FP_2015_05_

116 FLYPAST May 2015

FROM THE WORKSHOP MOSQUITO PROTOTYPE

unique feature of W4050, we will

not hide the slats again but leave

them in working condition so

visitors can see them.

Back together

In February this year, the fuselage

was reunited with the newly restored

wing. This is not as straightforward

as it may sound. The chief concern

in handling a Mosquito fuselage,

especially a 75-year-old one

constructed using casein glue, is that

it may break at its weakest point, just

aft of the canopy.

A jury frame needed to be

fabricated and installed from

Bulkheads 2 to 4 to stop the

fuselage bending when it is

suspended from its lifting beam.

But the frame has to be removed

to allow the fuselage to be lowered

onto the wing.

Gerald Mears, de Havilland

Aircraft Museum chief engineer,

and I decided we needed to

ensure the risk of breaking the

fuselage had to be reduced to a

minimum – accomplished by the

design and manufacture of a pair

of ‘back braces’. The system had

been developed and tested for the

rebuild of the FB.VI in 2009 and

proved very successful.

The braces were mounted

on the lifting beam and, by

fine adjustment, the fuselage

could be ‘flexed’ to ensure there

were no compressive or tensile

forces acting on the jury frame.

This enabled safe removal

prior to lowering onto the wing.

The technique has also been

adopted by the Calgary Mosquito

restoration group in Canada with

our blessing.

With the fuselage attached to

the lifting beam by a pair of slings,

the back braces were fitted and

adjusted. The wing was positioned

directly underneath and aligned

with the fuselage pick-up points.

The jury frame was removed at

the last moment and the fuselage

lowered and secured to the wing

using the four main attachment

bolts. A trestle supported the

rear end of the fuselage. Then

the restored undercarriage was

refitted and W4050 was once

again supported on its own legs.

The restoration team’s intention

is to complete the Mosquito

prototype as much as possible,

ready for the 75th anniversary

on November 25, 2015. All the

work has been going on very close

to where W4050 was originally

assembled in 1940.

http://www.dehavillandmuseum.co.uk

W4050’s fl ying life

De Havilland fl ew W4050 from Hatfi eld

on initial trials up until February 19,

1941 when it was delivered to the

Aeroplane & Armament Experimental

Establishment (A&AEE) at Boscombe

Down. Five days later it broke its back

due to tailwheel castoring problems

encountered on Boscombe’s rough

surface.

The fuselage intended for the photo-

reconnaissance prototype, W4051, was transported to Boscombe Down and used

to replace W4050. Once back at Hatfi eld a strengthening strake was fi tted above

W4050’s rear fuselage access door and the engine nacelles were temporarily

fi tted with extensions to alleviate a tailplane buffeting problem.

Trials resumed at the A&AEE in March 1941 and, on the 18th, W4050 achieved

a top speed of 388mph in level fl ight at 22,000ft. Testing continued until May

when a heavy landing again split the fuselage on the port side, just aft of the

wing root. The damage was repaired by a team from de Havilland using large

plywood patches still visible today.

In mid-1941 a dummy gun turret was fi tted just aft of the cockpit canopy while

other trials included wing-mounted bombs. By October the prototype’s wing

was returned to Salisbury Hall to be modifi ed to accept two-speed, two-stage

supercharged Merlin 61s. In July 1942, W4050 achieved a top speed of 437mph in

level fl ight at 29,200ft.

In November 1942 the Merlin 61s were replaced with Merlin 70 series engines

• a Merlin 72 to port and a ’77 to starboard. The Mosquito fl ew with them
  for a further year, primarily testing exhaust stubs of differing materials and
  confi gurations.

The dummy gun turret used for tests at

Boscombe Down. Traces of where this chafed

on the canopy Perspex can still be seen today.

“The restoration team’s intention is to complete the Mosquito prototype as

much as possible, ready for the 75th anniversary on November 25, 2015”

Mechanism in the leading edge of the wing

for the Handley Page slats.

Slung, braced and jury rigged, the fuselage

is lowered ready for mating with the wings.

ALL IMAGES BY OR VIA AUTHOR

The only known photo of the maiden fl ight:

Geoffrey de Havilland Jr piloting the prototype

75 years ago.

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