de Havilland DH.88

DH.88 Comet
G-ACSS Grosvenor House during a display at the Shuttleworth Collection in September 2014
Role	Racing aircraft
Manufacturer	de Havilland
Designer	Arthur Ernest Hagg
First flight	1934
Status	Two in restoration
Number built	5

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 for the era in the form of a stressed-skin 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 the discounted price of £5,000 per aircraft. The aircraft underwent a rapid 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.

Background

Mildenhall

Baghdad

Allahabad

Singapore

Darwin

Charleville

Melbourne

MacRobertson Air Race start, finish and compulsory stops. Aside from stopping at these places, competitors chose their own route; they were permitted to stop elsewhere

During 1933, the MacRobertson Air Race, a long distance multi-stage journey from the United Kingdom to Australia, was being planned for October 1934, to celebrate the 100th anniversary of the Australian State of Victoria. Sponsored by Macpherson Robertson, an Australian confectionary manufacturer, the race would be flown in stages from a new aerodrome at Mildenhall to Melbourne.^[1][2][3]

Despite a number of previous air racing successes by British companies, a new generation of monoplane airliners that were then being developed in America had no viable rival in Britain at the time. Geoffrey de Havilland, a British aviation pioneer and founder of aircraft manufacturing firm de Havilland, was determined that the MacRobertson Air Race ought to be won by a British aircraft.^[4] While it was recognised that there would be no prospect of recouping the full investment in developing a new design, the De Havilland board decided to subsidise the project; it was hoped that the endeavor would serve to both enhance the company's prestige and also provide benefits that would result from the research involved.^[5]

Accordingly, it was announced in January 1934 that if three orders could be obtained by 28 February, a specialist racer to be named the Comet would be built and sold for £5,000 each, that would be capable of achieving a guaranteed speed of 200 miles per hour (320 km/h).^[6] The prescribed price was projected as being half of the incurred cost of manufacture. Three orders were indeed received by the deadline; one from Jim Mollison, to be flown by him and his wife Amy (better known as Amy Johnson), one from A. O. Edwards, a hotel manager, and the last from racing motorist Bernard Rubin.^[4]

Design and development

Although designed around the requirements for the MacRobertson air race, the DH.88 was not classed as a racer, owing to the unusual requirements of the England-to-Australia race. De Havilland paid special attention to the non-stop range between the widely spaced official stages. They initially intended to produce a twin-engined two-seat development of the DH.71 experimental monoplane. However it would have insufficient performance so the designer, Arthur Ernest Hagg, turned to a more innovative design, this being a new cantilever monoplane with enclosed cockpit, retractable undercarriage and flaps. In order to achieve take-off at a reasonable speed and with high all-up weight, combined with a satisfactory high-speed cruise, it would be necessary to fit variable-pitch propellers.^[7]

The resulting design had a low, tapered high aspect ratio wing and was powered by two Gipsy Six R engines, a specially-tuned version of the new Gipsy Six. Construction was almost entirely of wood, metal being confined to high-stress components such as the engine bearers and undercarriage, and to complex curved fairings such as the engine cowlings and wing root fairings. The sheet metal parts were composed of a magnesium-aluminium alloy. Manually operated trailing edge split-flaps were fitted below the inboard wing sections and lower fuselage, while the Frise ailerons were mass balanced by lead strips within the wing's leading edges. Rudder and elevators had horn mass balances. In order to prove the wing design a half-scale model wing was built and tested to destruction.

Aerodynamic efficiency was the design priority and it was therefore decided to use a thin wing of RAF34 section. This was not thick enough to contain spars of sufficient depth to carry the flight loads and so the wing skin would have to carry most of the loads. However, the complex curves required for aerodynamic efficiency could not be manufactured using plywood. A construction technique previously used for building lifeboats was adapted. The majority of the wing was covered using two layers of 2 inch (50mm) wide spruce planking laid diagonally across the wing, with the outer layer laid crosswise over the other. These strips were of variable thickness, according to the loads they carried, reducing over the span of the wing from 0.5 in (12.5mm) at the root to 0.14in (3.5mm) towards the tips. It was built as a single assembly around three box-spars located at 21, 40 and 65 percent chord: there was an intermediate spruce stringer between each pair of spars to prevent buckling. The ribs were made of birch ply and spruce. The outboard 6 ft (1.5m) were skinned with various thicknesses of ply because of the difficulty of machining spruce planking to less than 0.07in thickness. The leading edge, forward of the front spar, was also ply covered. The centre section was reinforced with two additional layers of 0.07 spruce.^[8] This method of construction had been made possible only by the recent development of high-strength synthetic bonding resins and its success took many in the industry by surprise.^[9]

Cockpit of G-ACSS 'Grosvenor House' (2010). This differs considerably from the original state.

