tag:blogger.com,1999:blog-3991004594884305625.post4475400011132823159..comments2023-11-28T23:42:25.873-08:00Comments on Satcom Guru: What happened on ET302?Peter Lemmehttp://www.blogger.com/profile/16409315777756590084noreply@blogger.comBlogger55125tag:blogger.com,1999:blog-3991004594884305625.post-43469493955325632232019-05-31T19:03:35.035-07:002019-05-31T19:03:35.035-07:00Wow, the plane parts are very confusing for beginn...Wow, the plane parts are very confusing for beginners who don't know anything about aircraft.Infopintarhttp://infopintar.netnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-3804943495477659412019-05-12T16:40:28.471-07:002019-05-12T16:40:28.471-07:00To your last two points.
I cannot fully explain wh...To your last two points.<br />I cannot fully explain why, upon reactivating electric trim, they did not take "control of the situation". One explanation is that the trim "blips" caused a shudder due to the high speed, but I cannot say if that was a factor. <br />The Ethiopian crew made no attempt to reduce elevator command to aid trimming nose up, and were left unable, as best can tell from the data.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-7194129175499605662019-05-12T16:37:10.542-07:002019-05-12T16:37:10.542-07:00It is so odd that Boeing chose to change something...It is so odd that Boeing chose to change something, something that had to be evaluated by the FSB, that reduced functionality. There was no service related compelling issue in the circuit as far as I know - it has held up well these 50 years. While the general procedure could have been left untouched, the AD issued after Lion Air could have used the Autopilot cutoff switch (if it had been retained) as a surrogate MCAS off switch. For an augmentation system they put no switch, no indicator dedicated to it, and then took out the one switch that could be used, for no perceptible benefit.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-7230442796894098782019-05-12T16:33:16.463-07:002019-05-12T16:33:16.463-07:00There is no mention, but there must have been. Els...There is no mention, but there must have been. Else the EFSM would have been failed in some manner (it has a "dual-coil" actuator - either SMYD can command it independently).Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-71189071648310544142019-05-12T16:29:28.669-07:002019-05-12T16:29:28.669-07:00The issue raised by EASA is that you may need to m...The issue raised by EASA is that you may need to manually trim beyond the allowed Electric Trim range under certain weight/speed combinations (that are rarely encountered). There has been no assertion that the stabilizer electric trim actuator was mechanically unable to move the stabilizer nose up.<br /><br />The minor trim occurrences are confounding. It is possible at the high speed that the trim commands caused noticeable shudder, which "gave them pause", but this was also the stimulus for MCAS to command again.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-88087963983689742632019-05-11T22:42:08.568-07:002019-05-11T22:42:08.568-07:00RE pprune forum- Amen amen amen- I made a simple ...RE pprune forum- Amen amen amen- I made a simple suggestion in april in a post re manual trim force for which the main- top big boy moderator took exception in a very uncivil fashion. Attempts to explain via a civil discourse only resulted in more extreme uncivil response, and removal of all my posts, and most of the thread- eventually removing not only my posts, but those of some very intelligent and qualified responses. Currently almost any thread re 737 and or max is now locked with apparently no new thrreads or posts on the subject allowed. Perhaps there is some ' corporate' pressure being applied ??Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-84731576325375584252019-04-30T16:33:20.473-07:002019-04-30T16:33:20.473-07:00No, the final two electric trim inputs were ineffe...No, the final two electric trim inputs were ineffectual because they were very short in duration ('blips') and consequently the stabiliser barely moved, if at all. Andrewnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-32358595844632181922019-04-30T04:47:13.339-07:002019-04-30T04:47:13.339-07:00Hi, entirely unqualified observer - but I have rea...Hi, entirely unqualified observer - but I have read the PPRUNE thread from beginning to present: There were some posts a while back stating that electric trim does not have as much authority as manual trim, ie there is a lower limit to the stab leverage it can oppose. Does this explain the final 2 ineffectual attempts with the trim switches?Hillman Minxhttps://www.blogger.com/profile/15811455097743256823noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-86246630008927842622019-04-24T23:06:34.602-07:002019-04-24T23:06:34.602-07:00I wouldn't trust the pprune forum at all. It&#...I wouldn't trust the pprune forum at all. It's curated heavily and run by a power crazed dude who doesn't approve posts he doesn't agree with. I was reading it and on many threads there's tons of complaints about the level of curation and bias moderating. The only reason why there is discussion about the level of bias is b/c there are teams of mods and they don't all mod the same way. Should boycott that forum tbh. It looks like an open discussion but it's really heavily bias.