B-738 Crash in Russia Rostov-on-Don
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The 757's flight controls are in fact quite different from the 737's, e. g.
Originally Posted by Boeing 757 OM
[...] there is no manual reversion.
It also has three hydraulic systems instead of two.
EDIT: Thanks, Airbubba, Egypt Air 990 was a 767, but everything I said also applies to the 767, including the quote from the FCOM.
Bernd
Last edited by bsieker; 28th Mar 2016 at 23:58.
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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 757 (see the final report for Egypt Air Flight 990)
Instead of bemoaning people's lack of knowledge you could just respond to my wondering if the 737 systems are indeed supposed to work the same as in the 757.
A lot of 757 and 767 systems are similar but many, especially hydraulics, are significantly different. The two planes were literally designed by two different groups at the same company. Or, so they tell me...
Originally Posted by Defacto
During,manual go arounds,never needed much trim if any....i would believe if they needed a high amount of trim nose down would be if they initially way over pitched the aircraft.(whatever the cause may be).
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I don't know why but, FWIW, the Boeing FCOMs in general are notoriously poor by comparison with other manufacturers' FCOMs in providing aircraft technical information for flight crews, so misconceptions are bound to occur. For some here, a bit of professional courtesy and patience is necessary while others are sorting the question out. Airbus, Embraer & Dornier are far more detailed, helpful and well illustrated.
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FDMII:
Then again, major airlines, at least in the US., do not (or did not during my tour of duty) use Boeing's or other OEMs FCOMs. They wrote their own, tailored to their training methods, and with FAA concurrence.
The concept worked great at TWA. TWA called them FHBs, for Flight Operating Handbook. So, whether it was a 707, 727, 767, DC-9, MD-8x, L1011, all the FHBs had "that familiar appearance."
I don't know why but, FWIW, the Boeing FCOMs in general are notoriously poor by comparison with other manufacturers' FCOMs in providing aircraft technical information for flight crews, so misconceptions are bound to occur.
The concept worked great at TWA. TWA called them FHBs, for Flight Operating Handbook. So, whether it was a 707, 727, 767, DC-9, MD-8x, L1011, all the FHBs had "that familiar appearance."
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Airbubba:
Boeing has used tandem design teams for decades. The B-29 and B-50 e.g. The two teams "leapfrogged" each other, with only general exterior similarity. In the case of 757/767, they coordinated on general cockpit design and handling qualities, but little else.
A lot of 757 and 767 systems are similar but many, especially hydraulics, are significantly different. The two planes were literally designed by two different groups at the same company. Or, so they tell me...
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In the case of 757/767, they coordinated on general cockpit design and handling qualities, but little else.
The 777 was mostly a everett design team. The 787 was mostly Everett but had more than a few B2 experienced people, etc
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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.
Sorry to say so, but your say-so is not what I meant by "authoritative source". It would require some other document contradicting the 737 FCOM and mine and hec7or's reading of it. For example some documentation explaining that the torque tube between the two elevator surfaces is frangible and supposed to be broken by the override mechanism for dealing with a jammed control column.
« B737 Aircraft Control Override Devices: There are two devices that allow you to control the aircraft in case of a malfunctioning or jammed control system.
One concerns roll control. When one of the yoke cables (or aileron PCU/spoilers) becomes jammed or moves freely, the opposite control is still available to roll the aircraft. The two yokes are interconnected at the base of the co-pilots control column by the Aileron Transfer Mechanism through torsion spring friction and a “lost motion device”. If the FO control jams, the spring force can be overcome by the Captain thereby controlling the aileron PCU through cables. If the Captain control jams, the FO can control roll by use of the flight spoilers. Note that this only happens when the yoke has been turned ± 12° which engages a so called “lost motion device” which in turn operates the flight spoilers.
The second is related to pitch control. When one of the control columns becomes jammed, the crew can override (breakout) the failing control. The control columns are interconnected below the cockpit floor by a torque tube with a device that enables the controls to be separated from each other. The Elevator Breakout Mechanism connects both control columns by two springs which will separate the columns when ± 30Lbf/13Kgf is used to overcome them. When applied, the control columns are mechanically separated from each other. Note that deflection of the elevators is significantly reduced and a higher force is needed to move the elevators. (even higher than with manual reversion) »
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MOSCOW - Russian state television has aired the final words, of the pilots of the flydubai passenger jet that crashed in Rostov-on-Don last week killing 62 people, suggesting pilot error could be to blame.
Russia's Rossiya-1 channel said late on Friday it had obtained a transcript of the last words exchanged a minute before the Boeing 737 plunged to the ground from a source in the investigative commission with access to the plane's voice recorders.
The plane, which was arriving from Dubai, exploded into a fireball last Saturday after missing the runway in the city in southern Russia while making a second attempt to land in heavy wind and rain.
It was carrying 55 passengers and seven crew members. There were no survivors.
PICTURE: Russian Emergency Ministry rescuers search the wreckage of a crashed airplane at the Rostov-on-Don airport on March 20, 2016. CREDIT: AFP
The transcript suggests that the pilot lost control of the plane immediately after switching off the autopilot.
