forget

The National Transportation Safety Board recommends that the Federal. .Aviation Administration:

Require the manufacturers and operators of transport-category airplanes to. .establish and implement pilot training programs that: (1) explain the. .structural certification requirements for the rudder and vertical stabilizer. .on transport-category airplanes; (2) explain that a full or nearly full. .rudder deflection in one direction followed by a full or nearly full rudder. .deflection in the opposite direction, or certain combinations of sideslip. .angle and opposite rudder deflection can result in potentially dangerous. .loads on the vertical stabilizer, even at speeds below the design. .maneuvering speed; and (3) explain that, on some aircraft, as speed. .increases, the maximum available rudder deflection can be obtained with. .comparatively light pedal forces and small pedal deflections. The FAA should. .also require revisions to airplane and pilot operating manuals that reflect. .and reinforce this information. In addition, the FAA should ensure that this. .training does not compromise the substance or effectiveness of existing. .training regarding proper rudder use, such as during engine failure shortly. .after takeoff or during strong or gusty crosswind takeoffs or landings.. .(A-02-01). .Carefully review all existing and proposed guidance and training provided to. .pilots of transport-category airplanes concerning special maneuvers intended. .to address unusual or emergency situations and, if necessary, require. .modifications to ensure that flight crews are not trained to use the rudder. .in a way that could result in dangerous combinations of sideslip angle and. .rudder position or other flight parameters. (A-02-02)

<a href="http://www.ntsb.gov/recs/letters/2002/A02_01_02.pdf" target="_blank">http://www.ntsb.gov/recs/letters/2002/A02_01_02.pdf</a>. .**************************************************. .The complete recommendation letter is available on the Web at the URL. .indicated above.. .The letter is in the Portable Document Format (PDF) and can be read using. .the Acrobat . .Reader 3.0 or later from Adobe. .(http://www.adobe.com/prodindex/acrobat/readstep.html).

RatherBeFlying

edited NTSB Text follows -- foot notes interrupt text:

