NTSB Recommendation re Airbus Rudder Travel Limits

[PJ2]

NTSB Recommendation A-10-119/120, August 04, 2010 (http://ntsb.gov/recs/letters/2010/A-10-119-120.pdf)

Reference: American Airlines 587, Air Canada 190 accidents

[FIRESYSOK]

It's amazing that a seemingly seasoned crew would introduce major rudder deflections in a jet airplane with 3000psi hydraulics and triple PCUs. To do this at 36000 feet is asking for certain death. Feet belong on the floor, point blank period. When aileron is exhausted and the airplane continues to roll, it may be appropriate but the first instict should be aileron and reducing AOA.

[mm43]

PJ2

It would appear that EASA and the NTSB are both in agreement regarding the retro fitting of a PTLU to the aircraft mentioned. So, I am a little surprised that the NTSB needs to reiterate its position on the matter to EASA.

The following from the NTSB letter -
On March 19, 2010, EASA further indicated that “its previously held position on the pilot training out as being an efficient and sufficient measure to avoid any new hazardous situations has to be reconsidered following more recent service experience which confirms that crew use of rudder pedal inputs in upset encounters cannot be ‘[B]trained out.’” EASA therefore indicated that it plans to require the PTLU on Airbus A310 and A300-600 aircraft models.Possibly the NTSB are hoping that EASA will be prompted into issuing an AD forthwith.

mm43

[BEagle]

In the American Airlines flight 587 accident, the pilot applied four full alternating rudder inputs; after the fourth input, the aerodynamic loads on the vertical stabilizer exceeded the vertical stabilizer’s ultimate design load (at about twice the maximum load), and it separated from the airplane. In the Air Canada flight 190 accident, the pilot applied three alternating rudder inputs and exceeded the limit load by 29 percent.

What sort of idiots are they training over there? Or perhaps that should be 'what sort of idiotic training is being given over there'?

This NTSB recommendation is utter rubbish. Teach your pilots to fly correctly!

[protectthehornet]

what amazes me is that a plane that can destroy itself in flight wouldn't have rudder limiters to protect its structure. the jets I've flown either had a placcard saying : no full control throw above blank altitude.

or a gadget that prevented you from doing too much.

[p51guy]

BEagle, we are not trained to fly like that over here. AA conducted advanced maneuvering training at high angles of attack to use rudder to assist in recovery but not in a 250 knot climb out of JFK. The A300 had such severe yaw both engines snapped off along with the vertical stabilizer. The vertical stab on that particular aircraft had delamination where it separated coming out of the factory. It was patched with a brace right where it broke off. We know severe yaw was involved which could be from irratic rudder inputs or the vertical stab leading edge separating causing the yaw. Would you let your FO use that kind of rudder control because of wake turbulence?

[Huck]

Correct me if I'm wrong, but there was no data in the American crash showing rudder pedal input - only rudder deflection. And the yaw damper had been written up prior to that flight. And the pilots are dead, thus unable to explain what happened.

[p51guy]

I agree, the chance that both pilots would allow those reported rudder reversals to snap the vertical stab is not possible. It made it a lot cheaper for Airbus blaming it on the dead copilot though. Any flight attendant standing in the back would probably have been killed before the breakup with the lateral g forces. I wish they had data on actual rudder pedal movement, not just rudder displacement. The FDR also averaged movement of the rudder so left a lot to be desired for real time info.

[Zeke]

Correct me if I'm wrong, but there was no data in the American crash showing rudder pedal input - only rudder deflection.

All the control inputs were recorded.

http://www.ntsb.gov/events/2001/aa587/flight_path_web01.wmv

[Huck]

Those aren't inputs - they're control displacements.

The YD moves the rudder pedals too.

[FIRESYSOK]

Not to disrespect those who have departed, but watch that .wmv clip. The FO in clearly overcontrols through the first and second wake encounters. Extrordinarily aggressive IMO. The rudder and aileron are moving in the same direction which is probably a result of deliberate manual input. The training program was flawed, and this was probably a pilot who got too excited in a heavy airplane at 250 knots with plenty of roll authority to counteract a wake encounter. Interesting to note all of his previous experience prior to joining AA was in aircraft with unboosted controls.

[GlueBall]

The October 2002 NTSB hearing heard evidence from one American Airlines Captain John Lavelle, who had flown a number of times with F/O Stan Molin on the B727 in 1997-1998. He recalled that F/O Molin had aggressively used rudder in an oscillatory mode on a B727 to attempt to control roll. This action didn't level the wings, but it did create sideloads due to yaw. They discussed this during the flight. Captain Lavelle recalled that Molin had told him that he was following American Airlines training procedures. The NTSB concluded that the PF [F/O Sten Molin] tended to react to wake turbulence using excessive control inputs, and that his control inputs in this case were too aggressive and the degree of his initial rudder pedal activation was unnecessary to control the aircraft. :eek:

[EW73]

Huck....

your quote:

"The YD moves the rudder pedals too."

That must be an AB thing, since that's not the case in the 737NG!

Cheers..

[sprite1]

Huck,

Your statement about the yaw damper is incorrect.

The rudder trim moves the pedals so you can see the level of displacement. If the yaw damper was to move the pedals, you would be getting tiny vibrations during flight.

That goes for A320 and B737 series anyway. The system set-up shouldn't be any different for other types.

[protectthehornet]

p51 guy is right...if you over control, your flight attendants go flying, your passengers get sick and even YOu can get sick or the other pilot anyway.

[c46r]

Where does AF 447 fit into this????????????

[Huck]

You guys are right, I read it wrong. From the report:

The yaw autopilot actuator(emphasis mine), which produces yaw autopilot commands,42 is a single
unit that houses two electrohydraulic actuators, each of which is controlled by a flight
control computer. The yaw autopilot actuator has an output lever that is connected
through a torque limiter to the main bellcrank. The torque limiter allows a pilot to
override an autopilot output as long as the pilot applies about 143 pounds more than the
rudder pedal feel forces. Yaw autopilot commands are limited by software in the flight
control computers to a maximum of 34º of rudder per second. The yaw autopilot actuator
and the rudder pedals are rigidly linked, so a yaw autopilot input (through the main
bellcrank) results in pedal motion.


I know I'm in the minority here. But watch that video of the control movements again, keeping an eye on the artificial horizon. Look at the size of the control deflections. Tell me that there was nothing going on besides a wake encounter.....

[RatherBeFlying]

The present design is an ergonomic trap.

The ratio between breakout force and full deflection at high speeds makes rudder next to impossible to modulate.

[Huck]

Sorry, I meant yaw control from the A/P, not the YD....

Watch the artificial horizon, combined with the size of the control movements. About 19:15:53.

I doubt I've ever moved a yoke like that at 250 knots. Sure, maybe he was just a really really bad pilot. But maybe something was happening to that vertical stabilizer - something that doesn't show on the FDR.

[leftseatview]

Like any turbulance,you need to "ride it out" in wake turbulance and steady gentle inputs are the norm.
Quite often low experince pilots will quote "procedures"chapter and verse...without a clear idea as to where and how to apply them.
Another factor is that this event occured just after 911...maybe in this context wanting to "stay in control come what may" might have been a possible mind set.
Pure conjecture.....but just a thought about all the possible factors which could have played a role.

[stepwilk]

Well, you're absolutely right about that: Suggesting that there is a connection between 9/11 and the way that AA flight was flown is indeed pure conjecture. Also pure claptrap.

[vapilot2004]

The rudder channel raw data from the AA587 crash was so inconceivably unrealistic, NTSB investigators had to run it through the filter of a matrix of other A300 aircraft recordings to make any sense of it.

Part of the challenge involved the slow recording rate the A300 FDR box used. Those units were de-certified and replaced.

[411A]

The rudder channel raw data from the AA587 crash was so inconceivably unrealistic...

And, no wonder.
Whom in their right mind would bicycle pedal the rudder on a jet transport airplane at any speed, let alone a higher speed.
Oh, I forgot...it was an American Airlines airplane.:rolleyes:

[Zymurgist]

Quote “Where does AF 447 fit into this????????????"

AF447 was in Alternate Law flight mode. This turns off the rudder limiter and allows the pilot full rudder deflection (~+/-30d) even if travelling at cruise speed. Normally the rudder is limited to about 4d of travel at cruise.

It takes only about a half inch of pedal movement to get the full 4d deflection and there is nothing to stop the pedal from traveling to the floor nor stop the rudder from deflecting the full 30d if the limiter is turned off.

It would be very easy for the pilot to overcorrect for an aircraft upset due to turbulence and or a stall and exceed the maximum design load on the VS with the limiter turned off.

[fox niner]

I don't get it. If a very, very dangerous flight technique can not be trained out of somebody, then that pilot should be grounded. Regardless of the strength of the vertical fin.

[411A]

If a very, very dangerous flight technique can not be trained out of somebody, then that pilot should be grounded.
One might reasonably then ask, if the company training program taught the pilot how to improperly apply the rudder in potential 'upset':eek: situations...what the heck was wrong with the company?:ugh::ooh:

[mm43]

Zymurgist wrote in Post #24 (http://www.pprune.org/rumours-news/423360-ntsb-recommendation-re-airbus-rudder-travel-limits-2.html#post5855682)

AF447 was in Alternate Law flight mode. This turns off the rudder limiter and allows the pilot full rudder deflection (~+/-30d) even if travelling at cruise speed. Normally the rudder is limited to about 4d of travel at cruise. AF447 was an A330-206, and contrary to what you have indicated, when the control mode changes from Normal to Alternate Law, the Rudder Travel Limiter Unit locks the maximum available amount of rudder travel at the last valid angle based on CAS and barometric altitude. At FL350 and M0.80 this was +/-7.9°, and is the value found by Airbus on investigation of the RTLU after the recovery of the Vertical Stabilizer. The A330 series also has a PTLU fitted as standard.

mm43

[Flight Safety]

RatheBeFlying said

The present design is an ergonomic trap. The ratio between breakout force and full deflection at high speeds makes rudder next to impossible to modulate.

He's absolutely correct.

During the NTSB investigation of AA587, they had several pilots (including airline and test prilots) run through a series of tests at various airspeeds to see how well the pilots could modulate rudder deflection. Rudder deflection on this type is limited with increasing airspeed by progressively limiting rudder pedal travel. At higher speeds there's only a small difference (forget the exact figures now) between the breakout force and full deflection. The tests showed that beyond a certain airspeed it was no longer possible to modulate rudder travel, as the pedals basically became on-off switches providing either no deflection at all or full deflection. Even the test pilots could not produce a modulated value like 25% rudder deflection at higher airspeeds.

This is not the fault of the pilots, but rather a fault in the design of the rudder travel limiting system on the A310 and A300-600. This is the issue that NTSB wants to address.

[fox niner]

one might reasonably then ask, if the company training program taught the pilot how to improperly apply the rudder

Well 411A, true, true.....But: If a company can teach a pilot a wrong flight technique, it should be possible to unteach him/her. Otherwise I would be very interested in those teaching methods. Sounds like Aldous Huxley's Brave New World brainwash sessions!:}

[deSitter]

Have to agree with Flight Safety here - no airplane should be breakable from control input. Why not put strain gauges in the structure so that rudder max would be controlled by accumulated strain? Could be overridden in a dire emergency I guess..

-drl

[BEagle]

.....no airplane should be breakable from control input.....

You really expect designers to design aeroplanes for total idiots?

I'm with 411A on this issue! What on earth was that company doing, proposing such a stupidly aggressive way of flying the aeroplane?

[Flight Safety]

Beagle, the pilot was not stupidly aggressive. He was taught to use rudder inputs as part of upset recovery (questionable training I know). What he probably didn't know (while doing this) was there was no way to control the amount of rudder deflection he could input. At that airspeed, the rudder travel limiting system provided either full deflection or no deflection. So the "aggressiveness" you mention is part of the design flaw of the rudder travel limiter, not the fault of the pilot. Full rudder deflections just added to the upset, which the pilot continued to try and correct. This is the PIO situation NTSB is trying to address.

What you don't seem to want to accept, is there is a design flaw here the NTSB wants corrected. If this fault were absent, I doubt this accident would have occurred, even with the questionable training. I don't think properly modulated rudder inputs would have overloaded the vertical stab, or added to an upset that seemed (to the pilot) to require additional rudder inputs.

[misd-agin]

Huck,

Spoke with a party to the investigation. He seemed to disagree with the direction the investigation was heading until he got into a full motion sim that could duplicate the lateral loads, etc. :eek: That seat of the pants sensation is completely missing from just looking at the data. He said the control inputs made a lot more sense when you acutally felt similar lateral loads.

[bugg smasher]

The A330 series also has a PTLU fitted as standard.

Is this also a standard feature on the A319/20/21?

[misd-agin]

Fligth Safety - it's not impossible to modulate the rudder throws. It's not just zero or 100%. However, it is very very tough to modulate even after undergoing additional training that was implemented after the accident. Been there done that. However this was in training AFTER learning how sensitive the rudder was. Perhaps a key difference in being able to modulate the rudder travel was the lack of 'real time' pressure/time constraints.

Training included rudder displacements at <165 kts(?), 210, and 250 kts. The change from <165 to 210 kts was "hmmm, ok". The change from 210 kts to 250 kts was "whoa". It's just a different experience at the higher speeds. And the sim couldn't accurately duplicate the side loads being generated which might have changed it to "WHOA!".

I think the rudder travel is 1.3 inches above 250(?) kts. DC-9/S80 is 1.2(?) inches so it's not just the rudder movement that is the problem. It's rudder pedal travel, break out force, force after break out is achieved, degrees of rudder travel per pound of force, etc, etc.

google came up with this -

http://www.alliedpilots.org/Public/topics/issues/apa587finalsubmission.pdf

Seems to me that the A320 incident shows the need for all airline pilots to have training in rudder use at high speeds to understand any limitations their particular a/c might have.

[Flight Safety]

Misd-agin, I agree with all you said. However can you imagine in the adrenalin rush of an upset at 250kts, being able to modulate the rudder on the airplane with the current design? I think not.

[PJ2]

bugg smasher;

Yes, the A319/A320 series is fitted with an RTLU. It is under the authority of the FAC, Flight Augmentation Computers. The AMM states that the limitation remains lower than that which would induce load limits on the structure, throughout the flight envelope.

[grumpyoldgeek]

I don't get it. If a very, very dangerous flight technique can not be trained out of somebody, then that pilot should be grounded. Regardless of the strength of the vertical fin.

The pilot is not completely to blame here. Look carefully at the breakout force issue and compare it to a Boeing. Or compare it to a trainer. Responsive rudder action is required on some aircraft and many trainers. There's also the issue of the Va specification. The aircraft in question was flying below Va, which by definition allows lock-to-lock control throws without breaking the aircraft. After the accident Airbus qualified that to mean one excursion to lock and then back, not multiple cycles. I'd appreciate some input on this issue from the more experienced pilots on the forum.

[misd-agin]

grumpyoldgeek - "The aircraft in question was flying below Va, which by definition allows lock-to-lock control throws without breaking the aircraft. After the accident Airbus qualified that to mean one excursion to lock and then back, not multiple cycles."

