Western engine reliability

[Milosh]

Wow. I asked a simple question and you talk about an attitude problem! Maybe you need to look at yourself for a while?

So, do I have to assume You made those piece of papers up or do you have some kind of "source"?

Did you miss the 'WWII Aircraft Performance' source in Post#34?

 

[Aozora]

Wow. I asked a simple question and you talk about an attitude problem! Maybe you need to look at yourself for a while?

So, do I have to assume You made those piece of papers up or do you have some kind of "source"?

You can assume anything you like. Members of this forum are entitled to post documents, information and even material from websites in good faith, without having to always explain their authenticity or provenance except where there are compelling reasons to believe that the material isn't cocher. A compelling reason could be that you or someone else has seen the original document/material and knows and can prove that the one presented is faked.

Why Good faith? Because long experience has shown that otherwise interesting and informative threads rapidly deteriorate into bitter, angry arguments over the authenticity of all such material as soon as someone starts questioning the "authenticity and provenance" of someone else's contribution: with the large numbers of knowledgeable and informed people on this forum, altering or presenting a bogus document is risky, because chances are someone will have accessed the original or has material which exposes the fake. You have been warned by a moderator to show more respect - take his advice.

 

[DerAdlerIstGelandet]

I think the main issue affecting German reliability at the end of the war was the spiralling QA that was bound to lead to increased down times for the aircraft. everything was affected, not just aircraft. Thats not a poor reflection on German engineering, its just an acknowledgement that errors go up as the qulaity goes down, and quality was bound to go down as Germany spiralled out of control and into defeat.

I can agree with this. Between slave labor and a lack of skilled labor (With most men of fighting age on the front, this was bound to happen.), you are going to have quality issues. Add that to the fact that they were having to produce large quantities at a very fast rate.

spiralling, as in descending uncontrollably

Slave labour would contribute to that. As would the undiscriminating draft that saw highly skilled workers in key industries drafted

I see we actually agree completely....

Saying the same thing.

I predict he will corner one of us, probably the least well informed (that would be me), have a little rant, be extremely rude, deny everything and say while he posted good evidence, we have posted nothing and in particular say the RAF and CW contributed virtually nothing to the allied victory and then stomp off.

i hope he proves me wrong

Considering he has not done it yet, why make a statement that will certainly put flame on the fire and instigate it?

Seriously?

You guys love confrontations. You claim otherwise, but you all do it. Very tiring, very old...

Why Good faith? Because long experience has shown that otherwise interesting and informative threads rapidly deteriorate into bitter, angry arguments over the authenticity of all such material as soon as someone starts questioning the "authenticity and provenance" of someone else's contribution: with the large numbers of knowledgeable and informed people on this forum, altering or presenting a bogus document is risky, because chances are someone will have accessed the original or has material which exposes the fake. You have been warned by a moderator to show more respect - take his advice.

Long experience?

How long has your experience on this forum been? Were you a member before with a different username????

 

[GregP]

Getting back to it a little late but parsifal, I agree with you on the spiraling QA. I can tell you from experience that the Japanese radials are VERY reliable and very well made ... at least the Nakajima Sakae 21. Ditto the props that were license-built Hamilton Standard units. The Japanese HAD the license and were legally entitled to make the props. Their own prop designs weren't bad, either. The airframes are well-constructed and well designed using their own criteria. In the USA, we wanted more pilot and aircraft protection, but the Japanese workmanship is very good ... no complaints

The Me / Bf 109 was well made and stout, and whether it be a Spanish Ha-1109 / 1112 or a real Me / Bf 109, the workmanship is excellent. I have seena real Fw 190 and it, too, was well made.

Personally, I haven't see any short-life engines or bad workmanship in the palnes that have survived. Perhaps they bad ones simply didn't survive ... kinda' makes sense to me anyway.

About the infighting in here ... I apologize to anyone I have offended and hope to be more tactful in the future. I confess that when I am attacked, I tend to "fire back." I think most of us do that. Human nature. Sometimes the reply doesn't look so good in the morning and I try to say that when I notice it. I'd MUCH rather discuss and trade information than insults. If I don't agree with a particular point, it is not intended as an insult, just a simple, "I think it might be otherwwise and here is why I think that." Sometimes it doesn't come across quite that way, does it?

