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Lancaster high performance derivatives
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The high altitude Lancaster is the Avro type 684
projected in mid-1941 as a high altitude development
of the Lancaster (type 683)
Service ceiling of the 684 :42.000 feet.
FlyPast May 1991- one page article by George Jenks.
projected in mid-1941 as a high altitude development
of the Lancaster (type 683)
Service ceiling of the 684 :42.000 feet.
FlyPast May 1991- one page article by George Jenks.
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Does anyone happen to know what the expected speed of the high Speed Lancaster would have been?
From (surprise surprise) Tony Buttler’s British Secret Projects – Fighters and Bombers 1935-1950
In August 1941 Avro completed a brochure for its Type 684 Stratosphere Bomber. This all-metal airplane was designed to operate at a height that made it immune from fighter or AA interference and, with the exception of the nose portion of the fuselage, was identical to the Lancaster. The nose contained a pressure cabin, as designed for the experimental high-altitude Vickers Wellington flown in September 1940, which in conjunction with a Rotol blower, would maintain air conditions corresponding to 10,000ft when flying at an altitude of 40,000ft. To achieve this high-altitude flight the air flowing to the carburettors of the four wing-mounted Merlins would be increased in pressure by a slave Merlin 45 housed within the fuselage between and above the wing spars (the blower was placed between and above the rear spar). By regulating the rpm of the slave-blower to suit the prevailing conditions its discharge pressure could be made to correspond to 20,000ft conditions at all heights between 20,000ft and 40,000ft.
The 684 could carry either 4,000lb; 8,000lb or 12,000lb bombs, average cruise would be about 320mph and range 2,300 miles. The service ceiling at the start of the mission was 42,000ft and at the end of a flight 49,600ft. The absolute ceiling was 50,300ft, sea-level rate of climb at 60,000lb was 940ft/minute and at 38,492lb 1,910ft/min, time to 40,000ft was 57 minutes. A total of 2,130 gal of fuel was carried in the wings. The development workload needed for the standard Lancaster and its variants, and the new Avro 685 York transport which used the same mainplane, power eggs, tail and undercarriage, led to the design work on the 684 being suspended.
Dimensions: Span 103.2ft, length 72ft, WA 1,297 square feet,
Powerplant: 4 x Merlin XX, 1 x Merlin 45 (slave)
Performance: Max Speed 410mph at 42,500ft.
Armament: 12,000lb, no defensive armament carried.
In August 1941 Avro completed a brochure for its Type 684 Stratosphere Bomber. This all-metal airplane was designed to operate at a height that made it immune from fighter or AA interference and, with the exception of the nose portion of the fuselage, was identical to the Lancaster. The nose contained a pressure cabin, as designed for the experimental high-altitude Vickers Wellington flown in September 1940, which in conjunction with a Rotol blower, would maintain air conditions corresponding to 10,000ft when flying at an altitude of 40,000ft. To achieve this high-altitude flight the air flowing to the carburettors of the four wing-mounted Merlins would be increased in pressure by a slave Merlin 45 housed within the fuselage between and above the wing spars (the blower was placed between and above the rear spar). By regulating the rpm of the slave-blower to suit the prevailing conditions its discharge pressure could be made to correspond to 20,000ft conditions at all heights between 20,000ft and 40,000ft.
The 684 could carry either 4,000lb; 8,000lb or 12,000lb bombs, average cruise would be about 320mph and range 2,300 miles. The service ceiling at the start of the mission was 42,000ft and at the end of a flight 49,600ft. The absolute ceiling was 50,300ft, sea-level rate of climb at 60,000lb was 940ft/minute and at 38,492lb 1,910ft/min, time to 40,000ft was 57 minutes. A total of 2,130 gal of fuel was carried in the wings. The development workload needed for the standard Lancaster and its variants, and the new Avro 685 York transport which used the same mainplane, power eggs, tail and undercarriage, led to the design work on the 684 being suspended.
Dimensions: Span 103.2ft, length 72ft, WA 1,297 square feet,
Powerplant: 4 x Merlin XX, 1 x Merlin 45 (slave)
Performance: Max Speed 410mph at 42,500ft.
Armament: 12,000lb, no defensive armament carried.
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PRO Kew, AVIA 15/1617, Lancaster pressure cabin.
This was an early proposal for limited pressurisation of the Lancaster, it was later rejected in favour of using the Vickers pressure cabin developed for the Wellington V/VI. Obviously this went nowhere either.
