Qantas crew injured after autopilot cut out

[Pearly White]

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 (http://www.canberratimes.com.au/business/aviation/she-felt-the-cabin-floor-drop-qantas-crew-injured-after-autopilot-cut-out-20180314-p4z4c3.html)

[neville_nobody]

Anyone out there know why they changed the autopilot functionality?
Quite unlike Boeing as it would appear they hang onto 1960's technology very tightly.

[maggot]

Anyone out there know why they changed the autopilot functionality?
Quite unlike Boeing as it would appear they hang onto 1960's technology very tightly.

On the 767 there was a deactivated CWS and it was 'very dangerous' according to some checkies I asked about it. No real explanation given.

Now it's deactivated on the 737? Hmmmm I presume the crews were informed? It worked very well in that manner.

[GA Driver]

CWS on plenty of aeroplane autopilots. 210/Barons/DHC8 right through to 767 by the looks of it! Not sure whats dangerous.

[porch monkey]

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.

[RickNRoll]

Link to report.

https://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-030/

[Centaurus]

CWS on plenty of aeroplane autopilots

Because its stick force is somewhat greater than normal hand flying requirements, CWS is useful if for any reason manual flying is needed at high altitude or in severe turbulence. It minimises the possibility of over-controlling by a ham-fisted pilot. In fact, the B737 Supplementary Procedures page for Severe Turbulence include selection of CWS

[Lookleft]

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.

[Capn Bloggs]

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.
A revision to the Boeing Systems Description in the FCOM surely would have aroused everybody to the mod.

Hit Altitude Hold.

[Lookleft]

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.

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.

Which suggests that the training does not reflect what is written in the manuals:

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.

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?

[Berealgetreal]

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.

[Capn Bloggs]

The common practice of flight crews to prevent an overspeed was not a documented Qantas or Boeing procedure.
So what was the "documented procedure"? The report should have given those Boeing and Qantas') so the reader can see what the PF did differently here.

[Lookleft]

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.

[framer]

undocumented procedure
not everything is a procedure. The technique of transitioning the AP into CWS by overiding physically was a technique that utilised the operating design of the system. 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. More of a communication issue than a training and standards issue in my opinion.

[Basil]

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.

[maggot]

The transition to CWS in this sense is smooth
But to AP disc, not so much

[Lookleft]

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.

The report doesn't state it but were line crews told that the CWS-P function had been disabled? If it was trained for in the initial type rating I would have thought that it was a procedure that was incorporated in the syllabus. If it wasn't a procedure then why was it part of the initial type rating?

[framer]

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.

[sleeve of wizard]

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.

[Beer Baron]

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.

[ga_trojan]

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.

Yet CASA consider Fail Operational and Fail Passive almost like an entire new endorsement!

[Servo]

Does Qantas have FDAP?

Would it be possible that it was a factor in the pilot's reaction?

[framer]

What is FDAP?

[glekichi]

How often are pilots reacting similarly based on actual fear of danger to the aircraft vs not wanting paperwork/questions asked due to the overspeed?
I’ve always had the feeling that too often pilots are doing something that actually complicates the situation in order to avoid the latter. This is a classic example imho.

[maggot]

How often are pilots reacting similarly based on actual fear of danger to the aircraft vs not wanting paperwork/questions asked due to the overspeed?
I’ve always had the feeling that too often pilots are doing something that actually complicates the situation in order to avoid the latter. This is a classic example imho.

I see your point
But I'd say in my time on the 737 it's was pretty normal to gently respond that way (with CWS), really no dramas and smooth.

[Lookleft]

Until they took the CWS function away and didn't tell the pilots!:ugh:

[maggot]

Exactly


12345

[Bug Smasher Smasher]

They did tell the pilots as the update to autopilot logic was rolled out. Not all of them appreciated the implications though and some to this day still don’t.

[No Idea Either]

At the other large 737 operator in OZ we were told well in advance about the change and its implications. Don’t get me wrong, I too used to do the old gentle back pressure into CWS when approaching Vmo, but haven’t since for this exact reason......but having said that, we too have had a similar event as well.

[framer]

They did tell the pilots as the update to autopilot logic was rolled out. Not all of them appreciated the implications though and some to this day still don’t.
They were probably too busy doing online courses on how to stay safe on the tarmac, how to address your co workers, and how to keep e-safe, to take much notice of a pesky operational memo.

[framer]

I read on ATSB site the exact same thing happened n a Virgin 737 into Adelaide on the 13th Sept 17.
If two crews from two seperate Airlines in this fairly small aviation community have seriously injured cabin crew as a result of a software change to the aircraft, will the ATSB find the reason the crews were not aware of the risks? The ball has obviously been dropped somewhere and the fact that seperate crews from seperate airlines have been caught out suggests that the mistake was made further up the food chain than operational crew.
Training Departments? Airline Ops management? CASA?

[maggot]

I read on ATSB site the exact same thing happened n a Virgin 737 into Adelaide on the 13th Sept 17.
If two crews from two seperate Airlines in this fairly small aviation community have seriously injured cabin crew as a result of a software change to the aircraft, will the ATSB find the reason the crews were not aware of the risks? The ball has obviously been dropped somewhere and the fact that seperate crews from seperate airlines have been caught out suggests that the mistake was made further up the food chain than operational crew.
Training Departments? Airline Ops management? CASA?

Up the food chain for sure, Mr reason!

And why the change at all?

[Kiwiconehead]

CWS on plenty of aeroplane autopilots. DHC8

Dash 8 doesnt have CWS, it has a sync button which when pressed and held disengages the vertical mode allowing the pilot to re-datum the target IAS or VS. When the sync button is released the vertical mode reengages. It also works with just the flight director engaged.