I think the problem is line pilots thought Va for light a/c applied to large transport jets. The problem is the engineers or test pilots of transport a/c had different interpretations of what Va meant vs. what the line pilots thought it meant.

Boeing issued clarification also.

[411A]

I think the problem is line pilots thought Va for light a/c applied to large transport jets. The problem is the engineers or test pilots of transport a/c had different interpretations of what Va meant vs. what the line pilots thought it meant.


The problem here is...'thought it meant'.
Versus...what the actual certification criteria are in CAR4B/14CFR25.
If we look back more than thirty years with jet transport training, the trainers then knew damn well what the problems were, and yet...the 'new breed' that came after, did not, and further, would reject any input from older/more experienced guys.
The result?
A large number of dead bodies.
American Airlines (as a company) has a lot to answer for, with their misguided 'upset training' and will pay dearly, in the end.
Airboos, with their poor design, will also pay.

Meanwhile, dead bodies cannot speak from the grave....but their relatives can, through their attornies.
It will take at least 15 years to settle the legal action.

[johns7022]

Why is it every plane certificated has certified speeds that if not exceeded the pilot can penetrate severe turbulence and make abrupt control inputs...

And....

Vmo testing on jets requires Vmo +50kts then an abrupt pull-up to not show ANY structural damage....

Buy if you fly an Airbus...oh my gawd, you better not step on the rudder.....

[misd-agin]

Here's a link to a NTSB powerpoint on the rudder/AAMP issue -

NTSB - AA587 Board Meeting - Operations (http://www.docstoc.com/docs/820340/NTSB---AA587-Board-Meeting---Operations)

If people are really interesting in the accident I'd recommend viewing the NTSB site -

NTSB - American Airlines Flight 587 (http://www.ntsb.gov/events/2001/aa587/default.htm)

I'd recommend the statement by the lead investigator Robert Benzon(Hearing, day 1) as it has the animations, etc -

NTSB - Hearing Agenda (http://www.ntsb.gov/events/2001/aa587/agenda.htm)

[protectthehornet]

so either there is one bad pilot (which I don't believe) or there is one bad plane (type).

I can't recall anyone else shaking a plane apart with rudder movements since WW2, can you? (and not the electra...that was whirl mode).

like the guy said...if you were in a plane and you were flying it and you pumped the rudder back and forth, you would ''feel it'' and know enough to stop.

someday this will happen again and the pilot won't be blamed.

[misd-agin]

411A - The problem here is...'thought it meant'.
Versus...what the actual certification criteria are in CAR4B/14CFR25.
If we look back more than thirty years with jet transport training, the trainers then knew damn well what the problems were, and yet...the 'new breed' that came after, did not, and further, would reject any input from older/more experienced guys.
-----------------------------------------------------------------------

There's only one problem saying the old guys knew it best. Some of us actually grew up with 'old guys' that started out before the jet age started. At least they had to courage, face to face, to admit they didn't know about the rudder issues either. It's the rare guy that said "I knew that". How rare? Except for you I havn't met him.

Who'd this left seat generation have as trainers? The current generation? Uh, no, the 'old guys'. I learned from the guys that started out in the 50's and 60's, ie the dawn of the jet era.(actually a few came from the WWII era). All an observer needs to know about how FOS you are is to actually hear some of the stories from the guys that actually did the transitions from props to jets. Your position "the old guys knew this stuff" looks like swiss cheese after talking with guys that actually started out in the pre jet era. (unfortunately we still have guys relearning some of the same issues when transistioning from straight wing, relatively low altitude and low winging loading, to swept wing, high speed, high altitude and high wing loading a/c).

You remind me of the retired guy talking about how their training as fighter pilots back in the 1960's was the best. Hahaha, he obviously didn't need the advances in training that came about during the following years. Red Flag? Top Gun? John Boyd? P sub S curves? E-M? Waste of money, they could have just asked him.... He had no clue what any of that stuff meant but he had the best training ever....:yuk:

As far as 14CFR25? Oh puleeze. Anyone can read 14cfr25.147, 14cfr25.173, 14cfr25.175 and 14cfr25.177 and as a pilot it means nothing. Yeah, like the guys in the olden days knew what C.G. and force requirements the certification standards required.

[misd-agin]

411A - how does knowing the following section of 14CFR25 assist a pilot ?



Subpart B--Flight

Sec. 25.147 Directional and lateral control.

(a) Directional control; general. It must be possible, with the
wings level, to yaw into the operative engine and to safely make a
reasonably sudden change in heading of up to 15 degrees in the direction
of the critical inoperative engine. This must be shown at 1.4Vs1
for heading changes up to 15 degrees (except that the heading change at
which the rudder pedal force is 150 pounds need not be exceeded), and
with--
(1) The critical engine inoperative and its propeller in the minimum
drag position;
(2) The power required for level flight at 1.4 VS1, but
not more than maximum continuous power;
(3) The most unfavorable center of gravity;
(4) Landing gear retracted;
(5) Flaps in the approach position; and
(6) Maximum landing weight.
(b) Directional control; airplanes with four or more engines.
Airplanes with four or more engines must meet the requirements of
paragraph (a) of this section except that--
(1) The two critical engines must be inoperative with their
propellers (if applicable) in the minimum drag position;
(2) [Reserved]
(3) The flaps must be in the most favorable climb position.
(c) Lateral control; general. It must be possible to make 20 deg.
banked turns, with and against the inoperative engine, from steady
flight at a speed equal to 1.4 VS1, with--
(1) The critical engine inoperative and its propeller (if
applicable) in the minimum drag position;
(2) The remaining engines at maximum continuous power;
(3) The most unfavorable center of gravity;
(4) Landing gear (i) retracted and (ii) extended;
(5) Flaps in the most favorable climb position; and
(6) Maximum takeoff weight.
(d) Lateral control; airplanes with four or more engines. Airplanes
with four or more engines must be able to make 20 deg. banked turns,
with and against the inoperative engines, from steady flight at a speed
equal to 1.4 VS1, with maximum continuous power, and with the
airplane in the configuration prescribed by paragraph (b) of this
section.
(e) Lateral control; all engines operating. With the engines
operating, roll response must allow normal maneuvers (such as recovery
from upsets produced by gusts and the initiation of evasive maneuvers).
There must be enough excess lateral control in sideslips (up to sideslip
angles that might be required in normal operation), to allow a limited
amount of maneuvering and to correct for gusts. Lateral control must be
enough at any speed up to VFC/MFC to provide a
peak roll rate necessary for safety, without excessive control forces or
travel.

[411A]

Except for you I havn't met him.

You haven't looked hard enough.
PanAmerican positively knew the score, as did Boeing...and that is where I received my initial jet transport training, circa 1974.

Missed it, did you?

Sorry, you are totally misinformed.
Certainly...not surprised.:ugh:

[misd-agin]

protectthehornet - the A320 incident shows that the response can trigger man/machine interface problems. 'Startle factor' becomes a dynamic that can lead to increasing control inputs. The a/c responds differently than the pilot expects and that problem is compounded when the pilot enters a PIO and the aircraft responds differently than expected.

It's easy enough to sit at your desk and say "I'd just stop doing that." These two incidents show the potential for man/machine interface problems is real. We've all been startled and responded differently then we would have hoped/expected. Now imagine this happens to you in the aircraft...as the NTSB lead investigator said "some events occur very rapidly, especially near the end of the animation".

The link to the NTSB powerpoint I provided states that the impact of rudder use at high airspeed isn't well known in the industry. Next time you're in the sim try doing fairly abrupt rudder movements at <160 kts, 210 kts, and 250 kts in the simulator. You don't have to be abrupt, just quick. In my experience the difference between 165 and 210 kts was about what I expected. 250 Kts was probably a bigger change than I expected, which is what the whole training was for.

Keep in mind the lateral loads you experience in the sim are less than those you'd experience in the a/c.

The downside might be 5 minutes wasted in the sim. The upside might be priceless.

[misd-agin]

You haven't looked hard enough.
PanAmerican positively knew the score, as did Boeing...and that is where I received my initial jet transport training, circa 1974.

Missed it, did you?

Sorry, you are totally misinformed.
Certainly...not surprised
-----------------------------------------------------------------------

OK, now we're getting somewhere. What exactly did the Pan Am pilot group know, and when did they know it?

As far as your initial jet training, was that Boeing or Pan Am back in 1974?

[Spooky 2]

Pan Am should have known it pretty well by 1974 as they had destroyed enough 707's by then. Nothing like learning the hard way to reinforce the message. :}

[411A]

Pan Am should have known it pretty well by 1974 as they had destroyed enough 707's by then. Nothing like learning the hard way to reinforce the message
True...in fact, more observant than you might expect.

OK, now we're getting somewhere. What exactly did the Pan Am pilot group know, and when did they know it?

As far as your initial jet training, was that Boeing or Pan Am back in 1974?

For the first question, early 1959, the second...early nineteen seventies, both.

One must then wonder...would 'new' jet transport pilots today, think anything about...moving the pole fore and aft, rapidly, to full travel...and expect the horizontal tail to stay attached...at 250 knots?
Why then, I would ask, would these same pilots expect anything different from the rudder/vertical stab?

Answers on a postcard.:rolleyes:

[Pugilistic Animus]

John7022

Why is it every plane certificated has certified speeds that if not exceeded the pilot can penetrate severe turbulence and make abrupt control inputs...

perhaps this helps...http://www.pprune.org/5210206-post30.html

and here's the whole thread
http://www.pprune.org/professional-pilot-training-includes-ground-studies/388963-principles-flight.html

:)

[misd-agin]

411A - One must then wonder...would 'new' jet transport pilots today, think anything about...moving the pole fore and aft, rapidly, to full travel...and expect the horizontal tail to stay attached...at 250 knots?
Why then, I would ask, would these same pilots expect anything different from the rudder/vertical stab?

-----------------------------------------------------------------------

Actually can you imagine the fear/shock/amazement if a transport pilot pulled on the yoke and the a/c responded completely differently than he expected?

Now add in the fact that it's moving even easier than expected. Imagine if that learning curve happened at the same instant and you had seconds to realize it while experiencing aircraft loads you didn't expect. Ugly scenario, isn't it?

You never answered what the Pan Am pilots knew, be it 1959 or 1974.

[Spooky 2]

411, what's your point? Pan Am had a very poor safety record duirng the introduction of the 707 and right up until the mid 70's. Not all of the hull losses could be attributed to crew error or poor training but enough of them continued to happen that the FAA was taking an extremely hard look at the operation. Any other airline other than the mighty Pan Am would have been shut down. Not only did they have the hull losses they also had some serious training events that darn near caused the loss of the airplanes and crews.

I'm sure you recall the Boeing/Braniff accident up in Seattle. This was directly attributed to the Boeing instructor demonstrating the dutch roll characteristics of the new 707 to the initial cadre of Braniff pilots. It wasn't like Boeing did not know about this but the fact that the instructor intentionaly exceeded the parameters previously established for this maneuver.

Neither American, TWA or UAL suffered the line losses that PAA did although they did lose aircraft and flight crew duirng training accidents as I recall. I think AA has a pretty good operation even though I do not know a soul that currently fly's for them. All airlines have periods in their operational history which do not reflect well on them but your constant berating of AA is somewhat perplexing at times.

So you don't think I'm a total slacker I also received my initial type on the 707 at Pan Am in 1967 although my first Capt. trip in the airplane was not until 1971 at Western Airlines.

[p51guy]

Startle factor, now we have something. PTH and I have probably never heard of startle factor. I assume that means something happens you were not expecting and over react. Jumping all over the rudders is not something I would do with startle factor. Maybe my adrenaline would go up but I wouldn't start beating up the airplane because of startle factor. I don't think the AA FO did either. I think the vertical stab separated from the aircraft from the front and the yaw caused a yaw that the gyroscopic forces spit the engines off and the vs finally separated totally. The FDR rudder data was not programmed for a vs coming loose. Notice the final left bank nose down death dive with full right rudder in the video? That was what the FDR recorded probably as the vs was separating. Airbus sold us a faulty airplane with a vs problem. Their attorneys managed to blame it on the FO so Airbus is out of the woods. It worked well for them.

[PantLoad]

With regard to the USAir accident in Pittsburgh where the rudder hardover caused the crash....did not the rudder swing full one direction then the other (on its own due to a malfunction)? If so, why didn't the rudder shear off? Am I wrong, but didn't the rudder bang full displacement one way then the other....and still stay attached all the way to ground impact?

If the answer to the above is 'yes', at what speed did this occur?

Fly safe,

PantLoad

[PJ2]

PantLoad;

The DFDR on USAir 427 recorded only 14 parameters. Rudder position, yaw/yaw rate, pedal position, yaw-damper activity were not among those parameters recorded.

Recorded parameters were:

Time
Pressure Altitude
Airspeed
Mag Heading
Pitch
Roll
Vertical g
Longitudinal g
Captain's control column position
N1
N2
EGT
Fuel Flow
Microphone keying (either one)

PJ2

[protectthehornet]

P51 guy...I have never heard of "startle factor". cute term though. sure not in any books I've read!

talking about the rudder hardover at pittsburg (actually aliqupa). great tragedy. though they did hit wake turbulence and in that there is some similiarity to the american airbus accident.

I flew the 737...and didn't respect it as much the DC9 series. there was a nice handle on the DC9 that would depower the rudder with one easy move, leaving the rudder in manual reversion. turning off the rudder on the 737 is ahandful and leaves you with no manual reversion on the rudder.

and

Pan am may have had lots of crashes ...but they were pioneers...and pioneers teach the rest of us...sadly.

I want to say point blank that until the American accident, I believe that I could move the flight controls anyway I wanted and not cause the plane to fall apart (obeying and respecting placards and the limitations section).

So, we all learned a lesson...but there were better ways to teach it.

I for one, don't blame the copilot...I think the plane is one I wouldn't want to be on , in any capacity.

[Spooky 2]

Pan Am was no more a 707 pioneer than TWA or AA. They were first on the order list but nothing more. The Pan Am accidents were more of an issue of airmanship than anything else. Sorry if that rubs the fur the wrong way.:}

[411A]

.did not the rudder swing full one direction then the other (on its own due to a malfunction)?

No.
The action was a rudder hard-over, very similar in fact to the first rudder hard-over experienced with a jet transport airplane....an American Airlines 707 departing IDL (now JFK).

Pan Am had a very poor safety record duirng the introduction of the 707 and right up until the mid 70's. Not all of the hull losses could be attributed to crew error or poor training but enough of them continued to happen that the FAA was taking an extremely hard look at the operation.
Maybe, however, it must be remembered that PanAmerican operated the first series of B707's, and...if you recall (provided you are old enough to remember, or...flew some of these same airplanes after they had been passed to other operators, as I did) that they were not the best engineered airplanes (considering the present day standards of certification) so...no, it is not surprising that PanAmerican had accidents.

However, AA purchased A300-600R aircraft, then introduced very poorly thought out upset training, using the powered rudder in a totally inapporopriate way...and had a hull loss, with many dead.
IE: it wasn't the airplane (as other airlines had the type, and still do), it was the totally inept upset training scenario that American Airlines developed...that did the deed.
No doubt about it.

