FAA Belated Response to AA 587 Accident

[ozaub]

On 12 November 2001, American Airlines Flight 587, an Airbus A300, crashed due to structural failure of vertical stabiliser. On 21 November 2022, FAA published a final rule to prevent a similar failure on future aircraft designs.

See Federal Register :: Yaw Maneuver Conditions-Rudder Reversals (https://www.federalregister.gov/documents/2022/11/22/2022-25291/yaw-maneuver-conditions-rudder-reversals)

Flight Global covered it at FAA finalises rudder protection rule stemming from 2001 American Airlines A300 crash | News | Flight Global (https://www.flightglobal.com/safety/faa-finalises-rudder-protection-rule-stemming-from-2001-american-airlines-a300-crash/151056.article#:~:text=The%20agency%20on%2021%20November%20p ublished%20a%20final,caused%20by%20rapid%20reversals%20of%20 the%20rudder%20pedals%E2%80%9D.) but I haven’t noticed any media commentary on speed of FAA’s response.

Safety may be paramount but it’s clearly not urgent.

[pattern_is_full]

Key Takeaway - the FAA is under the thumb of politicians who may be both for and against certain levels of regulation (and changing every 2-6 years). It has to work with other agencies, both US and foreign. it is not a free agent or dictator who can simply issue a new rule

Time line (mostly from the first document you gave us above)....

2001: Nov 12 - AA 587 rudder loss and crash

2004: Oct 26 - After 3 years of research and investigation, the NTSB determines and issues its report on the probable cause of the accident - https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0404.pdf
Among the findings of that reports are recommendations to the FAA to:

Modify 14 Code of Federal Regulations Part 25 to include a certification standard that will ensure safe handling qualities in the yaw axis throughout the flight envelope, including limits for rudder pedal sensitivity.

2011: FAA tasks the external Aviation Rulemaking Advisory Committee (ARAC) with studying such a rule, and whether there are other ways to solve the problem.

ARAC consists of outside advisors representing various stakeholders: https://www.faa.gov/faq/what-purpose-aviation-rulemaking-advisory-committee-arac

The ARAC delegated that work to its Transport Aircraft and Engine Subcommittee, which further delegated it to its Flight Controls Harmonization Working Group (FCHWG).

2013: The FCHWG and ARAC finish their reports and provide them to the FAA.

2018: FAA issues a public Notice of Proposed Rulemaking on the subject. The manufacturers, and pretty much anyone else with a stake in the rule (and their lawyers) issue comment:

The FAA received comments from the NTSB, Airline Pilots Association, International (ALPA), ATR, Crew Systems, Textron Aviation, Airbus, The Boeing Company, and Bombardier Aerospace. The NTSB, ALPA, ATR, and Crew Systems supported the proposal and did not suggest changes to it. Textron Aviation and Airbus requested that the rule specify a single, full-pedal command followed by one rudder reversal and return to neutral, rather than three rudder reversals as proposed in the NPRM. Those two companies, along with Boeing, also requested other changes, as described in this section of the preamble. Bombardier Aerospace commented on the rule's cost, suggesting that the FAA issue guidance to limit the rule's applicability.

After considering the comments, the FAA reviewed considerations not strictly related to safety, as it is required to by law. Such as Regulatory Flexibility, International Trade Impact, Unfunded Mandates, Paperwork Reduction, International Compatibility, Environmental Analysis. Or by Presidential Executive Orders, such as Protection of Federalism (rights of/effects on the individual States); Regulations that Significantly Affect Energy Supply, Distribution, or Use; and International Cooperation.

2022: FAA, having accounted for all of the above, issues the rule.

So the length of the rulemaking has many fathers and mothers, of which the FAA is mostly low man on the totem pole.

[DaveReidUK]

Also worth noting that the NTSB categorised the Safety Recommendation in question as "Non-urgent".

[gums]

Salute!

Just out of curiosity, how much do the pedals move in the 'bus to command full deflection?

