Asymmetric wing incidence angles

[gaussianum]

gaussianum,
Sorry dude!!! This article is very bad news, in my opinion (but FlyboyJ seems to like it, so maybe I should reconsider).

It's Ok, but I really think you should read the full article. Maybe you're misinterpreting the author, and I suspect, to a significant degree.

He is trying, for some reason to say that the engine prop are always at a 90 degree angle to the direction of flight, and therefore can only produce a rolling effect.

No aircraft would fly in such a situation. Only a helicopter would. I think you're misinterpreting.

What is happening to the aircraft is similar to your experience, if you were holding a spinning bicycle wheel by the ends of the axel, as you change rotation, by swiveling (yawing) the axel, from horizontal to vertical, what is happening to our pilot is the view from near center of the axel.

What you are referring to, is gyroscopic motion. Climbing in an aircraft can produce a gyroscopic yawing motion, not a rolling one. Rolling will increase After the craft has started yawing, due to asymmetric wing lift, caused by the yaw itself.

My question has a physical origin. According to Newton's law of Action-Reaction, the torque imparted to the propeller is the opposite to the torque imparted to the airframe by the propeller/shaft. Since the prop rotates (Fast!), there is always a torque acting on the airframe, to make it rotate in the opposite direction. This is not an effect. This is the cause of all torque induced behaviour.

My question is: what force counters it?

Having the ailerons turned a bit to the right, when the controls are neutral (thus making the left wing generate slightly more lift than the right one), would counter it, but only when the airspeed reaches a certain level, namely cruise speed. This is because wing lift increases with V^2, so a small margin when speed is small, becomes a very large one when speed increases.

Another possibility would be, as the author says, to increase the left wing's incidence angle, relative to the right one.

P-factor only becomes significant when airspeed increases. Stockhouse says that the propwash force is stronger than p-factor at take-off, and although I would like to see the governing equations, I suspect that he is right.

I emphasize that the issue here is how rolling motion is countered, not yawing one.

When you stall, you roll. This means that the tail alone is not enough to counter engine torque. The propwash force is present, wether the aircraft is flying at 0 or 300 Km/h (as long as the engine is on, and the props are rotating, of course).

FlyboyJ, when flying at high speed, does an aircraft have a slight tendency to roll to the right?

Best Regards

 

[FLYBOYJ]

My question has a physical origin. According to Newton's law of Action-Reaction, the torque imparted to the propeller is the opposite to the torque imparted to the airframe by the propeller/shaft. Since the prop rotates (Fast!), there is always a torque acting on the airframe, to make it rotate in the opposite direction. This is not an effect. This is the cause of all torque induced behaviour.

My question is: what force counters it?

Look at the size and mass of the spinning propeller, then look at what's behind this - a much larger mass - the airframe with surfaces generating lift.

Having the ailerons turned a bit to the right, when the controls are neutral (thus making the left wing generate slightly more lift than the right one), would counter it, but only when the airspeed reaches a certain level, namely cruise speed. This is because wing lift increases with V^2, so a small margin when speed is small, becomes a very large one when speed increases.

Another possibility would be, as the author says, to increase the left wing's incidence angle, relative to the right one.

P-factor only becomes significant when airspeed increases. Stockhouse says that the propwash force is stronger than p-factor at take-off, and although I would like to see the governing equations, I suspect that he is right.

I emphasize that the issue here is how rolling motion is countered, not yawing one.
When you stall, you roll. This means that the tail alone is not enough to counter engine torque. The propwash force is present, wether the aircraft is flying at 0 or 300 Km/h (as long as the engine is on, and the props are rotating, of course).

You'll roll in a "Power On" stall, and that's why you need right rudder to counteract that and attain "Directional Stability." If you stall the aircraft with the engine at idle, most aircraft break out of the stall straight ahead.

Gauss - you've answered many of your own questions, all are correct!

FlyboyJ, when flying at high speed, does an aircraft have a slight tendency to roll to the right? Best Regards

You mean left (as sitting in the cockpit). It depends on the aircraft. Let me tell a story...

I worked on the P-3 for a number of years, in the early 1980s I worked on the production line. Our subcontractor dropped a right wing, it was rebuilt and shipped to our factory. When the aircraft was completed we did an asymmetry check and discovered the wing was slightly crooked (I don't remember the exact details). Lockheed management decided to do some additional testing prior to asking the customer (the USN) to take delivery of it. All parties agreed. Now the P-3 has 4 T56 engines all rotating in the same direction. I was told by the pilots at full speed the P-3 could not be trimmed out, it slightly turned left. This aircraft (with the repaired wing) was flown and at about 470 mph (the P-3s top speed) this aircraft flew straight and level "hands off." Till today I remember one the the flight test engineers saying "we couldn't build aircraft that could do that again if we tried....

