Some interesting posts are circulating on the problem.
Best,
Dave
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Some very interesting messages have been directed my way. I thought that I'd share them with you.
First one is from some one unknown to me. Obviously a airline F/O.
The second one is from a NASA DC-8 flight engineer that I have flown with in the past. He confirms that water can exist at -57 degrees C.
First PIREP:
Well, I'm sure you have all heard of the Air France accident. I fly the same plane, the A330.
Yesterday while coming up from Hong Kong to Tokyo, a 1700nm 4hr. flight, we experienced the same problems Air France had while flying thru bad weather.
I have a link to the failures that occurred on AF 447. My list is almost the same.
http://www.eurocockpit.com/images/acars447.php
The problem I suspect is the pitot tubes ice over and you loose your airspeed indication along with the auto pilot, auto throttles and rudder limit protection. The rudder limit protection keeps you from over stressing the rudder at high speed.
Synopsis; Tuesday 23, 2009 10am enroute HKG to NRT. Entering Nara Japan airspace.
FL390 mostly clear with occasional isolated areas of rain, clouds tops about FL410.
Outside air temperature was -50C TAT -21C (your not supposed to get liquid water at these temps). We did.
As we were following other aircraft along our route. We approached a large area of rain below us.
Tilting the weather radar down we could see the heavy rain below, displayed in red. At our altitude the radar indicated green or light precipitation, most likely ice crystals we thought.
Entering the cloud tops we experienced just light to moderate turbulence.
(The winds were around
30kts at altitude.) After about 15 sec. we encountered moderate rain. We thought it odd to have rain streaming up the windshield at this altitude and the sound of the plane getting pelted like an aluminum garage door. It got very warm and humid in the cockpit all of a sudden.
Five seconds later the Captains, First Officers, and standby airspeed indicators rolled back to 60kts. The auto pilot and auto throttles disengaged. The Master Warning and Master Caution flashed, and the sounds of chirps and clicks letting us know these things were happening.
Jerry, the Capt., hand flew the plane on the shortest vector out of the rain. The airspeed indicators briefly came back but failed again. The failure lasted for THREE minutes. We flew the recommended
83%N1 power setting. When the airspeed indicators came back. we were within 5 knots of our desired speed.
Everything returned to normal except for the computer logic controlling the plane. (We were in alternate law for the rest of the flight.)
We had good conditions for the failure; daylight, we were rested, relatively small area, and light turbulence. I think it could have been much worse.
Jerry did a great job fly and staying cool. We did our procedures called dispatch and maintenance on the SAT COM and landed in Narita. That's it.
Second PIREP:
Gentlemen and Ladies,
Some of you heard this before about what we do with the NASA DC-8-72 airplane in reference to the AF accident. We started flying thru and around and in and out hurricanes in 1993. The first thing that happens is you lose both airspeed. And within seconds of each other. Soon after, the outflow valve freezes due to the enormous amount of water the air conditioning systems (PACKS) are UNABLE to sling out via water separators. And that means a run away cabin altitude. Must vacant high altitude to at least 25,000 where things start to return to normal. But how could this be, was the question years ago, to have all this water at 39,000 feet? The science world immediately named this phenomenon: Liquid Cooled Droplets. Yup, even at -57 degrees. There is just too much volume of water in these weather systems for it all to freeze.
But if you really have to do this Suicide For Science flying like we do occasionally at NASA, get an Airborne Battleship. Also known respectfully, as a DC-8.
