B-738 Crash in Russia Rostov-on-Don
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It seems to me that according to the previously-posted article prepared by Boeing http://www.boeing.com/commercial/aer...ERO_2014q3.pdf shows several ways to crash the airplane without any mechanical/technical problem at all! I could be full of it, since I'm not a pilot.
It seems to me that according to the previously-posted article prepared by Boeing http://www.boeing.com/commercial/aer...ERO_2014q3.pdf shows several ways to crash the airplane without any mechanical/technical problem at all! I could be full of it, since I'm not a pilot.
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Correct link to Boeing Article
OK, this one works, at least for me:
http://www.boeing.com/commercial/aer...ERO_2014q3.pdf
I hope that every pilot who's flying passengers is thoroughly familiar with this information. Some of the responses here convince me that not everyone is familiar with this information. The article is on Page 13.
http://www.boeing.com/commercial/aer...ERO_2014q3.pdf
I hope that every pilot who's flying passengers is thoroughly familiar with this information. Some of the responses here convince me that not everyone is familiar with this information. The article is on Page 13.
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From MAK/IAC (Artur Muradyan, aide to chairman):
"At this time, we can neither confirm nor deny the reports of the pilots' last conversation. Neither MAK nor any of its employees gave any information to the media - not to Kommersant, not to anyone at all. When we release our data, it will be open to comment. We haven't yet completed the decoding of CVR and FDR, it's in progress, we're still analysing and compiling the data and identifying the [pilots'] voices. It's possible that we will release some preliminary data in a couple of weeks, but the final results of decoding will be published in a month."
"At this time, we can neither confirm nor deny the reports of the pilots' last conversation. Neither MAK nor any of its employees gave any information to the media - not to Kommersant, not to anyone at all. When we release our data, it will be open to comment. We haven't yet completed the decoding of CVR and FDR, it's in progress, we're still analysing and compiling the data and identifying the [pilots'] voices. It's possible that we will release some preliminary data in a couple of weeks, but the final results of decoding will be published in a month."
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And while a "split elevator" condition arising from both pilots pushing/pulling on the yokes against each other may occur in the 767 (see the final report for Egypt Air Flight 990), I have never heard of this for the 737, and that alone would not automatically cause loss of control and crash, much less a stall.
Bernd
EDIT: Egypt Air 990 was a 767. Thanks, Airbubba.
Last edited by bsieker; 28th Mar 2016 at 23:58.
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Talking about a fully mechanically controlled airplane this makes no sense at all.
In a "mechanically" controlled 737 (as you said it) dual input is very much possible. I suggest you update your knowledge - it is possible in ANY Boeing. If actions of both pilots are sufficiently different and forces exceed some limits - both sides will be separated, this was done to counter possible jamming of controls on one side, certification required such a solution.
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The controls are not "normally hydraulic, but manual fallback" - the pitch controls and ailerons are cable and pulley systems, with hydraulic assistance. Manual reversion simply means the hydraulic (or electrical for stab trim) assistance is removed. The controls can split between the two columns, the captains column connected to left elevator and ailerons, the fo's connected to right elevator and spoilers. They split in case one jams, as Olasek said.
Amazing how many people are commenting here without proper knowledge.
Amazing how many people are commenting here without proper knowledge.
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Come on chaps - how many have done a control disconnect in the sim? Looks like another 737 system that does not work.
Seems like a common thread to quite a few accidents in the last few years is inattention to the correct pitch attitudes. (Think of the initial autopilot disconnect on AF447). In the older types the flight director was a fairly crude device with limited modes so it was taken for granted that you needed to know the raw data attitudes for a given phase of flight and also to monitor carefully that these were being flown correctly.
Last edited by fireflybob; 28th Mar 2016 at 19:36.
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Originally Posted by Boeing 737 FCOM
The pitch control surfaces consist of hydraulically powered elevators [...]
[...]
With loss of hydraulic system A and B the elevators can be mechanically positioned by forward or aft movement of the pilots’ control columns.
[...]
With loss of hydraulic system A and B the elevators can be mechanically positioned by forward or aft movement of the pilots’ control columns.
And what I mean is that it makes not sense to say any single entity receives "conflicting commands", since after a split there is no longer a single system, but rather two separate ones (if that is indeed the case; see below). And an airplane as such cannot receivce "conflicting" "commands", it just experiences forces and moments and reacts according to the laws of physics.
The controls can split between the two columns, the captains column connected to left elevator and ailerons, the fo's connected to right elevator and spoilers. They split in case one jams, as Olasek said.
In fact it says that both elevators are linked by a torque tube, which is mentioned separately from the so-called "override mechanism", which allows the two control columns to be separated in the event that one of them becomes jammed. This does not really imply that it is the torque tube which is broken to free a jammed control column, but rather the connection between the two control columns.
Amazing how many people are commenting here without proper knowledge.
If my understanding of 737 is demonstrably wrong, please correct me by citing authoritative sources (which I agree the FCOM is not for a technical description; but it often gives a good idea.)
Bernd
EDIT: Egypt Air 990 was a 767, Thanks to Airbubba for the correction.
Last edited by bsieker; 28th Mar 2016 at 23:58.
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Elevator Control Column Override Mechanism
In the event of a control column jam, an override mechanism allows the control columns to be physically separated. Applying force against the jam will breakout either the Captain’s or First Officer’s control column. Whichever column moves freely after the breakout can provide adequate elevator control. Although total available elevator travel is significantly reduced, there is sufficient elevator travel available for landing flare. Column forces are higher and exceed those experienced during manual reversion. If the jam exists during the landing phase, higher forces are required to generate sufficient elevator control to flare for landing. Stabilizer trim is available to counteract the sustained control column force.
In the event of a control column jam, an override mechanism allows the control columns to be physically separated. Applying force against the jam will breakout either the Captain’s or First Officer’s control column. Whichever column moves freely after the breakout can provide adequate elevator control. Although total available elevator travel is significantly reduced, there is sufficient elevator travel available for landing flare. Column forces are higher and exceed those experienced during manual reversion. If the jam exists during the landing phase, higher forces are required to generate sufficient elevator control to flare for landing. Stabilizer trim is available to counteract the sustained control column force.
......also of interest and applicable to the NG, but not the 300-500 Efis
During high AOA operations, the Stall Management/Yaw Damper (SMYD) reduces yaw damper commanded rudder movement. The EFS module increases hydraulic system A pressure to the elevator feel and centering unit during a stall. This increases forward control column force to approximately four times normal feel pressure. The EFS module is armed whenever an inhibit condition is not present. Inhibit conditions are: on the ground, radio altitude less than 100 feet and autopilot engaged. However, if EFS is active when descending through 100 feet RA, it remains active until AOA is reduced below approximately stickshaker threshold. There are no flight deck indications that the system is properly armed or activated.
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If my understanding of 737 is demonstrably wrong,