88 http://www.aeroplanemonthly.com AEROPLANE JULY 2018been expressions of interest
from the military, including the
US Army.
He acknowledged that the
Rotodyne’s tip-jets were noisy
and insisted the company was
working to bring the noise
down to “an acceptable level”
— the aircraft appeared at
Farnborough in 1958 with new
noise ‘attenuators’ — but he
argued that aircraft operators
and heliport designers had a
role to play. Hislop thought the
ideal site for a heliport would
be the roof of a major railway
station. “Waterloo would be
nearly ideal since the station
itself is raised fairly high above
local street level”, he added.
Then the project received
something of a setback. The
Gyrodyne/Rotodyne had
started as a private venture but
from 1950 the government had
supported it as a military
research project. This funding
was withdrawn in 1957
although the Treasury did
agree to pick up the bills until
the end of the year. This left
Fairey and Napier (through its
parent company English
Electric) to meet the costs of
the prototype. Funding for the
production variant would be
subject to a different
arrangement.
Yet the Rotodyne’s prospects
appeared bright, with interest
from civil and military operators
around the world. BEA was
expected to place an order and
there was significant attention
from the USA. But the fact
remained that Fairey was
breaking fresh ground and this
was the cause of some
nervousness in Whitehall. Even
the Rotodyne Y, which was just
the prototype for the bigger Z,
was thought to be the world’s
biggest helicopter.
The prototype Rotodyne’s
fuselage, wings, rotor and main
undercarriage were built at
Fairey's manufacturing facility
at Hayes in west London while
the tail assembly was sub-
contracted to the company’s
Stockport, Greater Manchester
factory. These components
were trucked to White Waltham
for final assembly and testing.
In addition to the facilities
established there, a full-scale
static test rig for the Rotodyne’s
main rotor was assembled atHayes and transported to
A&AEE Boscombe Down to
support the programme.
This rig was essentially a
complete representation of the
Rotodyne’s rotor, powerplant
and control systems with all the
key components arranged in
their correct physical
relationship. Installed behind a
high earth bank to minimise
disturbance, it was capable of
running flight-standard
components and engines with
full validation. It remained in
continuous operation until
1962 to support all phases of
the main flight test
programme. Such rigs
subsequently became
commonplace but were
something of a novelty in the
late 1950s.
A one-sixth-scale model
without rotor was extensively
wind tunnel-tested for fixed-wing performance and a
smaller (1/15th-scale) model
with a powered rotor was used
to investigate vibration. In fact,
vibration coupling between the
articulated rotors and a
helicopter’s undercarriage
when the machine was on the
ground — known as ground
resonance — was a
phenomenon little understood
in the UK at the time, yet the
vibration could be totally
destructive.
Unlike most contemporary
helicopters, the Rotodyne was
designed with a retractable
undercarriage which meant
that special efforts were
required to overcome ground
resonance. The scale model
with its 6ft (1.85m)-diameter
rotor was used to conduct
dynamic testing of the
relationship between rotor and
undercarriage.Fairey’s chief helicopter test
pilot, Ron Gellatly, explained to
Flight readers in 1962, “The
alleviation of vibration was a
continuous job which took us
through a host of tests, some
with applied modifications and
some for gathering data only.
Eventually vibration was
reduced to one out of four
rotor blades and that was the
only frequency of note. The
only complaint we pilots could
make was of a propeller
frequency buzz on the
instrumentation boom.”
Airframe damping had
become so comprehensive that
vibration in the passenger
cabin had been brought within
what Gellatly called, “the BEA
comfort criteria”. All these
efforts to tune vibration out of
the structure meant that
enough information had been
gained, “to guarantee a lowvibration level on the
production aircraft”. Another
special rig enabled the
prototype to run on the ground
tethered by cables, the tension
of which could be varied. The
test team thus discovered two
resonance periods close to
maximum rotor speed
approaching take-off.
Meanwhile, construction of a
second Rotodyne was
authorised in the summer of- This was the definitive
production variant, known as
the Type Z. It would have been
20 per cent bigger with power
provided by a pair of Rolls-
Royce Tyne turboprops which
promised up to 5,000shp each,
a considerable advance on the
prototype’s Napier Elands.
An airliner variant for BEA
was intended to accommodate
up to 70 passengers in a
five-abreast lay-out, while a
military version could have
carried 60 troops or 40
stretcher cases. A rear loading
ramp with doors and a
‘beaver-tail’ arrangement
would have been offered as
standard on military examples
to give access to the whole
cabin and enable large loads
like vehicles to be carried.
Of particular significance to
those who still consider the big
rotorcraft to be one of Britain’s
greatest lost aviation
opportunities, Rotodyne
historian David Gibbings has
pointed out that the enlarged
Type Z’s cabin would have
been more than 50 per cent
longer and 20 per cent wider
than the Boeing Chinook’s. Its
all-up weight would have been
25 per cent greater.
Ron Gellatly felt few pilots
had been better prepared to fly
a new type than he was when
he stepped aboard the
Rotodyne to take it into the air
for the first time in November- He had become so
familiar with it through time
spent at the controls of the
‘old’ Jet Gyrodyne and 50
hours in the rig at Boscombe
Down that when he came to fly
the Rotodyne the only
‘unknown’ handling feature was
yaw control.
“In the Gyrodyne, under-
powered and elementary
though it was”, he wrote in The
Aeroplane during June 1958,
“we gained valuable air
experience in tip-jet behaviour
and particularly in transitional
handling from helicopter to
autorotative flight and back.
[Co-pilot Lt Cdr] John Morton
and I made 200 transitions
both ways in this old
aeroplane.”
The Rotodyne’s first flight
had originally been scheduled
for 1956, but despite the test
team’s best efforts it was
delayed until the following
year. Initial engine runs were
made in early 1957 and by the
summer a fully representative
run with both Napier Elands, all
four flight-standard rotor
blades and full instrumentation
had been accomplished on the
rig at Boscombe. The
completed aircraft’s first ground
run was made three-and-a-half
years after receipt of the first
working drawings.
A rendering of the Rotodyne first published in July 1953. VIA MAT THEW WILLISThe alleviation of vibration was a continuous
job... Eventually vibration was reduced to one out
of four rotor blades85-100_AM_Database_July18_cc C.indd 88 04/06/2018 16:57