[Spooky 2]

Flying into the side of mountains while on approach had nothing to do with airframes. Yea, I'm older and more experienced than you and do remember! :}

[safetypee]

One of the more interesting aspects of the NTSB’s letter is EASA’s response on pilot training (page 4).

It appears that NTSB, FAA, and EASA are agreed on the need for regulation change and the need to review aircraft for compliance (the actual applicability to individual aircraft types remains open), but apparently only EASA has considered the training issue.

The rudder design requirements are sufficient for the static and the single-input dynamic cases, but insufficient for reversals, particularly for a ‘high geared’ designs. Thus the argument for change rests on the aircraft’s susceptibility to a pilot induced oscillation, triggered by an inappropriate response to an external influence (old style human error).
The case against the A300 has been proven and apparently accepted by Airbus. For the A320 and other aircraft, the NTSB makes the strong inference of similarity, but apparently without conclusive proof.

EASA’s reconsideration of their “position on the pilot training-out as being an efficient and sufficient measure to avoid any new hazardous situation … ” and “that crew use of rudder pedal inputs in upset encounters cannot be ‘trained out’ ” points towards a system change as being the only viable solution for a range of aircraft.

Essentially EASA has changed its view of the pilot’s contribution towards safety in situations involving aircraft with deficient systems, where the pilot through erroneous behaviour, contributes to an accident. This is a major advancement in safety thinking, but could have very wide ranging implications.

Consider the MD-80 take-off configuration warning system. A recent accident involved pilot erroneous behaviour and a weak system (modern regulations already require a more reliable configuration warning system). Arguably problems of configuration warning failure have caused more accidents than the rudder problem in turbulence encounters, thus these systems should also be considered as unacceptable.
This line of thought (the change in the assumed capability of the pilot), could question many other aspects of weak designs which continue in service due to ‘grandfather rights’, or even industry lobbying, e.g. contaminated runway operations FAR vs CS 25.

The next move by the regulatory authorities could be interesting, particularly the FAA who appear to ‘believe’ in training as a solution for many safety aspects.

[RatherBeFlying]

P51 GuyStartle factor, now we have something. PTH and I have probably never heard of startle factor. I assume that means something happens you were not expecting and over react. Jumping all over the rudders is not something I would do with startle factor. Maybe my adrenaline would go up but I wouldn't start beating up the airplane because of startle factor. I don't think the AA FO did either. I think the vertical stab separated from the aircraft from the front and the yaw caused a yaw that the gyroscopic forces spit the engines off and the vs finally separated totally. The FDR rudder data was not programmed for a vs coming loose.When I was looking at the photos of the failed fin attachments, I had the same feeling the front attachments may have failed first -- definitely a worse case than initial failure at the rear.

Considering the human response, the PF:
Got a whole bunch more rudder than he wanted
Attempted a correction
Again got a whole bunch more rudder than he wanted -- perhaps augmented by front attachment failure.
There's two full rudder movements easily explained with the second rudder movement in exceedance of then little known certification limits.

I've had two PIO/APC incidents in small a/c known for benign handling. You don't know you're in it until you realise the first correction is an overcorrection. Then you have to gently correct the overcorrection and keep the controls still for a moment. The rudder control system in AA587 did not allow a gentle correction to be made.

[PJ2]

RatherBeFlying;
The rudder control system in AA587 did not allow a gentle correction to be made.
If I may, I would like to ask those reading/contributing: -Other than the AA training program, was there (and is there today) any reason whatsoever to use any rudder at all, ever?

Was this aircraft "upset" or just rolling a bit? I've hit wake turbulence at altitude, (744 1000' above, opposite direction) and it hit us very sharply and hard, (30deg bank approx). I suspect the A340's flight control system used appropriate aileron and that's all.

I'm not second-guessing here, (nor am I saying response should always be left to the AFS, although the NTSB Recommendation did state that, left alone, the Air Canada A320 would have righted itself). - I'm trying to understand the reason for the use of rudder at any time. I understand the reason for the NTSB's Recommendation and agree because of the reasons given, (inability to modulate rudder movement) and I like very much the view expressed by SP above, but still the question lingers...

PJ2

[PantLoad]

411A,

I couldn't remember, with regard to the USAir accident, and, frankly, I'm too lazy to look it up. :> :> :>

In any event, Airbus came out with an "FCOM Bulletin" after the American accident (FCOM Bulletin 828/1, dated June 2004) that discusses the proper and improper use of the rudder. (I happen to have this in my library....no need to research....:> :> :>)

And, you're right with regard to the misuse of the rudder....Airbus explicitly talks about this in the bulletin.

Someone else in this discussion talks about 'feet on the floor'. I respectfully disagree....the rudder is a flight control and should be used as appropriate when appropriate.


Years ago, when I was on the Boeing, I used to fly with a gentleman (F/O) who insisted on keeping his feet on the rudder pedals throughout the flight, especially during takeoff and landing....feet on the pedals with knees locked. It was difficult for me when I was the flying pilot to manipulate the rudder for centerline tracking during takeoff and landing. (Crosswind landings were a XXXXX when flying with this fellow.) His logic was to 'be there' in case of sudden pilot incapacitation. No counselling of mine convinced him otherwise. A run-in with another captain brought the issue before the chief pilot (training department representative present in the meeting, as well), and the problem was resolved right then and there.

Never flew with the fellow again....don't know for sure what happened to him.

I asked him where he learned this nonsense...he told me, "The U.S. Air Force." I doubted it, since I flew with many guys who were U.S. Air Force trained, and none employed this practice. (I am not U.S. Air Force trained.)

Anyway, good discussion. Enjoying it.....

Fly safe,

PantLoad

[Huck]

was there (and is there today) any reason whatsoever to use any rudder at all, ever?

Crosswind takeoffs and landings, and engine failures. That's about it.

[protectthehornet]

don't forget dampening dutch roll in swept wing planes via yaw damper...controlling rudder.

also in correcting adverse aileron yaw.

the rudder is a legit flight control and should be used with skill by excellent pilots.

placing the engines on top of each other in the tail would be one way to not have to worry about engine failure yaw.

crosswind landing gear would take care of that aspect of rudder use

but...oh well. now we know...

rudder saved my life when I lost the ailerons on a light GA aircraft...so keep it there! but at least put something in the book about making the darn thing fall apart in the sky.

[411A]

Crosswind takeoffs and landings, and engine failures. That's about it.
Agreed.
Note that the rudder is automatically used for yaw damping, turn co-ordination (L1011 and others), runway aligment and roll-out (the latter two on many aircraft equipped with an autoland function).
IE: no direct pilot input necessary.

[vapilot2004]

However, AA purchased A300-600R aircraft, then introduced very poorly thought out upset training, using the powered rudder in a totally inapporopriate way...and had a hull loss, with many dead.
IE: it wasn't the airplane (as other airlines had the type, and still do), it was the totally inept upset training scenario that American Airlines developed...that did the deed.
No doubt about it.

One key fact was omitted from the above comment - AA's flight training program for the A300 series aircraft was reviewed and approved by Airbus Industries prior to the airline's implementation. There was no contrary guidance issued regarding AA's upset recovery training from the manufacturer until after the accident.

The deadly tango of flight 587 did indeed require two partners - Airbus and American Airlines. The FO and the A300 were merely the shoes of the dancers.

[PantLoad]

vapilot2004 brings to light a major point....with major airlines in the U.S. (don't know how things work in the rest of the world), everything we do and every way we do it is scrutinized and rubber stamped by the FAA.

Wow, simple, yet brilliant!!!!!!

Thanks vapilot2004!

Fly safe,

PantLoad

[kbrockman]

One key fact was omitted from the above comment - AA's flight training program for the A300 series aircraft was reviewed and approved by Airbus Industries prior to the airline's implementation. There was no contrary guidance issued regarding AA's upset recovery training from the manufacturer until after the accident.

The deadly tango of flight 587 did indeed require two partners - Airbus and American Airlines. The FO and the A300 were merely the shoes of the dancers.

From an old AP press article
A letter dated Aug. 20, 1997, warned American chief pilot Cecil Ewing that rudders should not be moved abruptly to right a jetliner or when a plane is flown at a sharp angle. The letter was signed by representatives from The Boeing Co., the Federal Aviation Administration and Airbus.
Airbus contends that even people within American Airlines were concerned about how the airline was training its pilots. A letter to Airbus dated May 22, 1997, from American technical pilot David Tribout expressed concern about the airline's then-new training course on advanced maneuvers.

"I am very concerned that one aspect of the course is inaccurate and potentially hazardous," Tribout wrote. His concern: Pilots were being taught that the rudder should be used to control a plane's rolling motion

Paul Railsback, American's managing director of flight operations, testified in an April 8, 2003, deposition that he warned airline executives that someone would be killed some day as a result of the training.

[hetfield]

Due to the recalculation of loads for the Multi Role Transporter
and Tanker (MRTT) aircraft, it has been found that a structural
reinforcement at the aft section of the fuselage (FR (frame) 87-
FR91) is required for A300-600 aircraft and A310 aircraft with a
Trim Tank installed.

* * * * * * *
The unsafe condition is the potential loss of structural integrity
in the aft section of the fuselage between FR87 through FR91,
inclusive, during extreme rolling and vertical maneuver combinations.
We are issuing this AD to require actions to correct the unsafe
condition on these products.


govpulse | Airworthiness Directives; Airbus Model A310-304, -322, -324, and -325 Airplanes; and A300 Model B4-601, B4-603, B4-605R, B4-620, B4-622, B4-622R, F4-605R, F4-622R, and C4-605R Variant F Airplanes (Commonly Called Model A300-600 Series Airp (http://govpulse.us/entries/2008/04/14/E8-7665/airworthiness-directives-airbus-model-a310-304-322-324-and-325-airplanes-and-a300-model-b4-601-b4-60)

[kbrockman]

Quickly reviewed it , doesn't really relate to the issues in this thread, also
not a big issue really, just something that needs to be crossed of the todo list.

For the reasons discussed above, I certify this AD:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and

3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility

[Huck]

Paul Railsback, American's managing director of flight operations, testified in an April 8, 2003, deposition that he warned airline executives that someone would be killed some day as a result of the training.

A decade ago good friend and coworker of mine - a standards check airman on the A300/310 - attended this training as AA's guest, as our airline was looking at something similar. His reaction to it was identical to the one described above. We did not adopt the training program.

[PBL]

The letter to which kbrockman refers is at http://www.ntsb.gov/events/2001/aa587/exhibits/239998.pdf

Notice that the signatories specifically warn about events such as occurred 4 years later: "Rudder reversals such as those that might be involved in dynamic maneuvers [sic] created by using too much rudder in a recovery attempt can lead to structural loads that exceed the design strength of the fin and other associated airframe components."

PBL

[protectthehornet]

these rudder problems and warnings prior to the tragedy only indicate to me that AIRBUS and the regulatory agencies of the world, including the FAA, had the moral responsibility to place a placcard on the instrument panel in full view of the crew, warning them about rudder movements and structural failure.

of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.

[kbrockman]

these rudder problems and warnings prior to the tragedy only indicate to me that AIRBUS and the regulatory agencies of the world, including the FAA, had the moral responsibility to place a placcard on the instrument panel in full view of the crew, warning them about rudder movements and structural failure.

of course if this happened and reached the press...NO ONE WOULD book a ticket on this type.

I think you missed the point of all these previous warnings, it was by no means type or manufacturer specific, it was a firm warning from the most important aviation authorities at that time (FAA, Boeing Airbus and MDD) that rudder should not be used, except for some specific exceptions during the flight, contrarary to what AA was propagating at those times in their advanced piloting classes.

What most people keep on focussing on is the lost of the rudder but it wasn't a unique event leading to the crash, there where also the separating engines which is at least indicative of excessive forces put on the entire frame, the extending (weakest) points gave up first , like expected, namely the rudder and the engines.

To be perfectly honest I wouldn't like to be in a repaired airplane (like the rudder was on this frame) in any type from any manufacturer while going to such abuse, changes are that it also will be the last it'll be flying.

Like people said before on this thread, the Copilot also doesn't bear full responsibility for this crash, there is enough blame to spread around, Airbus for what seems to be a halfassed (just within delamination limits) job repairing the rudder and more importantly checking up regulary later on (not unlike what Boeing did to the JAL 747 pressure bulkhead which lead to the fatal crash later), AA for teaching these idiotic recovery techniques, and the FAA fro not reprimanding AA beforehand, they obviously knew about the issue and while they where ultimately the authority that could demand immediate action they failed to do so.


PS sorry for spelling errors, no spell check.

[PBL]

protectthehornet,

it is hard to make any coherent sense out of your view. All aircraft, not just the A300, have been certified to the same requirement of one-full-movement-and-hold. As became evident after the accident, not least through some good work by the late Michael Dornheim, not all pilots and their management were aware of rudder certification requirements and their limitations.

One could hold the view that at least one knows that the A300 fin is good for almost 30% above ultimate load; for other aircraft one knows it not yet.

There is no point putting a placard when all commercial transport aircraft must have it.

One of the main reasons why rudder reversals were not considered in certification is that no one at the time was able to perform reliable calculations of the aerodynamics involved in such oscillatory dynamic manoeuvres. At least at that time no one saw the point in making certification requirements for which no one would be able to provide reliable evidence of assurance (although one could argue that it's now done with SW routinely).

kbrockman,

there is enough blame to spread around, Airbus for what seems to be a halfassed (just within delamination limits) job repairing the rudder

It wasn't the rudder, it was the fin.

Something which fails just short of twice design load, 30% more than ultimate load, doesn't count in my book as a poor repair job. It counts in my book as very robust.

PBL

[kbrockman]

http://upload.wikimedia.org/wikipedia/commons/8/8d/Boeing_B-52_with_no_vertical_stabilizer.jpg

[hetfield]

@kbrockmann

Did that one crash as well?

[kbrockman]

@kbrockmann

Did that one crash as well?

No, neither did the Transat A310 loosing most of its stabilizer BTW.
Interestingly this B52 mishap was during testflight on a special stresstest program, pretty much comfirming that too much rudderuse is not a good idea in flight.

The A300 AA just might have made it if it was in level flight , not loosing its engines also during the whole event (or even maybe with one of the 2 left), they just had too many issues going against them and just didn't make it.

There are ample examples of all kind of airplanes loosing control surfaces during all differnt stages of the flight (most in combat situations, just look at all the examples during WWII bombermissions) , some of them made it , many did not.

If you have just enough control surface left, power is available and you happen to be trimmed correctly at levelled flight , you can survive a lot of structural damage, but if you are in a difficult part of the flight (in a turn at or close to MTOW, during heavy turbulence, low to the ground) it just takes away most of your chances of making it out alive.
AA587 was a prime example of just that.

[bearfoil]

It seems to me there are a couple points left unaddressed. The B-52 was designed Sixty years ago; the picture is instructive in two ways. First, the Vertical Stabilizer failed up to but short of its roots in the fuselage, so that part is straightforward enough, and points to a shortcoming of modern airliners in general, and Airbus in particular, due to demonstrable failures in the VS/Fuse join.

The second point is obvious to anyone old enough to remember when a/c were built in one setting, not farmed out piecemeal to locations around the globe. Structure is addressed as a function of stress on a continuum, and in certificated airframes the stress must be SPREAD such that it cannot become focal and cause failure.

