What was the problem with the allison engine?

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Continental started producing V1650s as well but were too late and the contracts were cancelled, as far as I have read they produced between 6 and 55 engines.
 
fastmongrel said:
Continental started producing V1650s as well but were too late and the contracts were cancelled, as far as I have read they produced between 6 and 55 engines.
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Obviously it was far better for them, in the middle of the war, to continue with the development of a motor they started in 1932 and had only yielded a handful of flight-worthy units.
 
EKB said:
Obviously true. But too many people have fallen back on nostalgia or compact technical histories of engines and airplanes and that is always misleading.
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Isn't that what you're doing here?!? You're arguing about Merlin reliability vs the Allison but not providing actual MC rates in comparative numbers and just posting quotes from combat reports that document individual situations.

I think Greg's post above says it all.

This old thread discusses aircraft reliability, I don't know if the links are still intact.

http://ww2aircraft.net/forum/aviation/reliability-ww2-fighters-10837-3.html

P-51 Maintenance...

Mustang! - Documents

I'll try to find some old sources that shows 8 AF aircraft abort rates and maintenance issues and IIRC there was nothing really glaring (with the exception of some P-38 squadrons - two engines mean 2x the maintenance) when you factored in aircraft numbers against hours flown.
 
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Well I didn't write that Merlin engines never worked as advertised. It that were true, very little would have been accomplished.

All top of the line aero engines had technical flaws—it's a matter of degree. If some people don't want to read about those problems that's fine with me.

The trend for Allied fighters in the ETO gradually moved to chiefly low altitude flying. The expansion of tactical air forces, anti-shipping operations, low level German raiders, and buzz bombs saw to that. By 1944 most of the high altitude fighting was done by heavy bomber escorts, but even they were assigned to strafing airfields, trains and other ground targets.
 
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I have some data on abort rates for the month of March 1945:

The 428th Fighter-Bomber Squadron was equipped with the Lockheed P-38J and P-38L, based at Florennes. The squadron recorded 662 sorties with eight aborts. The 1.2% abort rate in March was a record low for the 428th; their overall wartime rate for early returns was about 4%. Average time aloft per mission was about 2 hours and 25 minutes.

The 359th Fighter Squadron was equipped with the North American P-51D, based at Martlesham Heath. The squadron flew 404 sorties with 22 aborts. Average time aloft per mission was about 4 hours and 40 minutes.

The 365th Fighter Group was equipped with the Republic P-47D, based at Florennes and Aachen. The three squadrons amassed a total of 1,876 sorties with eight aborts. The average time aloft per mission was about 1 hour and 55 minutes.
 
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Since the initial charts comparing overhaul times was based on CONUS operations, I have two documents side by side comparing the noted overhaul hours against individual aircraft flying hours.



http://www.afhso.af.mil/shared/media/document/AFD-110331-045.pdf

If we were able to break out any Packard powered P-40s being operated in the US, this could give somewhat of a comparison. The V-1650 was over 100 man hours more to overhaul but I think you'll see there were more flight hours being put on them.
 
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Abort rate vs sortie flown factoring in flight hours will paint a good comparison.
 
Hey EKB,

It's OK to discuss the Merlin's faults or the faults of any engine or aircraft or even pilot. Many people in here will be glad to talk with you in here about faults that were uncovered. That isn't a problem. The Merlin was great engine that had a few issues that were more or less worked out. Let's just not call it a bad engine because they had to fix a few issues along the way. No piston aero engine of the time was without faults when it went from initial power levels to double in about 4 years.

Some issues were never fixed. One of the faults that vexes me is that Rolls Royce for some reason injects oil onto the reduction gears as they are moving in to mesh with each other. That is a mechanical no-no. Oil is incompressible. It adds a lot of completely unnecessary stress. The correct procedure is what the Allison did. They inject oil onto the gears as they come part from meshing and the oil has a chance to spread out and have excess throw off as it rotates around and remeshes. As a result, there were very occasional Merlin prop shaft failures. Not a lot, but some. The answer these days is to make a longer tube and run it around to the other side of the gear. Some do at overhaul; some don't.

I really don't like the way the valve seats are installed. You screw them in and tighten until the stem breaks off. Then you adjust the grind of the valve to match after you grind the valve seat. It adds time, but in service, it works fine. The hit comes at overhaul.

The center cam clamp is a tough nut to make. The rods are weak for hopped up engines, but are fine for stock power levels. You have to torque the cylinders every 25 hours (never on an Allison). But once you factor these things in, it starts and runs well, and lasts a good length of time between expensive overhauls.

Today, flying warbirds, the Allison is MUCH cheaper to operate and most warbird owners never get to 25,000+ feet since hardly anyone wants to waste expensive Merlin time flying IFR. They also mostly fly old fighters in severe clear weather. There is NO reason to risk an old fighter or a life in IFR weather today. If you need to get home that badly, take the airlines.