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.^[4] 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.

The challenging production schedule meant that flight tests of the DH.88 commenced just six weeks prior to the start of the race. During testing, the propeller blade roots were found to interfere unacceptably with the airflow into the engine. Instead, a two-position variable pitch type, manufactured by French manufacturer Ratier, was substituted.^[10] These blades were manually set to fine pitch before takeoff using a bicycle pump, and in flight they were repositioned automatically to coarse (high-speed) pitch by a pressure sensor. A drawback was that the propellers could not be reset to fine pitch except on the ground.^[10] Other changes included the installation of a large landing light fitted in the nose and a revised, higher profile to the cockpit to give the pilot marginally less restricted visibility.

Operational history

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.

G-ACSP Black Magic

Jim Mollison and his wife Amy (born Amy Johnson) were both famous aviators in their own right and had earned the nickname "the flying sweethearts". They were favourites to win the race in their own G-ACSP Black Magic and were the first entrants to take off.

At 6.30 a.m. on 20 October 1934, they began a non-stop leg to the first compulsory staging point at Baghdad, the only crew who managed to do so without stopping to refuel. Arriving next at Karachi they set a new England-India record. Problems began when their landing gear failed to retract and, after returning to Karachi for repairs, they were again delayed by difficulties with navigating at night. Worse problems followed when they made an unscheduled refuelling stop at Jabalpur but found no aviation fuel. Running instead on unsuitable fuel provided by the local bus company, a piston seized and an oil line ruptured. They flew on to Allahabad but, needing completely new engines, were forced to retire.

G-ACSS Grosvenor House

"Grosvenor House" in Martin Place, Sydney, Australia, 12 November 1934.

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 Allahabad. There they were told they were the first to arrive – they had taken 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.

G-ACSR

The third Comet, G-ACSR had been painted a racing green by Bernard Rubin who was a successful motor race driver. He had intended to fly it himself but had to pull out at the last minute due to ill health and instead engaged Owen Cathcart Jones and Ken Waller.

On reaching Baghdad, they overshot it in the dark, landing by a village when they ran low on fuel. Leaving at first light, they just made it to Baghdad on empty tanks. On taking off again they found that they had a serious oil leak and had to return for repairs. More trouble was encountered on the Darwin leg so they landed at Batavia, where engineers employed by KLM, who had entered the DC-2, made repairs for them. They were the fourth aircraft to reach Melbourne, in a time of 108 h 13 min 45 s. Cathcart Jones and Waller promptly collected film of the Australian stages of the race and set off the next day to carry it back to Britain. Their return time of 13½ days set a new record.

After the race

The race winner (formerly G-ACSS) wearing RAF livery in 1936

G-ACSS in a later incarnation as The Orphan, preparing for an air race in 1937 – Flight Photo.

Grosvenor House was dismantled and shipped back to England. It was later bought by the Air Ministry, given the military serial K5085, painted silver overall with RAF markings and flown to Martlesham Heath for evaluation. It made several flights before being written off in a heavy landing and sold for scrap. It was subsequently sold on, rebuilt and fitted with Gypsy Six series II engines and a castoring tailwheel. In this form it made several race and record attempts under various names. It claimed fourth place in the 1937 Istres-Damascus-Paris race and later the same year lowered the out-and-home record to the Cape to 15 days 17 hours. In March 1938, Arthur Edmond Clouston and Victor Anthony Ricketts made a return trip to New Zealand covering 26,450 mi (42,570 km) in 10 days 21 hours 22 minutes.^[11][12]

In G-ACSR, the day after they finished the race Cathcare and Waller took off on the return journey. Suffering engine trouble, at Allahabad they found the Mollisons still there and were generously given two pistons from Black Magic to allow them to continue. They set a new round-trip record of 13 days, 6 hours and 43 minutes. That December, G-ACSR was named Reine Astrid and flew the Christmas mail from Brussels to Leopoldville in the Belgian Congo.^[4] It was then modified and sold to the French government as F-ANPY, setting a Croydon-Le Bourget record on 5 July 1935. It subsequently made Paris–Casablanca and Paris—Algiers high-speed proving flights. Formerly believed destroyed alongside F-ANPZ (see below), F-ANPY was last seen in an unflyable condition at Étampes in France in 1940.^[13]

Black Magic was sold to Portugal for a projected flight from Lisbon to Rio de Janeiro. Re-registered CS-AAJ and renamed Salazar it was damaged on its attempted takeoff for the Atlantic crossing and was returned for repair. On its return it made a record flight from London to Lisbon, setting a time of 5 hr, 17 min in July 1937, but failed to make any further significant flights.

