De Havilland DH 106 Comet / Nimrod

Comet 4C

The Comet resulted from the wartime Brabazon Committee's recommendations for the Type IV North Atlantic turbojet mail plane, which led to numerous studies including a 20-passenger aircraft with three rear-mounted Goblin engines.
The final design emerged as an orthodox low-wing monoplane with 20 degree leading-edge sweep-back and four 19.8kN de Havilland Ghost centrifugal-flow turbojets buried in the wing roots. Initial accommodation was for 36 passengers in two cabins, pressurised to provide internal pressure equivalent to 2,438m when flying at 12,192m. Cruising speed was about 788km/h.

The prototype Comet made its first flight on 27 July 1949.

BOAC received a fleet of ten Comet Is and on 2 May 1952 inaugurated the first passenger services to be operated by turbojet aircraft - on the London-Johannesburg route, covering the 10,821km in 23 hr 34 min. Comets were subsequently introduced on a number of routes, bringing drastic cuts in journey time: such as the reduction from 86 to 33 1/4 hours between London and Tokyo. Air France and UAT soon began Comet services and there were a number of airline orders for Comet 1s when one broke up near Calcutta exactly a year after its introduction; in January and April 1954 two more suffered inflight structural failure, resulting in the type being withdrawn.

In October 1952, a Comet broke up in flight near Calcutta. Modifications were made, but when, on April 8, 1954, the fifth Comet accident oc-curred, all Comets were withdrawn from service and production was halted. Salvage and careful investigations showed that fatigue failure of the cabin was the cause of the crashes, and the fuselage was redesigned. Painstaking detective work by scientists and engineers had established that the Comet ls had suffered metal fatigue, causing explosive decompression of the pressurized fuselage.

THE COMET SITUATION
Flight 7 May 1954

A great deal of structural knowledge was gained through the accidents of four of the original nine Comet I models. This knowledge was later tested on the model 3 and applied to the model 4.

The Avon-powered Comet 2s on order for BOAC were strengthened and some delivered to the RAF.

A longer-fuselage long-range Comet 3 had been developed and in the light of the inquiry into the Comet 1s disasters it was redesigned, first flying on 19 July 1954. It did not go into production but made a round-the-world flight and served as a test vehicle.

Comet 3B

Most of the flight tests for the Comet 4 were conducted on the one and only Comet 3 built by Hawker.
In 1957 it was decided that Comets would be reinstated and BOAC ordered 19 Comet 4s. These were powered by 46.71kN Rolls-Royce Avon 524, had longer fuselages than the Comet 1 and could carry 60-81 passengers. The first Comet 4 flew on 27 April 1958 and on 4 October BOAC Comets inaugurated North Atlantic jet services over the London-New York route when Comet 4s of BOAC (G-APDB and G-APDC) made simultaneous crossings in opposite directions. BOAC bought 19 larger, more powerful Comet 4s, and successfully operated the first London/New York jet service from 1958. On 1 April 1959 Comets were put back on the London-Tokyo route.

It was a long range version of the basic Comet design and was recognized by the projection of the two pod fuel tanks on the leading edge of each wing. Following the model 4, the Comet 4B was produced for intermediate-range flights carrying a high-density passenger load.

The model C-2 was a military cargo airplane and was structurally far superior to the original Comet 1.

Comet C4

Transport Command's Comet 4 took 76 passengers, the C2 44 and the Comet T2s, which were often pressed into service could carry 36.

From that time Comets took over much of BOAC's network. Other Comet 4s were used by Aerolineas Argentinas, East African Airways and the RAF. From this version were developed the Comet 4B and 4C which first flew on 27 June and 31 October 1959 respectively. The Comet 4B had a 1.98m increase in fuselage length, a 2.13m reduction in span and was intended for high-speed operation over shorter stages. It could carry up to 101 passengers and was not fitted with wing-mounted external fuel tanks. The main operators of Comet 4B were British European Airways and Olympic Airways.

 

The Comet 4C combined the long fuselage of the Comet 4B with the standard Comet 4 wing. This version was ordered by several airlines and went into service in 1960. A total of 112 Comets were built including 74 Series 4 aircraft; and the type was subsequently developed into the RAF Nimrod.

The DH Comet was designed and built - all 113 of them over 15 years at Hatfield.

