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Aviation Forum / General / Aviation / July 2009Airbus Story (FWIW)
I just got this email from a retired airline pilot: From a retired NWA buddy of mine This from Brent Stratton, a friend and NWA pilot I flew the B-757 with out of our Tokyo base.........Now obviously on the A-330 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.  SignatureRemove _'s from email address to talk to me. > I just got this email from a retired airline pilot: > [quoted text clipped - 55 lines] > procedures called dispatch and maintenance on the SAT COM and landed in > Narita. That's it. Sounds plausible to me. A direct path from unexpected rain at high altitude (warm massive updraft in cu-nim?) to ice to frozen pitots to loss of rudder limiting. Then all it takes is injudicious heavy rudder in heavy turbulence and you are in deep do-do.... Brian W > Sounds plausible to me. A direct path from unexpected rain at high > altitude (warm massive updraft in cu-nim?) to ice to frozen pitots to > loss of rudder limiting. This meteorologist suggests that it would be highly unlikely for the Air France flight to have encountered rain or even supercooled water. He also suggests that the cause, if any, would be from descending air warming rather than an updraft: http://www.weathergraphics.com/tim/af447/ > Then all it takes is injudicious heavy rudder in heavy turbulence > and you are in deep do-do.... Why would they be using rudder at cruising speed? Further, according to the discussion in some of the other groups, the rudder limiter is still effective in alternate law. It supposedly clamps the limit at where it was when the shift was made from normal to alternate law. >> Sounds plausible to me. A direct path from unexpected rain at high >> altitude (warm massive updraft in cu-nim?) to ice to frozen pitots to [quoted text clipped - 6 lines] > > http://www.weathergraphics.com/tim/af447/ I read this over carefully, a few days ago. It seems like a respectable evaluation. And yes, it is highly unlikely situations which we are addressing. Both the eye-witness testimony of a person observing considerable precipitation at altitude, and the obvious meteorological observation that the higher the air, the colder, and the dryer (in absolute terms). If you accept this, then you have to accept that the water can only have come from below, via meso scale uplift (as the report puts it). That's not to say the uplift was not pulling water up higher than the fatal flight, then dropping it. These buildups are invariably turbulent. Brian W > Why would they be using rudder at cruising speed? Further, according to > the discussion in some of the other groups, the rudder limiter is still > effective in alternate law. It supposedly clamps the limit at where it was > when the shift was made from normal to alternate law. ...look at the first line in the ACARS messages: RUD TRV LIM FAULT... in other words, the rudder travel limiter not doing what it was supposed to do, i.e., limit the rudder travel. This was followed in fairly short order by a TCAS fault, an autothrottle disconnect, a/p disconnect and institution of alternate flight law algorithms. Look at the failure point of the 447 vertical stab and compare that with the failure point of the AA 300 that went down in 2001 on departure from JFK. Despite having a rudder travel limiter in place and working, the 2001 incident proved rather markedly that it is entirely possible, even at climb speeds, to overstress the vertical attach points of the structure. ...at cruise, in what may have been beyond extreme turbulence, that possibility may indeed be a probability in this case. We'll never know until the FDRs and CVRs are found and the data downloaded, but on that subject I have no faith that they will be found and, given Airbus's shenanigans with black boxes from earlier incidents, I have no faith that the company wants them to be found. >> Why would they be using rudder at cruising speed? Further, according >> to the discussion in some of the other groups, the rudder limiter is [quoted text clipped - 4 lines] > in other words, the rudder travel limiter not doing what it was > supposed to do, i.e., limit the rudder travel. My understanding from the pros in other groups, is that message simply says that the autolimiter disconnected, and as mentioned, the limits are clamped at what they were prior to the disconnect. It is supposedly part of the change from normal to alternate law. > This was followed in fairly short order by a TCAS fault, an > autothrottle disconnect, a/p disconnect and institution of alternate > flight law algorithms. > Look at the failure point of the 447 vertical > stab and compare that with the failure point of the AA 300 that went > down in 2001 on departure from JFK. They are different. Not at all the same type of attachment or type of failure. > Despite having a rudder travel limiter in place and working, The A300 was not a FBW aircraft. > the 2001 incident proved rather markedly that it is entirely possible, > even at climb speeds, to overstress the vertical attach points of the > structure. ...at cruise, in what may have been beyond extreme > turbulence, that possibility may indeed be a probability in this case. Why would an experienced pilot be using the rudder at all at cruising speed and at that altitude? > We'll never know until the FDRs and CVRs are found and the data > downloaded, but on that subject I have no faith that they will be > found and, given Airbus's shenanigans with black boxes from earlier > incidents, I have no faith that the company wants them to be found. So they will just hope no other aircraft decide to disappear while in cruise flight? Or do you think they already know what went wrong, and are correcting it behind the curtain? > >> Why would they be using rudder at cruising speed? Further, according > >> to the discussion in some of the other groups, the rudder limiter is [quoted text clipped - 40 lines] > cruise flight? Or