What was the problem with the allison engine? (1 Viewer)

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OK Shortround, let's look at it.

The Bell XP-63's, S/N's 41-19511 and 41-19512, first flew on 7 Dec 1942 with the V-1740-47 engine fitted with an auxiliary supercharger. I'll grant it didn't last that long, suffering a gear up landing in late Jan 1943 … but it did make very good power at high altitude. When you are talking about the October delivery of the P-63 you are talking about service delivery, not when it was flying. Getting planes into service usually took the USA some 9 - 12 months after planes were flying here in the States. The auxiliary-stage (2-stage) Allisons made good power up high. I wish they had incorporated an integral 2-stage supercharger, but that was not to be.
The multi-speed part was achieved in the aux stage with a variable hydraulic speed coupling, but the integral supercharger in the engine accessory case never got multi-speed capability.

The XP-82 did fly in June 1945, but it flew with Merlin engines. Since the British were increasing the license fees for the Merlin, that wasn't something that ever going to last and it didn't. The Allison engine F-82 flew 17 Feb 1947, but 1948 was when they reached operational service. Might have been much sooner, but wartime priority and pressure was greatly reduced on VJ day.

Allison development was effectively halted in late 1945 except for the P-82 engines (-143 / -145) and Allison largely concentrated on jet engines from then forward.

In the end, the Allison did have some issues and the government wasn't seemingly all that willing to have them worked out because they didn't fund a lot of things that would have improved performance and possibly speeded development. I have seen that in other products the US procured as well. Take a good look at the F-111 project and you see another case of government meddling that resulted in many problems.

I like both the Merlin and the Allison today and only wish they could be maintained in running condition longer than will probably prove possible. Parts sources are getting very scarce. It would be nice to see one or both of these engines reproduced or modified with fuel injection and modern ignition technology. Maybe then we'd see the reliability potential of both designs.

One quote from Don Wright, a F-82 field service representative states, "It was an electrician's nightmare, and it wasn't the fact that the engines wouldn't lift the airplane off or fly it. Rather you could never keep it in commission. All of the systems in there were all of the latest electronic advancements from the labs. This was done in a period when the labs at Wright Field put all these requirements into this airplane. It was just a mess all of the time, we had water injection for takeoff, we had WER, and we had a speed density pump instead of a carburetor. Really though the problem with the airplane was to get it to stay in commission. I don't know the percent of time the engines caused it to be out of commission, but it always seemed to be due to the electronics."

Note Don Wright was a North American Field Service Representative, not an Allison representative. I'd like to find those data myself, just out of curiosity, but it is unlikely at this late date and it is what it is.
 
The 1st trials of the Merlin 61 in a Spitfire were conducted in Jan 6th 1942, ie. almost a full year before the XP-63 flew. The V-1710-47 (or E-9, used on the XP-63) were not cleared for the WER, military power was 1100 HP at 21000 ft, 1325 HP for TO. Merlin 61 was not just earlier in the fray, it was making better power.
The next 2-stage V-1710 in use, the E-11* (V-1710-93) was used on XP-63A (as SR6 stated, 1st flew in late April 1943) and P-63A, was good for 1150 HP at 22400 ft, 1325 for TO. The WER power (dry) was how much, 1200 HP at 20000 ft, under 1500 HP at SL? Again, the Merlin 61 of 1942 vintage beats it, the newer Merlins (66 and 70, flight tested in November 1942, in use from summer of 1943, also the 63) further move the goal post. The 1st production P-63A was delivered at October 1943, the 1st production (not prototype!) P-51B is flown on May 5th 1943. The introduction of water injection to the P-63 will boost the power, but that will be felt between SL (1800 HP+ there) and ~22000 ft, or about the same as 'low level' Merlin 66 (1,710 HP @ 8,500 ft and 1,520 HP @ 21,000 ft; thanks, Mike).

Where the plane with 2 stage V-1710 in the same time looses and captures some ground is that it lacks the intercooler - less drag, but also less power. Above 20000 ft, and availability-wise, the 2-stage Merlin held the upper hand at least until VJ day.
 
