Turn Radius. Could somebody please explain??

[F4UDOA]

I'm down on the deck in my F4U with less than 50% fuel and ammo when a freshly spawned 109G-10 rears his ugly head and starts making high overhead runs on me. I evade, evade, evade until finally I get him were I want him. He loses e and flat turns on the deck in an atempt to get on my 6. I engage WEP and drop two notches of flap and brake left with the stall buzzer blowing in my ear. I see him directly above my conopy and I assume within two turns I should be looking at his tail in my sights. But then ping blam boom I'm dead.

Why, assuming I weight 12,000lbs (At that point I surely did not) and he was fresh from the hanger with say half fuel and ammo at 6740LBS (A full load would be 7410lbs).
His wing loading would be 6740/173.3= 38.9
My F4U would be 12,000lbs/314=38.21.
Ok thats too close to call right, wrong.
I had half fuel and ammo plus two notches of flap. So what gives? If I'm wrong then somebody explain why. But from everything I have read about the ability of the Bf-109 compaired to the Fw-190 and the P-51 the F4U should turn behind it quite easily. And the relative wing loading agree's with me as well. I am not trying to out turn a spitty here, I am fighting a bloated G-10 with Dragster tires and a blower sticking out of the hood.

Pyro, how to you calculate the sustained turn radius on these birds? I would luv to know?
Also I have seen Jekyll's web pages on this topic and it would seems to match my finding as well.

Thanks F4UDOA

[wells]

If you are trying to get your guns to point at your opponent, it's turn rate you need to worry about, not radius.  Even with a larger circle, the 109 can use yo-yo's to get his nose on you with a better rate of turn (he has flaps too!).  I can almost guarantee that using flaps will reduce your radius but the drag far outweighs the lift and your rate will fall off even more (the only exceptions being the P-38 with one notch and maybe the George).  The plane with the lowest stall speed has the smallest radius.

[F4UDOA]

Actually Wells,

It is the radius that I am speaking of. The F4U was carrier plane and had very good low speed lateral control as well as a low stall speed. Like I said the loaded or empty wing loading of a F4U is much better than a late model 109 with high wing loading. In head to head test with a P-51 and a FW-190 the F4U could turn circles around both of them. And both of those A/C could out turn a 109. Also a Hi yo yo is one thing but thats not what happened. I watched him fly right up my tail pipe. Flat on the deck. Not a yo, yo in the sky. As far as the flaps adding drag. Well 20%flap seeting in an F4U is called a maneuver flap and is meant to reduce the turning circle. According to the Arodynamic text that I have wing loading is the best indicator of turn radius. Then that number is divided by the lift coefficient of the wing to give you an "index" of turning capabilty. So for instance the turning index of a F4U-1D would be 11,803lbs/314=37.6 divided by the lift coefficient which is 1.88 (2.33 prior to the leading edge spoiler strip). Which gives you an index number of 19.99. The lower the better. A P-51D would be
9500/233.19=40.73 divided by lift coeficient of 1.89=21.55 or a little worse than the F4U-1D. If anybody knows the lift coefficient of the Bf-109 just figure it out and post it please. But wing loading is your best off the cuff indicator.  

Thanks
F4UDOA



[This message has been edited by F4UDOA (edited 05-01-2000).]

[RAM]

And did you think in the chance of it being a 109F4?...its not so different from a G10

Anyway, what wells says. If you turn with a 109 down in the deck with a F4U...well you saw the results   .

------------------
Ram, out

Fw190D9? Ta152H1? The truth is out there
JG2 "Richthofen"

 

[This message has been edited by RAM (edited 05-01-2000).]

[RAM]

EEEEKSSS!! <COUGH COUGH!!!>
AAAARG!!!!


A FW190 OUT TURNIGN A Me109?!?!?!??! WTF!??!?!?!


you are GROSSLY wrong!!!!


and, again...wasnt it a 109F4? why are you so sure it was a G10?

[wells]

F4u,

A smaller radius does not mean 'turn circles around'.  

Here's some math for you...