do you think they already know what went wrong, and are > correcting it behind the curtain? Look at the behaviour of US Scare and Boeing with the 737 rudder reversal problem. "Problem? There is no problem" Meanwhile, back at Area 51, er, Seattle, all manner of work towards a solution is being performed. > Look at the behaviour of US Scare and Boeing with the 737 rudder > reversal problem. > > "Problem? There is no problem" Meanwhile, back at Area 51, er, > Seattle, all manner of work towards a solution is being performed. They had access to the FDR information, and I don't think US Airways was complicit in blaming pilot error. That was only Boeing, and yes, they were a.s covering. In the case of AF447, the last thing the would want is for another aircraft to self-destruct, given the design is the basis for the potential US tanker program, and the 350. Without the FDRs, can they be sure they have actually solved the problem? Do they know enough to identify the cause with certainty, and know what needs to be done to correct things? > My understanding from the pros in other groups, is that message simply > says that the autolimiter disconnected, and as mentioned, the limits are > clamped at what they were prior to the disconnect. It is supposedly > part of the change from normal to alternate law. ...and if the pitot tubes were providing low airspeed data (which the OP mentioned in his post, saying "the Captains, First Officers, and standby airspeed indicators rolled back to 60kts...") prior to the rudder travel limiter disengage, those travel limits would be far less stringent than if the ADC "knew" the aircraft was travelling at cruise speed. > > This was followed in fairly short order by a TCAS fault, an > > autothrottle disconnect, a/p disconnect and institution of alternate [quoted text clipped - 5 lines] > They are different. Not at all the same type of attachment or type of > failure. Wrong. Both failure modes are nearly identical in apparent result (side loads beyond design limits) and the attach fittings (composites with steel/titanium attach points) are nearly identical as well. look at the photographs of both verticals. there is no crushing on the lower leading or lower trailing edges of the AF447 component that would indicate the failure took place fore and/or aft; on the other hand, the AF447 vertical shows skin tears along its lower edge that would indicate that the failure mode was due to sideloads exceeding design limits. > > Despite having a rudder travel limiter in place and working, > > The A300 was not a FBW aircraft. So what. The A300-600 has a rudder travel limiter, and its effectiveness has been the subject of numerous NTSB Safety Recommendations, to whit: "A review of the flight data for rudder position showed that, even after accounting for the slow response rate of the RTL, the rudder still appeared to exceed the estimated position at which it should have been limited by the RTL. This exceedance was as high as 4° near the end of the upset. The A300-600 RTL is designed and constructed so that it limits the rudder by reducing the allowable displacement of the rudder pedals. Testing of the RTL determined that if a pilot applies a sufficiently large pedal force when the pedal is at its travel limit, this will further slow or stop the movement and, consequently, the effectiveness of the RTL. As demonstrated by this event, such slowing or stopping of the RTL by application of large pedal forces could result in the rudder position substantially exceeding the designed travel limit. The Safety Board is concerned that such an increase in available rudder beyond the designed RTL restrictions could permit excessive rudder movements and possibly result in high loads on the vertical stabilizer." > > the 2001 incident proved rather markedly that it is entirely possible, > > even at climb speeds, to overstress the vertical attach points of the [quoted text clipped - 3 lines] > Why would an experienced pilot be using the rudder at all at cruising > speed and at that altitude? Because the first word governing an experienced crew's reaction to an emergency is "Aviate." That means (especially in light of a highly experienced crew reacting to an A/P disconnect as well as multiple warnings) put your feet on the pedals and your hands on the yoke and fly the thing until you, and the rest of the crew, can sort it all out. CRM 101. > > We'll never know until the FDRs and CVRs are found and the data > > downloaded, but on that subject I have no faith that they will be [quoted text clipped - 4 lines] > cruise flight? Or do you think they already know what went wrong, and are > correcting it behind the curtain? i have no opinion one way or another. all i know is that there was a fly-by accident at a press event years ago involving (if i recall correctly) an A320 where, despite a TOGA command, the aircraft did not respond and sank into the trees at the end of the runway. when the "black boxes" were made available to the NTSB and public the serial numbers (as well as the paint) on what were purported to be the boxes from the accident aircraft were not the same as those that had been installed on the accident aircraft. >> My understanding from the pros in other groups, is that message simply >> says that the autolimiter disconnected, and as mentioned, the limits are [quoted text clipped - 7 lines] > stringent than if the ADC "knew" the aircraft was travelling at cruise > speed. Is the pitot-static systems linked as in GA aircraft? If so, then a clogged pitot would read low airspeed or am I in the dark here? SignaturePWH and the Pricelessware Con Game - Exposed http://tinyurl.com/knogy8 > > ...and if the pitot tubes were providing low airspeed data (which the > > OP mentioned in his post, saying "the Captains, First Officers, and [quoted text clipped - 5 lines] > Is the pitot-static systems linked as in GA aircraft? If so, then a > clogged pitot would read low airspeed or am I in the dark here? If you meant to ask