Comet 3 – the hybrid prototype

Mk.3 in BOAC colours – setting off on a world tour


At the Society of British Aircraft Constructors [SBAC] show at Farnborough in September 1952, while the first Comet prototype was demonstrating Sprite rocket assisted take-offs, a new version of the Comet – the Mk.3 – was proposed by de Havilland as the next logical step in Comet evolution. The project was shown to the world airlines.

The intention was to offer an aeroplane with greater passenger capacity and able to operate over longer distances – seating for either 58 (all first class) or 76 (tourist) in a further lengthened fuselage – now 111’ 6″. The specification called for an increased fuel capacity – now 8308 Imp. gallons – feeding four new Avon RA16s rated at Range was to be 2700 miles or better.

Airline Interest

First flight was scheduled for 1954 and, provided there was sufficient interest from the operators, production to begin during 1956.

Initial airline interest was promising and BOAC were the first operators to show definite interest by ordering five.

The Corporation immediately began a program whereby ‘shadow’ flights were undertaken by the Operations Room staff. The objective was to proceed as if a Mk.3 was operating a scheduled flight from London Airport to New York, via Gander. Each morning at 8.30 hours weather reports were obtained for the North Atlantic route. They were studied and alternates planned. The ‘selected’ Comet Captain would then decide on the best route from London to New York with departure being set for 10.00 am. Departure was signaled to stations along the route. Updated Met. reports would be received for the area and, if necessary, changes to the flight plan made. The same procedure would be undertaken for the ‘return’ flight.

In planning these ‘shadow’ flights it was assumed that the Comet was operating at it’s maximum AUW (all up weight). Fuel was calculated based on this assumption, suitably corrected for the reported weather conditions. The weather was of course an ‘unpredictable factor’ .

However by taking regular ‘flights’ the Corporation was able to learn a great deal about how regular Comet operations could be operated on this demanding route and what fuel reserves would be necessary. Early indications were that the Comet would make the return trip within 24 hours having spent a number of hours ‘at rest’ at Idlewild.

Other carriers to express an interest included: Air India wanted two and Pan American wanted 3 with options.

KLMs response to the Comet was typical. As a key player in Europe they had influence. The key factor was economics. Would there be an adequate return on investment once the high initial cost of the aircraft expended? KLM judged not based on analysis of Comet 1 and 1A on their particular routes. The Comet 2 also was not considered for the same reasons.

Of course there were other factors to be considered too which were unique to the Comet – for example, it was faster, quieter, smoother and had great passenger appeal. This would in the normal course of events allow the Comet to attract the more affluent passenger – those that were prepared to pay a premium.

BOAC had got the Mk.1 at a bargain price by way of them being a ‘partner’ in development as well as being the ‘launch’ customer. But other airlines were going to have to pay the going rate and so were having to take a more realistic approach to the Comet’s potential return. Nevertheless KLM did express considerable interest in the Mk.3. Indications for de Havilland were, therefore, that if they could successfully increase the Comets range and payload they would be on to a winner. The Mk. 3 would be a marketable aeroplane.


Change of plans

That was in 1952. But following the accidents, the grounding of Comet and the subsequent delay while the Court of Inquiry sat, de Havilland plans changed greatly.

Not surprisingly most existing Comet orders were either cancelled or suspended while the results of the Inquiry were awaited. In fact, as the Inquiry drew to a close, de Havilland were forced to stress publicly that any delay in releasing it’s findings could be very detrimental to the Company and to it’s plans for the future. They requested an interim report so that the findings, none of which were in dispute, could be acted upon immediately.

Comet 3 roll out

The prototype Comet 3 (c/n 106100) was rolled out early in May 1954 with much to be done before the maiden flight. Registered G-ANLO the maiden flight was from Hatfield on 19th July – just four days after Boeing first flew the 707 Stratotanker (for-runner of the 707 passenger jet).

The flight lasted 1hr 25 min. crewed by John Cunningham (Chief Test Pilot); Peter Buggé and E Brackston-Brown as flight engineer, Tony Fairbrother, aerodynamics dept. was flight observer with J Marshall an instrument engineer.