 

[JonJGoldberg]

Flyboy J, gaussianum you must check out these finds, one I stumbled across hours ago, the other I don't remember how I found it but they are relevant.

The first http://naca.larc.nasa.gov/digidoc/report/tm/12/NACA-TM-712.PDF, an article from the NACA database (NASA archives), authored in 1933, is a 'technical' review of the Schneider Trophy aircraft.

The other NASA/TM-2004-212045 is titled Manual Manipulation of Engine Throttles for Emergency Flight Control. Shoot, I don't have the E-mail address, and it is a NASA document, I'll await a response from a 'mediator' or other WW2aircraft.net official to tell me weather or not I may attach this .pdf for you to upload, But I will attach some pages, so they may tell me if it is OK.

 

[gaussianum]

In the first report, they use two solutions.

First one: counter-rotating engines. The torque of one engine cancels the torque of the other.

Second one: They increase the weight of the right float. This increases the Moment of Inertia of the plane; it shifts the Center of Gravity to the right also, which is not the best of solutions, but it was probably the best one they could find.

In the second report:

All of these seem to be multi-engined aircraft. Some of them seem to be jet-engined.

The asymmetric wing incidence question is mostly related to single-engined, piston-driven (propeller) aircraft.

Best Regards

 

[FLYBOYJ]

Flyboy J, gaussianum you must check out these finds, one I stumbled across hours ago, the other I don't remember how I found it but they are relevant.

The first http://naca.larc.nasa.gov/digidoc/report/tm/12/NACA-TM-712.PDF, an article from the NACA database (NASA archives), authored in 1933, is a 'technical' review of the Schneider Trophy aircraft.

The other NASA/TM-2004-212045 is titled Manual Manipulation of Engine Throttles for Emergency Flight Control. Shoot, I don't have the E-mail address, and it is a NASA document, I'll await a response from a 'mediator' or other WW2aircraft.net official to tell me weather or not I may attach this .pdf for you to upload, But I will attach some pages, so they may tell me if it is OK.

I posted that NASA report on another link here in this forum in its entirety - I got it from my Father in law, he wrote an emergency procedure for UA on the 737 based on this information. Here's a copy, let me know if it downloads...

 

[JonJGoldberg]

Flyboy J...son of a gun, you did post NASA/TM-2004-212045, thanks again. I was not trying at all to take credit, I wanted to share, hope I didn't do something I was not supposed to, or that you took offence too. …Must have been an early senior moment. I suck!!!

gaussianum… They did much more than weight a float; from the article "…The 1923 Curtiss racers therefore used a weight balance in the float." "…Subsequent developments revealed the inadequacy of tilis weight balance for larger engines and the same dimensions. As a result, the more modern racer has a flotation gear in which the float loaded additionally at the takeoff is farther away from the plane of symmetry and, in addition, larger than the unloaded float (resistance balance). But even these measures did not always prove sufficient on all racing seaplanes. Thus the propellers of the Supermarine S.6 B had to have a diameter greater than the optimum figure, because at take-off with smaller propellers, it was impossible to keep the seaplane on the course, thus making the take-off altogether impossible."

So it seems to me they played with lots of stuff. I thought this may be of use to you …an attempt. Since I'm self educated, I just love going off into the deep end... My solutions...

 

[FLYBOYJ]

Flyboy J...son of a gun, you did post NASA/TM-2004-212045, thanks again. I was not trying at all to take credit, I wanted to share, hope I didn't do something I was not supposed to, or that you took offence too. …Must have been an early senior moment. I suck!!!

Hey No problem - that report is a bit dry but interesting. I actally had the opportunity to fly a 737 full motion simulator at UAs training center on severl occasions. On a "10 mile final from DIA" my rudder was "locked" and hydraulics were failed. My brother in law was in the right seat, he's a big strong guy so with his muscle (and mine) along with differential throttles, we landed the aircraft, the only damage that occured was the collision with several landing lights as we rolled off the end of the runway at about 20 knots due to the rudder being in full deflection.....

 

[gaussianum]

Hi JonJGoldberg,

Congrats for that very nice sketch, I appreciate your work.

Some further thoughts on the measures taken by engineers to reduce engine torque:

-Extending the float away from the axis of symmetry, again increases the Moment of Inertia, and unbalances the aircraft to the right. This has the effect that the torque induced by the left wing is greater than the one generated by the right one, at all speeds, since the lef wing's Center of Gravity is farther away from the plane's Center of Gravity, than the right one's.( nicely convoluted sentence there)

- Making the right float bigger enhances its buyoyancy properties, and the air resistance induces slight yawing torque, that counteracts the usual propeller-caused yaw.

