Lancaster production used both Rolls-Royce and Packard Merlins as
quickly as they were available. When the American Packard Merlin was fitted to an aircraft on the production line, it was designated a Mark III. When Rolls-Royce Merlins were fitted, then the aircraft was a Mark I. The aircraft 28
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are impossible to distinguish, being completely identical other than the engines the aircraft had fitted in their nacelles, and so the only way to tell them apart is by serial number, although this will only indicate what mark the aircraft was built as, and not what it may have changed to during service.
The Rolls-Royce- and Packard-built Merlins were completely
interchangeable, and as aircraft completed sorties and added hours to the engines’ working life, faults would of course begin to develop. It was found that there was no design flaw in the engine, the faults being linked to simple operational wear and tear. Aircraft with engine faults would often have engine changes, as would aircraft that had simply reached a number of hours’ flying time that necessitated an engine change under the RAF’s maintenance regimes.
Since the Packard and Rolls-Royce engines were interchangeable, the
maintenance units would replace an aircraft’s power plants with engines that were available from batches delivered or reconditioned. This meant that a Lancaster Mark I could be fitted with replacement Packard engines, becoming an instant Mark III, or vice versa. It was not uncommon for an aircraft to have a mixture of Packard- and Rolls-Royce-built engines, as faulty or
battle-damaged engines were replaced by maintenance units or on squadron.
It is therefore best to view the two marks as a Lancaster Mark I/III, as it is impossible to determine what aircraft you are looking at without detailed reference to the maintenance records of the aircraft in question for the date of a photograph or reference.
The Packard Merlin had one difference from the Rolls-Royce-built engine, namely a tendency to overheat on take-off or landing, which whilst not a particular problem for an experienced pilot to manage could be fatal for a new pilot unfamiliar with the Lancaster. As a result, operational conversion units used only Rolls-Royce engines and Mark I aircraft.
Type 464 ‘Provisioning’ Lancaster
Power:
As per B. Mark I
Dimensions:
As per B. Mark I
Weight:
Empty: 38,000lb
Normal take-off weight: 66,000lb
Performance:
As per B. Mark I
Armament:
6 Browning .303 machine guns in power-operated turrets: 2 in FN5 nose and 4 in FN20 tail turrets 1 9,250lb ‘Upkeep’ mine
Serials:
A. V. Roe: Prototypes; ED765/G , ED817/G and ED825/G
Production; ED864/G, ED865/G, ED886G, ED887/G, ED906/G, ED909/G, ED910/G, ED912/G, ED915/G, ED918/G, ED921/G, ED923/G, ED924/G, ED925/G, ED927/G, ED929/G, ED932/G, ED934/G, ED936/G, ED937/G
Production:
A. V. Roe: 23
The Type 464 ‘Provisioning’ Lancaster was a modification of the B. Mark I/III airframe to carry Barnes Wallis’s ‘Upkeep’ mine, otherwise known as the
‘bouncing bomb’. The development of the weapon and the Dams Raid
operation will be covered in more depth later; this section will concentrate on the modifications made to the airframe.
The airframe of the Mark I/III Lancaster required a number of modifications in order to carry the Upkeep mine. The Upkeep mine required its own launch mechanism to induce the back spin required to make the bomb bounce over water. The mechanism was fitted into the bomb bay of the airframe and the bomb doors were removed. A small hydraulic motor was installed in the
middle section of the cabin to drive the rotating mechanism in the bomb’s 29
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cradle, which imparted the necessary back spin. The increase in weight caused by the launch mechanism was offset by the removal of the dorsal turret.
To function correctly, the Upkeep mine required the aircraft to maintain a constant speed of 200mph at 60ft above the surface of the water in the target dams. The standard altimeter fitted to the Lancaster was viewed as too
inaccurate at such a low level and was replaced by a more sensitive radio altimeter. It was also necessary to find a way to control a constant height of 60ft over the target, so the aircraft was fitted with two Aldis lamps mounted at the nose and rear of the bomb bay and synchronized to converge on the ground when the aircraft was precisely 60ft above. The standard bomb sight was replaced with a special bomb sight made from a triangle of wood with two wooden pegs at each corner of the base. When the pegs lined up with the towers on the dams, the aircraft would be at the correct distance from the dam wall and the bomb could be released.
