250 or point 65

I am not saying that the wings will buckle or snap if you go full deflection of the ailerons at full speed, what i'm saying is that this scenario has nothing to do with Va.

joepilot

FAR 25.331(c)(2)(ii) says it applies to "negative pitching acceleration".

Joe

joepilot

I've read FAR 25.333, and it tells you part of how to figure out the speed for Va, but it makes no attempt to define what the term means.

Joe

KiloAlphaPapa

I thought this was about something else, anyhow, penetrate at will.

GCMSGuru

There are some things about the 587 accident that have disturbed me for several years.

The first of these is the length of time that the crew remained in the wake turbulance. This has been portrayed as a significant time on the order of perhaps fifteen seconds. If indeed the wake turbulance was severe enough to require full control deflection, and the crew suspected wake turbulance, why didn't they simply decrease their climb and get below it? Why for that matter not a slight turn in either direction to achieve the same result: that of exiting the wake stream?

Also, I've seen some references that indicate that the PF asked for full power. Given that full control deflection was being required it seems obvious in any case that severe turbulance was being encountered from whatever source. Why then would the PF increase power rather than reducing and coming back on the yoke?

These things are very strange...

Dougdrvr

Pan Am 707 near Mt. Fuji, Japan, IIRC.

KC10 FATboy

You can kick the rudder as hard as you want in ONE direction. You CAN NOT kick the rudder say RIGHT then immediately LEFT. That will break off the tail.

-Fatty

KC10 FATboy

I don't want to sound disrespectful (I've already had that accused of me today on here), but, you sound like someone who hasn't been in wake turbulence from a heavy.

After flying formation takeoffs in a heavy behind heavies, I can assure you that 15 seconds isn't a long time to be in wake turbulence. Let me make myself clear, any time in wake turbulence is too much, but, you can get yourself in it and kind of get trapped. Also, just as soon as you get out of it, wham!, you're back in it.

As for being able to steer out of it, that's the problem, you might not be able to. Sometimes it requires holding max aileron deflection just to keep yourself from rolling inverted. You can push on the rudder to help turn the nose out of it, or, if your bank is high might help you drop the nose.

Imagine if wake turbulence suddently rolled you to an extreme angle of bank. And as you rolled to that extreme AOB, you tried pushing the nose over. You could find yourself inverted and into a spin.

There have been times whe I've had to use full aileron and rudder to keep from rolling over. And worse, if you pick the wrong direction to turn out of it, you then get flipped in the other direction from the wake turbulence from the opposite wing. Good times.

-Fatty

rotorhead1026

Va seems to have been well-defined on this thread. Theoretically, one can apply full control deflections and not break anything. There are some exceptions, well-noted previously.

Vb would be a max speed / mach where you can encounter a max gust (defined by FAR 25 - I don't recall the figure, maybe 50 fps) and not have any structural damage - theoretically. This doesn't necessarily relate to full control deflection, as as such is not directly related to Va. The speed is usually quite a bit higher. Indeed, I don't recall flying an airplane on which both were defined. I suspect that's due to different certification rules. I ain't no expert, but I think I got this right.

And note the liberal use of the word "theoretically". Y'all be careful out there ...

Senior Skipper

Since we're talking about the AA accident, my understanding was that below Va, you will not overstress the plane by moving ONE control surface to full deflection. So you can apply full rudder, or full aileron or full elevator and still be safe.

Am I correct, or do I need to go re-read the accident report?