P-51 Mustang Vs. Me 262

[drgondog]

Guys, all great info, but remember all this doesn't preclude the fact that all these early jets were not great "accelerators" and flew into combat with high power settings. The Meteor was fast for its day but wasn't a great "roller." The Vampire, had a slow responding engine typical of the period, but built up speed quicker because of its lighter weight and was more maneuverable - but here's the key - the amount of energy these aircraft could maintain and develop during combat. The extra 5 or 6 mph difference in speed is not going to mean too much if one aircraft can use energy to accelerate away.

dead on Joe...I was nodding off in the discussion - plus the niggling detail that only when alerted (and capable) did max speeds even become a factor. The second guy to know he is in a gunfight often holds that as his very last thought.

 

[FLYBOYJ]

Thanks Bill - glad we woke you up!

 

[Erich]

funny I thought this was the contention between the Schwalbe and the Stang and nothing to do with the Meteor. why the F*** does a thread of this nature and interest always get off-topic

 

[riacrato]

I think in reality the Me 163 was a rocket-plane that regularly dissolved its pilots in T-stoff * and C-stoff

Granted the Sten was not pretty - and the MP40 was nicely machined and fitted.

Wrong.

And on what you wrote about jets. You see, by now everyone with decent interest in jet engines knows well enough about the relative advantages of centrifugal or axial compressors. And it is ****ing common knowledge that none is definetly superior to the other or else they were not both used until this day. But no, always someone has to make it look as if his country's engine concept choice was inherently superior.

That posting is representative of many articles/postings stating that the 003 engines were lousy wtih respect to reliability while the 004s were much better, they still lasted a very short time. Again, the point is about reliablity. And engine that lasts 20-25 hours is not reliable. Engines of today routinely get 10,000 hours of flight time. That is a reliable engine. 20-25 hours is not reliable.

First of all the 003 was abandoned for the Me 262 relatively early on simply for the fact that it was clear the engine was nowhere near as close to being serial production ready as the Jumo. Only the very first prototypes used the 003. And it wasn't "lousy" it was simply not ready. The J33 also had lousy reliability in pre-production. this is the first jet generation afterall. When the 003 entered true service with Ar 234 and He 162 it showed good reliability given the circumstances.

And todays engines have to last for ages, because that's how long the plane lasts. Now how long will a Me 262 in spring of 1945 last on average? We have really been repeating this subject over and over again. And there's a Me 262 vs Meteor topic right on this page.

 

[timshatz]

We have been close to this subject for a while and the point was about the reliability of the engines. In the spring of 1945, a Merlin was far more reliable than the Jumo 004. Hence the point about the Mustang being preferred over the 262 due to reliablity and maturity of the design. The Mustang had a more reliable and mature engine.

 

[Colin1]

And todays engines have to last for ages, because that's how long the plane lasts.

Now how long will an Me262 in spring of 1945 last on average?

Your first comment doesn't look right to me, I can't put my finger on it...

...and your second comment is probably what is confusing me; what are you saying has changed in aircraft maintenance between Spring 1945 and now? Or even air combat, in modern times we have less aircraft being shot at by far more accurate weapons (not all of them other aircraft), what are you saying has changed?

 

[riacrato]

The situation of a modern airforce is very different from LW 44-45. The reality was that from late '44 onwards the average LW fighter aircraft survived no more than a few (5? 10?) missions before being shot down in the air or on the ground, crash landed or similar. So it makes a lot of sense to have an engine lifetime in the vicinity of the total aircraft's lifetime. Sure the Jumo 004 is borderline. But you have to make a decision: Either have an expensive, normal-lifespan engine which will be a lot of money blown out the window if shot down (as in Jumo 004 A) or take the cheap route of the Jumo 004 B. I'd take the latter any day given the choices.

 

[Colin1]

... So it makes a lot of sense to have an engine lifetime in the vicinity of the total aircraft's lifetime...

In the Luftwaffe's case, I think this has more to do with unfortunate coincidence than intelligent design

With regards to a modern airforce, I don't think an F-15 sitting on the apron at Holloman AFB in 2010 has the same engines it rolled out of Long Beach with in 1974. I don't know that for certain but it doesn't sound feasible so the statement 'engines have to last because that's how long the plane lasts' feels limited in accuracy to me.

 

[FLYBOYJ]

Actually the F-15 was built in St. Louis and yes, more than likely any given F-15 flying today has seen at least a half dozen different engines in its lifetime, depending on the flying hours.

The minimal life time of German turbine engines during WW2 existed because of material and the implementation of new technology and that was typical of ANY turbine engine of the period. British and US made engines were lasting a bit more because of materials and better quality control, but that's not taking anything away from what Germany accomplished with its first turbine engines. In reality, reliability in ANY turbine aircraft built between 1944 and 1946 could be questionable and if I was flying one I'd make sure I had a good parachute, say prayers during the first 500' of takeoff and make sure I was way ahead of the airplane during landing.