- Making the propeller blades bigger probably increases the volume of the slipstream air column (propwash) hitting the horizontal and vertical stabilizers, thus countering more effectively the aircraft's rolling and yawing tendencies.

Did any of those Schneider Trophy planes have small winglets?

Best Regards

 

[JonJGoldberg]

gaussianum... Thank You.

I reasoned these innovations; I've never seen on a 'Schneider Trophy' aircraft, or any other aircraft, applied as I've shown (in yellow), an asymmetrical retractable rudder, asymmetrical winglet, asymmetrical elevator rudder leading edge slats. I also tilted the camber a bit on the larger float, but I reason someone has done that.

As I've shown, I believe the most effective controls would not be fixed, nor would it be an asymmetrical horizontal mounting of an elevator, or wing. For all the complexities I've shown, I believe that the 'real' aircraft designers were yet even cleverer. For example, as with the P-47, make the trim adjustments available only one side of the wing; then 'autopilot'...

Let me share this site with you The FoilSim II Applet. I've used it to help me visualize, and since it is from NASA, do rough math. It should help all here, Flyboy J you will love this, I should have remembered this site sooner!!! As a bonus, there is lots of other NASA Sim stuff as well!!!

http://www.grc.nasa.gov/WWW/K-12/freesoftware_page.htm

 

[FLYBOYJ]

Cool site JJ - lots of neat stuff!

 

[JonJGoldberg]

I still can not find that American test aircraft, I can't even remember it's number, the aircraft with the pivoting wing... Anyway found one better. Bad thing about this is, the design was applied as a solution for handling at various speeds, not asymmetrical forces .

 

[gaussianum]

That's very interesting JonJ. I've never seen anything like it.

 

[JonJGoldberg]

I found it... Matter of time... OK see what I created and posted below... Now check this out; this NASA researcher claims to have 'conceived' the idea. ... That is why I thought the BV such a find!!!

Go here for a 'quick-time' movie ( http://www.dfrc.nasa.gov/Gallery/Movie/AD-1/HTML/EM-0001-02.html )

This is where I found the pics from there the info... Have fun!!!
( http://www.dfrc.nasa.gov/Gallery/Photo/index.html )

FlyboyJ... Did I find the rock that does not ascribe to the bank angle law? No... But I wonder if this aircraft's bank angle is the same as that of a conventional aircraft of the same span... regardless of it's setting? That is why you see a pic of the cockpit.

 

[FLYBOYJ]

Hmmm, no turn and bank or artificial horizon on the instrument panel?!?

 

[ErangaEddie]

Can anyone tell me the disadvantage of an asymmetrical wing? please.

 

[pbehn]

Yes, I think that's the key to the problem. It's probably the stabilizer, not the wings.

You're a pilot aren't you? From your experience as a pilot, or from footage you may have seen, what would happen if a fellow lost his vertical stabilizer? The aircraft would not only yaw, but also roll, wouldn't it?

This happened to a 747 in 1985
Japan Airlines Flight 123 - Ask.com Encyclopedia

 

[Elmas]

To counterbalance the torque the Macchi 200-202-205 had wing dimensions slightly different berween left and right wing. The right wing was 4.32 m long, with a chord of 1.17 m at the tip and a weight of 168 kg, while the left measured 4,52 m, with 1.16 m at the tip, with a weight of 185 kg.

 

[GregP]

I believe the Bf 109 had asymmetry in the vertical fin. It was airfoiled on one side to help counter torque on takeoff and pretty much flat on the other side. Another method for helping to counter torque is engine mount offset. Many aircraft have a degree or two of downward / left / right thrudt from the engine mount.

Washout actually subtracts a small amount of total lift from the wing, but the benefits return at the stall when the ailerons remain efective as the wing root stalls. Wash-in is backwards, and is not generally desirable.

Usually the wing incidence is quoted as the incidence at the wing root - fuselage joining, not as an average of the entire wing. A great example of wing incidence would be the Bopeing B-52. The wing has a large positive incidence and is so great taht the tail lifts off firsta nd it flies nose down in level flight at low altitude. At it design bombing altitude, it flies levelly.

 

[waroff]

on the aicraft single engine or multi(but the propellers turn in same direction)
there are some effects:
- torque, due to drag of blade propeller
- helical wind of propeller
- asymetrical airscrew thrust
- gyroscopic effect

to compensate for these effects :
- torque: aileron trim, lenght of the wings(Macchi), adjustable flap on wingtip(MS406, MB152)

- helical wind: setting of fin(H75, Hawker Hurri, Bf 110, F4Au, Mureaux 11x...) or asymetrical air foil(D520...) + engine setting 1° left and 1°down(D520), 1°26' left and 1° down(MS406), 3° left(MB152)

- asymetrical thrust and gyroscopic effect are when airplane climb and/or change of pitch attitude : trim rudder