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What if...General Motors was forced to fix the V-1710?


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#111 Flo

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Posted 09 May 2012 - 11:00 AM

You've rather made my point for me?

That's to say that the pilots used different throttle settings according to their tasking.

Your earlier posts about '65% this' or '75% that' are plucked from the air. They were nonsense numbers that make no sense.

As to what throttle setting a particular fighter pilot would use at a particular point in his sweep? Don't guesstimate it, 'ask' them. :D Many accounts given by the fighter pilots we're discussing, or their biographers, deal specifically with combat settings.

Edgar mentioned BoB RAF aircraft using maximum throttle throughout their sortie. Some Luftwaffe fighters did the same over Germany. Likewise, P-38s made long range sweeps over the vast distances of the Pacific at very small throttle settings. None of the three used an arbitrary 10% less when over enemy territory. Generally, when they approached the greatest threat- the Lightnings target, say- they advanced to full throttle.
The defending fighter- also at full throttle- wouldn't be able to take advantage of the part throttle approach of his foe, that part of the flight profile would be over before they met.

Your oft repeated assertion that "most pilots didn't see who shot them down" isn't quite the same as 'being unaware of the possibility of attack'.
Quite the reverse, most aircraft shot down in WW2 combat were lost in fully developed combat- dogfights.
Being shot down from ambush- 'bounced'- was rare enough to warrant specific comment in most wartime pilots autobiographies.

I appreciate your memory may not be what it once was, Stewart. That's fine, really. :) Just do a wee check that what you're about to post is correct.
You're in front of a computer. Just google the subject. Eg, Wikipedia isn't quite as knowledgeable as specialist reference books or expert opinion, but it's a great tool for checking that the broad thrust of your argument is correct.

:) I'm not trying to lecture you mate, just offer a wee bit of friendly advice? Sorry if it sounds a bit patronising.

Edited by Flo, 09 May 2012 - 11:03 AM.
pompous a*se disclaimer!


#112 Kutscha

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Posted 09 May 2012 - 02:11 PM

At 5000m at max continuous (2400rpm, 323mph) the Bf109E-3 had an endurance of 55min and a of range of 286mi.

At 5000m at max economy (1400rpm, 217mph) the Bf109E-3 had an endurance of 1.5hr and a of range of 413mi.

Almost all Lw s/e fighters were based in the Pas de Calais area.
Abbeville to London is 130mi.
Wissant to London is 90mi.
St Omer to London 115mi.

The DB601A had a time limit of 5 min at max power (1.3ata) except on take off when it was 1 min (1.4ata).

Sorry Flo but full throttle was not used unless to engage in combat. It was just too hard on the engines. Max continuous throttle would be the norm.

I agree this % throttle is nonsense. Using the DB601 for example:

30% of 2400 = 720rpm
30% 0f 1.4ata = 0.42ata

#113 Ricky

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Posted 09 May 2012 - 02:15 PM

Bottom line - Escorts cruise to their target while Interceptors race to theirs, but once battle is joined everybody goes as fast as possible.

#114 Flo

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Posted 09 May 2012 - 02:50 PM

Isn't that what I said? :D
Ricky put it better, but to clarify: one setting to get there, another for combat, neither arbitrarily chosen because the fighter was in any particular location. Especially no '-10%' rule for operating over enemy territory.

#115 GregP

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Posted 09 May 2012 - 03:28 PM

Neo,

We own Merlins and Allisons and I build Allisons for a living. At cruise a Merlin burns a US gallon a minute or 60 gallons per hour. You might get it down to 50if you push it, but most owners don't. You can get an Allison down to about 45 gallons per hour, but it is happier at 48 - 55.

At 25 gallons per hour, you will have burned up either engine or caused it to stop from being too lean unless you are at idle power on the ground without a propeller installed.

Where do you get your numbers? They are clearly not from the world of operating engines and aircraft.

#116 Kutscha

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Posted 09 May 2012 - 05:22 PM

Posted Image

Posted Image

Edited by Kutscha, 09 May 2012 - 05:26 PM.