In cruise you can get an Allison down to some 39 - 42 gallons per hour (US gallons). The Merlins will get down to some 55 gph, and you CAN lean them further, but you run the risk of being too lean. So the Allison will cruise some 10 gph less, but that's not much of a savings if you fly a warbird with either engine in it, so most operators fly then at about a gallon a minute at cruise regardless of potential leaning capability. No risk of damage that way. If you're worried about a 10 gph difference, you can't afford to fly a warbird.

Most Merlins these days are seeing some 600 - 800 hours at overhaul time; some a bit longer. For Allisons, I know a few people flying then with 1,100 hours on them and going strong. But maybe these guys are just cheap. If I could afford either engine, I'd probably think about overhaul at about 700 - 800 hours whether it was running well or not. Props get overhauled every 5 years at a non-inconsiderable cost. Carburetors need it ever 5 years, too ... assuming they get flown enough. If they sit too long, the carb will require overhaul sooner.

A typical overhaul on a P-51 Hamilton Standard prop is about $100,000 USD. A typical carburetor overhaul for an Allison is about $5,000 USD. So yes, they are expensive to operate and overhaul but, what military aircraft isn't?

Notwithstanding all of the above, the Merlin is a great engine.

Wanna' talk warbird costs nobody ever sees? Try buying main gear tires for a Lockheed P-38! Try some $100,000 USD per set! Nobody makes them so, when they are needed, some tire manufacturer has to tool up and make a special run of 20 or so tires! That adds a LOT of non-recurring cost! And you get about 40 ladings on them on pavement. That means you are using up $2,500 in tire wear every single time you touch down! Any P-38 operator would love to fly from a grass strip!

Try finding wing slat bearings for a F-86! Some $5,000 per set and they used to be $20 per bearing!

The list is endless. Most people would cringe over the cost of a set of wheel pants for a Stearman Speedwing biplane, never mind the cost of other more mundane items. Nobody ever said flying surplus military airplanes was a cheap undertaking. At least, nobody since the 1960s anyway, when you could get a P-51 for $5,000, probably with a spare engine and a full tank of gas.
 

The reason for these aborts are ........?
 
EKB said:
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.
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Actually, the Merlin 61 was a limited production engine that was quickly superseded by the Merlin 63/63A with reinforced refined components that allowed, for example, increased boost pressures (+18 lbs). The Merlin 66 was improved over the 63/63A. Because R-R Packard continually exchanged information, it was Packard that introduced the two-piece cylinder block that was adopted by Rolls-Royce. In addition, the two stage V-1650s had different supercharger drives, different water pumps and different intercoolers, etc. (see attachment)


All anecdotal. It's very easy to blame the engine, but what did the engineering reports say about what caused the problems? The pilots may say one thing, but what counts is what the engineers back at base had to say. Something as simple as a faulty spark plug lead or foreign matter in oil or a faulty solenoid can cause all sorts of problems with a perfectly sound engine.

EKB said:
Obviously true. But too many people have fallen back on nostalgia or compact technical histories of engines and airplanes and that is always misleading.
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Dismissing Alec Harvey-Bailey's book on the Merlin as unreliable or misleading, because it's supposedly nothing more than "compact technical histories of engines and airplanes" is a cheap shot: Harvey-Bailey knew more about the developmental problems of the Merlin than anyone, and he knew what solutions were adopted. Making up an arbitrary rule that dismisses such a source...


Which shows that one of the great strengths of the two-stage Merlin was its ability to allow fighters such as the P-51 to operate as a high altitude bomber escort and a medium to low altitude attack aircraft; the Allison didn't quite make the grade in covering the gamut of high to low altitude roles.
 

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  • Packard as Aero-Engine Builder.pdf
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You'll need to visit the archives for that much detail. The early returns of the 359th Fighter Squadron were not out of line with other P-51 units using the Packard Merlin engine.

From March 1945 through April 1945 the 479th Fighter Group was equipped with the P-51D. During this period the group was based at Wattisham. They dispatched 2,110 sorties with 105 aborts. Average mission time was about 5 hours and 30 minutes.

From March 1944 through April 1944 the 363rd Fighter Group was equipped with the P-51B. During this period the group was based at Rivenhall and Staplehurst. They dispatched 1,677 sorties with 221 aborts. The total number of early returns was 268—but I did not count 47 P-51s that were recalled due to weather, on 18th March 1944. The group was also grounded for a week in the same month. Average mission time was about 3 hours and 40 minutes.

I think this reinforces my earlier post showing that the P-51B was a highly defective airplane in the spring of 1944.
 
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EKB said:
If that is your belief then prove it.
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You started with a diatribe against the engine but now your saying

EKB said:
I think this reinforces my earlier post showing that the P-51B was a highly defective airplane in the spring of 1944.
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Oh and I dont need to prove anything you started this particular horse its up to you to find solid proof that doesnt consist of a few selected quotes that when taken out of context reinforce your beliefs. I know the Merlin/V1650 had faults and I can happily off the top of my head without recourse to google list several dozen but I dont feel the need to knock anything to try and prove my belief that the people at the pointy end of WWII didnt make a mistake.

You are trying to prove a theory so its up to you to provide a proper well laid out set of proofs with a list of sources. I dont need to do anything but react to your claims I have no need to prove my claims because I am claiming nothing.
 
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