One plane has a turning radius of say 500' and a sustained turning speed of 150 mph

Another plane has a turning radius of 600' but a sustained turning speed of 200 mph.  Which one turns 'faster'?

A hint...not the first one

Flaps should only be used as an offensive tool (or when landing) to 'ensure' a kill.  They will increase your turn rate temporarily, until the speed loss outweighs the turn rate, so only a few seconds, after which, your turn rate will be lower than before.  The exceptions to this are those which have flaps that increase wing area before increasing the Cl, such as the P-38's fowler flaps and maybe the butterfly flaps on the George.

[F4UDOA]

RAM,

Yes I am very sure it was a G-10.
I asked as soon as I pick the shrapnel out of my arse. The offending pilot was glad to tell me what he was flying. No problem really.

If you are sure about the capabilities of the 109G-10 could you please post what you think the correct wing loading ad lift coefficient should be? I have the G-10 listed at 7410lbs loaded with a wing area of 173.3ft.

I am also looking at the empty wing loading which is even more slanted toward the F4U-1D.
Empty weight being 8971lbs wing area 314 wing loading=28.57.
BF-109G10 empty weight=6070lbs and wing area
=173.3 wing loading=35.02.
Maybe the F-4 fairs better in this comparison but the G10 does not.

F4UDOA

[F4UDOA]

Wells,

Stay with me on this because I think you understand what I'm saying. If I am turn slower I will have a smaller radius faster will have a larger radius but will exit the turn faster. Fine. But for the puposes of getting a tail shot I want a smaller radius.
Which should bring me into firing position.
Being faster in a turn in that case would be a disadvantage because it woud lead him in front of me or just plain overshoot. But their is no way he should get a "six" shot from a conopy to canopy start.
By your logic a faster circle is better than a smaller circle for ACM. If so why would the Zero be such and effective fighter at low speed. I was at 120IAS, we were in a slow left turn. In two turns he was on my 6. Why???

F4UDOA
Please don't turn this into a flame fest.
I just want a conversation with out the BS

[Kieren]

Personally, I would rather be the 109 in that situation...

[wells]

Clmax of 109 is about 1.4
Cdimax = 0.10

F4u Clmax = 1.88
F4u Cdimax = 0.21

Cdimax * WA (109) = 0.10 * 173 = 17.3
Cdimax * WA (F4u) = 0.21 * 314 = 65.9

So the F4u has almost 4 times as much drag in a max rate turn than a 109 (at a given speed). Does it have 4 times the power to overcome that drag?  Not even close.  The sustained turning speed of the F4u is going to be much lower than the 109's.

[wells]

F4U,

Turn 'rate' means getting ones nose pointed in the right direction faster.  The plane with the faster turn 'rate' can always get it's nose on target.  It's a delicate balance though, being too fast will result in too larger a radius and rate will be slower, likewise, the inverse is true (this is what I think happened to you in that fight).  Your speed was simply too slow for the radius and your turn rate suffered.  Time for some offline testing, I guess.

[wells]

Here's what I measured in AH (50% fuel loads)

109G10, sustained turn speed 180 mph, 28s for 360 degrees

F4u-1D, 140 mph, 30 s

Radii are

109G10 - 1176'
F4u-1D - 980'

The 109 does indeed get it's nose around a bit faster, albeit with a larger radius.

[F4UDOA]

Wells,

Great job of explaining. I am a long time aviation guy but a newbie in the aerodynamic calculations. I am reading my text to keep up with you but you seem to be giving me the info I am looking for. I was trying not to get into a pissing match with the flame artist on this board. I will respond as soon as I run some calculations on some other A/C for contrast.

Thanks Again
F4UDOA

[F4UDOA]

Wells,

How did you measure radius from your offline testing? How did you determine your best sustained turn speed? Was it 3G speed turn you were measuring?

F4UDOA

[wells]

I just looked at the IAS while pulling as much as I dared with the stall horn blaring in a level turn.  The radius can be figured by timing the turn at a constant speed.  

For the F4u, it flew at 140 mph for 30 seconds, so it flew a distance of 1.1666 miles (the circumference of the circle).  Divide by pi to get diameter, then divide that by 2 to get the radius.