# "Over-using the rudder"? Pilots, engineers, help please. **URL:** \ **Category:** In My Humble Opinion\ **Created:** [October 30, 2002, 12:34am UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468 "2002-10-30T00:34:16Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [November 3, 2002, 5:34pm UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/21 "2002-11-03T17:34:01Z")
Got a gent at our local field who owns an R-22 - for those of you who don’t know, it’s not a particularly speedy aircraft, even by helicoptor standards. Anyhow - he’s flown it from Indiana to the Pacific Ocean in California and back _twice_ in the last six months. We can’t figure out where he gets the money We can’t figure out how he can stand spending that many hours at a time in a teeny tiny helicoptor. But no one questions his cross-country skills. ---
**Author:** ![t-keela](https://avatars.discourse-cdn.com/v4/letter/t/a3d4f5/32.png) [@t-keela](https://boards.straightdope.com/u/t-keela)\ **Post date:** [November 3, 2002, 5:58pm UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/22 "2002-11-03T17:58:13Z")
I’m not sure if this applies here but I was reading several month’s ago that many air accidents are deemded “pilot error” because the insurance companies have “sublimits” in the passenger policies. Meaning, they don’t have to pay over a “certain” amount to survivors if the accident is “pilot error” or no fault. In other words,“Non-negligence on behalf of the airlines.” releases them from huge lawsuits. May explain some things ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 3, 2002, 8:02pm UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/23 "2002-11-03T20:02:13Z")
> [@](#): > > Anyhow - he’s flown it from Indiana to the Pacific Ocean in California and back twice in the last six months. Indiana to the coast _twice_ in just six months? He must have gotten a speedy one! 😃 (Actually the R-22 is faster than the Schweizer 300CB I’d been flying; but the 300CB is roomier.) ---
**Author:** ![happyheathen](https://avatars.discourse-cdn.com/v4/letter/h/b5e925/32.png) [@happyheathen](https://boards.straightdope.com/u/happyheathen)\ **Post date:** [November 3, 2002, 8:40pm UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/24 "2002-11-03T20:40:38Z")
From IN _to_ CA, I can see. It’s the “and back” part that makes me wonder 😛 ---
**Author:** ![Boxcar](https://avatars.discourse-cdn.com/v4/letter/b/c6cbf5/32.png) [@Boxcar](https://boards.straightdope.com/u/Boxcar)\ **Post date:** [November 4, 2002, 3:46am UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/25 "2002-11-04T03:46:46Z")
Back to AA587, the NTSB issued a [safety bulletin](http://www.ntsb.gov/Recs/letters/2002/A02_01_02.pdf) about pilot training and use of the rudder in February of this year. The thing that stands out in the bulletin was the description of what, exactly, manuvering speed means in terms of aircraft design. I understood that to be the speed at which you can make a full control input from one stop to the other without having to worry about bits and pieces coming off. With the rudder, at least, that is not true. From the Safety Bulletin: > [@](#): > > Transport-category airplanes certified by the Federal Aviation Administration (FAA) must meet the airworthiness standards in 14 CFR Part 25. Subpart C, pertaining to the airplane structure, includes Section 25.351, titled “Yaw maneuver conditions,” which requires that the airplane be designed for loads resulting from the following series of maneuvers in unaccelerated flight, beginning at zero yaw: (1) full rudder input resulting in full rudder deflection (or as limited by the rudder limiter system); (2) holding this full deflection input throughout the resulting over-swing and steady-state sideslip angles; and (3) while the airplane is at the steady-state sideslip angle, a release of this rudder input and the return of the rudder to neutral. The A300 was certified as having met this regulatory standard. In other words, **the airplane must be designed to withstand the results of a full rudder input in one direction followed by (after the airplane reaches equilibrium) a release of that rudder input.** > > It is noteworthy that these certification requirements do not consider a return of the rudder to neutral from the over-swing sideslip angle, nor do they consider a full rudder movement in one direction followed by a movement in the opposite direction. > > snip > > **…the Safety Board is concerned that pilots have not been made aware that, a full or nearly full rudder deflection in one direction followed by a full or nearly full rudder deflection in the other direction, even at speeds below the design maneuvering speed, can dramatically increase the risk of structural failure of the vertical stabilizer or the rudder.** bolding mine The bulletin also goes into the ease with which this can happen, even with a limiter and recommendations for training to prevent overuse of the rudder. What it boils down to is that even if the aircraft is at or below the manuvering speed, if you go from full left rudder to full right rudder, the tail could snap off. In what is looking like the preferred NTSB scenario for the crash of AA587, wake turbulance caused an upset of the aircraft. The pilot (or autopilot) applied rudder movements to correct these swings. Somewhere along the line, the nose of the aircraft was swinging in one direction, much as if rudder had been applied. In response, a correcting rudder movement was made in the opposite direction. Since the aircraft was already in a yaw, the stress of the correcting movement would be much like going from full-stop to full-stop with the rudder. Result is the broken tail. Do a search on “AA587 rudder” and you will find many more theories and articles out there. ---
**Author:** ![happyheathen](https://avatars.discourse-cdn.com/v4/letter/h/b5e925/32.png) [@happyheathen](https://boards.straightdope.com/u/happyheathen)\ **Post date:** [November 4, 2002, 5:57pm UTC](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468/26 "2002-11-04T17:57:41Z")
> [@](#): > > What it boils down to is that even if the aircraft is at or below the manuvering speed, if you go from full left rudder to full right rudder, the tail could snap off. Obviously. The problem is that it _shouldn’t_. The definition of green arc is “speeds at which full deflection of any control surface, in any sequence, **CANNOT** damage the aircraft”. What we have now is a little asterisk after that statement which reads “except A300-600’s” The certification test was deficient to require only a single deflection from neutral to stop, without then requiring a second deflection to opposite stop. What we have is a situation wherein, if the pilot stomps on the wrong pedal, then the correct one, everybody dies. That is not acceptable, and, if you go through the history of the investigatio at [www.ntsb.gov](http://www.ntsb.gov) , you will find that A300-600’s have been known to initiated uncommanded tail wagging, and the FDR is wired in such a way as to make it nearly impossible to tell if 587’s rudder deflections were commanded or not[sup]\*[/sup] - - “commanded” - the pilot told the plane to do it; “uncommanded” - the plane did it all by itself [Previous page](https://boards.straightdope.com/t/over-using-the-rudder-pilots-engineers-help-please/134468.md?page=1)