Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: fscott on October 21, 2000, 06:04:00 PM
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I tested the F4U1D and F4U1C and the P51D in E-retention. What I did was loaded all planes up with 100% fuel, emptied the ammo loads, and climbed to 1000 feet. I maintained a speed of 200mph for 30 seconds then cut the engine while maintaning level flight. I timed how long it took each plane to reach speeds of 100mph. In this case the F4's would just start to stall out but not losing much if any altitude, the same applied to the P51.
F4UD 27 sec
F4UC 28 sec
P51D 24 sec
There are just rough numbers, but my question is should a huge plane like the F4U, with that big open radial frontend glide longer than an inline engined plane like the P51D?
This is what makes me suspiscious. Since they are all flying a level plane, shouldn't the F4U's create more drag and thus reach 100mph sooner than a P51?
Now the N1K1, I didn't have time to do this one but I will. here is a plane that is much lighter than an F4U yet also has a big radial engine on the front. If the arguement is that a massive plane like the F4U will have more E, then I would assume a smaller and lighter plane like the N1K2 would bleed speed quicker. As we all know, it seems to hold E better than any plane level with engine cut. I am assuming the N1K2 will come in well over 30 seconds.
I dunno maybe this type of testing is flawed. I am ASKING, not debating. Please respond if you have a clue.
fscott
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N1K2-J just registered 48 sec from 200mph to 100mph! It reached 140mph in 34 sec. Now that's alot of E.
fscott
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I think Pyro said 100% fuel in the P-51 is overload. Testing should be done with 75% fuel.
While full is considered full wing tanks and an empty fuselage tank, we have to take 25% in it. This is still below the point at which the center of gravity changes though, which is the indicator (in the 51) of overload.
- Jig
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If those numbers fscott just posted are right, something definately needs checking into. The p51 should have one of the lowest drag coeffiecients of any WWII fighter. The F4u should have one of the worst (radial, carburator intakes in wings, bent wings). The n1k gliding for 48 seconds, now that's just insane if correct.
I think I'll try something similar to this with 25% fuel and see what happens.
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bloom25
THUNDERBIRDS
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Ill bet it took you most of those 48 seconds to get it to leave the 200mph mark. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
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1. F = m a. For a given amount of drag force, a heavier plane will slow down at a lower rate.
2. At those speeds, induced drag is a big factor. Streamlining of the fuselage becomes less important than lift/drag ratio of the wings.
[This message has been edited by funked (edited 10-22-2000).]
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Ok
N1K2-J loaded weight: 8,818lbs.
F4U-1D loaded weight: 11,887lbs
P-51D loaded weight: 10,100lbs
P-47D-25RE loaded weight: 14,600lbs
Got the weights from Joe Baugher's pages, since it's all the reference I've got. Since the N1K2 is the lightest of the bunch it should drop speed faster, right?
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
"My art is the wings of an aircraft through the skies, my music the deep hum of a prop as it slices the air, my thrill the thunder of guns tearing asunder an enemy plane."
Flakbait
19 September 2000
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Ok, here are some more results from testing. I tested nearly all of the planes by the following method:
First of all, take off at a1 offline and proceed to 7k EXACTLY. Loadout was always the very top guns package, 25% fuel, NO ordinance of any kind( bombs, rockets or dts). At 7k stabilize speed at 200mph and cut the engine, be sure not to allow the speed to be accelerating in any way, this would cause errors. CT was off (I tested with it on and it didn't seem to effect anything though.)
Here are my results:
plane: Time (seconds):
A6M5 11
109F4 21
109g10 19
c202 48
c205 52
f4u-1c 25
f4u-1d 26
190a5 26
190a8 23 *
la5 1:42
N1k 1:17
P51d 20
P47-d30 30 **
spit9 15
spit5 13
yak9u 15
typhoon 18
p38l 1:18 ***
c47 (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) 58
* 190A8 stalled at this time
** P47-d30 is unable to finish test, stalls at time stated
*** p38l will not finish test, stalled at 105 mph at the stated time.
Error: +/- 2 seconds max
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I don't want to make any conclusions at this point. The results certainly surprised me.
Please test yourself and post your results so we can average them.
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bloom25
THUNDERBIRDS
[This message has been edited by bloom25 (edited 10-22-2000).]
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I might add that I did not test the 109g2, g6, and the p47-d25. I wouldn't expect much difference between them though.
(The la5 can almost fly across the map with the engine off, that 1:42 really is 1 minute, 42 seconds, and it would have continued for a few more seconds below 100mph. (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif) )
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bloom25
THUNDERBIRDS
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Ok, I said I wouldn't, but I JUST have to. My opinions gained through testing repeatable by the above method are:
The la5 (too bad because I fly this plane A LOT) time is WAY off.
F4u-1c compared to F4u-1d, seems correct IMO, the 1c has more drag.
The n1k is also way off.
