Buffalo Control Response: Better than the Spitfire?

[Skyediamonds]

Good afternoon everyone. I just read in HistoryNet that the Brewster Buffalo was one of the first fighters that featured sheet metal ailerons as opposed to the fabric covered ones of the Spitfire & Hurricane. It went on further to say that the Finns were greatly impressed with its "…crisp rolls in which the ailerons were not as sloppy as on the Hurricane. Light on elevator controls & not as sensitive as opposed to the Spitfire…."

I'd like to know how sheet metal covered ailerons & elevators would yield better responses on flight controls, if all other factors (airspeed, altitude, size & airfoil shapes, etc) bring equal.

 

[pbehn]

Comment on another forum by Edgar Brooks late of this parish RIP. A lot of info on the subject in the link Metal ailerons,,

Two sets were made up and tested, and the behaviour wasn't liked; Camm seems to have been disinterested, and Farnborough didn't want to spend any time making them acceptable, so the whole idea was quietly dropped, with the Typhoon taking precedence.

 

[buffnut453]

I suspect some of the benefits seen in the Buffalo came from the use of metal control rods that were fixed to the base of the control column. Those rigid rods resulted in shorter cable runs and hence less stretch of cables when manoeuvring under load. It's just a theory, mind you.

 

[pbehn]

The Spitfire elevators were improved by Westlands W.E.W. Petter but not with metal surfaces.

By 1942 Westland was building mostly Spitfires under contract.[30]​ One of the problems with the early marks of Spitfire was variability of longitudinal stability, leading to aircraft getting dangerously out of control and contributing to the risk of structural failure .[31]​ Petter made a significant contribution to improving the longitudinal stability of the Spitfire because he was the first to appreciate that aerodynamic modification to the elevator could provide additional stability. On his own initiative he had Penrose collect flight test stick force data and trim curves on a Spitfire at various centre of gravity loadings, then produced a prototype elevator with a bulged aerodynamic section, which produced a 'remarkable' improvement in stability, later being known as the 'Westland Elevator'.[32]​

 

[SplitRz]

I've been reading some of Winkle Browns assessments of various aircraft. Nothing he says undermines the idea that the handling of the Buffalo was actually very good, whatever else its other shortcomings. That may well have been due in part to its use of metal :

""In normal cruise at 160 mph the aircraft was longitudinally unstable, laterally neutral stable, and directionally positively stable. Maximum speed was 290 mph at 16,500 ft. and the service ceiling was only 25,000 ft. Not very impressive performance. However, it was a different story when it came to handling, for the ailerons were highly effective throughout the speed range, the elevators almost equally so, and the rudder very good too."

"My feeling after flying the Buffalo was one of elation tinged with disappointment. It was a true anomaly of an aeroplane with delightful manoeuvrability but poor fighter performance."

 

[pbehn]

Why do you single out the Spitfire? The challenge is delivering fighter performance with good control, so its quite possible something like a Harvard trainer is better than a fighter. The best fighters are on the edge of stability, it means they change direction more quickly.

 

[GregP]

Why do you single out the Spitfire? The challenge is delivering fighter performance with good control, so its quite possible something like a Harvard trainer is better than a fighter. The best fighters are on the edge of stability, it means they change direction more quickly.

The "perfect" fighter would have dead neutral stability on all 3 axes ... it would also not be fun to fly it on instruments, but it would be very responsive to pilot inputs.

 

[pbehn]

The "perfect" fighter would have dead neutral stability on all 3 axes ... it would also not be fun to fly it on instruments, but it would be very responsive to pilot inputs.

Like any high performance car or motorcycle, great to drive or ride but you cant spend any time gawping at the countryside.

 

[PAT303]

Why do you single out the Spitfire? The challenge is delivering fighter performance with good control, so its quite possible something like a Harvard trainer is better than a fighter. The best fighters are on the edge of stability, it means they change direction more quickly.

In 1940 production over road development, metal elevators weren't the issue with the Spitfire, it was the profile. Like all fighters it wasn't until they were pushed to their limits in an actual war that problems presented themselves, the fabric elevators ballooned at high dive speeds and the initial metal elevators gave no improvement, it wasn't until the profile was changed that there was a marked improvement in their performance.

 

[Shortround6]

They also installed a bob weight in the elevator circuit to help limit some of the over control. The elevators were too powerful. (too much response for a given amount of travel or effort)

The Hawk 75 was noted as having well coordinated controls.

If the fighters controls give markedly different response (different amount of change in direction/rotation) for the same level of input the plane is going to be difficult to maneuver well.

However, the amount of response for a given amount of input (force and/or distance on the stick/pedals) changes with the speed and the change is not usually the same for the different controls.