At least we all have a common interest in WWII aviation. That makes us all interested in the same subject ... and SHOULD be a source of a desire for interchange, not argument. OK, off my soapbox and back to an Old Frothingslosh Ale, the pale, stale ale with the head on the bottom.

 

[DerAdlerIstGelandet]

About the infighting in here ... I apologize to anyone I have offended and hope to be more tactful in the future. I confess that when I am attacked, I tend to "fire back."

To everyone:

Don't, all it does is stoke the fire and make it worse. It actually ruins threads, because the informative exchanges tend to stop then. Just step back, let us know, and let us Mods take care of it. Believe it or not, we are watching. Sometimes we miss things and sometimes it might take a while because we have lives outside of the forum as well (shocker huh? ).

As for the above situation, that I commented on above.

Why even say something like that?

1. It has nothing to do with the thread.

2. It only stokes the fire.

3. It is counterproductive.

4. If anything, all it is doing is instigating a fight. If the said person was not going to fight, he will do so now, because he is offended by the post.

If anything, it sounds like the person was trying to entice him into a fight. Almost daring him to do so. Why? Are we adults here? Sometimes I wonder?

 

[GregP]

Well said DAG (long name ...) ... perhaps I can emulate your poiltical nature and not "fire back," perhaps not. I'll try ...

 

[parsifal]

Considering he has not done it yet, why make a statement that will certainly put flame on the fire and instigate it?

He has not shown much restraint to date. ignoring him is like appeasement....hoping he will be nice. My comment was designed to try and make hime think a bit. Wasnt deswigned to inflame him, but Im not prepred to watch him pedal his wares unchecked either. Maybe I should

Seriously?

You guys love confrontations. You claim otherwise, but you all do it. Very tiring, very old...

You could not be more wrong in my case. I loathe confrontation. But neither wil i roll over and play nice to some of the attrocious and outrageous things that are said in this place. You have known me for five years now Chris. Im not perfect by a long shot. I have a limit to patience. I admit all that. usually I am the one trying to promote patience and tolerance. And some people absolutely detest that. which is why they come after me so many times.

And no, i am not defying you, or looking to get my head blown off. Im not that silly. If i could get peace in this place, without having to sell my soul for it, trust me i would do it. And that doesnt mean "if i could get my way all the time i would be happy"......

 

[Aozora]

Long experience?

How long has your experience on this forum been? Were you a member before with a different username????

Not long on this forum, but I have experienced other forums where threads got nasty once people started the "you tell us the provenance of that document or else" crap, plus I have had a look around here and, while finding found the likes of this thread , my overall impression is that good faith over posted documents etc is expected - or am I mistaken? And, no I have never been banned from any forum - like parsifal I loath wasting my precious leisure time on stupid, pointless arguments: that said I also value the right to take the time and trouble to post relevant material without having someone else demanding that I prove their authenticity and provenance - As it is please note I usually post my sources.

You'll have also probably noticed that us "Colonials" (from OZ and NZ) can be blunt and direct - that's just the way we are.

 

[Tante Ju]

Apparently the thesis behind this thread was the terrible record of Allied aero engine reliability which,

Made no such statement.

according to Tante Ju, meant that the average life expectancy or TBO for all engines by 1945 was about 50-60 hours.

Made no such statement. Most of these engines TBO we do not know, thread is open to find out what was realistic TBO, as said. Western engines did not last more than about 50 hours in Soviet service - fact shown. This may be due to conditions, as shown validly - but then comparison and claim was made with Soviet engines 'relatively poor' TBO times - is it not equally valid that those Soviet engines were operated under same primitive conditions of Eastern Front airfields? Serviced by same mechanics? Filled with same oil? Word disengenious can be equally applied.

Soviet pilot here says for example.
Interview with Vladimir Mukhmediarov

'I finished the war on Yak-9U with M-107 engine. Its engine life was 50 hours only. There also were a lot of accidents with this airplane. At high power connecting rods would break.'

