DeHavilland DH88 Comet

by Clive Paling

I first became interested in this aircraft several years ago, when my daughter bought the 1/72 Airfix kit, from Snowy Mountains, during the post Expo clear up (do I get a discount because it saves you taking it home?).  She had intentions of entering the following Expo with it.  However by the time Expo had come and gone, with only the wings assembled, I duly inherited it.  After sitting in the cupboard for a few months it finally emerged for construction.  It was put together more or less OOB except for some scratchbuilt cockpit detailing (pure invention due to lack of references) and the end result was quite pleasing - it's a nice little plane.

  A little later I came across "The de Havilland Aircraft Company" by Maurice  Allward (1996) in the TTG library.  A very interesting book and of course it contains more info on the Comet, including the fact that there was a black one with gold markings (must build).  Anyway by now I was getting more interested in this plane so I thought I would give a brief history.

  In January 1934 the de Havilland  directors were discussing the hopeless position of British aicraft in the upcoming Melbourne Centenary Air Race.  A trophy and prizes totaling 15,000 were on offer, but the technically advanced American planes looked set to sweep the field.  With only 10 months to go before the start of the race de Havillands decided to design and build a long range racing airplane to enter the speed section of the race.  A price of 5,000 was set for each aircraft provided orders were placed by the end of February 1934.  No technical details would be divulged, even to the buyers, but a speed in excess of 200mph was guaranteed.

  Within the time scale orders were received for three Comet racers, allowing the design and building program to get under way.  The design was a low winged monoplane of minimal frontal area and clean lines.  Power came from two de Havilland Gypsy Six engines uprated to 225 hp giving a cruising speed of 225mph over 2,900 miles. The two crew were housed in a tandem cockpit well down the fuselage to reduce drag.  Because the wing was so thin all fuel tanks were also housed in the fuselage.  The wooden structure was covered with wooden stressed skin, a technique later used on the Mosquito.  The one piece cantilever wing had the engines cleanly cowled in underslung nacelles which also housed the undercarriage.

  One of the hardest technical problems to overcome was the fitting of controllable pitch airscrews to such a small aircraft.   The American Hamilton Standard  variable pitch propeller was the obvious choice, but time was too short to overcome the technical problems.   An alternative was found in France.  Designed by Ratier, its smaller size was more suited to the Gypsy Six engines.  The propeller was set to fine pitch by pumping on the ground with a bicycle pump.  After takeoff, when reasonable speed (150mph) had been reached, the air pressure on a disc in front of the spinner, pushed it aft and changed the blades to coarse pitch.  Once changed the prop had to remain in coarse pitch until after landing, which didn't make landing any easier.  Also it was impossible to synchronize the discs so that they changed pitch together.

  The three Comet racers were built in great secrecy at the old Stag Lane factory despite continual removal of works machinery to equip the growing Hatfield factory.  A remarkably short period of 8 months had elapsed from conception to first flight on 8th September, just six weeks before the start of the race. To avoid too many problems the Ratier propellers were not fitted for the early tests.  On the maiden flight the pilot forgot which way to wind the manual under carriage handle to lower the wheels, as no indicator was fitted.  As no radio was fitted he watched the reactions of the onlookers while making his landing approach.  Much frantic waving caused him to make another circuit, lower the undercarriage and land safely.

  Although it was one of the lowest powered aircraft entered for the speed section of the race, it was the fasted British civil aircraft ever produced, except for the Schneider Trophy contestants.  During official tests the first aircraft reached 235mph at 1,000 ft and 225mph at 10,000 ft. 

  The first purchase announced was for the Managing Director of London's, Grosvenor House Hotel.  It was finished in red with white markings and named Grosvenor House.  It was to be flown by T, Campbell Black and C.W.A. Scott.  Jim and Amy (Johnson) Mollison were to fly an all black craft with gold markings (Black Magic) and the third, in dark green and white, was to be flown by Cathcart Jones and Waller.

  All entries were to arrive at Mildenhall by 4:30pm on Sunday 14th October, but that as they say is another story..............More next month.

  Many thanks to Peter Murrie, who has kept me supplied with copies of any articles he comes across concerning this plane.

  Needless to say I still want to build 'Black Magic'. So if anyone has the old Frog kit (or even the Black Magic decals) which they would be prepared to part with (at a realistic price), then please get in touch with me at club meetings, through Sapmail or at the Expo. 

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