Roll rate
 

What is the maximum roll rate that can be achieved in a plane like a Boeing 757. I assume this is normally limited by the computer. Is the maximum roll rate affected by air speed? If there was no over-ride, what would be the maximum roll rate?

On the B757 there is no computer that limits roll rate, it's not a fly-by wire system, simply mechanical powered controls with both ailerons and spoilers for roll control. Max roll rate is not relevant in normal operations, one never needs more than a gentle wheel input to achieve what is needed. I can't remember using in the air more than perhaps 20 degrees of the available 90 degrees of wheel movement. On the ground, for takeoff and especially landing with strong x-wind, much more will be used.

That's perhaps a long way of saying I can't answer the question directly, but I can tell you it is speed-dependent, with higher roll rates at higher speeds. TAS or IAS? There's a question!

Incidentally, the flight manual gives no figures and no limits.

Forgive me for offering what amounts to off-topic trivia, but during my BAC111-200 conversion, our flight-controls groundschool instructor - who had worked at BAC - claimed that the roll-rate could equal that of the EE (BAC) Lightning in certain circumstances. As I recall, you needed to have the spoilers slightly extended (i.e., as medium airbrake) to achieve the best roll rate. (The spoilers on the upgoing wing would, of course, then retract.) Whether the speed was the higher the better, and whether that would be IAS or TAS related, I don't know.

Chris

My guess would be IAS... and I would LOVE to see a BAC111 rolled like a Lightning... any clips?

:}

MD

In the simulator it takes six seconds to roll a 727-200 through 360 degrees as part of Jet Upset training.

Here's a lazy-er roll rate (10-11 sec.) in a plane that's not often rolled.

main_dog,
Regret I cannot assist in that area. (And listen, we're talking about roll RATES, not rolling!) :ugh:

Unlike its big sister, the VC10, the One-Elevens all employ manual spring-servo-tab ailerons - not PCUs. Spoiler/Speedbrake surfaces are hydraulically powered, of course.

According to my hand-written course notes (in Doug Realff's lectures at the Bee Hive in 1977, re the 200 series): when speedbrakes (why don't we call them AIRbrakes?) are retracted, they do not lift as roll spoilers until 4deg of aileron, unlike the cruder system on the B707. This avoids spoilers cracking open in gentle turns or with aileron trim, and reduces initial roll rate. 4deg of aileron represents roughly 11 - 15deg of control-wheel movement.

However, with 10deg of speedbrake (half the maximum permitted in flight), the situation is slightly more volatile.
"...as soon as the (control wheel) is (fully) displaced, the spoilers will rise on the downgoing wing (to 43deg)......and the spoilers on the upgoing wing will retract. In this config, maximum roll rate is about 400deg per second."

Returning to the speed issue, the spoiler surfaces are designed to "blow back" at a certain air load. This would probably limit roll rate at high IAS, and presumably applies to all aircraft types. FBW types, no doubt, prevent that happening by limiting roll-rate (although blow-back of the surfaces can still occur in speedbrake mode).

Chris

RAF Gnats at Valley were stop-limited to 270*/sec. The Arrows had no stops and were 360*/sec..

Well, that is a range of responses. Let's make the question more specific.

Say a B 757 was approaching the circuit area, still at high speed, and the pilot had a short blackout. He woke up to discover he had pushed the throttles fully forward and the plane was doing 460 knots, banked at an angle of 80 degrees. Knowing that the plane will be dropping fast, and scared that there might be a plane just below him, the pilot wants to level the wings as fast as possible. Bearing in mind that spoilers will not be involved, how long will it take to get the wings level?

It seems this is not just a question of maximum roll rate that can be achieved; some inertia must be overcome getting the roll started.

I just can't resist chipping in here, as nearly all my years on the 1-11 had me training on the real aircraft. We were also told the story of the roll rate from a man that had flown both types during testing. I was not sure if I believed it, but it gave a bit of street-cred.

At 20k feet or so, I was told to roll the aircraft this way and that - as hard as I liked. I think our speed would have been c 250k. It was quick, but unremarkable, the controls seeming rather heavy.

Several years went by.

I managed to get a very sick aircraft going in Seville, after desperate attempts by engineers had failed. We'd been stuck on the aircraft for 36 hours. When we came to leave, we had no crew oxygen, so headed back to the UK at low level. <10k. Plenty of fuel, 4 crew + 3 engineers.

