What was the problem with the allison engine?

[Milosh]

So why were the Allison-powered Mustangs relegated to Army Cooperation tasks? Answer - because the Allison lacked altitude performance which was vital for 1940 because it didn't have the 2-stage supercharger as discussed previously in the thread.

I didn't know Mustangs were available during the BoB.

What Merlins had a 2 stage supercharger in 1940?

 

[buffnut453]

Mustangs weren't available in the BoB, they came after...which is precisely my point. The Allison engine fitted to the Mustang MkIs lacked the altitude performance to enable the aircraft to be used in the fighter role so they were consigned to army co-op instead. If the early Mustangs couldn't hack the altitudes at which Fighter Command expected to operate, how would fitting an earlier version of the same engine to a Hurricane or a Spitfire in 1940 have improved things for the RAF in the BoB?

 

[Readie]

Fair enough. Incidentally, is there definitive evidence of Allison serviceability being better than the Merlin in the Western Desert or is it simply that the P-40 was more associated with that campaign due to the publicity given to 112 Sqn's sharkmouthed aircraft?

The DAF (Desert Air force)

The air defence of the UK always received priority, so the DAF was generally equipped with older aircraft types. Initially equipped with obsolete types like the Gloster Gladiator biplane fighter and the Bristol Blenheim light bomber, the DAF made a good showing against the equally obsolete Italian Air Force. After the direct threat to Great Britain receded, newer types were assigned to the DAF, such as the Hawker Hurricane and Douglas Boston medium bomber in 1941.
US built P-40 Tomahawk/Kittyhawk also went to the DAF as it was unsuited to European operations which were generally fought at much higher altitudes and against more formidable opposition. The P-40 was used initially as an air superiority fighter but it was also adapted (and found to be ideally suited) to ground attack missions.
The DAF always outnumbered its Axis opponents and concentrated on long-range interdiction and direct tactical Eighth Army support. Unfortunately these tactics meant that the faster Messerschmitt Bf 109s of Jagdgeschwader 27 usually had the advantage of height and surprise over the low-level, slow-flying DAF fighters and losses were correspondingly heavy.
In 1942, the DAF reorganized its tactics and upgraded its inventory. Spitfires were eventually assigned in the air superiority role, becoming operational in August 1942, which allowed the DAF to finally turn the tide.
The DAF adapted the Luftwaffe concept of tactical air support and Army co-operation by using fighter-bombers controlled via radio by "Forward Air Controllers"; trained air force observers attached to forward Army units.
The DAF improved the concept by introducing "cab ranks" of fighter-bombers in the air waiting to be called in to attack specific tactical targets. In this way the DAF provided vital and decisive air support to the Eighth Army until the end of the war, fighting through Egypt, Libya, Tunisia, Sicily and mainland Italy. The tactical concepts which had proven so successful in the latter part of the North African campaign were subsequently adopted with even greater success during the Invasion of Europe in 1944.

The tropicalization of the Hurricane and the performance degradation from tropical filters notwithstanding, the Hurricane would still be slower than any model of P40. Hence the preferance for P40 and Spitfire MkV for fighter vs fighter roles in North Africa. Hurricanes were still used in fighter/bomber and ground attack roles though, right up to the end of the desert campaign.

Horses for courses.
Cheers
John

 

[Readie]

Mustangs weren't available in the BoB, they came after...which is precisely my point. The Allison engine fitted to the Mustang MkIs lacked the altitude performance to enable the aircraft to be used in the fighter role so they were consigned to army co-op instead. If the early Mustangs couldn't hack the altitudes at which Fighter Command expected to operate, how would fitting an earlier version of the same engine to a Hurricane or a Spitfire in 1940 have improved things for the RAF in the BoB?

Buffnut, it wouldn't.
No one in their right mind would fit an Allison over the Merlin.
Cheers
John

 

[Readie]

While Merlins were used in some coastal craft the majority of fast craft were powered by either Hall-Scotts (many of the Fairmile Launches) or Packard Marine engines which were NOT Merlins but a 2500cu in engine derived from a late 1920s aircraft engines.

