Blackburn Buccaneer - Aerodynamic parameters/Flight Test results

[Tom355uk]

Evening all, really run up a dead end and this is the last place I can think of that might hold the answer!

I'm trying to produce a digital representation of the Buccaneer Mk2; specifically the flight model in the most accurate manner possible. I've got a set of three crew manuals (ODM, Systems and Weps) and a full maintenance manual but the aero information contained within is very sparse.

I've contacted BAe Heritage at Brough several times without response, and looked through the National Archives and found nothing pertinent.

Has anybody any idea where I could get this information? I found a Cranfield test report on a scale Mk1 wing section but the numbers are provided only for very low speeds.

Ideally, I need all the aerodynamic parameters for the aircraft across the full speed range; CLalpha, CLmax, CDmin, Cma, CNbeta, Induced and Viscous Drag Factor, Roll rates, Pitch coefficients etc.

Any help or assistance to point one in the right direction to obtaining such information would be very much appreciated!

[Basil]

Worth a request in 'Tech Log' or even 'Aviation History and Nostalgia' ?

[Genghis the Engineer]

Once upon a time, when I was a university lecturer in aerospace engineering, I used to have students model and validate their models on old military aircraft. I used to have the students use available drawings, reverse engineer them with ESDU data sheets, then we'd pull the Boscombe Down flight test reports to validate their modelling.

With regard to sets of detailed technical specifications - the crew manuals are the best you'll get at this distance. For aerodynamic shape, frankly, buy the best Airfix kit available and reverse engineer it. We've been known to do that in universities - build the kit, fill it with cement, stick it in the wind tunnel.

There are bits of software like AAA that'll do a good job from your measurements of estimating all of this for you, but to be fair, it might not do such a good job on something relatively exotic like the "coke bottle" Bucc. Much cheaper, and surprisingly good, is X-plane.

dCl/dAoA, Cl.max - those are from wind tunnel results on a whole airframe model, Cdmin is a bit irrelevant - what you actually want there is Cdo, and the Oswald span efficiency factor - from that and standard results you've got the full drag polar; Cd.min is of-course 2Cdo by standard result. Pitching and rolling moment coefficients: in reality the first order derivatives are probably long lost from company archives - you might reverse engineer them from Boscombe Down reports, or again from a model and an ESDU transonic design pack. You want the BDN reports anyway, but I think that either borrowing a teaching wind tunnel and using an airfix kit on a sting, or using ESDU are most likely to work.

G

[Plastic Bonsai]

The most pertinent I remember is Cdo wing body 0.012.

Most you can get close enough with ESDU. I think Clmax was 2.4 with blow. dcl/dalpha 4.5, de/da 0.3

Nv 0.08, Lv -0.03 ish Lxsi -0.2 ish - very powerful in roll.

[walbut]

Tom,

The man you need to contact is John Cowper in the Brough Heritage Group. He was the aerodynamicist responsible for stability and control for many years. The group normally come in to Brough on a Thursday late morning/early afternoon and I still occasionally go and ask him questions (on Hawk) when I am really stuck for information. I will look up the Heritage Group phone number when I am at work tomorrow and PM you the details.

Walbut

[Genghis the Engineer]

The most pertinent I remember is Cdo wing body 0.012.

Most you can get close enough with ESDU. I think Clmax was 2.4 with blow. dcl/dalpha 4.5, de/da 0.3

Nv 0.08, Lv -0.03 ish Lxsi -0.2 ish - very powerful in roll.
No idea who you are Plastic - but my compliments on proving me apparently wrong so interestingly.

A thought on Cl.max - if Vs is in the Pilots Notes, then you can work it out (or check Plastic's figures) so long as you have weight. It'll be:-

Cl.max = (2W)/(1.225 x Vs^2 x reference wing area).

If you're using a fairly modern simulator system working in SI units, use m^2 for wing area, Newtons for weight (multiply kg by 9.80665), m/s for speed. You want to be very careful with getting your units right if going from old aerodynamic data to a modern simulator - they may be using significantly different units, and hence values.


If you know stalling AoA from somewhere (did the aircraft have an AoA gauge?, I don't know, but if there is, this might be in the pilots notes), that gives you dCl/dalpha using a zero/zero reference assuming nominal linearity from zero to stall. It won't quite be, but it's close enough for a crude simulation. Check the units - your simulation package may be using either degrees or radians, and if you use the wrong one, the result will be nonsense.

G

[Tom355uk]

Many thanks chaps, some very valuable input!

Unfortunately wind tunnel tests on an Airfix are out of the question , the resources available won't cover the costs!

I thought I'd end up having to brute force manually calculate a lot of the figures using approximations, but the CD0 and pitch/roll figures from Plastic are immensely helpful. As GTE alluded to, the manuals are all in pounds shillings and pence but the simulator only accepts Euros for the lookup tables so one will need to be extremely careful during the conversion process.

The data within the manuals is also less technical, more real world - i.e do not use more than half stick roll deflection above 0.75 IMN, do not exceed 20 units AOA or buffet boundary whichever is reached first, stall in landing config is reached at 25-26 units AOA.

I did find a CLalpha calculator on the ESDU site that covers the whole subsonic regime for low aspect ratio wings which will also be extremely helpful.

Cheers again guys, I'll let you know how I get on!

[Genghis the Engineer]

Does the maintenance manual contain a calibration chart for the AoA gauge?

