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Subject: de Havilland DH.88
Date: 27 Jul 2017 06:25:55 -0700
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https://en.wikipedia.org/wiki/De_Havilland_DH.88
The de Havilland DH.88 Comet was a two-seat, twin-engined aircraft developed
specifically to participate in the 1934 England-Australia MacRobertson Air Race
from the United Kingdom to Australia.
Development of the DH.88 had been initiated at the behest of British aviation
pioneer Geoffrey de Havilland, along with the support of de Havilland's board,
being keen to garner prestige from producing the victorious aircraft as well as
to gain from the research involved in producing it. The DH.88 was designed by
Arthur Ernest Hagg around the specific requirements of the race; Hagg produced a
relatively innovative design of the era in the form of a cantilever monoplane,
complete with an enclosed cockpit, retractable undercarriage, landing flaps, and
variable-pitch propellers.
A total of three DH.88s were produced for the race, all for private owners at
development cycle, performing its maiden flight only six weeks prior to the
MacRobertson Air Race itself. Comet G-ACSS Grosvenor House emerged as the
winner. Two further examples were later built. The DH.88 went on to establish a
multitude of aviation records, both during the race and in its aftermath, as
well as participating in further races. Several examples were bought and
evaluated by national governments, typically as mail planes. Two DH.88s, G-ACSS
and G-ACSP, survived into preservation, while a number of full-scale replicas
have also been constructed.
The fuselage was built principally from plywood over spruce longerons, while the
upper and lower forward section were built up from spruce planking in order to
achieve the necessary compound curves. As with the wing, the strength of the
structure was dependent upon the skin. Fuel was carried in three tanks in the
fuselage, two over the wing in front of the cockpit and the third, of only 20
gal capacity, behind it; this could be used to alter the aircraft's trim. The
pilot and navigator were seated in tandem in a cockpit set aft of the wing;
while dual flight controls were fitted, only one set of flight instruments were
installed.
The engines were uprated versions of de Havilland's newly developed Gipsy Six,
race-tuned for optimum performance with a higher compression ratio. The DH.88
could maintain altitude up to 4,000 feet (1,200 m) on one engine.
Hamilton-Standard hydromatic variable-pitch propellers were fitted initially.
The main undercarriage retracted backwards into the engine nacelles and was
operated manually, requiring 14 turns of a large handwheel located on the right
hand side of the cockpit.
MacRobertson Race
All three Comets made it to the start of the race at RAF Mildenhall, a newly
established air base in Suffolk. G-ACSP was painted black and named Black Magic,
G-ACSR green and unnamed, G-ACSS red and named Grosvenor House. The three
distinctively coloured aircraft took their places among 17 other entrants, which
ranged from new high-speed Douglas DC-2 and Boeing 247 airliners to old Fairey
Fox biplanes.
A. O. Edwards named his red Comet G-ACSS after the Grosvenor House Hotel which
he managed. He engaged C. W. A. Scott and Tom Campbell Black to fly it in the
race.
Having landed at Kirkuk to refuel, they arrived at Baghdad after the Mollisons
had left but took off again after a mere half-an-hour turnaround. This time it
was Scott and Campbell Black who missed out Karachi and flew non-stop to
the lead from the troubled Mollisons. Despite a severe storm over the Bay of
Bengal, in which both pilots had to wrestle with the controls together, they
reached Singapore safely, eight hours ahead of the DC-2.
They took off for Darwin, losing power in the port engine over the Timor Sea
when the oil pressure dropped to zero, but struggled on to Darwin. While
mechanics were working on the engine its designer, Frank Halford, saw a news
placard back in England and telephoned through to Darwin. Talking it over he
concluded that, despite the warning indicator, they should be able to fly on at
reduced power. Despite this their lead was now unassailable and after the final
mandatory stop and more engine work at Charleville they flew on to cross the
finish line at Flemington Racecourse at 3.33 p.m. (local time) on 23 October.
Their official time was 71 hours 18 seconds.
Specifications
General characteristics
Crew: two
Length: 29 ft 0 in (8.84 m)
Wingspan: 44 ft 0 in (13.41 m)
Height: 10 ft 0 (3.05 m)
Wing area: 212.5 sq ft (19.75 m2)
Airfoil: RAF 34
Empty weight: 2,930 lb (1,332 kg)
Loaded weight: 5,550 lb (2,523 kg)
engine, 230 hp (172 kW) each
Performance
Maximum speed: 237 mph (206 kn, 382 km/h)
Cruise speed: 220 mph (191 kn, 354 km/h)
Stall speed: 74 mph (64 kn, 119 km/h)
Range: 2,925 mi (2,541 nmi, 4,710 km)
Service ceiling: 19,000 ft (5,790 m)
Rate of climb: 900 ft/min (4.6 m/s)
*
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