A couple of observations, common themes with the UK cabin pressure bombers are a near dead space behind the pressure cabin (and thus the main spar) and above the bomb-bay through to the rear gunners compartment. Also common is that there appears to be no truly credible solution to the rear gunner problem, pressure suits, his own oxygen supply and mild pressurisation are all mentioned.
This was an early proposal for limited pressurisation of the Lancaster, it was later rejected in favour of using the Vickers pressure cabin developed for the Wellington V/VI. Obviously this went nowhere either.
A couple of observations, common themes with the UK cabin pressure bombers are a near dead space behind the pressure cabin (and thus the main spar) and above the bomb-bay through to the rear gunners compartment. Also common is that there appears to be no truly credible solution to the rear gunner problem, pressure suits, his own oxygen supply and mild pressurisation are all mentioned.
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The list of Vickers-Supermarine type designations contains a reference to 22 Lancasters being converted to "Upkeep" configuration under Type 464.
Now since this hasn't been mentioned elsewhere on the forum, and since Types 463 and 465 were the "Highball" Mosquito conversions, I was wondering if perhaps this could have been a modification of the same sort (though the name suggests it could simply be a rehaul or upgrade of some kind).
Thanks in advance to anyone who can help with this question.
Now since this hasn't been mentioned elsewhere on the forum, and since Types 463 and 465 were the "Highball" Mosquito conversions, I was wondering if perhaps this could have been a modification of the same sort (though the name suggests it could simply be a rehaul or upgrade of some kind).
Thanks in advance to anyone who can help with this question.
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Jemiba said:
Ah, okay. So it makes sense that Vickers-Supermarine should perform both "Highball" and "Upkeep" mods at the same time, since both dealt with integrating a special type of bomb to an existing aircraft type. Perhaps these mods could be more easily performed by using the same workshops/teams for them?
The 103 foot wingspan indicated in PMN1's post seems surprising - I would have thought that the wingspan would have been extended as was done for the Lincoln and the parallel scheme tried in the Do 217P (HZ-Anlage).
An interesting point is that the fuselage mounted engine (Merlin 45) differs from the wing mounted engines in having only a single speed supercharger. I imagine this is to avoid the abrupt changes in engine output that would otherwise result from the supercharger gear changing.
This all raises the question of the nature of the problems encountered by the Germans with the HZ-Anlage - I've never seen any description of what the problems were, though I suppose the reliability issues affecting the early production versions of the DB 603 would not have helped. At least at first sight, the concept has the attraction that the boost provided by the auxiliary supercharger can be easily varied by changing the engine speed.
An interesting point is that the fuselage mounted engine (Merlin 45) differs from the wing mounted engines in having only a single speed supercharger. I imagine this is to avoid the abrupt changes in engine output that would otherwise result from the supercharger gear changing.
This all raises the question of the nature of the problems encountered by the Germans with the HZ-Anlage - I've never seen any description of what the problems were, though I suppose the reliability issues affecting the early production versions of the DB 603 would not have helped. At least at first sight, the concept has the attraction that the boost provided by the auxiliary supercharger can be easily varied by changing the engine speed.
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Stéphane,
the Upkeep is the cylindrical bouncing bomb used by the 617sq dam busters.
There was quite a modification to the bomb bay and lower fuselage area of the Lancaster to spin and launch it.
See attached photo of the trials test-drop of an upkeep at Reculver Bay in May '43 in preparation for Op Chastise
Also a close-up at wikimedia: http://en.wikipedia.org/wiki/File:Upkeep_in_Lancaster.jpg
the Upkeep is the cylindrical bouncing bomb used by the 617sq dam busters.
There was quite a modification to the bomb bay and lower fuselage area of the Lancaster to spin and launch it.
See attached photo of the trials test-drop of an upkeep at Reculver Bay in May '43 in preparation for Op Chastise
Also a close-up at wikimedia: http://en.wikipedia.org/wiki/File:Upkeep_in_Lancaster.jpg
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W
Wingknut
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Hi folks,
Below, three-view of the Avro Type 684 Stratospheric Bomber
Taken from: http://www.warbirdsforum.com/topic/1652-cheap-effective-modification-of-lancaster/page-2
Speculative ("What-if") colour profiles of Avro Lincoln-derived ‘Type 684’ here:
http://kirovrampager.deviantart.com/art/Bronson-the-Avro-Lincoln-Stratosphere-Bomber-331184747
And here: http://www.1940lafrancecontinue.org/FTL/images/avions/autres/Avro_Lincoln.jpg
Cheers, ‘Wingknut’
Below, three-view of the Avro Type 684 Stratospheric Bomber
Taken from: http://www.warbirdsforum.com/topic/1652-cheap-effective-modification-of-lancaster/page-2
Speculative ("What-if") colour profiles of Avro Lincoln-derived ‘Type 684’ here:
http://kirovrampager.deviantart.com/art/Bronson-the-Avro-Lincoln-Stratosphere-Bomber-331184747
And here: http://www.1940lafrancecontinue.org/FTL/images/avions/autres/Avro_Lincoln.jpg
Cheers, ‘Wingknut’
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blackkite
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Hi! Avro 684.
