Seems like the severe turbulence/erroneous airspeed indication scenario is not unique to the A330...
the airplane encountered "severe turbulence at high speed" and started to deviate signficantly from assigned altitude. The crew reported later, that their airspeed had become unreliable and requested to divert. During descent the crew reported that airspeed had returned to normal and requested to hold to reduce weight.
While in the hold and descending, the crew was ordered to stop descent at 16000 feet, the crew was however unable to comply and reported the airspeed problems had reoccured.
Francoflier From France, joined Oct 2001, 3195 posts, RR: 10 Reply 3, posted (3 years 11 months 2 days 16 hours ago) and read 14116 times:
Quoting Chuchoteur (Thread starter): Seems like the severe turbulence/erroneous airspeed indication scenario is not unique to the A330...
Nothing new, really, but I guess it bears repeating that very bad weather, severe turbulence and icing will cripple and potentially bring down any airliner, past present and future.
Quoting Chuchoteur (Reply 2): makes you wonder what caused the erroneous airspeeds.
Again, flying through a big thunderstorm, the potential exists for rapid SAT increases associated with sudden severe icing conditions. At the end of the day, and for all the computers/systems installed downstream of it, a pitot tube/static port is just a tiny hole exposed to the elements...
Looks like I picked the wrong week to quit posting...
CX Flyboy From Hong Kong, joined Dec 1999, 6341 posts, RR: 56 Reply 4, posted (3 years 11 months 2 days 16 hours ago) and read 14023 times:
This is not actually a very rare event. It has been put into the spotlight by the Air France accident but in certain storms there is a possibility for any pitot/static system to encounter icing. It is unusual that it results in an accident and we have checklists for unreliable airspeed and indications which point to pitot tube icing.
Ryanair!!! From Singapore, joined Mar 2002, 4652 posts, RR: 27 Reply 5, posted (3 years 11 months 2 days 15 hours ago) and read 13963 times:
Quoting CX Flyboy (Reply 4): This is not actually a very rare event. It has been put into the spotlight by the Air France accident but in certain storms there is a possibility for any pitot/static system to encounter icing. It is unusual that it results in an accident and we have checklists for unreliable airspeed and indications which point to pitot tube icing.
Is this due to the presence of super cooled water droplets at cruising flight levels?
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Kiwiandrew From New Zealand, joined Jun 2005, 8435 posts, RR: 14 Reply 7, posted (3 years 11 months 2 days 14 hours ago) and read 13749 times:
Quoting Qantas787 (Reply 6): Forgive me asking a silly question, but why can't aircraft just use a simple GPS to measure speed accurately from inside the cockpit?
not a silly question - but the reason is quite simple . The flight crew need to know airspeed - ie the speed of the aircraft relative to the air through which it is moving , GPS can only give a groundspeed , ie relative to the whichever part of the earth the aircraft is flying over .
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DxBrian From United States of America, joined Mar 2006, 131 posts, RR: 0 Reply 8, posted (3 years 11 months 2 days 14 hours ago) and read 13696 times:
To keep things short:The GPS can only measure the speed of the aircraft over the ground, while stall speed, max maneuvering speed, max structural speed are all based on speed through the air and factor in the density altitude for more accuracy.
There are different measures for air speed as well, there is Indicated Air Speed which is strictly based on information given to the Air Speed gauge from the pitot tubes. There is Calibrated Air Speed, which corrects for the mechanical differences in the system and True Air Speed which corrects for altitude and temperature.
I'm sure someone out there can offer a lengthier and more technical explanation, but that is the short version.
Aircatalonia From Spain, joined Nov 2007, 532 posts, RR: 0 Reply 9, posted (3 years 11 months 2 days 12 hours ago) and read 13180 times:
Ok this is probably silly as well, but from what I've learned from flight simulator, isn't it NORMAL that the airspeed indicator becomes unstable during turbulence? I'd imagine the more intense the turbulence is the more unstable the indicator becomes...