So explain me please how 50 hours from Merlin 46 engine is different from 50 hours from M 107 engine. Operated by same skilled mechanics, using same oil, under same conditions.

The Merlin was cited as was the Griffon, Sabre and early Allisons ; funny thing is in Europe these engines (apart from the original Allison engined Mustangs) were using 100/150 grade fuel and high boost on operations and experiencing no problems with unreliability or low TBO

Serious engine troubles during testing with high power - shown. An example of Griffon 65 engine lasting between 40-60 hours post war was shown. If you have other practical figures for Griffon engine - show. We all learn...

Also reports made by Allies themselves differ of your opinion.

3. At the time the 150 grade fuel was first used all three fighter types listed above were in operational use by this Air Force. Shortly after June 1 P-38 units were re-equipped with P-51 type aircraft so that experience with 150 grade fuel in P-38 aircraft is limited. Gradually, conversion of P-47 outfits to P-51’s took place during the Summer and Fall of 1944, and as of approximately 1 November only one P-47 group remained in this Air Force.

4. Maintenance difficulties can be summarized as follows:

a. P-38 (V-1710 Engine).

Spark plug leading was increased. The extent of this leading was such that plug change was required after approximately 15 hours flying. This conditions was aggravated considerably by low cruising powers used to and from target areas, while trying to get the maximum range possible. It was found, however, that regular periods of high power running for a minute of two in most cases smoothed out any rough running engines unless the cause was other than leading.

b. P-47 (R-2800 Engine).

Spark plug fouling was the only maintenance difficulty encountered during the period in which 150 grade fuel was used. Spark plug life was reduced by about 50%, the same low power cruising as described above being the principle cause for the extra fouling. No deleterious effects on diaphragms, fuel hose or any other rubber of synthetic rubber materials were noted.

c. P-51 (V-1650 Engines).

The same type of lead fouling as described in a and b above happened in the case of the P-51 except that is was probably more serious than in either of the other two types. Using 130 grade fuel with 4˝ cc. of lead, the average operational P-51 could last 5 missions (roughly 25 hours) before the fouling required plug change. With 150 grade fuel containing 6 cc. of lead, 10 to 12 hours, or normally 2 missions, was the average length of time between spark plug changes or cleaning. At various times in the six months of operation of P-51 aircraft on 150 grade fuel many other maintenance difficulties were attributed to the fuel, but final analysis proved that the only real effect of the fuel was the lead fouling. Some units maintained that they had some deteriorations of seals, but this was not borne our throughout the command, nor was there any concrete evidence that it existed in the units.

The excessive fouling of spark plugs usually exhibited itself in roughing up of engines after a couple of hours of low power cruising. Periodic bursts of high power in most cases smoothed the engine out. However, if the engine was allowed to go too long a period without being cleaned out, the accumulation of lead bromide globules successfully withstood any attempts to blow them out.[/b] In some instances, long periods of idling while waiting for take-off and a failure to use high power on take off resulted in loss of power during take-off run and in some cases caused complete cutting out with subsequent belly landing. The cases of cutting-out on take-off definitely attributed to excessive fouling were comparatively few, although numerous enough to list it as an effect of the extra lead.

As a result of several months operational use with the fuel, an SOP – designed to reduce power failures on take-off, leading troubles in flight, and other things which were causing early returns and abortive aircraft – was published. This is inclosure no. 1. Almost immediately after this section published this SOP practically all of the troubles then existing ceased, although it was necessary to change plugs after each two missions or thereabouts.

In an effort to reduce the lead fouling, tests were conducted by this section with 150 grade fuel containing 1.5 T’s of ethylene dibromide. A total of about 120 hours was run by this section and the three squadrons given the “Pep” fuel for accelerated service tests. The results of these service tests showed a considerable reduction in lead fouling with no apparent effects otherwise. As a results, all fighter units of the Air Force were put on Pep fuel late in January 1945. About thirty days thereafter a sharp increase in valve trouble was experienced with the V-1650 engine. Inspection of engines at overhaul revealed that the hydrobromic acid was eroding the silchrome valve seat inserts to such an extent that after approximately 100 hours of operation all the valve clearance was gone. This 100-hours is the minimum life some engines going 170 to 180 hours before this condition prevailed. There are no other deleterious effects of this fuel noted. As of 1 April 1945 fighter units of the Air Force returned to the use of 100/150 grade fuel containing 1.0 T of ethylene dibromide.

