Ethiopian airliner down in Africa
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Just trying glean what flight regime MCAS needs to protect. So, they didn't want the column cutout switch to work because they envisioned pulling hard and not trimming. Trimming would normally return the column to neutral. Two things come to mind. Windshear escape in the clean config and steep turns with guys that don't trim. I (having the T-38 training mantra embedded, "trim trim trim") would trim during steep turns so that would not be a problem for me or MCAS. Of course steep turns are a simulator exercise so not really relevant. Again I ask why put out the original AD and not caution about being careful when pulling with the loss of MCAS.
On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.
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Handling qualities regulations require starting from a wings level, trimmed condition and then demonstrating flying to high AOA (both by slowing and by executing a wind-up turn at constant speed) and showing that the stick force throughout the maneuver (flown without trimming) increases monotonically (i.e., the required pull does not decrease throughout the maneuver). These maneuvers involve insertion of enough aft column to go past the column cutout switch and thus MCAS must be able to continue to add airplane nose down stabilizer with the column pulled past the position of this switch.
On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.
On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.
Last edited by jimtx; 14th Mar 2019 at 15:17.
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i have had some dealings with transponders, and the rule of thumb is that.
Mode-c gives 1013 baro altitude.
Mode-s gives 1013 baro altitude.
Ads-b also gives 1013 baro altitude, to be compatible with the above.
Flarm and paw give gps altitude.
As far as i know, fr24 is simply picking up ads-b 1013 pressure altitudes, so you will need to know the qnh of the day, and the altitude of the airport, to calculate the true height of the aircraft. Transponders were designed for seperation on airways, not for separation with terrain, so the older units all used 1013 baro, and ads-b follows suit.
(if ads-b used gps alt, then atc would not be comparing like with like. However, newer systems like flarm and paw can happily use gps alt, because they all use gps, so they are comparing like with like.)
silver
Airfield elevation 2,334m / 7,625 ft
Last edited by Super VC-10; 14th Mar 2019 at 04:35. Reason: + airfield elevation
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Crash in Ethiopia: Germany can not analyze black boxes
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html
Crash in Ethiopia: Germany can not analyze black boxes
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html
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Dead link, but the gist of a google search using those terms is that Germany currently lacks the ability to assess this new version of the FDR. I do hope that there is a non-US avenue for analysis. I never used to feel that way, but lately I get to feeling a bit queasy getting between Americans and money.
France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...
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It's not like there won't be an FAA/NTSB team and Boeing reps in the room. I fail to see what the big deal is.
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Ethiopian Airlines on Twitter: "An Ethiopian delegation led by Accident Investigation Bureau (AIB) has flown the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) to Paris, France for investigation."
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On top of that, STS trims on all departures, not only in the light aircraft, high thrust aft CG situation.
It’s a weird system that I could do without.
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After 1000 feet I noticed a decrease in aircraft performance. I picked up that the autothrottles were not moving to commanded position even though they were engaged. I'm sure they were set properly for takeoff but not sure when the discrepancy took place. My scan wasn't as well developed since I've only flown the MAX once before. I manually positioned the thrust levers ASAP. This resolved the threat, we were able to increase speed to clean up and continue the climb to 3000 feet.
Shortly afterwards I heard about the (other carrier) accident and am wondering if any other crews have experienced similar incidents with the autothrottle system on the MAX? Or I may have made a possible flying mistake which is more likely. The FO (First Officer) was still on his first month and was not able to identify whether it was the aircraft or me that was in error.
Shortly afterwards I heard about the (other carrier) accident and am wondering if any other crews have experienced similar incidents with the autothrottle system on the MAX? Or I may have made a possible flying mistake which is more likely. The FO (First Officer) was still on his first month and was not able to identify whether it was the aircraft or me that was in error.
An Alternative to MCAS
As has been very well explained, the reason for MCAS was to cause ANU stick force to increase or at least not to decrease when AoA approaches stall angle. That was a certification requirement.
However, by repeating the trim input at remaining high AoA, something more than just desired stick force increase is achieved.
What is needed is a one time increment in stick force to bring the Max into line with the other 737 models - if that was the aim.
This can be achieved by adding feel spring force to the control run, cut in point determined by AoA.
If there were then a fault in the AoA signal, the increment would be applied - once - which would be trimmable and controllable.
The whole sorry idea of playing with the stab trim to achieve what is really a desired primary control feel correction is unnecessary and as we see, unsatisfactory and potentially dangerous.
A feel spring solution should satisfy the certification authorities and the desire by the manufacturer to keep the Max in the 737 family, rating wise.
However, by repeating the trim input at remaining high AoA, something more than just desired stick force increase is achieved.
What is needed is a one time increment in stick force to bring the Max into line with the other 737 models - if that was the aim.
This can be achieved by adding feel spring force to the control run, cut in point determined by AoA.
If there were then a fault in the AoA signal, the increment would be applied - once - which would be trimmable and controllable.
The whole sorry idea of playing with the stab trim to achieve what is really a desired primary control feel correction is unnecessary and as we see, unsatisfactory and potentially dangerous.
A feel spring solution should satisfy the certification authorities and the desire by the manufacturer to keep the Max in the 737 family, rating wise.
If the manufacturer is interested in technical solving the issue, then the real data FDR and CVR of both flights are required. With the money at stake I have no doubt he is. So why should you think Boing has any benefit with tampering FDR or CVR data? It will be difficult enough to restore customer trust into that plane. So anything short of a thorough analysis yielding a transparent technical solution scrutinised by all parties including the regulatory bodies will not do.
So Honeywell would be my first shot to ask, the recorders hand delivered and the restorrage overseen by some trustable and technical savvy people.
Ask Airbus guys and some of the national experts in the regulatory bodies to participate.
So Honeywell would be my first shot to ask, the recorders hand delivered and the restorrage overseen by some trustable and technical savvy people.
Ask Airbus guys and some of the national experts in the regulatory bodies to participate.
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