Somewhere west of the French coast, and at cruising speed, I had a finger thrust under my nose, along with a loud cry of "Mind That!" My reaction must have been adrenalin fueled. Certainly, the ailerons were way past the angle needed to lift a spoiler, and the aircraft virtually snap-rolled. In disbelief, I stopped it with wings past the vertical, and rolled it back the long way. I know, total wimp.

It had rolled faster than anything I'd flown for aerobatics. Period.

(Fortunately, I'd spent quite a lot of time throwing small aircraft around, so managed to keep the huge toolbox stuck to the flightdeck floor during the recovery.)

I've often wondered about that tail. A lot of mass up there - hydraulic and electric motors and the like. A lot of stress in the roll.

Not a thing was ever mentioned about it, and come to think of it, I got no thanks for jerry-rigging the airplane.

Wow. It seems some aircraft can roll fast.

I came across this at Aviation Week:
"Aircraft with very long wings, and in particular airplanes with engines distributed outboard along the wings, tend to have more formidable inertia than airplanes with engines located on the fuselage. The amount of fuel in the wings can also make a considerable difference in an aircraft's roll inertia, as an aircraft with fully loaded wings at the beginning of a long-range flight will have a much higher moment of inertia about the aircraft's longitudinal axis than when those tanks are empty. It takes a lot of force to begin rolling those transports. According to the FAA's Airplane Upset Recovery Training Aid, "This greater inertia must be overcome by the rolling moment to produce a roll acceleration and resulting roll angle, and the effect is a sluggish initial response."

So it seems there can be considerable variation. Specific questions:
Does the B757 deploy spoilers at high speed?
As its engines are some distance out from the body, would it be regarded as sluggish in initiating a roll?
Would the amount of fuel in the tanks make a perceptible difference to the initiation of roll?

One of the fastest rolling aircraft around is the A-4 Skyhawk at up to 720 degrees/sec. Enough roll acceleration to bang your head off the canopy if you aren't the one flying (2 seat versions). Enough roll rate to over-pressurize the wing fuel tank from centrifugal force effects and damage the wing (I've investigated some of the resulting incidents). Max roll rate only allowed for one 360 degree roll before stopping it due to roll-pitch coupling.

Lets not forget Tex Johnson and the B707. This may not have been about rate but certainly balls can be respected..

Acrobatic planes not of interest in this case
 

Can anybody give me a figure for how long it would take in a standard Boeing757 to go from an 80 degree bank to wings level at a high speed?

27 seconds

but why?

Strange that no 757 jockeys appear to have latched on to this thread. Never flew them myself.

But I am also curious to know why you are fixated with the 757, gravity32, and it seems I may not be the only one. :confused:

Fair question?

Why the interest in a Boeing 757?
 

I have been involved in arguments with people over some of the events of 9/11. They are arguing that the official account of the impact of AA77 on the Pentagon cannot be correct because they found a few witnesses who say the plane passed north of the former Citgo gas station. If it did, it could not line up with the damage trail, both outside and inside the Pentagon. They assert the damage was done using explosives, while the plane flew over the top of the Pentagon. No witnesses to the plane flying over the top have been found. These people do not seem to respond to the fact that far more people are on record that the plane hit the Pentagon.

We have radar data showing the plane aiming right at the impact damage at the Pentagon, but it does not go all the way as the plane gets too low for radar. I have done some calculations which show that if the plane curved round the Citgo gas station at the reported 530 mph, it would have to be steeply banked. It has to come out of the left bank then go into a right bank.

There is only one thing missing in my calculations: the time and distance it would take to switch bank from left to right, say 70 degrees each way, assuming maximum control wheel input was used?

My guess is 3 or 4 seconds unless you wanted to rip up the wings but what difference does it make? I always knew I could right the 757 with no problem but probably wouldn't have hacked a stopwatch. I'm sure it would do a great aileron roll. I wish I had done one in the sim. My home flight simulator does it very well but it also does a split S to a landing. I've flown in level flight inverted in the 737 real sim over LAX. It has a very good roll rate so assume the 757 is about the same.

G32, if you didn't care about tearing up the airplane a 70 left to right bank could be accomplished in around three seconds. Wonder where the airplane and all their passengers went after the event? AA587 and TWA800 investigations were both bogus in my opinion but not this one. Coverups are quite common throughout the world to get the public to believe certain things. Hiding a 757 with a bunch of passengers on board that disappeared after being in sight on descent heading for the pentagon at low altitude isn't. Blaming a copilot for aggressive rudder movements and center fuel tank explosions are easier to BS the public with. They were both BS but most of the public went along with it. Airbus and the US government were successful in pulling it off.

