737-800 Autothrottle Question
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737-800 Autothrottle Question
Hello all,
The other day I was taxiing out and when cleared to position I went to engage the Autothrottle and it wouldn't arm.
-FD's were on.
-TOGA Takeoff
-CDU preflight was complete ie.ZFW and TO weight were entered.
-Unpressurized Takeoff after Deice.
I've asked some line pilots and only one person had that happen and suggested it could be temperature related, but wasn't sure. -15c at the time. Could it have something to do with the Isolation Valve being closed?
Through about 3000AGL after reconfiguring the Bleed Panel, the Autothrottle armed and worked the remainder of the flight.
Thanks for your time.
The other day I was taxiing out and when cleared to position I went to engage the Autothrottle and it wouldn't arm.
-FD's were on.
-TOGA Takeoff
-CDU preflight was complete ie.ZFW and TO weight were entered.
-Unpressurized Takeoff after Deice.
I've asked some line pilots and only one person had that happen and suggested it could be temperature related, but wasn't sure. -15c at the time. Could it have something to do with the Isolation Valve being closed?
Through about 3000AGL after reconfiguring the Bleed Panel, the Autothrottle armed and worked the remainder of the flight.
Thanks for your time.
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B737-900er and Framer,
Thanks for the replies. It was snowing at the time and the previous flight picked up a lot of ice which required a prolonged de-ice. Airplane was fully serviceable with no MEL's at the time.
I had talked to Maintenance at destination and they had no suggestions specially with a serviceable airplane. Maybe the MCP solenoid switch is becoming intermittent.
Thanks.
Thanks for the replies. It was snowing at the time and the previous flight picked up a lot of ice which required a prolonged de-ice. Airplane was fully serviceable with no MEL's at the time.
I had talked to Maintenance at destination and they had no suggestions specially with a serviceable airplane. Maybe the MCP solenoid switch is becoming intermittent.
Thanks.
I have had a dirty weight on wheels switch cause a partial air/ground logic failure. The first thing that happened was the Autothrottle flicked off. Maybe in your case it was a bit sticky due ice?
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Autothrottle engagement on runway
Usually it occurs when airspeed is in excess of set value, 747 was 50kts. Taxi onto runway with highspeed entry and say 30kts of headwind you won't be able to engage the auto throttle until after T/O .
Last edited by tony64peter; 25th Nov 2012 at 01:45.
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I think without OAT the preflight is not complete, I had a couple of times problem with A/T too and still unknown the cause, but I was able to engage it during climb.
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Will you pls explain the 'unpressurised takeoff' due de-ice? That's a 1st for me
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It's to prevent unpleasant fumes from de-icing fluid entering the cabin via the APU.
Quote from the 737 AFM:
Quote from the 737 AFM:
Note: If Bleeds OFF take-off performance is required after de-icing, perform the ‘Unpressurized’ Take-off procedure, and ensure APU BLEED air switch is OFF.
Per Ardua ad Astraeus
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It's to prevent unpleasant fumes from de-icing fluid entering the cabin via the APU.
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Further to my last the speed is 60kts. If your practice is to stand the thrust levers up, stabilise engines,release brakes, then push TOGA switches, often in strong headwinds, more than 60kts IAS will be indicated.You will not get N1 annunciation as there not enough time for the A/T system to set the N1 before 80kts. ie THRUSTHOLD. So manual setting is required.More common on bigger aircraft.
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172 Driver,
CDU Preflight was completed for sure and we had a target N1 as I remember including this value in my breifing. However, I cant recall if the OAT was entered. But if the preflight cannot be completed without entering an OAT it must have been entered. Could possibly be one of those once in a while things or the MCP Autothrottle switch is about to go U/S.
As for unpressurized T/O after de-ice, our company's SOP is to perform this procedure(found in FCOM 1 Supplementary) to avoid fumes entering the cabin. Might not necessarily be a Boeing procedure.
Thanks all.
CDU Preflight was completed for sure and we had a target N1 as I remember including this value in my breifing. However, I cant recall if the OAT was entered. But if the preflight cannot be completed without entering an OAT it must have been entered. Could possibly be one of those once in a while things or the MCP Autothrottle switch is about to go U/S.
As for unpressurized T/O after de-ice, our company's SOP is to perform this procedure(found in FCOM 1 Supplementary) to avoid fumes entering the cabin. Might not necessarily be a Boeing procedure.
Thanks all.