Power came from four RA16 turbo-jets each delivering 9000 (These were later changed to Avon 502’s (RA26) engines rated at 10,000 each). In this guise the Mk.3 could not be fully pressurized.

General specification for the Comet 3 was thus: Span at 107’ 9.7″, length now 111’ 6″ and tail height 28’ 6″. Wing area was 2121 sq.ft and seating provided for between 58 and 78 passengers depending upon the class mix adopted. The range was quoted as 2700 miles at a cruising speed of 500mph at around 40,000ft. Avon 502s were fed from integral wing tanks and centre section bags with a total capacity of 8360 Imp. gallons.

Mk.3 cancelled

After the enforced delay of over a year it became clear that the Comet 3, as first proposed, could not be marketed. Two airframes were in fact laid down but only one (06100) flew. 06101’s fuselage and wings were used for structural testing at Hatfield.


The ‘New’ Comet

BOAC remained faithful to the enlarged Comet idea and signalled to de Havilland their firm intention to order the larger aeroplane. But they now wanted a new further improved version – dubbed the New Comet – which they knew de Havilland had been working on for some time.

In February 1955 they placed and order for 19 Mk. 4s. which, although identical in size to the Mk.3, would be structurally completely different – a completely new aeroplane in fact.

Test bed.

The ANLO turned out to be a most, some would say the most, remarkable and versatile aeroplane of the Comet family – it was certainly one of the most interesting variant. Once it was decided how extensive the modifications and improvements which were to be incorporated in a Mk.4 were to be it was clear that, apart from size, there would be little in common with the Mk.3.

From the outset it was decided that various new systems and equipment were to be installed in the Mk.4. Everything had, of course, to be extensively tested. ANLO now had a new role as a flying test-bed.

So the task of the Mk.3 was two-fold:

  • to provide a vehicle for Mk.4 development (and in the process speed up the Certification programme) and

  • secondly, in parallel with this work, to use the aeroplane as a promotional tool.

The enormous costs of introducing the Comet 4 had to be offset by sales and the Comet 3 would be instrumental in maintaining, and generating, airline interest in the new aeroplane during the three years that would elapse before the Mk.4 flew.

World Tour

Nothing illustrates ANLO’s public relations potential more than a tour which departed in December 1955 when John Cunningham and Peter Buggé set off from Hatfield on a round-the-world trip. The objective of the trip was to make a practical assessment of the Mk.4s commercial capabilities.

By the time ANLO landed back at London Airport on December 28th over 30,000 miles had been covered in just 67hrs flying time. They had flown 3250 miles from Montreal in 6hrs 18 min. at an average speed of 515 mph.

The trip was a huge success but it was not an easy one for the crew. The Mk.3 pressurization system was described by one engineer as a ‘lash up’. The structure was basically Mk.2 so ANLO could only be pressurized to 4 psi. This gave a cabin pressure equivalent to 8,000ft even when cruising at 20,000ft. This was the maximum altitude used for demonstration flights but, en-route between destinations, the Comet cruised at about 35,000ft (crew on oxygen) rising gradually with cruise-climb to 40-42,000ft. and on the longest stage ANLO touched 44,000ft.

The Mk.3 proved to be extremely reliable – there was only one problem on the whole trip -the detachment of an extension jet pipe from the starboard inner engine. This happened a few minutes after leaving Montreal on December 22nd. It was soon repaired. Reliability was outstanding.

Flying the flag, as it were, ANLO had made the trip in BOAC colours and, in addition to de Havilland staff, BOAC had seconded Capt. Peter Cane who acted as a crew member for the tour. Again, in accordance with making a truly practical assessment, the Comet was flown strictly in accordance with normal jetliner procedures.

A great deal of PR. value lay in these tours. At many stops en-route demonstration flights were laid on. At Sydney, Melbourne, Auckland, Honolulu, Vancouver, Montreal an average of fifty people were carried aloft. The Comet was demonstrated to many representatives of the world’s Airlines: Australian National Airways, Trans-Australia Airways, Qantas, Canadian Pacific Air Lines, Tasmanian Empire Airways, Trans-Canada Airlines all expressed interest. Feedback indicated operators were particularly impressed by the airport behaviour of the Comet especially its short take-off and landing – characteristics that were always a Comet strong point.