The lugs and brackets solution on the 300 is begging to be noticed, and discussed.
Secondarily, if a system such as the VS/Rudder is to fail, it must not fail at the Fuselage in any way prior to or in concert with Rudder separation.

The Rudder is of course a necessary control, but its utility can be sacrificed and must be, as has been noted in the 447 thread, before the V/S cuts loose: an aircraft cannot be flown with directional stability without a Vertical stabiliser.

The Rudder is a trimming device. Obviously it cannot perform as a control when yaw gets dicey, and certainly not with power that is all or nothing at all. Again, the Rudder must fail (separate) when its aspect is divergent from the Vertical plane such that it transmits load failure to the VS.

Of course the Rudder pulls out the VS forward mount first, the resistance of the Rudder is a lever that pushes the aft vertical spar DOWN and pulls the forward UP. This is the reason for the bottom trailing edge of the Rudder in 447 looking the way it does.

Back to Global modularity. No matter the strength of the join, the Vertical assembly with its uncommon power with its Rudder deflection at some speed will snap any mount proposed (patently). More continuity in the vertical and deeper spread of the fuselage resistance to control forces is demanded. Planting a Tail on an assembled Fuselage is not working.

edit for PJ2

I think it is necessary to think of the VS and the Rudder as separate systems; the Rudder must never be stronger than the VS mount. It is irrelevant to tout the strength of the Rudder here, if it was lost, the VS load would reduce and the VS would not separate. The Rudder caused the loss of the VS, directly. It would be embarrassing to land with a VS only, but not fatal. Wait til dark and send around a company flatbed to retrieve the Rudder.

bear (obviously with hindsight, all due respect)

[PJ2]

411a, PTH, Huck, thank you. I understand the use of rudder but I asked my question for a reason and the point is made in the responses: In fact there are NO circumstances where the rudder would be used as it was here - the rudder on a jet transport is never used in flight, period, except for those cases you describe - crosswinds, turn coordination and yaw damping.

The next question then needs to be asked: Before this accident and prior to awareness of the potential inability to finely modulate rudder response at high speed (Flight_Safety Post #28 (http://www.pprune.org/rumours-news/423360-ntsb-recommendation-re-airbus-rudder-travel-limits-2.html#post5856300)), what reason or evidence, at the time, would any manufacturer have to contemplate that the rudder would be used in this way? As PBL states, any design that fails at 30% above ultimate load, (and the A319 rudder withstood 29% above design limit load) would seem robust enough.

The QRH for the A320 has always been abundantly clear when rudder protections are lost due to various system failures: "Use Rudder With Care".

I think the key point in this is made by safetypee: "EASA’s reconsideration of their “position on the pilot training-out as being an efficient and sufficient measure to avoid any new hazardous situation … ” and “that crew use of rudder pedal inputs in upset encounters cannot be ‘trained out’ ” points towards a system change as being the only viable solution for a range of aircraft.

Essentially EASA has changed its view of the pilot’s contribution towards safety in situations involving aircraft with deficient systems, where the pilot through erroneous behaviour, contributes to an accident. This is a major advancement in safety thinking, but could have very wide ranging implications."

[BOAC]

I have looked briefly at the NTSB stuff, but could someone help here? Has it been positively determined that the fin failed due to human 'cycling' rudder input or was the rudder input an attempt to control the a/c following some sort of fin failure? I have only seen the words 'probable' so far. The wmv shows rudder movement in line with pedal displacement until the supposed 'separation', but is that supposition or confirmed?

[JW411]

For what it is worth, I was always taught to keep my feet on the floor after take off when flying swept wing jet aircraft and only to reunite them with the rudder pedals on approach and landing.

Farting around with rudders was purely for take-off, landing and asymmetric flight only.

As one of my old mentors once put it, a bootfull of rudder could result, at best, in 380 gin and tonics being spilled and, at worst, serious damage which might bite you or the next chap to fly the aeroplane.

Sound advice I feel.

[PBL]

neither did the Transat A310 loosing most of its stabilizer BTW.

Not stabiliser, rudder: ASN Aircraft accident Airbus A310-308ET C-GPAT Varadero (http://aviation-safety.net/database/record.php?id=20050306-0)

PBL

[protectthehornet]

pbl

I am glad that you know all about transport category rudder certification. I guess I don't. Mind you I've taken 7 FAA written exams, gone to FlightSafety twice, been through ground schools at 3 regional airlines and one Major airline and have two type ratings.

nope...not once was I told that moving the rudder would shake the plane apart...never...not in 35 years of flying...until the Airbus/American tragedy.

so, for me, and other people like me who might not know, a placcard is cheap insurance.

Mind you also, that my last two jet transports had rudder limiters so I couldn't pull an airbus!

Mind you if the limiters failed, we had procedures to deal with the situation (including written instructions to limit rudder movement ).

And, as to using the rudder in flight...I've quite smoothly and happily initiated shallow turns in a transport jet using just rudder...it was nice to know how to use the rudder if needed!

[misd-agin]

PTH - the Airbus has a rudder limiter.

What a/c are/were you type rated on? They might have had the same rudder limiter design that the A300/310/320 have.

Anyone know if Airbus changed to the better standard on the A330/340/380?

NTSB concerned about rudder sensitivity on Airbus narrowbodies (http://www.flightglobal.com/articles/2010/08/06/345900/ntsb-concerned-about-rudder-sensitivity-on-airbus-narrowbodies.html)

NTSB believes a variable-ratio rudder travel limiter may provide better protection against high loads from sustained rudder inputs at high speeds than variable-stop systems since variable-ratio systems retain a relatively uniform response throughout the airspeed envelope, and require more physical effort from a pilot to produce cyclic full rudder inputs at high speeds

[PBL]

pth,

yes, with all your experience it would surprise me greatly that you missed all the discussions and information distribution about rudder, certification of and use of, that followed the AA587 accident eight and a half years ago.

If, of course, I were to believe that. Which I don't. I can't see how an experienced professional pilot could be around any kind of discussion forum such as PPRuNe any length of time and have missed it. All of the people on the bluecoat list knew about it as soon as Dornheim broke the story, if not before.

PBL

[protectthehornet]

pbl

I've followed this discussion since the accident...I just didn't know before the accident and I'll bet 90'percent of the pilots here didn't know either.

[Vel Paar]

Hi guys, I know that the AA accident in New York involved aggressive use of rudders; what is your take on pilots who come on with a 15 to 20 degrees crab in a strong crosswind and then suddenly kick it straight at flare? What do you think would be the force even at the slow speed at flare?

[KBPsen]

NTSB believes a variable-ratio rudder travel limiter may provide better protection against high loads from sustained rudder inputs at high speeds

The original Airbus had just such a system.

[411A]

What do you think would be the force even at the slow speed at flare?
Not excessive, in the scenario you describe.

[p51guy]

I have never flown with a pilot that puts their feet on the floor after takeoff. You have three controls, elevator, aileron and rudder. They control pitch, roll and yaw. Why not use the yaw control if it becomes necessary?

[bearfoil]

An Aileron roll in any swept wing jet without some feet would end up pretty interesting.

[Cacophonix]

I am just a light aircraft jockey but occasionally throw a Yak or a Slingsby around and know not to mistreat the rudder and that sturdy but ultimately fragile fin.

How is it that these professional guys were not aware that they could destroy their aircraft by being heavy footed? This is not an Airbus problem!

With respect!

[bearfoil]

If the RTLU is a "protection", AirBus has a duty to anticipate a Pilot trusting it, and perhaps blank out the possibility that a prot. could snarl and bite. The device is a PRTLU without a fully trained crew. But especially when aggressive recovery is trained in?

587 comes a little sharper into focus?

[GlueBall]

I have never flown with a pilot that puts their feet on the floor after takeoff.

Well, then you must have never flown with me. Good.

An Aileron roll in any swept wing jet without some feet would end up pretty interesting.

In 747, "feet" not required during normal [up to 30 deg bank angle] turns.

Rudder required with engine failure, or when landing in cross winds.

[Pugilistic Animus]

it is actually incredibly easy to break an airplane:\

the three least understood phenomena in the pilot community are:

1. The Stall
2. Operating Strength Limitations
3. Airplane performance

I'm NOT being funny or sarcastic in any way:sad:

[bearfoil]

Sorry, meant series of 360degree rolls in a smallish fighter.

[Cacophonix]

it is actually incredibly easy to break an airplanehttp://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wibble.gif

I'd fly aeros any day with you fellah! You are right!

But these guys were being asked not to do that and yet... (training...?)

I don't know and as I said, not a heavy metal man but...

[vapilot2004]

The following is a discussion about AA's well received AAMP - American Airlines Advanced Aircraft Maneuvering Program.

"I am very concerned that one aspect of the course is inaccurate and potentially hazardous," Tribout wrote. His concern: Pilots were being taught that the rudder should be used to control a plane's rolling motion

kbrockman - The only time AA's training program suggested the use of the rudder during unusual attitude recovery was when the ailerons/spoilers were not responsive.

From AA's response:

Use of Rudder

Let me say this one more time, we do not advocate the introduction of large sideslip angles when flying at a high angle of attack. You seem to be predisposed to the belief that we are using rudder first or rudder only. The workbook is not a stand-alone document and nothing should be inferred without listening carefully to the presentation.

In four different sections of the AAMP, emphasis is focused on the fact that when the airplane is not responding to aileron and spoiler control, you should use smooth application of coordinated rudder to obtain the desired roll response. Additionally, let me re-emphasize that AAMP stresses keeping the airplane inside of the flight envelope at all times regardless of attitude. Our pilots are taught to always "respect" the stick shaker.

[PBL]

vapilot2004 (and others),

the AA reply to the FAA/Boeing/Airbus letter did not address the matter of losing structural integrity through use of rudder.

It commented on the possible results of one application of rudder hard-over (referring to Colorado Springs and Pittsburgh 737 upsets), and as far as structure goes that behavior was necessarily covered in certification throughout the flight envelope.

PBL

[hetfield]

I have never flown with a pilot that puts their feet on the floor after takeoff. That's SOP in my (major EU) airline:)

[BOAC]

Anyone able post #83?

[p51guy]

glueball, you remind me of someone who would go down the turnpike in cruise control with their feet crossed because if nothing goes wrong the drive will be uneventfull. An in flight thrust reversal event might catch you totally off guard but hey, it isn't supposed to happen like that. Hope you have an uneventfull future because you don't seem to be prepared to have something out of the ordinary happen.

[p51guy]

hetfield, so with your feet on the floor and the departure requires a 30 degree right bank at 500 feet and at 600 ft you lose the right engine, what do you do? Are you allowed to use the left rudder? Remember your sop says feet on floor. Inquiring minds want to know.

[hetfield]

@p51guy

The term "takeoff" in our SOP means until slats/flaps are retracted, so something around 2.000' AGL.

Hope that helps:ok:

[FullWings]

I think we have to distinguish between V1 cuts, where large and timely rudder deflections may be required to adequately contain the yaw and failures at higher speeds.

If you had the critical engine run down during a close-in turn after takeoff, flying manually, how would you a) recognise the problem and b) deal with the short-term effects? I put forward that unless it was a sim training detail where you were expecting something like this to happen, the first clue would be an increasing tendency to hold off bank, followed by reducing airspeed as the pitch attitude would be too high for the remaining thrust. The initial response of most pilots to a roll deviation is to apply opposite roll control, as 99.999% of the time it is caused by turbulence, wake or otherwise. The first response to a trend of airspeed loss is to lower the nose to a more appropriate attitude.

After a short period of :confused: the amount and duration of the aileron input required would lead most people to feed in rudder to assist, especially if the roll input was a significant proportion of the total available. At that point, there would be enough clues, including engine instruments now showing a problem, that would trigger recognition of engine failure and the appropriate responses and drills.

Point is, it doesn't require violent rudder inputs a split second after the event to stop the aeroplane flipping onto its back. Applying a measured amount of corrective yaw in response to what you have recognised as an unwelcome trend I'd say was a better solution...

Coming back to the central theme of this discussion, I agree with many of the posters that there is no need for significant rudder inputs in jet airliners, outside of low-speed engine failures and crosswinds. The only possible exception that I can think of is if you had reached the limits of control and were heading outside of them, then you could (gently) try the rudder *as a last resort*. At any more than moderate speeds, the primary and secondary effects of rudder input are so powerful that you stand to lose much more than you could possibly gain.

[p51guy]

Take off in this country is when the wheels are on the runway. Once we clear the runway it is called a climb. Hope that helps.

[BOAC]

Once again all this handbag swinging:ugh:

Why not post clearly? My policy is cover until clean.

Next?

Now then, back to #83 - do I take it in view of the lack of clarification here that is is only PROBABLE that the accident occurred due to mishandling of the rudder, so a pre-disposing structural failure remains a possibility?

[FullWings]

Takeoff: "From the application of takeoff power, through rotation and to an altitude of 35 feet above runway elevation."

ICAO link. (http://www.intlaviationstandards.org/Documents/PhaseofFlightDefinitions.pdf)

So I suppose if you levelled off at 30' and flew a circuit, you'd never leave the takeoff phase! ;)

[FullWings]

do I take it in view of the lack of clarification here that is is only PROBABLE that the accident occurred due to mishandling of the rudder, so a pre-disposing structural failure remains a possibility?
Most of the accident reports I've read only go as far as detailing "probable" cause... I don't know whether this is SOP at the NTSB but it seems to be that way for the AAIB. Leaves room for aliens, etc.

[BOAC]

Leaves room for aliens, etc. - presumably your 'etc' includes premature fin failure BEFORE the rudder input (not by aliens), then?

[FullWings]

- presumably your 'etc' includes premature fin failure BEFORE the rudder input (not by aliens), then?
According to the data in the report, the lug failed AFTER the train of alternating rudder inputs: an audible "bang" which correlated with a change in lateral loadings. It failed at near 2x the limit load and well over the ultimate design load, w.r.t. the aerodynamic studies. It appears that the fin failure was anything but premature as it seems to have hung on well beyond what it was manufactured to withstand...

I don't see much in the report (not that I've read every single word) that would lend itself to a 'premature' scenario. To do that you'd have to regard the data and conclusions as false/incorrect, which takes you into conspiracy theory territory.

If there's anything simple to be gleaned from this accident it must be to leave the rudder alone at high speed (240kts/275mph in this case). An unchecked PIO often ends in disaster.

[stepwilk]

"@p51guy

The term "takeoff" in our SOP means until slats/flaps are retracted, so something around 2.000' AGL.

Hope that helps"

Incredible as it may seem, I think we all know what Hetfield means.

[BOAC]

an audible "bang" which correlated with a change in lateral loadings. - well, that's how I see it too, so why 'probable', As you say - it seems to be the way (but not for the RAF....).

[PJ2]

BOAC;
Re #83,The wmv shows rudder movement in line with pedal displacement until the supposed 'separation', but is that supposition or confirmed?
Animations are not strictly investigative tools in the sense that they should be relied upon to determine what happened when. Animations are used to provide situational awareness from which an examination of the actual data can be launched.

The "draw" of animations in a visual, (non-textual) culture such as ours is psychologically very powerful. The format does not invite examination. Rather, for non-specialists especially, the "agenda" of such animations "convinces" rather than "raises questions".

