What was the problem with the allison engine?

GregP said:

Malta, where Coral dust was so prevalent, it wouldn't make TBO and would be overhaul based on condition rather than overhaul hours.

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I dont know if there are any Coral Reefs on Malta anymore but the Island is made from a fairly soft but incredibly gritty Corraline Limestone with layers of Greensand which is an even grittier soft Sandstone containing lots of mineralised marine life. Both types of dust plus any liquid turns it into something resembling Valve Lapping in compound.

So yes its Coral dust just 55 million year old Coral dust

I took that from WWII operation accounts. Almost all mention dust and several mention coral dust. Whether it is sand or coral, it seems to eat engines for breakfast. I known they had coral dust in the Pacific as I've experienced it myself.

What they really needed in the Pacific were air filters, at least for takeoff, landing and ground operations. Don't believe they ever got them.

I took that from WWII operation accounts. Almost all mention dust and several mention coral dust. Whether it is sand or coral, it seems to eat engines for breakfast. I known they had coral dust in the Pacific as I've experienced it myself.

What they really needed in the Pacific were air filters, at least for takeoff, landing and ground operations. Don't believe they ever got them.

The Bf109F seemed to have a very good filter that had a flap to divert air when taking off and landing but let the air flow freely when in the air. The early RAF Vokes filter robbed power and speed some Hurricane MkIs in the Med struggled to top 300mph with the Vokes.

I don't think the Mustang I P-51 had dust filters, but they were fitted to the P-51A's carburettor air intake, and the A-36's.
(from the Manual of Instructions for the P-51A Mustang Fighter Airplane (Contract AC-30479, NAA, August 1 1943)

Very interesting Are those manuals available for download?

tomo pauk said:

Very interesting Are those manuals available for download?

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Yep; via membership of Avialogs: Aviation E-Library and more: it's a great resource.

The carby air intake for the A-36 had a different system to that of the P-51A

(Erection and Maintenance Instructions for A-36A Airplane (15 November 1943; revised 25 October 1944)

Aozora said:

EKB raised the whole "Merlin is so-o-o unreliable vs the Allison" schtick;

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You need to show us when Mustangs with the Allison engine suffered this many problems:


" Operational Diary—1944 [4th Fighter Group]

25 February 1944—The ground crews had their hands full trying to get about 50 Mustangs [P-51B] ready for combat. Before morning all of the kites had been painted in QP, WB, VF livery in anticipation of the first Mustang show the next day.

26 February 1944—Weather scrubbed the 4th's Mustang debut but at least there was time for familiarization …

27 February 1944—At 1315 a Rolls-Royce tech representative held a briefing on the P-51. Don Blakeslee held a discussion on flying problems with the Mustang which had been disappointingly numerous. A plague of mechanical gremlins diminished the pilots' enthusiasm for the new fighter. Jim Goodson, Willard Millikan and George Carpenter had bounced the new paddle-bladed P-47s of the 56th and frustratedly reported that these Thunderbolts were a match for the Mustang upstairs and downstairs. This added to the air of uncertainty.

28 February 1944—Maj. Clark led the first Mustang mission, a Free Lance under Type 6 control with two 75-gallon drop tanks under the wings of each kite … Both 334 and 336 got 12 aircraft up while 335 put up 11, but there were several aborts due to mechanical problems …

29 February 1944—The P-51's ugly side reared its head—Mills prop began throwing oil and his wing tanks would not feed; Biel's cooling system and RT went out Beil's cooling system and R/T went out; Rafalovich could not get enough manifold pressure and his R/T also quit. France, Chatterley and Smith could not catch up with the Group. All six were forced to abort the mission. After everyone got back a bunch of disgruntled pilots went to the briefing room at 1645 to hear a 354th Group pilot talk about mechanical failures with the Merlin engine.

