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Well, your conclusions do come across as being very definite, with little room for doubt; though it may just be your style that gives that impression, I suppose. As for the Statistical Digest, I have tried to find more data, but I haven't found anything that can explain why there are differences between it and MAW IV or unit records; but it does underline how uncertain and confusing WWII data can be.
I knew 80% efficiency was a figure at certain speeds, and never connected that data with the constant-speed propeller. I figured the constant-speed propeller did allow the efficiency of the propeller to be varied for speed.You are over complicating things. especially #3
Most props (once you get rid of the fixed pitch and two pitch things) are just about 80% efficient give or take (mostly take) a couple of points. That was the whole idea of the constant speed propeller.
Of course -- that variation is proportional to speed?Since the conversion of engine thrust to power varies with the speed of the aircraft there is a considerable reduction in "power" at climb speeds compared to max level speeds.
This might sound silly but why does drag go up with the square of speed and power needed go up with the cube?We don't need to know cooling drag, that goes right in with over all drag. yes a plane in climb mode (cooling flaps and doors open and hanging in the breeze) is very dirty compared to one closed up for high speed but then instantaneous drag goes up with the square of the speed. Power needed goes up with cube of the speed.
That was kind of what I was going for. While this might sound silly could I simply use the TAS of the airplane to do a rise over run sort of thing where I factor the speed in fps; then compute climb-rate in fps at that speed and use the slope equation to just figure out how high-up the nose is pointed and then use that to establish a power-to-weight ratio (T/W of 0.5 = 45-degree maximum climb which is 1/1).Want to check your "thrust" calculations at 140-160mph climbing speed?
I didn't even think of that variable. That said, what was the roll-rate of the Spitfire using fabric covered ailerons?As I posted earlier, I think the RAE and NACA graph we all use as gospel may not be giving the full picture for one reason or another re: the Typhoon roll.
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In service, if the Typhoon's roll rate over 250 IAS compared best with a Spitfire with fabric ailerons (and a lot worse under that) than any other fighter -- you'd think this wouldn't escape constant mention.
I didn't even think of that variable. That said, what was the roll-rate of the Spitfire using fabric covered ailerons?
I knew 80% efficiency was a figure at certain speeds, and never connected that data with the constant-speed propeller. I figured the constant-speed propeller did allow the efficiency of the propeller to be varied for speed.
Drag is the force acting at one one moment. Or perhaps the resistance to force at any one moment?This might sound silly but why does drag go up with the square of speed and power needed go up with the cube?
I know J is advance-ratio, what's 0.75R, and that funny looking N sub pe on the y-axis?View attachment 525845
That is one chart, others may differ a bit (not go over 80%?) but basically the constant speed propeller will have a good efficiency over quite a speed range.
I followDrag is the force acting at one one moment. Or perhaps the resistance to force at any one moment?
I figured force would be based on surface area, (L x W), but we live in a 3D world so you have L*W*H. I figured it'd have all cubed up.Power introduces a time element. Plane A for instance is going 20 % faster than Plane B. It needs 44% more force at any one moment in time.
This stuff about 'tuning the engines" is a pet peeve of mine.
Just what the heck did they do to "tune' the engines?
The ignition timing is fixed. The valve timing is fixed. the intake track is fixed, you have very very limited options on the exhaust stacks.
You can change the jet size in the carburetor/injector but most aviation fuel (at least from the same country) had pretty much the same BTUs per gallon/pound so screwing around with the mixture isn't going to get you much.
That leaves messing around with the boost control, which really isn't "tuning" an engine in the conventional sense.
US 100 octane used 2% or less aromatic compounds and the rich response of the fuel didn't change much from the lean response. It was sort of 100/98-102 fuel.
British BoB fuel was 100/115-20 and had no less than 20% aromatic compounds.
The high aromatic compound fuel would dissolve certain rubber parts in the fuel system and degrade early self sealing tank liners so the number of early US fighters that used the two different fuels is limited. US agreed to go to the high aromatic fuel even before Pearl Harbor so fuel incompatibility wasn't really a problem. Neither was "tuning" the engines once they left the United States,
Drag is the force acting at one one moment. Or perhaps the resistance to force at any one moment?
Power introduces a time element. Plane A for instance is going 20 % faster than Plane B. It needs 44% more force at any one moment in time. However if you change the speed of plane A by 20 % it is trying to cover more ground (move aside ) 20% more air in the same amount of TIME as the slower plane, in addition to moving the air aside faster and the higher friction impact. Stick arm out of car window at 40mph and 50mph. more force acts on the arm in any one moment and keeping the arm out there is going to require a lot more work (muscles get more tired) in the same amount of time
I know J is advance-ratio, what's 0.75R, and that funny looking N sub pe on the y-axis?
I follow
I figured force would be based on surface area, (L x W), but we live in a 3D world so you have L*W*H. I figured it'd have all cubed up.
Disclaimer: I was born in the early 1980's and as a result went to school during the late 1980's to early 2000's. Our education and curriculum suck.
That is important...because the mechanics adjusted maximum boost for more power.I believe the Desert Air Force did use 100/130 fuel in the Med but I'm not sure precisely when that started.
For the CBI I am not sure but most of the supplies came via India which at the time was part of the British Commonwealth.
Thank you.
I believe the Desert Air Force did use 100/130 fuel in the Med but I'm not sure precisely when that started.
For the CBI I am not sure but most of the supplies came via India which at the time was part of the British Commonwealth.
As I posted earlier, I think the RAE and NACA graph we all use as gospel may not be giving the full picture for one reason or another re: the Typhoon roll.
(re: my earlier posts here)
Which is the better fighter, P-40F or Typhoon?
Which is the better fighter, P-40F or Typhoon?
In service, if the Typhoon's roll rate over 250 IAS compared best with a Spitfire with fabric ailerons (and a lot worse under that) than any other fighter -- you'd think this wouldn't escape constant mention.
Not fantastic but much better than the Typhoon according to this which Ivan already posted upthread.
I'm basically on the same page, I think. As I said earlier, a simple, steady rate with 50 lb force 'may not be giving the full picture'. When you read all the opinions from the A&AEE, USAAF, and AFDU what you don't see is "this is the worst rolling aircraft at any speed this establishment has ever seen". So I'm fully prepared to believe there's more nuance to roll performance than steady rate at 50 lb force.
Re: the Zero, that can easily be explained by speed. Under 250 IAS (according to Allied tests) the Japanese fighter handily out-rolled the Wildcat/Hellcat - above that speed the US fighters held the advantage.
I'm fairly certain the Typhoon was used for ground attack over the Spitfire more due to superior lifting capacity and inferior high-level performance (vs. the Spit IX). Though I'm sure the Spitfire's superior climb and manoeuvrability played a part.
I would probably disagree about the compressibility issues - if we're talking about the same thing. Typhoons were routinely dived at high speed while bombing.
Why not use the Typhoon as a long range fighter carrying a couple large drop tanks instead of committing them all to the ground attack role?