The HS.801 Nimrod was originally designed by Hawker-Siddeley, but was also a product of BAE Systems. The Nimrod serves the RAF in two variants: the R1 variant in a reconnaissance and electronic intelligence gathering capacity (ELINT), and the MR2 variant in the Maritime Reconnaissance role.

Ordered by the RAF to replace the Shackleton MR.Mk.3s, the Nimrod is said to have begun in June 1964 when Hawker Siddeley at Woodford began work on the HS.801. Its true origin is in the de Havilland Comet, two Nimrod prototypes were made from unsold Comet Mk.4C airframes, with many changes involved in producing a maritime reconnaissance version. The second prototype (XV148) was converted to HS.801 standard, four Rolls-Royce RB.168 turbofans replacing the Comet’s original four R-R Avons. Its maiden flight was on 23 May 1967, with the second, Avon-powered, aircraft flying two months later.

In mid-1965 a contract to build 38 Nimrod MR.Mk.Is was placed, and the first flew at Woodford on 28 June 1968. All were built as new airframes and delivered by September 1972, although a further eight were completed three years later. In service with RAF Strike Command since late 1969, the Nimrod MR.1 is based on the airframe of the Comet 4C Main difference are a power plant of four Spey turbofan. In addition of an unpressurised pannier beneath the pressurised main fuselage to house the operational equipment and weapons; and modified tail design incorporating an ECM pod and MAD stinger.

 

Subsequent plans were to upgrade 35 aircraft to Mk.II standard (by the installation of new communication systems and advanced tactical sensors), with 11 for the new AEW Mk.3 programme, and the last of the Mk.IIs was completed in 1985. The conversion added some 6000 lbs to the empty weight, and external signs of change were a reduction in cabin windows, new intakes and ducts around the rear fuselage. Other MR.2 modifications include the provision of in-flight refuelling probes, Harpoon anti-shipping missiles, and AIM-9 Sidewinder AAMs for self-defence. Loral early-warning support measures pods (EWSM) are mounted on the wing tips, and minor airframe changes have been made, comprising the introduction of larger finlets to the tailplanes and a new ventral fin. The Nimrod R.1 is a specialised Elint variant.

Nimrod MR.2

The AEW.3 conversion programme was scrapped in 1986 after the con-version of eleven Nimrods at a cost of around NZ$2,700 million.
The UK Ministry of Defence decided drop the Nimrod AEW.3 project in favour of Boeing E-3A Sentry purchase. The planned Nimrod AEW.3 was a conversion of an MR.1 airframe to accept an AEW mission system comprising radar, IFF, ESM, and datalink.
Nimrod R Mk2 - The RAF has three of these specially-equipped versions of the MR Nimrod to fulfil its requirement for long-range elec-tronic reconnaissance missions.
The next changes came in 1982 with the Falklands War, when the Nimrods were required to operate up to 6440 km from their advance base at Ascension Island and carry the Marconi Stingray torpedo, 1000 lb bombs and the AGM-84A Harpoon anti-ship missile. Even air-to-air armament was added in the form of AIM-9G Sidewinders. Another large installation was an inflight refuelling probe to extend its endurance up to 19 hours, which saw large hoses laid over the floor inside the cabin. Placed under the floor when the conflict ended, this gave the Nimrod Mk.IIP code. At the same time GPS was installed in RAF aircraft. The AEW version was plagued with problems and never entered service, being placed in outside storage.

Models offered up four additional hardpoints externally to field even more potent air-to-surface missiles and mine dispensing munitions. Crew accommodations vary per model. The MRA.Mk 4 (or "Nimrod 2000") can house a base flight crew of two personnel along with 7 specialists in designated roles. Additionally, up to 13 relief crewmembers can be carried aboard for extended flights. The Nimrod MRA.4 can operate a 15 hours of endurance time.

Gallery

Comet 1
Engines: 4 x Ghost 50 turbojets, 4,450 lb. (2,020 kg.) thrust.
Range loaded with res: 2,030 sm.
Capacity payload: 14,000 lb.
Fuel cap: 7,050 Imp.G.
Max range with res: 2,610 sm.
Length 93 ft. (28.35 m.)
Wing span 115 ft. (35 m.)
Weight 105,000 lb. (45,540 kg.)
Pax cap: 36-44.
Max cruise speed: 490 m.p.h. (790 km.p.h.).
Cruise alt: 35,000 ft. (11,000 km.) fully loaded.
Range: 1,750 miles (2,800 km.).

