New F4U performance tests

[Optiker]

Widewing,
      I'm curious as to how the test for turn radius and rate is performed. Is there a writeup on how you measure these parameters? I can see how you might perform turn rate by recording compass readings and timing them, but turnradius has me stumped. How is the turn radius measured? And during the testing of the new models, were flaps engaged? How much and when to engage flaps still has me puzzled.

      Any place you can send me to study how flight performance envelopes are measured would be appreciated.

Thanks,

Bill "Optiker" Brady

[Widewing]

I don't know if initial turn rate has changed, it's a difficult metric to measure.
What I do know is that the F4Us seem to retain E better than before. Turn radius for the F4U-1A is the best of the Corsairs and about 20% better than the 109K-4. Climb is about the same as the -1D, but acceleration is slightly better. Zoom climb is excellent. Dive acceleration seems much faster. Saxman noted this too. Unlike previous tests of the F4U-1D done last spring, the F4U-1A really winds it up in a dive. I haven't tested the others beyond the F4U-4, but it appears to have gained as well.

I believe that the torque modeling has been changed. When slow with flaps fully out, the Hogs now resist rolling to the right. I'm sure you've experienced this with the 109s. To induce a roll to the right just above stall speed, you must pull back power first. I find that the 109s have the same problem.

My regards,

Widewing

[Rocket]

WW,

      I have noticed a feeling of better E retention.  The zoom seems longer now and getting slowed down once you get a head of steam on in the -1A seems harder.  The roll rate seems different, faster, lighter touch on the controls.  May be just a feel but I like it.  I have been waiting for this hawg for a looong time.  I came back at the right time.  


S!
Rocket

[Saxman]

Lol! Yeah, Rocket. I'm having a hard time slowing down enough to turn after an initial dive, even with gear out and throttle zero. She just holds onto E so well in the zoom and replaces it so well in a dive.

I had a Spit VIII earlier think he was gonna catch me in a dive, and when he broke off even after I had to immelmann to reverse still thought he'd be able to out-zoom me.

Now if only HTC could fix the glass engine, wings and tails...

[MOSQ]

I retested the 1 and 1D, along with the new 1A for turn radius and acceleration.

A few notes first:

1) Widewing typically outturns me in most planes by a little bit. So it's tough to add/compare any of WW's tests to mine and make a definative conclusion. They will be within the ballpark and are good for generalities, but don't go the bank thinking 10 ft difference in turn radius is going to make a hill of beans difference in a fight.

2) Either the flight models have changed for the F4U's or the IAS-TAS bug has made acceleration testing and turn testing inaccurate. The reason I say this is all the F4U's are a LOT faster from 300 mph to 350 mph than they were before. Acceleration times under 300 mph haven't changed much, but over 300 they have...a lot. Which leads me to believe that HTC changed the drag equations for the F4U's, or the airspeed is not being correctly reported on the E6B. Both of these possibilities would account for the faster dive speeds reported by WW and Saxman above. The problem for turn radius testing is that speed is a critical factor and if the E6B is incorrect for the F4Us, then the turn testing will be inaccurate as compared to the rest of the plane set.

So here's my old data compared to the new 3.09:

F4U-1
3.08: 150 to 350: 128 secs, 300 to 350: 76.1 secs
3.09: 150 to 350: 119 secs, 300 to 350: 67.4 secs

3.08: Full Flaps TR: 422 ft, DPS: 19.6
3.09: Full Flaps TR: 419 ft, DPS: 19.6

The turn radius probably didn't change, this is well within experimental error. However the high speed accel is 9 secs faster.

F4U-1D
3.08: 150 to 350: 137 secs, 300 to 350: 89.7
3.09: 150 to 350: 121 secs. 300 to 350: 74.6

3.08: Full Flaps TR: 430 ft
3.09: Full Flaps TR: 434 ft

Same comments as the -1. The TR is probably experimental error. But 15 seconds faster from 300 to 350 mph is significant.