This safety recommendation letter addresses an industry-wide safety issue involving omissions in pilot training on transport-category airplanes. Specifically, the National Transportation Safety Board has learned that many pilot training programs do not include information about the structural certification requirements for the rudder and vertical stabilizer on transport-category airplanes. Further, the Safety Board has learned that sequential full opposite rudder inputs (sometimes colloquially referred to as “rudder reversals&#8221 <img src="wink.gif" border="0"> —even at speeds below the design maneuvering speed1—may result in structural loads that exceed those addressed by the requirements. In fact, pilots may have the impression that the rudder limiter systems installed on most transport-category airplanes, which limit rudder travel as airspeed increases to prevent a single full rudder input from overloading the structure, also prevent sequential full opposite rudder deflections from damaging the structure. However, the structural. .certification requirements for transport-category airplanes do not take such maneuvers into account; therefore, such sequential opposite rudder inputs, even when a rudder limiter is in. .effect, can produce loads higher than those required for certification and that may exceed the. .structural capabilities of the aircraft.. .This safety issue was identified in connection with the Safety Board’s ongoing investigation of the November 12, 2001, accident involving American Airlines flight 587, an Airbus Industrie A300-600.2 Flight 587 was destroyed when it crashed into a residential area of Belle Harbor, New York, shortly after takeoff from John F. Kennedy International Airport (JFK), Jamaica, New York. Before impact, the vertical stabilizer and rudder separated from the fuselage.3 The 2 pilots, 7 flight attendants, 251 passengers, and 5 persons on the ground were 1 The design maneuvering airspeed is the maximum speed at which the structural design’s limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage.. .2 Under the provisions of Annex 13 to the Convention on International Civil Aviation, the Bureau Enquêtes-Accidents and Airbus Industrie are participating in the Safety Board’s investigation of this accident as the Accredited Representative and technical Advisor, respectively, of the State of Design and Manufacture.. .3 The vertical stabilizer and rudder assemblies were found floating in the water about 0.7 mile from the main impact crater. The vertical stabilizer was largely intact with no significant damage, although some localized areas of. .2. .killed. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight destined for Santo Domingo, Dominican Republic. The scheduled. .passenger flight was conducted under 14 Code of Federal Regulations (CFR) Part 121. The investigation is still examining many issues, including the adequacy of the certification standards for transport-category airplanes, the structural requirements and integrity of the vertical stabilizer and rudder, the operational status of the rudder system at the time of the. .accident, the adequacy of pilot training, and the role of pilot actions in the accident. It must be. .emphasized that, at this time, the Board has not yet determined the probable cause of the. .accident. Further, the Board is not aware of any prior events in which rudder movements have. .resulted in separation of a vertical stabilizer or rudder. Nonetheless, the investigation has. .revealed this safety issue, which should be immediately addressed. Before the separation of the vertical stabilizer and rudder, flight 587 twice experienced turbulence consistent with encountering wake vortices from a Boeing 747 that departed JFK ahead of the accident aircraft. The two airplanes were separated by about 5 (statute) miles and 90 seconds at the time of the vortex encounters. During and shortly after the second encounter, the flight data recorder (FDR) on the accident aircraft recorded several large rudder movements(and corresponding pedal movements) to full or nearly full available rudder deflection in one direction followed by full or nearly full available rudder deflection in the opposite direction.4. .The subsequent loss of reliable rudder position data is consistent with the vertical stabilizer. .separating from the airplane. The cause of the rudder movements is still under investigation.. .Among the potential causes being examined are rudder system malfunction, as well as flight. .crew action. Preliminary calculations by Safety Board and Airbus engineers show that large sideloads were likely present on the vertical stabilizer and rudder at the time they separated from the airplane. Calculations and simulations show that, at the time of the separation, the airplane was in an 8° to 10° airplane nose-left sideslip while the rudder was deflected 9.5° to the right. Airbus engineers have determined that this combination of local nose-left sideslip on the vertical stabilizer and right rudder deflection produced air loads on the vertical stabilizer that could exceed the airplane’s design loads. The Board notes that, at the time the vertical stabilizer and rudder separated from the airplane, the airplane was flying at 255 knots indicated airspeed (KIAS), which is significantly below the airplane’s design maneuvering speed of 273 KIAS. 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 damage were evident around the stabilizer-to-fuselage interface. At the lower end of the stabilizer, all of the attachment fittings were either fractured through the attachment hole or the stabilizer structure was fractured around. .the fittings. Portions of the closure rib and skin attach angle and front spar were also fractured from the stabilizer. Most of the rudder was separated from the vertical stabilizer except for portions of the rudder spar, which remained attached to the actuators and the upper hinge (no. 5 and 7).. .4 Preliminary information based on FDR data and an analysis of the manner in which rudder position data is filtered by the airplane’s systems indicates that within about 7 seconds, the rudder traveled 11° right for 0.5 second, 10.5° left for 0.3 second, between 11° and 10.5° right for about 2 seconds, 10° left for about 1 second, and, finally, 9.5° right before the data became unreliable. [FOUR complete reversals inside 7 seconds -- methinks the crew would have to be Tour de France material to work the pedals that fast]. .3. .