G

[Plastic Bonsai]

I used to work with John Cowper, the best boss I ever had. Pleased to know he's still around Walbut. Please pass on my regards.

Also watch out for factors of 2 on the lateral rate derivatives and lateral side forces Tom. Lp used to be -0.4 and it's been devalues to -0.2 in the later non-dimensional form.

[unmanned_droid]

Hi Tom,

What sim software are you using?

I released a couple of models of the Buccaneer for X-plane - it was some time ago but I might still have a copy somewhere.

[walbut]

Tom,

The Blackburn Heritage people are aware of your request and will be in contact shortly.

Walbut

[thunderbird7]

It's all wibble to me but does this (http://airfoiltools.com/airfoil/details?airfoil=n63415-il) website help?

[Tom355uk]

Does the maintenance manual contain a calibration chart for the AoA gauge?

The AoA gauge on the Buccaneer was driven by the Airstream Direction Detector, a fixed incidence probe on the starboard nose cone that used the differential air pressure in a horizontally divided paddle chamber to deduce the current angle of attack.

The Blackburn Heritage people are aware of your request and will be in contact shortly.

roger, email received!

[Genghis the Engineer]

In case the reason for my question wasn't obvious - if you have faith in your AoA indications, and know stalling AoA as well as CL.max, then you have dCl/Dalpha - at least if you assume linearity which should be true for most of the way from zero alpha/zero lift (if that is the case) to the stall.

G

[BEagle]

Bucc ADD indications were in units ('bananas') rather than degrees.

I don't know whether any units:alpha calibration curves were available though.

[Genghis the Engineer]

Ah, that was the question. It must exist somewhere - but of course unless that's somewhere Tom can source, not much use.

G

[Vitesse]

I do hope the OP'S effort is for the DCS simulator.

That has a nice Red Flag NTTR scenery which would suit the Buccaneer nicely.

Good luck, anyway.

[LOMCEVAK]

Whatever numbers anyone has for lift curve slope, aero derivatives etc they must to related to both Mach number and Reynolds number because the flying qualities and aerodynamic characteristics varied markedly with Mach and airspeed.

The ADD limit was 20 units in all configurations, and at low speed (less than about 300 KIAS when on internal fuel) with flap and droop 0-0-0 this was reached well before any buffet. At ADDs approaching the stall a pitch up developed and there was insufficient tailplane authority to counter it such that a loss of control was inevitable. Therefore, simple considerations of CL max are not really valid as the high AOA characteristics were very complex. Between about 300 KIAS and corner speed (about 450 KIAS with no stores and internal fuel) there was a good buffet margin which occurred at less than 20 ADD. In the blown approach configurations (30-20-20 and 45-25-25) there was again no buffet at 20 ADD which, as well as being the limit, was the value used on the approach. The only time when a slightly higher ADD was sometimes used was on an unblown 45-10-10 approach when you could go to about 20.5 units. Note that the aircraft had an audio ADD system that was the prime data source to the pilot; the gauge was not really used.

There were some interesting characteristics at high IAS and high Mach. Tailplane power reduced quite markedly at high Mach numbers (which is probably why complete loops were not cleared). Directional stability also reduced at high IAS and I believe that intake momentum drag was one contributory factor. This meant that above about 550 KIAS the aircraft would not fly slipball central but needed a small sideslip angle to achieve directional stability. Also, at high IAS the roll performance reduced dramatically, I believe due to wing twisting moments from the ailerons, although high Lv and adverse yaw could also have been a factor.

One other consideration is that full forward stick to full aft stick did not give the complete range of tailplane movement; the trim tailplane angle determined the range of movement.

You have chosen to try to model an aircraft with some of the most complex flying qualities that I have known, especially at low speed or very high speed. But from about 350 - 550 KIAS at low level it was incomparably good!

[LOMCEVAK]

I think that the major problem that you will have will be the landing pattern because you have no blow/BLC system. the blow cut in when the ailerons drooped through 20 degrees 12 degrees in an early mod state, and this did result in a very strong nose down pitching moment which is why the tailplane flaps were fitted and their positions were indicated in the cockpit by gauges with a black background and a yellow sector to indicate the surface position,(cheeses)and both had to move together or you would lose control in pitch and therefore, there was a mantra to be spoken after each selection "cheeses moving together, cheeses stopped "tgether also, you could not reduce power too much on the approach or else you would lose blow pressure there were 3 blow pressure gauges that you had to keep checking

but the 45-25-25 the approach speed at 20 AOA was low (127 +2KIAS/1000 lbs of fuel)from memory, sadly it has been a long time since I last flew one but unblown 45-10-10- it was 146 KIAS=+1KIAS/1000 lbs fuel.

the audio AOA system was interesting, it had a steady note when at 20 AOA i.e.. on speed for the approach plus a series of beeps if the AOA was too high .i.e. .you were too fast and a series of burps if the AOA was too high i.e. you were too slow

an interesting aside about the audio AOA, is that the British F4Ks /FG1s)had the same audio system but the beeps and burps worked in the opposite sense; I was probably one of the few pilots who ever maintained currency on both types simultaneously I had grown up on the Buccaneer so I used the audio on that but in the Phantom, I would use the steady note on the approach if it sounded but otherwise I used the AOA gauge on the approach, and at the same time I was current on the FGR2 and occasionally on the F4J(UK) neither of which had the audio system