4 March 1944—During combat several pilots were hampered by windscreen frost and jammed guns. At 18,000 feet and 550 mph indicated, Ward's canopy, wing and tail came off, hitting Megura's kite … Paul Ellington had engine problems and bailed out over the Dutch Coast … Bob Richards was killed when he went in near Framlingham returning from the show. Blakeslee returned fuming, his guns wouldn't fire at all.

[John Godfrey later said that Richards crashed due to motor trouble].

7 March 1944—New spark plugs were put in the kites to see if this might improve the engine problems.

8 March 1944—In spite of claims of 16 destroyed, rough engines and unservicable drop tanks were the order of the day.

13-15 March 1944—In spite of the successes against the Germans, the P-51s were mechanical nightmares and they were grounded. Rough engines, props throwing oil, glycol leaks and auxiliary tank feed problems were causing aborts on every mission. These two days all the wing bolts were replaced and engine mount bolts were magnafluxed, but these precautions weren't effective. On the 17th Burtonwood manufactured new motor mount bolts but even these turned out to be unsatisfactory and by April North American had to rush 250 sets VIII FC.
Table II prop kits for the Mustang arrived in February and March stripped and useless, so propellers continued to be in short supply until July. V-1650 engines were also in short supply through March and April. All this added up to low mission strengths for quite a while. Many times a squadron was able to get but 10 airplanes up for a mission. To get 20 up was a minor miracle …
The gloom over losses due to engine problems was hard to dispel. At least five pilots went down during March due to glycol and engine failures, possibly more since several losses are noted due to unknown causes. The gunnery and electrical systems also failed with regularity, resulting in lost kills. And the installation of the 65-gallon upright tank behind the pilots' seat without baffle plates to prevent violent shifts in the center of gravity was considered a nightmare by several pilots.
Blakeslee's crew chief, Harry East Jr. never could get the right bank of the Chief Cook's Merlin to quit smoking and missing. Col. Don kept the kite because it was fitted with a better-vision Malcolm hood. 43-6437 was not replaced until the hydraulic line was perforated, much to East's relief.".


See p.40-45
Garry Fry Ethell. Escort To Berlin: The 4th Fighter Group in World II. Arco, 1980.

Aozora said:

it's up to EKB to support his own convictions with more than just meaningless, bald statements.

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Show us evidence that P-51s with the Packard Merlin engine were more reliable than P-51s with the Allison engine. Surely you can do better than fling accusations like cream pies.

Aozora said:

I suggest EKB read Harvey-Bailey, pages 40-45 to find out. The isolated troubles of the Griffon on some Seafires have nothing to do with the Allison V-1710.

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If you didn't want to read bad news about the Griffon engine, then you shouldn't ask direct questions about the Griffon engine. I can't protect you from the truth. A brief overview of the Merlin engine written by a former Rolls Royce employee (Harvey-Bailey) was not intended to be a completely catalogued timeline of problems. It's a summary and nothing more.

A large number of the problems you list were not with the V1650 engine (Its not a Merlin) but with the plane and ancillaries. These were new planes to the unit the ground boys were inexperienced on the new type. Go look at any Unit history covering the period after the changeover between types and you will find the same thing. Go look at any unit logs when the unit had used the new P51 in combat for 6 months and compare.

This thread was about someone asking genuine questions about why the Allison didnt seem to get the fame that other engine types got. You are simply trying to knock down an engine because of its fame and mythology, what people say and think now has no bearing on 70 years ago.

The Merlin/V1650 engines might have had more problems than a V1710 but ask yourself this question would you want to take on the Luftwaffe in their backyard at 30,000ft in a P51 B,C,D or K powered by a 1943 V1710 with a 2 speed 1 stage non Turbo blower or a V1650 with 2 speed intercooled 2 stage blower. You cant say "ahh but the V1710**** series ran on the stand in 1945 for 10 million hours and gave 3,000hp at 50,000ft and had freakin laser beams on the cam boxes" its between a V1650-3 or its May 1943 Allison equivalent.