#117 NeoConShooter

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Posted 10 May 2012 - 01:23 AM

[quote name='Edgar Brooks'][quote name='NeoConShooter']
My understanding (drop the "mis" please) is that the maximum setting was 3,000 rpm, which was only to be used at take-off, to 1000' (not 5 minutes,) then 2,850 rpm maximum climb (maximum 1 hour,) then continuous rich or lean, at 2,650 rpm, with a 5 minutes limit at 3000 rpm for combat, though 30 minutes, at that setting, was permitted above 20,000'.
I don't have a "problem," either, since the 5 minutes combat setting did not melt the pistons, but had to be noted down, so that, when a certain time (about 1/2 an hour) had been accumulated, the engine needed overhaul.[/QUOTE]
The RPM figures by them selves are absolutely meaningless. What was the throttle poss, manifold pressure, prop setting, mixture setting, altitude, speed, loaded condition of the plane, as in heavy or lite, etc. What other conditions?
The five minutes at combat power remark was made in response to the video someone posted of the game pilot who flew an intercept with the engine set at full throttle, MTO in modern parlance, with the mixture at the LEAN setting! I'll bet that if we ask the engine builder guy for his opinion, who's name I am so sorry because I can't at this moment remember it, whether or not that plane's engine would last that long or melt the pistons at LEAN mixture?

#118 Wuzak

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Posted 10 May 2012 - 01:44 AM

The RPM figures by them selves are absolutely meaningless. What was the throttle poss, manifold pressure, prop setting, mixture setting, altitude, speed, loaded condition of the plane, as in heavy or lite, etc. What other conditions?
The five minutes at combat power remark was made in response to the video someone posted of the game pilot who flew an intercept with the engine set at full throttle, MTO in modern parlance, with the mixture at the LEAN setting! I'll bet that if we ask the engine builder guy for his opinion, who's name I am so sorry because I can't at this moment remember it, whether or not that plane's engine would last that long or melt the pistons at LEAN mixture?


The throttle position is meaningless. The RPM and boost settings are more important. The throttle position will change with altitude to maintain boost pressure settings.

Can't have METO with lean mixture. There will be a maximm boost the engine can run in lean, which won't be nearly as much as for METO.

#119 GregP

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Posted 10 May 2012 - 01:47 AM

Hi Kutscha,

Thanks for the posted tables. Nobody today cruises above 12,000 feet or so ... maybe as high as 15,000 feet. If you have a fighter, who wants to waste the engine life in straight and level IFR flight?

We have more than 100 Allisons out in the flying world and know more than 80 Merlin users, and NOBODY gets 25 gallons per hour at 10,000 feet and below. If you do that (might be possible to sustain operation), you'll wind up paying Mike Nixon or somebody else to overhaul the Merlin and Joe Yancey or somebody else to overhaul the Allison WAY TOO SOON.

But, by all means, go ahead if you want to prove it is possible. You coudl be right ... and doing that is very good for Joe's business.

The tables you posted are for Merlins owned by a government, with government-paid mechanics and massive spare parts inventories. There aren't any government-owned Merlins flying in the world except maybe the British BOB Memorial Flight, and they don't want to overhaul their Merlins anymore than any other owner does these days, and they don't have more parts than anyone else does.

If you don't run the V-12's at a decent power level, you'll PAY in the end, and much sooner than you expect to.

Allisons aren't happy producing less than 550 - 600 HP in flight. Idling on the ground is OK until you heat up, but they are made to fly with airflow though the radiator and with the oil in the green temperature range. Most people cruise them at 2,000 rpm and 30 inches of MP, and 3,000 rpm and 50 to 70 inches at airshows ... and they get GREAT engine life.

We have one customer who runs his Allisons at 4,000+ rpm and 160 inches of MP, and he has been doing that for more than 10 years in a tractor with no failures. Of course, a tractor pull is a short engine run! He runs three Allisons putting out over 3,000 HP each!

Edited by GregP, 10 May 2012 - 01:54 AM.


#120 Kutscha

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Posted 10 May 2012 - 02:10 AM

Greg, you are starting to sound like Crumpp. He confuses today with yesterday all the time.

The thread is not about today but yesterday. What is relevant is how they were operated yesterday, not how they are operated today.




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