Thanks B44. That is a good clear response. If 3 seconds is the quickest the roll could be done, this manoeuvre is out of the question as there are only about 4 seconds available for the whole thing, left turn, roll, right turn. With 3 seconds used up rolling, hardly any turn would occur.

Can anyone find a reason it could be done quicker?

The quickest would be to deploy a bit of spoilers so you have differential spoilers helping the roll rate and using full aileron but you could cause some damage to the aircraft.

I didn't think spoilers could be deployed at such high speed, 460 knots. I thought they would not be needed at high speed as the ailerons would have all the authority anyone would need. I also thought they might be at risk of damage at high speed. Perhaps I am wrong about these things.

If spoilers could be used, and were used, what would be your estimate of roll rate?

Probably around 100 degrees per second with full deflection. Good luck on everything hanging together. I would expect the ailerons to take a lot more stress than the speed brakes would with full deflection.

According to a google search the flight test roll rate exceeded 60 degrees per second at what ever speed they tested it at.

My Google searches have not been fruitful. Where did you find that?

gravity32:

The AA77 maneuvering problem is more basic than just roll rate. Why not chart the supposed course on a city map, using the greatest possible turn radii, then work it as a centrifugal force problem at 530 mph (kts I presume?). At 530 in a 2g turn, the nose just creeps around the horizon. Even if you totally neglect the time required to roll into/out of the required bank, I'll bet you need to make 4 or 5g turns to fly the required course.

With half a second allowed for roll time the radius of turn is 1893 feet, the force is 9.97g, the bank angle 84.3 degrees.

It couldn't survive the g-force and if it did, nobody saw that bank!

B757 Upgrade To B767 — Tech Ops Forum | !!!!!!!!!!!!!!

I couldn't find any official reference to this post 20 and 22 info.

Chris Scott

That's on par with some aerobatic aircraft...

Why would they have configured the control-system to produce such a heavy roll rate all the sudden at maximum control surface deflection? I thought the whole idea is so that it builds up in a predictable manner...


Loose Rivets

Impressive...


Machinbird

I didn't know a plane could roll fast enough to damage itself...

What's roll-pitch coupling?

Envision an aircraft rolling at a high rate with some angle of attack.
The angle of attack displaces the nose above the roll axis and the tail below the roll axis. Centrifugal force from the roll tends to force these extremities away from the roll axis causing a potentially uncontrolled increase in angle of attack.

The A-4 wing fuel tank is a single tank spanning both wings, however if the correct conditions exist, pressure in one wing can exceed the structural strength of the rivets attaching the internal stringers to the wing skins and the stringers to the ribs. One squadron I was in had such an incident and the Blue Angels had one too. Normally it was the port wing experiencing damage. The starboard wing had the fuel dump/overpressure relief valve and was rarely damaged.
Each aircraft has different considerations, but under the right conditions you could overpressurize a wing or throw engines by generating a great enough roll rate.:uhoh:

Machinbird,

So you get a corkscrewing action going?

It seems to me I have asked the wrong question. The term "roll rate" appears to relate to a stabilized process in which the initial inertia has been overcome.

In a plane like a B757 the wings are long, the engines are outboard and the fuel tanks go well out along the wings, so there would be a lot of inertia.

The proper question is not roll rate, but time for a roll of a specific number of degrees. Since flying at 2g is within the permitted range, which has a bank of 60 degrees, does anyone have a figure for the time to go from wings level to 60 degrees, with maximum control wheel input, in a B757?

Depending on speed probably less than a second to reach a 60 degree bank but nobody flies that way because the engines and pylons aren't built to take those forces so even test pilots don't do it. They may withstand it but nobody flies like that. Tell your conspiracy friends about the 9-11 Pentagon crash that it didn't make a 10G turn but vaporized. That is the only explanation for not seeing it depart at high speed. I wonder after the 10 G turn where they were going?

There is of course no doubt the plane hit the Pentagon. There are many witnesses, including three of their star north-of-Citgo witnesses, Lagasse, Turcios and Brooks, who all said they saw the plane hit the Pentagon. Sean Boger from the Control tower at the Pentagon Heliport watched it all the way into the Pentagon. Albert Hemphill at the Navy Annex said it was to his right, and flew straight over the bridge into the Pentagon. There is not one witness to the plane flying over the Pentagon though there were hundreds of cars stuck in traffic around the area.

