Qantas crew injured after autopilot cut out
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Qantas crew injured after autopilot cut out
A Qantas flight attendant broke her leg and another suffered numerous injuries when their aircraft's autopilot unexpectedly disengaged as it descended into Canberra Airport last year.
The Australian Transport Safety Bureau's investigation into the incident has found a modification made to the Boeing 737-8 meant the pilot's attempt to stop the aircraft going too fast inadvertently triggered an abrupt change in speed and angle.
'She felt the cabin floor drop': Qantas crew injured after autopilot cut out
The Australian Transport Safety Bureau's investigation into the incident has found a modification made to the Boeing 737-8 meant the pilot's attempt to stop the aircraft going too fast inadvertently triggered an abrupt change in speed and angle.
'She felt the cabin floor drop': Qantas crew injured after autopilot cut out
Now it's deactivated on the 737? Hmmmm I presume the crews were informed? It worked very well in that manner.
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It hasn’t been removed, the functionality has been changed, in response to some inadvertent reversion incidents. It’s a useful tool in some circumstances, it isn’t dangerous in and of itself. My company modified the response training for inadvertent overspeeds some time ago as a result of Boeing’s changes. We had a similar incident last year for the same reasons.
CWS on plenty of aeroplane autopilots
From the report the crew did what was taught and that they had a reasonable expectation that the aircraft would respond in a predictable manner. Why would crews not be told about the removal of the CWS function? This type of incident has occurred with both Airbus and Boeing yet the airlines don't want to learn from them. Airbus reinforced the need to use the speedbrake to control an overspeed several years ago. Cabin crew were being injured because both pilots were pulling back on the side stick with the Airbus logic summing the totals of the individual inputs. There appears to be an attitude that if it hasn't happened to us then there is nothing to worry about.
There is nothing in the report that suggests that line pilots were advised that the CWS-P function had been removed and of the possible consequence. What were the Fleet Managers doing? If their pilots are trained to use it to control an overspeed then it is bordering on negligence to not tell the pilots it had been disabled. If the Fleet Managers were not aware, then there has been a significant breakdown of communication between the engineering departments and the flight operations departments which is also a concern.
There is nothing in the report that suggests that line pilots were advised that the CWS-P function had been removed and of the possible consequence. What were the Fleet Managers doing? If their pilots are trained to use it to control an overspeed then it is bordering on negligence to not tell the pilots it had been disabled. If the Fleet Managers were not aware, then there has been a significant breakdown of communication between the engineering departments and the flight operations departments which is also a concern.
If the Fleet Managers were not aware, then there has been a significant breakdown of communication between the engineering departments and the flight operations departments which is also a concern.
Hit Altitude Hold.
Actually the answer to my question is in the report but it still raises questions about what was being taught in the sim and on line.
Which suggests that the training does not reflect what is written in the manuals:
So the question then is why did 737 fleet management allow for the training of and the common practice of a technique that was not a documented Qantas or Boeing procedure?
The common practice of flight crews to prevent an overspeed was not a documented Qantas or Boeing procedure. As a result, the potential consequence of this practice was not considered when the autopilot was modified.
Qantas advised the ATSB that it was common practice for its B737 flight crews to manage an impending overspeed by applying control column force to override the autopilot. The expected outcome of this action was for the autopilot to revert to ‘control wheel steering-pitch’ (CWS-P)5
mode, and raise the aircraft’s nose. According to VZZ’s first officer, the technique was part of initial B737 type rating training and line training. The captain also confirmed that this technique was commonly practiced.
mode, and raise the aircraft’s nose. According to VZZ’s first officer, the technique was part of initial B737 type rating training and line training. The captain also confirmed that this technique was commonly practiced.
Removal of AP to CWS via control column is a total pain.
I heard it was related to a low hour pilot going into cws when adjusting seat while capt was in the lav. could be a bs story however.
I heard it was related to a low hour pilot going into cws when adjusting seat while capt was in the lav. could be a bs story however.
