Tail Types

[Ashrunner]

Recently, Boeing announced a change in the F-15 Eagle -- the Silent Eagle. It is designed to be stealthier than the current models of Eagles.

Major changes are outward canted tails, rather than vertical fins, and internal weapons bays for when stealth is critical. The aircraft will still have external hardpoints when the stealth isn't critical.

More info here.

[CharlieC]

T-tails do help keep the horizontal control surfaces out of the wash from the wing at high angles of attack but it is possible to get into a "super stall" where the T-tail surfaces are blanked out. There was a fairly famous accident with the BAC-111 where the T-tail was ineffective at recovering from a stall. Most airliners with this configuration have a stick pusher to prevent the angle of attack getting too high.

Regards,

Charlie

[rmks2000]

Ashrunner

Is the change due to the reduction in F-22 purchases?

[Zathros]

We should incoporate some kind of big non stealthy device we could activate remotely in case one of these planes gets into enemy hands, like turn it into a blimp, a big orange one with a bulls eye on it.

[Ashrunner]

Originally Posted by rmks2000

Ashrunner

Is the change due to the reduction in F-22 purchases?

From what I understand, the change is for countries who won't be able to get the F-22, but still want stealth capability.

[shrike]

And an attempt by McBoeing to keep a 'paid for' production line open since they don't have another full fledged fighter contract.

A historical parallel would be Curtiss' constant attempts to revamp the P-40 into a more effective aircraft without completely redesigning it.

[Mechanic]

Originally Posted by CharlieC

I don't think anyone's commented yet that the fins on propeller driven aircraft are often offset from the centreline to partially account for the torque reaction. From memory the T-6 Texan (Harvard to colonials) would fly with nearly neutral rudder trim at cruise power settings because of this.

Regards,

Charlie

I don't recall if it was an article on full-size or r/c (probably the latter), but I remember reading something about how engine torque on propellor aircraft was more or less a myth, or false force. The true culprit was swirling prop-wash; with most of verticle stabs being above the thrust line it's the propeller airstream that tends to push the tail slightly sideways.

Comments?

[Retired_for_now]

Hmmmmnnnn ...
Thinking - - may be a while. Do know you have to step on the rudder while accellerating/climbing (takeoff); not an issue in stable flight. Could be caused by torque (let's not get into the right hand rule, 90 degrees around and perpendicular and all that), prop wash (?maybe but I'm not sure the direction is correct ...?), effect of tail/rudder tab offset that's tailored for cruise speed and not lower speed.high power climbing (how's that for a herring), other options?

Yogi

[shrike]

I'm not sure I buy the propwash explanation. It seems that would hold true only at a given rpm and prop pitch, and would be ineffective outside that narrow situation.
Interference from the wings and fuselage would tend to break up any specific flow from the prop, not to mention the effects of the horizontal surfaces which would further blank the rudder.

I've seen airplanes 'torque up' on the ground too

[Zathros]

The torque was so great on the Corsair F4U, WW2) that a stall strip was installed on the right wing to stall with the left wing it so the huge propeller would not throw the plane over. It is not a myth but the interplay within the forces may be a little understood. When an airplane is climbing the blade going down relative to forward motion has greater forward speed than the blade going down towards the retreating wind. This makes one side of the propeller cut into the wind better. This causes the plane to want to cork screw and is why much pedal force is required when taking off especially at greater angles of attack. This force becomes less prevalent when at full speed but propeller planes do not fly straight anyway, they crab a little, for various reasons, such as wind aloft and the unbalanced nature of the beast. Tail draggers that apply too much power without the appropriate rudder offset will flip right over while on the ground (ground-loop). From "Wikipedia", in reference to the F4U Corsair,

"If the throttle were suddenly advanced (for example, during an aborted landing) the port wing could stall and drop so quickly that the fighter could flip over with the rapid increase in power. These potentially lethal characteristics were later solved through the addition of a small, 6 in (152 mm)-long stall strip to the leading edge of the outer starboard wing, just inboard of the gun ports. This allowed the starboard wing to stall at the same time as the port.