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-swing5 and steady-state sideslip angles; and (3) while the airplane is at the steadystate 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. Although, as. .previously mentioned, most transport-category airplanes are equipped with rudder limiter. .systems that limit rudder deflection at higher airspeeds, which prevents single rudder inputs from causing structural overload, 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. The Safety Board is also concerned that pilots may not be aware that, on some airplane types, full available rudder deflections can be achieved with small pedal movements and comparatively light pedal forces. In these airplanes, at low speeds (for example, on the runway during the early takeoff run or during flight control checks on the ground or simulator training) the rudder pedal forces required to obtain full available rudder may be two times greater and the rudder pedal movements required may be three times greater than those required to obtain full available rudder at higher airspeeds. On the A300-600, for example, at airspeeds lower than 165 knots (when rudder travel is unrestricted by the airplane’s rudder limiter system) the rudder can travel +/-30°, requiring a pilot force of about 65 pounds to move the rudder pedals about 4.0 inches. However, at 250 knots, when the limiter restricts rudder travel to about +/-9.3°, a pilot force of about. .32 pounds is required to move the rudder pedals about 1.3 inches. The rudder system on the. .A300-600 uses a breakout force6 of about 22 pounds. Thus, at 250 knots, the rudder can reach. .full available travel (9.3°) with a pedal force of only 10 pounds over the breakout force. There. .are several other types of rudder limiter systems that operate differently. For example, on some. .airplanes, full pedal travel (and corresponding pedal force) is required to obtain full available. .rudder, regardless of airspeed, even though the maximum available rudder deflection is reduced. .with airspeed by mechanical means. Lacking an awareness of these differences in necessary. .pedal force and movement, some pilots, when sensing the need for a rudder input at high speeds, may use rudder pedal movements and pressures similar to those used during operations at lower airspeeds, potentially resulting in full available rudder deflection.. .5 Over-swing refers to the maximum sideslip angle resulting from the airplane’s momentum as it yaws in response to the rudder’s movement; the over-swing sideslip angle will always be greater than the subsequent steady-state sideslip angle.. .6 Breakout force is the force required to start moving a flight control such as the rudder pedal or control column.. .4. .The Safety Board notes that there is a potential for pilots to make large and/or sequential. .rudder inputs in response to unusual or emergency situations, such as an unusual attitude or. .upset, turbulence, or a hijacking or terrorist situation. In fact, unusual attitude training already exists7 that encourages pilots to use full flight control authority (including rudder), if necessary, in response to an airplane upset. Further, the Board is aware that, since the terrorist attacks of September 11, 2001, operators and pilots have been discussing ways to disable or incapacitate would-be hijackers in cockpits or in cabins during flight. Although the Board understands the need to formulate effective maneuvers for addressing such unusual or emergency situations, the Board is also concerned that, without specific and appropriate training in such maneuvers, pilots could inadvertently create an even more dangerous situation if those maneuvers result in loads that approach or exceed the structural limits of the airplane.. .Finally, notwithstanding the concerns noted above about the potential danger of large and/or sequential rudder inputs in flight, it should be emphasized that pilots should not become. .reluctant to command full rudder when required and when appropriate, such as during an engine. .failure shortly after takeoff or during strong or gusty crosswind takeoffs or landings. The. .instruction of proper rudder use in such conditions should remain intact but should also. .emphasize the differences between aircraft motion resulting from a single, large rudder input and. .that resulting from a series of full or nearly full opposite rudder inputs. As previously noted, the Safety Board’s examination of the adequacy of the certification standards is ongoing and no conclusions have yet been reached in that regard. However, on the basis of the investigative findings to date, the Board believes that the FAA should require the. .manufacturers and operators of transport-category airplanes to establish and implement pilot. .training programs that: (1) explain the structural certification requirements for the rudder and vertical stabilizer on transport-category airplanes; (2) explain that a full or nearly full rudder deflection in one direction followed by a full or nearly full rudder deflection in the opposite direction, or certain combinations of sideslip angle and opposite rudder deflection can result in potentially dangerous loads on the vertical stabilizer, even at speeds below the design maneuvering speed; and (3) explain that, on some aircraft, as speed increases, the maximum available rudder deflection can be obtained with comparatively light pedal forces and small pedal deflections. The FAA should also require revisions to airplane and pilot operating manuals that reflect and reinforce this information. In addition, the FAA should ensure that this training does not compromise the substance or effectiveness of existing training regarding proper rudder use,. .such as during engine failure shortly after takeoff or during strong or gusty crosswind takeoffs or landings. The Safety Board also believes that the FAA should carefully review all existing and proposed guidance and training provided to pilots of transport-category airplanes concerning special maneuvers intended to address unusual or emergency situations and, if necessary, require modifications to ensure that flight crews are not trained to use the rudder in a way that could result in dangerous combinations of sideslip angle and rudder position or other flight parameters.. .7 The widely used Airplane Upset Recovery Training Aid, which was created by Airbus Industrie, the Boeing Company, many major domestic and international airlines, and major pilot organizations, states that, “pilots must be. .prepared to use full control authority, when necessary. The tendency is for pilots not to use full control authority because they rarely are required to do this. This habit must be overcome when recovering from severe upsets.”. .5. .Therefore, the National Transportation Safety Board recommends that the Federal Aviation Administration:Require the manufacturers and operators of transport-category airplanes to. .establish and implement pilot training programs that: (1) explain the structural certification requirements for the rudder and vertical stabilizer on transportcategory airplanes; (2) explain that a full or nearly full rudder deflection in one direction followed by a full or nearly full rudder deflection in the opposite. .direction, or certain combinations of sideslip angle and opposite rudder deflection can result in potentially dangerous loads on the vertical stabilizer, even at speeds below the design maneuvering speed; and (3) explain that, on some aircraft, as speed increases, the maximum available rudder deflection can be obtained with. .comparatively light pedal forces and small pedal deflections. The FAA should also require revisions to airplane and pilot operating manuals that reflect and reinforce this information. In addition, the FAA should ensure that this training. .does not compromise the substance or effectiveness of existing training regarding. .proper rudder use, such as during engine failure shortly after takeoff or during strong or gusty crosswind takeoffs or landings. (A-02-01). .Carefully review all existing and proposed guidance and training provided to pilots of transport-category airplanes concerning special maneuvers intended to address unusual or emergency situations and, if necessary, require modifications to ensure that flight crews are not trained to use the rudder in a way that could. .result in dangerous combinations of sideslip angle and rudder position or other flight parameters. (A-02-02). .Chairman BLAKEY, Vice Chairman CARMODY, and Members HAMMERSCHMIDT,. .GOGLIA, and BLACK concurred in these safety recommendations.. .By: Marion C. Blakey. .Chairman. .Original Signed