Except for, "because they can", I am not certain of why animations have become part of the "investigative" kit at all. They are helpful in the act of imagining either the airplane or the cockpit indications but there are problems with using animations for detailed examinations such as the kind often suggested regarding the rudder and rudder pedal symbols' motion. I have posted my comments numerous times on these problems in hopes of placing the animation tool in appropriate perspective. Animations may be useful to "place context" but should not be relied upon for detailed information or conclusions.

The reason for this lies in the way flight data is recorded. Very simplistically but importantly, there are two problems: 1) within the one-second recording time frame, dozens if not thousands of parameters are recorded sequentially and not all at once, and, 2) each of these parameters is recorded at an instant in time and most of the time, (the rest of the second), is not recorded. There are exceptions to the "once-per-second" recording - Vertical 'g' is usually recorded 8x per second, etc.

But, stating it differently, most flight data is collected at the rate of one "snapshot" per second. Within a one-second time frame, thousands of parameters sequentially take their place in the dataframe until the beginning of the next second.

These one-second digital snapshots are placed in a dataframe one after the other, so to speak. To re-emphasize, the parameter that may be recorded at the precise beginning of a second, let us say, rudder pedal position, will come slightly before the parameter, let us say, rudder position, which is recorded, in its turn, slightly past the precise beginning of that second, and so on, through thousands of parameters.

But because animations are mathematically smoothed to avoid an inherent jerkiness from digital input which has more periods of "no-data", than not, assumptions are made by the animation software designers about "what happened in the spaces where there is no data", and so data is filled in where there is none.

Think of one stroboscope when observing the motion of just one thing in the dark - while the strobe is lit, we can see what is going on with the control or indication under the strobe-light, but once the light is out, nothing can be determined for sure even though we may be tempted to interpolate "between data points".

Most of the time such interpolation is innocent and usually does not lead to mistakes in understanding what happened.

But in swiftly-occurring events such as a hard landing where examination of both 'g' and flight control surfaces would benefit from a "frame-rate closer to video", we are stuck with interpolation of parameters sampled at only 4x and 8x per second. Thus, when the "strobe is off", we are "in the dark" about where the sidestick was, or what the rate of descent was, in-between samples. The same may be said even more so with parameters which are only sampled once-per-second.

The assumption implicit in a casual reading, (an animation) of the data is that "things happened at the 'same time' ", when in fact they may not have, and incorrect conclusions may be drawn when only looking at an animation. Thus the advice to be cautious when watching an animation of an incident or accident. We just do not know what went into the animation to make it look the way it does. Within such animation programs are dozens of corrections to wind, to magnetic variation, to rates of descent and so on, which are available to the analyst and which, when used with intelligent comprehension of the event achieved through close examination of the actual data, can reflect, within the limits of the technology, what happened. But, despite what the Discovery Channel teaches, animations of incidents or accidents are only rough approximations, and are not videos of what actually occurred.

So, for detailed understandings, I would readily dismiss the animation of AA587 except as a general, situational tool and I would avoid drawing the conclusion about rudder pedals and rudder positions until the actual flight data was examined. We don't even know if the rudder pedal position "parameter" was merely derived from the rudder position, (such derivation is not unusual but is in my view a waste of time and calculating capacity), and not an independent parameter. I have been unable to locate any DFDR readings and none is provided in the NTSB report.

That all said BOAC, in response to your question, I think it is reasonable to conclude that fins don't just come off airplanes without cause. No plausible alternate theory as been posited which places the departure of the fin prior to the rudder inputs.

PJ2

[bearfoil]

PJ2

I can appreciate your description of sampling and animation; in early movie houses, one could hear 24 clicks per second, as each frame "posed" in the lens. The human eye sees 24 "samples" as continuous motion, for electrochemical reasons that are weighty, to say the least. The herky jerky of one second samples is well described in your intimation of "bit rash". At the other end of the camera are high speed cameras in the tens of thousands of eps.

587? The first "bang" was most likely the forward mount of the VS severing itself from the fuselage. I see that happening as the first catastrophic shock load of a Rudder slamming into its stop (30degrees?) puts untenable stress on the joint, a result of the VS lever action forcing the forward lugs "up" and away from the clevis acting in concert with side loads (undesigned for) try to root out the entire assembly.

Is the game up? I think no. The VS is now operating in a sloppy plane as loads cause it to articulate with a broken foremount, and an aft one that has been driven into the fuselage (tail cone), swivelling around a middle joint that is most likely compromised, but still holding. This would express itself in excursions in the lateral, though independently of the Rudder (essentially). Now the cockpit is reacting to a new control: a slow and unpredictable loose VS/Rudder, and response would of course be unpredictable re: pedal inputs. Now might be the time to put foot on the floor, and think about RTB. No pilot would entertain what he is dealing with, it is not trained for. Had it been anticipated by the engineers, a sacrificial hinge may have been installed to prevent the Rudder from overloading the VS.

No. Yaw is atypical, and no one thinks to nurse a wounded bird back to land. The pilot is still trying to "save" the a/c. Instead, he pedals again, against a now fully articulating VS/Rudder assembly, which produces new and surprising results. The Rudder is now ineffective, and who would know the a/c is about to lose the tail? I also believe the Rudder at this point is not the problem. It is what can be described as the "procuring cause". Instead, the VS is flopping around in the 259 knot airstream, until the back and forth has worn out the middle hinge, and the VS flies off to land in the Bay.

The "Finding" must be written by an authority that has many cousins. "Inconclusive" is a favorite word when boxed into a corner by Manufacturers, Old Pilots, Airlines, and politicians. Conclusion? Frangible Rudder or moderated deflection, or "keep your feet on the floor?"

[Mad (Flt) Scientist]

We don't even know if the rudder pedal position "parameter" was merely derived from the rudder position, (such derivation is not unusual but is in my view a waste of time and calculating capacity), and not an independent parameter. I have been unable to locate any DFDR readings and none is provided in the NTSB report.

I agree with the use of an animation as an analytical tool; animations are great for explaining, not so great for initial understanding...

Rev the rudder parameter - footnote 84 on page 49 of the NTSB report indicates that the control positions WERE instrumented, not derived from control surface positions:

During the initial readout of the FDR, the conversion equation for the rudder pedal parameter was found to be incorrect. Thus, the FDR data had to be examined to obtain reference data to establish the proper equation for the rudder pedal position parameter. In addition, revised equations for the control wheel and control column positions were established based on the FDR data. (The airplane was not initially configured with the rudder pedal position, control wheel position, and control column position parameters because they were not mandatory when the airplane was manufactured.) American Airlines added flight control input sensors and the associated hardware to the airplane to comply with 14 CFR 121.344, which required that, no later than August 20, 2001, all transport-category airplanes be equipped with FDRs that record control input positions.

(my emphasis)

I haven't found any plots of that data yet though...

[PJ2]

Mad (Flt) Scientist;

Thanks...given the age of the aircraft, (fairly young, compared with manufacture dates in the '90's, where pretty basic parameter sets obtain - 14 mandated parameters, anyone?), I suspected it would be recorded but didn't assume.

It's curious that the plots aren't available. This was a very high-profile accident where many strong interests were/are to be found. One would have thought, given that most reports include at least some traces, that the data would have been available. Perhaps it is and we haven't located it yet.

PJ2

[BOAC]

Thanks for the comprehensive post. The rudder pedal displacement is clear from the FDR trace. I suppose what I was trying to establish was whether there was any trigger for the pedal action APART from some ingrained training issue following some sort of fin failure ie had something 'gone' that was causing undesired yaw?

For MFS - if I read you correctly, what you seek is on page 6 of the NTSB report under Factual Information.

[PBL]

PJ2, MFS,

The relevant FDR data for AA 587 are contained in various reports by the Airplane Performance group, in the docket. For example, http://www.ntsb.gov/events/2001/aa587/exhibits/242470.pdf
http://www.ntsb.gov/events/2001/aa587/exhibits/283528.pdf
http://www.ntsb.gov/events/2001/aa587/exhibits/306430.pdf

Give them a little time to load. The graphics are heavy on bits.

PBL

[Mad (Flt) Scientist]

Thanks PBL. I'd just tracked down the docket when you posted that.

It's odd that to get to the docket, NTSB seem to make you go through the public hearings rather than straight from the accident database - or maybe I'm doing it wrong.

@BOAC indeed, I'd missed that - expected it in an attachment at the end of the report to be honest. Though just plotting those two control input parameters with no response data is borderline useless. IMHO.

[TyroPicard]

GlueBall
In 747, "feet" not required during normal [up to 30 deg bank angle] turns. I disagree. If you observe a 747 on a close-in SID turn you can see it slipping into the turn. The slip ball shows about half a ball displacement - I always used to squeeze enough rudder to centre it. Yes you need opposite aileron to control the bank angle, but that's what pilots do... Well, a few of us.

JW411
Farting around with rudders was purely for take-off, landing and asymmetric flight only.See above.

[PJ2]

bearfoil;
Conclusion? Frangible Rudder or moderated deflection, or "keep your feet on the floor?"
Just to establish time frames associated with what was available as understanding regarding this issue, (and, to clarify, for sure not as any "boast"), for as long as I can recall, from an early understanding of "feet on the floor", (through talking with a few pilots who trained on the DC8 in the early 60's and who I was fortunate enough to know as a kid), to bearing in mind the side-loads on our little airplanes' vertical stabilizer when doing full spins during initial flight training, (later-60's, Fleet 80 Canuck - tail-dragger), through later learning and training (when I joined a major carrier), I (and most colleagues) knew the rudder was not so much a flight control as part of the vertical stabilizer, which was to be left alone.

Insofar as the "feet on the floor during takeoff/landing" discussion goes, that's nonsense of course. But nor did one "ride the pedals" with feet right up on the pedals (danger of inadvertently applying brakes while controlling rudder in stiff crosswinds, etc), - one kept one's heels on the floor and toes on the pedals for possible engine-failure and directional control either during the reject or the initial rotation and climb-out.

As a group of young pilots starting out with the airline we were trained on the use of the rudder for engine-out and crosswinds only. "Jet Upset" was unknown and so not trained for. However, I've seen/been in Dutch Roll when we turned off the yaw damper at altitude, (not routine!, but turning it off was routine however, on approach in the DC8 40 and 50 series) and it is controllable with aileron, as described in Davies', Handling the Big Jets which I read in 1970 and which reinforced these understandings. I don't know about other places to work, but use of the rudder beyond this understanding was not tolerated; most knew why.

In reference to Flight Safety's excellent post (http://www.pprune.org/rumours-news/422319-lufthansa-cargo-plane-crash-post5849929.html#post5849929), which is well worth reading, I think along with skills-degradation, even a rudimentary understanding of aerodynamics and certification standards is slowly degrading as "things become comfortable and reliable" and NTK - Need to Know, started to make inroads in the mid-80s, perhaps because those running the airline saw automation as making such understandings redundant?

PBL, thank you - I'd visited the Docket but hadn't the time to search thoroughly - much appreciated.

PJ2

[BOAC]

When you look at the failure of AB to warn against 'rudder reversals' following AA903, and read US Read's points at U.S.Read - AA 587 Crash Timeline (http://www.usread.com/flight587/Timeline.html) and his vastly different interpretation of the time-line it is easy to be seduced into Full Wings 'conspiracy theory territory'. Blame the pilot - he's dead?

Who knows?

[bearfoil]

Trombettas is a little agitated, and if what he says has weight, there should be more questions. Fig.37 of the NTSB report shows Lateral moment of Fin (up to and through ultimate Load.) Each occurrence is a tidy match with each of four traces, none of which I think, are actual. They are computed, or there is "Bypass" (AB). As far as the noises, there is a lot of room for opinion. I'm going with thump (Rudder hitting stop) click (?) and BANG. The bang is at the most pronounced Yaw, and I think fits with a (compressor) stall of the Starboard engine. I don't think it is the VS separation, and I don't think it is a bomb.

Starboard because it is in clean air (which separates discretely) and the port side is ingesting turbulent airflow, which serves to mix and homogenize the intake air.

Another possibility is that F/O was trying to counter Yaw with Rudder, but the VS itself was causing the Yaw. If First Rudder deflection uprooted the fore mount and buried the aft, the VS may have ended up looking like an "all-flying" surface, similar to the THS and Elevators. The VS leading edge lodged out of line to the left initially, Pilot inputs Left Rudder. As the VS AoA reaches the point where the remaining structure stops its deflection, the induced slip would allow air behind the leading edge of the VS causing a deflection (a very emphatic, and LOUD one) and the a/c would heave violently back to the left, repeat three times, the VS is finally prised out of its middle mount root.


Until he brings up TWA800, he had me.

Then again, Thump could be the sound of an explosion, filtered through the hold, cargo, and fuselage to the cockpit. When was 587's date with destiny? How soon after the 9/11 deal?

[HarryMann]

Bearfoil: Going back a few of your posts now but I feel you may be falling into a trap with this theory of Rudder forces > Break >Vertical Stabilisers, and think we should iron this crease away once and for all.

I am fairly sure the analysis showed that it's the loads produced by aircraft (thus VS) yaw angle at high EAS, not the direct rudder hinge forces, that broke the VS. The rudder gets you in that situation, but does not per se break the VS through loads transmitted...

Indeed, I might guess that the rudder deflection would be neutral or in an opposite sense when a/c yaw angle reaches maximum, due to out-of phase pumping (howsoever exacerbated by poor control law and force rates)

The Rudder is a trimming device. Obviously it cannot perform as a control when yaw gets dicey, and certainly not with power that is all or nothing at all. Again, the Rudder must fail (separate) when its aspect is divergent from the Vertical plane such that it transmits load failure to the VS.

Of course the Rudder pulls out the VS forward mount first, the resistance of the Rudder is a lever that pushes the aft vertical spar DOWN and pulls the forward UP. This is the reason for the bottom trailing edge of the Rudder in 447 looking the way it does.

Back to Global modularity. No matter the strength of the join, the Vertical assembly with its uncommon power with its Rudder deflection at some speed will snap any mount proposed (patently). More continuity in the vertical and deeper spread of the fuselage resistance to control forces is demanded. Planting a Tail on an assembled Fuselage is not working.

edit for PJ2

I think it is necessary to think of the VS and the Rudder as separate systems; the Rudder must never be stronger than the VS mount. It is irrelevant to tout the strength of the Rudder here, if it was lost, the VS load would reduce and the VS would not separate. The Rudder caused the loss of the VS, directly. It would be embarrassing to land with a VS only, but not fatal. Wait til dark and send around a company flatbed to retrieve the Rudder.

[HarryMann]

PJ2

I am in agreeement with respect to your cautions over 'animations'..

Effectively, the equivalence of 'schematic' comes to mind, in contrast to 'painting or picture'

A subtle warning I think, thanks, an easy trap to fall into
... All that glitters is not gold

[chris weston]

Glisters sir, glisters.

How oft have we heard that told.

CW

[bearfoil]

Harry Mann

In my post #118 I describe the VS separation as Rudder: "procuring cause".

This is an expression that means something starts the ball rolling, then becomes not relevant. It is the enormous pressure of an AoA/VS that does the deed, indeed.
It is possible to construe my statement: The Rudder is the direct cause of the loss....