Oh and by the way yes the Merlin/V1650 is my favourite engine of all time but I am not blind to its many flaws and unsuitability for passenger air use. I dont have a 2nd favourite but a group of engines which I regard as exceptional but just not Merlin/V1650s and in that group of 6 is the V1710.

The introduction of the Merlin Mustang was a new thing for the 8th AF, with Packard just begining the production of 2-stage V1650s in Spring 1943. As a new outift, it will come with more or less a number of issues. That was true for P-47 (P-47B was unfit for war, the engine problems persisted until mid-1943 with P-47C and D, again engine problems with M), F4U (both engine and airframe, not just for carrier service), P-38 (host of the problems with engines' installation, most notably in the P-38J, insufficient heating prior spring of 1944 when installation of second generator allowed for a redesign of the cockpit heating sytem). P-40 in 1941 with restricted engine power.
Basically everytime the design, either airframe or engine or both, was pushing forwar it encountered issues, some designs (and the design staff) being better in overcoming the issues than another. The fact still stand that Merlin Mustang ranged far and wide against German and other Axis targets, with the unprecedented range and performance - just what and when was needed, even if we account the P-38 history. This, added to the wordwide use of the Merlin will still mean plenty for anyone.

If we talk post-war pistons, let's recall that V-1710 powered P-82 were never as reliable nor as performing as V-1650 powered P-82s.

tomo pauk said:

The introduction of the Merlin Mustang was a new thing for the 8th AF, with Packard just begining the production of 2-stage V1650s in Spring 1943. As a new outift, it will come with more or less a number of issues. That was true for P-47 (P-47B was unfit for war, the engine problems persisted until mid-1943 with P-47C and D, again engine problems with M), F4U (both engine and airframe, not just for carrier service), P-38 (host of the problems with engines' installation, most notably in the P-38J, insufficient heating prior spring of 1944 when installation of second generator allowed for a redesign of the cockpit heating sytem). P-40 in 1941 with restricted engine power.
Basically everytime the design, either airframe or engine or both, was pushing forwar it encountered issues, some designs (and the design staff) being better in overcoming the issues than another. The fact still stand that Merlin Mustang ranged far and wide against German and other Axis targets, with the unprecedented range and performance - just what and when was needed, even if we account the P-38 history. This, added to the wordwide use of the Merlin will still mean plenty for anyone.

If we talk post-war pistons, let's recall that V-1710 powered P-82 were never as reliable nor as performing as V-1650 powered P-82s.

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For a moment I thought I had been reading the F-35 thread

Way off-topic, and way too wrong - the 15-20 years of the JSF/F-35 development that was supposed to use off shelf things to speed up the design has nothing to do with US succeses like the P-51, 47 or 38. Just think what Kelly Johnson's team would've done with SR-71 in 15-20 years.

EKB said:

You need to show us when Mustangs with the Allison engine suffered this many problems:

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To make an accurate comparison you need to show us when that many Allison Mustangs were being fielded under the same conditions. I would guess they would have had the same issues.

These squadron reports and tid-bits should not be used to accurately determine MC rates, they could be misleading. The real determination of aircraft reliability considers the number of aircraft assigned to a squadron, minus those grounded for routine maintenance. At that point a fly order is formulated and it is factored against ground and air aborts, that gives you your true MC rates.

Some more Allison info, describing the differences between "F" series engines (from the Allison Handbook of Operation and Maintenance for Allison V-1710 "F" Type Engines 1 April 1943):

FLYBOYJ said:

To make an accurate comparison you need to show us when that many Allison Mustangs were being fielded under the same conditions.

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To begin with the Mustang was not a new type of airplane in March 1944. Wright Field tested the first production model P-51B one year earlier and issued a report in May 1943, by which time the RAF already had fifteen squadrons of Mustang Is in the U.K. Missions to Germany started in July 1942.

FLYBOYJ said:

I would guess they would have had the same issues.