Does the rudder law use any dynamic pressure to limit full deflection or speed/rate of deflection?

As an early user of a FBW system I am simply interested. In our Viper, the rudder pedals moved less than an inch but they moved, whereas the stick did not move it at all until they reconfigured it to move about 1/8 inch. BFD. There was no tactile feedback to provide a clue as to how much rudder or aileron or stab movement/ deflection resulted. Twas all pound/ounces of pressure, and you could trim the gee and do a loop with feet off the pedals and hands off the stick!

Here's the rudder implentation. Very straight forward.


https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/401x529/early_flcs_rudder_crop_0ab3220926ed93c5bee57b213167dd247045b 95e.jpg


Gums asks...,

[safetypee]

gums,

note that the aircraft was not a FBW Airbus, and like other similar aircraft types of the time, depended on pilot training not to make aggressive rudder inputs.

Aircraft certification required structural strength for full deflection, but did not consider fast, limiting, reversals.

The major manufacturers responded quickly after the accident to alert operators to the training issues.

[gums]

Salute!

Thanks for the correction.

Some of we charter members questioned the rudder implementation for the pedals as normally they were moved according to overall pilot command using the stick and had very strong aileron-rudder interconnect as well as anti- spin movement by HAL if you departed.

Gums sends...

[MechEngr]

To revisit - Airbus decided to scale the movement of the rudder pedals with dynamic pressure - the 100% limit was applied at a smaller displacement of the pilot feet thereby preventing the pilot from understanding that change in scale until they hit the variable travel stops.

Under Airbus, it could be that 5% of the full pedal travel could be the 100% allowable per the dynamic pressure.

Boeing let the full allowed travel to be the full allowed travel of the pedals and scaled the motion of the rudder instead. So 100% pedal travel was always 100% allowable per the dynamic pressure.

The discovery process uncovered ten prior in-service events concerning A-300 aircraft,
beginning with an Interflug Airlines event in 1991. In all ten events, the vertical
stabilizers of each Airbus aircraft were exposed to excessive aerodynamic loads—three
even exceeding ultimate load (United States 2003 (Public Hearing Exhibit 7Q). When the
manufacturer observed these highly unusual in- flight events, Airbus should have
investigated the flaws in the design as the limit load is the maximum load expected when
the aircraft is in service.
https://web.archive.org/web/20160304081931/https://legacy.alliedpilots.org/Public/Topics/Issues/apa587finalsubmission.pdf

also

This new system used a Variable Stop Actuator (VSA) which is also found in the
MD-80. The VSA also limited the amount of rudder available to the pilot. The difference
in this system is that the distance which the rudder pedals moved also decreased as the
rudder movement decreased in proportion to speed. A significant flaw in the design failed
to offer the same kind of protection as in the McDonnell design. The MD-80 limits
rudder travel and affords protection in the form of rudder “blow down” should an
operator demand more rudder travel (with resultant excessive load) than the structure can
withstand. These kinds of redundant system designs are common in commercial
aviation—a standard that should be addressed during certification. The Airbus Flight
Crew Operations Manual (FCOM) addresses the rudder system much like any other
manufacturer and, in fact, did not change the language of the FCOM even after changing
the A300 design from the VLA to the VSA system.

[Prober]

MechEngr’s comments stirred my memory. Boeing pedals did move 100% but the rudder movement decreased due to the rudder ratio mechanism. However, many years ago, in the early days of the 757, a slow L HYD leak required the system to be switched off until required for the approach (if stack pipe reserve was intact). For some reason all our aircraft required a great deal of rudder trim in the cruise (later corrected). Having such a leak and following the QRH, the result was an immediate 30 to 40 degree wing down. The aircraft, though, maintained straight and level (altitude but not wings!) flight with us hanging in our straps until the L HYD was quickly switched back on again. This was later shown to have been due to a full and immediate rudder deflection (at M.8). Mr B informed us later that the ratio of rudder deflection reduces with speed by 15 times, from slow to high speed. RUDDER RATIO though, of course, was switched off by selecting L HYD OFF. I believe the QRH was amended to include zeroing the rudder trim before switching off the L HYD. I remember at the time, being surprised that this had escaped being mentioned in the QRH because the excessive trim required on our aircraft was caused, I was told, by a design change requested by our company. Little finger and thumb sometimes do not speak and these things get lost in the fog of history and I have long been out of the game.

