Unschedule Stab Trim B767
Registered User
Thread Starter
Join Date: Jul 2004
Location: Brasil
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Unschedule Stab Trim B767
Recall Items
Hi everybody!
I do not feel comfortable following the relative CList described on B767 QRH regarding this failure.
I would rather that " Stab Trim Cut Out Switches (both)...Cut Out" were a recall Item when the EICAS MSG " Unschedule Stab Trim" blinked on my panel.
Wich are your opinion?
Good Flights for all.
Victor Lemmi
FO B767 Varig Brazilian Airline
Hi everybody!
I do not feel comfortable following the relative CList described on B767 QRH regarding this failure.
I would rather that " Stab Trim Cut Out Switches (both)...Cut Out" were a recall Item when the EICAS MSG " Unschedule Stab Trim" blinked on my panel.
Wich are your opinion?
Good Flights for all.
Victor Lemmi
FO B767 Varig Brazilian Airline
Join Date: Dec 2001
Location: MVD
Posts: 27
Likes: 0
Received 0 Likes
on
0 Posts
WHY NOT??
In my opinion the qrh procedure is so clear and logic, in order to stop the unconmmanded stabilizer motion you must first shuts off the hydraulic power to the stabilizer control module by placing both the stabilizer trim cut out switches in cut off position, then desengage the autopilot and start to investigate placing one at time to find out wich of them if the case are working not properly.
In my 757's qrh is not a recall item-
bye
In my 757's qrh is not a recall item-
bye
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
For the B777,
STABILIZER CUTTOUT SWITCHES (Both)...................CUTOUT
Do not exceed current airspeed,
are RECALL items in response to the [STABILIZER] EICAS MSG. The associated text describes the condition as - "Uncommanded stabilizer motion detected or stabilizer is inoperative", which would appear to be equivalent to the B767 " Unschedule Stab Trim" message.
Maybe Boeing logic is common across types here, maybe not.
STABILIZER CUTTOUT SWITCHES (Both)...................CUTOUT
Do not exceed current airspeed,
are RECALL items in response to the [STABILIZER] EICAS MSG. The associated text describes the condition as - "Uncommanded stabilizer motion detected or stabilizer is inoperative", which would appear to be equivalent to the B767 " Unschedule Stab Trim" message.
Maybe Boeing logic is common across types here, maybe not.
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
Victor Lemmi,
A post-script to my earlier comments......
I'm not familiar with the B767, but on some earlier Boeing aircraft which I've operated (e.g. B727) the stab brake prevented any further stabilizer activity if the pilot applied opposite elevator force to the stabilizer movement. Once contained in this way, the pilot could then operate the Stabilizer Cut-Out in a more leisurely manner.
IF this is so for the B767 it may explain why operation of the Cut-Out switches is not a recall item.
A post-script to my earlier comments......
I'm not familiar with the B767, but on some earlier Boeing aircraft which I've operated (e.g. B727) the stab brake prevented any further stabilizer activity if the pilot applied opposite elevator force to the stabilizer movement. Once contained in this way, the pilot could then operate the Stabilizer Cut-Out in a more leisurely manner.
IF this is so for the B767 it may explain why operation of the Cut-Out switches is not a recall item.
Join Date: Jul 2000
Location: West
Posts: 399
Likes: 0
Received 0 Likes
on
0 Posts
Control column will interrupt stab trim commands
Boeing 767 Ops Manual Vol 2:
"The control column can be used to interrupt stabilizer trim commands. This feature allows the pilot to quickly stop uncommanded trim changes. The stabilizer trim commands are interrupted if the control column is displaced in the opposing direction."
"The control column can be used to interrupt stabilizer trim commands. This feature allows the pilot to quickly stop uncommanded trim changes. The stabilizer trim commands are interrupted if the control column is displaced in the opposing direction."
Join Date: Oct 2002
Location: Heathrow
Posts: 291
Likes: 0
Received 0 Likes
on
0 Posts
Yes, but if the autopilot is in, by the time you have got the QRH out, found the page etc the trim could be full deflection. I have tried this in the sim and would not like it to happen for real. You can control the aircraft as normal, but no autopilot and a hell of a push or pull is required. So much that my colleague had to help and I couldn't control the forces for more than about 10 mins without a break, arm wobble was a problem too.
If I saw it, I would switch them off regardless of whether it was a memory item (normally I am 100% SOP and it is a memory item in my company). If I were mistaken I could always switch them on again. Not to be confused with the 'stab trim' message though which is different.
If I saw it, I would switch them off regardless of whether it was a memory item (normally I am 100% SOP and it is a memory item in my company). If I were mistaken I could always switch them on again. Not to be confused with the 'stab trim' message though which is different.
Join Date: Apr 2003
Location: Crawley, Surrey
Posts: 92
Likes: 0
Received 0 Likes
on
0 Posts
I agree, in the sim if you do get runaway stab trim it "really runs away" if you don't stop it in time and by then even two portions of the Capt's meal won't be enough to control it or fly the a/c 
Switching off hydraulic supply to the stab trim at the first indication of runaway trim would a very good idea. I do recall though in one of the books by Mike Ray on the B767/B757 where he's totally against the idea of resetting the cutout switches one by one. Wonder why though 
Switching off hydraulic supply to the stab trim at the first indication of runaway trim would a very good idea. I do recall though in one of the books by Mike Ray on the B767/B757 where he's totally against the idea of resetting the cutout switches one by one. Wonder why though
Join Date: Oct 1999
Location: Uhstraylya
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Hmmm, it's not a recall item in our QRH either.
However, in the NNC section of the Checklist Introduction it states,
"The pilot flying may also direct reference procedures to be accomplished by recall if no hazard s created by such action, or if the situation does not permit reference to a checklist."
I would consider this to be one of those such situations and I'd certainly be performing at least the first two items of the checklist by recall (Cutoff Switches and A/P).
Curious that Boeing doesn't standardise it across fleets though...
However, in the NNC section of the Checklist Introduction it states,
"The pilot flying may also direct reference procedures to be accomplished by recall if no hazard s created by such action, or if the situation does not permit reference to a checklist."
I would consider this to be one of those such situations and I'd certainly be performing at least the first two items of the checklist by recall (Cutoff Switches and A/P).
Curious that Boeing doesn't standardise it across fleets though...
