747FOCAL,
Both Boeing and Airbus have highlighted concerns about rudder usage in their upset recovery literature, warning that too much rudder could lead to loss of control or even structural failure.
Also IFALPA has published literature regarding rudder usage in their upset recovery literature, for both Boeings and Airbus.
You have had a totally unbalanced campaign relating to this incident, facts are that the aircraft
does meet the FAR 25 design requirements, and the Flight 587 flight data recorder (FDR) shows three lateral accelerations of 0.3g and 0.4g right, and 0.4g left, in the approximately 7 seconds before it appears that the fin came off. Analysis show that the aircraft may have been in a full slip to produce the high accelerations. During the same period the FDR shows the rudder making about five deflections of 5 to 10-11 degrees, culminating in a rudder reversal immediately before the fin apparently came off. The 10-11-degree deflection is the maximum allowed by the A300's rudder limiter at that airspeed, suggesting it was working correctly.
The FARs paragraph 25.351 covers yaw manoeuvre conditions, and 25.341 covers gust and turbulence loads.
Paragraph 25.351 spells out a simple manoeuvre and requires that the manufacturer analyse the loads at four conditions. The manoeuvre is to:
- Fly straight and level, and step on the rudder pedal with a large force (condition A),
- Maintain rudder and let the aircraft swing to a peak sideslip angle that is beyond equilibrium slip due to fuselage momentum (condition B),
- Maintain rudder and let the aircraft swing back to equilibrium sideslip (condition C), and
- Neutralize the rudder while at equilibrium sideslip (condition D).
The rational for these design requirements is that each condition tends to load different parts of the fin, such as the front spar, rear spar, hinges, rudder, etc., but condition D can create the highest fin bending loads, as far as the regulations are concerned.
Ultimate loads as per FAR 25, only needs to be tolerated for 3 seconds (not 7 seconds) and can result in permanent deformation. There is no requirement on what the strength must be after surviving ultimate load.
The A300 rudder is relatively powerful because it is large, about 34% of the total fin chord. Rudder effectiveness also washes out with increasing sideslip, and this affects the critical anti-slip rudder more than pro-slip rudder. The A300 rudder has ±30 degrees of authority at speeds below 165 KIAS, and the limiter progressively cuts this back to 3.5 degrees at maximum speed. It may be tempting to further limit the rudder at higher speeds, but it needs enough authority to handle engine failure with some margin, and serve as a yaw damper. There also are unusual conditions such as multiple leading edge flap failure that may require a large amount of rudder to counteract.
Given the limited amount of FDR data released by the NTSB it is not clear if forces in the rudder exceeded ultimate loads, but the high sideslip and rapid full rudder motions are ripe for this possibility. The exact motions may never be known because the FDR only measured the rudder twice per second, while it can move at 39 deg/s the rudder could go from neutral to the stop and back between samples. And as the NTSB has stated fast rudder motions were distorted by being filtered.
Now as for this article for the manipulation of data by airbus, I have news for you Boeing, and just about every other manufacturer I can think of does the same. Compliance with the FAR 25.351 yaw manoeuvre may be shown analytically, and the airframe manufacturers may not actually conduct a full-force manoeuvre. Why take an aircraft to 100% design load in flight, when you can limit loads to the neighbourhood of 80%, and use this data to validate a model, which combined with ground test results shows the aircraft complies with regulations.
What I see is obvious from this accident, so does IFALPA, so does Boeing and Airbus, is that the design regulations that are set by organisations such as the FAA are the legal requirement for manufactures to meet, a type certificate data sheet issued by the FAA is a licence stating that the manufacturer meets the design requirements as specified the FARs.
If an airline then alledgedly subsequently decides to promulgate an upset recovery technique based upon the senior pilots previous military training, and not in accordance with the what the FAA had allowed for in the FARs, one will never know about this alledged deficiency in the check and training procedures until and accident such as this occurs resulting in a lot of finger pointing. Still some airlines say they know better than IFALPA, Boeing, and Airbus, putting their pilots and passengers into the experimental category.
Bottom line, the aircraft met and exceeded the design requirements as specified in the FARs. If the FARs are not covering all the design requirements that the public demands, don’t blame Airbus or Boeing, blame the FAA.
Like your unbalanced campaign for the A380 upper deck evacuations, Boeing
NEVER conducted upper deck evacuations for the 747 as part of its certification, but have a certified capacity of 660 people, at least Airbus is going to demonstrate it in certification phase.
Obviously this article was written to appeal to Americans of a certain intellect, interesting social experiment to see who runs with it.
IFALPA Safety & Security Bulletins relating to rudder use :
Use of Rudder on Airbus
Use of Rudder on Boeing
Edit: added IFALPA links