Yaw is no Yawning Matter

[Pearo]

From NASA Report CR-1975, Riding and Handling Qualities of Light Aircraft:"The change in rolling moment due to variation in yawing velocity ... wing provides the major contribution ... left wing moves faster than the right wing, producing more lift ... consequently ... rolling moment ..."

whereas

 

"the change in rolling moment .. caused by variation in sideslip angle ... is the result of wing dihedral effect and the moment resulting from the vertical tail center of pressure located above the equilibrium x-axis ..."

 

Apply rudder and you get both a yawing velocity and a sideslip (or skid).

 

The report quantifies each effect for a Cessna 182 as an example.

Link pls.

 

 

[djpacro]

Link to my hard drive? Try the NASA Technical Report server or Cranfield University library - both free.

 

 

[Pearo]

Link to my hard drive? Try the NASA Technical Report server or Cranfield University library - both free.

Neither seem to provide the paper you cited, or at least its not obvious from the searches I performed.

 

Perhaps you could drop box it for those of us who are not privy to the report

 

 

[Pearo]

Ok, so it seems said report is actually a book. I found a digitised copy online, that is pretty hard to read. a PDF would be better.

 

Trying to see the link to a Cessna 182 data. To me all I can see now is a table that shows the effect of yaw in increased wing speed as a result of wing geometry. As I suggest earlier, this is going to be negligible in most GA type aircraft and that reports suggest its wise to design a wing to reduce that effect.

 

 

[facthunter]

If you are doing say 120 knots and you yaw the plane the SPEED increment with one wing related to the other, and lift variation, is a pretty small % . I would say the largest effect is due to aircraft design, particularly relating to dihedral , one wing is shielded by the fuselage and most of all sweep back, which can cause some very interesting effects. A tail of large size and mostly above fuselage axis would have a discernible effect too with rudder application, but in the opposite sense. Nev

 

 

[djpacro]

Perhaps you could drop box it for those of us who are not privy to the report

Seems to have fallen off the NTRS. Here you are https://www.dropbox.com/s/orfmqo5847nfnh0/NASACR1975.pdf?dl=0

 

[Pearo]

Seems to have fallen off the NTRS. Here you are https://www.dropbox.com/s/orfmqo5847nfnh0/NASACR1975.pdf?dl=0

Thats a solid read. I did fluid mechanics at uni and I am struggling through that big time. For a laugh, I tried solving some of the equations, I failed. The young fella that works for us did a double degree in math, so next time things are quiet I am going to put him to the test. I dare say that paper is aimed at post grad aero mech people!

 

 

[djpacro]

Thats a solid read. .... I dare say that paper is aimed at post grad aero mech people!

Yep, it is a good but basic summary of stuff. I used to have that Fortran program on my computer.

[Pearo]

If you are doing say 120 knots and you yaw the plane the SPEED increment with one wing related to the other, and lift variation, is a pretty small % . I would say the largest effect is due to aircraft design, particularly relating to dihedral , one wing is shielded by the fuselage and most of all sweep back, which can cause some very interesting effects. A tail of large size and mostly above fuselage axis would have a discernible effect too with rudder application, but in the opposite sense. Nev

This is correct. The paper (book) that DJP supplied looks at making rides in small aircraft more user friendly. When you refer to rolling moment as a result of yaw (Clr), the author suggests it should me minismised to prevent spin entry. They dont give figures of lift derived from yaw, but they they do provide some data based on wing design. They also provide some detail on the tail contributing to roll.

 

At the end of the day, unless you really jump hard on the rudder at speed, there is going to be very little lift as a result of the difference in wing speeds.

 

 

[facthunter]

YES. It only happens AS you are yawing. Once you reach a steady state the effect is gone. As in a (continuous slip/ skid or sideslipping on purpose.. While a sideslip is totally crossed controls, often with full rudder, you won't spin if the minimum safe airspeed is maintained OR you don't pull the stick back. (same thing).

 

It's pretty uncomfortable awkward manoeuver, but executed well won't cause a spin. Errors are not being slow enough and not keeping the wing down. The aim is a high rate of descent at the slowest, safe speed, giving a steep approach angle. Nev