Also note that a slow fighter has an easier time of this, since the force acting on the control surface (or force needed to move the control surface) goes up with the square of the speed.

The force needed to move a control surface a given distance at 250mph is about 1/2 the force needed to move the control surface at 350mph. However the same amount of movement of the control surface is going to give a different result (change in angle/direction) at the two different speeds.

This not the same as trim. ( I don't think, I am not a pilot) Trim is adjusting the force needed as the speed changes so that plane responds the same way both ways, as in rudder makes the plane yaw the same amount both ways with the same amount of rudder deflection. This will change at different speeds. Or the elevator needs trim to make the elevator respond correctly at different speeds. Since the horizontal stabilizer exerts negative lift in proportion to the square of the speed the trim is there to try to keep the force needed on the elevator to within the desired range. If the fabric on the elevators balloons it can limit the ability of the of the elevators to affect the air flow and thus the control of the plane.

But it is all a balancing act. The planes that are "pilots" planes have the least change in the control inputs for a given result over the common speed range.

 

[PAT303]

Also note that a slow fighter has an easier time of this, since the force acting on the control surface (or force needed to move the control surface) goes up with the square of the speed.

Good point, what people forget is the Me109 had the very same issue, Spitfires and 109's tangled as high as 30,000 feet and above during the BoB, ran the engines at over boast, dived at speeds well above peacetime velocities and turned as hard as physically possible, it's no surprise the pilots of both experienced handling issues that lesser aircraft never suffered from.

 

[BiffF15]

This not the same as trim. ( I don't think, I am not a pilot) Trim is adjusting the force needed as the speed changes so that plane responds the same way both ways, as in rudder makes the plane yaw the same amount both ways with the same amount of rudder deflection. This will change at different speeds. Or the elevator needs trim to make the elevator respond correctly at different speeds. Since the horizontal stabilizer exerts negative lift in proportion to the square of the speed the trim is there to try to keep the force needed on the elevator to within the desired range. If the fabric on the elevators balloons it can limit the ability of the of the elevators to affect the air flow and thus the control of the plane.

But it is all a balancing act. The planes that are "pilots" planes have the least change in the control inputs for a given result over the common speed range.

Shortround6,

Per an aviation website: Aircraft trim holds control surfaces (rudder, elevator, or ailerons) in a specific position, requiring less manual input from the pilot to maintain a desired flight attitude. Trim either moves entire control surfaces (like on a stabilator) or is installed as a separate trim tab (like on an elevator).

Trim is used to relieve pressure on the flight controls. For takeoff in the F15 we would put the trim in the "green" (little pushbutton that would reset the flight controls in pitch to the takeoff position). The takeoff position allowed the aircraft to have a slight pitch up at normal weights at takeoff speed. As the plane accelerates and without trimming the stick you would have to push forward at greater amounts as speed increased just to maintain level flight or a shallow climb. At pilot training we were hammered initially with "trim trim trim" so as to make it easier to fly the plane (a trimmed up plane requires less brain cells to fly). A aircraft will be trimmed for a speed. At 250kts and level, unacclerated flight, and trimmed up, the plane will pretty much hold altitude. Push the power up and it will climb pretty much at 250kts. Pull the power and it will descend at 250. You trim for airspeed and power for altitude.

As for the rudder, it's just like the elevator on cable or pushrod flight controls in that the faster you go, the more force you will need to put on it to get the plane to move. It will move more for a given amount the faster you go (greater force acting up the surface, less movement gives more reaction).

Now to totally distort what I wrote here is what the Thunderbirds and Blue Angels do. When flying a trimmed up plane there is a little dead spot (hydraulic flight controls) as in you can move the stick just a tiny bit and nothing much happens. When watching a two ship of jets in formation flying into the pattern you would think they were glued together. However, if you were the wingman you would be bobbing around just a little and making constant power and flight control inputs in order to stay in position. That little bobbing is almost eliminated in our two demonstration teams by flying with full nose down trim while doing the show. Yep, crazy sounding shit but they do it. The F16 will slowly pull the trim back to 1g, while the F18 does it rather quickly. End result, the T-Birds are constantly trimming nose down (about 45lbs of force pull back required to hold it level) and the Blues use a bungee cord attached to the center pedestal that is put on the stick to pull it forward. In full disclosure I haven't seen the Blues set up, but have spoke with enough T-Bird guys who relayed that to take it as truth. The F16 stick literally only moves about 1/8 inch in any direction. I have tried doing this and absolutely hated it in pitch, but in roll I would put a couple of clicks on aileron into my flight lead when flying close as it helps "hold" you in position.

