What was the problem with the allison engine?
- Thread starter davparlr
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Old Wizard
2nd Lieutenant
Balljoint
Senior Airman
Great engine. Just lagging a year or two in development. Allison is way down the list in regard to blame or incompetency.
soulezoo
Senior Airman
soulezoo
Senior Airman
The above photo is the one I promised a week ago. The photo shows the top turbo, a Garrett 4094r, well but the larger bottom turbo, a Garrett 4718r, is hidden. The 90* pipe shown goes from the bottom turbo and feeds the top turbo. The two braided steel lines shown in the pipe going from top turbo to the intercooler are the nitrous injection lines. Not shown in the photo but are located on the intake on the other side of the engine are 5 lines for the methanol/water injection.
Old Wizard
2nd Lieutenant
fastmongrel
1st Sergeant
Just casting this into the cam boxes would have made the V1710 a winner
![:-\"](/forum/images/smilies/eusa_whistle.gif "Whistle :-\\"")
It was a great engine in its own right . There is no doubt that had RAF fighters been powered by Allison during BoB ,the result would have been the same .18 RAAF pilots bacame aces with P-40's powered by Allisons .Aside from all these nationalistic feelings , I'm at a loss trying to figure out what decisive role Merlin might have played during BoB , it looked pretty tragic compared to 109's state of the art direct fuel injections, 100 octaine fuel perhaps?
Balljoint
Senior Airman
The problem with the Allison only developed when the Allied bombers started daylight flying at 20,000'+. It was solvable by a two-speed, two-stage Allison or Packard Merlins –a tossup in my view. Of course the situation wasn't aided by the bomber boys attachment to self defending bombers, or the thought that a fighter with long range fuel capacity couldn't defend itself, let alone the bombers.
They lacked the hindsight that we're blessed with
In 1940 it was a great engine block. It did not have the supercharger of turbo charger to give performance at altitude. If we only had Allison engined aircraft in the BoB then combat would take place above 20,000 ft where the Allison was way down on power. The decisive role of the Merlin was powering the Hurricane and Spitfire which saw off the LW. The Merlin was 27 Litre swept volume while the Db 601 was 34 Litres.
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Pray tell, why would anyone consider the Merlin engine as 'pretty tragic'? Since when the presence of a fuel injection is a determinant of a great ww2 piston engine?
As for the Merlin in the BoB, there was no what might have been, since it actually was - an important piece in the mechanism that dealt the 1st defeat to the Luftwaffe. The Allison of any year was inferior of a Merlin of the same year, 1940 included, it was acknowledged as such by the USA, and entered license production there as a single major foreign piece of equipment by the date.
There was no such thing as '100 octaine fuel'; fuel injection was a feature of an engine, not of an aircraft.
pbehn speaks truth. The Allison of 1940 couldn't match the Merlin at 20K and above and certainly not the Daimler because it's supercharger was optimized for max power down low, not at altitude. The USAAC decided in the thirties to cast its lot with turbochargers at altitude and superchargers for lower levels, thus American technology for high altitude superchargers lagged a bit behind Europe by the time of BoB.
Turbochargers of the day didn't fit gracefully in P-40 sized aircraft, and even if it had the power at altitude, it wouldn't have had the speed or maneuverability to counter Emil up high. It was a low altitude airframe, heavy, with a draggy high lift airfoil.
Cheers
Wes
The engines for high-altitude aircraft (ones also featuring a turbo) also featured another supercharger, thus making a two-stage supercharging in effect. American superchargers' techology was every bit as good as European, whether in 1939, 1941 or 1944, Germany included. Neither Soviets nor Italian came close to the US superchagers. The 1st gear-driven two stage supercharged engine was the US product.
The V-1710-33 (one of the 1st 'military-grade') Allisons was making more power above 14000 ft than the DB601A of 1940.
The P-40 was a bigger and heavier A/C than the Bf 109, and it was heavier than the Spitfire or Hurricane. P-40 carried more fuel and (in most cases) armament weight than the Eurpoean fighters. The airfoil choosen was not that draggy - 15% T-t-C ratio at root, same percentage as with Fw 190 or Hellcat. 'Low altitude airframe' it was not, as it can be seen when the 2-stage V-1710 was installed, for the performance equal to the Fw 190D-9. The early P-40 were as fast as the Emil, with more range and better roll rate.
The turbos of the day were same size as in 1942 or 1944, the slender booms of the P-38 accepted them after all.
Tomo, thanks for the info. Clearly you've researched this more than I.
Couple of questions. Where was the -33 Allison when the BoB came along? I was under the impression that came later. I should have been clearer about superchargers. It wasn't so much inferior technology as choosing to gear it for max power down low at the cost of high altitude performance. The late thirties Army thought of single engine fighter planes as accessories to the ground army, not high altitude dogfighters.
Cheers
Wes
Couple of questions. Where was the -33 Allison when the BoB came along? I was under the impression that came later. I should have been clearer about superchargers. It wasn't so much inferior technology as choosing to gear it for max power down low at the cost of high altitude performance. The late thirties Army thought of single engine fighter planes as accessories to the ground army, not high altitude dogfighters.
