Planes With the Best E Retention

[Widewing]

    if the above mentioned planes dive from 5k to 500ft and the dive angle is EXACT SAME
  all 4 will reach 500 ft at different speed,therefor even though you start timing at 400 mph the innital leval out speed is where the E retention comes into play
  if a plane levals out from a dive at 475 and another at 450 and you time both of them from when they reach 400 to 375 the plane that was going 475 will have more potential E stored.   

Huh?

We are talking about kinetic energy or KE = (1/2)mv^

Potential energy is related to altitude. Potential is that energy available should I dive to sea level from 500 feet. Potential energy has nothing to do with my test. PE = mgh, where h = height.

All of the aircraft exceeded 450 mph, but then decayed to 400 mph at a rate associated with total drag. For any given airframe, that rate of deceleration will be unchanged at 400 mph regardless of what level speed was attained prior. Regardless of what speed you begin measuring, the P-51 decelerates slower than the other fighters listed. Why? Lower drag.


My regards,

Widewing

[Masherbrum]

Before it became a "fad" like the Ta-152, the Ki-61 has very good E retention.   

[Saxman]

       ok it all looks cute~n~fuzzy
 first off, was all 4 planes at same speed at 500 feet when you leveled out ??
 if they wher then you have a ligit test. if not you wasted your time.
    if the above mentioned planes dive from 5k to 500ft and the dive angle is EXACT SAME
  all 4 will reach 500 ft at different speed,therefor even though you start timing at 400 mph the innital leval out speed is where the E retention comes into play
  if a plane levals out from a dive at 475 and another at 450 and you time both of them from when they reach 400 to 375 the plane that was going 475 will have more potential E stored.

.
   

I always think it's hilarious when people question WW's testing methods.

 

[Lye-El]

I always think it's hilarious when people question WW's testing methods.

 

Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. 

[Banshee7]

Before it became a "fad" like the Ta-152, the Ki-61 has very good E retention.   

Ki61 has become a fad?? 

[BnZs]

Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. 

Yet even WW himself is treated as know-nothing amateur when he questions why the P-51 in AHII doesn't handle more like people who actually tested the things and flew them in combat says it did. Along with everyone else who presumes to challenge the infallibility of AHII in regards to this or any other flight-modeling issues. Curious.

[Murdr]

Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. 

Yea, I think the engineer in this thread would know a bit about devising practical tests.

[Masherbrum]

Ki61 has become a fad?? 

Yep, a lot more in the air, same goes for the 152.   

[cobia38]

 i think we should call mythbusters...........they are after all the masters 

[Widewing]

I did some testing to measure deceleration with minimal propeller drag. I did this by taking off from a 10k field, accelerating to 300 mph, reducing rpm and then chopping power to idle. I then nosed over and dived to 3k, leveling off. I began recording the time of deceleration from 400 mph to 150 mph. All loaded with 25% fuel.

Results are interesting. More than interesting, they are very odd.

The Ta 152H required 101 seconds, while the 190D-9 required only 63 seconds.

The Spit16 required just 59 seconds, and the Tempest only 58 seconds. Yet, the FM-2 required 65 seconds.

P-51 came in at 94 seconds. F6F-5 at 86 seconds. P-39Q required 67 seconds. 190A-5 took 78 seconds. P-38L also took 78 seconds, and the Mossy needed 79 seconds. The P-47N used up 93 seconds, with the F4U-1A at 92 seconds. La-7 took 75 seconds, the Niki 58 seconds. The Ki-84 used up 75 seconds, and the Ki-61 74 seconds, with the Yak-9U at 73 seconds.

It seems that propeller drag, at either minimum or maximum pitch, is all over the place. How else can we account for the difference between the Ta 152H and Dora? Or, what can possibly account for the FM-2 decelerating slower than the Tempest?

<edit> P-38L requires 111 seconds if both props are feathered (use E key to auto-feather). Compare that to 78 seconds at minimum rpm.

My regards,

Widewing

[BnZs]

Do you have figures on drag area for these planes?

I did some testing to measure deceleration with minimal propeller drag. I did this by taking off from a 10k field, accelerating to 300 mph, reducing rpm and then chopping power to idle. I then nosed over and dived to 3k, leveling off. I began recording the time of deceleration from 400 mph to 150 mph. All loaded with 25% fuel.

Results are interesting. More than interesting, they are very odd.

The Ta 152H required 101 seconds, while the 190D-9 required only 63 seconds.

The Spit16 required just 59 seconds, and the Tempest only 58 seconds. Yet, the FM-2 required 65 seconds.

P-51 came in at 94 seconds. F6F-5 at 86 seconds. P-39Q required 67 seconds. 190A-5 took 78 seconds. P-38L also took 78 seconds, and the Mossy needed 79 seconds. The P-47N used up 93 seconds, with the F4U-1A at 92 seconds. La-7 took 75 seconds, the Niki 58 seconds. The Ki-84 used up 75 seconds, and the Ki-61 74 seconds, with the Yak-9U at 73 seconds.

It seems that propeller drag, at either minimum or maximum pitch, is all over the place. How else can we account for the difference between the Ta 152H and Dora? Or, what can possibly account for the FM-2 decelerating slower than the Tempest?


My regards,

Widewing

[Widewing]

Do you have figures on drag area for these planes?

Drag coefficients:

P-51D: .0175
P-39N: .0217
P-47D: .0243
FM-2/F4F: .0253
F4U-1D: .0267
P-38L: .0270
F6F-5: .0270


My regards,

Widewing

[bozon]

A few remarks:

I am not surprised by the results for the twin engines. The windmilling props create a huge amount of drag. The twins have two of them. On the other hand, the twins can feather the props and glide forever. Has anyone tried to land a mossie with both props feathered? Try it with no fuel and your rudder shot off a little like landing a helium balloon.

Deceleration depends on the Drag/Mass ratio, not just drag.

The drag created by the prop can have strange behavior at high speeds. Unlike real life, planes do not over-rev in AH and I don't know how the low-rev limit works for planes that cannot feather. I suppose the drag will depend on the individual prop and the high/low rev limits. I also suspect that this has an effect on the speed bleed of the light but high powered planes from high speeds and with full power on.

[Die Hard]

It seems that propeller drag, at either minimum or maximum pitch, is all over the place.

Of course it would be. Different sized propellers with different pitch limitations windmilling different sized engines at different rpms.

[Widewing]

Of course it would be. Different sized propellers with different pitch limitations windmilling different sized engines at different rpms.

I see, so that explains why there is a huge difference between the Ta 152H and Fw 190D-9 when they both have a Jumo 213 engine and the same propeller?

Guess not, huh?

Remember this equation: KE = (1/2)mv^   M=mass V=velocity. Velocity is the same. The difference in weight (mass) between the two is only about 400 lb, which should be offset for the most part by the Dora's much smaller wing (reduced flat plate area).


My regards,

Widewing