Loss of Oil Pressure on PA-44

[User546]

Wouldn't it be wiser to feather the engine first, while the RPM's are >950, then shut the engine down?

So THATS why I could never get that prop to feather!

I obviously wasn't typing my thoughts in an orderly manner. The point I was trying to make was that you need to get the engine shut down, which of course entails you feathering the prop first. But you get what I meant...

 

[Kream926]

heres one that ive been pondering

i understand the gear is stabalizing, is it cause of the "keel" effect or does the gear extended move CG forward?

 

[Amish RakeFight]

heres one that ive been pondering

i understand the gear is stabalizing, is it cause of the "keel" effect or does the gear extended move CG forward?

Depending on how the gear swings, it can have an effect on Vmc. If it swings down and forward, you'll move the CG forward and increase the arm from the CG to the rudder. This may allow a slight decrease in Vmc.

Lowering the gear (or already having it down) also has a positive effect on Vmc by making it more difficult for the aircraft to yaw adversely.

 

[FL420]

Depending on how the gear swings, it can have an effect on Vmc. If it swings down and forward, you'll move the CG forward and increase the arm from the CG to the rudder. This may allow a slight decrease in Vmc.

Lowering the gear (or already having it down) also has a positive effect on Vmc by making it more difficult for the aircraft to yaw adversely.

To help clarify a little bit, lowering the gear may result in more rudder effectiveness to counteract yaw in a OEI(one engine inoperative) situation. The main landing gear on most aircraft retracts inward and extends outward without affecting the longitudinal position of the CG and therefore having negligible effect on OEI handling. However, a MLG that retracts forward or aft instead of laterally can have a significant effect on CG position.

The nose landing gear must retract either forward or aft. A forward retracting NLG will move the CG aft when the gear is extended, shortening the effective moment arm of the rudder thereby slightly reducing it's effectiveness in counteracting yaw due to OEI.

OTOH, a rearward retracting NLG will move the CG slightly forward when the NLG is extended, effectively increasing the moment arm and the effectiveness of the rudder during OEI with the gear extended.

 

[Amish RakeFight]

To help clarify a little bit, lowering the gear may result in more rudder effectiveness to counteract yaw in a OEI(one engine inoperative) situation. The main landing gear on most aircraft retracts inward and extends outward without affecting the longitudinal position of the CG and therefore having negligible effect on OEI handling. However, a MLG that retracts forward or aft instead of laterally can have a significant effect on CG position.

Actually, even though the mains have no real effect on the CG movement, they act almost like anchors on either side which makes it more difficult for any adverse yaw to take place. When the mains are extended, the operative engine in a single engine situation has a harder time yawing toward the dead engine because of the additonal drag each main gear is providing, thus lowering Vmc.

Along with a nose gear that moves forward when extended, thus moving the CG forward, both the nose and main gears serve to decrease Vmc.

 

[FL420]

Actually, even though the mains have no real effect on the CG movement, they act almost like anchors on either side which makes it more difficult for any adverse yaw to take place. When the mains are extended, the operative engine in a single engine situation has a harder time yawing toward the dead engine because of the additonal drag each main gear is providing, thus lowering Vmc.

Along with a nose gear that moves forward when extended, thus moving the CG forward, both the nose and main gears serve to decrease Vmc.

Yeah, I can see that. I don't think I would use the term adverse yaw though as that term applies to yaw resulting from induced drag as a result of lift generated by a down-going aileron.

In a non-centerline thrust multi-engine nose-dragger, the CG is forward of the MLG and yaw is going to result in drag on the MLG resulting in a large force vector opposite the line-of-flight and a much smaller force vector in the direction of the displaced nose tending to realign the nose with the line-of-flight(i.e.-stabilizing.)

In a non-centerline thrust multi-engine tail-dragger, the CG is aft of the MLG and yaw is going to result in drag on the MLG resulting in the same force vectors as above but since the force is acting forward of the CG it tends to further displace the nose from the line-of-flight(i.e.-destabilizing.)

This article actually concerns ground operations but provides good background.

http://www.aerospaceweb.org/question/design/q0200.shtml

This one discusses aerodynamic forces in flight.

http://www.aerospaceweb.org/question/dynamics/q0045.shtml

 

[Amish RakeFight]

Yeah, I can see that. I don't think I would use the term adverse yaw though as that term applies to yaw resulting from induced drag as a result of lift generated by a down-going aileron.

Yeah, I realized I used this term in a more generic sense. I meant it as unwanted yaw which is developed from an imbalance in engine power. I hope no one confuses it with "adverse yaw" as it applies technically to the drag induced by the UP not "down-going" aileron.

 

[FL420]

I don't think so..........

I hope no one confuses it with "adverse yaw" as it applies technically to the drag induced by the UP not "down-going" aileron.

Thus, the wing on which the aileron is deflected downward to generate more lift also experiences more induced drag than the other wing. Profile drag includes all other forms of drag generated by the wing, primarliy skin friction and pressure drag. This profile drag increases on both wings when the ailerons are deflected, but the increase is equal when the ailerons are deflected by the same amount. However, the induced drag on each side is not equal, and a larger total drag force exists on the wing with the down aileron. This difference in drag creates a yawing motion in the opposite direction of the roll. Since the yaw motion partially counteracts the desired roll motion, we call this effect adverse yaw.

http://www.aerospaceweb.org/question/dynamics/q0045.shtml

 

[Amish RakeFight]

Thus, the wing on which the aileron is deflected downward to generate more lift also experiences more induced drag than the other wing. Profile drag includes all other forms of drag generated by the wing, primarliy skin friction and pressure drag. This profile drag increases on both wings when the ailerons are deflected, but the increase is equal when the ailerons are deflected by the same amount. However, the induced drag on each side is not equal, and a larger total drag force exists on the wing with the down aileron. This difference in drag creates a yawing motion in the opposite direction of the roll. Since the yaw motion partially counteracts the desired roll motion, we call this effect adverse yaw.

http://www.aerospaceweb.org/question/dynamics/q0045.shtml

You're right.
Sorry for any confusion.

I think I might be dyslexic!:blush:

 

[buxflyr]

Thus, the wing on which the aileron is deflected downward to generate more lift also experiences more induced drag than the other wing. Profile drag includes all other forms of drag generated by the wing, primarliy skin friction and pressure drag. This profile drag increases on both wings when the ailerons are deflected, but the increase is equal when the ailerons are deflected by the same amount. However, the induced drag on each side is not equal, and a larger total drag force exists on the wing with the down aileron. This difference in drag creates a yawing motion in the opposite direction of the roll. Since the yaw motion partially counteracts the desired roll motion, we call this effect adverse yaw.

http://www.aerospaceweb.org/question/dynamics/q0045.shtml

Now you can start talking about the "Frise" ailerons and how they are used to counteract the adverse yaw. This is the upward facing aileron...

Also, I would think that any positive effect that lowering the gear would have on Vmc would be offset by the large amount of drag that gear is creating.