Now, let's get this thread back on track....

 

[parsifal]

something I only recently found out. The Vampire used the same plywood laminar construction as had been developed for the Mosquito, though more metal was used in the Vampire. This mixed wood/metal construction was continued in both the Venom and Sea Venom types, which were not retired until 1967 in the RAN.

The Sea Venom had an initial climb rate of 5900 feet per minute. Does that not suggest superior accelaration, I assume that climb rate and accelaration are related in terms of their power demands?

 

[FLYBOYJ]

something I only recently found out. The Vampire used the same plywood laminar construction as had been developed for the Mosquito, though more metal was used in the Vampire. This mixed wood/metal construction was continued in both the Venom and Sea Venom types, which were not retired until 1967 in the RAN.

The Sea Venom had an initial climb rate of 5900 feet per minute. Does that not suggest superior accelaration, I assume that climb rate and accelaration are related in terms of their power demands?

All true...

 

[riacrato]

In the Luftwaffe's case, I think this has more to do with unfortunate coincidence than intelligent design

the Jumo 004 A had a significantly longer lifetime than the B, that is fact. The B was a trade-off solution between material availability and service life.that is also fact.

With regards a modern airforce, I don't think an F-15 sitting on the apron at Holloman AFB has the same engines it rolled out of Long Beach with in 1974.

And I never said so. I said with a plane lasting years it makes sense to have an engine lasting a few years (didn't say it has to be 1:1). With a plane whose lifecycle is measured in weeks it doesn't make sense to have its engine lasting for years. Disprove me.

 

[FLYBOYJ]

With a plane whose lifecycle is measured in weeks it doesn't make sense to have its engine lasting for years. Disprove me.

The point here is despite an airframe with a lifecycle lasting weeks, no one in 1945, allied or axis was building a turbine engine lasting years, even if they wanted to.

 

[timshatz]

The point here is despite an airframe with a lifecycle lasting weeks, no one in 1945, allied or axis was building a turbine engine lasting years, even if they wanted to.

I'm with you on the engine life Flyboy. Any bird with a lifecycle on the engines of 20-25 hours is going to make me VERY nervous. Jeez, if that's the average, what's the deal with the substandard engines that snuck by QC.

Matter of fact, I don't think I've ever met a pilot who wasn't at least "very sensitive" to whatever his engine was doing. And that's on a 2000 TBO Lycoming.

 

[thrawn]

I'm with you on the engine life Flyboy. Any bird with a lifecycle on the engines of 20-25 hours is going to make me VERY nervous. Jeez, if that's the average, what's the deal with the substandard engines that snuck by QC.

Matter of fact, I don't think I've ever met a pilot who wasn't at least "very sensitive" to whatever his engine was doing. And that's on a 2000 TBO Lycoming.

Some people are mixing expectet engine life time with reliability.
It is right that an unreliable engine has an shorter average lifetime than an reliable. But to assume a short life engine is unreliable is simply wrong.
If we assume a gaussian normal distribution with the peak at 20 hours engine life, the variance (width of the bell) is the factor to determine reliability. This could be small or wide. The average life time will be the same. So if only very few engines last significant longer than 20 hours, there will be very few engines which will last significant shorter. Thats a reliable engine. For an unreliable one its the other way around. But we dont know the variance and so we cant judge reliability. Engine life time alone is meaningless.

In fact, one of the problems which reduced the life time on the jumo 004 was the blade lengthening because of low heat resistant materials. But this lenghtening is a very steady process, which is controllable.
Of course this is not the only problem of the Jumo 004. And so its difficult to say it was reliable or not.

regards

thrawn

 

[timshatz]

Some people are mixing expectet engine life time with reliability.
It is right that an unreliable engine has an shorter average lifetime than an reliable. But to assume a short life engine is unreliable is simply wrong.
If we assume a gaussian normal distribution with the peak at 20 hours engine life, the variance (width of the bell) is the factor to determine reliability. This could be small or wide. The average life time will be the same. So if only very few engines last significant longer than 20 hours, there will be very few engines which will last significant shorter. Thats a reliable engine. For an unreliable one its the other way around. But we dont know the variance and so we cant judge reliability. Engine life time alone is meaningless.

In fact, one of the problems which reduced the life time on the jumo 004 was the blade lengthening because of low heat resistant materials. But this lenghtening is a very steady process, which is controllable.
Of course this is not the only problem of the Jumo 004. And so its difficult to say it was reliable or not.

regards

thrawn

See your point and agree with you Thrawn. The distribution of the population is a crucial component on the effective life of an engine. And using a Gaussian (took me back to College on that one) would assume the engine life is not restrictive to the point of being a point of contention. Going on that perspective, my guess is the consideration of any engine under something like 15 hours (again, just pulling that one out of thin air as there is no data associated with it that we could, or I would, analyse) you would have a confidence interval in the high 90s that they would survive up to at least 15 hours.

