Bulldog and Tight Turns

[JP1]

I was wondering what is possible in the Bulldog with regard to constant tight turns, whereby speed, and height are maintained. What is the rate of G experienced, speed and bank angle?

And if you're prepared to lose height in the turn what can you push to..

Disclaimer....

I am not planning to do this exercise and kill myself. I have an aero lesson booked for it. But since I didn't get the chance to speak with my instructor in detail I thought I would ask the PPPrune community for further info. Turns on the buffet were mentioned at banks approaching 80 degrees. Could anyone expand on this further with regard to other parameters, power settings etc etc.

Thanks
JP1

[hugh flung_dung]

Hi John,

All the general info you need is here: http://www.aerospaceweb.org/question/performance/q0146.shtml

Specific points for the Bulldog are that it's a 6g airframe and the max level speed (1g) is pretty close to 120kts. Va (at MAUW) is 142kts. The stall speed (at 1g, MAUW) is 53kts IAS, 58kts EAS.

HFD
Edited to correct the quoted stall speed

[BEagle]

Max possible to sustain in level flight is only around 70 deg AoB and 3G at 2-3000 ft with full power on the buffet nibble.

Descending, you can wind it up to 4.75G at around 100 KIAS with full power. But very tricky to hold accurately on the buffet nibble!

[JP1]

Thanks for the answers...

One final one. What happens if you over cook it.. Will you get one wing stalling first and a guaranteed spin entry or is the effect more benign..

[BEagle]

If the max rate turn is overcooked, you end up in a technical incipient spin with an undemanded roll rate if you are stupid enough not to recognise and recover from the situation.

However, no-one should EVER try to fly a max rate turn until they have been taught how to maintain a max rate level turn on the buffet nibble correctly.

The average PPL holder 'taught' by some wet-behind-the-ears hours builder probably wouldn't have a clue.....

[hugh flung_dung]

It depends on whether you have any sideslip. The default outcome of a stall with sideslip is autorotation and, if you don't do anything about it, a spin. At PPL level many people talk about "the stall speed" and forget that the figure quoted in the POH is at 1g. Have a think about what the stall speed might be at 4g, and then think what it might be at 0g.
The honest answer to your question in this case is "wait and see" :E

HFD

(edited to add that I wish I was a bit more wet behind the ears :O )

[JP1]

HFD

And I would willingly trade some years back for a bit of water behind the ears:) as well as as a couple of inches off the waist:eek:

Fortunately the words stupid, inexperienced and hours builder don't apply in this case..:ok:

[BackPacker]

HFD, that's a very interesting page. I'm going to add that to my aeros notes and Robson book.

Specific points for the Bulldog are that it's a 6g airframe and the max level speed at (1g) is pretty close to 120kts. Va (at MAUW) is 142kts. The stall speed (at 1g) is about 45kts.

Am I wrong, but do these figures not compute? If you assume that the Va is calculated at 6g, should Va not be sqrt(g load) * stall speed at 1g? So it's either Va 110 with Vs 45, or Va 142 with Vs 59?

Somebody put me out of my misery please?

(Oh, and the reason for getting these numbers right is of course so you can calculate the g loading at 120 knots and thus know the bank angle you can achieve at that speed.)

[jabberwok]

(Oh, and the reason for getting these numbers right is of course so you can calculate the g loading at 120 knots and thus know the bank angle you can achieve at that speed.)

Read the page again as you have it the wrong way round. Speed is irrelevant - it's the bank angle that dictates the G load.

For a level turn G = 1/Cos(bank) so that:

Bank Angle----G Load

60-------------2.00
65-------------2.36
70-------------2.92
75-------------3.86
80-------------5.75
81-------------6.39
82-------------7.18
85-------------11.47

At the same time Stall Speed increases as Vs x SQRT(G). If the Bulldog has a Vs of 57.5kts then:

Bank Angle----G Load------Stall

60-------------2.00--------81.3
65-------------2.36--------88.3
70-------------2.92--------98.2
75-------------3.86--------112.9
80-------------5.75--------137.8
81-------------6.39--------145.3
82-------------7.18--------154.1
83-------------8.20--------164.6
84-------------9.56--------177.8
85-------------11.47-------194.7

From the above the limitation for max bank angle is stall speed rather than G.