Prober

[6packpilot]

Salute!

Just out of curiosity, how much do the pedals move in the 'bus to command full deflection?

Does the rudder law use any dynamic pressure to limit full deflection or speed/rate of deflection?

As an early user of a FBW system I am simply interested. In our Viper, the rudder pedals moved less than an inch but they moved, whereas the stick did not move it at all until they reconfigured it to move about 1/8 inch. BFD. There was no tactile feedback to provide a clue as to how much rudder or aileron or stab movement/ deflection resulted. Twas all pound/ounces of pressure, and you could trim the gee and do a loop with feet off the pedals and hands off the stick!

Here's the rudder implentation. Very straight forward.


Gums asks...,

A300 is not FBW.

no flight control laws

[Fortissimo]

…the excessive trim required on our aircraft was caused, I was told, by a design change requested by our company. Little finger and thumb sometimes do not speak and these things get lost in the fog of history and I have long been out of the game.

Prober

Interesting. I wonder why the Seattle Satan allowed a mod without considering all the pitfalls, and why it didn’t affect other company fleets…

MAX aside, this begs the question of company changes to QRH and normal flows. Manufacturers go to great lengths to establish procedures that work for aircraft X, only for a management pilot to decide his way is better. Unless you are harmonising across fleets from different manufacturers, why is this OK?

[India Four Two]

Gums,

On the Viper, was the +- 15 pound rudder “dead zone” about neutral noticeable in practice?

[gums]

Salute!

First, seems some folks here are describing rudder systems that are not purely move the pedal, rudder moves "x". Move pedal to stop and rudder moves to stop. Ratios and even variable ratios according to "q" are implemented. So THERE ARE "laws" on many systems, just not laws implemented by HAL with little or no tactile feedback. So I shall continue to use the term "laws" for how your plane uses pilot inputs to then move control surfaces.

@India...... The rudder movement was so small that most of us felt it was pressure more than movement. I had the chance to give my bride a taxi ride in the back seat of a family model, including a burner takeoff initiation to about 120 knots. She had no trouble steering the jet down the taxiway with nosewheel steering engaged. Took her maybe two left-right commands and no comment about the "dead zone" plus we didn't go into the grass, heh heh. That was during a fleet grounding when something or other was being fixed and we had to run the things to keep them lubricated and also maybe discover something new to fix. Many of us had done this in the A-7D years before, so no big deal. Was a wonderful few weeks to reward many crew chiefs and others to actually see what we did most every day.

Gums sends...

[RatherBeFlying]

MechEngr’s comments are spot on. ​​​​​​

Not covered was that rudder effect in the A300 vs. pedal movement increased with q² while it was more gently modulated in Boeings where full pedal movement is allowed while rudder travel is decreased according to q by whatever ratio B provided.

Feel systems are important to give feedback to the drivers, but I don't know if feel is provided to the pedals on various types.

[gums]

Salute!

Thank you , Rather. Looks like you learned same as I did as well as many of the old farts on the forum. Our trainers had pure mechanical linkage to the control surfaces, gear/pulley ratios included. If we moved the control to its limits, the control surface moved to it limits. Most had great feedback and you could feel flutter or vibrations or increased force required to move the stick further.

That all changed in the 50's, especially with the new jets that I flew ten years later. As far as feedback, we were concerned about the young pilots checking out in the Viper, as it had zero control feedback. We called those newbies the Atari generation, as Nintendo was not invented yet. And you know what? They did just fine, but I would not have trusted one in a Champ or Cessna 152 at high AoA in in a stall recovery in the base turn.

Gums sends...