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RAF Army Co-operation squadrons absolutely loved there Alison engined Mustangs I II and kept them running till the spares ran out. Apparently there wasnt much that could stick with the Allison Mustang at low level even in 45 when the airframes must have been getting quite tired.
 
Hi Tomo,

The Merlin had the high-altitude upper hand when the Allison was run at 60" MAP while the Merlin went higher. I'll give you that one. The Merlin 66 was cleared at the time for +18.00 psi, which was 66+ inches of Mercury.

I'd really love to get ratings at equal boost and altitudes!

We KNOW from interviews that US pilots may times flew Allisons at 75 inches of boost ... and later variants were cleared for 90 inches, but the official ratings during most of the war were at 57 inches. That is what is normally in print at the time.

There are WAY too many comparisons where the indigenous engine is allowed to run higher boost while the engine being compared was limited to some arbitrary number. In my view, if you want a real comparison, run them at the same boost, but that's just my opinion.

In any case, both engines served with distinction.
 
 
I've never heard anything bad about the DB 601/3/5 engines except that there are so few left around ... except that many Luftwaffe pilots witnessed post war the ease with they could started with an electric starter, and wished fervently they had those in WWII in their Messerschmitts. Instead, they got by with the mechanics doing the hand-crank ineretia starting task. On cold mornings this could be a real chore! At least I have heard that from former Luftwaffe mechanics.

I have no data on the times between overhauls for Axis engines, but I suspect they were somehwat shorter early in the war due mainly to being operated from farmer's fields more often than Merlins and Allison were for a large part of the early war. The off-airport operation was probably about equal in the late 1943 through 1944 time frame and was probably more for the Allied engines than the German engines in 1945 as the Allies advanced and the Germans returned to home airfields. This is pure conjecture on my part, but few WWII fighters ran an air filter and fields could be quite dusty as planes took off.

Dust SHOULD mean lower TBO times when operating without an air filter.
 
I know this is an old thread but I just found it while searching for something else.


What was the Allison's performance in 1938? Also, there's the challenge of securing export for the Allison in 1939 and enabling licence-building of the engine in the UK.
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A horsepower graph for the V-1710-33 (C15), dated 5th December 1939, reads:

1,690 b.h.p. at Sea Level (61.0"Hg)
1,480 b.h.p. at 4,000 feet (54.0"Hg)
1,310 b.h.p. at 8,000 feet (48.0"Hg)
1,100 b.h.p. at 12,500 feet (40.0"Hg)
1,000 b.h.p. at 15,500 feet (36.0"Hg)
840 b.h.p. at 20,500 feet (30.0"Hg)
700 b.h.p. at 25,000 feet (24.1"Hg).

All brake horsepower readings at 3,000 r.p.m. Supercharger gear 8.77:1.

The pre-war Air Corps restriction was 40.0"Hg. That was soon dispensed with in the combat zones. P-40 pilots of 3rd Squadron/AVG had the engines set-up to run at 58.0"Hg (1,600 b.h.p.) and this was within a few months of the Pearl Harbor attack. Some pilots asked the crew chiefs if they could get 62.0"Hg, which meant overspeeding the engine to about 3,200 r.p.m.

The source is Vees For Victory! : The Story of the Allison V-1710 engine 1929-1928. by Daniel Whitney, p.124.



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.
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You exaggerate the differences between Rolls Royce and Allison.

The Merlin III (standard Spitfire engine in 1940) was rated for medium altitude and produced only 500 b.h.p. at 30,000 feet. The Merlin 45 (standard Spitfire engine from 1941-1943) developed about 700 b.h.p. at 30,000 feet. That information is found on the engine horsepower graph published by the Rolls Royce Heritage Trust.

A USAAF horsepower graph for P-51 serial 41-37320 shows the Allison V-1710-39 engine produced 500 b.h.p. at 32,000 feet (8.80:1 supercharger gear). The horsepower graph for P-40N serial 42-9987 says that the V-1710-81 engine produced 700 b.h.p. at 30,000 feet, due to a higher gear ratio of 9.60:1.