"Don't worry," the pilot says repeatedly in the transcript translated into Russian, before repeating seconds later "Don't do that!" The last words are repeated calls to "Pull up!"
For the last six seconds of the plane's dive, all that can be heard are "inhuman screams," the channel's source said.
The channel suggested -- citing specialists while stressing that this was not the official version -- that the pilot accidentally switched on a stabilising fin at the tail as he tried to pull the plane back to a horizontal position.
With this fin activated, "the plane practically does not react to the pilot's control panel" the channel said.
"The pilots clearly did not understand that the stabiliser was to blame for the steep dive."
The channel said the pilot could have accidentally switched on the button activating the fin due to his reported "chronic fatigue."
The only other possible explanation would be an "unprecedented glitch in the plane's automatic systems," the channel said.
Aircraft control out of sync
Sputnik media, meanwhile, reported on Monday that the Boeing 737-800 could have crashed due to a conflict in the cockpit.
PICTURE: File image of the interior of a Boeing 737-800. CREDIT: Flickr.com/Frans Zwart
According to a source of Russia’s Kommersant newspaper, decoding of the parametric data and voice recorders of the plane revealed that pilots had twice attempted to land the aircraft in automatic mode, but failed to do so due to difficult weather conditions. The pilots eventually decided to come in to land in manual mode.
Experts claim that the crew failed to take characteristics of Boeing 737-800 into consideration, particularly transition from landing to ascend. The pilot on the controls continued to ascend and attempted to pick up speed, while his co-pilot tried to stop gaining altitude. As a result, control of the aircraft was out of sync.
CREDIT: Faisal Akram from Dhaka, Bangladesh, via Wikimedia Commons
The investigation has not yet managed to establish which pilot made a fatal error.
Investigators have launched a criminal probe into whether poor weather, pilot error or a technical fault were behind the crash.
Russia's Rossiya-1 channel said late on Friday it had obtained a transcript of the last words exchanged a minute before the Boeing 737 plunged to the ground from a source in the investigative commission with access to the plane's voice recorders.
The plane, which was arriving from Dubai, exploded into a fireball last Saturday after missing the runway in the city in southern Russia while making a second attempt to land in heavy wind and rain.
It was carrying 55 passengers and seven crew members. There were no survivors.
PICTURE: Russian Emergency Ministry rescuers search the wreckage of a crashed airplane at the Rostov-on-Don airport on March 20, 2016. CREDIT: AFP
The transcript suggests that the pilot lost control of the plane immediately after switching off the autopilot.
"Don't worry," the pilot says repeatedly in the transcript translated into Russian, before repeating seconds later "Don't do that!" The last words are repeated calls to "Pull up!"
For the last six seconds of the plane's dive, all that can be heard are "inhuman screams," the channel's source said.
The channel suggested -- citing specialists while stressing that this was not the official version -- that the pilot accidentally switched on a stabilising fin at the tail as he tried to pull the plane back to a horizontal position.
With this fin activated, "the plane practically does not react to the pilot's control panel" the channel said.
"The pilots clearly did not understand that the stabiliser was to blame for the steep dive."
The channel said the pilot could have accidentally switched on the button activating the fin due to his reported "chronic fatigue."
The only other possible explanation would be an "unprecedented glitch in the plane's automatic systems," the channel said.
Aircraft control out of sync
Sputnik media, meanwhile, reported on Monday that the Boeing 737-800 could have crashed due to a conflict in the cockpit.
PICTURE: File image of the interior of a Boeing 737-800. CREDIT: Flickr.com/Frans Zwart
According to a source of Russia’s Kommersant newspaper, decoding of the parametric data and voice recorders of the plane revealed that pilots had twice attempted to land the aircraft in automatic mode, but failed to do so due to difficult weather conditions. The pilots eventually decided to come in to land in manual mode.
Experts claim that the crew failed to take characteristics of Boeing 737-800 into consideration, particularly transition from landing to ascend. The pilot on the controls continued to ascend and attempted to pick up speed, while his co-pilot tried to stop gaining altitude. As a result, control of the aircraft was out of sync.
CREDIT: Faisal Akram from Dhaka, Bangladesh, via Wikimedia Commons
The investigation has not yet managed to establish which pilot made a fatal error.
Investigators have launched a criminal probe into whether poor weather, pilot error or a technical fault were behind the crash.
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As I understand the system, you are simply overriding a jammed control column (an unlikely scenario). So any jam in the cabling or in one elevator has no possibility of an override. And even when you do override the other cc (if a cc can jam...), the forces are so high and the control so limited, the aircraft is all but uncontrollable. (Only what training dept said, they have never let me try it after 20 years on the 737.) While other aircraft like the 146 have a complete split between the entire system, with a separated control system to a separated elevator. A much more sensible system, that we could demonstrate on the sim each and every year.
In the case of one pilot pushing and one pulling, on a 737 with a split torque tube, I think the result will be no elevator displacement. The one will cancel the other.
The channel suggested -- citing specialists while stressing that this was not the official version -- that the pilot accidentally switched on a stabilising fin at the tail as he tried to pull the plane back to a horizontal position.
