haughtney1
13th Feb 2010, 03:19
Had an interesting experience a few weeks back...
Got airborne (full pwr T/O) and at about 1000' we hit the wake of a 777 ahead of us..then called for CLB THR & VNAV, the PNF selected both modes...however the thrust mode went to CON...(all this happened in the space of about 2 seconds) then just as I saw the CON mode...I noticed an EGT temp exceedance of 8C..so disconnected the auto throttle..and bought the thrust lever back slightly, the EGT temp then jumped back to more normally expected values.
A quick check of the indications, and we both were satisfied that it was mayby a slight airflow disruption thanks to the wake encounter...so I matched the thrust levers accelerated, cleaned up..and asked for CLB thrust again...but no...the thrust mode intially accepted CLB..but then returned to CON.
At this point it was still very busy so we decided to climb in manual thrust and sort it out at top of climb.
We got levelled off at an intermediate level for a couple of minutes so decided to try and sort the problem out.......a quick scan of the FMC CLB page showed that the mode had defaulted to VREF+80 CON CLB.....
ClB DIR cleared this, and hey presto...when we selected CLB on the TMSP, that mode was accepted, and we could use VNAV..life was good again.
All I can think of is that the EGT exceedance is viewed as a failure mode, and the Pegasus FMC "helpfully" defaults to the VREF+80 CON CLB mode, and allows you to climb single engine at this speed...but thats a guess.
I've had minor EGT exceedances before (full load out of Jedda etc) and never seen this before and have never seen it in any manuals I've reviewed before or since..which is to say..its probably staring me in the face.
Come on guru's over to you:ok:
Got airborne (full pwr T/O) and at about 1000' we hit the wake of a 777 ahead of us..then called for CLB THR & VNAV, the PNF selected both modes...however the thrust mode went to CON...(all this happened in the space of about 2 seconds) then just as I saw the CON mode...I noticed an EGT temp exceedance of 8C..so disconnected the auto throttle..and bought the thrust lever back slightly, the EGT temp then jumped back to more normally expected values.
A quick check of the indications, and we both were satisfied that it was mayby a slight airflow disruption thanks to the wake encounter...so I matched the thrust levers accelerated, cleaned up..and asked for CLB thrust again...but no...the thrust mode intially accepted CLB..but then returned to CON.
At this point it was still very busy so we decided to climb in manual thrust and sort it out at top of climb.
We got levelled off at an intermediate level for a couple of minutes so decided to try and sort the problem out.......a quick scan of the FMC CLB page showed that the mode had defaulted to VREF+80 CON CLB.....
ClB DIR cleared this, and hey presto...when we selected CLB on the TMSP, that mode was accepted, and we could use VNAV..life was good again.
All I can think of is that the EGT exceedance is viewed as a failure mode, and the Pegasus FMC "helpfully" defaults to the VREF+80 CON CLB mode, and allows you to climb single engine at this speed...but thats a guess.
I've had minor EGT exceedances before (full load out of Jedda etc) and never seen this before and have never seen it in any manuals I've reviewed before or since..which is to say..its probably staring me in the face.
Come on guru's over to you:ok: