Author Topic: Turn rate and radius questions (Read 3906 times)

F4UDOA · « **Reply #45 on:** May 12, 2003, 03:29:28 PM »

Gripen/Dtango,

I did do test that compared sustain and instantious turns.

What I could not do, that I am whining about are instantious turns at givin speeds attempting to reach the specified G load(on the chart). I could not match these.

I also have these charts for the F8F, F7F, P-38L, and P-51B/D.

Out of all of these charts the F4U has the ability at a gross weight of 12,000LBS (a full combat load) it can pull the highest G at the Lowest speed of any at it's gross weight. The only possible exception is the P-38 which list no weight for G pulled. However the P-38 also has a 6G limit which I find to be surpisingly low.

Another interesting item is the P-51 chart which shows acceleration limits at a minimum weight of 8,000LBS. It tells you to take a max load figure of 64,000lbs(8G limit at 8,000LBS) and divide it by the higher weight to reach the new load figure. For instance at 9,000lbs the max G figure would be 7.1 G's.

It also list a 2.5G stall at 150MPH. At an adjusted gross weight of 9,000LBS the stall would be 2.22G's

For comparison use the F4U-1 chart to notice that the 2.5G stall is at approx 128Knots or 148MPH at 12,000LBS.

So even with a light P-51D a fully loaded F4U should be able to pull more G that a relatively light P-51D.

When the F4U weight is adjusted to a more modest 11,000LBS used the same G limit calculation as the P-51 the 2.5G limit is reached at 120knots or 138MPH. A pretty fair advantage over the P-51D.

I do not feel that this is represented in AH. I have done many test to show this as well as present a litirary ton of data to back it up.

In fact I have 2 other documents to show the F4U accelerated stalls to be well within these guildlines if not lower.

If this is whining then so be it.

gripen · « **Reply #46 on:** May 12, 2003, 05:24:25 PM »

F4UDOA,
As noted above, you should do testing as pull ups to get comparable data with that manual chart. Load a F4U to about 12000 lbs, climb to say 10k and do series of accelerated stalls (pull up until stall happens) from level flight (or dive) and use filming option to record data (you can read speed and max g load afterwards from the film at the moment of the stall). Then just compare your data to 10k curve from the manual. Similar test using turning would result about 10% lower g load at the moment of the stall at same speed.

For the P-51D there is very good flight tested data available from NACA technical report server:

NACA TN 1044

NACA TN 1719

NACA Report 1219

Note that below mach 0,64 buffeting boundary and stall boundary are same in the case of the P-51D (it is stated several times in NACA Report 1219 and TN 1719). Above mach 0,64 buffeting is caused by compressebility, therefore charts in the NACA TN 1719 are directly comparable with the chart in the F4U manual, just calculate IAS speeds to mach values at given altitudes.

Note also that "Airplane normal force coefficient" (CN=nW/qS) in the NACA 1219 and NACA TN 1719 is same as Clmax calculation (Clmax=WAz/qS) in the NACA TN 1044, so these reports give good and accurate Clmax data too. Beauty of these reports are that there is separate data sets for the pull ups and turns. It should be also noted that reports supports each other pretty well and data sets are quite large. Using Clmax you can calculate flight envelopes for any given flying weight and there is also data for some other planes which are present in the AH (P-38, F6F and P-39) in the NACA TN 1044.

Happy testing!

gripen

frank3 · « **Reply #47 on:** May 13, 2003, 10:04:14 AM »

oh my god! my head's almost exploding of all these numbers, static's and long texts

HoHun · « **Reply #48 on:** May 15, 2003, 05:48:05 PM »

Hi F4UDOA,

>I also have these charts for the F8F, F7F, P-38L, and P-51B/D.

That's good data! :-) Are they available online anywhere?

Some more food for thought: The accelerated stall limits in the Operating Flight Limits charts (and I suppose in Badboy's charts, too) seem to be calculated without consideration of propeller slipstream.

Power-on stall speed usually is lower than power-off stall speed, and according to some wartime reports I've seen, fighters should normally be able to turn tighter at low speeds and low Gs than suggested by the flight limit charts.

(You could visualize it as a low-speed/low-G upward bump in the accelerated stall speed graph above, or in Badboy's diagram too.)

Another thing to consider is that these flight limits charts probably are for air speeds as indicated by the airspeed indicator, so you have to be cautious when comparing different aircraft types because they might have different errors in their respective indication.

Regards,

Henning (HoHun)

bfreek · « **Reply #49 on:** May 15, 2003, 07:41:02 PM »

this is giving me indegestion, doesn't how fat the pilot is matter?

F4UDOA · « **Reply #50 on:** May 15, 2003, 07:47:14 PM »

HoHun,

I can post these charts or Email them. Which ever you prefer.

Also I asked the same question about prop slip stream to Zigrat. According to him (In my understanding anyway) it doesn't make nearly as much differance in accelerated conditions as it does in 1G flight because the AOA reduces the slipstream effect.

However in 1G flight slip steam increases Clmax dramatically.

FYI. I have all of the CAS correction charts as well. The CAS speed for the 3G stall of the F4U is 164MPH from 161MPH. I can post those as well.

F4UDOA · « **Reply #51 on:** May 15, 2003, 08:14:31 PM »

BTW,

I have done the accelerated stalls as Gripen defined.

At 10K using the technique Gripen defined I attempted to match the 3G stall number indicated in the chart.

At an idle condition diving at approximately a 35 degree from 11K angle I accelerated to speeds of 160, 180 and 200MPH. It seems I could only achieve a 3G stall at a speed of approx 200MPH.

This is about 35MPH over the charted speeds. I was at 75% fuel so the weight was a couple hundred pounds light as well.

I will post the test I did. But instead of picking my test apart I would like to see someone take a shot at this other than me.

gripen · « **Reply #52 on:** May 16, 2003, 05:32:17 PM »

F4UDOA,
Hm... I have a vintage AH 1.06 here and I got 3,4-3,7 g at 200 mph IAS and 10k (several runs without filming). There was no big difference between power on or of, less than 0,3 g. I used the F4U-1D, 75% fuel. Flight model might have changed since 1.06.

Anyway, power on stall is what we are interested about. Test data in the NACA TN 1719 is power on and power off in the NACA TN 1044, the NACA 1219 tests were with various power settings (more close to power on). There appears to be about 0,5 g difference if compared to manual chart of the F4U (assuming 1 knot = 1,15 mph).

gripen

F4UDOA · « **Reply #53 on:** May 17, 2003, 01:01:48 PM »

Gripen,

1.06? Is that pre digi film viewer?

I did film and viewed it on the external film viewer.

And I believe the F4U FM got heavier in 1.08.

I will post my film but I am not even close to 3G's at 165MPH.

BTW, Half a G is pretty significant and our test are about 300LBS lighter that the chart calls for.

Also if your right, and the differance is between 165MPH and 200MPH. Thats not really close.

I hardly think the Spitfire crew would be pleased if they were stalling at 30MPH higher than they should.

Zigrat · « **Reply #54 on:** May 17, 2003, 05:55:12 PM »

fyi external viewer gives tas not ias

gripen · « **Reply #55 on:** May 17, 2003, 06:01:13 PM »

F4UDOA,
I have AH 1.1X something in another box somewhere else and I'm too lazy to dl 35 megs with modem right now. Anyway, relative maneuverability appears to be in correct order; Fw 190A-5 did about 3,5 g at 200 mph IAS (with quite sharp stall) and Spit IX did well over 4. So why are you complaining? One well known writer wrote once that relative accuracy is more important than absolute in the WWII flight simulators.

gripen

Badboy · « **Reply #56 on:** May 17, 2003, 06:46:09 PM »

Quote

Originally posted by gripen
One well known writer wrote once that relative accuracy is more important than absolute in the WWII flight simulators.

Wise words indeed

Badboy

F4UDOA · « **Reply #57 on:** May 17, 2003, 09:38:35 PM »

How is a FW190A5, an Aircraft with wing loading in the neighborhood of 44LBS/Sq ft turn as well as an A/C with Wing loading at 38LBS/SQ ft?

Is this relatively close? In fact closer than the differance between Spit IX (35LBS/SQ ft fully loaded) and the F4U-1D.

Why not just make it a 2D arcade game with pretty pictures. Is this relatively close enough for you?

BTW, I don't use any annecdotal arguements to make a point. Either I have documentation that matches or I don't.

When I'm wrong I'm wrong because the engineering says so. But when I right don't tell me it's close enough.

gripen · « **Reply #58 on:** May 18, 2003, 04:24:01 AM »

F4UDOA,
Well, why don't you just stop whining and enjoy the game? A simulator is it's own universe. Fly Spit or A6M if you want to turn. As another writer once wrote, you are hammering your head on wall.

gripen

F4UDOA · « **Reply #59 on:** May 18, 2003, 03:04:43 PM »

Quote

Well, why don't you just stop whining and enjoy the game?

Gripen,

This statement says exactly why I am the way I am and why you are as you are.

I do enjoy the game frequently. I have been a paying customer since the open beta and fly and enjoy AH very much. Where as you not only don't pay to play you don't even have a recent copy.

Quote

Fly Spit or A6M if you want to turn.

I haven't flown the Spit since the beta but I have flown the A6M5 quite a bit. As well as the 109G10, 190, GV's, PT's and some of my other fav's. And I have posted about issue's in many of them.

And frankly your blind criticism without testing or providing any data does not exactly give you the position of calling me a whiner.

whine ( P ) Pronunciation Key (hwn, wn)
v. whined, whin·ing, whines
v. intr.
To utter a plaintive, high-pitched, protracted sound, as in pain, fear, supplication, or complaint.
To complain or protest in a childish fashion.
To produce a sustained noise of relatively high pitch: jet engines whining.

Considering the fact that you are bringing nothing to this post other than to criticize me I think you may be the one doing the most whining.