PPRuNe Forums - View Single Post - AF 447 Thread No. 6
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Old 28th Aug 2011, 22:13
  #567 (permalink)  
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Join Date: Jun 2009
Location: florida
Age: 81
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Body rates

No problem, Clandestino.

I have been having a problem expressing myself lately.

Still want folks to know that the human "body rates" can help for the first second when something unusual happens. Also, you cannot depend upon gauges when you have to make very quick control inputs flying a few feet on the wing of your leader. Besides, you can't do much except take an occasional glance at the HUD or ADI to let you know you have not been in a sustained bank or whatever.

The HUD's I flew quit showing the aircraft vector once weight-on-wheels switch was activated. I agree that the speed indication is very important once you know/feel that you are slowing down. But I never needed to look at the speed "thermometer" in the first second I tapped the brakes on an icy runway. Most of my early birds did not have an "inertial" groundspeed indication, and the pneumatic pitot reading went to zero around 40 knots.

Same observation as far as skid is concerned. I'll take my butt for the first half a second, then depend upon my eyeballs to keep tracking down the centerline. And BTW, when I landed the Viper with that leading edge flap up, the flight path marker was almost useless ( I musta had 15 degrees of yaw), so I flew the ILS gauges even tho I broke outta the overcast about 1200 or so feet AGL. I simply tracked my butt down the centerline until "impact", heh heh. Next guy to try it almost pranged, as I had not yet briefed all the pilots on the 'technique". Additionally, the preferred technique ( actually "mandatory") was to land in a crab when crosswinds were high. The aileron-rudder interconnect cut out with weight-on-wheels, so trying to land "wing low" in a slip resulted in a huge yaw moment upon touchdown. Not good, to say the least, and another instructor tried it one day when messing around.

My view of the 'bus rudder is not that the FBW system has a "spin resistance" feature as we had in the Viper once our AoA was above 30 degrees. Seems to me that the basic yaw damper function and a great directional stability that is inherent in the jet's design did the trick. i would also postulate that spoilers could have compensated for adverse yaw once the crew got into uncharted territory.

I agree that the true "upset" was not loss of the pitot system or A/P disconnect. We are in the same "zone" in that regard.

The stall warning that seems to be audible in the cockpit of AF447 still puzzles me. I am not sure if the crew ignored it due to the unreliable airspeed or what. A mystery to me as well as many here.

Finally, I am overjoyed that commercial jets are finally getting good HUD's. The Shuttle didn't get one until just before Challenger, or even about the same time. My 'nam roomie was the lead astronaut for the Shuttle's HUD, and had to overcome some resistance from Crippen, Young and others of the "old guard". I was a techno-geek, and used the HUD more than most in the old days. The "inertial" vertical velocity" was especially handy, and later HUD's had inertial ground speed. Still had an easy cross-check with the steam gauges, plus the AoA indexers on each side of the HUD ( ask 'bird and RF4 and others that flew Navy jets).
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