Aeroplane – June 2018

A New Zealander by birth, Sqn Ldr W. R. ‘Ron’ Gellatly flew Ventura and Marauder light bombers during

World War Two before commanding No 293 Squadron on the Walrus and Warwick in the air-sea rescue

role. He graduated from the Empire Test Pilots’ School prior to joining Fairey, and stayed with Westland

when it bought Fairey out. KEYSTONE PICTURES/ALAMY

AEROPLANEAEROPLANE JULY 2018 JULY 2018 wwwww.aeroplanemonthly.comw.aeroplanemonthly.com 9797

Development

Technical Details

Flight Testing

Cancellation

Insights

Transitioning from vertical to

horizontal flight and vice versa

was normally achieved at

between 104 and 127mph. It

was a process largely invisible

to those on board. As speed

increased, tip-jet velocity was

reduced to produce a rotor

speed of around 140rpm while

maintaining a gentle nose-up

attitude. A single control lever

was operated to cut off tip-jet

fuel and declutch both

compressors. The clutch oil

drained for about 15 seconds,

over which period the pilot

applied the necessary

aerodynamic trim and change

of propeller power.

Reverting to helicopter

mode was essentially a

reversal of this procedure.

Speed was reduced to

127mph (200km/h) and the

auxiliary compressors were

engaged to provide a flow of

air to the tip-jets. Fuel and

ignition were selected to fire

them up. This process normally

took four to five seconds.

According to Ron Gellatly,

302 transitions were made

during the flight test

programme. They were

virtually incident-free. “The

inherent handling safety and

simplicity of these manoeuvres

was considered well proven”,

he reported. Writing in The

Aeroplane in June 1958, Fairey

senior project engineer D. M.

Davies said that the

Rotodyne’s cyclic and

collective pitch controls were

crisp and precise. Directional

control, provided at low speed

by the propellers, was “fully

adequate.”

Cruising in gyroplane

mode, the rotor was

established in autorotation

with the tip-jets shut down

and thrust for forward flight

provided wholly by the

propellers. Pitch and roll

control was now maintained

through cyclic pitch acting on

the rotor and conventional

aerodynamic controls. Yaw

control was maintained

through the rudders. In this

condition, total lift was evenly

distributed between the rotor

and the wings. Even during

the early flights it was found

that the pilot was able to

make extremely accurate

landings.

The layout of the pilots’

cabin and controls of the

Rotodyne Y followed normal

helicopter practice with the

captain sitting in the right-

hand seat. The proposed

production variant, the Z,

would not have differed from

the Y in this respect. In the

helicopter flight regime, the

controls and the way they

operated were intended to

follow conventional practice

except that directional control

would have been exercised by

the differential application of

Gellatly wrote of transitions, “The inherent

handling safety and simplicity of these

manoeuvres was considered well proven”

propeller pitch and the rudder

pedals.

On the Z the pilot would

have used a twist-grip

mounted on the collective

pitch control lever to control

tip-jet power by regulating the

RB176 gas generators’ output

and their fuel-to-air ratio. In

the gyroplane regime engine

power would have been

controlled through operation

of a throttle lever and

propeller pitch through a

propeller control unit.

INSIGHTS FAIREY ROTODYNE

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