Shortround, This is interesting. I lifted the thread from British W11 wood boats.

12-10-2003, 04:36 AM
The MTBs and MGBs had three Packard Merlins, went at very silly speeds, and were inclined to catch fire and blow up, due to the difficulty of keeping that much gasoline without leaks whilst doing 41 knots, even before the Germans took a hand in things. They also had what were apparently quite lamentable electic servo-pneumatic and servo-mechanical control systems. The larger Fairmile Motor Launches (ML's) which were 112ft LOA had two gasoline engines and made about 20 knots.

For much of WW2 they were involved in fighting with German E-Boats which laid mines in the swept channels followed by coastal convoys and would also attack merchant ships with torpedoes and gunnery.

A very small number were built with Paxman high speed diesel engines for the spcial task of bringing ball bearings, which Britain could not make in the required quantities or to the right specifications, I am not sure which, from Sweden.

The Merlin engined types did not have the range. Unfortunately the Paxmans were not wonderfully reliable, and quite a number of the blockade runners were caught in the open as sitting ducks, with engine failure, so some Mosquito bombers were modified for the task instead.

My late father, who was in the RNVR, shared the common opinion of all who had to do with the MTBs MGBs and MLs that the German E-boat was a very much better boat - diesels and hydraulics. He was with the group that overran the German base at Catania during the invasion of Sicily and found, intact, what appeared to be a complete set of drawings for the E-boat, which he sent off to the Admiralty with much satisfaction; he used to say that the "thank you" letter caught up with him sometime after VJ day, by which time he was in Burma.
Hwyl
12-10-2003, 05:05 AM
Andrew,I did not realise that there are two types of Merlin engines. Are the Packard and Rolls Royce engines completely different?
Andrew Craig-Bennett
12-10-2003, 05:31 AM
No; same engine. R-R design, V12, 27 litre, water cooled, aero engine. A Packard Merlin is a Rolls-Royce Merlin engine, built by Packard in the USA. Packards did modify the design a little, in the direction of simplicity and ease of mass production, but the differences are small.

Well before WW2, it was obvious that the Merlin engine was the best British aero-engine; the Spitfire and Hurricane were designed around it "off the drawing board", and it was also obvious that, as a key element of the war effort, the RR factory that built it was a prime target for bombing.

"Shadow" factories were set up within Britain, and in the USA Packards also contracted to build Merlin engines. They built an awful lot of them - the Packard Merlin powered the P51 and in its marine version it powered British high speed light craft. Packards had started to build the engine for US-built Spitfires; later it was adopted for the P-51.

The mass production of the Merlin was a notable part of the war effort; RR are not, never have been, mass production engineers, and the Merlin was descended from very specialised engines built in small numbers. The original design for the Merlin was a private venture by RR; not in response to any government tender, so all development work was privately funded.

RR did two things with their engine; they developed a quality control programme to achieve very high reliability (basically, they took engines off the production line at random, ran them at full power until they broke, then found out which bit had broken and made it stronger!) and they worked out how to mass produce it whilst keeping it reliable.

I think that rather more than 160,000 Merlins were built; only a few hundred were the marinised version. I don't think any marinised ones survive, although a handful of MLs and MTBs do.

Cheers
John

 

[Lighthunmust]

The importance of the Battle of Britain is hard to overstate. The main reason for that importance is not because it saved Britain or influenced Barbarosa. The influence on an isolationist America containing a significant population of ethnic Germans, Irish, etc., who previously had no affinity for Britain was probably the most important aspect of the BoB. Allisons probably would have gotten the job done, but Readie is right. No one in Britain in their right mind would have installed anything but the well understood Merlin in a Hurricane or Spitfire at that time.

 

[Readie]

The importance of the Battle of Britain is hard to overstate. The main reason for that importance is not because it saved Britain or influenced Barbarosa. The influence on an isolationist America containing a significant population of ethnic Germans, Irish, etc., who previously had no affinity for Britain was probably the most important aspect of the BoB. Allisons probably would have gotten the job done, but Readie is right. No one in Britain in their right mind would have installed anything but the well understood Merlin in a Hurricane or Spitfire at that time.

