Bae 146 decompression ???
Joined: Sep 2006
Posts: 1,312
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From: back of the crew bus
I am pretty sure the limitation is still in effect
From memory, there were quite a few issues surrounding that event, and the crew were at least partly to blame for what happened. There is a pretty good instructional video about it, that was made by the airline after the event.
Joined: Dec 2002
Posts: 2,775
Likes: 353
From: UK
Engine rollback – ‘the crew(s) were partly to blame’.
With hindsight this view is bit harsh. The icing phenomenon was previously unknown and only after the statistics from events was it associated with very large Cbs. More recently Boeing and Airbus have encountered problems.
There were some human aspects, particularly after the initial warnings not to fly anywhere near Cbs, but also there were more general circumstances. Many of the incident aircraft were relatively light, thus cruised at a (relatively) higher altitude; crews believed that no return on radar was the same as no threat due to mismanagement/misunderstanding of WXR – corner cutting near Cbs, and some of the engine air-bleed tolerances were at minimum - maintenance.
In at least one event a crew ‘induced’ depressurisation (four engines shut down – not in Oz), presented an interesting dilemma between descending relatively fast (for lack of O2/pressure), pausing at FL200 to obtain a relight, or to reduce altitude loss to maximise the much need overwater glide range. Again, with hindsight, a compromise at FL200 provided a balance between risks and needs; at least the engines relit.
In many aircraft, crews over reacting to a depressurisation warning; pilots are taught the depressurisation drill in association with an emergency descent, thus they become automatically sequential. Whereas in reality after donning the O2 masks, there is time to check the actual cabin pressure and cabin rate, and possibly some fault diagnosis.
The more experienced 146 Captains would look at the overhead panel and check the outflow valves, which under manual control had a sluggish response and lacked feed back of the selection except for air pressure on the ears. Many pilots did not have opportunity to gain this knowledge from annual airtests (now discontinued), and the simulator was ineffective.
Depressurisation; a quick response required for O2 masks, no rush to descend … check … then act accordingly.
With hindsight this view is bit harsh. The icing phenomenon was previously unknown and only after the statistics from events was it associated with very large Cbs. More recently Boeing and Airbus have encountered problems.
There were some human aspects, particularly after the initial warnings not to fly anywhere near Cbs, but also there were more general circumstances. Many of the incident aircraft were relatively light, thus cruised at a (relatively) higher altitude; crews believed that no return on radar was the same as no threat due to mismanagement/misunderstanding of WXR – corner cutting near Cbs, and some of the engine air-bleed tolerances were at minimum - maintenance.
In at least one event a crew ‘induced’ depressurisation (four engines shut down – not in Oz), presented an interesting dilemma between descending relatively fast (for lack of O2/pressure), pausing at FL200 to obtain a relight, or to reduce altitude loss to maximise the much need overwater glide range. Again, with hindsight, a compromise at FL200 provided a balance between risks and needs; at least the engines relit.
In many aircraft, crews over reacting to a depressurisation warning; pilots are taught the depressurisation drill in association with an emergency descent, thus they become automatically sequential. Whereas in reality after donning the O2 masks, there is time to check the actual cabin pressure and cabin rate, and possibly some fault diagnosis.
The more experienced 146 Captains would look at the overhead panel and check the outflow valves, which under manual control had a sluggish response and lacked feed back of the selection except for air pressure on the ears. Many pilots did not have opportunity to gain this knowledge from annual airtests (now discontinued), and the simulator was ineffective.
Depressurisation; a quick response required for O2 masks, no rush to descend … check … then act accordingly.
Joined: Oct 2001
Posts: 3,832
Likes: 115
From: UK
The other quadruple hush (caused by rollback) happened to a Flip I Lino crew (JP was the captain). They got the first engine running again about 3500 ft above the sea north of Brunei and finally made it to Singapore with three engines running.
Like the Oz crew, they were flying close to large Cb activity at high altitude.
The interesting thing (to me) was that both crews were cruising with the TMS in TGT/SYNC mode.
Now, we abandoned this mode of the TMS as worse than useless right at the beginning in 1987 for it was a contradiction in terms. (In effect, it only regulated TGT on the master engine and allowed the other three to float whilst regulating SYNC).
The Flip I Lino crews were initially trained by us in UK and were warned about using TGT/SYNC. However, whilst they were waiting for their aircraft to be delivered, they were given further training in OZ.
I have often wondered, if having one engine roll back in icing conditions and having TGT/SYNC selected, dragged the other three back with it?
In any event, all the engines have since have been modified and I am now retired so I suppose I don't give a stuff one way or the other!
Like the Oz crew, they were flying close to large Cb activity at high altitude.
The interesting thing (to me) was that both crews were cruising with the TMS in TGT/SYNC mode.
Now, we abandoned this mode of the TMS as worse than useless right at the beginning in 1987 for it was a contradiction in terms. (In effect, it only regulated TGT on the master engine and allowed the other three to float whilst regulating SYNC).
The Flip I Lino crews were initially trained by us in UK and were warned about using TGT/SYNC. However, whilst they were waiting for their aircraft to be delivered, they were given further training in OZ.
I have often wondered, if having one engine roll back in icing conditions and having TGT/SYNC selected, dragged the other three back with it?
In any event, all the engines have since have been modified and I am now retired so I suppose I don't give a stuff one way or the other!
Fleet Manager
Joined: Apr 2001
Aviation Qualifications: ATPL
Posts: 7,448
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From: various places .....
the crew were at least partly to blame for what happened
I think that you need to provide some evidence for your contention.
As far as I am aware, Phil was considered to have done a pretty good job at the time.
I think that you need to provide some evidence for your contention.
As far as I am aware, Phil was considered to have done a pretty good job at the time.