Other Comets

Following the French government's acquisition of F-ANPY (see above), they ordered a fourth Comet, F-ANPZ, with a mail compartment in the nose. It was later taken on charge by the French Air Force before being destroyed in a hangar fire at Istres in France in June 1940.^[13]

The fifth and last Comet, registered G-ADEF and named Boomerang, was built for Cyril Nicholson. It was piloted by Tom Campbell Black and J. C. McArthur in an attempt on the London-Cape Town record. It reached Cairo in a record 11 hr, 18 min, but the next leg of the journey was cut short due to oil trouble while in flight over the Sudan. G-ADEF crashed and was lost on 22 September 1935, the crew escaping by parachute.^[4]

DH.88 Comet record flights

The DH.88 Comets set many record times for long-distance flights during the 1930s.

Surviving aircraft

G-ACSS Grosvenor House in 2011

G-ACSS was requisitioned for the RAF once again in 1943 but soon passed on to de Havilland. Restored for static display as Grosvenor House, it was put on show for the 1951 Festival of Britain. The Shuttleworth Collection at Old Warden acquired it in 1965 and then in 1972 re-registered it under its original identity for restoration to flying condition, finally achieved in 1987.

G-ACSP Black Magic, under restoration in 2016

CS-AAJ Salazar was rediscovered in Portugal after being lost for more than 40 years. It was brought back to the UK and re-registered once again as G-ACSP. It is currently under restoration to flying condition, in its original livery as Black Magic, by the Comet Racer Project Group at the Amy Johnson Comet Restoration Centre, Derby Airfield.^[16]

Airworthy reproductions and replicas

N88XD is a full-scale flying replica Comet. Built in 1993 for Thomas W. Wathen of Santa Barbara, CA by Bill Turner of Repeat Aircraft at Flabob Airport in Rubidoux, California, it wears the livery of G-ACSS Grosvenor House.

A replica, originally started by George Lemay in Canada, was acquired by the Croydon Aircraft Company based at Old Mandeville Airfield, near Gore, New Zealand, where it is currently still under construction.

G-RCSR is a reproduction DH.88 Comet based on the original construction drawings, being built by Ken Fern in parallel with the restoration of Black Magic at Derby.^[17]

Operators

 France

• Armée de l'Air

 Portugal

• Portuguese Government

 United Kingdom

• Air Ministry (for evaluation)
• Shuttleworth Collection

Specifications

Preserved at the Shuttleworth Collection, one of the original race-tuned Gipsy Six R engines fitted to the winning DH.88 Comet Grosvenor House (background) for the MacRobertson Air Race in 1934.

Data from De Havilland Aircraft since 1909^[18]

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^[19]
• Empty weight: 2,930 lb (1,332 kg)
• Loaded weight: 5,550 lb (2,523 kg)
• Powerplant: 2 × de Havilland Gipsy Six R six-cylinder air-cooled inverted inline 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) ^[20]
• 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)

In popular culture

A cigarette card featuring G-ACSS Grosvenor House

In the film Planes from DisneyToon Studios, the character Bulldog is based on the DH.88 Comet and is voiced by the comedian and actor John Cleese.^[21]

In the Dutch aviation comic series "January Jones" the title heroine, a U.S. racing pilot in the 1930s, flies her own a DH.88 Comet, usually indicated as (De Havilland) Comet. Its red-with-white colour and #43 resemble Grosvenor House. The series has been published in Dutch, French, Danish, Norwegian, Finnish, Portuguese, Catalan, Spanish and German.

The comic strip "The Phantom" began a storyline on 2 July 2016 which featured a DH.88 Comet, describing it as one of the original race machines, restored after a hangar fire in France in June 1940.

See also

Aircraft of comparable role, configuration and era

• Caudron Typhon
• Grigorovich E-2

Other

• Half a World Away or The Great Air Race (TV two-part series)

References

Notes

Bibliography

External links

Wikimedia Commons has media related to De Havilland DH 88 Comet.

• Comet Racer Project Group
• The Burberry Comet Racer Project, Sywell Aerodrome.
• Sound recording of G-ACSS, Aircraft Sound Recordings.