I also tested the No Flaps Intial Turn radius, they are slightly different but again within experimental error and/or the E6B speed bug.

3.09 F4U-1A
150 to 350: 99.8 secs, 300 to 350: 54.1
Full Flaps TR: 425 ft. DPS: 19.3

I haven't tested the F4U-1C but I'd bet it's 300 to 350 time is faster too.

The conclusion: the F4U-1A is significantly faster than the others in high speed acceleration. It just outurns the -1D but a plain -1 will be an even match in a flat turning contest. Like I said above any two planes that are within about 20 ft in turn radius are too close to call in a flat turning contest.

I hope Pyro reads this thread and checks out the true speeds and indicated speeds of the F4U's soon.

[Widewing]

Originally posted by MOSQ

Widewing typically outturns me in most planes by a little bit. So it's tough to add/compare any of WW's tests to mine and make a definative conclusion. They will be within the ballpark and are good for generalities, but don't go the bank thinking 10 ft difference in turn radius is going to make a hill of beans difference in a fight.

You recorded 425 feet for the F4U-1A, I got 422 feet. Considering that we have different computers and probably different flight hardware, as well as our own personal stick settings, I'd say that this is as close as is feasible. Seriously, if I were testing a piece of hardware at a test lab, I'd consider this correlation to be extraordinary.

As to acceleration rates, perhaps the drag model was tweeked again. I'd suggest testing other types and compare that data with previous data to see if it spans the whole of the plane set or is unique to the F4Us.

My regards,

Widewing

[Saxman]

Incidentally, I wasn't judging dive acceleration by the E6B, as at the time I was trying to get the @%$& out of dodge with a full-power WEP dive, but rather by the airspeed indicator on the dash itself.

[MOSQ]

WW you're correct. They have changed the drag for all planes again. The difference is mostly apparent in the planes capable of 350 mph. And it's different depending on the plane.

The Typhoon, P-51D, P-47N, LA-7 only gained 2-3 seconds on their 150 to 350 times.

The FW-190 D9 gained 5 seconds. Ditto the 109-K4.

The FW-190 A8 gained 9 seconds.

So far the biggest winner is the F4U1C, it gained 19 seconds.

I'm not looking forward to retesting all the planes again!!

[Bodhi]

Originally posted by Balsy
If you were flying that thing in REAL combat, you'd kiss that fine piece of metal protecting your grape.

Its all perspective I guess .

Balsy

The piece of metal above you in the canopy is not armor. It is a piece of sheetmetal extended off the frame.  It was there to allow a cut out in the canopy so it could flex easier at the back so it did not crack when sliding it back on to the fuselage.

[Oldman731]

Originally posted by Bodhi
The piece of metal above you in the canopy is not armor. It is a piece of sheetmetal extended off the frame.  It was there to allow a cut out in the canopy so it could flex easier at the back so it did not crack when sliding it back on to the fuselage.

My father-in-law was actually one of the folks who came up with this fix.

- oldman

[Widewing]

Originally posted by Bodhi
The piece of metal above you in the canopy is not armor. It is a piece of sheetmetal extended off the frame.  It was there to allow a cut out in the canopy so it could flex easier at the back so it did not crack when sliding it back on to the fuselage.

I was surprised to see it on the new F4U-4 as most production -4s had the later canopy with full plexiglass. Many ofthe F4U-1Ds also had the later glass...

Image below shows the current F4U-4 canopy...



This next image shows what canopy was fitted to the typical F4U-4...



My regards,

Widewing

[Bodhi]

Originally posted by Widewing
I was surprised to see it on the new F4U-4 as most production -4s had the later canopy with full plexiglass. Many ofthe F4U-1Ds also had the later glass...

Image below shows the current F4U-4 canopy...



This next image shows what canopy was fitted to the typical F4U-4...



