Early Jet Engines Spool-up Rate

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KJ_Lesnick

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Okay...

How long did it take for some of the early jet-engines such as

- HeS 3 (Heinkel He-178 powerplant)
- Power Jets W.1 (Gloster E.28/39's powerplant)
- Rolls-Royce Welland (Gloster Meteor Powerplant)
- BMW-003A
- Jumo 004
- Rolls-Royce Nene
- Westinghouse J-30
- General Electric J-31
- Westinghouse J-32
- Rolls Royce Derwent / Allison J-33
- Westinghouse J-34
- General-Electric/Allison J-35
- Allison J-71
- General-Electric J-47
- Armstrong Siddely Saphire / J-65
- Rolls Royce Avon

From what I remember the J-35 and J-47 took something like 20 seconds... but the others I have no clue...


KJ Lesnick
 
ı believe Jumo engines on the Me 262 needed about 45 seconds in flight , so you had to land once you committed , it was practically impossible to reposition for a second try .
 
R-16,

Forty-Five seconds? How the hell did they manage to dogfight at all with such an awful slow spool up rate?
 
I flew a couple late versions of the J-34 in the late fifties early sixties as well as J-33 and one or two others. Perhaps the manuals have something in them. I do remember flying one aircraft that required a go-around decision as soon as the wings were level on final. One might make it with into a touch and go, but you would almost certainly touch down. That was including retracting speed brakes, which I do not believe the 8-262 had. However, remember that thrust vs rpm is not linear, If you can carry 50 0r 60% rpm with the speed brakes out, between retracting the speed brakes and full throttle the effective spool up time is reduced.

Best Regards,

Artie Bob
 
Civilian high bypass engines, with their large diametre fans and generally heavier rotating parts, are still pretty slow. Smaller military engines are quite fast nowadays, the F404 takes about four seconds from idle to full afterburner and the M88 is even claimed to be slightly faster.
 
in comparision ...

how long does a classic recip engine take from idle to full power ... something like a RR merlin or a P&W R4360?
 
I got some information back from a friend who is a United Airlines A320 captain and he told me that their IAE V2500 engines have a spool up time of around five seconds.
 
agricola64,

I'd assume they'd be very fast. I mean my car and motorcycle both use reciprocating engines and they rev up right away
 
KJ_Lesnick said:
agricola64,

I'd assume they'd be very fast. I mean my car and motorcycle both use reciprocating engines and they rev up right away
Click to expand...

i agree that recips "spool up" very quickly ..

but if you need to accelerate a large anount of ironmongery it is going to take a little while -- it is also taking a little time for the exhaust gasses to reach the turbo-charger, for the turbo-charger to spool up and for the air to go through the intercooler and reach combustion

so i wuld not expect it to be instanteous
 
while the topic is about engine performance , ı think ı might say that Me 262 wasn't meant to dogfight .Although its pilots speak well of it as a flying machine , it had only the speed advantage , the German pilot could look for an unattentive enemy pilot and shoot him down in straight gunnery pass .The statistics suggest about 80 % of air combat kills are from surprises when the targeted aircraft didn't see the attacker or it was too late to do something effective . If the Germans had enough air superiority over their airfields and enough '190s to shoot down the endless streams of bombers the Me 262 would have won the war for them .In 1945 , it was hard to surprise the Allies , or running from them . ı remember reading Tempests following a jet for an half hour . They wouldn't catch him in the air , but he would have to land and options were limited . Not even the Mig-15 would have won the war in 1945 for Germany .
 
Sentinel Chicken said:
I got some information back from a friend who is a United Airlines A320 captain and he told me that their IAE V2500 engines have a spool up time of around five seconds.
Click to expand...

Interesting, that's pretty fast!
 
R-16,

ı think ı might say that Me 262 wasn't meant to dogfight .
Click to expand...

You sure about that? Back then I was under the impressions that all fighter planes were designed to dogfight as simply put all air to air combat was up close and personal until missiles came around. While Hitler wanted the Me-262 re-designed as a bomber, it was originally a fighter, and from what I read about it, it had excellent handling.

From what it would seem the trick was to use the speed advantage to provide a good rate of turn (in terms of degrees per second -- turning arcs were wider) and to avoid trying to actually turn as tight as propeller driven planes (in terms of turning arc).


KJ Lesnick
 
If you moved the throttle too quickly on the Jumo 004 you could get a flameout anyway. So, the throttle would have been good for adjusting cruise speed and controlling energy during landing approach, but not in combat. It was an interceptor with reasonably good handling, a devastating armament and the ability to pull away from any opponent using a shallow dive (providing the 262 pilot spotted the attacker soon enough). Its edge was in speed and armament. It could destroy a plane in one pass, but it couldn't dogfight its target (or even get a second pass without breaking off from the engagement first). Like most early jets it couldn't handle tricks, rapid throttle adjustments and close manoeuvring the way most biplanes and early war fighters could.
 
I remember hearing something about military jet-engines particularly those used on fighters at some point adopted a fuel control system that produced a tighter surge margin to allow faster spool-ups, and more bleed-valves to compensate for this and allow the pilot to slam the throttles around more liberally without worry.

From what I infer, this sounds like certain turbojets used on jet fighters would spool up a bit quicker. Of course I'm not sure how much faster. With that said how quickly did the J-57's and J-75's used in fighter designs take to spool up from idle to full military power?


KJ Lesnick
 
"it is also taking a little time for the exhaust gasses to reach the turbo-charger, for the turbo-charger to spool up and for the air to go through the intercooler and reach combustion". During WWII most fighters did not have turbo-chargers, the main exceptions being the P-38 and P-47. So turbo spool-up was not a factor except in some USAAF fighters. I am pretty certain no Merlins saw combat with turbos.

Best Regards,

Artie Bob
 
returning to Me 262 , Germans were quite the innovators of the method described ever since they had Albatross fighters against the Allies and the distinction ı am using has been present since 1917 as far as ı can see it . Dogfighters like Camels and performance fighters like the SE-5 . Zero handled the Allies roughly as it was a very good dogfighter with at least equal performance to anything that opposed it in the beginning and it ruled supreme . Then Americans took the performance advantage . It is all relative to the context the fighting is in . Corsair will be defined as a performance fighter since it did so much against the Japanese - dive, shoot and reposition for further attacks - yet New Zealanders in occupation duty in Japan actually caused a few Spitfires in mock combat to lose their wings as tried to match F4-U's tight turning at high speed . And ı don't think 262 suffered in any way by getting bomb racks . Even Spits had them . It is an excuse by German industry to cover the fact that they produced 1400 plus and only 100 or so made it to the frontlines . The guys had to get all those Starfighter contracts you know and they had to prove it wasn't them that failed .
 
I was at RR Bristol before Christmas watching an EJ200 on test. Time from idling to max reheat is only seconds though I can't remember an exact figure. The testing was surprisingly violent with very rapid thrust changes to check that there were no problems. It's also awesome to watch.
 

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