These two expressions are not exclusive, for me in any case.

I make plenty of errors here to be sure. Allow a defense of the accuracy of this one?

Edit: Geoffrey Chaucer.... "All is not (ne) Golde, that glisteneth"

Thank You Sir.

bear

[BandAide]

American Airlines did not train aggressive rudder techniques, but it did not have or train rudder application limitations.

A good case can be made, and has, that the flying pilot on the JFK flight would not have known his rudder technique would result in structural damage or failure.

Also, full and abrupt application of rudder won't cause the failure, but such rudder reversals will.

[411A]

If you observe a 747 on a close-in SID turn you can see it slipping into the turn. The slip ball shows about half a ball displacement - I always used to squeeze enough rudder to centre it.
The 'ole 707 was exactly the same...a bit of rudder required.
More modern types have rudder applied automatically, the TriStar was the first I believe.

[BandAide]

The Airbus autotrims ailerons, rudder and THS (stab). If you let go it will continue doing exactly what you were doing before you let go, and be nicely trimmed.

[misd-agin]

Bandaide - agreed about the training and that not only did the FO not now but almost the entire pilot corps didn't know the rudder's potential(the whole manuevering speed debate).

However you're wrong about the auto trim issue. The A300 didn't auto trim anything. 1960's design, updated in the 1980's before FBW, etc, etc.

[Machinbird]

I've been looking at the lateral g trace, Figure 3.2.2, from the NTSB report and the estimated rudder position chart, Figure 3.3.1. To me, the whole thing looks like a lateral Pilot Induced Oscillation.

For those who are unsure of the meaning of the term, PIO refers to the pilot being moved in the cockpit by g forces and inadvertently applying control inputs as he is moved around, not deliberate control inputs.
In this case, the pilot flying would be sliding sideways in his seat as the g forces reversed and inadvertently applying rudder input as he attempts to brace his body.
Haven't had an opportunity to read the full NTSB report, but did NTSB address a possibility of PIO?? The Airbus rudder system does not get harder to move as airspeed increases and thus would be rather prone to such a PIO.

[PBL]

did NTSB address a possibility of PIO?

Yes, explicitly. See the Hess Report, http://www.ntsb.gov/events/2001/aa587/exhibits/288388.pdf

BTW, the "proper" term nowadays is Aircraft-Pilot Coupling: Aviation Safety and Pilot Control (http://www.nap.edu/catalog.php?record_id=5469), a fine book. Hess was on the committee who wrote it.

PBL

[BOAC]

For those who are unsure of the meaning of the term, PIO refers to the pilot being moved in the cockpit by g forces and inadvertently applying control inputs as he is moved around, not deliberate control inputs. - I would question that definition. A 'PIO' is any oscillatory instability INDUCED by pilot input, most commonly caused by pilot input applied to dampen a disturbance is applied incorrectly so as to be 'in phase' with the disturbance, thus either worsening or at best maintaining the oscillation. What you describe would be a particular form of 'PIO', not within the general definition.

I'm not sure we have a scientific name for your phenomenon (yet), and I have my doubts that an 'experienced' yaw could cause a rudder input as you describe it.

[HarryMann]

Nevertheles, this is rather naughty...

The Airbus rudder system does not get harder to move as airspeed increases and thus would be rather prone to such a PIO.

This sort of thing was highlighted as long ago as 1949/52 when the first ever jet airliner was being test flown with 'straight' powered controls. The DH Comet fairly soon in its career had a 'Q' pot fitted to simulate increasing stick loads with EAS. I am not abs. sure though whether the rudder was similarly improved.

[barit1]

BOAC:

- I would question that definition. A 'PIO' is any oscillatory instability INDUCED by pilot input, most commonly caused by pilot input applied to dampen a disturbance is applied incorrectly so as to be 'in phase' with the disturbance, thus either worsening or at best maintaining the oscillation. What you describe would be a particular form of 'PIO', not within the general definition.

Another term I've heard used is "Pilot-in-loop" oscillation. It's a servomechanism or control loop in which the pilot is part of the loop. It's difficult to assess or predict when/where this can occur, because the mass and dynamic response of each pilot's arms and legs is different.

And it doesn't matter if the initiating input is voluntary, or turbulence, or whatever. If it's an unstable loop, the oscillation will grow in amplitude.

The correct action is to LET GO of the controls, to break the loop so the oscillation can stop, then drive on.

[BOAC]

Barit - again I do not agree - you are also involving the 'dynamics' of a body in thisthe mass and dynamic response of each pilot's arms and legs. A basic PIO is totally pilot induced, and caused by deliberate control inputs which are incorrectly timed/phased, due either to pilot response, aircraft reaction or control damping. The correct 'cure' is not to 'let go' but to 'freeze' the controls until the PIO dampens (normal stability). You and Machin seem to be describing some sort of event whereby a pilot's body is 'flailing around' and moving the controls (I've met pilots like that:)). I could, I suppose, envisage a situation in severe turbulence where a pilot was flying with one hand on a yoke stick (unlikely!) and thereby being forced to make aileron inputs through the acceleration forces on the arm, but that is an unlikely event. It would be most unlikely in pitch and yaw. Yours is not a classic PIO and more relevantly neither can I see any way in which the yawing motion of 587 could in any way have induced such rudder application.

[Mad (Flt) Scientist]

Such 'g'-induced inputs to the flight controls through accelerations acting on parts of the pilots body would seem to be out of the realm of this accident. Assuming the pilot was properly strapped in etc., the idea that he was under forces so great as to practically lose control of his legs is ... difficult to comprehend. Indeed, such force levels probably themselves would be enough to take the aircraft close to, if not beyond, design loads.

I won't deny that such effects are plausible under the right circumstances - single arm control of a handwheel or control coumn would seem most likely. And I've seen cases where there appeared to be difficulty in the pilot applying precise control in multiple axes due in part to 'g' forces on body components.

But as this was in a high performance jet aircraft conducting rapid rolling testing under high 'g' levels, with a centre column/single arm scenario, and EVEN SO the pilot at no point was rendered unable to control the aircraft (he simply couldn't achieve the perhaps over-ambitious "with no fore/aft stick input" we were trying to achieve) I really can't see that the AA587 scenario gives any scope for such inputs.

Agree 100% with those stating this scenario is in any case not PIO, and certainly not in the classical sense.

edited to add: one classic example of the kind of inadvertent control input being discussed is the carrier catapult launch case, where if hand is kept on the control column to 'g' force on the pilot arm may induce a back stick application which is unintentional. Even the weight of the control column, sans pilot, has to be considered and properly balanced. But, again, these are 'g' levels outside any conceivable large transport aircraft's capability

[bearfoil]

The F-18 requires the pilot's right hand to be grasping the handhold on the forward canopy hoop, and OFF the stick at cat-stroke. Until the boss sees his right fist, there is no launch. The a/c takes itself off, and the pilot assumes control with a pos. climb.

To see a real PIO google F-22 PIO

bear

[misd-agin]

PBL - thanks for posting the link to the Hess Report.

Interesting reading(re-reading?) it.

[mike-wsm]

Could anyone with specific type experience clarify some points, please?
1. At what point would the Yaw Damper have been engaged?
2. Was there an additional Turbulence Damper and was this used?
3. What effect do pilot inputs have on damper performance?
Many thanks!

[Machinbird]

PBL
Thank you for the references. Lets see if this old dog can learn a few new tricks.
I am going to quote a paragraph from one of the references you provided: From the introduction to "Aviation Safety and Pilot Control" ISBN-10: 0-309-05688-8

Aircraft-Pilot Coupling

The committee has adopted APC phraseology for two reasons. The first is to remove the presumption of blame implicit in the term "pilot-induced"; although it is often difficult to pinpoint the cause of specific APC events, a majority of severe APC events result from deficiencies in the design of the aircraft (especially with regard to the FCS) that result in adverse coupling of the pilot with the aircraft. The second reason for referring to APC events instead of PIOs is to expand the focus of the term to include other extreme, unwanted PVS motions that, although not necessarily oscillatory,still derive from inadvertent pilot-vehicle interactions. (Note: PVS=Pilot-Vehicle System).Unfortunately, I'm going to now quote some writers who use the PIO term.

The Hess report (PBL's first link in post #137)(Group Chairman's Factual Report -Addendum Two) concludes pretty conclusively that AA 587 was a PIO (APC) accident:
This report concludes that activity consistent with a lateral-directional pilot-induced oscillation (PIO) was evident in the moments before the crash of AA 587. The lateral-directional PIO was likely accompanied by a similar oscillation in the longitudinal axis. There was a high probability of rate saturation of the aileron and rudder actuators during the oscillations. It has been demonstrated in ground tests that this saturation can create additional time delays in the flight control system and require increased wheel and pedal forces of the pilot, both of which could contribute to the severity and duration of a PIO.
The sensitivity of the rudder/pedal control system of the A300-600 aircraft could constitute a control system characteristic conducive to a PIO. One necessary (but not sufficient) condition for the pedal/rudder sensitivity to serve as such as characteristic would be a demonstration that, in its absence, PIOs do not occur. One such demonstration occurred in AA 587, itself. That is, in the first wake vortex encounter, pedal inputs were minimal and sustained oscillations did not occur.
The Hess report looks at rate limiting of actuators and does not look at forces on the aircrew causing undesired control inputs.


. A basic PIO is totally pilot induced, and caused by deliberate control inputs which are incorrectly timed/phased, due either to pilot response, aircraft reaction or control damping. The correct 'cure' is not to 'let go' but to 'freeze' the controls until the PIO dampens (normal stability). You and Machin seem to be describing some sort of event whereby a pilot's body is 'flailing around' and moving the controls Flailing around is too severe a term although there are situations where that has happened. Everything you do with the controls in a cockpit requires a stable reference. We can compensate for slow, momentary or expected forces on our bodies to a great extent, but if we are dislodged from our "perch" by unexpected motion that changes the distance between us and the controls we manipulate, then we may induce unintended control input. Unfortunately all cockpits are not perfectly designed to avoid unintended control input from aircrew motion. The resulting control motions can either stabilize or destabilize the aircraft.
Only problem with freezing the controls is that in most aircraft there is no good way to do that when you are being bounced around. Perhaps on a Cessna you can grab the column forward of the yoke where it penetrates the panel and stop things from moving in pitch, but on most other aircraft, if you are being moved by accelerations, it is very hard to freeze the controls.
Barit1 is correct, the most positive way to break a positive feedback loop is to release the controls. (But on the Sageburner F-4 PIO accident that act precipitated the final g overshoot.YouTube - F-4 PIO (http://www.youtube.com/watch?v=RhLq4jf_tc4&feature=related)).



HarryMann
Nevertheless, this is rather naughty...The Airbus rudder system does not get harder to move as airspeed increases and thus would be rather prone to such a PIO..
Well Harry, I hope you mean it was naughty of Airbus to design it that way. The bird I used to fly found it prudent to increase rudder force per degree almost 5 fold when accelerating through ~250 knots.
If I understand the Airbus travel limiter properly, the rudder pedal stroke gets shorter as airspeed increases but the speed of rudder response and the force to actuate remain unchanged. The breakout forces change and the gradients change slightly between Airbus models but do not change in-flight.

I am very glad to see that the NTSB and EASA appear to be moving in the direction of a better standard. That some of the existing designs can induce an amplifying oscillation (APC) has already been demonstrated.

[misd-agin]

"I am very glad to see that the NTSB and EASA appear to be moving in the direction of a better standard. That some of the existing designs can induce an amplifying oscillation (APC) has already been demonstrated."


Unfortunately, and to me surprisingly, they didn't come to that conclusion after the AA 587 crash.

[BOAC]

forces on the aircrew causing undesired control inputs - I'm still intrigued by these thoughts - how do you envisage the motion of 587 itself causing the co-pilots legs to push on the pedals - do you see him sliding around in his seat? Why did the first wt encounter not do the same?

587 to me exhibits a simple, classic PIO. The only query I have is why did it start.

Out of interest how did you conclude that the F4 pilot 'let go' of the stick?

[p51guy]

The statute of limitations was probably one reason the rudder problem wasn't addressed until now.

[Machinbird]

BOAC
Out of interest how did you conclude that the F4 pilot 'let go' of the stick?I read the accident report. The PhotoTheodolite footage clearly showed the motion of the stabilator relative to the fuselage. The accident board made the conclusion from that information. Unfortunately the aircraft was trimmed nose up from the turn to align with the course. I should add that the stability augmentation earlier disengaged-in those days it was an electrically held switch that selected it.

[bearfoil]

To me, the correct exit from "oscillation" involves not "letting go", that's counterintuitive and not recommended. The answer is to not "over control", and that is why I think the F22 Raptor youtube is the best example. The F-4 vid looks more like an overloaded wing(s).

The Raptor has (highly) powered controls, far stronger than any human's legs or hand (arm). The (test) pilot was using what he thought were correct inputs, but his powers of observation weren't in tune with elevators that can change pitch 90degrees at 350 knots in a heart beat at 35 tons. He was behind the a/c, and out of control, without a runway to stop his boneheaded stickwork, he would have been dead.

Each change in pitch the jet made, he corrected with WAY too much stabilator.

It was HIS oscillation, no one else's. That's why PILOT induced oscillation. Each one of the accompanying videos on the you tube link has a different explanation, float, bounce, etc.

Aircraft Coupled/Pilot terminology looks like PC newspeak for situations that went by many different names in the past, and doesn't really do the endeavour much good.

Please don't "Let go of the controls".

[PBL]

Each change in pitch the jet made, he corrected with WAY too much stabilator.

How do you know it was the pilot moving the stabilator? Answer: you don't. Further answer: it is obviously the FBW control system moving the stabilator in accordance with (a) what it "thinks" it should do, and (b) pilot inputs.

It was HIS oscillation, no one else's. That's why PILOT induced oscillation.

So you don't think a FBW control system does anything other than mimic pilot control inputs? Astonishing.


Aircraft Coupled/Pilot terminology looks like PC newspeak for situations that went by many different names in the past, and doesn't really do the endeavour much good.

The National Research Council committee thought that such situations had at least as much to do with the design of the control laws as they did with the pilot, and produced the Bode and Nyquist plots to prove it.

But you can look at the stabilator motion and know it was the pilot! What a talent! I wish I had it!

PBL

[Mansfield]

It was HIS oscillation, no one else's.

A statement like this suggests to me that you have never experienced a PIO.

The APC term was developed in the hope of removing the stigma associated with the phrase "pilot-induced oscillation". These have nothing to do with someone's powers of observation being out of phase with the aircraft dynamics. Rather, they are associated with with the control-response feedback loop, which is very much driven by the control system capabilities.

Reference AD 2006-23-15, which addresses the roll PIO issue on the 757. This problem was often initiated by the 757's peculiar ability to dump lift off the upwind outboard flap with a slight crosswind and a slightly raised upwind spoiler. The AD required, among other things, the installation of a roll damper.

Landing on runway 27 at BOS several years ago in an airplane that had not been so modified, I managed to find this little cliff while retarding the power to flare. The resulting PIO that I produced used three roll oscillations and three mainwheel contacts before the FO manually deployed the spoilers and killed the event. We did not damage the airplane, thank goodness, and we were very fortunately on a ferry flight.