I agree with a lot of your post, the BoB was vital to us as it was the first defeat for Nazi Germany and we repelled the attacks on our island or, were seen to repel the Germans if you are cynical.
A propaganda gift for Churchill whose rallying cries are well documented. In the context of 1940 any 'win' however slim was vital to the British will to fight and in those terms the BoB was a total victory.
It has entered our culture and 'the few' are revered along with their aircraft and engines.
Britain and America were culturally closer in those days than we are now and, understandably, there was still a reluctance for America to get drawn into another European war. But, you did in the end. I wonder if there was a third European conflict whether you would now?
Cheers
John

 

[MIflyer]

The first V-1710s with two stage compressors had an aftercooler, which loked very similar to teh one atop the Merlin 60 series. However, using that meant redesigning the engine supercharger intake and carburettor, or moving the carb to the auxiliary stage. By not having the aftercooler Allison was able to use a common engine stage supercharger and carb for all their variants - single stage, two stage, and turbocharged.

The loss of the aftercooler meant that ADI was required.

btw two stage Merlins had intercooling and aftercooling. The aftercooler is obvious in pictures, while intercooling was achieved by cooling passages around the supercharger casing. Maybe not super effective, but still there.

Which is just the point I have been making.

1. By not producing a 2 speed (that is single speed impeller speed not a two stage) supercharger, Allison limited the performance of the V-1710 in everything that did not use a turbo, P-39, P-40, P-51. Take a look at the performance graphs in America's Hundred Thousand. With two speeds you had a step in the performance where the first speed topped out and the 2nd, higher one kicked in. With nothing more than a 2 speed supercharger the Mustang Mk.1 would have topped 400 mph and been good for more than medium and low altitude. The P-40 and P-39 would have been better as well. They would not have been as good as with a 2 stage Merlin but better than they were.

2. By not redesigning the two-stage V-1710 engine to take a liquid cooled aftercooler they hurt the performance of the P-63, and especially the F-82. And by not developing a two stage two speed supercharger to directly bolt on the V-1701 and replace the single speed unit that eliminated their ability to compete with the Merlin 61 series.

By taking an "automotive viewpoint" with ease of production being the priority so to be able to use the same accessory case and same basic supercharger design for all V-1710 engines Allison needlessly reduced the value of their products. Given the separate rear case of the V-1710 (as opposed to the Merlin's single case) they could have done this easily without changing the design of the rest of the engine.

Note that they followed the single stage, single speed approach with the V-3420, which was supposed to use a turbo to boost the engine as well.

Government is partially to blame as well. An engineer at NACA was given the job of figuring out how to improve the V-1710 and took the attitude that "it's hopeless, given how bad this engine is." From the perspective of 70 years later we might be Monday morning quarterbacks but it looks pretty clear what needed to be done, and saying "it's hopeless" sure was not the answer. Almost the first technical report that NACA issued, in the immediate post-WWI timeframe, was on the positive effects of supercharging on aircraft engine performance, but in 1942 they said "it's hopeless."

 

[Shortround6]

Shortround, This is interesting. I lifted the thread from British W11 wood boats.

Cheers
John

Interesting but in rather direct conflict with the information in "British and Dominion Warships of WW II" by H.T. Lenton J.J. Colledge and in "Selected Papers on British Warship Design in World War II" Naval Institute Press, Chapter 5 Coastal Force Design by W J Holt.

For some pictures of the Packard try here: Packard V12 Marine Engine

It appears that very few R.N. craft had Merlins during WW II. RAF crash tenders may be different. British were importing and using Issota Fraschini engines in boats built before Italy joined the war in 1940. Fairmile As, Bs and Cs used Hall Scotts, the D boats used the big Packards.

 

[Shortround6]

Which is just the point I have been making.

1. By not producing a 2 speed (that is single speed impeller speed not a two stage) supercharger, Allison limited the performance of the V-1710 in everything that did not use a turbo, P-39, P-40, P-51. Take a look at the performance graphs in America's Hundred Thousand. With two speeds you had a step in the performance where the first speed topped out and the 2nd, higher one kicked in. With nothing more than a 2 speed supercharger the Mustang Mk.1 would have topped 400 mph and been good for more than medium and low altitude. The P-40 and P-39 would have been better as well. They would not have been as good as with a 2 stage Merlin but better than they were.