Cheers
Wes
GregP
Major
The issue with the altitude capability of the Allison was the direct result of Air Corps requirements. They got what they ordered. They also declined to fund the development of a higher-altitude version. Allison's use of the auxiliary, 2nd-stage supercharger was a low-cost development that was not optimum, but could be considered for a bomber's larger nacelles. Had the Air Corps / USAAF decided to make a 2-stage integral engine, Allison could have done it. Not sure about the timeframe, but it wasn't magic ... only unfunded.
The powers that be at the time declined to look at a long-term solution, and the Merlin was a gift horse when there was a need. They COULD have asked Allison to make one with a similar supercharger arrangement. That they didn't says a lot about making due. It says nothing about the ability to do it.
Maybe that's why Allison was given the opportunity to develop early jet engines ... the Air Corps saw the piston in technological decline and turbine in technological rise.
Now, there is NOTHING wrong with a Merlin, carb or not, It's a good engine; even a great one. So was and IS the Allison. It all depended on what you were going to do with it, and how high you were going to be. The Allison could get up into the mid 30s altitude, but ti didn't have fighter performance when it got there on one the way up. That's not a disadvantage if you aren't in a fighter. The Allison-engiend B-17 was faster than the R-1820 version, and cruised a lot faster, too.
In modern ownership, the Allison has a much longer time between overhauls. But that isn't a wartime requirement. All military piston aviation engines were overhauled before they really needed it. If they waited until overhaul was needed, the pilot might decline to fly it. So, the fact that the DB605 was slated for a 100-hour TBO doesn't make it a bad engine. It means that the engines in service were reliable, ran well, and generally had 100 or less hours on them as they sat waiting for a mission. That's all.
To me, the title of the thread has a problem. The Allison didn't have many problems, though it did have a few (4, to be exact) when operated in Europe, at first. All were solved. The Air Corps had a short-sighted view of what they wanted and it turned out that what they wanted in 1929 (when the Allison was developed) was NOT what was required in 1940. The intervening time could have been used to update the low-volume engine, but it wasn't. The time from Pearl Harbor until 1943 could ALSO have been used to develop high-altitude capability, but it wasn't, either.
So, we can thank the British for seeing clearly what was needed and having a genius like Sir Stanley Hooker around to help with the supercharger development. I'd like to have seen something like the Fw 187 with a pair of aux S/C Allisons in it, OR a pair of 2-stage Merlins in it. But ... the planes we DID see were really good ones and I can't complain.
There was no shortage of good aircraft on either the Allied or the Axis side. They were the pinnacle of piston development at any particular time in the war. Naturally, some were better than others.
The powers that be at the time declined to look at a long-term solution, and the Merlin was a gift horse when there was a need. They COULD have asked Allison to make one with a similar supercharger arrangement. That they didn't says a lot about making due. It says nothing about the ability to do it.
Maybe that's why Allison was given the opportunity to develop early jet engines ... the Air Corps saw the piston in technological decline and turbine in technological rise.
Now, there is NOTHING wrong with a Merlin, carb or not, It's a good engine; even a great one. So was and IS the Allison. It all depended on what you were going to do with it, and how high you were going to be. The Allison could get up into the mid 30s altitude, but ti didn't have fighter performance when it got there on one the way up. That's not a disadvantage if you aren't in a fighter. The Allison-engiend B-17 was faster than the R-1820 version, and cruised a lot faster, too.
In modern ownership, the Allison has a much longer time between overhauls. But that isn't a wartime requirement. All military piston aviation engines were overhauled before they really needed it. If they waited until overhaul was needed, the pilot might decline to fly it. So, the fact that the DB605 was slated for a 100-hour TBO doesn't make it a bad engine. It means that the engines in service were reliable, ran well, and generally had 100 or less hours on them as they sat waiting for a mission. That's all.
To me, the title of the thread has a problem. The Allison didn't have many problems, though it did have a few (4, to be exact) when operated in Europe, at first. All were solved. The Air Corps had a short-sighted view of what they wanted and it turned out that what they wanted in 1929 (when the Allison was developed) was NOT what was required in 1940. The intervening time could have been used to update the low-volume engine, but it wasn't. The time from Pearl Harbor until 1943 could ALSO have been used to develop high-altitude capability, but it wasn't, either.
So, we can thank the British for seeing clearly what was needed and having a genius like Sir Stanley Hooker around to help with the supercharger development. I'd like to have seen something like the Fw 187 with a pair of aux S/C Allisons in it, OR a pair of 2-stage Merlins in it. But ... the planes we DID see were really good ones and I can't complain.
There was no shortage of good aircraft on either the Allied or the Axis side. They were the pinnacle of piston development at any particular time in the war. Naturally, some were better than others.
I believe that once the USA agreed to supply it (at a cost) they all did.
Very true Tomo but all the turbo and cooling gear are where the pilot with his controls normally are.
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A great point, I would add that the RAF did not accept the Mustang as a front line fighter despite its speed range and agility, its poor performance at altitude was the reason and the Allison engine as delivered was the reason. If USA turbo and supercharger technology was as good as the opposition why were US bombers escorted by Merlin engined P-51s?
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