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-7276951597866192532019-04-24T11:44:38.578-07:002019-04-24T11:44:38.578-07:00Here’s one where a bird strike hit the AOA vane an...Here’s one where a bird strike hit the AOA vane and broke it off.<br />A Cargolux Boeing 747-400, registration LX-FCL performing freight flight CV-775 from Calgary,AB (Canada) to Luxembourg (Luxembourg) with 2 crew, was in the initial climb out of Calgary's runway 35R when a loud bang was heard followed by the stick shaker activating. The airspeed was still alive and safe, however, the indications of the stall margin were missing. The crew continued the climb and assessed the situation suspecting a nose tyre had failed and damaged an angle of attack (AoA) vane, then stopped the climb at 12000 feet reporting a damage AoA vane and decided to return to Calgary, where the aircraft landed safely about 40 minutes after departure.<br />The Canadian TSB reported no damage was found to the nose tyres, however, maintenance determined the right hand AoA vane was missing, there was evidence of a bird strike. The AoA vane was replaced and a bird strike inspection performed, then the aircraft returned to service.<br />https://www.aeroinside.com/item/7646/cargolux-b744-at-calgary-on-may-28th-2016-bird-takes-aoa-vane-out<br />This was discussed on .pprune.org.<br />https://www.pprune.org/tech-log/580217-744-what-if-we-lose-aoa-vane.html<br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-23031646974415931772019-04-20T03:09:37.462-07:002019-04-20T03:09:37.462-07:00Maybe following the philosophy that the pilot shou...Maybe following the philosophy that the pilot should not be able to permanently override MCAS (unless in a full stab runaway emergency)?Spornradhttps://www.blogger.com/profile/13499648828513945851noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-53845642426908856542019-04-19T16:30:33.008-07:002019-04-19T16:30:33.008-07:00it is a really big question. Putting two switches ...it is a really big question. Putting two switches to do the same function is a strange change, just in general.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-78156227430551003492019-04-16T12:20:50.051-07:002019-04-16T12:20:50.051-07:00Peter, any thoughts on why the functionality of th...Peter, any thoughts on why the functionality of the STAB TRIM CUTOUT switches was changed on the 737 MAX?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-11944610365362307542019-04-12T07:37:51.661-07:002019-04-12T07:37:51.661-07:00It is unknown what the FDR records when the electr...It is unknown what the FDR records when the electric trim is activated and either the column cutout and/or one or both of the cutout switches is thrown.<br />If the FDR does'n record commands when the column cutout is open then that could explain why no ANU command was recorded despite the electric trim was pushed to ANU. In that case the Stab Trim Override switch could have helped to restore electric trimming.<br /><br />Another piece of information, the stall warning system is activated when the Radio Altitude is >10ft.Michelhttps://www.blogger.com/profile/17519499067682794542noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-56039538913953551442019-04-11T14:19:50.381-07:002019-04-11T14:19:50.381-07:00It does appear that the autopilot commands are rec...It does appear that the autopilot commands are recorded with the cutout, but nothing to confirm the yoke switches. The discussion is a bit unclear, but on first blush he tries the yoke switch and then the crank. The captain may have been cradling the yoke so his hands were not on the wheel. I don't think they were faced with anything like 250 turns to get the stab back into the 4-5 unit range - something like 12-20 is what I was led to believe (but have not found a conclusive source). the area mic is designed to pick up noises.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-57472140083961100702019-04-11T13:43:27.045-07:002019-04-11T13:43:27.045-07:00Peter, did the first officer try the manual trim w...Peter, did the first officer try the manual trim wheel crank or the manual trim switch when he said it didn't work after he shut off the power to the tail? Does the data recorder record blips using the electric trim switch when the power to the tail is off? I saw that it records MCAS trying to do it with the power off. I could not determine what the first officer actually tried to do that he said didn't work from the report. Is doesn't work what a pilot would say or was that someone editorializing in the preliminary report. No mention of the Captain helping and it was less than eight seconds of trying. I would have expect him to help. Maybe he was hold the yoke to aft real hard. Would the pulling out of the handle on the manual crank cause a sound on the cockpit voice recorder to determine if the first officer really tried the crank. I saw a video where they were doing the crank in a 737 MAX simulator and I could clearly hear the sound of him moving the crank handle out of its stowed position and a lot more audio when they both cranked. I think I heard it took 250 rotations to go from one end to the other.