Each of the Type 464 Lancasters was allocated a G suffix to their serial number. The G suffix indicated that the aircraft required special levels of security and was to be guarded at all times. After the Dams Raid, all the surviving aircraft were re-modified to standard Mark I/III configuration and were reissued to squadrons.
Lancaster B. Mark X
Power:
4 Packard Merlin 38 (KB700 – KB 774)
4 Packard Merlin 228
Dimensions:
As per B. Mark III
Weight:
As per B. Mark III except for a normal take-off weight of 61,500lb
Performance: As per B. Mark III
Armament:
10 .303 Browning machine guns in power-operated turrets: 2 in FN5, 2 in FN50 mid-upper, 2 in FN64 ventral and 4 in FN20 tail turrets. Later aircraft had the FN50 mid-upper turret replaced by Martin mid-upper turrets fitted with 2 .50
Browning machine guns
12,000lb of bombs
Serials:
KB700 – KB799, FM100 – FM229
Production:
Victory Aircraft: 430
By 1942, Canada was already providing a major contribution to the Allied war effort in the air by providing air crew training facilities away from the 1: AVRO LANCASTER B. MARK I (NO. 101 SQUADRON)
D
PA238 (SR-Z) is equipped with Airborne Cigar (ABC) radio countermeasures. No. 101
Squadron’s Lancasters were all equipped with ABC, the three long aerials on the aircraft showing it is fitted. PA238 is fitted with a Rose rear turret armed with two .50 Browning machine guns.
2: AVRO LANCASTER SECOND PROTOTYPE
DG595 was the second Lancaster prototype. It was near to production standard and was sent to Boscombe Down in August 1941 for flight testing. The ventral FN64 turret was fitted to DG595, but was deleted from production Lancasters early on.
3: AVRO LANCASTER B. MARK I (FE) (NO. 35 SQUADRON)
TW878 (TL-H) was one of No. 35 Squadron’s Lancasters that took part in a goodwill tour of the United States of America in 1946 at the invitation of the USAAF. Sixteen Lancasters from the squadron toured the United States for most of August 1946, arriving back in the UK on 29 August.
4: AVRO YORK, THIRD PROTOTYPE (NO. 24 [COMMONWEALTH] SQUADRON)
LV633 was the third prototype York. It was allocated to Sir Winston Churchill as his flying conference room. The aircraft carries the name ‘Ascalon’ under the cockpit.
30
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1
2
3
4
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Lancaster B. Mark I Special
predations of the Luftwaffe, and a steady stream of trained air crew. The with Grand Slam bomb. The
Canadian government wished to contribute further by producing aircraft. An nose of the aircraft shows the
agreement was reached that resulted in the formation of the Victory Aircraft fairing that replaced the nose
Corporation to produce Avro Lancasters under licence fro
m A. V. Roe. The turret.
Corporation was wholly owned by the Canadian government. The Lancasters built in Canada were classified as the Lancaster B. Mark X.
The first 75 aircraft were fitted with Packard Merlin 38 engines, with the remaining aircraft fitted with the Packard Merlin 228 engine. The Mark X was outwardly identical to the B. Mark III except for the fitting of enlarged bomb bay doors as standard and the return of the FN64 ventral turret. The original needle-bladed propellers were superseded by broader paddle-bladed propellers from KB774 onwards, which gave improved rate of climb and altitude
performance.
The majority of aircraft produced by Victory were flown or shipped across the Atlantic Ocean to Britain, where they were issued to Royal Canadian Air Force bomber squadrons operating from England.
