Loss of Oil Pressure on PA-44

[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.

 

[FL420]

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...

I have flown airplanes with normally-hinged ailerons; airplanes with ailerons that travel further when up than when down; airplanes with spoilers only; airplanes with spoilers that go up on one wing while the aileron on the opposite wing only goes down, not up; airplanes with inboard and outboard ailerons where the outboard ailerons are locked out at high speeds and airplanes with Aileron Rudder Interconnect(ARI.) I can't recall ever seeing an aircraft with top-hinged Frise-type ailerons where profile drag on the bottom of the aileron is used to counteract adverse yaw due to induced drag on the opposite aileron. I'm sure they exist, though.

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.

Yeah, but you gotta land sometime so it helps to know what lowering the gear is going to do to aircraft handling qualities.

 

[Amish RakeFight]

Multiengine Vmc (what affects it) is a compromise between performance and control. What helps performance hurts control and vice versa.

 

[minitour]

I have flown airplanes with normally-hinged ailerons; airplanes with ailerons that travel further when up than when down; airplanes with spoilers only; airplanes with spoilers that go up on one wing while the aileron on the opposite wing only goes down, not up; airplanes with inboard and outboard ailerons where the outboard ailerons are locked out at high speeds and airplanes with Aileron Rudder Interconnect(ARI.) I can't recall ever seeing an aircraft with top-hinged Frise-type ailerons where profile drag on the bottom of the aileron is used to counteract adverse yaw due to induced drag on the opposite aileron. I'm sure they exist, though.

You've never flown a 172? 152?

 

[FL420]

You've never flown a 172? 152?

Uh, yeah. The Cessna singles I've flown are the C150/152/172/172RG/177RG/182/195 and 210, but granted, all a long time ago. I'm starting to work on getting the civilian CFI/CFII/MEI ratings so will have the opportunity to check out the C172 and PA44 ailerons soon.

I did some digging and all I could come up with is all the so-called aviation experts(i.e.-denizens of forums like this and other places) cannot agree on which Cessna singles have Frise-type ailerons and which don't. They especially can't agree on the C152 and C172.

Looking at a picture of the C172 aileron hinge makes me think you could possibly stretch the definition of a Frise aileron to include the little piano hinge mounted at the top of the front rib. It doesn't appear that any part of the aileron sticks down into the airflow to create profile drag although I suppose the gap created when the aileron pivots up could create some interference drag.

I'm always happy to learn something new.

 

[buxflyr]

I have flown airplanes with normally-hinged ailerons; airplanes with ailerons that travel further when up than when down; airplanes with spoilers only; airplanes with spoilers that go up on one wing while the aileron on the opposite wing only goes down, not up; airplanes with inboard and outboard ailerons where the outboard ailerons are locked out at high speeds and airplanes with Aileron Rudder Interconnect(ARI.) I can't recall ever seeing an aircraft with top-hinged Frise-type ailerons where profile drag on the bottom of the aileron is used to counteract adverse yaw due to induced drag on the opposite aileron. I'm sure they exist, though.


Look at this article again.

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

About half way down is the picture showing the Frise Ailerons. Without knowing how to draw on here, its the best way to see the effect. The air does flow through the small slot as well, but from how it was explained to me, the front part of the aileron is doing most of the work by creating more profile drag, and thus counter-acting the yaw.

By the way...how did you get to fly all of those airplanes you list? Know alot of people?

 

[minitour]

Uh, yeah.

I was just checking.

The 152s and 172s I've flown have an extra "piece" that is extended from the leading edge of the aileron. When the aileron is down, this piece is tucked in the gap, when the aileron is deflected up, the piece hangs out in the airstream.

Very little, but it's there.

-mini

 

[FL420]

Look at this article again.

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

About half way down is the picture showing the Frise Ailerons. Without knowing how to draw on here, its the best way to see the effect. The air does flow through the small slot as well, but from how it was explained to me, the front part of the aileron is doing most of the work by creating more profile drag, and thus counter-acting the yaw.

Here is a photo of an aileron on a C172:

http://www.weekendcfii.com/photos/c172preflt/C172_aileron_hinge.jpg

IIRC, the bottom of the aileron is flush with the bottom of the trailing edge of the wing when neutral. I don't think any part of the aileron lowers into the free airstream when the aileron is up. It does create quite a gap between the bottom of the wing and the bottom of the aileron when up. The illustrations of a Frise aileron in the article cited above definitely show the bottom of the leading edge of the aileron sticking down below the wing. That's not happening here.

 

[FL420]

By the way...how did you get to fly all of those airplanes you list? Know alot of people?

My dad and his twin brother were longtime pilots and aircraft mechanics. My first ride in an airplane was at age 2 in a Waco UPF-7. Unfortunately, I don't remember it.

Dad owned a Fairchild 24C and a Stinson 108. I inherited the Stinson and owned a Globe Swift for many years. Hanging out at airports and being older than dirt accounts for all the rest.

 

[buxflyr]

Here is a photo of an aileron on a C172:

http://www.weekendcfii.com/photos/c172preflt/C172_aileron_hinge.jpg

IIRC, the bottom of the aileron is flush with the bottom of the trailing edge of the wing when neutral. I don't think any part of the aileron lowers into the free airstream when the aileron is up. It does create quite a gap between the bottom of the wing and the bottom of the aileron when up. The illustrations of a Frise aileron in the article cited above definitely show the bottom of the leading edge of the aileron sticking down below the wing. That's not happening here.

Yea, and the thing is... it doesnt seem to make that huge of a difference on the pa-44 either....but its there, and the reason I started this whole thread was because the ailerons, (i had to draw it out) along with the oil pressure question was on my multi oral. The responses have been great though... learned even more now!

I have not gotten to this point yet, but what do most jets use? Any certain type besides a combo of outboard/inboard, etc? What about heavy's vs. rj's?

 

[minitour]

I don't think any part of the aileron lowers into the free airstream when the aileron is up.

It does...not nearly to the extent of the pictures in the article, but it does.

They are definitely differential-frise ailerons.

-mini