The two speed drive would NOT have helped the Allison. The 8.80 gear set in the -39 engine was as high as they could go with out redesigning the the drive. THE existing gears would not handle the power when they tried 9.60 gears. For the 9.60 gear performance just look at any Allison with a take-off power of 1200hp and 1125-1150hp at 15,000-15,500ft. That was as good as it was going to get for the Alison. A lower gear, like the 7.48 was needed to get 1325hp for take off. With a 2 speed box you could use 6.44 gears for take-off and very low level flying which would give around 1415hp for take-off but had no extra capacity or a WER rating while keeping the 1150hp at 15,000ft. Going muc above the 9.60 gears would have just sent the impeller tips past supersonic and not gotten any better altitude performance.

 

[Readie]

Interesting but in rather direct conflict with the information in "British and Dominion Warships of WW II" by H.T. Lenton J.J. Colledge and in "Selected Papers on British Warship Design in World War II" Naval Institute Press, Chapter 5 Coastal Force Design by W J Holt.

For some pictures of the Packard try here: Packard V12 Marine Engine

It appears that very few R.N. craft had Merlins during WW II. RAF crash tenders may be different. British were importing and using Issota Fraschini engines in boats built before Italy joined the war in 1940. Fairmile As, Bs and Cs used Hall Scotts, the D boats used the big Packards.

History PT Boats

I have learnt something this evening. Thanks Shortround.
I think it may be the sound of the Packard that has confused people?
Cheers
John

 

[Readie]

...sent the impeller tips past supersonic and not gotten any better altitude performance.

True, every supercharger has its design limitation.I have a supercharger on my car and I can only increase its speed (17% decrease in pulley size) by a certain percentage before it overheats and the power curve falls.
Superchargers offer a great deal of boost,but they also take power to turn whereas a turbo is 'free' power with the exhaust gases.
Cheers
John

 

[Lighthunmust]

Fair enough. Incidentally, is there definitive evidence of Allison serviceability being better than the Merlin in the Western Desert or is it simply that the P-40 was more associated with that campaign due to the publicity given to 112 Sqn's sharkmouthed aircraft?

Off the top of my head I can't point you in the right direction for definitive evidence. But as discussed here and other threads, it is common belief. I know I heard about this issue long before anyone other than DARPA was on the net. If I come across something in my books I will PM you.

 

[renrich]

The BOB was indeed the first time that the German war machine was checked and was important from a morale point of view. It would have even been a greater morale booster if the Germans had actually launched an invasion and a good part of the Wehrmacht had been drowned in the English Channel. However, "The truth is says Fuller, with the possible exception of Goering, the LW commander, nobody believed in Operation Sea Lion. Certainly the German Admirals did not, nor the generals, nor Hitler himself who, according to General Blumentritt, in July told Runstedt privately that he did not intend to carry out Sea Lion." Page 449, "The Decisive Battles of the Western World" JFC Fuller.

The first directive for invasion of England was issued in mid-July under the code name, Sea Lion. All preparations were to be completed by the middle of August. The air preparation was to take one week. Absolutely ridiculous! Apparently even Hitler realised how absurd the plans were. It seems to me that Hitler may have felt at some point that an arrangement with Britain could be made where Germany ruled the continent and the British could go on about their business as usual with their trade and Empire.

The BOB was a momentous event for Britain and perhaps even Joe Kennedy, Ambassador to Great Britain for the US, was shaken in his belief that England could not hold out.

 

[fastmongrel]

True, every supercharger has its design limitation.I have a supercharger on my car and I can only increase its speed (17% decrease in pulley size) by a certain percentage before it overheats and the power curve falls.
Superchargers offer a great deal of boost,but they also take power to turn whereas a turbo is 'free' power with the exhaust gases.
Cheers
John

No such thing as free power

Much higher boost pressure is needed in a turbo for the same bhp due to pressurized air being much hotter, due to conduction from white hot exhaust manifold.

