Nothing conclusive yet from the NTSB over the Air France 447 disaster, but they did put out an interesting press release yesterday:
The National Transportation Safety Board is investigating two recent incidents in which airspeed and altitude indications in the cockpits of Airbus A-330 aircraft may have malfunctioned.
The first incident occurred May 21, 2009, when TAM Airlines flight 8091 (Brazilian registration PT-MVB) flying from Miami, Florida to Sao Paulo, Brazil, experienced a loss of primary speed and altitude information while in cruise flight. Initial reports indicate that the flight crew noted an abrupt drop in indicated outside air temperature, followed by the loss of the Air Data Reference System and disconnections of the autopilot and autothrust, along with the loss of speed and altitude information. The flight crew used backup instruments and primary data was restored in about 5 minutes. The flight landed at Sao Paulo with no further incident and there were no injuries and damage.
The Safety Board has become aware of another possibly similar incident that occurred on June 23 on a Northwest Airlines A-330 (registration unknown) flying between Hong Kong and Tokyo. The aircraft landed safely in Tokyo; no injuries or damage was reported. Data recorder information, Aircraft Condition Monitoring System messages, crew statements and weather information are being collected by NTSB investigators.
What makes that really interesting, is that earlier that day, before the press release, I received this email forwarded from a trusted source, who in turn received it from a trusted source. (I know that’s more than a couple of degrees of separation from being corroborated, but in affairs like these people have to be careful: Neither Airbus nor its partners will much appreciate someone casting doubt on their products):
(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.
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…
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.
The captain 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. The captain did a great job fly and staying cool. We did our procedures called dispatch and maintenance on the SAT COM and landed… That’s it.
Airbus says it’s “too soon to say.” I wonder if they just don’t want to?
It is too soon indeed — to go all automatic on civilian airliners. Especially when the failure of a single system results in a breakaway rudder. Is it too much to ask that a secondary system to estimate airspeed, such as using that weather radar in a coarse doppler mode to estimate airspeed?
They can’t use GPS speed over ground if their primary speed indicators fail?
Rudder limit protection: Do you realize how little rudder movement they recommend even at low speed such as what happened to AA587? Something like 8 lbs and 1.5 inches. The problem is when you think you are going to die you may not hold back at only 8 lbs or less than 2 inches of throw, especially while on climb out at mere 103 seconds after roll-out off the numbers. It too was an A300 and problems with them go back to their early days of service. Lots of and Good stuff here: http://www.americanchronicle.com/articles/view/106754
The problems with the Airbus product line go way down into the certification process. If Vertical Stab’s are breaking off because near routine use exposes them to Ultimate Design limits then I think they are in big trouble. I mean, can you retrofit them enough to give you additional margin? That reciprocal certification treaty business has exposed the US flying public to unknown design limits. Limits that are found during the full scale fatigue testing that is mandatory for US air transport manufacturers. And that is testing to destruction by the way. Not so over there (the EU), they develop their limits by analysis and test to what they think the operational limits are and if the test limits are reached without anything nasty happening, they sign off. This means no one knows what the Ultimate loads are until, well, until something breaks off.
Now you want to talk about the strange flying, they have recorded many instances of Airbus aircraft flying about on their own and not in a good way either. Lots of issues out there.
For years I have traveled across and around the country all the while avoiding flights that had Airbus as the equipment. It has gotten almost impossible with the loss of airlines that flew all Boeing or McDonald-Douglas product. Now with the merger of Northwest into Delta the once Boeing only airline (Delta) is gone. Most of my flying is now being done on Southwest and let me tell you, its hard getting around.
BT: Jimmy T sends.
Wondered how long it would take for that e-mail to reach you. Rumor is the author is in a bit of hot water at the home office, they don’t like showing what’s under the kimono…
The root of the problem is pitot tubes. For you ground-pounders, pitot tubes take in air flow at the front of the jet and compare the pressure to the “static” pressure around the jet. This give you your airspeed. All of the jets that have had a problem have pitot tubes made by Thales, my airline is quickly changing out any Thales pitot tubes. Rumor is NTSB is going to shut down any jet that still has Thales tubes. (This is all heresay).