Looks to me work is needed in the flight control and feel systems -- breaking an airliner should be hrd work.

LatviaCalling

I don't know, but the preliminary NTSB report seems to me like absolute bull. It's like saying that you can't drive with summer tires in snow. Of course you can't, but how gentle can you be to reach the maximal tolerance of the rudder? Apparently, not a hell of a lot.

BOING

This has been a long time coming but is not unexpected. It has been quite obvious that far too many procedures are being implemented on the basis of a little knowledge and a lot of SIMULATOR testing by people not competent to formulate such procedures. The last time I commented on this subject the return post questioned whether I had ever heard of a rudder load limiter since the respondant clearly considered that these items would always prevent structural problems. Unfortunately I returned from a trip too late to make an effective reply.. . As a cost cutting measure commercial aviation training nowadays focuses on routine flight profiles using autoflight systems with almost zero training on aviation fundamentals and aircraft handling. The cynical assumption is that pilots bring this knowledge to the job (or that in modern commercial operations they do not need this training). This may be true for certain ex-military pilots but it is resoundingly not true for the present day run-of-the-mill entrant in the US. This is not to denigrate the ABILITY of these entrants it is to point out their LACK OF EXPOSURE. It is easy to see how new pilots would buy into the idea that the aircraft manufacturer has solved all the possible handling problems. This is the viewpoint encouraged by flight training departments who prefer the sausage machine approach to keep costs down. If you need examples of the lack of basic aircraft handling knowledge of many pilots just remember all the comments by the brave souls who were going to carry out high altitude aerobatics in a transport aeroplane to upset hijackers.. . In the case of the use of rudder to recover from upsets the idea started out quite sensibly - if you needed a little help to speed up a roll use an amount of rudder. Unfortunately, over the years the "little help" turned into an automatic application of full rudder regardless of actual flight conditions. I see this every training session. This attitude is encouraged by simulator programming which often provides negative training. In our simulators the box will not allow upset recovery until it has reached predefined upset limits EVEN IF THE AEROPLANE WOULD HAVE RECOVERED UNDER THOSE SAME CONDITIONS. Therefore use of full rudder is encouraged. If the aeroplane (simulator) does not recover with the rudder you have applied - try some more. Since the simulator is programmed not to recover inevitable full rudder is eventually applied. Negative training.

ironbutt57

If we are taught to "rudder" our way out of a slow speed upset to avoid stalling the wing with aileron deflection....then this "new finding" flushes that all down the toilet...looks like somebody has paid a lot of money to cover up a basic design flaw...who (whom)?