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The two-stage Packards used by 4th FG in March 1944 were similar to the Merlin 61. Some of the problems with this engine did not apply to the Mustang I or Mustang II.



September 1942 —" I did very little operational combat flying during September. I did do a couple of high altitude interception attempts, one on the Ju 86 which came over at high altitude, as always. On this attempt I had trouble with the second-stage blower [Merlin 61], and when I finally reached 34,000 feet, I had much surge in the engine. Most of my time was spent testing our new Spit 9. We seemed to have a lot of trouble with the radio transmissions on them, and a lot of trouble with the cannons. Nevertheless, we were all looking forward to flying them operationally, because they were a vast improvement over our Spit 5's."

Richard Alexander
133 (Eagle) Squadron


6 September 1942 —" Spike Miley was having trouble with his power [Merlin 61] and was lagging behind. An FW 190 was stalking him, so I broke formation and went back to help him. As I turned left to be in the sun so the Hun would have less chance of seeing me. He didn't see me and I came around and hit him good. Pieces started flying off his plane and he turned right, going down in a steep turn. I was sure he was finished and I caught up with Spike and we were able to rejoin the squadron. About then all hell broke loose as fifteen FW-190s hit us. Two of the Fortresses were shot down and we lost two planes, Doorly and Gudmundsen."

7 September 1942 —" We were about twenty-five miles inside the Dutch coast when my engine [Merlin 61] began to surge and run very rough and only make about 50 percent power. I began to lag behind and soon lost sight of the squadron. Our controller in England heard me calling to the squadron for help and said they had six enemy fighters plotted on their scope between me and the coast. They were just milling around, waiting for me, since my squadron was already well west of them in mid-Channel. I was now alone and on my own. "

Leroy Gover
133 (Eagle) Squadron


R. L. Alexander. They Called Me Dixie. Robinson Typographics, 1988 (p.102).
P. D. Caine. Spitfires, Thunderbolts and Warm Beer. Brassey's, 1995 (p.105-106).

FLYBOYJ said:

The real determination of aircraft reliability considers the number of aircraft assigned to a squadron, minus those grounded for routine maintenance.

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Obviously true. But too many people have fallen back on nostalgia or compact technical histories of engines and airplanes and that is always misleading.

fastmongrel said:

A large number of the problems you list were not with the V1650 engine (Its not a Merlin) but with the plane and ancillaries. These were new planes to the unit the ground boys were inexperienced on the new type. Go look at any Unit history covering the period after the changeover between types and you will find the same thing. Go look at any unit logs when the unit had used the new P51 in combat for 6 months and compare.

This thread was about someone asking genuine questions about why the Allison didnt seem to get the fame that other engine types got. You are simply trying to knock down an engine because of its fame and mythology, what people say and think now has no bearing on 70 years ago.

The Merlin/V1650 engines might have had more problems than a V1710 but ask yourself this question would you want to take on the Luftwaffe in their backyard at 30,000ft in a P51 B,C,D or K powered by a 1943 V1710 with a 2 speed 1 stage non Turbo blower or a V1650 with 2 speed intercooled 2 stage blower. You cant say "ahh but the V1710**** series ran on the stand in 1945 for 10 million hours and gave 3,000hp at 50,000ft and had freakin laser beams on the cam boxes" its between a V1650-3 or its May 1943 Allison equivalent.

Oh and by the way yes the Merlin/V1650 is my favourite engine of all time but I am not blind to its many flaws and unsuitability for passenger air use. I dont have a 2nd favourite but a group of engines which I regard as exceptional but just not Merlin/V1650s and in that group of 6 is the V1710.

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Is it better to play favorites or sort out what really happened? Germany had more critical problems than the Allies thanks to shortage of heat-resistant materials. In 1945 the Daimler-Benz engines put in the Me 109 averaged about 10 hours between changes, per General Steinhoff. Sometimes the engine technicians had to unpack and test several DB 605s before they found one that started up and ran acceptably.

