PPRuNe Forums - View Single Post - Interesting note about AA Airbus crash in NYC
Old 13th Jan 2007, 05:13
  #211 (permalink)  
aardvark2zz
 
Join Date: Dec 2002
Location: Beverly Hills 90210
Posts: 88
Likes: 0
Received 0 Likes on 0 Posts
Good stuff.
.
Also, note that the rudder mechanism does have the proper speed of the plane. The speed is approx 30 kts less while accelerating.
.
Therefore as the plane was going 250 kts the internal rudder-mechanism speed signal was 220kts due to time filtering.
.
And therefore more deflection was possible than designed for. See reports and slides.
.

Originally Posted by AirRabbit
Well first, it wasn't an "FAA report," it was an NTSB report - second, the simulator is going to do whatever it is programmed to do - nothing more ... nothing less. With proper programming you can make any simulator fly just like the space shuttle. And as you should know, the FAA evaluates simulators to make sure they perform and handle as much like the airplane as can be determined. The data they use for comparison purposes is data gathered during flight testing of the airplane. If you were watching someone in the simulator flailing around on the rudder and the pedal deflections were more than the 1.2 inches described, then I can promise you the airspeed was significantly less than 250 knots and I can promise you that the deflection was more on the order of 4 inches than it was 6 inches. (Sometimes pilots have a problem discerning the difference between those measurements, but that's a debate for another forum!)
No one has said that "the A300 uses 1.2 inches of rudder pedal deflection to produce large rudder response at low climb speed." The accident report specifically describes maximum rudder pedal deflection at 135 KCAS (note-calibrated airspeed) as being 4 inches using 65 pounds of force, and at that maximum pedal deflection, the rudder should be deflected 30 degrees. The same chart (and I'm referring to the chart on page 23 of the report - but, the chart on page 27, cited by RatherbeFlying, is quite eye popping in the relationships it shows!) describes maximum rudder pedal deflection at 250 KCAS as being 1.2 inches using 32 pounds of force (there is a note, stating that this 1.2 inches may change slightly because of the response of the yaw damper), and at that maximum rudder pedal deflection, the rudder should be deflected 9.3 degrees.
So the comparison between the A300-600 and the B-767 (similar sized airplanes) goes like this (same info as supplied by RatherbeFlying, but perhaps a little easier to read:
At 135 knots:
A300-600
breakout force = 22.0 pounds
pedal force at maximum deflection = 65 pounds
pedal travel at maximum deflection = 4.0 inches
rudder deflection at this point = 30.0 degrees
B-767
breakout force = 17.0 pounds
pedal force at maximum deflection = 80 pounds
pedal travel at maximum deflection = 3.6 inches
rudder deflection at this point = 26.0 degrees
At 250 knots
A300-600
pedal force at maximum deflection = 32 pounds
pedal travel at maximum deflection = 1.2 inches
rudder deflection at this point = 9.3 degrees
B-767
pedal force at maximum deflection = 80 pounds
pedal travel at maximum deflection = 3.6 inches
rudder deflection at this point = 8.0 degrees
aardvark2zz is offline