Subsequent discussion with the FAA flight test engineer working with Boeing on this problem revealed that during the flight test program executed in search of this issue, a JAA test pilot had also created a PIO following a similar wing drop. The Boeing test pilot in the right seat froze the controls and killed the oscillation.

No doubt this is the correct response. But I have to tell you that, in between main wheel contacts, freezing the controls doesn't immediately cross one's mind. Particularly the rudder, which proved quite useful in keeping the nose pointed down the runway. Of one thing I can be absolutely certain: letting go of the controls was not an option.

The FAA was quite concerned that they had only documented eleven cases of this problem, yet the airplane had been flying for twenty years before the first Boeing Flight Operations Technical Bulletin in 2002. Boeing was concerned enough to mount a fifty odd hour flight test program. But the elephant in the room was obviously that many more of these had taken place...and not been reported.

The authors of Aviation Safety and Pilot Control were attempting to introduce a terminology that would allow such events to be more readily reported and discussed within the community.

The committee has adopted APC phraseology for two reasons. The first is to remove the presumption of blame implicit in the term "pilot-induced"; although it is often difficult to pinpoint the cause of specific APC events, a majority of severe APC events result from deficiencies in the design of the aircraft (especially with regard to the FCS) that result in adverse coupling of the pilot with the aircraft.

Continuing to perpetuate uninformed notions about these events leads to the misinterpretation of the manufacturer's guidance (my case) and, much worse, the under-reporting of them. Read the book, which is quite good, or research PIOs through other venues.

Somehow, we need to move beyond the "everybody else is an idiot except the guys in my class, or airline, or generation..." style of discussion. It does no one any good.

[bearfoil]

Mansfield

Thanks for your reply, I've had more pilot initiated turbulence than I will admit to.

I am not alone, and if my post has offended anyone I have no excuse.

I watched two a/c take off for formation once. One pilot was civilian, the other was a decorated instructor at Top Gun. Their first pass down the runway was odd. The civil pilot was moving along like he was on rails. The Navy guy couldn't maintain his altitude, his distance, or his a/s. He'd start with a slight manouveur, followed by a series of "corrections" that made it worse, until he gathered himself and did fine until his next "small" mistake. I call that PIO. Another instructor noted how she preferred civilian flight to Navy. She said the military teaches "hamhandedness", and the best way to fly is gently. She is a 777Captain.

bear

edit for pth. H---er was flying #2, (Navy)

[protectthehornet]

navy pilots vs civilian...come on...

I'e flown with great military pilots and crappy ones....I've flown with great civilian pilots and crappy ones.

and who was following who in the formation flight?

I flew formation once with another plane...my altitude didn't change according to the altimeter...the other plane LOOKED like it was all over the sky...much more to this sort of thing than meets the eye.

[stepwilk]

"H---er was flying #2 (Navy)..."

Would that be Bob Hoover? He certainly wasn't Navy.

[protectthehornet]

I ask myself and you...if you had to fight a dogfight, would you rather have a 777 captain, or a naval aviator.

But, if you had to land a 777, wouldn't a naval aviator do just fine?

hamhanded indeed.

[bearfoil]

If it was me, I'd trust both dogfight and 777 landing to me, I was passing along the young lady's opinion, not mine

At the time, and after we saw H**er's performance, she made sense.

(Sorry for adding too many empties, stepwilk)

As long as your asking, JR, maybe you can help me get a handle on the debate over
computer v. Pilot. It seems to me that if FBW is what you have, you might be better off with a cadet flying rather than a stick and Rudder type. If it Stalls, you're just screwed, either way, but with Captain Super flying, you'd still crash. Is it that important to have someone to blame? The cadet can blame the fbw, If yer Auto trips out, leaving you blind, thin and confused, it's "The Pilot's Fault", by virtue of your hours.

bear

[stepwilk]

I'm confused. You say you "watched two a/c take off in formation once," and that apparently one was a klutz. Hinker, or Honker, or maybe Humper.

Now you're saying that you're simply "passing along the young lady's opinion" of the two-ship? Is there a post I missed?

[bearfoil]

stepwilk

The lady and I were watching together, she made the "hamhanded" crack.

sorry, and my apologies for misspelling H**er's name.

bear

[Machinbird]

BOAC
- I'm still intrigued by these thoughts - how do you envisage the motion of 587 itself causing the co-pilots legs to push on the pedals - do you see him sliding around in his seat? Why did the first wt encounter not do the same?

587 to me exhibits a simple, classic PIO. The only query I have is why did it start.
Why did it start? First lets look at what Hess said in his report regarding the subject of Triggering events:

Triggering Events
PIO incidents are almost invariably preceeded by a "triggering" event [3]. A trigger is a
stimulus that can cause a pilot to change his/her control behavior. Triggers have been categorized as (a) Environmental Triggers (such as those that involve changes in the vehicle dynamics that cause a mismatch between pilot control strategy and the aircraft dynamics), and (c) System Failures, (such as the failure of an actuator or hydraulic system).

Triggers can cause a pilot to move from non-tracking or low-gain tracking behavior to high-gain tracking behavior. For example, a sudden and large turbulence encounter can cause a pilot to actively begin high-gain, compensatory attitude tracking when previous to the encounter he/she was only monitoring aircraft trim or making low-gain corrections to vehicle attitude.

Of and by itself, a triggering event may not be a catalyst for a PIO. Typically, some flight control system property conducive to a PIO is revealed when high-gain behavior begins. A good example of this is the PIO that occurred in the Shuttle Orbiter Enterprise in October of 1977 (Alt-5). This flight involved the Enterprise being carried aloft on a Boeing 747, then released to make a landing at specific touch-down point on a concrete runway at Edwards AFB (previous landings took place on a dry lake bed). The triggering event here could be described as an Environmental Trigger associated with the stress of attempting what amounted to a spot landing. High gain pilot tracking activity then began that involved large and rapid pilot inputs in the final segment of the approach. The combination of large time delays in the flight control system coupled with the aforementioned control inputs caused the vehicle's elevon actuators to rate saturate or rate limit. This means that the actuators were moving the elevons as rapidly as their designs permit. The intrinsic time delays constituted the control system property conducive to a PIO. The rate saturation dramatically changed the vehicle dynamics by introducing even larger time delays into the control loop. A PIO in both lateral and longitudinal axes ensued. The PIO was terminated when the pilot-in -command released the control stick, i.e. completely "backed out of the loop".

It has been hypothesized that a true PIO will involve the pilot adopting a "regressive" form of tracking behavior marked by the control of error-rate rather than an error itself. For example, if a PIO in the roll-control axis has begun, the pilot will regress to control of roll-rate rather than roll-attitude. Once this regressive behavior has been adopted by the pilot, it is difficult for the pilot to "back out of the loop". A sustained PIO is likely. Often at this point the pilot believes that something is wrong with the aircraft, i.e., that a failure has occurred. As far as the pilot is concerned, the aircraft is behaving strangely. Some pilots who have survived serious PIO encounters have said that they simply "no longer recognized the aircraft".As I mentioned before Hess seems to be looking at AA587 from a control rate limiting perspective, There may be another way to look at the APC forcing function.

But first, a short story about my attempts at driving my brother’s 1967 Pontiac GTO.
I attempted to accelerate the vehicle in a normal manner by letting out the clutch and applying a little accelerator only to be embarrassed by a jerky heel toe type acceleration profile. When this happened a second time immediately afterward, I began to realize that there was more at play than just a clumsy operator.:}
A few experiments revealed that while starting in first gear, the seat back yielded enough to pull me off the clutch and the accelerator together. As I my weight left the clutch pedal the clutch engaged smartly which further increased the acceleration and completed pulling me off the accelerator. But now the deceleration caused by no throttle moved me forward and the throttle was applied again and the clutch disengaged. As long as I attempted to accelerate this jerky charade continued. The fix was simple…Start in second gear.
This is a simple (and I hope easily understood) linear single axis DIO (Driver Induced Oscillation) that resulted from accelerations upon the “crew”. The enabling factor for this oscillation was seat back rigidity incompatible with the accelerations created on the crew member and by a clutch that engaged over a very short pedal travel distance. The initiating event was starting the vehicle in first gear.

I have a few experiments anyone can try in the safety of your own car.
Consider the case of cornering in a vehicle. As long as the turn is in one direction, you settle into whatever support you can find and ride out the turn. If the turn rapidly reverses, you (and your passengers) are now accelerated in the opposite direction. If the forces (speed) is low, friction holds you in place and nothing much happens. With higher forces (speed) your upper body displaces to the opposite side of the seat to find whatever purchase it can and particularly if you are a passenger, you use your legs to help support your body. At still higher turn rates and forces, your posterior slides to the opposite side of the seat until it finds support. The key event as far as your body is concerned is the reversal of force from one direction to another. If this occurs rapidly and unexpectedly it is difficult to steady your body and you use all your appendages to steady yourself.

The following is a generic pilot seat support assessment based on various seats I have ridden in: Your favorite aircraft seat may be different.
Subjective support levels:
1. Good support against positive g events,
2. Fair support against negative g events,
3. Good support against linear acceleration,
4. Fair support against linear deceleration,
5. Fair to poor support on lateral acceleration depending upon whether there are arm rests, location of anchoring straps, and how much the seat width exceeds your actual width.
My expectation is that lateral support in aircrew seats is going to have the worst level of performance.

I suggest you do the car experiment yourself and observe what your turn coping strategies are. The driver in the vehicle has forewarning of the maneuvers and can hold onto the wheel so the best results would be with you as passenger. Observe how you use your legs. Do you use your right leg to brace yourself in a left turn (and vice versa)?
I am going to have to stop at this point. You won’t hurt my feelings if you tell me I am all wet after having run this experiment. I don’t expect 100 % consistent results, but you should be able to see where I am going with this in the context of AA587.

[BOAC]

Machin - I am not disputing your scenario in general - it is the application to 587 I query. Your 'car ' scenario is well known and we have the term 'Kangaroo Petrol' in the UK.

My post " The only query I have is why did it start. " refers to my uncertainty, having looked at the 'conspiracy' theory of 'US Read', as to the actual 'timeline' and what triggered the initial pedal inputs. The FDR trace shows rudder broadly in line with c column, so I do not see your 'physical' motion at play here.

[Mr Optimistic]

If the rudder effect was much more than the pilot expected or knew, the building motion would just have been interpreted as the effects of worsening wake turbulence wouldn't it, ie requiring even more 'corrective action' ? Once the mental picture was set, would there have been any perceptive feedback to alert him that he was a contributor ?

[bearfoil]

Wake turbulence rotates, and for all the "off course" reaction to be in Yaw only is a stretch, something I've not seen addressed, though early on an animation was seen, it required a very specific relationship between the 300's tail (specifically VS) and the rolling vortex from the 747. If the flying pilot bought into wt initially and through the event, wouldn't other controls and thrust settings be in evidence? The author of the USRead piece was more than slightly convinced of his timeline, discounting the wt and drawing attention most emphatically to the call for max power. Something seems awry, just me?

[DozyWannabe]

At an even higher level, it's also worth remembering through this theorising that even the best pilots (and other professions) have off moments - and in the vast majority of cases we end up with little more than bruised pride, and a salient lesson to take more care in future. In this case the PF was an a truly unfortunate nexus of events that yielded tragic results. Whether there was a structural issue or whether it was just a mistake that escalated into a loss of control the results were sadly the same.

The good that has come out of this includes a revision in training practices, along with considerably more attention paid to the ageing properties of composite aircraft materials. It would be a shame to let the negativity and in-fighting overshadow that. This is not the first accident that has split the piloting fraternity in terms of what they believe the fundamental cause is, and it's unlikely to be the last.

Whether the first "hole in the cheese" was a result of First Officer Molin making a mistake, or something technical that precipitated those rudder movements, I'm sure - judging from the personal recollections of those that knew him as a conscientious professional - he'd want the advances in safety and knowledge to be the paramount legacy of the crash.

[Mansfield]

DozyWannabe: It can't be said any better than that.

[p51guy]

Hopefully after 9 years Sten Molin, the FO, is on the first step to being not the cause of the accident but a victim to rudder control engineering faults.

[Ct.Yankee]

p51guy;
I totally agree with you!
It's time to stop blaming a dead pilot!

[p51guy]

. AA 587 had also encured inflight turbulence that injured dozens of passengers 6 years prior and no inspections other than a visual, which we know are not valid now, were done. Airbus probably put pressure on the NTSB to blame the copilot until litigation against them could be erased under the statute of limitations law. I always felt Sten was the fall guy from the beginning. Why did it take 9 years to tell Airbus to fix the rudder system?

[p51guy]

My theory is the vertical stab broke off possibly because of previous damage in 95 and the patch made when manufactured where it broke and caused the severe yaw that separated the engines from the aircraft but they haven't gotten that far yet. Give them another 9 years.

[BandAide]

The thing is, though, the A300 had flown and continued to fly uneventfully with its design rudder system for years.

I was corrected a few pages ago for thinking the A300 had the same autotrim as later Airbi, but the basic principles of rudder application apply regardless. You can't employ rapid, aggressive rudder reversals on big jets, no matter the material compostition of the structure or the manufacturer. The structure won't withstand it. That AA 587's flying pilot didn't know that is basic to the cause of the accident.

Further, a wake turbulence encounter at AA 587's altitude did not require the drastic correction taken. Escape is easily accomplished with an slight upwind turn or altitude level off. Rapid full rudder reversal was not called for, and never is.

Remember Dutch roll on B-707s and DC-8s? The counter was a brief full aileron against the oscillation, neutral controls, then a brief full aileron against the return, opposite direction oscillation. Too much aileron, or any rudder at all accelerated the oscillations. The lesson of the modest control inputs applies to wake turbulence as well.

I think blaming Airbus for faulty design is wrong when the real cause was improper pilot technique, for which I do not fault the pilot as his training curricula overlooked the well known problem of excessive rudder application in opposite direction.

[DozyWannabe]

p51guy, Ct. Yankee:

At this point the evidence is exhausted - there is not and never will be definitive proof one way or the other. "Designed differently from some other manufacturers" is not the same thing as a "design fault". In some cases certain aspects of an airliner's design could be considered non-optimal and require special handling, but that's something that is true of pretty much any airliner you care to name.

I don't think anyone with any degree of self-awareness or compassion would go so far as to out-and-out hold First Officer Molin solely to blame for the accident. Regardless of the controversial issues, contributing factors include inadequate training and insufficient understanding throughout the airline of the important differences between the types they flew and techniques relevant to each. Regardless of whether the rudder design or a mistake was the initiating event, the fact remains that he was spectacularly unlucky in the sequence of events he was given to handle, and there but for the grace of any deity you care to name go many of us.

[EDIT : p51guy - the FDR trace, correllated with the CVR and all other data available at the time, proved beyond any measure of doubt that the vertical stab failed at a level of stress well in excess of its ultimate design load - in layman's terms it outperformed the boffins' expectations - and the failure happened *after* the initial severe upset, not before. Also, Airbus Industrie have no clout whatsoever with the NTSB (and neither for that matter do Boeing or any other manufacturer - see the history of the 737 rudder issue) - it is an independent agency. Airbus couldn't apportion blame even if they wanted to.]