Last paragraph is interesting as it cites practical TBO 100 to 180 hours of life with 150 grade fuel (1.5 TEL) before completely destroying valves and requiring engine change.

Merlin 66: 9,268 hrs; over 6,000 hrs by two squadrons alone. (Tante Ju cites worn out Merlin 45s in Russian service.)
Griffon 65: 2,000 hrs; 610 Sqn 1,119 hrs. (Tante Ju cites 1 preliminary test and a post war test with no explanation given as to the circumstances behind the failures...)
Sabre: 2,300 hrs at +11 lbs; reducing to +9 without V-1 threat. (Tante Ju cites 1 test and Eric Brown's experience.)

Soviet Merlin 46s were not worn out. They did not last more than about 50 hours - yes this 50 hours includes familiarisation, as usual.

Two Squadrons contain about 45-50 aircraft in British practice. 6000 / 50 = 120 hours per plane. What is not known - how many engine changes in meantime?
610 Sqn 1,119 hrs Griffon 65 - about 46 hour per plane in avarage (note post war trial Griffon 65 lasts about this long before engine change is needed...). How many engine changes in meantime?

We must not lose focus on question. What was practical TBO of Western engines under field conditions? Any source Welcome. We all learn.

 

[Tante Ju]

First I like to ask for excuse to take so long to answer thread. Different committments..

So, in order.

Tante JU, this is very disengenious of you.

1. The Merlins in the Russian Spitifres were neither new nor were they maintained to the same standards as in the UK. You have no idea how much time the engines had on them before they went to the Russians.

Source posted shown that they were repaired before sent. In any case, engine life time is not difficult to find - these are precise written in engine log every time (see Griffon source). When Russians say 50 hours, its 50 hours in engine. Its logged in book, simple as that everywhere, since overhaul or built, engine run that much, as recorded everywhere.

2. The V-1710s in Russian P-40s experianced a similar situation

No, 50 hours in book is 50 hours. It seems Russian P-40s Allisons were sensitive to oil condition, dust and maintaince. But no more different than a Yak.

My point is, if you want to dicriminate Allison lifespan because it was Russian mechanics who serviced them, with Russian oil, in Russia conditions, why are some still insists to make comparison with Yakovlev

Allison serviced in good condition vs a Klimov engine serviced in bad conditions? Sure Allison will last longer, it is very correct to point this out by GregP, SR6 and others, but it is everything but a fair comparison, when you want to rule out P-40s in the desert, because they were in harsh conditions (side point - aren't war fighters supposed to be and need to be capable of operated in such conditions?) but at same time it is somehow fair to cite bad TBO for a German/Russian engine with bad supply in the end of the war, for a Russian engines with poor sandy conditions in the Steppe and winter reachinmg -50 Celsius? How fair is it to rule out P-40's cite TBO in North Africa because 'sand is bad for engines you know' but be entirely fine with citing TBO in North Africa for Axis engines. Take for example DB engines in mid war. I am not sure how much pracitcal TBO was, I read about 100-150 hours, but these TBOs were achieved where DB engined planes (109, 110 etc) were deployed to: Africa and Russian steppe most of the time.

I am sure P-40s lasted longer in nice hangers in mainland USA than Yakovlevs near winter Leningrad, or Spitfires in Crimea. But what is point in such comparisons?

3. You're using test flights made at high boost with 150 octane engines as representative of regular combat operations. Griffon 65s at +25lbs, Sabre IIs at +11 lbs, Merlins at +25 lbs. Put more stress on these engines and of course the failure rates are going to increase.

