Posted on 06/27/2009 5:07:40 AM PDT by Erik Latranyi
A Northwest Airlines jet traveling from Hong Kong to Tokyo last Tuesday suffered a series of equipment and computer malfunctions strikingly similar to those encountered by Air France Flight 447 just before it crashed into the Atlantic Ocean on May 31.
The Northwest plane and its passengers, however, emerged unscathed. Details of the harrowing incident described in a memo by one of the Northwest pilots and confirmed Friday by others familiar with the matter highlight how cockpit crews can safely cope with something that is almost never supposed to happen: a system breakdown that prevented the crew from knowing how fast the plane was flying.
During the brief but dramatic event, the Northwest Airbus A330's crew was left without reliable speed measurements for three minutes. In addition, the computer safeguards designed to keep the aircraft from flying dangerously too fast or too slow were also impaired. Like the Air France A330 jetliner, the Northwest plane entered a storm and quickly started showing erroneous and unreliable airspeed readings.
(Excerpt) Read more at online.wsj.com ...
No it didn't. Another pilot may have tried to make it to Teterboro (which they had a visual on). Sullenberger knew from his gliding experience that his Airbus would not make it, leaving the tricky water-landing as the only option.
Yes, it was only a few seconds, but the skills Sully had as a glider pilot paid off.....huge.
Oh I don’t know, one time I was changing a tire and the voice said, “you’re jacked, man.”
Wind makes that impossible in air. The GPS calculates your speed through space just fine, but the air is moving, too, and you must take that into account to get airspeed. On airplanes, they measure the airspeed directly, using pitot tubes. Malfunctioning pitot tubes and/or the computer systems they feed are probably at the root of these incidents.
But Sully did first say he was going to turn around and go back to LaGuardia (clearly impossible) and then subsequently inquired about the Teterboro option (also clearly impossible). With a couple of minutes to think through the available data, and given his gliding knowledge, he certainly could have figured out that both these options were absolute physical impossibilities. But he just didn’t have time to apply the knowledge. I think when he finally realized that the “where” decision was being made for him — probably when he saw the surface of the Hudson right in front of him, right where the runway should be on a normal landing — he instantly concentrated on the landing angle, and that made all the difference between 100% survivors and 100% fatalities. Honestly, before that, I think he was having some of the same trouble the TRACON controller was having, accepting the reality that the only place this plane was going to go down was in the Hudson. If you’d showed him a video of an identical flight, before this incident ever happened, along with all the data that was available to him in the cockpit, I’m sure he could have said within 15-20 seconds of the bird strike that, absent a miraculous engine restart, the only option was the Hudson, and that no time should be wasted thinking about any other option.
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 Staab, 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.
“accepting the reality”
That is always the hard pard - we ALL tend to hang on to what we believe we know, when reality has changed.
*
Airspeed and groundspeed are two different things. GPS won't tell you the former.
Ground speed (as measured by GPS) has little relevance in the air. What matters is how fast air is flowing relative to the airplane body -- also called airspeed. The two could be quite different, especially in stormy/turbulent weather.
Let me take that back. Ground speed will tell you when you will reach your destination. Airspeed is required for flight control.
You throw the GPS out the window, and see how fast it disappears.
Unless you are landing the Airbus with 'wheels-up'.
There is much more forgiveness in landing an aircraft that has a nosewheel and mid-fuselage (or wing) wheels.
Most gliders have only one, or even no wheels, so the landing is very similar to landing on water.
For a stick shift, there is a fixed relation ship between RPM and road speed, as determined by the gear you are in, caused by fixed mechanical linkage from the engine to the transmission to the wheels to the road. There is no such fixed relationship for an aircraft and airspeed.
How does using a tach work as a speedometer when the car is hydroplaning? That's closer to what happens in the air.
I wasn’t trying to indicate a relationship between road speed and airspeed.
I was commenting on the pilot’s reliance on the known speed of the engines and the conditions in which he was flying appeared to make the difference between a value rich event and a crash into the ocean.
There was no comparison made other than the relationship of experience to one’s reactions to an event.
Which is why cutting back on simulator time is Not a Good Thing. Most, but not all, of that training for "anomalies", occurs in a simulator, not a full sized aircraft out over the ocean or desert.
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