Flylot From United States of America, joined Dec 2007, 186 posts, RR: 0 Reply 10, posted (3 years 11 months 2 days 11 hours ago) and read 12968 times:
Here is the ATC audio feed. Rather uneventful if you ask me. Not saying I wanted the plane to crash, but like someone said before its not an rare occurrence, so was an emergency landing really necessary? When they checked on the plane, they found nothing wrong. I guess better safe than sorry.
VirginFlyer From New Zealand, joined Sep 2000, 4502 posts, RR: 50 Reply 11, posted (3 years 11 months 2 days 9 hours ago) and read 11344 times:
Quoting Qantas787 (Reply 6): Forgive me asking a silly question, but why can't aircraft just use a simple GPS to measure speed accurately from inside the cockpit?
Quoting Kiwiandrew (Reply 7): not a silly question - but the reason is quite simple . The flight crew need to know airspeed - ie the speed of the aircraft relative to the air through which it is moving , GPS can only give a groundspeed , ie relative to the whichever part of the earth the aircraft is flying over .
see GPS As Pitot Tube Backup? (by Jawed Jun 7 2009 in Tech Ops) although be aware that from about reply 73 onwards it is dedicated to a discussion of some of the finer points of gas dynamics...
V/F
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Decoder From Finland, joined Jun 2005, 71 posts, RR: 0 Reply 13, posted (3 years 11 months 2 days 9 hours ago) and read 10640 times:
Quoting Aircatalonia (Reply 9): isn't it NORMAL that the airspeed indicator becomes unstable during turbulence?
Yes it's normal. Pitot tubes measure airspeed at the location directly in front of the aircraft. If the airspeed they measure is errand, as is the case in turbulence, the instrument will produce errand values regardless of make or model.
For example in gliders doing a simple sideslip will disturb the airflow near the pitot tubes so much that the airspeed indicator becomes essentially useless.
Mm320cap From United States of America, joined Jul 2004, 211 posts, RR: 4 Reply 14, posted (3 years 11 months 2 days 7 hours ago) and read 9270 times:
True erroneous airspeed indications are VERY rare and VERY serious. It's an emergency procedure in any fleet and would absolutely require a divert if not resolved.
The airspeed needle jumps around in turbulence on the 767, but it's not unreliable. It will be within 10-15 knots and that is usually due to windshear effects.
Soon7x7 From United States of America, joined May 2006, 2799 posts, RR: 14 Reply 15, posted (3 years 11 months 1 day 22 hours ago) and read 5910 times:
You stole my wind...while in thermals while flying gliders I'll watch my indicator fluctuate or while under aerotow in turbulent air it will also fluctuate. Crews are just more recently sensative of this as typically they probably never notice it. Kind of like the bird strike rash...all of the sudden everyone is having birdstrikes...j
Mke717spotter From United States of America, joined Dec 2005, 2310 posts, RR: 5 Reply 16, posted (3 years 11 months 1 day 21 hours ago) and read 5597 times:
I flew WAW-ORD today and now I've gotta say that LO pilots must maybe have some kind of a knack for flying into rough turbulence. When we were lining up for takeoff I looked down the runway to see the sky ahead of us pitch black with lightning strikes. We ended up getting tossed around bad on the climbout and it was rough - I hate to imagine how it was for that tiny ATR that went up before us.
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ThirtyEcho From United States of America, joined Dec 2001, 1634 posts, RR: 1 Reply 17, posted (3 years 11 months 1 day 18 hours ago) and read 4932 times:
Quoting Aircatalonia (Reply 9): Ok this is probably silly as well, but from what I've learned from flight simulator, isn't it NORMAL that the airspeed indicator becomes unstable during turbulence?
In a real airplane, it will fluctuate very slightly and return to normal almost instantaneously. The instrument fluctuations, by the way, are a 100% reliable indication of airspeed fluctuations.
I've never played the MSFS game, so I don't know about that.
Flylot From United States of America, joined Dec 2007, 186 posts, RR: 0 Reply 18, posted (3 years 11 months 1 day 12 hours ago) and read 4546 times:
Quoting Aircatalonia (Reply 9): Ok this is probably silly as well, but from what I've learned from flight simulator, isn't it NORMAL that the airspeed indicator becomes unstable during turbulence?
