Loss of Oil Pressure on PA-44

[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

 

[gkrangers]

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

They are definitely differential-frise ailerons.

-mini

Great, now I have to go play with the ailerons on a 172 next time I go to the airport....Duchess too for that matter...

 

[FL420]

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?

It depends on the vintage and the mission. Old F-9 Cougars(really dating myself here) had "flaperons." I don't really remember much about them but I think that was a fancy term for an aileron that drooped with the flaps and one froze up on me inflight once. No big deal.

The A-4 Skyhawk(aka Tinkertoy and Scooter) had conventional ailerons. An aileron hinge broke on me once. It flew fine with the aileron floating up about 30°. Speedbrake panels activated by a switch on the throttle were on each side of the fuselage behind the wing.

The F-4 Phantom II had 2 spoiler panels on each wing and ailerons. Spoilers would deploy up to 45° with stick deflection while aileron travel range was 1° up and 30° down. The ailerons drooped 16½° when flaps were lowered to ½ or full down. Turn coordination was provided by an aileron rudder interconnect(ARI.) The ARI exercised 10° of rudder authority. The yaw damper had an additional 5° of rudder authority. Speed brake panels activated by a switch on the inboard throttle were on the bottom of the wing. Spoilers located outboard on the wing provided effective roll control at higher Angles Of Attack(AOA) or alpha(α) as spanwise flow blanked airflow over the inboard trailing edge of the wing. Rudders were increasingly used for roll control when maneuvering at high AOA's as stick deflection at critical α could result in a nasty post-stall departure at a most inopportune time. The departure was aggravated by the adverse yaw introduced by the downward-deflected aileron.

The A320 family has 5 spoilers and 1 aileron on each wing. The spoilers work in various combinations for various purposes. All 10 deploy to maximum 40° deflection to dump lift(when armed by the speedbrake lever) upon touchdown. In this mode they are called "ground spoilers."

The middle 3 spoilers on each wing deploy progressively with rearward movement of the speedbrake lever. The inboard panels extend more than the outboard panels. In this mode they are called "speedbrakes."

The 4 outer panels on each wing deploy progressively with sidestick displacement to provide roll control in conjunction with aileron displacement. In this mode they are called "flight spoilers" or "roll spoilers."

The ailerons droop 5° with flap extension and have a travel range of ±25°. Turn coordination is provided by a yaw damper. A Load Alleviation Function(LAF) operates the ailerons and the 2 inboard spoiler panels at higher speeds to reduce wing structure loads during turbulence.

The spoilers and ailerons on the B757 work very similarly to the A320 family. The B757 has 6 spoiler panels(4 outboard and 2 inboard of the engine pylon) on each wing. They function in various combinations as "flight spoilers," "speedbrakes" and "ground spoilers" like the A320. Inboard spoilers are locked out at higher speeds. Turn coordination is provided by 2 yaw dampers. IIRC, the B767 has 2 ailerons on each wing with the outboard ailerons locked out at higher speeds to reduce wing bending loads .

The CRJ200 has 4 spoiler panels and one aileron on each wing. The 2 inboard panels on each wing only operate as "ground spoilers" and are either full up or full down. The outboard panels are called "spoilerons" and work in conjunction with the ailerons for roll control. BTW, the spoilerons are Fly By Wire(FBW). The spoiler panels just inboard of the spoilerons are called "flight spoilers" but they act in the air as speedbrakes and are operated progressively by the "flight spoiler control handle"(aka speedbrake handle.) They deploy fully on the ground with the 4 inboard ground spoilers as a part of the Ground Lift Dump(GLD) system. Turn coordination is provided by 2 yaw dampers.

Physical movement of ailerons and spoiler panels in modern jets is accomplished by hydraulics with valves being positioned by pushrods and bellcranks(older and heavier systems,) cables and pulleys(newer but still heavy) and electrically(newer and lighter FBW.) Two or 3 independent hydraulic systems with various combinations of engine-driven pumps, electric pumps and Power Transfer Units(PTU's) supply the power. Sometimes each aileron and spoiler panel is driven by 2 different hydraulic system(in case one fails) and sometimes each spoiler panel is only driven by one system but the adjacent panel is driven by another hydraulic system. The CRJ has 2 hydraulic systems and the F-4, A320 and B757 have three.

With yaw dampers providing turn coordination, flight spoilers providing profile drag on one wing to counteract adverse yaw generated by the aileron on the opposite wing and differential deflection of ailerons, aircraft designers don't usually need to use physical devices like Frise-type ailerons to deal with adverse yaw. Modern jet transports are pretty much flown with feet on the floor except during takeoffs and landings(crosswinds you know) and during One Engine Inoperative(OEI) situations.

I know you just asked "what time it was" and I told you how to "build a watch." Sorry, I just got on a roll. Hope I answered your questions without boring you to death.

 

[minitour]

Great, now I have to go play with the ailerons on a 172 next time I go to the airport....Duchess too for that matter...

Yep...take your plotter with the aileron neutral and lay it flat on the bottom side of the wing. Then raise the aileron...can't do it, right? Now move the plotter, raise the aileron, replace the plotter and see that it bumps into the leading edge of the aileron.

Good stuff.

-mini

 

[Amish RakeFight]

Yep...take your plotter with the aileron neutral and lay it flat on the bottom side of the wing. Then raise the aileron...can't do it, right? Now move the plotter, raise the aileron, replace the plotter and see that it bumps into the leading edge of the aileron.

Good stuff.

-mini

Interesting thing to demonstrate to a student.

 

[A Squared]

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

That's not necessarily true.

For example, banking into the operating engine just enough to cancel sideslip will increase both performance and control, when compared to wings level flight.

Feathering the prop will improve control and performance (unless you feather the prop on the operating engine, then it only improves control. Performance experineces a sudden downturn)

 

[Amish RakeFight]

That's not necessarily true.

For example, banking into the operating engine just enough to cancel sideslip will increase both performance and control, when compared to wings level flight.

Feathering the prop will improve control and performance (unless you feather the prop on the operating engine, then it only improves control. Performance experineces a sudden downturn)

Good point. Thanks for bringing it up. I was generalizing a little too much in that post.

 

[A Squared]

Good point. Thanks for bringing it up. I was generalizing a little too much in that post.

Maybe a little too general, but you're right in that it's good to teach in terms of performance and control, and think about which elements affect which in what way. I tink too often multi-engine training focuses on the control aspects and neglects the control aspects.