There is radar data from four installations all leading directly to the Pentagon impact site. Now there is also the FDR file, which has recently been fully decoded, showing the plane flying straight, at the same track angle as the radar, and descending. The last radio height is 4 feet. Add 6 feet for the offset and 16 feet for the height of the wings above the wheels and you get a height that matches the length of the chopped off light poles.

So all the evidence shows the plane hit the Pentagon. Its mass is sufficient to smash the wall. Most of it went inside. There is enough debris outside to account for the parts that were too light to penetrate. The claim the plane flew north-of-citgo is a claim based on no evidence other than a few who were mistaken about something that would not seem important to remember at the time.

You can read about this here:
The Science of 9/11| Pentagon

Worse than that. The aircraft could go completely belly into the wind and convert its roll momentum into yaw momentum (worst case).

gravity32
I wouldn't worry too much what a few borderline psychos have concocted. Reasoning, thinking, men can hear these stories and discard them. Those that embrace these strange theories have an emotional need. That is their problem. All you need to do is firmly state, "That is Bull!!!!!," to indicate you do not want to play their game.

Machinbird

Okay... so as it would roll, centrifugal forces would rapidly drive up the AoA, which then arrests the roll and causes a gigantic sideslip?

Machinbird, these guys are not psychos. They are smart operators who have figured out that they can sell DVDs by creating controversey. They do harm and should be opposed.

My revised calculations show that the plane would have to be banked at 77degrees to perform the proposed ridiculous turn with a g-force of 4.4.

This leads to an interesting question. What is the maximum bank angle that a B757 could fly at and maintain height?

The maximum legal bank is arrived at from the maximum legal load, 2.5g, about 66 degrees, but we don't want to apply this restriction. The question is really about power. At maximum power, what bank angle could it get to and maintain height, assuming it did not break up?

I presume it could be worked out knowing the max power, and the drag at various AoA, given that the AoA and bank angle must be related in a level turn.

Any takers?

Quote from Jane-DoH:
"Quote from Chris Scott:
"...as soon as the (control wheel) is (fully) displaced, the spoilers will rise on the downgoing wing (to 43deg)......and the spoilers on the upgoing wing will retract. In this config, maximum roll rate is about 400deg per second."
"...as soon as the (control wheel) is (fully) displaced, the spoilers will rise on the downgoing wing (to 43deg)......and the spoilers on the upgoing wing will retract. In this config, maximum roll rate is about 400deg per second."
That's on par with some aerobatic aircraft...
Why would they have configured the control-system to produce such a heavy roll rate all the sudden at maximum control surface deflection? I thought the whole idea is so that it builds up in a predictable manner..."

Apologies, Jane: I completely missed your post. Did have some later misgivings re mine, though. Obviously, once the roll-spoilers on the upgoing wing have retracted, the situation is the same as if they had been retracted (as speedbrakes) in the first place.

However, I think the point my BAC 1-11 ground instructor was making may have been relating to the initial response. Due to the moment of inertia of a 30-ton aeroplane with a fairly large wingspan, the rate of increase of roll-rate is likely to be pedestrian in relation to lighter fast jets with small wingspans, like the contemporary English Electric (BAC) Lightning that he was comparing it with.

I think you have a point, except that it wouldn't happen all of a sudden on the One-Eleven. Mind you, the 200 series I first flew certainly was agile. If you look back to my post, you'll see reference to the roll-spoilers not "cracking" until a moderate amount of aileron displacement (unlike the B707). Being airline pilots, we tried not to pass that threshold if convenient, because of the slight aerodynamic rumble from the spoilers.

Regards,
Chris

It's related to specific excess power.

But the 757 didn't have to maintain height; it was undoubtedly using its potential energy in a shallow dive, aiding the specific excess power issue.

Nonetheless, good luck with the 4.4g. :}

barit1, that is a very interesting article. Thanks.

It is clear that height and excess speed can provide power to maneuvre. Certainly the 757 had plenty of speed but very little height. The problem is it only had at the most 1 second to get its wings level from 77 degrees and pull out of the dive. It finished virtually level.

The FDR data shows it pulled up from a 5 degree descent to about 1 degree in 2 seconds and that the average force during these 2 seconds was 2g. If this absurd turn is to be believed, only 1 second would be available thus 4g lift would be required, all starting from a bank of 77 degrees. Could it do it?