whether the 3-odd pitot systems, the answer I think is a No, else you'd have both pilots' ASIs reporting the same speed all the time, which isn't the case. Pilots can in fact even choose which pitot system the Autopilot can take inputs from. I seem to remember that one of the criticisms of the PF's actions in the Birgen Air crash was that he didn't opt to link the AP to the functional pitot system (FO's) although he knew right during the takeoff roll that his own pitot had gone kaput. Ramapriya >> My understanding from the pros in other groups, is that message >> simply says that the autolimiter disconnected, and as mentioned, the [quoted text clipped - 7 lines] > stringent than if the ADC "knew" the aircraft was travelling at cruise > speed. Three separate systems all roll back to the same speed identical simultaneously? That is beyond wild speculation. As soon as one didn't match the others, the system would cut out. >> > This was followed in fairly short order by a TCAS fault, an >> > autothrottle disconnect, a/p disconnect and institution of [quoted text clipped - 15 lines] > would indicate that the failure mode was due to sideloads exceeding > design limits. Wrong. The AA failure was in the attachment lugs, and the rudder was completely missing. In the photos of the AF VS, you can see the lugs are intact, and that the failure was in the surrounding structure, plus most of the rudder is still attached. Further, the attachment arrangement between the 310 and the 330 was redesigned. >> > Despite having a rudder travel limiter in place and working, >> [quoted text clipped - 20 lines] > restrictions could permit excessive rudder movements and possibly > result in high loads on the vertical stabilizer." My point is that the two aircraft are entirely different, as are the controls limiting rudder travel. You might as well be trying to compare a Boeing and an Airbus because they both have two wings and a tail. >> > the 2001 incident proved rather markedly that it is entirely >> > possible, even at climb speeds, to overstress the vertical attach [quoted text clipped - 12 lines] > the pedals and your hands on the yoke and fly the thing until you, and > the rest of the crew, can sort it all out. CRM 101. Which means they wouldn't consider using the rudder at high speed and altitude. There is practically no situation I can think of where an experienced crew would consider using the rudder. The rudder simply isn't used to "aviate" at altitude. Using it would be an indication of inexperience. >> > We'll never know until the FDRs and CVRs are found and the data >> > downloaded, but on that subject I have no faith that they will be [quoted text clipped - 13 lines] > from the accident aircraft were not the same as those that had been > installed on the accident aircraft. You certainly do have an opinion, or you wouldn't have been posting this stream of misinformation. BEA is now saying that AF447 entered the water in one piece, in a horizontal attitude, but with a high vertical force. That pretty well describes a flat spin. That would not have happened if the VS separated at high altitude. http://tinyurl.com/mb4mmt (en Francais) And I see a number of US media sources can't translate French aeronautical terms correctly, as they are saying the aircraft went straight down, almost vertically. Il paraît avoir heurté la surface de l'eau en ligne de vol Means that the aircraft struck the surface in a horizontal attitude. avec une forte accélération verticale" Means with high vertical acceleration, meaning it was in an aerodynamic stall. > BEA is now saying that AF447 entered the water in one piece, in a > horizontal attitude, but with a high vertical force. That pretty well [quoted text clipped - 16 lines] > Means with high vertical acceleration, meaning it was in an > aerodynamic stall. BEA is also reporting that the vertical stabilizer separated from the aircraft from the back to front, with a slight leftward twist. They also said that faulty pitots were a factor in the accident, but not the cause. Whatever conclusions you can draw from those statements. (snip) you're not a pilot, are you? Loss of airspeed renders the rudder limiter inoperative, which can lead to vertical stabilizer overstress and possible failure. This may have happened on Flight_447. One possible solution would be to add strain gauges that directly measure the stress in the vertical stabilizer and feed this data to the rudder limiter along with the airspeed and altitude information. This would allow the rudder limiter to continue functioning even when the air-data system fails. John schrieb: > Loss of airspeed renders the rudder limiter inoperative, which can > lead to vertical stabilizer overstress and possible failure. This may [quoted text clipped - 3 lines] > airspeed and altitude information. This would allow the rudder > limiter to continue functioning even when the air-data system fails. > Loss of airspeed renders the rudder limiter inoperative, which can > lead to vertical stabilizer overstress and possible failure. This may > have happened on Flight_447. Drinking too much red wine and then deliberately flying a flick roll can also lead to empennage overstress and possible filure. This may also have happened on Flight_447. >> Loss of airspeed renders the rudder limiter inoperative, which can >> lead to vertical stabilizer overstress and possible failure. This may [quoted text clipped - 3 lines] > also lead to empennage overstress and possible filure. This may also > have happened on Flight_447. So does that rule out white wine as the cause? I hope so, as I have a slight preference for whites over reds. What if the pilot had the fish? > >> Loss of airspeed renders the rudder limiter inoperative, which can > >> lead to vertical stabilizer overstress and possible failure. This may [quoted text clipped - 8 lines] > > What if the pilot had the fish? Then he wouldn't have hit the pitot heat switch |
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