I agree at high power, boosted engines etc. failure rates are going to increase. This is whole point of contention - Shortround claims many hundred hours for these later war engines, which seems very very unlikely in view of evidence posted and common sense. But we need to find accurate data to find this out.

4. You're pointing to specific examples and then generalising into a trend. This is dangerous territory.

I am not generising. I am collecting information to find out what the truth is. Certainly much less dangerous to do that than simply saying: Western engines were much better. Without any source. Contrary to source.

How about some engines in regular service, well maintained by the airforces of the country that built them? How about more than just a few individual examples?

That is exactly what I am hoping to find, as said in first post. Regular engine lifespan, in field. Not manufacturer's selling brochures, with many many disclaimers like R-R papers.

'Oh our engines last 240.... provided: 1, We only speak 1 in every 3 engine 2, no sand comes near to them 3, high power we note in brochure is rarely used etc.'

Such conditions make TBO figures paper like, as no engine is operated this way in combat aircraft. You cannot compare R-R paper figures with this diclaimers burdened to practical field conditions achievable, yet some do.

The R-2800 manual from 1942 suggest a conservative TBO of 350-400 hours. Rolls-Royce suggested a TBO of about 240 hours for the Merlin, but only around 30% of engines actually reached this figure. In service Packard V-1650s had a TBO of 110-180 hours in the Mustang in Nth Africa/Italy.

Can you post these sources please? I am not doubting it, but would like to see.

An interesting read, if somewhat long, on the Axis History forum, from 2006. Kurfurst and Huck tried exactly this approach and see how far it got them:

Axis History Forum • Reliability of aircraft engines

Thank you very interesting thread indeed. Lots of noise from everyone, and I am not sure if EKB there did not have an agenda. Still, information is useful, from both parties. I see there were some cases of R-2800 lasting about 700 hours, other time, only 80 hours. Two opposites of extreme ends.

Rolls was saying in 1939 that a fighter Merlin could go 240 hours and Bomber engine 300 hours. By 1944 they were saying 300 hours and in 1945 360 hours for the fighter engine. Bomber engine life was supposed to be 360 hours in 1944 and 420 hours in 1945. Even if we cut that to 60% for the average that would be 180 hours in 1944 for a fighter engine and 216 hours for a bomber engine. 3 1/2 to 4 times what is being bandied about.

Yes, selling brochure figures.. Rolls was bandied about its engine could go 240 and 420 hours Merlin TBO but it seems they did not. In service shown 50 hours they lasted. I am will to see other figures, but none shown since.
Griffon lasted about 50 in Canada. Allied reports show after about 100 hours, valve is destroyed with high TEL fuel.. was Rolls saying 420? Then what? Engine did not last that long in service.

Great strides were made in metallurgy and testing during 6 years of war. Post war most of the R&D went into long life rather than power but it seems a bit strange that engines that could only give 50-60 hours of life in 1944/45 could give hundreds of hours of life if not over 1000 hours in post war airliner service. Not so strange if the engines were giving 400-600 hours in the last year of the war.

Show me source that these engines lasted 400-600(!!) hours in the last year of the war practice please.

This sounds very funny. Since we build Allisons, we have the books and the records of overhaul ... and we talk with and sell to (mostly used to sell to these days) former WWII pilots who have Allison, Merlin, P&W, Wright, etc. - powered aircraft from WWII. For instance, we did the engines for Lefty Gardner and all the flying P-38's except the Red Bull unit.

According to our information, wartime TBO for the Allison was 250 - 400 hours depending on the dust conditions. Wartime TBO on Merlins was 200 - 300 hours depending on dust conditions. In typical wartime forward area airstrips, typical TBO was 250 hours for both.

Thank you for your posts, very useful, fair and insightful IMHO.

Do you have exact sources of conditions, and could you post them please if I ask?

Engine reliability depends almost entirely on the use and maintenance of same. Dito the propellers and guns.

Very much agree. IMHO one of most important things to learn and remember from this discussion.

 

[Tante Ju]

Merlin 266 was appearant less reliable than British produced engines. C. Shores: 2nd TAF volume II, page 342.

 

[Tante Ju]

I think this concludes and closes thread part of discussion deciviely.