The p51 should take longer to decelerate than the f4u or the p47. Something is truly wrong here. We are talking at least a 20% difference in the wrong direction according to my results. IMO the p51 should glide the longest.
The p38l seems about right IMO in comparison to others, large wing area and very large mass.
Spitfire - engine = beware of falling rocks
Zeros - engine = poor gliders
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bloom25
THUNDERBIRDS
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Just an observation but the P38 stall speed seems too high <gets out recently aquired P38 pilots operating manual>
"Stalls power off
Flaps and gear up
Speeds IAS in Mph
15,000Lbs Gross......94mph
17,000lbs Gross......100mph
19,000lbs Gross......105mph"
In the Landing Distance charts it quotes distances for the 38L model at weights of 14,000 and 16,000 lbs so I would have thought an aircraft with full guns but no ord and 25% fuel comes in at the 15,000lb area.
That seems to suggest that the stall should be about 95MPh IAS - stall at 105 is 10mph to early - that's a lot.
Also are the gauges in Knots or mph?? I'm used to flying with gauges in Knots so assumed they in Knots - if that is so then 105 IAS in knots is about 120mph and that's even worse...
Sparks
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Here's a couple more results from 300 to 100 mph for the planes that seem the farthest off to me: NOTE: All speeds were measured in TAS, NOT IAS for all measurements. (The red dash on the meter.)
plane time (s)
p51d 44
f4u-1c 50
n1k 1:57
la5 2:27
It's also important to note that in testing the speed decrease vs time was no where near linear. It generally looked linear until about 150 TAS, then declined MUCH slower. In the case of the la5 and n1k they drop from 300 to 200 at about the same rate as the p51, but from 150 on down they decay more like a e^(-t) function. The p51 and F4u continue to lose speed rapidly. (The la5 will have the stall horn sounding for about 30 seconds from 110 down to 100. At exactly 100 TAS it will stall to the left.
(Sparks, the TAS vs IAS is the reason for the stall speed discrepency, the IAS was reading around 100 mph then.)
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bloom25
THUNDERBIRDS
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OK Flakbait you got the weights. Now what is the drag on each of those planes as a function of IAS at 1g? Once you get that then we need to solve a 2nd order non-linear differential equation (via numerical integration i.e. building a simulation) and then we can make a meaningful comparison between theory and the experimental results posted in this thread.
[This message has been edited by funked (edited 10-22-2000).]
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Fscott I tried to duplicate your test and I get 24 seconds for the N1K2.
Did you actually hold the plane at 1000 feet or did you use the autolevel trim? Not the same thing unfortunately.
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Funked I'm no math expert, or any good in aerodynamics. The only reason I can figure recoil, or muzzle energy, is because I've got a lengthy explination on how it's done. I wonder if wells could whip something up?
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
"My art is the wings of an aircraft through the skies, my music the deep hum of a prop as it slices the air, my thrill the thunder of guns tearing asunder an enemy plane."
Flakbait
19 September 2000
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Bloom25, very nice statistics, I'm sure I don't that much time to do all those tests.
Ok folks, bloom25 has some very good numbers here, and it's obvious that a few planes could be off, way off. Does this strike any of you as unusual? We all demand accuracy in flight models. I assume we are all ok with these numbers? IF we aren't, then we need to let HT know about it.
Funked, I like pollocks so I will answer you. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif) I am not sure how you got 24 seconds. Ther dang thing will ride at 140mph for 15 seconds almost that long! Bloom25 also got some rather large numbers for the N1K2. I think you may want to be sure you are holding the plane level. I did not use trim of any kind. All trim was centered prior to flight.
he enxt thing I'm gonna do is compare the same tests against Warbirds flight modelling. Let's face it, most of us were probably Warbirders and some of us actually swore by those flight models. I'll try to get around to it son. If not, Bloom25 could you do some in WB also? Smae setup, same attributes.
fscott
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Please don't ride me about my typing. Yes I can spell, I just type too fast and use two fingers. No I did not call you "son", that was meant to be "soon."
fscott
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bloom
some hints for your test:
1)
When you cut engine in La-5 (or N1K)her propeller stops, and when you cut engine in Yak(or P-51) her propeller continue rotation.
2)
It's better to test decreasing of speed in 250-150 mhp range because at 100 mph planes getting stall and autotrim can not keep them in level flight.
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Flakbait yes Wells could whip something up. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
Fscott, I'm not Polish, and as my own tests give much different results, I must continue to question the validity of the numbers on this thread.
Here is the procedure I used to match your numbers (Fscott):
Load aircraft to 100% fuel, full ammo, no external stores.
Take off, climb and maintain 1,000 feet.
Establish airspeed at 200 mph TAS.
Turn off the engine.
Hold plane 1000 feet by applying increasing back pressure with stick.
Record time from engine cut-off until 100 mph TAS is reached.
To match Bloom's numbers I did the same test but with 25% fuel, and 7,000 feet altitude.