The Merlin III had a low supercharger gear ratio of 8.58:1, which makes it obvious that high altitude power was not a major priority until after the Battle of Britain.

Single-stage Merlin engines that followed had a higher gear ratio of 9.089:1. Some had a larger diameter rotor for high flying and others had a smaller "cropped" rotor for increased low level power. There is more about this in The Merlin in Perspective - the combat years by Alec Harvey-Bailey.

Two-stage supercharged Merlin engines were not available in 1940, so I don't understand why you penalize Allison for not having what Rolls Royce itself could not provide. Let's not forget that the U.K. and British industry were on war footing in 1939, while Allison and its suppliers worked within a peacetime economy until 1942.



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
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Do not confuse engine power with loaded weight of airplanes. A P-51 fitted with a Merlin III would not climb higher or faster than it did with the V-1710-39. A P-51A fitted with a Merlin 45 would not climb higher or faster than it did with the V-1710-81.

A more direct way of comparison would be: add 2,000 lbs. of ballast to the Spitfire Mk I (to match normal combat weight of a Mustang Mk I or Kittyhawk Mk I) and then pit them against each other in climbing trials.



So why were the Allison-powered Mustangs relegated to Army Cooperation tasks?
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Why were so many Spitfires relegated to Army Cooperation tasks?

In January 1944, 18 of 23 Spitfire IX squadrons on English bases were assigned to 2nd Tactical Air Force. The British home islands still contained 27 squadrons equipped with the Spitfire V, with more overseas, even though this type had been obsolete for two years.

By June 1944, most of the Spitfire IXs had the Merlin 66 and most of the Seafires had a Merlin 32 or Merlin 55M. Those engines were not geared for high altitude performance.



The Allison was a good engine but in no way was it ready for the combat environment of the BoB.
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A Spitfire with the Allison engine would probably out-climb the Merlin III version to 20,000 feet. The Merlin engines cut out in negative-g combat; while the Allison and Daimler Benz engines did not. The V-1710 would have been more than sufficient during the Battle of Britain. But only if we nose dive into a fantasy world where it was politically acceptable for the 1930s British government to develop the Hurricane and Spitfire with foreign made aero engines.
 
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Except that French engineering devised the two-speed supercharger drive. Rights to copy the Farman design were bought and paid for by Rolls Royce and that is what raised the Merlin engine from mediocrity.

Without the French Connection, the Merlin 20, 60, 70, 80 and 100 series would not exist. The Packard V-1650 series (which in turn copied the basic design of the Merlin 20, 60 and 100 series) would not exist.



The supercharger design gave it the edge and all I was trying to say that in wartime that 'edge' was all that mattered. The Allison was a good motor handicapped by the US militaries misunderstandings.

Moral? Leave it to the engineers !!
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Vive la France!





Allison played to its audience in the same manner as Rolls Royce. The U.S. Army Air Corps wanted turbo boost for high-altitude flying, e.g. P-38, P-47, B-17, B-24 and B-29. For the P-38 the USAAF preferred low gear ratios on the internal supercharger because that made the Allison engine more efficient and powerful at low altitude.





The true acid test for aero engines is the civilian market, where the main goals are safety, dependability and profit. Liquid-cooled engines like the Merlin, Griffon and Sabre were not successful commercially.

Moreover a Lancaster or Stirling bomber with four turbo-supercharged R-2800 engines would easily out-lift, out-climb, and out-pace those with Merlins or Hercules II engines.



Why would anyone prefer am Allison to a Merlin?
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Because they wanted to go very fast below 15,000 feet. In July 1942 sixteen Mustangs of No. 2 Squadron flew a sweep into the Ruhr. This was the first time that Allied single-engine fighters (armed with guns, that is) violated German airspace and all planes returned.

Had they preferred to do this job with Spitfires, it would have been a one way ticket.
 
