Author Topic: 262 durability ? (Read 2367 times)

SageFIN · « **Reply #75 on:** July 19, 2002, 12:40:23 PM »

Roscoroo, one of the points Ho Hun is trying to get across is that reliability and combat survivability of an engine are two separate things and not necessarily connected.

Karnak · « **Reply #76 on:** July 19, 2002, 01:46:33 PM »

SageFIN,

He's right in that they are not necessarily connected, but in the case of the 262 they are. He has yet to show one iota of data that the 262's engines were durable. He insists on ignoring the only data, admittedly of the personal account type, that we have and insists that his opinion, unsupported by data, is correct.

Frankly, he's coming off as a demagogue.

AKSWulfe · « **Reply #77 on:** July 19, 2002, 01:59:55 PM »

Hell- I gave a freaking diagram of the engine.

It's obviously a very easy target to hit being underneath the wings, it has no armor around the engines, and a barrage of .50s cals ain't gonna be shrugged off lightly by an engine that DID have problems falling apart. Hint: the rotor blades were known to rip off.

So you get some foreign material in there (.50 cal), it pierces the engine, flies through the compression chamber forward of the compressor blades and you are gonna have a helluva lotta material getting sucked into those compressor blades.

It ain't no A-10 engine, which was designed to take crap like that, it's a first generation jet engine that's highly vulnerable to enemy gun fire.
-SW

Roscoroo · « **Reply #78 on:** July 19, 2002, 05:42:02 PM »

Quote

Frankly, he's coming off as a demagogue.

who is ????

I'll I have done is given all of you places to look, read,and experiment for yourselves . You can come to your own conclusions.

In my opinion based on the Facts I have read,and been taught. the Jumo engine in the ME262 is great piece of engineering that issued us into the jet age. But it is a substandard pile of junk with no reliability.

If the Germans would of kept using top grade metals and had more time for testing and quality control for the engines . these planes could of put a big dent in the Allied bombing raids, as they are, they were lucky to get off the ground make one straffing pass and land safely .

We must also look at the fact that these are turbo jet engines not turbo fans (like in the A-10 ) a turbo fan has a seperate turbine and the front fan section , and the big fan out front is used for thrust not for compressing air into the engine . in this configuration the fan can ingest foriegn objects and spit them out without near the damage that a turbo jet will go thru if even a single rock goes thru it.

I believe if there would of been more ME262s harrasing the Allied Buffs that we would have came out with a Shaff or shrapnel launching device (kinda like a defensive flak thing) that would of really put a stop to the ME262's abilitys. (why shoot bullits when all you have to do is toss used tin beer cans at it to ruin it ? )

HoHun is just trying to have a good Discussion going on here .

~~Oops getting carried away again~~

Innominate · « **Reply #79 on:** July 19, 2002, 06:01:54 PM »

Does anyone have any credible evidence of jet engines being better at taking damage than piston engines? There have been of engines exploding because of a single compressor blade cracking off, on modern jet engines. I seriously doubt that a jet engine will survive more than a radial piston engine.

HoHun · « **Reply #80 on:** July 19, 2002, 07:10:37 PM »

Hi Karnak,

>He's right in that they are not necessarily connected, but in the case of the 262 they are. He has yet to show one iota of data that the 262's engines were durable.

As I've already pointed out, the Jumo 004B was designed to deliver the same power as the Jumo 004A that used high-quality alloys. This means that the turbine blades from substitute alloys were able to take the same mechanical stresses as the high-quality blades. They did not have the same longevity, though, but damage resistance is mainly determined by the ability to take mechanical stress.

You can find an explanation of the cause of the Jumo 004B's short engine life at the site pointed out by Roscoroo:

http://www.stormbirds.com/project/technical/technical.htm

>He insists on ignoring the only data, admittedly of the personal account type, that we have and insists that his opinion, unsupported by data, is correct.

Battle survivability is a statistical process. Personal accounts of Me 262 kills aren't random samples that would enable us to determine Me 262 durability, not even for a rough estimate. To arrive at such an estimate, you'd have to include the unsuccessful attacks on jets for the same set of pilots and missions. That's a mathematical requirement I'm not responsible for :-)

>Frankly, he's coming off as a demagogue.

Which is a good example for a demagogical statement itself :-) This is a pretty ordinary forum discussion, no need to get overwhelmed by bad vibrations!

Regards,

Henning (HoHun)

HoHun · « **Reply #81 on:** July 19, 2002, 07:24:20 PM »

Hi Rocoroo,

>http://www.stormbirds.com/project/technical/technical.htm

Good link, thanks!

>So if we compare todays jet engine to piston engines we find that yes it is way more reliable . But back in the 40's and early 50's the piston engine was way more reliable .