http://www.alternatewars.com/blog/?p=40
https://www.alternatehistory.com/forum/threads/air-and-space-photos-from-alternate-worlds.222258/page-118
Wikipedia
https://en.wikipedia.org/wiki/Avro_684
High speed mail plane project.
https://www.kampfgruppe144.com/Lancaster_HS_Mailplane.htm
http://www.alternatewars.com/blog/?p=40
https://www.alternatehistory.com/forum/threads/air-and-space-photos-from-alternate-worlds.222258/page-118
Wikipedia
https://en.wikipedia.org/wiki/Avro_684
High speed mail plane project.
https://www.kampfgruppe144.com/Lancaster_HS_Mailplane.htm
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Reference the Lancaster stratospheric bomber
I am sure someone would have fairly quickly figured out that Merlin 60 series two stage engines would have been a better choice than the weight and fuel consumption of the Merlin 45 slave engine.
I also wonder what sort of speed and altitude could have been gotten out of a Canadian built Lancaster or extended wing Lancaster (aka Lincoln) using the same nacelles as the XB-38 with turbocharged intercooled (gasp!) Allison (heresy!! sacrilege!!!) engines.
I am sure someone would have fairly quickly figured out that Merlin 60 series two stage engines would have been a better choice than the weight and fuel consumption of the Merlin 45 slave engine.
I also wonder what sort of speed and altitude could have been gotten out of a Canadian built Lancaster or extended wing Lancaster (aka Lincoln) using the same nacelles as the XB-38 with turbocharged intercooled (gasp!) Allison (heresy!! sacrilege!!!) engines.
Merlin 45 slave engine is impressive.
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Piper106 said:
The thing of it is though, both the Brits and the Germans found that increasing boost through supercharging got results as good as turbocharging without the bulk of the plumbing, that's why the British effort in turbocharging never really got going and the Germans cancelled most of their turbocharged engines (DB621-626 and 629 and several variants of the BMW 801 and 802) in late '42.
Nick Sumner said:
True as far as it goes. But there is more to it. A real engineer could probably explain this better. But here is what I have read.
First, fuel chemistry and metallurgy were the keys to successful turbocharging. Only the US had both.
The US and, as a result, Britain had very high performance fuel that made highly supercharged, relatively small displacement engines like the Merlin practical by limiting charge detonation. The Germans had neither the fuel quality nor quantities to use the same design approach. So Daimler-Benz used larger displacement engines with less extreme, continuously variable supercharger drives. Both BMW and Daimler-Benz limited detonation by adopting direct fuel injection and by using methanol-water injection when running high-supercharger ratios. For high-altitude performance, they injected nitrous oxide, which works as both an antidetonant and a supplementary oxygen source.
Successful turbocharging depended on access to alloys that could stand up to the high-exhaust temperatures. The Germans were actually very successful when turbocharging diesels for high-altitude--diesel exhaust is relatively cool. But they were never able to find the right alloys for gasoline. As a result, BMW, which did in fact persist with turbocharging for high altitude performance, never produced a successful high-altitude engine. Britain likewise failed to produce successful turbocharged engines until the mechanical superchargers were well established. In the US, Sam Heron more or less accidentally discovered that the Vitallium alloy used in his dentures had the temperature and wear resistance for use in turbine blades and could be cast precisely (Vitallium is a close relative of Stellite, used in valve seats). When combined with American fuel, this breakthrough made turbochargers practical.
Secondly, turbocharging (at least in theory) met requirements peculiar to the US, which made the US more willing to deal with related problems than Europeans were.
For the US, long range and thus fuel economy were greater concerns than they were for the European powers. The turbocharger had theoretical advantages in this respect. A mechanically supercharged engine burns a lot of fuel just to drive the supercharger and blows a lot of usable energy out the exhaust stacks. A turbocharged engine drives the supercharger using that otherwise wasted energy.