[p51guy]

The MD80 works with trim tabs to control the control surface. What if AA587 lost it's rear lugs on the VS and the rudder was giving opposite commands of yaw. Right rudder, left VS, giving the rudder the function of a control tab? Could you control an airplane on a moments notice using right rudder to yaw left? Just a thought, I have always thought the front lugs failed first which would cause the same crash but in a different way. Rudders alone, I don't think so.

[DozyWannabe]

A separation of that magnitude would have been easily identifiable on the CVR, or at the very least the NTSB would have considered the sequence of events as ambiguous based on what they heard. No such sense of ambiguity made its way into the transcript, so while what youre suggesting is certainly possible, it would be considered extremely unlikely.

[Mansfield]

The Board often behaves in mercurial ways, and, in my opinion, is perfectly capable of going down the wrong rabbit track. That said, they have some of the better metallurgical and structural people in the industry, and, although I have no first hand knowledge of this accident, I would expect their work to be rather solid in this regard.

Regardless of all of this, I will say that based on my intimate experience with Franco-NTSB relations during the Roselawn investigation, the Board is very unlikely to be influenced by French pressure. Indeed, it is far more likely to yield the opposite result.

As far as the certification limits on vertical stab loads, I had no idea prior to this accident that the stab was not structurally designed to handle rapid rudder reversal. Once I read the rule in Part 25, it was painfully obvious...I just never looked at it before, and I certainly never heard it discussed in training with any airline.

This among many other cases has reinforced my belief that a genuine ATP license should require a comprehensive education in both Part 121 and Part 25 rules (and/or the EASA equivalents, depending on your country of issuance), including the means of compliance acceptable to the authorities and the history of accidents and failures that promulgated the rules in the first place.

For example, how many of us realize that the flight director pitch guidance during a go-around is predicated on the engines being spooled to approach power at the initiation of the go-around? The Air Canada crew at Fredericton apparently did not; they followed the pitch guidance promptly, even though the engines had been at flight idle when the go-around was initiated.

We have been fighting this battle with regard to icing certification for years. Many pilots continue, with substantial help from the authorities and the operators, to conflate holdover tables for freezing precipitation with certification to operate in same. Not the case at all. But beyond that, the accident history is laden with cases in which the pilot did not understand the criteria to which either his airplane was certificated, or to which the approach aid was certificated, or to which his ops specs were approved, and so forth.

Perhaps a little less "unencumbered solutioneering" in various training departments, and a bit more thorough exploration of the regulatory criteria and constraints, would go a long way in this regard.

[Slats One]

After reading this thread focus mainly on rudder ratio and related control systems and human inputs, I am now forced to ask:

Are we going to now consider the events of 2005 when an A310 of Air Transat -
flight 961- routing from Cuba to Canada on March 6, 2005, lost its rudder in
flight and experienced Dutch Roll and some flight profile deviations- followed
by a successful landing back at its POD.

I am unaware that anyone blames the pilot flying it, for dubious rudder pedal
inputs - nor is any such suggestion extant. But I am aware that the rudder came
off, and upon subsequent inspection, two of the main fin fuselage- to -fin attachment points had reportedly been damaged and that the fin was left hanging on by less than its normal number of attachment points (3 each side, half alloy, half composite and glue....).

Stress fractures or fluid ingress damage near hinge points were framed as being
the rudder's issues- but few looked at the main empenage's issues....

I believe that this (subsequent to AA 557) incident may relevant in re-evaluating AA587 and Mr Molin’s actions.

Of note:

The Air Transat A310 rudder failed and departed the airframe – leaving only a
few below hinge sections remaining. The reasons for the failure are linked to our lack of
understanding and lack of monitoring knowledge and procedures for the ageing
composite airframe.

‘Tapping’ the fin – as is done on the ramp - and doing a quick ultrasound are not really going to reveal the true state of an ageing composite and the deep layers of its build, cure, bond, resin state and delamination, let alone decide if the current ‘acceptable’ standards for build and resin faults are safe.

There are known existing problems with the manufacture of large scale hot bonded aerospace structures. Several incidents of manufacturing bonding and curing errors took place- leading Airbus to repair/rebuild new build tail fins pre-delivery.

The significant issues are these;

(a) It is hard to inspect or quantify failures in curing (autoclave) and bonding during new build.

(b)Such failures are well known and well documented.

(c) Leading composite researchers have argued for years over the technique of creating a 'peel' during manufacture. Such chemical peel of the composite, can create a non suitable surface on the peeled item once removed - any structure that is then bonded to it can suffer from disbonding etc over time and effects thereof.

So, what are we doing to properly inspect the resin states, lamination, gel
coats, molecule attrition from oil based contaminants and the effects of water / fluid ingress and freezing expansion at high altitudes and low temperatures?

(As an aside -can anyone recall the anecdotes of water allegedly pouring out of Airbus rudders on the ramp after arrival from warmer climes via high level, circa -59 degrees cruise?)

Yet the key reveal of the Air Trasnt A310 event, was the alleged damage to the fin attachment points.

And what are we doing now, all these years later, to address the design and
structural issues that may or may not be apparent in the design of composite rudders and vertical stabs and their crucial attachment point design.

Does the Air Transat event, (and subsequent events with the Air Canada Airbus
fleet subject of a recent statement), have any relevance to the previous incidents?

What other large series production airframe has had such a fin attachment design
and build, and what other airframe suffers fin attachment damage after losing
its rudder and suffering Dutch Roll?

IE: Why did Concorde’s main fin not come off each time part of its composite
rudder failed and broke off in flight – with resulting very severe vibrational harmonics affecting the fin structure? And did you know that the first composite rudder (made by Ciba
Geigy) testing (that is rudder only) was on an RAF VC10 over two years in the early 1970s - a
wonderfully trouble free record over thousands of hours.

What structural differences exist between Airbus tail fin design and strengths
relevant to differing thrust options within each relevant per model type? Answer
? Is it: None?

Why are factory repairs to new cure composite structures allowed? AA587 had such
did it not. And how can adding a strut brace to a composite structure devoid of
a load path carrying chassis, not do anything but expectedly fail at its reinforcement point - that is always going to happen...

Why is the Airbus fin attached with an alloy fitting down one side and a direct
composite fitting down the other- whatever the design loads, whatever the fact
that the AA557 fin failed at beyond its design load, this type of design is
always going to concentrate stress in a small area and at differing resistance
rates - is it not?

Even ff we accept that Mr Molin was using the rudders as evidenced, why do some
blame him solely for that supposed single action - why do we not ask why he was
using the rudders as alleged- was it due just to his own construct, due to the
AA training programme, the rudder ratio issue - or did something happen that was not considered at the time but may, repeat may now be focused by subsequent events - contribute to his actions. Was there a rudder issue not cited then, but apparent now from more recent events? Was there a fin attachment issue? Was there an ageing composite
issue ?

I guess we will never know. But we do now know that the fin is not intended to handle a certain type of rudder action.

Let us remember that in the 1960s a BOAC 707 crashed over Mount Fuji after a
turbulence hit- and the fin failed beyond design limits- just as the AA 587 fin
failed beyond design limits.- so, no, I am not having a 'bash' at Airbus. But
what I am asking is this - does the record of the Airbus fin design, have
a hidden factor only told by the advent of the ageing composite airframe - or
our subsequent knowledge of how to design and build large composite fins- and
crucially, how to keep them attached?

How many more pictures of fins floating in the water - as in AA557, AF 447, and
the NZ 'unexpected turn' Perpignan test flight, will we see?

It has taken years, but are we now at a point where anecdote might indicate a
consistent pattern of evidence?

FYI: I am only asking. The opinions stated above are just that- they are not claims of actuality nor are they evidence. They are just obvious questions after a very long wait.

So shoot me down now why don't you? Someone will....

Meanwhile, what are YOU doing to research the issue of the ageing composite and the legacy of early composite design issues?

Air Transat Ref:
Report Number A05F0047. Transportation Safety Board of Canada(TSB). 2007-11-22.

[safetypee]

Re Machinbird post #161, also Mr O #163, B Aide #171.
It would appear that the accident may not fit classical descriptions of PIOs, but it is probably sufficient for the NTSB’s discussion.
A wider ranging view is that for a deficient system, more often than not, all pilots will suffer a tendency to couple with the system. However, with only a weak system (high geared rudder) the tendency might be ‘trained out’.
There have been few reports of problems with this type of rudder system in normal operations, noting that normal operations may only require occasional and different methods of use; e.g. rudder input with engine failure does not result in a PIO, similar with the landing drift correction.

Thus as an alternative view, if the crew had not experienced the rudder sensitivity during training (experience which provides a datum for future operations), then they could have been surprised by the aircraft’s response when the rudder was used in wake turbulence.
Add to this, the lack of side force (lateral acceleration) in simulators, then the crew could have lacked key elements of the control loop normally provided by training, e.g. damping any tendency to over control during a first flight, or first time driving a new car.

Thus, due to training weaknesses, perhaps accentuated by poor advice of how to react to wake turbulence, the accident crew were actually learning to fly the aircraft in the lateral axis. This may have been more difficult due to the normally tolerable, but relatively high rudder sensitivity.

The view above may reflect some of the EASA’s comments about ‘training’; how much can be assumed about pilot behaviour when operating a system.

In a system involving a man – machine interface, either end, man or machine can be the source of problems (blame) and cures. However, the actual link between the two is very complex; perhaps we should be looking more in this area, and perhaps EASA has made a start.

[DozyWannabe]

How many more pictures of fins floating in the water - as in AA557, AF 447, and the NZ 'unexpected turn' Perpignan test flight, will we see?
I wasn't aware there was a yaw component to the Perpignan test flight - in fact I'd be surprised if there was. We don't know if there was on AF447, but the structural investigation indicates that the vertical stabiliser separated on impact. As I understand it the design of the vertical stabiliser/rudder and it's mountings are completely different across the A300-A320-A33/40 series, so any link there would only be tenuous at best.

It has taken years, but are we now at a point where anecdote might indicate a consistent pattern of evidence?
I'm a cautious enough person to never say never, but my opinion for what it's worth is that it's very unlikely, for the reasons above among others. The famous pictures of the TWA800 wreckage at the surface were not the first parts to separate. The fin in the pictures from the wreckage of the Air India bombing was also not the first to separate. On the other hand, the venerable 737 had been in the air for 24 years before the "perfect storm" of a PCU valve worn in a specific manner combined with extreme low temperatures exposed a design flaw, and it took a non-fatal incident in the wake of two, sadly, fatal accidents before that design flaw was exposed.

The Air Transat incident caused a lot of focus to be put on potential delamination issues, and that focus was compounded by AA587. As a result new inspection procedures are in place and a much more rigorous fatigue monitoring programme has been implemented, as well as all A30/10 training programmes making a point to explain the differences in the rudder system. None of this would have been the case if the accepted version of events simply pinned it on First Officer Molin and left it at that.

I understand the desire to "clear the name" of one of your own, but I don't think there's any name to clear - as I said, it's understood that many pilots put in that position may have acted in the same manner had they had the same training. First Officer Molin was sadly in the wrong place at the wrong time.

[BOAC]

I understand the desire to "clear the name" of one of your own, but I don't think there's any name to clear - as I said, it's understood that many pilots put in that position may have acted in the same manner had they had the same training. First Officer Molin was sadly in the wrong place at the wrong time. - my feelings exactly, but unfortunately there are, as you can see here, those experts who KNOW it was him wot dun it. It is not so much 'clearing the name' as preventing the tarnishing in the first place, I feel?

[DozyWannabe]

I think that says more about the qualities - or lack thereof - of those doing the tarnishing than it does about the one being tarnished.

[protectthehornet]

if one could ''right'' a plane in wake turbulence just using aileron/spoilers and not rudder...one would do that

and if that was insufficient, rudder would be used.

anyone remember the DC9 that couldn't pull out of the wake and was lost?

[glad rag]

Why is the Airbus fin attached with an alloy fitting down one side and a direct
composite fitting down the other-


Where's the HF shunt (antenna) fitted on these aircraft?

[protectthehornet]

and how long is the nelson river bipole?

[DozyWannabe]

anyone remember the DC9 that couldn't pull out of the wake and was lost?

Yes, and the AA training that indicated rudder could be used was based on the DC-9 series - in fact the video of the training session shows the instructor using a DC-9 model to illustrate the technique. That technique did not or should not apply to the A300 series - in fact any large-wide-bodied airliner, because the surface area of the rudder is so much larger. Larger airliners tend to have less severe reactions to wake vortex encounters because their momentum/inertia is so much greater - as such, ailerons should be more than sufficient.

I know one DC-9 was lost on a training flight after encountering the wake vortex of a DC-10, and I think it was either a DC-9 series or a bizjet that was lost in the wake of a 757 - which led to the 757 getting a special classification in ATC separation, because the design of it's wing generated wake vortices considerably larger than those generated by any other aircraft of it's size.

[protectthehornet]

dozzywannabe

the size of the rudder and vertical stabilizer are based more on the need of the rudder to counter an engine out situation...as the DC9/MD80 series has engines close together, there is less need for a big rudder than the traditional underwing mounted engines like on the A300.

so, this makes my case that the DC9/MD80 is a stronger plane than the A300?
;-)

[DozyWannabe]

It's like comparing an articulated semi to a (US) full-sized sedan in terms of the amount of air displacement required to affect it's direction of travel, as well as the amount of air displacement it leaves in its wake.

Also, the smaller a hollow object is, the greater structural rigidity it tends to have, presuming the thickness of the material is roughly equal - that and the difference in the volume of air contained when such a hollow object is pressurised is why data from a decompression event in a narrow-body like a 707 cannot reliably be extrapolated to a widebody like a DC-10 (or an L-1011, or an A300 for that matter) - something the industry found out the hard way in the mid-70s.

The DC-9 is therefore structurally marginally more rigid than a widebody, but the flipside of that is it's relative susceptibility to extreme upset in a wake vortex encounter.

[Graybeard]

Glad Rag: Where's the HF shunt (antenna) fitted on these aircraft?

HF currents causing VS damage was my initial thought on this accident back then. Other HF knowledgable guys have agreed, but we don't have any details from this accident. Neither do we know if HF currents were even addressed in the investigation.

It's in the leading edge of the vertical fin. Transmitting HF generates up to hundreds of amps which must pass through the VS to the fuselage, as the entire airplane is the antenna. The connection must be clean, or heat will be generated. Carbon is a resistive conductor that would heat up if current passed through it.

The antenna spec for the DC-10, the standard of good HF antenna design, is 8 milliohms maximum. Boeing didn't know what it was doing when it put HF shunt antennas in the 767, and it showed in poor performance. I don't know if Airbus was any better.

FWIW, the guy who designed the DC-10 HF antenna was an ex-pat Brit.

GB

[PA-28-180]

"I think it was either a DC-9 series or a bizjet that was lost in the wake of a 757 ".......

It was a bizjet following the 757 that was lost due to wake turbulence....happened in Southern (?) California.

[Piper_Driver]

It was a Westwind biz jet that crashed on approach to John Wayne airport in 1993. the Westwind did have a wake turbulence encounter with a 757 that it was following. The CEO of In-N Out Burgers was killed on the flight.