The common practice of flight crews to prevent an overspeed was not a documented Qantas or Boeing procedure.
I think Bloggsy the report is suggesting that the PF did what he/she/they were trained to do but,whether by accident or design, it is stating that Qantas allowed an undocumented procedure to be taught and then flown on line operations. It reminds me of the "TOGA tap" incident in Jetstar where an undocumented procedure was introduced into line training and it lay as a latent threat.
undocumented procedure
Only ever came across CWS in the TriStar. Didn't like it and, after playing with it once or twice, never used it again. If some pilots found it useful then fine but I wouldn't have been happy to have been told to use it as an SOP.
The thought of hauling on the control column until (unexpectedly) the a/p disengages - bally heck!
p.s. I do appreciate that, on this occasion, it had been disabled.
The thought of hauling on the control column until (unexpectedly) the a/p disengages - bally heck!
p.s. I do appreciate that, on this occasion, it had been disabled.
The transition to CWS in this sense is smooth
But to AP disc, not so much
But to AP disc, not so much
The problem in my mind, after reading the report, is that line crew didn’t have it in the front of their minds that the operating design of the system had recently changed.
My take on that LL is that it is a method of controlling the aircraft, not a procedure.
To try and expand on that a bit; there is a ‘procedure ‘ for flying a circuit, but that procedure doesn’t specify exactly how you control the aircraft, do you do it with the AP engaged? Flying manually? In CWS pitch and roll? Just CWS roll? I think this is similar, not a procedure, just a method of carrying out a procedure, and that when the functionality of the machine changed, the crew needed to be briefed on it and informed of any fish hooks associated with the new functionality. This may well have happened, I don’t know, but if it did I think the report would probably have mentioned the method of promulgation.
To try and expand on that a bit; there is a ‘procedure ‘ for flying a circuit, but that procedure doesn’t specify exactly how you control the aircraft, do you do it with the AP engaged? Flying manually? In CWS pitch and roll? Just CWS roll? I think this is similar, not a procedure, just a method of carrying out a procedure, and that when the functionality of the machine changed, the crew needed to be briefed on it and informed of any fish hooks associated with the new functionality. This may well have happened, I don’t know, but if it did I think the report would probably have mentioned the method of promulgation.
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From the original B737 FCTM
Overspeed
Overspeed
VMO/MMO is the airplane maximum certified operating speed and should not be exceeded intentionally. However, crews can occasionally experience an inadvertent overspeed. Airplanes have been flight tested beyond VMO/MMO to ensure smooth pilot inputs will return the airplane safely to the normal flight envelope.
737-300 - 737-500
During cruise at high altitude, wind speed or direction changes may lead to overspeed events. There are some conditions that are beyond the capability of the autothrottle system to prevent short term overspeeds.
737-600 - 737-900ER
During cruise at high altitude, wind speed or direction changes may lead to overspeed events. Although autothrottle logic provides for more aggressive control of speed as the airplane approaches VMO or MMO, there are some conditions that are beyond the capability of the autothrottle system to prevent short term overspeeds.
When correcting an overspeed during cruise at high altitude, avoid reducing thrust to idle which results in slow engine acceleration back to cruise thrust and may result in over-controlling the airspeed or a loss of altitude. If autothrottle corrections are not satisfactory, deploy partial speedbrakes slowly until a noticeable reduction in airspeed is achieved. When the airspeed is below VMO/MMO, retract the speedbrakes at the same rate as they were deployed. The thrust levers can be expected to advance slowly to achieve cruise airspeed; if not, they should be pushed up more rapidly.During descents at or near VMO/MMO, most overspeeds are encountered after the autopilot initiates capture of the VNAV path from above or during a level-off when the speedbrakes were required to maintain the path. In these cases, if the speedbrakes are retracted during the level-off, the airplane can momentarily overspeed. During descents using speedbrakes near VMO/MMO, delay retraction of the speedbrakes until after VNAV path or altitude capture is complete. Crews routinely climbing or descending in windshear conditions may wish to consider a 5 to 10 knot reduction in climb or descent speeds to reduce overspeed occurrences. This will have a minimal effect on fuel consumption and total trip time.