 
Since were unlikely to hear much from Readie for the time being:


The book states at pg. 119 that V-1710 C15 engines were downrated in good deal of 1941 in the USAF service to 2770 rpm max, thus making only 950 HP at 8000 ft, military power. The so-called modernized V-1710 C15s were outfitted with stronger crankcase and bearings.
Compared with the unauthorized overboosting, and thus risky for both pilots and aircraft, the Merlin III have had authorised boosting to +12 psi (54.3 in Hg) already in 1939 (1938?) and +16 psi (62.5in Hg!) for Sea Hurricane, mid 1941, respective powers of 1300 and 1440 HP. The Allison and USAF were plenty late with WER ratings, took them until mid 1942 to come out with that officially.
The Merlin III still beats the C15 in altitude power, albeit not by much.



Horsepower at 20000 ft:
-Merlin III: 890; in service in 1937
-V-1710-33 (C15): 860; in service in 1940 (similar for -33, or F3R engine)
-Merlin XX: 1060 HP; in service in mid 1940
-Merlin 45: 1120; in service in winter of 1940/41
-V-1710-81 (F20R): 950; in production from mid 1942

Bared the aplication of magic dust, there is no way that V-1710 will beat the Merlin in altitude power.

Where the V-1710 might come ahed is the injection carb vs. float carb used in early Merlins, not just for allowing a quick negative G maneuver, but for being less restricting for airflow.


Merlin III was a single speed supercharged engine, the gear ratio employed is 'high', rather than 'low'; if there was a high altitude engine in 1937-40 that was the Merlin III. The early merlin variant with 'low' supercager gearing was the VIII, used on Fulmar.
The gearing does not tells the whole story - Merlin III, VIII, XX and 45 employed the supercharger with impeller of 10.25 in diameter, vs. most of the V-1710s with 9.5 in (as with the 'cropped' Merlins). Coupled with the size of whole intake section that was far bigger in Merlin, the better altitude performance should not came as a surprise.
Merlin 46 and 47 were with 10.85 in impeller, no wonder they were making 1100 HP at 22000 ft (but with less power down low).


The P-51 with Merlins would've been better in speed and climb at altitude than with V-1710s. The Merlin XX and 45 were in volume production before the V-1710-39, and it the -39 can't compete with either Merlin. An 1/4 of power surplus matters.
The -81 is two years too late, it just managed to best the the pre-war Merlin III, it still has 10% less power than the XX or 45.

By June 1944, most of the Spitfire IXs had the Merlin 66 and most of the Seafires had a Merlin 32 or Merlin 55M. Those engines were not geared for high altitude performance.
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The Merlin 66 was better in altitude work than BMW 801D or DB 601A. If one does not want the 66, the 63 and 70 series are available in 1943, unlike the two-stage V-1710 with similar power.

The Merlin was a workable engine 3 years before the V-1710. Waiting for the V-1710 will do to the RAF same as if we delete the Chain Home, or worse.
The situation in the USA was that both R-2800 and license produced Merlin were wanted, in case the V-1710 ends up as a flop.



What you've said has everything to do with Mustang, not with V-1710 supposedly being better than Merlin.
 

Acid test ???? what on earth does a post war Passenger plane have to do with building fighter engines. How many post war transport planes used V1710s.

As for a Lanc with Turb R2800s being a better performer. Well of course it would be an R2800 has 70% greater swept volume than a Merlin and has a Turbo. Good luck getting a production R2800 turbo version much before 1943.
 
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tomo pauk said:
...
Bared the aplication of magic dust, there is no way that V-1710 will beat the Merlin in altitude power.
...
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That works for listed engines, of course.

The 2-speed drive was licensed from Farman indeed, and it was applied in Merlin X before shooting started. The 1st production V-1710 with more than one S/C speed was available in second half of 1943, ie. some 4 years later.
 


The United States was not at war until the last three weeks of 1941, so the "not by much" comment is hardly a good way to frame the real or imagined advantages of the Merlin engine.
 