Captain104

Sorry,. .4 weeks ago, in the thread "Whitnesses saw AA 587...",I guessed:"I dare say, during the next weeks the profs will circle around those AA procedures you all heard about: the recovery out of unusual attitudes by applying full rudder".. .Retour:. .1)A honorable member called "The Prisoner" booked me on the train:"me thinks a Captain of C 150"!. .2)In a post, McD Administrator corrected me, "the emphasis is on PROPER and CONTROLLED inputs".

Reading the NTSB-release today carefully, I feel a bit like "Mr.Piggy who knows it all". What makes me thinking is a very long explanation they give there dealing exclusivly with training aspects. In their bag no yawdamper-problems, no wrong wiring somewhere, no computer problem, nothing. <img src="confused.gif" border="0">

Than Boings interesting post, in which he talks about:"therefore use of full rudder is encouraged". Comments are welcome, because I'm really <img src="confused.gif" border="0">

411A

It would appear that many here are rather "new" to high speed jet aircraft operations. . .The problems with large rudder inputs were taught many years ago to the pilots of the Boeing 707...now we have a new group, but many lessons of the past have been forgotten, or never learned.. .The results are there for all to see....aerodynamics do not necessarily change with the calendar.

[ 09 February 2002: Message edited by: 411A ]</p>

Wino

FOR IMMEDIATE RELEASECONTACT: Gregg Overman. .Director of Communications. .Allied Pilots Association. .817-302-2250

. .ALLIED PILOTS ASSOCIATION RESPONDS TO NATIONAL TRANSPORTATION. .SAFETY BOARD RECOMMENDATION CONCERNING PILOT TRAINING OMISSIONS:. .GUIDANCE NEEDED 'AS SOON AS POSSIBLE'

Fort Worth, Texas (February 8, 2002)-The Allied Pilots. .Association (APA), which serves as collective bargaining agent. .for the 11,000 pilots of American Airlines, responded to the. .NTSB's Safety Recommendation concerning omissions in pilot. .training on transport-category airplanes by calling for specific. .guidance as soon as possible.

. .The NTSB issued its Safety Recommendation today as part of the. .ongoing investigation into the accident involving American. .Airlines Flight #587. With today's Safety Recommendation, the. .NTSB acknowledged that pilots have not been informed that it is. .possible, in certain situations, to overstress key aircraft. .components even when on-board load limiting systems are in place. .and functioning properly.

. ."Pilots worldwide lack meaningful guidance regarding 'how much is. .too much' when it comes to rudder inputs," said Captain John. .Darrah, APA President. "As the NTSB notes in its Safety. .Recommendation, the widely used Airplane Upset Recovery Training. .Aid states that 'pilots must be prepared to use full control. .authority when necessary.'

. ."We look forward to receiving specific guidance for our pilots as. .soon as possible in this critical flight-safety matter."

. .In today's Safety Recommendation, the NTSB notes that it has not. .yet determined the probable cause of the Flight #587 accident.. .The NTSB also noted that the source of the rudder movements. .recorded by the Digital Flight Data Recorder on board the. .aircraft just before the accident have not been pinpointed.. .According to NTSB Chairwoman Marion Blakey during the NTSB's. .press conference this morning, "We do not know if those rudder. .movements were caused by the stabilizer's failure, or if the. .rudder movements perhaps were caused by a mechanical problem that. .was separate from that, or whether these movements were caused by. .the pilot.

. ."This Recommendation is about education and training," said. .Blakey. "It is not about pilot error."

. .Headquartered in Fort Worth, Texas, APA was founded in 1963. The. .union's Web site address is <a href="http://www.alliedpilots.org" target="_blank">www.alliedpilots.org</a>

Shore Guy

This NTSB recommendation comes as no surprise in the course of this investigation. However, I believe it to be of little value in the ultimate solving of this accident investigation.

I am not privy to the upset training program at AAL, but it is hard to fathom that any professional pilot would manually enter the abrupt and contradictory inputs mentioned to date. Keep in mind that one of the suspected culprits in this accident is wake turbulence. Wake turbulence at the angles/aircraft types involved normally produces a rolling motion, not normally compensated with by rudder input. At the altitude/speed these events occurred, normally a pilots feet are on the floor, letting the yaw damper system do its job.