Looks like on the AirFrance jet, as with the Delta jet, the pitot tubes iced over. This lack of air input tells the jet it is going very slow and since it is so out of whack the whole system dumps. Losing all three air data systems makes the jet think it has stalled. The flight controls automatically revert to “upset law” which is a form of alternate law.
Rumor is NTSB is going to ground
Sobersub- good question about airspeed/groundspeed. I don’t know if they would still get the groundspeed indication with the loss of all the airspeed signals.
As far as rudder limiter issues, I am not as familiar with 330, but I want to ask someone about that. The bigger problem is not overspeeding or stalling due to lack of airspeed info. (Hence the 83% setting on the motors.)
Jimmy, I find your fear of Frog Planes amusing as Boeing rudders have killed almost twice as many people as Airbus flight controls. (We can talk fuel boost pumps too, if’n you want.)
I’m not sure NTSB has any authority to ground. I think FAA has to do that and FAA and NTSB don’t always see eye-to-eye, do they?
Not that I have ever put my ham-like mittens on a multiengine aircraft’s controls, but if the pitot tubes are icing up wouldn’t the apparent airspeed seem to increase due to the smaller diameter? and the pitot tubes do have heaters, yes? Can they ice up so quickly that there is no apparent increase before the apparent stopping? (the sampling filter on the software throws out the spiky increases as obvious errors and then shouts “You got it” to the pilot when the apparent slow speed persists? ) AND (last one) does this also have to do with Qantas’s Airbus troubles as well, which I had been reading was thought to be erroneous angle of attack readings?
( I can’t get the image of that Bugs Bunny cartoon where after fighting the gremlins, he pushes the autopilot button on the ‘B-19′ and a robot pops out of a closet, surveys the flight deck, grabs a ‘chute, and jumps.)
Nose – when all 3 air data systems dump from loss of the pitot, you don’t lose attitude as well, do you? I’m thinking if you have attitude and AOA, plus the 83% setting on the motors, you would seem to have a decent chance at controlling the AC at least long enough to assess and get in the book and on the horn for help. I guess the problem is that you’re not likely to see a frozen-over pitot unless you’re in the goo and then you’ve possibly got issues where the rudder limiters (that were controlled in part by input from the now-defunt air data computers) are gone and so now if you don’t remember to step gingerly on the rudder pedals you could cause problems in the tail.
Easier said from here than done in the air, of course. Just wonderin’.
Thanks – Brian
I read the above and thought “B2 crash”.
Isn’t there more than ONE pitot tube for reading airspeed? In the computer vernacular that sounds like “single point of failure”. Triple module redundancy and voting logic has been around a long time, for when the data must absolutely, positively, be there correctly.
I’m just a database hack, so I am commenting out of curiosity. Please enlighten.
Joel, think about the tubes (There are 3, JoeC) this way: if you are sitting still, nothing is going in (except “ambient”), the faster you go, the more air molecules go into the tube, so when the tube ices closed, or almost closed, nothing goes in and the tube senses low airspeed. They are heated, but the speculation is that the design doesn’t drain the supercooled water fast enough and it freezes faster than the heaters can melt it. I have been told (again hearsay) that the “bad” tubes have 1 drain hole for water, the “Good” tubes have two…
Brian, the “platform” is derived by three ADIRUs (Air Data Inertial Reference Units). If you loose all three air data inputs, you loose your primary attitude. Secondary should still be good. The Delta 330 guy didn’t mention losing standby instruments, but someone told me the AirFrance jet did. I don’t think the problem for AirFrance was so much rudder limiters, but attitude reference while in the goo. From back in my ASO days, lots of de-clothed bodies and big parts mean the jet probably broke up in the air which leads me to believe they blew through Vmo/Mmo and ripped it up?
Although it uses AOA extensively and has two AOA vanes, Airbus does not have an AOA indication in the instrumentation. (I think it would scare the Chair Force guys.) Douglas jet I flew did not either. Don’t know about Boeing. Anyone?
Thanks Nose.