Please, don't get me wrong - having the V-1710 in production and in service was a major boost to the Allied cause in ww2. The V-1710 was in combat before the USA entere the war, so a comparison with Merlin (or other engine in the time frame) is a valid one IMO. And in that comparison the V-1710 comes out as second best. Further, the USA have had in production, in winter of 1941/42, better engines than the V-1710.
 
EKB said:
The United States was not at war until the last three weeks of 1941, so the "not by much" comment is hardly a good way to frame the real or imagined advantages of the Merlin engine.
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Comparing a MkIII Merlin to a V1710-C15 you must take into account that the MkIII had gone into service in 1937 and was being replaced in service by the MkXII and MkXX Merlins around the turn of 1940/41. I cant find when the III went out of production but it must have been roughly the same time the Spit I and Hurri I went out of production in late 1940. Using 100 Octane, continuous +12 psi boost in the XII and continuous +14psi boost in the XX they were both producing in the region of 1,400 hp at full throttle height. In Jan 1941 the 40 series engines came along and they could run +16 psi boost and were producing 1500hp at FTH.

None of this is to denigrate the superb Allison the RAF Tactical Squadrons loved there Allison engined Mustang MkIs and kept them going till spares ran out in 1945 when the airframes must have been worn out. The fact is the non Turbo Allison was always behind the curve when compared to the Daimler Benz and Rolls Royce engines when it came to altitude performance. This wasnt Allisons fault they built what the customer and owner of the engine the USAAC wanted.

If the USAAC had wanted a mechanically supercharged V1710 with the same or better performance at high altitudes than the RR Merlin or DB 601/605 I am sure they could have built it.

The DB 601/5 series and RR Merlin series ran neck and neck from 1935 to 1945 never able to get the better of each other the non turbo Allison was second all the way there might only have been a length in it but it was still paying place odds nearly all the time.
 
fastmongrel said:
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If the USAAC had wanted a mechanically supercharged V1710 with the same or better performance at high altitudes than the RR Merlin or DB 601/605 I am sure they could have built it.
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Very true. The Alllison company was proposing the 2-stage supercharged V-1710 already in 1938, the USAAC was not interested.


The DB 601 and Merlin indeed went neck and neck. The DB 605, on the other hand, developed considerably less power than the 2-stage supercharged Merlin of the same era for some 2 years, catching up in mid 1944 with DB 605ASM.
The 2-stage V-1710 catched up with DB 605A by mid 1944. (no, second half of 1943)
With that said, too bad there was no in-service single engined fighter made in USA with turboed V-1710.
 
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fastmongrel said:
the RAF Tactical Squadrons loved there Allison engined Mustang MkIs and kept them going till spares ran out in 1945 when the airframes must have been worn out.
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The Allison engined Mustang MkIs must have blown away the similarly powered P-40's.
And V-1650-1 powered Mustang MkIs also would have blown away the similarly powered P-40F's and P-40L's.
Gotta wonder (dream) if Allison engined Mustang MkIs could have/should have replaced P-40's and P-40 production ended sooner.
 

Hi gjs it was the Mustang MkIII with the V1650 motor.

I have read that the Tactical boys ran their Allisons all day at sea level on 130 octane and +18 pounds of boost and the engines took it and came back for more. There was talk of trying the Allison engined MkIs on 150 octane and as much as +25 pounds of boost and sending them on Diver operations against V1s but by that time they were considered too old for it to be worthwhile modifying the engine. They were also reckoned to have less vibration than a Merlin though someone once told me that was the Supercharger drive not the engine. Dont know enough about that to say yes or no personally.

I have found vibration and noise to be more a factor of engine mounting and auxillaries like water pumps, alternators, fuel pumps and blowers than engine design. For example at work we have two 4 cylinder diesel engined cars virtually the same capacity and power but the Ford ticks over like a swiss watch and the Vauxhall (actually an Isuzu engine) ticks over like a piston is about to make a break for freedom. The Ford has a short auxillary belt that runs the Alternator and the Air con pump. The Isuzu has an auxillary belt half a mile long that runs the Alernator, Water pump, Air con pump, and the power steering pump.
 
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