Much more complex management needed in a turbo, to control fueling and ignition due rise of boost pressure compared to a gear driven blower.

Higher pressures and temperatures encouraging detonation, turbo can be a big engine destroyer.

More intercooling needed to cool inlet air.

Much higher incidence of fire due to white hot turbo and manifold.

Compromised exhaust manifold and system function due to restriction of turbo and waste gate not letting the gas flow freely.

Waste gates are fickle things that can jam leading to your cylinder heads coming off with a bang.

Not able to use exhaust jet nozzles worth hundreds of horsepower to the non turbo engine.

Higher cost and with early installations higher weight and greater bulk.

Greater sensitivity to detonation due to unstable octane blends.

The list of exhaust driven blower cons is at least as long as that of a gear driven blower.

The reason you cant get much increase in power in your supercharger by increasing speed is because inlet wont let the air flow you cant just spin it faster. Your cramming too much air in and we all know what happens when you compress air too fast HEAT

 

[Piper106]

I think the Lancaster (and the follow-on development, the Lincoln) was handicapped by being Merlin powered.

Four turbo charged Allisons (basically the whole engine package from a P-38J/L) would have been more effective. More allitude capability compared to the Merlin 20 series in the Lancaster (equal to the Merlin 85 engines in the Lincoln) to help get above the flak and fighters. The stronger Allison power section could handle more power longer than the Merlin (good for the long climb to allitude) with less maintenance. Most importantly, the turbocharged Allison burned less fuel than a Merlin for the same horsepower, so more bombs for the same takeoff weight.

Griffon power in the Shackleton (another Lancaster follow-on) was also less than ideal. Allison had a turbocompound V-1710 running in their test cell. A single stage single speed version of a gas sipping Allison turbocompound would have been a better match to the Shackleton than the Griffon. (Note, this assumes that Napier misfires with their diesel work. They already had data and blueprints for the Jumo 205 diesel, a Deltic version of a Jumo 205 would have been could have been winner for long range patrol aircraft. Even the 'simplified' second version of the Nomad was wayyyyy too complicated. As with the Sabre, Napier reached too far).

I'm going to stand back after I send this post, just in case a vein in Readie's forehead bursts...

Piper106

 

[Lighthunmust]

I think the Lancaster (and the follow-on development, the Lincoln) was handicapped by being Merlin powered.

Four turbo charged Allisons (basically the whole engine package from a P-38J/L) would have been more effective. More allitude capability compared to the Merlin 20 series in the Lancaster (equal to the Merlin 85 engines in the Lincoln) to help get above the flak and fighters. The stronger Allison power section could handle more power longer than the Merlin (good for the long climb to allitude) with less maintenance. Most importantly, the turbocharged Allison burned less fuel than a Merlin for the same horsepower, so more bombs for the same takeoff weight.

Griffon power in the Shackleton (another Lancaster follow-on) was also less than ideal. Allison had a turbocompound V-1710 running in their test cell. A single stage single speed version of a gas sipping Allison turbocompound would have been a better match to the Shackleton than the Griffon. (Note, this assumes that Napier misfires with their diesel work. They already had data and blueprints for the Jumo 205 diesel, a Deltic version of a Jumo 205 would have been could have been winner for long range patrol aircraft. Even the 'simplified' second version of the Nomad was wayyyyy too complicated. As with the Sabre, Napier reached too far).

I'm going to stand back after I send this post, just in case a vein in Readie's forehead bursts...

Piper106

The Lancaster from the BoB squadron will be arriving over your house sometime tonight to give you Readies response.

 

[Milosh]

The Lancaster from the BoB squadron will be arriving over your house sometime tonight to give you Readies response.

No it will be the Canadian Lancaster.

 

[renrich]

Actually, the Lancaster would have probably been a much better and more survivable bomber with four R2800s powering it.

 

[Lighthunmust]

Actually, the Lancaster would have probably been a much better and more survivable bomber with four R2800s powering it.

But it wouldn't be as pretty.