V 1650 avarage TBO: 133 - 154 hours for example.

So much for brochure figures...

 

[parsifal]

I stand corrected

 

[DerAdlerIstGelandet]

He has not shown much restraint to date. ignoring him is like appeasement....hoping he will be nice. My comment was designed to try and make hime think a bit. Wasnt deswigned to inflame him, but Im not prepred to watch him pedal his wares unchecked either. Maybe I should



You could not be more wrong in my case. I loathe confrontation. But neither wil i roll over and play nice to some of the attrocious and outrageous things that are said in this place. You have known me for five years now Chris. Im not perfect by a long shot. I have a limit to patience. I admit all that. usually I am the one trying to promote patience and tolerance. And some people absolutely detest that. which is why they come after me so many times.

And no, i am not defying you, or looking to get my head blown off. Im not that silly. If i could get peace in this place, without having to sell my soul for it, trust me i would do it. And that doesnt mean "if i could get my way all the time i would be happy"......

You know I have nothing but respect, but all you are doing is instigating at the moment.

I am sorry but I will not tolerate instigating, just like I wont tolerate rude behavior. Save both those those things for the school lunch room.

How about you let us do out jobs, and not make it more difficult by adding fuel to the fire.

 

[Juha]

...Soviet pilot here says for example.
Interview with Vladimir Mukhmediarov

'I finished the war on Yak-9U with M-107 engine. Its engine life was 50 hours only. There also were a lot of accidents with this airplane. At high power connecting rods would break.'

So explain me please how 50 hours from Merlin 46 engine is different from 50 hours from M 107 engine. Operated by same skilled mechanics, using same oil, under same conditions...

Firstly, M-107 is known to have more than its fair share of problems, on Merlin. again, look my message #7, they didn't have manuals nor anybody to teach them on Merlins.

Juha

 

[Tante Ju]

So how much time Merlin 46 had in British service before requiring overhaul?

 

[Juha]

So how much time Merlin 46 had in British service before requiring overhaul?

I don't have any good source at hand but from recent messages here:
http://www.ww2aircraft.net/forum/av...s-bf-109-k-4-vs-la-7-vs-yak-3-a-13197-26.html

…
01-15-2013, 06:26 PM Shortround6

"…Engine "life" was not a guarantee the engine would make it that long. It was the MAX life of the engine, If the engine actually made it that far it was supposed to be pulled from service at that point and over hauled and NOT run any further.

Rolls Royce claims that from 1942 on 35% of engines passing though repair organizations had reached their expected service life. They also claim that the average life of the engines passing though repair organizations from 1942 onwards was about 60% of the "nominal" life for the type.

While the repair organizations couldn't count engines lost in service they were repairing some battle damaged and crash damaged engines."


http://www.ww2aircraft.net/forum/aviation/western-engine-reliability-35560-2.html

…
01-15-2013, 09:51 PM Shortround6

" Rolls was saying in 1939 that a fighter Merlin could go 240 hours and Bomber engine 300 hours. By 1944 they were saying 300 hours and in 1945 360 hours for the fighter engine. Bomber engine life was supposed to be 360 hours in 1944 and 420 hours in 1945. Even if we cut that to 60% for the average that would be 180 hours in 1944 for a fighter engine and 216 hours for a bomber engine. 3 1/2 to 4 times what is being bandied about."

I would make a quess from 144 hours to 180hours, if I must give one figure I'd say 155 hours on average.

Juha

 

[Tante Ju]

Thank you. It is a pity there is no such report available to us than American above.

Perhaps Guassian curves can be applied to brochure figures, with known 30% success...

 

[Shortround6]

And so much for the claim of western engines lasting 50-60 hours.


Companies whose "brochure" figures don't at least come close to reality tend to get little repeat business and go out of business fairly soon.