On this very successful tour numerous records were set and the Mk.3 became the first jet to cross the Pacific and to circumnavigate the world.

More Records

The Mk.3 was used to help satisfy those concerned (usually the Airport Authorities) about jet airliner noise.

In November 1957 ANLO was subjected to noise measurement tests at Hatfield for the Port of New York Authority (whose permission was required for access to Idlewild Airport).

At about this time it was discovered that Stockholm’s airport authority had measured the noise of the Mk.3 while it was on a promotional visit. These measurements were in fact taken before new noise suppressers had been fitted to the engines, nevertheless they concluded that the Comet made no more noise than the latest piston or turboprop airliners.

G-ANLO certainly did not have an easy life – well over 900 stalls were made evaluating Mk.4 and 4B stall characteristics – some of these being very severe. No measurable damage was sustained.

In June ‘56 ANLO was flown to Toulouse from Hatfield – 564 miles in 80 minutes – to demonstrate the Comet to J. H. Carmichael, President of Capital Airlines and five of his colleagues. (Incidentally while in France John Cunningham took the opportunity to fly the Caravelle – the Comets great European rival). Also on this trip were representatives of BOAC, BEA, Trans-Australian Airlines, Rolls-Royce and the Ministry of Supply.


G-ANLO Mk.3B in BEA colours


Once certification for the 4 was completed the 3 was progressively modified to evaluate new developments and to test other pre-production modifications and refinements. The 3 was modified to 3B specification for Comet 4B evaluation and for Certification work. The 3B prototype first flew on 21st August 1958 with Messrs. Cunningham and Buggé at the controls. The clipped winged 3B was displayed at the SBAC show, Farnborough in September ’58 where it was shown in BEA colours and named ‘R.M.A. William Brooks’.

Another ‘first’ was the use of thrust-reversers which operated on the outer two engines – Avon 525s. They were flight tested for the first time on 26th April 1958 and immediately gave satisfactory results. They became ‘standard optional equipment’ on all Comet 4Bs and later Comets. Noise suppression, too, was becoming increasingly important to airline operators and Rolls-Royce developed their Jet-noise suppressors (the Greatrex -type) for the Mk.3. They too became standard on the Mk.4

For BEA the Mk.3B fulfilled a similar role as the Comet 2E had done for BOAC – speeding up crew training and route proving.

BEA crews used ANLO to gain in-flight experience after completion of ground based courses with de Havilland and Rolls-Royce. BEA Flight Manager, Capt. G. T. Greenhalgh, described his first impressions of the Mk.3. He said,

“when the throttles were opened nothing much seemed to happen for what seem like an age then, as the aircraft reached 65 knots, it was like getting a ‘hefty kick in the pants’. V1, Vr and V2 came up rapidly and at 125 Knots pulling back on the ‘stick’ the Comet climbed. Keeping the climbing speed to 150 Knots the ground disappeared rapidly and the aeroplane appeared to be standing on it’s end – almost in an instant the wheels were up and the ASI was passing 200 Knots”.

Experience was gained doing circuits and bumps, stalls and initiation into high-speed Mach. runs all with limited pressurization and using oxygen masks when not on circuit.


G-ANLO in old BEA colours

Blind Landing Experimental Unit – BLEU

G-ANLO also found itself in the hands of the Blind Landing Experimental Unit (registered as XP915) based at Bedford and, later still, with the RAE, Farnborough. Finally it was transferred to Woodford, Cheshire for use as a Nimrod test-rig.

All in all G-ANLO had a long and distinguished career. Some unusual demands were made upon it, for example, it was used to test the efficiency of urea formaldehyde foam in its ability to arrest aircraft on overrun. The foam was being tested by the Naval Air Department at Bedford who had been asked to assess its worth. The foam was to be spread by spraying onto the runway in the event of an emergency and the idea was that it would resist the rotation of the aircraft wheels – causing them to compress the foam, and in doing so, to dissipate energy and slow the aeroplane. The foam was not adopted.

Finally ANLO suffered the ignominy of having its tail damaged when the top of its fin and rudder were knocked off by a Trident 3 while awaiting take-off on January 19th 1971. However it survived to fly again!


Comet 2

Copyright © David Young 2021 

Comet 4