The Germans were in far better situation in 1941-43 (and no, they did not need such great heat resistant materials in their non-turbo engines), yet they have these issues, ranging from big to still significiant:
-BMW 801C and D, mid 1941 to oct 1942
-Jumo 222
-Db 606
-Db 603A, whole of 1943
-DB 605A, 'the engine that killed Marseille', from mid 1942-late 1943
-DB 601N - 1 minute emergency rating??
-Jumo 211N - managed to kill half of Ta 154 that crashed

They would've traded the 'reliability' of their engines with relibility of Merlin every day, and twice on sunday.

They built about 168,000 Merlins from all suppliers and it is inevitable some would malfunction. It IS a machine. They were built at Derby (RR), Crewe (RR) Glasgow (not sure, but I think it was a British government factory and not RR), Manchester (Ford of Britain), and by Packard in Detroit, Michigan, U.S.A..

You are making a mountain out of a molehill here, EKB. The history is written. Merlins proved to be the best engine of the European war of the liquid-cooled V-12 variety. You might as well accept it or you're trying to rewite history all by yourself. That usually doesn't generate a large numbers of supporters.

Did the Merlin have some issues? Of course, especially with continuous development happening. ALL wartime-developed engines had these issues, some less than others. Allison didn't have quite an many issues, but they weren't getting bombed, either. The Allison was some 2 years or so behind the Merlin development since we weren't on the edge of war. It was strong and robust down low but fell off about the mid-teens in altitude unless turbocharged. I think we mostly all know the issues with Allisons as this has been discussed at length in here. They were worked out, but it took time.

Meanwhile the ETO proved to be largely a high-altitude theater, probably due to European weather making many flying days into IFR conditions. When IFR, it is usually best to be higher than the mountains, so they ALL went up high except on clearer days or if it was unavoidable for some reason. The supercharger of the Merlin 2-stage units is what made the engine work so well up high. Sir Stanley Hooker helped that unit a LOT.

The Merlin DID have some issues. A P-51 (or Spitfire, etc.) would shudder and vibrate when the supercharger switched to high gear and the pilots simply throttled back and anticipated it. There was no fanfare when it shifted down to low range ... the manifold pressure just dropped. But all in all, it was a VERY good unit and outperformed the DB 601/3/5 despite being of considerably less displacement. The DB was a good engine, too, but also had wartime development issues, some of which were never completely solved.

Almost all of the Merlin's chief faults WERE completely solved. It still had some quirks, but has a solid reputation even 75 years later among people who still operate it. That lone says quite a lot.

At the Planes of Fame, we just changed one out with a long, reliable run as history. It lasted a LONG time, but I am not at liberty to post the hours. The numbers are private. Suffice to say it lasted MUCH longer than any wartime Merlin and ran very well for all that time, with few problems. I know maybe six - eight people who have had and are having that experience right now. Few problems in current service, a LONG time after it was built. The only DBs I know of that run do so only infrequently. The Merlins and Allisons fly quite regularly. We have one local here with a beautiful, very-late P-51 and he flies it almost every weekend ... with no trouble. He isn't the only local Merlin to fly very frequently, either.

You might be barking a lot about nothing much. Everyone who operated Merlins liked them in operation. They took a lot a hours to overhaul when that event came around, but active operations were good.

OK EKB I will play by your rules. The Merlin/V1650 was so unreliable why was the USAAF so stupid it used every engine it could get its hands on and even went so far as to build a new production line at Continental to make more V1650 engine's. Please explain why the USAAF wasted so much money and why they should have used a different engine. Please explain how using the Merlin/V1650 prolonged the war.

Many of the merlins problems as far as being taken apart number of fasteners etc probably stem from it being designed for RAF fighters. I doubt Rolls thought they were going to make more than a few thousand at most. A production of 168,000 units would seem like fantasy in the days when it was designed and production lines thought of. It should have been replaced by the vulture and Sabre but in effect outlived them both.