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Bsieker, I did not claim that the elevators split, I said the Capt column is connected to the left elevator and the Fo's to the right. That is to get around any jam in the control runs, not just the column. The torque tube between the elevators will move both together, regardless of which column is used. The cables have springs to allow the surface to move off one input while the other is jammed.
As for what happens if the elevator jams completely, silvertate, you fly it on the stabiliser and thrust. It isn't easy, but it should be completely manageable for any commercial pilot. I have done that too in the NG sim, with a simulated impossible, or at least incredibly unlikely, total jam of all roll and elevator control (both columns) - the aircraft is quite controllable on stab trim and rudder. I even had a go (for play, not assessed) at a loss of all flight controls in the box, not being allowed to touch any flight controls from 400 feet on take off. It was perfectly possible to fly the aircraft on thrust alone (no trim, flap or rudder as well as column), like Sioux City - I was given calm and CAVOK, so didn't have to contend with any weather, but I was surprised at how easy it was to land on the runway centreline, in the touchdown zone, and stop it on the runway on the first (only) attempt. The FO managed to do a controlled landing on the runway too, when he had a go at the same.
Furthermore, the 737Max has the same flight control system, the sole difference being the mechanical aileron - spoiler mixer unit being replaced by a flybywire unit that replicates the mechanical one with less weight. So, the system does meet modern certification requirements and in my opinion has more redundancy than any other airliner in current service.
As for what happens if the elevator jams completely, silvertate, you fly it on the stabiliser and thrust. It isn't easy, but it should be completely manageable for any commercial pilot. I have done that too in the NG sim, with a simulated impossible, or at least incredibly unlikely, total jam of all roll and elevator control (both columns) - the aircraft is quite controllable on stab trim and rudder. I even had a go (for play, not assessed) at a loss of all flight controls in the box, not being allowed to touch any flight controls from 400 feet on take off. It was perfectly possible to fly the aircraft on thrust alone (no trim, flap or rudder as well as column), like Sioux City - I was given calm and CAVOK, so didn't have to contend with any weather, but I was surprised at how easy it was to land on the runway centreline, in the touchdown zone, and stop it on the runway on the first (only) attempt. The FO managed to do a controlled landing on the runway too, when he had a go at the same.
Furthermore, the 737Max has the same flight control system, the sole difference being the mechanical aileron - spoiler mixer unit being replaced by a flybywire unit that replicates the mechanical one with less weight. So, the system does meet modern certification requirements and in my opinion has more redundancy than any other airliner in current service.
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Bsieker, I did not claim that the elevators split, I said the Capt column is connected to the left elevator and the Fo's to the right. That is to get around any jam in the control runs, not just the column. The torque tube between the elevators will move both together, regardless of which column is used. The cables have springs to allow the surface to move off one input while the other is jammed.
You have said this twice but I have no reference for this so-called Capt. column is connected to the left and FO to the right elevator?
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 tocounteract the sustained control column force.
u
You have said this twice but I have no reference for this so-called Capt. column is connected to the left and FO to the right elevator?
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 tocounteract the sustained control column force.
u
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@Organfreak
Often as disturbing as the initial CFIT in pprune post incident analyses!
Some of the responses here convince me that not everyone is familiar with this information.
Last edited by sAx_R54; 29th Mar 2016 at 10:23.
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Since I specifically commented on split elevator, It seemed straightforward to take your's and olasek's comments to refer to the elevators.
Thanks for clearing up that misunderstanding.
Bernd
Thanks for clearing up that misunderstanding.
Bernd
Last edited by bsieker; 29th Mar 2016 at 10:53.
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I could refer to an incident that happened in my airline a couple of years ago to raise another scenario that could lead to a loss of control/CFIT. It did happen on a A319, but about the same thing may also happen on a Boeing.
A go-around was initiated at an altitude below the go-around target altitude, but not that much, and the thrust levers were not set to TOGA. Guess what happened when the AP was re-engaged, with the FD still in approach mode? The aircraft dived, still in IMC, to get back to the glideslope, and control was resumed only when they broke out of the clouds. As far as I remember, a disaster was avoided by a couple hundred feet.
Same thing would happen on a B737 if a go-around (or winshear escape maneuver) is conducted without pushing the TOGA switch (and the fact that the gear was still down at impact, see the videos showing the landing and taxi lights, makes me think that was a WS escape maneuver). And then, it is easy to get confused...
Just another wild guess, based on history...
A go-around was initiated at an altitude below the go-around target altitude, but not that much, and the thrust levers were not set to TOGA. Guess what happened when the AP was re-engaged, with the FD still in approach mode? The aircraft dived, still in IMC, to get back to the glideslope, and control was resumed only when they broke out of the clouds. As far as I remember, a disaster was avoided by a couple hundred feet.
Same thing would happen on a B737 if a go-around (or winshear escape maneuver) is conducted without pushing the TOGA switch (and the fact that the gear was still down at impact, see the videos showing the landing and taxi lights, makes me think that was a WS escape maneuver). And then, it is easy to get confused...
Just another wild guess, based on history...