I've done a fair amount of virtual test flying but I can't match the numbers either of you are getting. This means either one of us is varying from the stated procedure, or (God forbid) our FE software is giving different results.
I'm going to do the test again and post a film. I advise you guys to do the same. Any other pilots who are bored might wish to do it also. Let's see if we can find out if it is procedure or software.
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I used auto level as soon as I reached 7000ft, then let it stabilize at that altitude and 200 mph. Now cut engine and see how long it takes to get to 100 mph. (Or in the case of a few planes when they spin.)
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bloom25
THUNDERBIRDS
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OK Bloom can you do it again without autolevel? The planes behave very different under autolevel - some of them hold altitude while others don't. As you know, the ones that drop altitude will deccelerate slower due to the potential energy of gravity.
[This message has been edited by funked (edited 10-22-2000).]
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OK I was finally able to get close to Fscott's N1K2-J number. It was my fault, I was doing the procedure wrong.
Instead of setting throttle to hold 200 TAS I was idling the throttle at 250 then cutting the engine as speed dropped to 200.
My time went from 24 to 45 seconds when I made that change.
With the throttle at idle, the blades will go to fine pitch in order to maintain RPM. Then when you cut the engine the blades stay there.
If you hold throttle to maintain 200 mph, the blades will go to an intermediate (coarse) pitch setting, then stay there when the engine is switched off.
Fine pitch creates more drag than coarse pitch, which explains the difference in coast times from 200 to 100 mph.
Since every plane is going to have different prop drag characteristics and a different pitch setting to hold 200 mph, you will get different amounts of drag from the prop on different planes.
It looks like the HTC guys are right, we are mostly measuring prop drag with this test.
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It looks like the HTC guys are right, we are mostly measuring prop drag with this test.
Which basically says - "...can we have a prop pitch indicator in our cockpits please as well as manual pitch control where it was available..."
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lynx
13 Sqn RAF
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I posted this in another thread [Interesting test results] in regards to the N1K2. I was able to pull a roughly 180 degree turn, in blackout, with only 50mph speed loss. I put the field off to one side as a marker, waited for 300mph, then hauled it around. When I checked the speed, after the lights came back on, I had only lost 50mph.
N1K2 film (http://www.worldaccessnet.com/~delta6/htbin/film8.ahf)
This is either beyond strange, and a one shot occurance, or a SNAFU.
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
"My art is the wings of an aircraft through the skies, my music the deep hum of a prop as it slices the air, my thrill the thunder of guns tearing asunder an enemy plane."
Flakbait
19 September 2000
[This message has been edited by flakbait (edited 10-23-2000).]
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Flakbait:
Film link is broken for me.
I was able to duplicate the result though.
What makes you think a real N1K2 could not do that?
(That's a real question not a smart bellybutton remark.)
[This message has been edited by funked (edited 10-23-2000).]
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Fixed the link.
It's a feeling I get when I can pull stunts like that, Funked. An aircraft that can pull 6+ Gs for 180 degrees yet only lose 50mph of speed. To me that's strange. Weight is obviously a large factor in speed retention, yet the N1K2 weighs 3/4 of a ton less than a P-51 [8,818lbs vs. 10,600lbs]. Power loading now comes into play, I think. I won't even try to figure everything, since I know I'll get it wrong. What I've got so far is this. The N1K2 has 4.43lbs/hp, and a Fw-190A3 has 4.90lbs/hp. Which means the A3 should do the same thing the N1K2 is capable of, right? I use the A3 as an example, since the web site I raided didn't list a weight for the A5.
I'll stop there, since I don't want to screw up and bring a firestorm down. If the N1K2 is fine, and either Pyro or HiTech say it is, I'll shut my trap and be done with it. No sense fixing what isn't broken. But I think it is broken, in order for performance of that magnitude to be common place something is up. It could be HTC picked the wrong plane to put it, or that a typo snuck in the code. I honestly don't know.
My gut says something is wrong here, and I am well aware Pyro and HiTech outrank my gut. What it could be I don't know, but performance like that is not normal for most aircraft. It might be that none of the aircraft mush when you pull up hard. Or it could be drag of some sort is too low. I feel drag with power off isn't enough, but that's another thread.
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
"My art is the wings of an aircraft through the skies, my music the deep hum of a prop as it slices the air, my thrill the thunder of guns tearing asunder an enemy plane."
Flakbait
19 September 2000
[This message has been edited by flakbait (edited 10-23-2000).]
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Flak did you read Wells' thread on E-retention?
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Sorta skimmed it, but I haven't really gone through it yet. Why do you ask?
[edit] just tried reading the thread, but it was deleted.
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Flakbait
Delta 6's Flight School (http://www.worldaccessnet.com/~delta6)
"My art is the wings of an aircraft through the skies, my music the deep hum of a prop as it slices the air, my thrill the thunder of guns tearing asunder an enemy plane."
Flakbait
19 September 2000
[This message has been edited by flakbait (edited 10-23-2000).]