My regards,

Widewing

even funnier Widewing is that most production F4u-4's had a flat windscreen (early production still had the rounded front as depicted), including most of  those produced and in service in WW2.  Either way, it does not matter, the views are not a hindrance, know where the nme is, and it is not an issue.

I also think the rear canopy extension is too big.

[Widewing]

Originally posted by Optiker
Widewing,
      I'm curious as to how the test for turn radius and rate is performed. Is there a writeup on how you measure these parameters? I can see how you might perform turn rate by recording compass readings and timing them, but turnradius has me stumped. How is the turn radius measured? And during the testing of the new models, were flaps engaged? How much and when to engage flaps still has me puzzled.

      Any place you can send me to study how flight performance envelopes are measured would be appreciated.

Thanks,

Bill "Optiker" Brady

Testing for turn rate and radius is relatively simple in concept, but not so easy in practice. The aircraft must be flown with great precision right at the edge of the flight envelope. This takes some practice.

The method is as follows:

Set up a reference point to use as the beginning and end of each 360 degree turn. Most of us use the .target command set at some reasonable distance. I use 1,000 yards. Get into a turn, adding flaps as you need them. Engage WEP. You must maintain altitude, not letting the nose drop or wander up. You should have E6B enabled with the clipboard stowed.

When you are flying at the limit, time 3 full 360 degree turns. Check speed each turn. Average the 3 speed readings.

Let's say your average speed was 99 mph. Divide 99 by 60 to obtain Miles Per Minute, or 1.65. Multiply that by 5,280 feet, or 8,712 Feet Per Minute. Divide by 60 seconds, and get 145.2 Feet Per Second. Multiply 145.2 by the total time of the 3 turns. In this case, 54.84 seconds. This will produce 7,962.768 (total distance flown). Divide 7,962.768 by 3 to obtain the circumference of the average circle, or 2,654.256 feet. Divide this by Pi (3.14 will do) to obtain the diameter of the circle, or 845.304 feet. Divide by 2 to obtain the turn radius, or 422.65 feet for the F4U-1A

To calculate average turn rate, multiply 360x3/time, or 19.694 degrees/sec.

My regards,

Widewing

[Optiker]

Widewing,
     Thanks for the procedure - now that you've explained it, the radius calculation makes perfect sense. I can also see that flying a precise circle, without allowing the nose to drift is difficult.
      The statement "Get into a turn, adding flaps as you need them." is more difficult for me to comprehend. I assume during the 3 rotations being averaged, the flap setting is constant, correct? How do you know when and how many notches of flaps to add? Do you perform the test with no flaps, add a notch and re-test, and compare results? Or is there some metric (G loading, speed, instinct) that indicates "Gee, I need to add a notch here".
      Sorry for being a pain, but I started in spits and never used flaps and seemed to do OK. I'm still trying to learn F6F and with correct flap application I think it's going to be an awesome ride.

Thanks again for the writeup and in advance for any assistance you can lend.

"Optiker"

[Widewing]

Originally posted by Optiker
Widewing,
     Thanks for the procedure - now that you've explained it, the radius calculation makes perfect sense. I can also see that flying a precise circle, without allowing the nose to drift is difficult.
      The statement "Get into a turn, adding flaps as you need them." is more difficult for me to comprehend. I assume during the 3 rotations being averaged, the flap setting is constant, correct? How do you know when and how many notches of flaps to add? Do you perform the test with no flaps, add a notch and re-test, and compare results? Or is there some metric (G loading, speed, instinct) that indicates "Gee, I need to add a notch here".
      Sorry for being a pain, but I started in spits and never used flaps and seemed to do OK. I'm still trying to learn F6F and with correct flap application I think it's going to be an awesome ride.

Thanks again for the writeup and in advance for any assistance you can lend.

"Optiker"

Generally speaking, you will develop a feel for when flaps are needed. Many players will use flaps, but often use more than needed and keep them deployed longer than they should. It's really about balancing flap use with the need. You will learn this with practice.

My regards,

Widewing