Lancaster B. Mark I Special
Power:
4 Rolls-Royce Merlin 24 engines
Dimensions:
Span: 102ft
Length: 59ft 6in
Height: 20ft
Wing area: 1,300sq ft
Weight:
Loaded weight: 73,000lb
Performance: Service ceiling: 17,000ft with weapon
Max speed: 275mph at 15,000ft
Range: 1,650 miles with Grand Slam bomb
Armament:
4 Browning .303 machine guns in a power-operated tail turret.
1 22,400lb Grand Slam bomb
Serials:
PB995-PB998, PD112-PD139
Production:
A. V. Roe: 32
32
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Flying Officer E. W. Weaver of
No. 617 Squadron with Grand
Slam bomb loaded into a
Lancaster B. Mark I Special’s
bomb bay. The bomb is held
in place by two straps, one
just behind Weaver’s hand and
one further aft (the pale band
on the bomb).
The Mark I Special came about because of the need to find machines capable of carrying another of Barnes Wallis’s wonder weapons, the 22,400lb Grand Slam bomb. The bomb was the biggest weapon dropped by the Royal Air Force during World War II. It measured a massive 25ft 5in long and was filled with 11,000lb of Torpex high explosive. The bomb was designed to penetrate
especially tough targets such as the reinforced concrete U-boat pens built by Germany, which had reinforced concrete roofs up to 35ft thick and were
impervious to any other weapon. The bomb was a free-fall weapon that
reached supersonic speeds on its journey towards the ground while having spin imparted by its four canted tail fins, finally embedding itself deep in the target before exploding.
The massive proportions of Wallis’s earthquake bomb meant that the only aircraft capable of carrying it was the Lancaster, albeit with a large amount of modification. The challenge of loading the Grand Slam bomb into the
Lancaster resulted in the removal of the bomb bay doors and the modification of the bomb bay, including the fairing in of both ends, to fit a single weapon.
The prototype B. Mark I Special flew with all three turrets in place, but it was soon realized that the nose and mid-upper turrets would need to be removed and faired in, in order to save weight. This left the aircraft equipped with just the four-gun tail turret, although later the tail turret would be reduced to mount just a pair of .50 Browning machine guns. The increased weight of the aircraft and bomb also led to the undercarriage being strengthened.
The fuel load of the Mark I Special was reduced to 1,675 gallons, restricting the aircraft to a range of 1,650 miles. This reduction in range did not affect the type’s operational usefulness, as by the time it entered service in March 1945 the Allies were firmly ensconced in mainland Europe and the aircraft could reach all of the targets allocated to it from airfields in Europe.
The massive Grand Slam bomb challenged even the Lancaster, which even
after modification and weight reductions was only capable of lifting the bomb to an altitude of 17,000ft. The ceiling of the Lancaster B. Mark I Special was lower than the level Barnes Wallis viewed as the ideal height from which the bomb should be released for maximum penetration. Despite his
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fears, the practical results of using the new weapon proved the concerns to be unfounded, and 41 Grand Slam bombs were dropped from Lancasters
before the end of the war.
Lancaster B. Mark VI
Power:
4 uprated Rolls-Royce Merlin 85/87 engines
Dimensions:
As per B. Mark III
Weight:
As per B. Mark III
Performance: As per B. Mark III
Armament:
As per B. Mark III
Serials:
DV170, DV199, JB675
Production:
Metropolitan Vickers: 2
A. V. Roe: 1
A small number of conversions were also undertaken
The Lancaster B. Mark VI was an attempt to fit the Lancaster with the uprated Rolls-Royce Merlin 85/87 engine. Two airframes (DV170 and DV199), built by Metropolitan Vickers at Trafford Park, were sent to Rolls-Royce to be fitted with the new engines in June and July 1943. A third airframe built by A. V.
Roe at Newton Heath, JB675, was delivered to Rolls-Royce in November
1943 to become the first ‘prototype’ B. Mark VI. Following modification by Rolls-Royce, JB675 was delivered to A&AEE at Boscombe Down for trials. It later served with four different squadrons, although it only flew a single operational sortie, before being transferred to the Royal Aircraft Establishment (RAE) at Farnborough.