One aspect of this accident that I have not seen particularly addressed is that the forces/stresses on the vertical stabilizer/rudder (yaw axis) of large twin-engine transports is (my opinion) greater than other transport aircraft. Vertical stabilizer and rudder area (and therefore the stresses involved) on large twins is disproportionately greater than on other transport aircraft because of the need to keep the aircraft tracking straight with loss of very high thrust engines at a critical time (V1). Not until the advent of large, high powered engines was this situation encountered. In normal operations, this is routinely demonstrated by the relative “sporty” nature one must approach a crosswind takeoff or landing in large twins. These aircraft are weathervanes and take a large amount of control input to counteract this tendency.

Any engineering types out there care to provide more insight into this?

Ignition Override

Interesting.

At least one US major airline gives no training on unusual aircraft attitudes. Why? Could it be money, even before Sept 11, but long after the loss of the UA 737 in Colorodo Springs and the 737 near Pittsburgh? Not to pick on the 737s, just to point out the perceived need for a new type of training in all transport planes. Doesn't United teach it in each fleet?

For this "other" airline, unusual attitude training (in our fleet) is to have an engine failure at about 18-20 degrees pitch on takeoff. But we still, in December, wasted some time and money on simulator PRM approaches, which are NOT to be done anymore at the "Peoples' Republik" hub! . . Woops! The Peoples' Thought-Korrektness Polizei might be reading this in Eagan...they said that "the Wall" came down, but most of us know better.

As for training, the FAA might like to sign off any slight change in the trainingsyllabus...more paperwork=more job security.

[ 09 February 2002: Message edited by: Ignition Override ]</p>

MasterGreen

Shore Guy : I was under the impression this was a "after take off - low level climb event", so your premise of :

"At the altitude/speed these events occurred, normally a pilots feet are on the floor, letting the yaw damper system do its job."

Is probably an orange herring and is suspect in every way. I don't know your background - although your profile says "Major Airline". I will be generous and assume an RTFQ error before I rant on.

411A has got it just about on the button here I fear. There is a new generation of "handlers", not "pilots", out there who can only fly the way they have been taught. This is not to say they can't fly - but they are severely limited in their experience and backgrounds and this is the new way of it. Unfortunately this is the "new thing". Automation takes the place of systems knowledge and skill / feel is replaced by, yes, another computer system.

On a positive note there is a very good article on Upsets and Recovery here :. . . .<a href="http://www.boeing.com/commercial/aeromagazine/aero_03/textonly/fo01txt.html" target="_blank">Aero Magazine Web Page</a>

Shore Guy

Master Green and all,

Perhaps my reference to "feet on the floor" during the wake turbulence encounter was slightly inappropriate, but, according to the NTSB, the event began some 93 seconds after liftoff, with normal climb/acceleration to that point. With normal profiles in a large twin, that does not qualify this (in my opinion) as an "after take off -low level climb event” as you describe. As I recall, the aircraft was at or close to clean maneuver speed, where critical rudder inputs are not normally needed. Your offensiveness in your defense was not necessary. (By the way, what is “RTQF”?).

An A-300 or any other large twin is not a Pitts Special, nor should it be flown as one. There are different skills/disciplines required to fly each one well – and sometimes those skills are mutually exclusive.

I will once again pose my original query – is there someone with an engineering background who would like to address the specific loads/stresses on the vertical stabilizer/rudder on large twin engine aircraft?

Old King Coal

Well imho taking your feet away from the rudder pedals in a big twin jet (or indeed any aircraft), in any stage of flight is just asking for trouble !

Also, I was always taught to use the rudder purposefully but also gently - it's a necessarily very powerful control - it needs some respect.

Ps. RTFQ = Read the ******* question, whilst RTFA = Read the ******* answer.

SaturnV

ORAC posted the following link in the earlier thread about AA pilots seeking to have the A300 grounded.

