B757 Leading Edge Slat Disagree Reset
Thread Starter
Join Date: Jan 2006
Location: All over the World
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
B757 Leading Edge Slat Disagree Reset
Recently some pilots in my company have "rediscovered" an old Boeing "approved" technique for resetting a leading (or trailing) edge slat (or flap) disagree. It involves selecting and then deselecting the appropriate (or both) Alternate Flap Switches and thereby resetting the timer on the motor and reactivating that motor.
My understanding of the system is that when the flaps are selected, there is a certain amount of time (?30 seconds?) for the flaps or slats to get into that position. If the flaps aren't in the selected position in the allotted time, then the hydraulic motors are shut down and you get the Flap/Slat Disagree message. Apparently selecting and then deselecting the appropriate switch resets the timer on the motor and allows it to activate again and reposition the flaps/slats as selected, thus avoiding the need to do the QRH checklist.
This all sounds a little suspect to me.
My Questions are:
1. Did Boeing ever have a procedure like this?
2. If not, did they approve it?
3. If they subsequently withdrew this procedure, why?
4. Is this a reasonable procedure?
5. And, most importantly, where can I find an official Boeing (or otherwise) comment on it.
Any comment?
My understanding of the system is that when the flaps are selected, there is a certain amount of time (?30 seconds?) for the flaps or slats to get into that position. If the flaps aren't in the selected position in the allotted time, then the hydraulic motors are shut down and you get the Flap/Slat Disagree message. Apparently selecting and then deselecting the appropriate switch resets the timer on the motor and allows it to activate again and reposition the flaps/slats as selected, thus avoiding the need to do the QRH checklist.
This all sounds a little suspect to me.
My Questions are:
1. Did Boeing ever have a procedure like this?
2. If not, did they approve it?
3. If they subsequently withdrew this procedure, why?
4. Is this a reasonable procedure?
5. And, most importantly, where can I find an official Boeing (or otherwise) comment on it.
Any comment?
Buttonpusher
This reminds me of a circuit breaker procedure, back in the old days you reset it a couple of times and if it stayed in life was good. Today we don't reset a popped breaker, due to the possibility of fire ...Why screw with the motors if they didn't work as advertised ? You have no way of knowing if the motors are malfunctioning, maybe even causing a fire hazard where you have no protection...I would follow sop and land "as is". Besides what would you say at the Board of Inquiry ? Well I had this idea.....
Join Date: Apr 2005
Location: Stockholm Sweden
Age: 74
Posts: 569
Likes: 0
Received 0 Likes
on
0 Posts
Cycling the Flap/Slat alternate switches resets the FSEUs. As a ground engineer it is the first thing I do with flap and slat problems. So I looked in the FIM to find a reference for this and its not mentioned. So now I wonder if it is promulgated anywhere? Will continue to investigate
Thread Starter
Join Date: Jan 2006
Location: All over the World
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Thanks, Steve. I await your answer.
FLCH, what you are talking about is airmanship and is, in many peoples minds, a matter of judgement on the day. I agree with you totally, and with even more reasons, but I have tried those arguements and they have had no effect. Now I need some sort of reference on Boeing letterhead which states their position clearly.
FLCH, what you are talking about is airmanship and is, in many peoples minds, a matter of judgement on the day. I agree with you totally, and with even more reasons, but I have tried those arguements and they have had no effect. Now I need some sort of reference on Boeing letterhead which states their position clearly.
Join Date: Jan 2005
Location: Europe
Age: 63
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
I´m aware of this technic. If the flap handle is left out of the slot (and only IF that is the reason) for prolonged time, it is only logical to do this. This is because you KNOW the reason for this message. If in ANY doubt don´t.
Join Date: May 2003
Location: Abu Dhabi
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
Not sure about the first three questions but the QRH is the Boeing approved procedure. If receiving an EICAS message ‘Flaps/Slats Disagree’, you are required to complete the appropriate checklist from the QRH as there maybe a very good reason why the Flaps/Slats failed to reach the selected position in the required time. Why complicate things keep it simple if you can, only my opinion of course. Most companies require that from after engine start to engine shut down you comply with any EICAS message and complete the required QRH checklist!
If on the ground and you select the flap handle to a take off flap position and it is not seated correctly in the detent you will receive a flap disagree message. On the 757 (the 757s I used to operate)you needed to reset the PDUs (alternate switches need to be recycled) but on the 767 you only need to position the flap lever in the detent to remove the message, if my memory serves me correctly.
If on the ground and you select the flap handle to a take off flap position and it is not seated correctly in the detent you will receive a flap disagree message. On the 757 (the 757s I used to operate)you needed to reset the PDUs (alternate switches need to be recycled) but on the 767 you only need to position the flap lever in the detent to remove the message, if my memory serves me correctly.
Join Date: Jul 2000
Location: West
Posts: 399
Likes: 0
Received 0 Likes
on
0 Posts
L.A.
It is specifically contrary to Boeing. The following was recently emphasized to us:
"Most flap/slat problems are
straightforward, result in little or no adverse
control issues, and are easily resolved by
reference to the QRH. And, just for the “old
timers” – there is NO LONGER a “free punch”
to clear a FLAP DISAGREE message! Just use
the correct checklist. (New guys, forget you read
this!)"
It is specifically contrary to Boeing. The following was recently emphasized to us:
"Most flap/slat problems are
straightforward, result in little or no adverse
control issues, and are easily resolved by
reference to the QRH. And, just for the “old
timers” – there is NO LONGER a “free punch”
to clear a FLAP DISAGREE message! Just use
the correct checklist. (New guys, forget you read
this!)"