A car analogy would be driving at 20 mph your car pulls to the left. At 30 it tracks straight, and at 40 it pulls to the right. It's "trimmed" for 30 mph. Trim allows you to reset the speed at which it tracks straight.

If someone can explain it better feel free to chime in as I never instructed at the primary level.

Cheers,
Biff

 

[Shortround6]

Thank you.

Once you get into power assisted controls and computer controlled controls (fly by wire) I get lost quickly.

For the WW II pilots who had to use muscle power to deflect the control surfaces the degree of leverage in the control circuit was often important. Again, too much or too little and over which speeds.

 

[GregP]

Shortround6,

Per an aviation website: Aircraft trim holds control surfaces (rudder, elevator, or ailerons) in a specific position, requiring less manual input from the pilot to maintain a desired flight attitude. Trim either moves entire control surfaces (like on a stabilator) or is installed as a separate trim tab (like on an elevator).

Trim is used to relieve pressure on the flight controls. For takeoff in the F15 we would put the trim in the "green" (little pushbutton that would reset the flight controls in pitch to the takeoff position). The takeoff position allowed the aircraft to have a slight pitch up at normal weights at takeoff speed. As the plane accelerates and without trimming the stick you would have to push forward at greater amounts as speed increased just to maintain level flight or a shallow climb. At pilot training we were hammered initially with "trim trim trim" so as to make it easier to fly the plane (a trimmed up plane requires less brain cells to fly). A aircraft will be trimmed for a speed. At 250kts and level, unacclerated flight, and trimmed up, the plane will pretty much hold altitude. Push the power up and it will climb pretty much at 250kts. Pull the power and it will descend at 250. You trim for airspeed and power for altitude.

As for the rudder, it's just like the elevator on cable or pushrod flight controls in that the faster you go, the more force you will need to put on it to get the plane to move. It will move more for a given amount the faster you go (greater force acting up the surface, less movement gives more reaction).

Now to totally distort what I wrote here is what the Thunderbirds and Blue Angels do. When flying a trimmed up plane there is a little dead spot (hydraulic flight controls) as in you can move the stick just a tiny bit and nothing much happens. When watching a two ship of jets in formation flying into the pattern you would think they were glued together. However, if you were the wingman you would be bobbing around just a little and making constant power and flight control inputs in order to stay in position. That little bobbing is almost eliminated in our two demonstration teams by flying with full nose down trim while doing the show. Yep, crazy sounding shit but they do it. The F16 will slowly pull the trim back to 1g, while the F18 does it rather quickly. End result, the T-Birds are constantly trimming nose down (about 45lbs of force pull back required to hold it level) and the Blues use a bungee cord attached to the center pedestal that is put on the stick to pull it forward. In full disclosure I haven't seen the Blues set up, but have spoke with enough T-Bird guys who relayed that to take it as truth. The F16 stick literally only moves about 1/8 inch in any direction. I have tried doing this and absolutely hated it in pitch, but in roll I would put a couple of clicks on aileron into my flight lead when flying close as it helps "hold" you in position.

A car analogy would be driving at 20 mph your car pulls to the left. At 30 it tracks straight, and at 40 it pulls to the right. It's "trimmed" for 30 mph. Trim allows you to reset the speed at which it tracks straight.

If someone can explain it better feel free to chime in as I never instructed at the primary level.

Cheers,
Biff

I've always remembered my aerodynamics professor's explanation of trim. He said:

"You fly the aircraft straight and level, and use the trim to remove any force you have to use to stay straight and level. When you have it trimmed to fly hands off straight and level, then the aircraft in in trim for that speed, weight, angle of attack, power, and CG. When any of those change, you have to re-trim to remove the force on the stick and rudder to remain in straight and level flight.

If you are trimmed, then if you add power, the aircraft will climb straight ahead at the trim speed if you hold more rudder to remain straight against the new higher torque.

If you are trimmed, then if you subtract power, the aircraft will descend straight ahead at the trim speed if you hold less rudder to remain straight against the new lesser torque."

He claimed trim was there simply to remove the force from the stick and rudder in any flying situation.

 

[PAT303]

Greg/Biff all that makes sense to me.

 

[Snautzer01]

 

[Snautzer01]

never instructed at the primary level.

Let me help you with that.

Just ask the simple question first:

 

[pbehn]

Let me help you with that.

Just ask the simple question first:

View attachment 692740

Why is the blue whale turning left?

 

[FLYBOYJ]

I never instructed at the primary level.

Cheers,
Biff

You'll never know the crazy fun you missed!

 

[Shortround6]

You'll never know the crazy fun you missed!


View attachment 692747

Haven't even gotten off the ground yet???