The soviet engines, which you seem to think were a close equal, had an awful lot of trouble making 100 hours on test stands.

on the M-107

"According to the plans, the engine's servicing interval was to be increased to 100hr by 1 May 1941. Series production was to be started, and 2000 M-17s were to be completed by the end of the year. However bench testing revealed vibration, oil leaks which lead to decreased oil pressure, failure of the spark plugs, breakdown of the crankshaft bearings, and leaking of the gas seals. Overheating was also a problem. After some refinement the M-107 successfully passed it's its 50hr test. During 1941 twenty-nine engines were manufactured, these being used for various tests. Series production started in 1942. Certain versions were manufactured until 1948 at factory No. 26 in Ufa. ...... Owing to drawbacks in the design, manufacture was halted several times (in September-December 1945 and April-October 1946). In total 7,902 M-107/VK-107s of different versions were built."

"M-107 (M-107P) The first series-production version of 1941. Power rating 1,300/1,400hp, weight 765kg (1,687lb). This version suffered from failures of con-rods, pistons and crankcases. During 1941-42 686 M-107s were manufactured."

"M-107A VK-107A) A 1942 version with variable-incidence blades (Polikovskiy's blades) in the GCS guide vanes. Power rating 1,500/1,600hp, weight 769kg (1,695lb). This engine was in series production form the endo fo 1942 (forty-one were built in 1942). According to the plan, engine service life was to be brought up to 50hr by mid-November 1942, and up to 100hr by the end of the year. In fact, its service life reached 50-60hr. During December 1943-January 1944 the VK-107 was flight tested in a Yak-9U fighter, in April-November 1944 in a Yak-3, and in April1944 in a Pe-21 high speed bomber prototype. The VK-107 remained in production until 1948........In 1946 the reduction gear ratio was changed, the maximum rpm was limited and an additional oil oil pup was fitted ( similar to the one used on the VK-108 ). These modifications allowed the engine to demonstrate a 100hr service life during the check tests."

from Page 143 "Russian Piston Aero Engines" by Vladimir Kotelnikov.

This has been said before but it seems to NEED repeating. The "brochure figures" are maximum engine life NOT minimum or guaranteed.

You seem to be implying that the western engine makers were indulging in a dishonest practice.

What they were saying is that after the "brochure" life figure the chances of inflight failure are going to go up and they are strongly recommending the engine be taken out of service at this point regardless of how well it seems to be running or what points of wear that can be seen without dismantling the engine, show.

Now if you are buying engines for an airline or airforce and Company "A" says the MAX life of their engine is 240 hours and company "B" says 150 hours and company "C" says 100 hours which one are you gong to buy? Maybe company "C" is being more honest and 90% of their engines make it to 100 hours. If 1/3 of company "A"s engines make to 240 hours and the"average life (including prop stikes) is 150 hours how far ahead are you?

If company "A"s engines turn out to have a life under 100 hours Company "A"s reputation will be ruined. Reputation was very important to Western companies because they often "sold" (took deposits on) new engines well before they actually flew. Or airframe makers designed planes to use "new" engines based on promised performance and initial drawings for installations. Stick them with non-performing engines too many times and they won't use the unreliable company's engines in future designs.

 

[Tante Ju]

And so much for the claim of western engines lasting 50-60 hours.

They did last 50-60 hours in Soviet service. Same as VK 107 - which was a poor engine no doubt for reliability.

Note that even in much more favourable conditions than Soviet front, V-1650 (Merlin) did not seem to last more on avarage than 130 hours. The vast majority, say 80-90% was performed at low cruise ratings, this certainly helped to prolong engine life - 8 hour sorties at low powers escorting bombers did not put nearly big as strain as Soviet practice of flying max. 1 hour sorties near frontline as fast as possible.

BTW Merlin also had 'awful lot of trouble' completing 100 hour tests on bench. Well known from history.

Griffon did last 40-60 hours in post war Canadian service it seems.

I am curious how long Sabre lasted. I think 40 would be very generous assumption, given plague history of engine.

And as much as you like kick Soviet engines for developing about 50% of their brochure figures in service, I wonder how that compares to Allisons 700+ hour claims vs. 150-180 hours in practice..

PW engines seems best, though statistics may be somewhat unfair as many had duel (fighter-bomber) applications, and bomber use tends to improve statistics.