As I pointed out repeatedly, reliability and survivability aren't necessarily connected. The answer for the reliability question is probably much easier to find, and we could open another thread for that if you like :-)

(You might have heard of the Lockheed Constellations being referred to as "the world's most beatiful trimotor" since it was quite common for the airliner to arrive at its destionation with one of the big radials off and its propeller feathered :-)

>Well I had a great post here until my 1 1/2 year old copilot came by and hit the reset button on my PC and I lost my chain of thought , but I find this discussion alot better them most of the garbage on these boards

Too bad about the reset! I think the standard mod consists of adding a master arm switch in the front seat to prevent accidental operation of the reset button by unqualified crewmembers ;-)

Regards,

Henning (HoHun)

BUG_EAF322 · « **Reply #82 on:** July 20, 2002, 12:39:06 AM »

HOW RELIABLE IS AN ENGINE THAT HAD TO BE REPLACED AFTER 24 HRS FLIGHT TIME ????

Roscoroo · « **Reply #83 on:** July 20, 2002, 05:40:43 AM »

If were gonna discuss the reliability of jets vs prop planes then perhaps we need a time frame here such as 1940-52 /57

by 1958 is when most of the bugs of engineering were worked out of the jet engine.

we can do a 1958-70 comparison to ... just to have fun with it .

I 'd gladly drag up some more objective web sites . for im not biased either way when talking about this stuff .

And its a great way for everyone to learn . Go ahead start another thread if you want

flaps737 · « **Reply #84 on:** July 21, 2002, 12:23:06 PM »

Embry-Riddle in daytona beach florida purchased 3 Jumo 004's (D or E model i think) many years ago. I talked with a professor that runs the turbine engines lab and teaches engine courses for pilots there. The first engine wouldnt run at all even though it appeared to be in good order. The second engine ran and was played with in one of the test cells for a while, until a carpenter walked a little too close in front of it while it was in operation. It sucked the roofing nails out of his tool pouch, damaging the compressor blades enough to render it inoperable. This engine is now on static display at the school, and is cutaway so that you can see the internals, and also the little dings on the compressor blades made by the nails. The 3rd engine was never run and donated to a museum some years later. I will try to supply pictures of the Jumo on display at the school. The little dings in the compressor blades were enough to stall the blades and cause catastrophic failure in a matter of seconds.

HoHun · « **Reply #85 on:** July 21, 2002, 04:19:33 PM »

Hi Flaps,

>Jumo 004 (fairly) recent experience story

Try that with any jet engine, and the results will be similar.

Ingestion of foreign objects is not the same as getting shot at.

It could be a concern in combat, and Me 262 tactics included passing over the top of bomber formations instead of diving below it to avoid ingestion of debris from damaged bombers. However, I don't think this is a reason to doubt the survivablity of the Jumo 004B engines.

Regards,

Henning (HoHun)

Roscoroo · « **Reply #86 on:** July 21, 2002, 08:11:41 PM »

Well I think survivability and combat reliability kind of go hand in hand here . say you have a engine (it doesnt matter what type) that will break easy under sudden high boost pressure ,prop overspeed,unable to withstand a spike in temperatures,in case of a jet engine a compressor shift when decreasing or increasing rotation speed. This all adds into how capable a aircraft can dogfight.

I would like to know how anyone could get that close to a running engine in a test cell to have nails endup ingested into it .
I could see it happening but it sounds more like a flight line- prop wash story to me. (its probly fod ingestion from the flightline or rubbing of the compressor blades)

I was stationed at a Depot level base and spent many hours (on boring Grave shift nights) hanging out with all the civilians (the evil "hearts" player types) that worked in the engine shop and over in the test cells during many run ins and tests. along with being engine run/trim qualified on WC-135B's w/ TF-33 's , I have also been within 2 - 3 feet of a Running prop on C-130's

whgates3 · « **Reply #87 on:** July 22, 2002, 02:52:04 AM »

if anyone is interested there is an article titled 'flying the me262' (or something like that)written by a guy who did so in the sept 2002 Aviation History magaizine. the only unusual things mentioned about the engines, with regards to their performance, was the lack of fuel injection and the good possibility of an engine catching fire during the starting procedure. whenever the 262 was started a team of firefighters was close at hand

HoHun · « **Reply #88 on:** July 22, 2002, 03:38:32 AM »

Hi Roscoroo,

>This all adds into how capable a aircraft can dogfight.

In the case of the Me 262, the main limitation of the engine was that it would not take any quick throttle changes. However, jet tactics didn't call for quick throttle changes (or dogfighting), so this wasn't much of a tactical problem.

The cause of the limitation was the the engine control system, so it was not a question of mechanical reliability. Junkers had a better system eliminating the problem ready at the end of the war, but it didn't get into production.

In short, there's no connection to the engine's battle survivability.

Regards,

Henning (HoHun)

HoHun · « **Reply #89 on:** July 22, 2002, 03:40:56 AM »

Hi Whgates,

>whenever the 262 was started a team of firefighters was close at hand

This was standard operating procedure for piston engines as well. Nothing special about the Jumo ...

Regards,

Henning (HoHun)