When encountering an inadvertent overspeed condition, crews should leave the autopilot engaged unless it is apparent that the autopilot is not correcting the overspeed. However, if manual inputs are required, disengage the autopilot. Be aware that disengaging the autopilot to avoid or reduce the severity of an inadvertent overspeed may result in an abrupt pitch change.
During climb or descent, if VNAV or LVL CHG pitch control is not correcting the overspeed satisfactorily, switching to the V/S mode temporarily may be helpful in controlling speed. In the V/S mode, the selected vertical speed can be adjusted slightly to increase the pitch attitude to help correct the overspeed. As soon as the speed is below VMO/MMO, VNAV or LVL CHG may be re-selected.
Note: Anytime VMO/MMO is exceeded, the maximum airspeed should be noted in the flight log.
Overspeed
Overspeed
VMO/MMO is the airplane maximum certified operating speed and should not be exceeded intentionally. However, crews can occasionally experience an inadvertent overspeed. Airplanes have been flight tested beyond VMO/MMO to ensure smooth pilot inputs will return the airplane safely to the normal flight envelope.
737-300 - 737-500
During cruise at high altitude, wind speed or direction changes may lead to overspeed events. There are some conditions that are beyond the capability of the autothrottle system to prevent short term overspeeds.
737-600 - 737-900ER
During cruise at high altitude, wind speed or direction changes may lead to overspeed events. Although autothrottle logic provides for more aggressive control of speed as the airplane approaches VMO or MMO, there are some conditions that are beyond the capability of the autothrottle system to prevent short term overspeeds.
When correcting an overspeed during cruise at high altitude, avoid reducing thrust to idle which results in slow engine acceleration back to cruise thrust and may result in over-controlling the airspeed or a loss of altitude. If autothrottle corrections are not satisfactory, deploy partial speedbrakes slowly until a noticeable reduction in airspeed is achieved. When the airspeed is below VMO/MMO, retract the speedbrakes at the same rate as they were deployed. The thrust levers can be expected to advance slowly to achieve cruise airspeed; if not, they should be pushed up more rapidly.During descents at or near VMO/MMO, most overspeeds are encountered after the autopilot initiates capture of the VNAV path from above or during a level-off when the speedbrakes were required to maintain the path. In these cases, if the speedbrakes are retracted during the level-off, the airplane can momentarily overspeed. During descents using speedbrakes near VMO/MMO, delay retraction of the speedbrakes until after VNAV path or altitude capture is complete. Crews routinely climbing or descending in windshear conditions may wish to consider a 5 to 10 knot reduction in climb or descent speeds to reduce overspeed occurrences. This will have a minimal effect on fuel consumption and total trip time.
When encountering an inadvertent overspeed condition, crews should leave the autopilot engaged unless it is apparent that the autopilot is not correcting the overspeed. However, if manual inputs are required, disengage the autopilot. Be aware that disengaging the autopilot to avoid or reduce the severity of an inadvertent overspeed may result in an abrupt pitch change.
During climb or descent, if VNAV or LVL CHG pitch control is not correcting the overspeed satisfactorily, switching to the V/S mode temporarily may be helpful in controlling speed. In the V/S mode, the selected vertical speed can be adjusted slightly to increase the pitch attitude to help correct the overspeed. As soon as the speed is below VMO/MMO, VNAV or LVL CHG may be re-selected.
Note: Anytime VMO/MMO is exceeded, the maximum airspeed should be noted in the flight log.
A complicating factor is that there are two types of mode control panels on the QF737 fleet from different manufacturers. The change to the CWS reversion only applied to one of the models and even then only to the aircraft that had had the update applied.
So some behave one way and some behave the other.
So some behave one way and some behave the other.