The US was also concerned with rapidity of production and with wide applicability of products than Europeans were. A highly supercharged engine with a mechanical supercharger was a complicated, specialized machine that required a lot of development time and a fairly narrow range of applications. US users expected a single engine to be built in huge numbers and then adapted for various applications, from high-speed fighters to long-range stratospheric bombers and large transports. The only major producer of liquid-cooled engines, Allison, never favored the highly integrated Rolls-Royce approach for this reason. Allisons were built for "bolt-on" superchargers, either turbochargers or Allison's hydromechanical external supercharger. The other manufacturers produced air-cooled radials of the kind favored by airlines. They obtained the required base power by increasing displacement and maintained altitude performance, when required, with turbocharging. When occasional high-power levels were needed, US manufacturers controlled detonation with lots of ADI (Anti Detonant Injection--alcohol and water), richer mixtures, and highly leaded high-quality fuel.
In short, requirements drive implementation in engineering. So different solutions suggest different problems, even when the issues are superficially similar.
Yes, a 60 series Merlin and a turbo charged Allison make about the same amount of power at altitude, but as Iverson pointed out so well, turning that wonderful two stage Merlin supercharger takes a fair amount of fuel. A turbocharged engine can make the same power at altitude while using less fuel. Every extra pound / kilo of fuel that has to be carried to reach the target and return is a pound / kilo less bombs that can be carried. Alternately, if the bomb bay is already full, lower fuel consumption gives a lower gross weight that turns into more speed or altitude.
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Or use Griffons of various denominations.
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Re: Lancaster high performance derivatives, other big bombers and the B-29/32
I read the thread about British efforts to possibly build a high-altitude, heavily-armed long-range version of the Lancaster as well as the threads about the other big, long-range bomber plans and found them most interesting. I especially found of interest the comments of Iverson on supercharging engines and the U.S. vs European challenges and philosophies.
From these discussions it appears the British projects never got terribly far, which may explain the request by the British Air Commission of the USAAF in 1943 for detailed engineering information on both the B-29 and B-32 for the purposes of potentially producing one of these in the U.K. I have attached an internal USAAF letter I stumbled across in my research from Major General Oliver Echols, Assistant Chief of Air Staff, Material, Maintenance and Distribution, to General Arnold. The British had reportedly made several informal approaches to the AAF on this subject prior to submitting a formal request on June 3, 1943. Rather than go into detail I refer you to the copy of the internal AAF letter attached.
Iverson's feedback on the original topic raised a number of questions in conjunction with the above:
How would the British have mass-produced such a large, all-metal aircraft?
What were the chances of the British getting either the B-29 or B-32 into production
before the war ended?
Given the challenges of manufacturing the turbosuperchargers used by either aircraft,
how did the British propose to accomplish this?
American-designed bombers typically had rather large crews in comparison to those of
the British. Where would the extra crew members come from with the RAF already
suffering grievous losses?
What aircraft would have gone OUT of production in order to facilitate either the B-29 or
B-32?
It occurs to me that early British use of the B-29 or - much more likely - the B-32 could have been accomplished via delivery of completed aircraft by flying them across the North Atlantic as was being done with B-17s and B-24s. But even with that as a possibility and the U.S.'s huge lead in the development and production of these aircraft, it would have been late 1944 before even the B-32 would be available and given USAAF plans for the B-29 I believe it safe to say they would never have received any prior to the end of the war in Europe.
All this raises an additional item of interest - finding a copy of the letter from the BAC to General Echols dated on June 3, 1943 as well as any British records on previous, less formal approaches to the USAAF on the same topics. Anyone have anything?
AlanG
I read the thread about British efforts to possibly build a high-altitude, heavily-armed long-range version of the Lancaster as well as the threads about the other big, long-range bomber plans and found them most interesting. I especially found of interest the comments of Iverson on supercharging engines and the U.S. vs European challenges and philosophies.
From these discussions it appears the British projects never got terribly far, which may explain the request by the British Air Commission of the USAAF in 1943 for detailed engineering information on both the B-29 and B-32 for the purposes of potentially producing one of these in the U.K. I have attached an internal USAAF letter I stumbled across in my research from Major General Oliver Echols, Assistant Chief of Air Staff, Material, Maintenance and Distribution, to General Arnold. The British had reportedly made several informal approaches to the AAF on this subject prior to submitting a formal request on June 3, 1943. Rather than go into detail I refer you to the copy of the internal AAF letter attached.
Iverson's feedback on the original topic raised a number of questions in conjunction with the above:
How would the British have mass-produced such a large, all-metal aircraft?