<a href="http://pull.xmr3.com/p/25356-E59F/30254611/rudder.html" target="_blank">http://pull.xmr3.com/p/25356-E59F/30254611/rudder.html</a>

This is AviationWeeks technical analysis article (with graphs) on how excessive rudder movement can overstress the fin. This article is cited in the NY Times story of Feb 9, below, and was also cited in a USA Today article earlier this week:

"WASHINGTON, Feb. 8 - The inquiry into the crash of an American Airlines plane in Queens three months ago has shown that a passenger jet can break up in flight if the rudder suddenly flips back and forth, investigators said today.

"Pilots should be trained that such a breakup can occur even at the low speeds that rudder movements had previously been considered safe, the investigators added.

"Government rules on how strong an airplane's tail must be do not take into account sudden back-and-forth rudder movements like those that occurred in the last moments of American Airlines Flight 587, the National Transportation Safety Board said.

"In fact, the board said, in some cases a fairly light tap on the rudder pedals may be enough to cause structural damage. If the pilot reverses the rudder just as the plane reaches its limit in one direction, investigators said, the movement can overload the tail, which they say may have. .happened to Flight 587.

""It is possible, particularly with reverse action, to do catastrophic damage to the tail assembly," said Marion C. Blakey, the board chairwoman.

"In an unusual response, the Federal Aviation Administration immediately said that it agreed with the substance of the recommendation and would make a formal answer shortly. The. .safety board recommendations are advisory; the F.A.A. sets pilot training requirements.

"The recommendation is in contrast to a text jointly developed by Airbus, Boeing and major airlines on recovering from aircraft "upsets." That training tool, as the safety board pointed out today, stresses that "pilots must be prepared to use full control authority when necessary."

"The board said that the problem might extend to all big jets, not just Airbuses, and not just those with tails made of composites, as the tail on the A-300 is. The board, which based its recommendation on calculations of side stresses that would have been produced by the plane that. .crashed and the rudder movements that were recorded, is still trying to determine whether there was a pre- existing weakness in the tail. The board is also continuing to investigate whether the rudder moved because the pilots. .pushed the pedals, or whether it moved because of a mechanical malfunction.

""Even if investigators determine that the rudder moved in response to "pilot inputs," as engineers call it, Ms. Blakey stressed, "this tecommendation is about pilot education and training; it is not about pilot error."

"But it is also about the standards used to certify the airplane as safe to fly. Those standards, used by both the F.A.A. and, in the case of the Airbus, its European counterpart, are taken by pilots to mean that a safety system called a rudder limiter will prevent them from. .overstressing the tail.

"In normal flight, using the rudder will turn the nose of the plane out of line with its direction of travel, like a car skidding on an icy road that points to the side without changing direction. In the air, it is called a yaw. In a. .big airplane, in which the tail is 100 feet or more behind the center of gravity, a yaw can produce large pressures on the vertical tail.

"The rudder limiter on the A-300 and many similar planes blocks the rudder from moving too far and creating a dangerous yaw. The faster the plane flies, the closer the limiter holds the rudder to the neutral position. Aircraft builders calculate the maximum force that the yaw can produce and design the plane to survive 50 percent more.

"If the rudder is pushed to its limit, the plane will swing hard, and because of its momentum, will reach maximum yaw and then settle back slightly toward straight, in a new equilibrium.

"The problem is that the certification test assumes that when the plane reaches maximum yaw, the rudder is held steady or returned to neutral position, and that the rudder is not pushed in the opposite direction until the plane has. .reached equilibrium. In the case of the Queens crash, the rudder appears to have moved in the opposite direction at the moment of maximum yaw, and that may have overstressed the tail.

"That possibility was first raised publicly by Aviation Week & Space Technology magazine on Jan. 21, after it conducted its own analysis.

"This was news to many pilots. "The traditional wisdom is that the rudder limiter will prevent you from exceeding the certification limit," said a senior captain at another airline who has trained scores of pilots on using the rudder.

"But the captain, who did not want to be further identified added, "there are no maneuvers we teach at all that would require you to use full rudder in one direction, then another direction.""