De Havilland DH 106 Comet 1 A
Engines: 4 x DeHavilland Ghost 50 Mk 2, 22249 N / 2268 kp
Length: 93.012 ft / 28.35 m
Wingspan: 114.993 ft / 35.05 m
Max take off weight: 115021.6 lb / 52164.0 kg
Max. speed: 459 kts / 850 km/h
Range: 1728 nm / 3200 km
Crew: 3
Payload: 44 pax

Comet 2
Engines: 4 x Avon turbojets.
Range loaded with res: 2,610 sm.
Capacity payload: 14,000 lb.
Fuel cap: 7,050 Imp.G.
Max range with res: 3,700 sm.
Block speed: 444 mph.

Comet 4
Engines: 4 x RR Avon RA.29, 10,500 lb.
Wing span: 115 ft 0 in (35 m).
Length: 111 ft 6 in (33.99 m).
Height: 28 ft 4.5 in (8.65 m).
Max TO wt: 152,500 lb (69,235 kg).
Max level speed: 500 mph ( 800 kph).
Cruise speed 489 mph

Engines: 4 x Rolls-Royce Avon 525B, 46.7kN
Max take-off weight: 73482 kg / 162001 lb
Empty weight: 36430 kg / 80315 lb
Wingspan: 35.0 m / 114 ft 10 in
Length: 36.0 m / 118 ft 1 in
Height: 9.0 m / 29 ft 6 in
Wing area: 197.0 sq.m / 2120.49 sq ft
Cruise speed: 865 km/h / 538 mph
Ceiling: 10000 m / 32800 ft
Range w/max.fuel: 6700 km / 4163 miles
Range w/max.payload: 5350 km / 3324 miles
Crew: 4
Passengers: 72-102

Nimrod MR.1
Engines: Four 11,500 lb (5 217 kg) st Rolls Royce RB.168 Spey turbofan. -
Wingspan: 114 ft 10 in (35.0m).
Length: 126 ft 9 in (38.63m).
Wing area: 2121 sq.ft (197.0 sq.m).
Height: 29 ft 8.5 in (9.01 m).
Max TO wt: 192,000 lb (87090 kg).
Max cruising speed: over 500 mph (805 kph).
Max endurance: 12-14 hr.
Crew: 12.
Max level speed: 575 mph (926 kph).  

Nimrod MR.2
Engine: 4 x R-R Spey 250 turbofan.
Installed thrust: 216 kN.
Span: 35 m.
Length: 38.6 m.
Wing area: 197 sq.m.
Empty wt: 39,000 kg.
MTOW: 80,500 kg.
Warload: 6100 kg.
Max speed: 930 kph.
Ceiling: 13,000 m.
T/O run: 1460 m.
Ldg run: 1620 m.
Fuel internal: 48,780 lt (+8590 lt).
Endurance: 12+ hr.
Air refuel: Yes.
Armament: Stingray torpedo or AGM-84 Harpoon.

Nimrod Mk.IIP
Engines: 4 x Rolls-Royce RB.168-20 Spey Mk.250 turbofans, 12,140 lb.
Span: 114 ft 10 in (35 m).
Length: 129 ft (39.31 m).
Empty wt: 86,000 lbs (39,009 kg).
MTOW: 192,000 lbs (87,090 kg).
Max speed: 500 kt.
Service ceiling: 42,000 ft.
Max Op alt: 37,000 ft.
Normal transit speed: 425 kts.
Ferry range: 9254 miles.
Endurance: 12 hr.
Crew: 13.

BAe / Hawker Siddeley Nimrod MRA.4
Engines: 4 x Rolls-Royce BR710 Mk 101 turbofan, 15,500lbs / 66218 N / 6750 kp thrust
Length: 126.74ft (38.63m)
Wingspan: 127.00ft (38.71m)
Wing loading: 91.23 lb/sq.ft / 445.00 kg/sq.m
Height: 31.00ft (9.45m)
Wing area: 2538.151 sqft / 235.8 sq.m
Empty Weight: 102,515lbs (46,500kg)
Max take off weight: 231271.4 lb / 104885.0 kg
Fuel capacity: 2959 gal / 11200 lt
Maximum Speed: 575mph (926kmh; 500kts)
Maximum Range: 6,903miles (11,110km)
Service Ceiling: 42,000 ft (12,802m)
Endurance: 15 h
Accommodation: 9 + 13
Hardpoints: 4
Payload: max 5500kg

Nimrod

DH-106 Comet