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-89163629522245306232019-04-10T17:43:37.013-07:002019-04-10T17:43:37.013-07:00Peter, your analysis appears to be spot on. Your l...Peter, your analysis appears to be spot on. Your last graph, in conjunction with the sudden 75 deg left AOA value and the loss of the AOA vane heater just after what obviously must have been a bird strike, overwhelmingly suggests that the vane was gone and that just a nub of the vane's supporting stalk was all that remained.GoneToPlaidhttps://www.blogger.com/profile/03129948734295748830noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-21612226791384142882019-04-10T12:07:32.977-07:002019-04-10T12:07:32.977-07:00Not reported, but if EFSM activated, there should ...Not reported, but if EFSM activated, there should have been a Master Caution/FLT CONT/FEEL DIFF PRESS annunciation. The FLT CONT annunciation is on Captain's side, and he might have been to overwhelmed to notice since there was also a Master Caution for the ANTI-ICE.Andyhttps://www.blogger.com/profile/02276619041267501471noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-15002649470577730202019-04-10T11:45:58.696-07:002019-04-10T11:45:58.696-07:00As to why the MCAS bypasses the control column cut...As to why the MCAS bypasses the control column cutoff switches, MCAS needed to be able to respond to an accelerated stall (nose low recover, turning stall) when the control column might be displace far enough aft to trigger the cutout switch.<br /><br />As far as the redesign of pedestal cutout switches, I suspect this is what happened: Current 737NG procedures requires the use of BOTH switches in case of a runaway. We no longer try to isolate the system. Since both switches are used by procedure, then there really isn't a need for two switches on the MAX. However, I have been told that they retained two switches in series for redundancy in case of a rare instance of switch (or more likely, relay) welding. I suspect the real reason was to retain as much commonality as possible. Going from the NG to the MAX, you have two switches, and you use both of them. No difference in procedure, no training required.Andyhttps://www.blogger.com/profile/02276619041267501471noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-79933709322329253572019-04-10T08:39:01.454-07:002019-04-10T08:39:01.454-07:00Ron Belt 10 February 2018
Marek, Thank you for y...Ron Belt 10 February 2018<br /><br />Marek, Thank you for your comment and additional recommendations. My post containing example recommendations was intended to focus more attention on finding solutions for ALL the problems experienced by the pilots in these B737 incidents, and not to focus exclusively on just the MCAS problem. Boeing would like to limit the discussion to the MCAS issue only because it will get its planes off the ground again in the shortest possible time. But fixing MCAS will not eliminate all the other problems that the pilots experienced. <br /><br />By the way, if only one stick shaker is activated, then if the ADIRU on that side is turned off on, and the other ADIRU is used for both pilot’s displays and aircraft control, then MCAS will continue to operate but with a different AoA sensor that is likely still good. This is why one has redundant AoA sensors and ADIRU’s. It maintains the protection that MCAS provides. If trimming problems still remain after ADIRU switching, then MCAS can be shut down using the two cutout switches.<br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-76748869770118912172019-04-10T00:53:16.972-07:002019-04-10T00:53:16.972-07:00Ron: I think your 1 b is a bit questionable, for t...Ron: I think your 1 b is a bit questionable, for this is exactly the situation where unintended nose-up pitch (the reason for inventing MCAS) would be most dangerous.<br /><br />What about forcing Boeing to revert the cutout switches to the long-proven classics & NG setup? Including additional training and procedures for recognizing and handling erroneous MCAS interventions (e.g. using autopilot cutoff only as a first attempt before throwing both of the switches)? This would further benefit a lot from a clear audible and/or visual indication of an MCAS intervention, which needs to remain present for some time even after the MCAS pitch-down movement has been finished?Marekhttps://www.blogger.com/profile/07523007600490465348noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-87847418440667508442019-04-10T00:48:10.776-07:002019-04-10T00:48:10.776-07:00What I saw barely mentioned is the incomprehensibl...What I saw barely mentioned is the incomprehensible delay built into MCAS. It is primarily a "stick feel" system, Boeing says. From a human factor view I find the delay after flaps up makes the system outright wicked. The delay makes it hard for the pilot to causally connect the events. Does such a delay also apply to AOA trigger? It is already a slow system compared to lets say a stick pusher...Spornradhttps://www.blogger.com/profile/13499648828513945851noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-28030569437977153652019-04-09T14:06:22.914-07:002019-04-09T14:06:22.914-07:00Ron Belt 8 February 2018