But doesn't your arguement base itself on the condition that we know the standard deviations of the distribution. If we have a median of 20 hours without knowing the actual distribution (given this was a new technology in the situation it was being used), then there could be some engines that last 38 hours and there could be some that last 2. Given that the technology was not refined to the point it is now, with engine lifes in the thousands of hours, would it not be wise to consder the immaturity of the engines in the effectiveness of the aircraft?

I guess what I'm saying is, given how many unresolved (to the point of consistency that a jet engine ten years in the future would have) issues there were with the 004s, could the intervals of the population be so wide as to cover from the 0 time engine to the 40 hour engine?

 

[FLYBOYJ]

Some people are mixing expectet engine life time with reliability.
It is right that an unreliable engine has an shorter average lifetime than an reliable. But to assume a short life engine is unreliable is simply wrong.
If we assume a gaussian normal distribution with the peak at 20 hours engine life, the variance (width of the bell) is the factor to determine reliability. This could be small or wide. The average life time will be the same. So if only very few engines last significant longer than 20 hours, there will be very few engines which will last significant shorter. Thats a reliable engine. For an unreliable one its the other way around. But we dont know the variance and so we cant judge reliability. Engine life time alone is meaningless.

In fact, one of the problems which reduced the life time on the jumo 004 was the blade lengthening because of low heat resistant materials. But this lenghtening is a very steady process, which is controllable.
Of course this is not the only problem of the Jumo 004. And so its difficult to say it was reliable or not.

regards

thrawn

Thrawn - Your point is taken but during this period the statistical analysis of engine reliability couldn't really be determined because your Gaussian normal distribution (also known as a "baseline" in laymen's terms) was unattainable during that period for a number of reasons (tolerances, variances manufacturing process, still evolving workmanship standards, and mainly a still evolving technology). For example even by mid 1945 I-40s powering early P-80s that failed in service failed at varied times. Tony LeVier had a turbine blade come apart on a P-80 he was flying south of Edwards AFB in March 1945. I remember him telling me that engine had less than 10 hours on it. Even though these early manufacturers attempted to place a time life on these engines, it was still a crap shoot with failure imminent at any given time.

Bottom line whether we want to lump expectant time life into reliability, it was not comforting to those early pilots flying these crates and coming from a world where they could easily see 50 or 100 hours on a recip engine (and not normally fail during normal operation), these new turbines weren't reliable, regardless of any time life that might have been attempted to be attached to them.

 

[Cromwell]

Wrong.

And on what you wrote about jets. You see, by now everyone with decent interest in jet engines knows well enough about the relative advantages of centrifugal or axial compressors. And it is ****ing common knowledge that none is definetly superior to the other or else they were not both used until this day. But no, always someone has to make it look as if his country's engine concept choice was inherently superior.

1. Well before you start saying 'Wrong' perhaps you can tell me why I am wrong ? or perhaps you don't know.


2. Also, I think the issue was at that time which of the beligerants could field a reliable jet plane that would give them certain advantages in terms of time in the air, serviceability, safety and pilot confidence.

Based on the materials then commonly available the Centrifugal engine scored more highly in these areas - as well as in power-to-weight ratio. It so happened that this was on the Brit / US side of the equation.

So, it would seem that if the war had dragged on for a year or more, the allies might have been well placed to put up a credible jet force using technology that gave them certain advantages.

 

[Cromwell]

All true...

I live near the Mosquito museum here in the UK and they actually have some early Vamps Venoms. Its really strange to go up and touch the Plywood noses and the Fabric covered aerolons :-

Mosquito Aircraft Museum - de Havilland Aircraft Heritage Centre

Note. Pilots found the Vamp was a great plane to belly-land if needed - the shape and the elastic wooden structure used to just skid nicely long grass strips.

One other point :

I said earlier that the Me163 was a Rocket-plane. Someone else said 'Wrong' (bit rude really)

This is entirely true - it was driven by a reaction-rocket engine, running on mixed liquid fuels

Komet Me163 - Chief test pilot Rudy Opitz tells it like it was - Flight Journal.com Page 1

 

[Cromwell]

Great posts Cromwell, especially about the differences about the two engines. I was not aware of the differences in that light. Very interesting. As I am a relative novice on Jet Engines (I know how they work in principle but that doesn't mean squat in the real world), where do Turbofans fit in. Any link I can go to for a comparison to co-axle or are they the same?

On another note, somebody on the board used to use a Sterling and had a low opinion of it. Said something like it was useless for everything but opening beer bottles or some such. I can't remember. It might've been Airframes or one of those guys who were in the British Army in the 70s.

Well Wikipedia seems a good place to start - if a bit obvious !

Jet engine - Wikipedia, the free encyclopedia