Design and development De Havilland DH.88 Comet

cockpit of g-acss grosvenor house (2010). differs considerably original state.

the fuselage built principally plywood on spruce longerons, while upper , lower forward section built spruce planking in order achieve necessary compound curves. wing, strength of structure dependent upon skin. fuel carried in 3 tanks in fuselage, 2 on wing in front of cockpit , third, of 20 gal capacity, behind it; used alter aircraft s trim. pilot , navigator seated in tandem in cockpit set aft of wing; while dual flight controls fitted, 1 set of flight instruments installed.

the engines uprated versions of de havilland s newly developed gipsy six, race-tuned optimum performance higher compression ratio. dh.88 maintain altitude 4,000 feet (1,200 m) on 1 engine. hamilton-standard hydromatic variable-pitch propellers fitted initially. main undercarriage retracted backwards engine nacelles , operated manually, requiring 14 turns of large handwheel located on right hand side of cockpit.

the challenging production schedule meant flight tests of dh.88 commenced 6 weeks prior start of race. during testing, propeller blade roots found interfere unacceptably airflow engine. instead, two-position variable pitch type, manufactured french manufacturer ratier, substituted. these blades manually set fine pitch before takeoff using bicycle pump, , in flight repositioned automatically coarse (high-speed) pitch pressure sensor. drawback propellers not reset fine pitch except on ground. other changes included installation of large landing light fitted in nose , revised, higher profile cockpit give pilot marginally less restricted visibility.