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TurboJ
24th Mar 2003, 08:53
Hi,

Not sure if this is the right forum, but here goes:

I watched the B52 Bomber take off from RAF Fairford yesterday. As it rotated and climbed into the sky, the spoliers on the wings appeared to deploy ?

With Principles of Flight as one of my ATPL subjects, I am interested to know why it would deploy during a climb when the reasons are to increase drag and/or rate of descent ?

Cheers...........TJ

Jet A1
24th Mar 2003, 09:11
Due to the large wing span the spolier deflection is required to assist aileron control whilst at low speeds. Due to the larger wing span the spolier deflection is more apparent.

On the Boeing and Scarebus, it is often the case at lower speeds the spoliers assist aileron. I think, without going into my books, 10 degs of aileron inpuit on the B737 causes a spoiler deflection so got to be careful when putting into wind aileron during a xwind T/O not to deploy the spoiler cos can cause perf reduction.

boxmover
24th Mar 2003, 15:43
Does the B52 have ailerons or is all the roll control from the spoliers?

dvt
24th Mar 2003, 16:23
Having flown that magnificient beast, I'll tell you that the BUFF (Big Ugly Fat FVCK) does NOT have ailerons. The B52D was the last aircraft to have ailerons. I believe.

The spoilers on the G and H models are more than enough for control, even for precision manuevers like air refueling or MITO's (Min Interval Takeoffs/12 sec spacing). On approach, we set the Spoilers (we call them Airbrakes) to position 4. (4 out of 6 positions) This increases the roll response on approach.

The flaps on a B52 are deployed simply UP or 100% down. Except for engine out, where we use 40% Flaps. When we call for flap extention it can be pretty disorienting because of we go from UP to 100% down. This results in a hugh attitude and trim change. We try to extend them during a descent to minimize altitude deviations. The flaps want to pitch the aircraft up and it helps to have the throttles at idle.

The plane still looks great. They were already 30 years old when I was flying them back in the 1980's. They no longer have a gunner or a navigator, I'm told, since you need complete air superiority to or standoff munitions to employ them. Great bomber, 51-500 pound bombs! Amazingly. There I go getting all teary eyed again. My love affair with Boeing, began with this airplane.

NWSRG
24th Mar 2003, 17:40
There was a programme on the BUFF on Discovery Wings last night. Apparently ailerons would cause twisting of the wings due to their span, and hence change the AoA, so spoilers were used instead. Also said that the B52 might still be flying in 2030! Some of the shots of low level manouvring were fantastic. It was amazing to see something so big fly so nimbly. With the wing span, you were waiting to see the wings snap off in some of those turns!

TurboJ
24th Mar 2003, 19:33
Thanks for the replies.....thats great.

So if the aircraft doesn't have ailerons, do the spoilers replace the function of the ailerons ?

TJ

dvt
24th Mar 2003, 22:09
Yes. The spoilers replace the ailerons.

Another thing about this particular flight control configuration that's odd is that when you roll into a turn you initially have to PUSH on the yoke, stabilize in the bank, and then pull and trim off. Conventionally controlled airplanes generally don't pitch up on you when starting into a turn.

Aerodynamically, I never really knew what was going on. Some egghead tried to explain it to me once, but you just figure out the handling characteristics and get on with the weapons tactics.

I do remember that on one sortie I lost the complete Yaw Damper system. Simple looking inocuous little switch, I never thought must about till it stopped working. Without that Yaw Damper, the handling charateristics became completely alien. It was a wollowing pig. Dutch Rolled the whole way home. The Nav Team filled up a couple of puke bags each that day.

Tinstaafl
25th Mar 2003, 01:36
I wonder if the combination of highly swept wing & spoiler location is causing the pitch-during-roll?

I'd surmise that the loss of lift on the downgoing wing with the roll spoilers mounted towards the wing tips would have the effect of also moving CoP forward, leading to a pitch up.

411A
25th Mar 2003, 15:49
dvt
'Wollowing pig' with an unserviceable yaw damper quite aptly describes another Boeing design....early 707's, with their smaller vertical fins. Ouite a handful if the YD goes bye-bye.

forget
25th Mar 2003, 15:53
411A. UK certified 707's had an extended fin and strake under the fin. This gave, I think, an extra 13 feet in total.

HotDog
28th Mar 2003, 15:56
You can thank D.P. Davies of "Flying The Big Jets", for that totally unnecessary appendage.

stargazer02
28th Mar 2003, 16:22
seems to be very easy for you to comment on this acft since it was on the discovery channel.....
where were you based??? you are now in lands end UK presumably....

mustafagander
28th Mar 2003, 17:27
forget,
As I recall it, all re engined B707s - 120s and 436s - had the ventral strake for yaw control due to much uprated thrust. The design was for about 12,000lb/eng and the JT3D3B gave about 18,000lb, as did the RR Conway
The designers obviously had a bit of redesign on their collective plate.
BTW they also had a wing glove fitted to enhance their high speed performance. The rudder control package became an engineers' nightmare with the way boost came into play as the rudder deflected.
They sure did wallow at high alt without the yaw damper.
Now, what was this thread about again???

Volume
28th Mar 2003, 18:06
dvt : ´Some egghead tried to explain it to me once´

I´ll give it another try ...
It´s quite simple, for a swept wing aircraft inner wing means front of CG, outer wing means aft of CG. If you deploy spoilers on the outer wing, you reduce lift aft of CG which causes the plane to pitch up.
If you use ailerons, you add lift on one side and reduce it on the other, so the effects in pitch rule each other out.
An additional effect is that the airfoil pitching momentum (acting nose down for a positive cambered airfoil) is reduced if deploying spoilers. This makes some planes prone to tailstrike if ground spoilers are deployed, although they are on the mid wing and therefor close to CG.

dvt
28th Mar 2003, 20:37
Ah, thanks egghead! Kidding.

;) ;) ;)

HotDog
28th Mar 2003, 20:45
Quite right Volume, just like pitch control with emergency flap operation. Airplane nose up inbd flaps down and or outbd flaps up. Airplane nose down, inbd flaps up and or outbd flaps down. (NUID)