Danish Pilot

Regarding the use of rudder, could it be because (as 411A point out) that the older generation was tought to fly on tailwheel aircraft? I remeber the schoolflying, and we were strictly taught to use any amount of rudder required, to recover from stall or other flight manouvers before those would end in a stall. So the "use of rudder" is/was burried deep inside, and that goes for me allso, until I did some time on a tailwheel aircraft (Pilatus PC6). You simply cannot fly that one, if you don´t start useing rudder as a "tool" rather as an "solution". Don´t know if that make sense, but that was what I noticed about my self. <img src="cool.gif" border="0">

E. MORSE

No Danish Pilot, has to do with the difference between large jets and lightplanes.

And yes, rudder is the tool for tailwheel aircraft on the ground !

Cheers

John Farley

I am concerned that several pilots seem genuinely baffled that rudder use could have the fin off a fully serviceable aircraft that was properly designed and certificated. Unhappily it can, as I will try to explain in a moment.

Before I go on please may I emphasise I am not suggesting this caused the accident this thread is about, but offer these comments to the general debate about rudder use that is going on.

The mechanism I refer to is the same one employed by adults when helping youngsters to enjoy a swing. The adult applies a very small force at just the right moment in the cycle and by so doing builds up the oscillation until in the end the displacement of the swing can become very large indeed (with much yelping from the occupant)

A similar relatively small side force generated by rudder deflection, repeatedly applied, can cause a yaw oscillation to build rather than damp. There are two possible end points in this case, either the fin will stall due to the size of its AoA (in which case the aircraft will depart from controlled flight) or the fin will break before it stalls due to aerodynamic overload.

We all enjoy the powerful damping effects of yaw autostabilisers when they produce a very small force and apply it at the right moment to reduce the yaw oscillations. Now imagine a yaw autostabiliser that is working in reverse. Or a pilot that is out of phase with his feet. Or a pilot that is pushing the rudder pedals correctly but control actuation lags result in those correct inputs being delayed to an incorrect time.

CrashDive

Just in case anybody doesn't know who John Farley is: [quote]John Farley OBE AFC CEng is a renowned test pilot.

He became a fighter pilot with the RAF and following training as an instructor, taught flying at RAF College Cranwell. He returned to the Royal Aircraft Establishment (Farnborough) and spent 19 years contributing to the development of the Harrier. He retired as Chief Test Pilot BAe Dunsfold.

Five years as Manager of Dunsfold and a further two as Special Operations Manager at BAe Kingston completed his career with British Aerospace. In 1990 he became the first Western test pilot invited by the Russians to fly the MiG-29 fighter.<hr></blockquote>

RatherBeFlying

Footnote 4 in the NTSB letter catches my interest:

"Preliminary information based on FDR data and an analysis of the manner in which rudder position data is filtered by the airplane’s systems indicates that within about 7 seconds, the rudder traveled 11° right for 0.5 second, 10.5° left for 0.3 second, between 11° and 10.5° right for about 2 seconds, 10° left for about 1 second, and, finally, 9.5° right before the data became unreliable."

These are the last 7 seconds the fin and rudder were well enough attached to give reliable FDR readings. The FDR shows FOUR complete rudder reversals inside "7 seconds" but the sum of the intervals given only comes to 3.8 seconds and we are not given the travel time of the last rudder movement to the right. The letter does show that the last reliable FDR reading shows the a/c in a left yaw of 8-10° and that that combination exceeded the structural strength.

We are only given the last yaw angle -- I would really like to see yaw vs. rudder position in these 7 seconds. In my opinion, the crew would have to be Tour de France material to work the pedals that fast against a 32 pound force. This inclines my suspicions to the flight control system.

In traversing the two wake vortices, it is possible that local effects confused the yaw damper sensor system and resulted in counter-corrective rudder movements.

I am tempted to propose an expensive and hazardous experiment with a 747 and A300 flying the accident flight profile in a remote area with an unfiltered FDR -- remote control or ejection seats for the A300 crew highly recommended.

whatshouldiuse

Not a pilot, but a frequent Pax...If I interpret the NTSB document correctly, it recommends "not using Rudder reversal at high speeds as this can cause structural damage to the vertical tail fin"

. .How far am I off base from what the report states??