[BackPacker]

Jabberwork, I was a bit ahead of you. Everything you said with regards to the relation of bank angle and g load is true, provided you have the speed to do so - try pulling an 80-degree angle of bank, 6g turn when you are just above stall speed to see what I mean. (But do it at a safe altitude and with an instructor on board if you've never had spin training!)

The issue here is that the Bulldog, if the numbers are correct, can't reach the speed to pull 6gs, with full throttle in level flight.

You can work out the max gs you can pull based either on Vs or on Va, if the numbers given are all correct. And since the max level speed is 120 knots, that's the speed we want to know the max gs for, and thus can calculate the bank angle.

Based on Vs (1g stall speed) of 45, the calculation works out to 7.1g at 120 knots
Based on Va (6g stall speed) of 142, the calculation works out to 4.1g at 120 knots

That's a HUGE difference which means that either, if you roll a Bulldog into a tight turn, let's say 80 degrees AoB, and pull to the buffet, you either snap out of it at approximately 4g, or you may rip the wings off at 7g. (Exaggerating a bit here obviously but you get the point.)

Note that at 4g the bank angle is 75, and 7g it is 82 degrees, a hardly noticeable difference. So in the first case, limiting your bank angle is not going to help preserve your wings unless you fly extremely accurately.

Personally, my guess is that the Va of 142 is correct and that Vs is 58, with the Vs given by HFD is actually the Vso, the stall speed in landing config. That would mean that you can pull 75 degree AoB and 4gs in a steep turn from level flight. Whether the Bulldog has the power to sustain that is another matter. Beagles response suggests it doesn't.

But that last paragraph is purely a guess: I have never flown the Bulldog and don't have a POH to hand.

[foxmoth]

Max level speed may be 120 kts, but with the extra drag from the manoeuvre you will not keep anything like that, maximum level AoB is around the 75 degrees mark and will vary slightly from aircraft to aircraft depending on engine power (mainly because of the age of the engine and how it has been abused), speed in this will settle at around 95 kts or so.

[hugh flung_dung]

Hmm Backpacker, you're absolutely right that the numbers I gave originally don't compute :O - that's because I said the stall speed was 45 whereas the POH give a Vs1 of 57.5kts EAS (53 IAS) at MAUW. It all goes to show, relying on memory isn't a good thing, even with 700 hours on type.
FWIW VS0 is 50 IAS, 54 EAS.

Apologies for the confusion, I've edited my original to correct the error.

Foxmoth: yes, that's about what we see

HFD

[Fg Off Max Stout]

I'm sure BEags will concur if I say that the RAF-taught way of flying max rate turns in the mighty 'dog was all about looking outside and flying by feel. It certainly wasn't a case of staring at the instruments and rolling to a certain AoB, pulling to a certain 'g' and settling at a certain speed. You would keep your eyes outside rolling and pulling at full throttle until you felt that you were nibbling the stall buffet (no stall warner of course), glancing in momentarily only to check the DI, and the altimeter/VSI. AoB, g and speed achieved would depend on how fat the instructor was and how worn out the engine was, amongst other things.

Good fun but certainly some potential to f--- it up good and proper.

[Knight Paladin]

"Lookout, Attitude (with reference to the OUTSIDE world, not a bloody AI!), Buffet, Height, Speed, G" ...... or some kind of scan along those lines ..... although I've never thought that buffet level should really be part of a 'scan' per se.

[Wessex Boy]

I experienced my first Grey-out as a Pax in a Bulldog pulling a max-rate turn late last year:O

We got to just over 4g and things started to go quiet and a bit 'tunnelly'

Absolutely great fun aeroplane for making big lazy circles in a beautiful blue sky.

I might have a vid of it somewhere, I will look tonight.

Edit: I was too busy greying out in the Max rate turn, but did video the Stall turn amongst other maneouvres:
http://www.youtube.com/watch?v=P6ArzPAnfmM