Quoting ThirtyEcho (Reply 17):
I've never played the MSFS game, so I don't know about that.
This is where I first discovered faults with airspeed indicators. Thinking it was a glitch in the game, I red up on it and discovered it was a real life occurrence.
WROORD From United States of America, joined Mar 2009, 811 posts, RR: 0 Reply 19, posted (3 years 11 months 1 day 2 hours ago) and read 4191 times:
The same aircraft LPA had an emergency landing in GDA today according to Polish aviation site www.pasazer.com. The aircraft was flying from KRK to ORD and supposedly landed in GDA to get extra fuel??? I think there must be some issue with this machine.
Ikramerica From United States of America, joined May 2005, 21029 posts, RR: 60 Reply 20, posted (3 years 11 months 1 day 2 hours ago) and read 4170 times:
could a RAT be used to measure airspeed? maybe not located where they are currently on some aircraft, but located in a different location, can't the same mechanism that acts as a RAT be calibrated to measure it's rotational speed, thus airspeed, like a ground based sensor? the reason I ask is only as a failsafe backup for pitot icing...
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Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 21, posted (3 years 11 months 1 day 1 hour ago) and read 4152 times:
Quoting Ikramerica (Reply 20): could a RAT be used to measure airspeed? maybe not located where they are currently on some aircraft, but located in a different location, can't the same mechanism that acts as a RAT be calibrated to measure it's rotational speed, thus airspeed, like a ground based sensor? the reason I ask is only as a failsafe backup for pitot icing...
It's technically possible, but you need to be able to back out the load on the RAT, both hydraulic and electric, and measure the density, in order to get from RAT RPM to airspeed. I'm not sure you can do that accurately enough, with a practical system, to make a good enough airspeed sensor. Especially since, if you've got pitot icing, you'll probably get RAT icing too.
Konrad From United States of America, joined Mar 2002, 494 posts, RR: 0 Reply 22, posted (3 years 11 months 23 hours ago) and read 3979 times:
Quoting WROORD (Reply 19): The same aircraft LPA had an emergency landing in GDA today according to Polish aviation site www.pasazer.com. The aircraft was flying from KRK to ORD and supposedly landed in GDA to get extra fuel??? I think there must be some issue with this machine.
Not an emergency landing just a technical stop for fuel.
KRK runway is 2550m only, not enough for a 763 fully loaded for the KRK ORD westbound trip in summer. GDN is few hundred miles closer and has a 3000m runway or so. This happens a few times every summer when the loads are 100%.
Brons2 From United States of America, joined Sep 2001, 2969 posts, RR: 5 Reply 23, posted (3 years 10 months 4 weeks 1 day 18 hours ago) and read 3389 times:
Quoting Decoder (Reply 13): For example in gliders doing a simple sideslip will disturb the airflow near the pitot tubes so much that the airspeed indicator becomes essentially useless.
Also in aerobatics the airspeed indicator doesn't seem to be terribly useful. The first time I was a passenger in a 2 seat plane doing figure 8's with pretty close to 90 degree wing bank and I looked down and saw the indicated airspeed was 40 knots, I almost fainted. The pilot flying told me to stop looking at the airspeed indicator. So then when he did some barrel rolls I closed my eyes. That made him mad too. lol.
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Mke717spotter From United States of America, joined Dec 2005, 2310 posts, RR: 5 Reply 24, posted (3 years 10 months 4 weeks 8 hours ago) and read 3021 times:
Looks like another issue for one of LO's 767s:
A LOT Polish Airlines Boeing 767-300, registration SP-LPF performing flight LO-26 from Warsaw (Poland) to New York JFK,NY (USA), was already overhead the Baltic Sea more than an hour into the flight, when the crew decided to return to Warsaw due to the failure of the autopilot. The airplane dumped fuel and landed routinely and safely in Warsaw about 3 hours after departure.
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We ended up getting tossed around bad on the climbout and it was rough - I hate to imagine how it was for that tiny ATR that went up before us.
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