What were the chances of the British getting either the B-29 or B-32 into production
before the war ended?
Given the challenges of manufacturing the turbosuperchargers used by either aircraft,
how did the British propose to accomplish this?
American-designed bombers typically had rather large crews in comparison to those of
the British. Where would the extra crew members come from with the RAF already
suffering grievous losses?
What aircraft would have gone OUT of production in order to facilitate either the B-29 or
B-32?
It occurs to me that early British use of the B-29 or - much more likely - the B-32 could have been accomplished via delivery of completed aircraft by flying them across the North Atlantic as was being done with B-17s and B-24s. But even with that as a possibility and the U.S.'s huge lead in the development and production of these aircraft, it would have been late 1944 before even the B-32 would be available and given USAAF plans for the B-29 I believe it safe to say they would never have received any prior to the end of the war in Europe.
All this raises an additional item of interest - finding a copy of the letter from the BAC to General Echols dated on June 3, 1943 as well as any British records on previous, less formal approaches to the USAAF on the same topics. Anyone have anything?
AlanG
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This topic has produced a lot of discussion. Perhaps it should be split off and moved to the propulsion section?
Correct, I've split, what I regarded as the pure propulsion part of this thread and moved it here
https://www.secretprojects.co.uk/forum/index.php/topic,29601.0.html
If I've missed something, or you would like the title to be different, just tell me, please.
Correct, I've split, what I regarded as the pure propulsion part of this thread and moved it here
https://www.secretprojects.co.uk/forum/index.php/topic,29601.0.html
If I've missed something, or you would like the title to be different, just tell me, please.
Temistocle
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Here the single page appeared on May 1991 issue of FlyPast, as indicated in post #2.
blackkite
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blackkite
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The resin conversion I have to build a model of that Wellington, the pressure chamber measures to 5'-0" diameter. I can't imagine flying any long range mission in one. The Avro 684 was slightly bigger in diameter at 6'-0" and almost twice as long. Still pretty cramped conditions. The B-29 on the other hand had a 9'-0" diameter pressured fuselage.
With regard to the High-Speed Lancaster, I wonder whether it isn't connected with RAF operational research.
As I recall, in his book Disturbing the Universe, Freeman Dyson recounts how his statistical work on Bomber Command losses in the RAF Operations Research indirectly revealed the existence of the German Schräge Musik tactic. Dyson and his colleagues deduced that German nightfighters were formating on RAF bombers in order to attack from below. They calculated that a modest increase in bomber performance would reduce the nightfighters' performance advantage enough to make the tactic futile. Their estimates suggested that suppressing the nose and tail turrets of the Lancaster (as was done on the later Barnes-Wallis bomb carriers) would, on its own, reduce drag enough to achieve this. I do not recall whether Dyson suggested reducing the height of the canopy as well, but it seems like an obvious measure.
As a fast day bomber, the High-Speed Lancaster would hardly make sense: it could hardly outrun day fighters or defend itself, despite the retention of a dorsal turret. But as a fast night bomber opposed by converted Germain bombers, it could have operated with near impunity.
Be that as it may, Dyson's suggestion was met with incredulity: Bomber Command still believed its nose and dorsal gun turrets were ably defending bombers at night.
As I recall, in his book Disturbing the Universe, Freeman Dyson recounts how his statistical work on Bomber Command losses in the RAF Operations Research indirectly revealed the existence of the German Schräge Musik tactic. Dyson and his colleagues deduced that German nightfighters were formating on RAF bombers in order to attack from below. They calculated that a modest increase in bomber performance would reduce the nightfighters' performance advantage enough to make the tactic futile. Their estimates suggested that suppressing the nose and tail turrets of the Lancaster (as was done on the later Barnes-Wallis bomb carriers) would, on its own, reduce drag enough to achieve this. I do not recall whether Dyson suggested reducing the height of the canopy as well, but it seems like an obvious measure.
As a fast day bomber, the High-Speed Lancaster would hardly make sense: it could hardly outrun day fighters or defend itself, despite the retention of a dorsal turret. But as a fast night bomber opposed by converted Germain bombers, it could have operated with near impunity.
Be that as it may, Dyson's suggestion was met with incredulity: Bomber Command still believed its nose and dorsal gun turrets were ably defending bombers at night.
Not sure if it constitutes a high performance derivative per se but I recently read about how Australia was looking at a R-2800 powered Lancaster before switching to the standard Avro Lincoln. Does anyone have any more information or perhaps drawings of what this may have looked like/performed like?
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