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But understand that when these early engines "broke down" they usually "blew up." Compressor or turbine bearing failure, blade failure or burnt burner cans meant a complete engine teardown.But we are talking aboutt the 'life' of the engine rather than simply 'going wrong' aren't we? If a Welland broke down after 20 or so hours running it may be fixed, but after that time the Jumo was only fit for scrap, if I have understood the various histories correctly.
Flight tests and flying the aircraft operationally are a bit different. many of the early engines (I-40, W2B did well in a test enviornment. It's when you started producing the engine and start gathering engine life trend data in operational aircraft is when you start seeing pre mature failure.No luck so far on specifics but there are some interesting quotes in D N James 'Gloster Aircraft since 1915;
Regar.ding the E.28/39's early testing in 1941, it states following the successful first flight "during the next 13 days a further 10 hours flying were accumulated in 15 test flights without the need to remove the engine cover".
This was following the FIRST flight of the first allied jet. That at least strongly suggests a life of more than 20 hours overall.
As does the line, in relation to an uprated Derwent engine in 1945 "this engine successfully passed its 100 hr test before being flown in Meteor III EE260 by Eric Greenwood on 17th May".
I think the real proof would have to come from service records. But I am quietly confident, If I can find them
I never said "all" in terms of TBO. The factory gave them a TBO of 160 hours, my point is they rarely made that time in operational service (or at least a good portion of them). I think 160 Wellands were built before production was stopped. Most of the on line literature mentiones the Derwent being a better and mre reliable engine.Can you provide anything to support your statement that all early engines had a 20-25 hour service life? You see everything I've seen points to the early British service service engines having lives of between 100-160 hours at least. The only references to much shorter lives always refers to German engines and always refers to it being due to their lack of specialist alloys that allowed British engines to last much longer, I find it odd that no references to Meteors, Vampires or the XP-59A/XP-80 see fit to mention short engine lives it it was the case?
First off FBJ I 'd like to apologise for the almost confrontational tone of my question (that you quoted). It was just a question but my wording could have been better. I blame the fact that my wife was stood with her coat on demanding a lift to work, so I was rushing it. whats wrong with the bloody bus, lazy sod?
Yes - in the test cell things are very controlled and uniformed. No changes in air temp, no g loads on the structure, gravity not working aganist the flow of fluids, etc.I think I have your point now, and I was also thinking of the Derwent among the 'early jet engines'. Yes, the first few would have had short operational lives, though I still think from the general sources available that they last far longer than the German engines of the same time, otherwise they would not have been accepted for service. Look at the quote where a Derwent completed a 100 hr test before it was flown. However I take your point on there being a difference between this and operational use, but I find it hard to believe the difference would be that great.
I think in the early development days premature failure was just considered norm. My guess is when the money train stopped, people responsible for fielding these things started tracking specifics on when and why failures occured.I wonder why specific figures seem to be so hard to come by though? Maybe a 'reliability myth' has grown around the early RR and DH engines but I would have to see something solid to accept that as fact.
You're 100% wrong. As early as WW2 the military (at least the US and Germany, some in the UK)kept pretty accurate records with regards to failure analysis in many of the weapons systems deployed. Eventually some of the methodologies used evolved into things like trend monitoring and risk mitigation and is a norm in today military.any and all engineering is a compromise. what is an acceptable failure rate? if it's my engine make that zero. the military has always had a somewhat caviler attitude about lives. i guess its because men get killed no matter what you do.
Apples and oranges. The examples you bring were all ready developed items that suffered because of quality related to cost and profits. As far as the M-16, that was the result of not enough foresight into what type of environment the weapon would be subjected to and it also stems for a 1950s/60s mindset that the best weapon was the most technically advanced and it could do all. "MacNamara Thinking."as to the test-bed times and real world times that really has not changed. look at the recent toyota fiasco or the famous pinto exploding gas tank. look at the "swiss-watch" zero clearance m-16. built for combat in the jungle. anybody at colt care when it goes click?
As far as the M-16, that was the result of not enough foresight into what type of environment the weapon would be subjected to and it also stems for a 1950s/60s mindset that the best weapon was the most technically advanced and it could do all. "MacNamara Thinking."
It was also the result the of changing the propellant type from a stick powder to which th eweapon was developed with to a ball powder with a heavier deterrent coating which had a much higher "soot" factor.
Colt had little or no control over ammo production.
The fact that a F-104 never shot down a single Mig wasn't the fault of the airplane, but a matter or where and when it was operated. it served for almost 25 years through out NATO and did everything from interceptor to mini nuke bomber.Guys, exactly my point. since nothing is or will ever be perfect development has to stop at some point and there are factors which cannot be controlled or even foreseen. the consumer (civilian/military) are always the ultimate beta testers. military contractors are out for the same profit as any other company. failure records are great but they are still failures and someone pays. we used to say: "remember, your weapon was made by the lowest bidder". I was a "ground pounder" so i'm more familiar with ground weapons but i do recall the F-104 which never shot down a single mig and had no way to carry ordinance on their wings, unarmed HUEYs that we had to hang machinegun by bungee cords, F4 phantoms that no one had thought to equip with cannon or machine guns, and when they were jury-rigged no gunsight, the good old M-113 with a 50cal mounted high on top with no protection or gun ports.
FBJ, i guessed that you were a pilot and you have my utmost respect. one of my main missions was to rescue downed pilots after SAR had failed.
All true - the F-4 did do well without the gun, the Sparrow missiles were horrible and many MiGs "got away" because of a lack of a gun.as i said not all failures can be foreseen or controlled espec in a combat situation. i was not blaming the planes or pilots, rather the military genius who decided that the f4 would only need to shoot down russian jets and therefore equipped it only with missile then decides to send it into a combat situation outside its design parameters. after the f4 was redesigned it became the deadliest fighter out there. the pilots used to claim that they were the world's largest supplier of used mig parts.
When were you in Nam - my brother was there in 68, Ashore Valley. He's called in airstrikes to have skyraiders show up.when we asked for close ground support the 7thAF sent high speed jets instead of the skyraiders we asked for, after all jets are so much cooler than cluncky old prop jobs. just like AH deciding that the 262 should be a bomber (though willy should bear the brunt of that since he lied) stopping production and recalling built planes to redesign them.
to me failure is failure to perform mission for whatever reason, machine or human
I wonder why specific figures seem to be so hard to come by though? Maybe a 'reliability myth' has grown around the early RR and DH engines but I would have to see something solid to accept that as fact.
I can't remember reading anything in particular about Meteors and engine failures. There were other issues with the engines, but not reliability. The only real problem I can remember was blanking of the engines during sharp manoeuvres at low speeds which would cause them to flameout. This wasn't a particular problem from the engines but rather from the Meteor's long nose disrupting the airflow over the nacelles when yawed.
I can remember reading of failures with Whittle's early engines, sometimes turbine related (still with stainless steel blades) and sometimes compressor related but have never seen mention of problems with the production engines.
Welland was discontinued in favour of the higher powered Derwent rather than anything else. Power Jets basically designed the Welland whilst the Derwent was RR's first engine. Power Jets improved the Welland design to the W2/700 which gave 2500lb+ but RR continued with the Derwent line.
From the lack of evidence its really quite difficult to conclude that the Welland or Derwent was unreliable.