Only a small number of Lancasters were converted to B. Mark VI
configuration, which served mainly with No. 7 Squadron at RAF Oakington and No. 635 Squadron at RAF Downham Market in the Pathfinder role.
The engines, whilst proving to be more powerful, gave cause for concern due to reliability issues, which is likely to have been the reason that the B.
Mark VI had been withdrawn from operations by November 1944. The
experience with the B. Mark VI was, however, useful, and influenced what would come later.
Lancaster B. Mark I (FE)
Power:
As per B. Mark I/III
Dimensions:
As per B. Mark I/III
Weights:
Varied depending upon tropical equipment fit
Performance:
Varied depending upon tropical equipment fit
Armament:
6 Browning .303 machine guns in power-operated turrets: 2 in FN5 nose and 4 in FN20 tail turret
Serials:
Various aircraft were fitted as B. Mark I (FE)
Production:
2 prototypes and various modified Mark I airframes
The Lancaster B. Mark I (FE) was a result of the Royal Air Force beginning to give thought to operations in the Far East in 1944, in support of the United States Army Air Force’s air offensive against Japan. It was decided to use the Lancaster for long-range strategic bombing operations in the Far East until the replacement was available. A number of completed Lancaster B. Mark I
aircraft were taken from the production lines at Vickers-Armstrong and Sir W.
G. Armstrong Whitworth and Co. for storage at No. 38 Maintenance Unit at Llanlow, awaiting tropicalization ready for despatch to the Far East to serve 34
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with ‘Tiger Force’, the RAF’s task force created for service against Japan This Lancaster B. Mark VI is alongside the United States Army Air Force. These aircraft were designated fitted with an Armstrong Lancaster B. Mark I (FE).
Siddeley ASX jet engine in its
bomb bay in late 1945 for
In view of the long distances involved in operating in the Pacific Theatre flight tests. The nose turret
of Operations, a number of suggestions were made concerning ways in which has been faired in to save
the Lancaster’s range could be increased. One idea saw two Lancasters, weight, since it is not required.
HK541 and SW244, converted to carry large saddle tanks on the upper
central fuselage. These long-range fuel tanks were fitted in a large fairing, which extended from the cockpit to just aft of the trailing edge of the wing and necessitated the removal of the mid-upper turret. The tanks increased fuel capacity by 1,500 gallons, but also increased the all-up weight of the aircraft to 72,000lb. HK541 underwent trials at A&AEE at Boscombe Down before being sent to Mauripor in India for in-theatre trials in May 1944, being followed by SW244 in August 1945. The two aircraft underwent trials with No. 1577 Flight, where it was found that the aircraft’s handling
characteristics were poor, and the project was abandoned. The aircraft were flown home and scrapped.
Another idea was for 600 Lancasters to be converted to in-flight refuelling tankers. In-flight refuelling had been demonstrated before the war, although its application in military operations was relatively untried. Trials began at A&AEE at Boscombe Down at the end of 1944 using LM730, which had been modified with in-flight refuelling couplings. Delays in the arrival of the Lincoln and the end of the war meant that the programme’s relevance became academic and the project was cancelled.
Despite the trials with saddle fuel tanks and in-flight refuelling, it was decided that ‘Tiger Force’ would be equipped with tropicalized standard Lancaster B. Mark I, B. Mark III or B. Mark VII airframes. The mid-upper turrets would be removed to allow the FE aircraft to be fitted with an
additional 400-gallon fuel tank in the bomb bay. The FE-designated aircraft 35
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were also all to be fitted with the best navigation equipment available, including Gee, Loran, Rebecca and H2S.
The atomic bomb attacks on Hiroshima and Nagasaki brought an end to
the war in the Pacific, and the need for ‘Tiger Force’ ended. The force disbanded in October 1945 and all of its Lancasters had their mid-upper turrets refitted, as they were no longer required to carry out long-range missions.
Avro Lancaster Page 5