Peter, here is another ...Ron Belt 8 February 2018<br /><br />Peter, here is another B737 incident caused by a faulty AoA sensor. The aircraft was a 737NG with registration F-GZHO that took off from Paris Orly on 8 February 2018. During takeoff the “IAS DISAGREE, “AoA DISAGREE” and “ALT DISAGREE” warning lights turned on. The aircraft returned safely to Orly. BEA reported that a post-flight inspection revealed that an AoA probe had failed. On a previous flight the same aircraft had an intermittent AoA problem. This incident is still being investigated by the French BEA as investigation number BEA2018-0071. No report has been issued. Refs:<br /><br />1. https://www.aeroinside.com/item/11033/transavia-france-b738-at-paris-on-feb-8th-2018-ias-aoa-and-alt-disagree.<br />2. http://avherald.com/h?article=4b4f3b2b. See also comments by Mikie and Anonymous.<br />3. https://www.bea.aero/en/investigation-reports/notified-events/detail/event/incident-du-boeing-737-immatricule-f-gzho-et-exploite-par-transavia-survenu-le-08022018-a-orly-94/.<br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-68502408556334962802019-04-09T11:50:22.045-07:002019-04-09T11:50:22.045-07:00Hi Ron, I will dedicate a whole post to that point...Hi Ron, I will dedicate a whole post to that point, still noodling on it. I agree with your recommendations. I wonder as well why they cannot have a procedure to deal with erroneous AOA. It would mean turning off the offending SMYD, I think. Mostly to kill off EFSM and to allow autopilot command. The displays can be switched to source off the good side (DEU). No doubt, much to consider.Peter Lemmehttps://www.blogger.com/profile/16409315777756590084noreply@blogger.comtag:blogger.com,1999:blog-3991004594884305625.post-77919733354424119942019-04-09T11:19:35.400-07:002019-04-09T11:19:35.400-07:00Ron Belt 8 April 2019
Peter, your summary of thi...Ron Belt 8 April 2019<br /><br />Peter, your summary of things to be learned from the ET302 crash is excellent. But it leaves out any recommendations for things to be changed to prevent such an accident from happening in the future. Here are some recommendations to consider after having read your summary:<br />1. MCAS should be disabled in parts of the flight envelope where it could be a danger:<br /> a. At high speeds near VMO where a sudden stabilizer nose down command can cause an abrupt and dangerous change of altitude<br /> b. At low altitudes where recovery time from a nose down pitch command is insufficient to resume level flight.<br />2. MCAS should perform a data valid test on the AoA sensor inputs<br /> a. Any AoA inputs above and below some reasonable angle like +25° or -45° should be set equal to the limits or rejected completely.<br /> b. Related question: Why is the output range of AoA sensors as high as ±90° or ±100° when aircraft rarely go above some smaller number like +25° or -45°?<br />3. The MCAS fix currently being proposed by Boeing will stop MCAS from issuing more than one nose down command when AoA sensors disagree, but will NOT eliminate other issues caused by erroneous AoA sensors which increase the pilot’s work load, such as:<br /> a. Control column pressure aft (pulling) on both sides is increased significantly and remains high even if MCAS commands to the stabilizer are stopped.<br /> b. Continuous or intermittent stick shaker on the affected side only, especially when it occurs immediately after takeoff and remains ON in level flight. The incessant vibration and noise drastically affects the pilot’s decision-making abilities.<br /> c. IAS is offset from valid values<br /> d. ALT is offset from valid values<br /> e. Minimum speed bar (red and black) on the affected side only.<br /> f. IAS DISAGREE alert<br /> g. ALT DISAGREE alert<br /> h. AOA DISAGREE alert (if the option is installed)<br /> i. FEEL DIFF PRESS light<br /> j. Autopilot may disengage<br /> k. Inability to engage autopilot.<br />To eliminate these problems, instead of leaving it up to the pilot and F/O to solve the problems in real time during a flight, consider giving guidance to the pilot to switch off the ADIRU on the side having an active stick shaker and replacing it with the ADIRU readings from the other side. (This guidance was provided in Air Worthiness Directive 2013-19-08 for an A320 with 3 AoA sensors and 3 ADIRU’s to switch off two of them).<br />Anonymousnoreply@blogger.com