P-47M whine whine whine

[hitech]

Moot:

but where's the 47's exhaust thrust?

What force do you think drives the turbocharger?

HiTech

[moot]

I'm out of my depth. I didn't even know it had a turbocharger (I don't know jugs at all, so I went from memory of a jug fanatic mentionning a long time ago that jugs' exhaust thrust is a major factor).  So the N/M P-47s have no major exhaust thrust; or is it all P47 models?

I'm just curious how the 152 with so little power compared to the 47N/M can stay competitive. Is it mostly due to the 47's larger parasitic drag, then?  I won't try and speculate so much anymore.

[Die Hard]

Two aircraft of equal weight and thrust will have similar acceleration at low speed, but if one of them has much lower wing loading it will climb better. Acceleration also vary with speed if the two aircraft have different drag properties. Climb rate and acceleration are not always a linear equation, and never 100% so.

A good example is the Spitfire IIa with a constant-speed propeller and a 1,175 hp Merlin XII engine, and 109E-4 with a 1,175 hp Daimler Benz DB 601Aa engine. With equal engine power the Spitfire out climbs the 109, despite being heavier. However the 109 out accelerates the Spitfire in level flight at low to medium altitudes, but at high altitudes the Spitfire's wings again give it the edge also in acceleration.


So in a comparison between a lighter, less powerful plane with glider like wings (Ta 152) against a powerful, heavy, stubby-winged aircraft (P-47) there is no such thing as a linear equation of anything; there are too many variables.

[hitech]

Die Hard

Two aircraft of equal weight and thrust will have similar acceleration at low speed, but if one of them has much lower wing loading it will climb better. Acceleration also vary with speed if the two aircraft have different drag properties. Climb rate and acceleration are not always a linear equation, and never 100% so.

wing loading it will climb better.

It will also accelerate better.


By pure definition climb rate and Acceleration are the same thing. And of course we are not comparing Max climb rate with accelerations at different speeds. You must compare acceleration and climbs at the same speed. To put it very simply, climb rate is simply an acceleration against gravity.

If 2 planes have the same climb rate at any given speed, then their acceleration will also be exactly the same at that speed.

HiTech

[Die Hard]

That's correct hitech, but to simply say that the best climber is also the quickest in acceleration is inaccurate (you didn't say that, but it's easy to draw that conclusion from what you said).

[Stoney]

I'm out of my depth. I didn't even know it had a turbocharger (I don't know jugs at all, so I went from memory of a jug fanatic mentionning a long time ago that jugs' exhaust thrust is a major factor).  So the N/M P-47s have no major exhaust thrust; or is it all P47 models?

I'm just curious how the 152 with so little power compared to the 47N/M can stay competitive. Is it mostly due to the 47's larger parasitic drag, then?  I won't try and speculate so much anymore.

Well, there is a small amount of exhaust thrust, but as HTC alludes to, most of it turns the turbine that drives the turbocharger.  What isn't used for induction exits the aircraft at two points:  The waste-gate openings just behind and below the cowl flaps (look for the origination of the exhaust soot on the bottom of the aircraft) and the turbo exhaust just in front of the tailwheel.  I can't really see any benefit from the waste-gate exhaust as it exits the aircraft perpendicular to the direction of flight.  The turbo exhaust exiting the hood at the aft part of the fuselage would really be the only means for the Jug to gain exhaust thrust, and what comes out at that location is the spent exhaust coming off the turbine--not a lot compared to conventional exhaust systems on supercharged aircraft.  This system is consistent across all P-47 models.

http://rwebs.net/avhistory/history/supercha.htm

Do you have any information on the parasitic drag coefficient of the Ta-152?  We can compare it to the known values of the P-47s.  Ultimately, we'd need to create some power available tables and some other analysis to make a more accurate comparison.

[Karnak]

That's correct hitech, but to simply say that the best climber is also the quickest in acceleration is inaccurate (you didn't say that, but it's easy to draw that conclusion from what you said).

That isn't what he said though.

Take the P-51D and Spitfire Mk VIII at sea level.  At 200mph the Spitfire will have much more acceleration/higher climb than the P-51D but as we near the Spitfire's top deck speed that will change, at 325mph the P-51D will be able to both outclimb and out accelerate the Spitfire Mk VIII as almost all of the Spitfire's thrust is being used just to maintain that speed whereas the P-51D still has substantial thrust beyond what is needed to maintain level flight at 325mph.

[moot]

Thanks Stoney.  I don't remember if I have those specs, but I'll look. 

[bj229r]

This thread was really cool....now my head hurts

[eddiek]

I'm still trying to figure out why so many people say it would have to be perked.
190D-9, P-51D, Spit Mk XVI, 109K4 all have similiar performance #'s at typical MA fighting altitudes.  Like several people have said, it won't be a "dominant" ride til you are way up there in alt, much like the N model.  And unlike AH several years ago, it gets lonely and boring up that high, not many fights, so it won't see much action at those alts.
Oh well, I'll believe it when I see it.  After asking for it on this BBS and in person at the HTC offices for 8 years, I've all but given up.

[moot]

Stoney is this any help for the drag part of the equation?   

I'm still working on finding power vs alt figures.

I guess we're off topic now.  I'll start a new thread to keep this one clear.

[Stoney]

Stoney is this any help for the drag part of the equation?   

I'm still working on finding power vs alt figures.

I'm gonna need some help translating this stuff, but it appears to be an awesome collection of information.  Can you give me some pointers on where I might find some drag numbers?