their
magnificent Britannia and its Proteus turboprops, they lost no time in extolling this
virtue when it became a principal topic at Farnborough time.
According to reports, the sound of a ramjet helicopter—one with small units at the
blade-tips—is nothing short of shattering, and this alone may preclude the fitting of
this type of power to commercial helicopters. Fortunately, gas turbines appear to be
a more likely power source, and the indications are that in this application they will be
relatively quiet. It is our hope that the helicopter will not come to be regarded as one
more jarring noise thrust upon the long-suffering British public, but rather that it will
be a welcome and unobtrusive as well as convenient new means of transportation.