Simply depressing to think that some component that has worked on thousands of aircraft for decades is the culprit. The engineers were too smart for themselves, or the management decided that drilling/machining two holes was far too expensive and the computerized test data showed one hole was sufficient to drain. In this case it may be best that the flight data recorders/cockpit voice recorder are not found. No one can imagine those poor sods up front watching all that gear shi_ itself, and they realize “time is up”. Nose’s point on Boeing vs AB kill ratio valid. So what do we fly? Wonder if I can put aux tanks in the Lance for the winter trip to Italy?
Nose – thanks for the response. Intersting info.
Nose, point taken however, a look at the numbers of raw aircraft out there tells the real story regarding risk in flying. While the A320 family of aircraft is a great product to get around on, there are about have of them as compared with the B737 family. (I dare say that this would hold true if you were to compare the two fleets side by side, there is just many more Boeing aircraft in the air than Airbus.) So you really can’t argue on raw body count as you have attempted.
While not a fan of the entire Airbus family of aircraft I do find myself having to fly on A319′s and have no qualms about that, they have proven to be a very safe aircraft and not just because I have an even number of events. I live in the suburban Philadelphia area and used to make many trips a year to Jacksonville, FL (when the Mighty War Hoovers were there in number) and had little choice if I wanted the direct flight (less than a 2-hour flight). The choice being the factor, I was able to crunch my own numbers and choose accordingly. Delta offers a connection there via MD80 so you will never guess what I flew, yeah like I said the A319 is a nice Jet to get around in.
I still worry about the certification process and I don’t think we should be giving one manufacturer a buy-in by treaty. There are other issues that people argue over regarding Boeing vs Airbus (direct subsidies vs indirect, all the fly-by wire nonsense etc) my worry is that we don’t know what the true ultimate limit is until you have a debris field. I just don’t want to be a member of that “flight test team”.
BT: Jimmy T sends.
So I guess we won’t be able to walk into the cockpit and find that some pilot has hung a tennis ball from the ceiling and restored the WWI method of fly by wire….
If the electronics is what fails and puts the rudder limiter out of play is there some reason that we cannot look into a mechanical rudder limiter that is pushed into position once the necessary restrictions on rudder movment are in play? Such a system could stay locked in place until it received a positive command to unlock and slide back. A signal input failure would not automatically remove the rudder limiter.
SWO guy, part time engineer, zero experience in aircraft use or design. Just curious. Is there a web sight where one can read up on fly by wire, alternate law and modern flight controls?
Leaving aside issues of pitot heads (which are heated of course and I can vouch for just how hot they get – suggest we forget the ice idea with three heads!), I caught a news item in the aviation press that this particular aircraft was involved in a taxing accident recently (within last year I believe) with an A320. Serious damage was done to the tail section of the 320 but apparently following tests on the AF A330 nothing serious was found amiss as far as its wing was concerned – and the aircraft was cleared for flight. I really don’t want to start another fruitless conspiracy theory but it is perhaps an issue that encountering serious vertical up/down drafts in cum/nimb, the wing cleared of structural damage was perhaps suffering from something that was not obvious to post-accident damage inspection? You don’t need to be a structural engineer to make some sort of connection with prior damage to a later accident – the 747 crash near Mt Fuji is one example where a botched repair following a tail scrape led to catastrophic failure – and there are many others. It’s fair to say that I have no detail of the ground collision issue and cannot now find where I originally saw it. Anyone else know of this? It was not a figment of my imagination I’m sure.
Recommend airline pilots look at their engine tapes once in a while at cruise, transition or in the pattern. Get a feel for what it takes. Don’t just fly whatever it takes.
Power settings rarely lie unless something is hanging out or you have combat damage. Cross check. Monitor all that on A/P while you eat your sandwhich and read the WSJ.. (not you Nose)
b2
b2/
Are you implying that Nose is 1) too competent a pilot as to not already be doing what you recommend, or 2 ) is a knuckle-dragger neither intelligent enough nor intellectually curious enough to decipher all the really big words in the WSJ?
VX,
#1 most certainly, if he can board a contraption with as many moving parts as a Hummer he’s already way ahead of anybody (except Sully, a former Phantom driver) on any flying skills!
#2- The WSJ he just scans on his BB. No. I’m sure Nose reads Dostyevsky/Kant/Gibbon while on A/P enroute.
B2
Looks like an A310-300 went down off Comoros on approach. Rough WX. One known survivor.