737 High speed rejected take off actions and AT disengage action
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737 High speed rejected take off actions and AT disengage action
Part of the drill for a high speed rejected take off on the 737 series is immediate thrust lever closure. The FCTM states:
"If the takeoff is rejected before the THR HLD annunciation, the AT should be disengaged as the thrust levers are moved to idle. If the AT is not disengaged, the thrust levers advance to to the selected take off thrust position when released. After THR HLD is annunciated, the thrust levers, when retarded, remain in idle. For procedural consistency, disengaged the AT for all rejected take offs.
From observation of high speed rejected takeoffs in simulator sessions, we often see the pilot rapidly actuating the autothrottle disconnect switch in the thrust lever handle, as a momentary first action before closing the thrust levers.
This slight delay of about 1-2 seconds before thrust levers are closed (even though the perception is of simultaneous action of AT disengage and thrust lever closure) extends the stopping distance by 2-300 feet which could be critical on a runway limiting take off.
This habit may be ingrained because of the normal procedure of disconnecting the AT before closing the thrust lever of a failed engine in flight.
It is worth thinking about - especially if the runway is wet and the stopping distance already increased. It is better to fully close the thrust levers first (high speed reject) and only then disconnect the AT switch (for procedural consistency as per FCTM). Comments invited but next time you are in the simulator have a close look. Every split second delay in thrust lever closure during a high speed rejected take off means extra stopping distance.
"If the takeoff is rejected before the THR HLD annunciation, the AT should be disengaged as the thrust levers are moved to idle. If the AT is not disengaged, the thrust levers advance to to the selected take off thrust position when released. After THR HLD is annunciated, the thrust levers, when retarded, remain in idle. For procedural consistency, disengaged the AT for all rejected take offs.
From observation of high speed rejected takeoffs in simulator sessions, we often see the pilot rapidly actuating the autothrottle disconnect switch in the thrust lever handle, as a momentary first action before closing the thrust levers.
This slight delay of about 1-2 seconds before thrust levers are closed (even though the perception is of simultaneous action of AT disengage and thrust lever closure) extends the stopping distance by 2-300 feet which could be critical on a runway limiting take off.
This habit may be ingrained because of the normal procedure of disconnecting the AT before closing the thrust lever of a failed engine in flight.
It is worth thinking about - especially if the runway is wet and the stopping distance already increased. It is better to fully close the thrust levers first (high speed reject) and only then disconnect the AT switch (for procedural consistency as per FCTM). Comments invited but next time you are in the simulator have a close look. Every split second delay in thrust lever closure during a high speed rejected take off means extra stopping distance.
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As you said, no need to waste time by first disconnecting A/T before slamming the thrust levers back and raising the reverse levers... A/T wouldn't be able to move the thrust levers forward once the reverse levers are up. That's how it would play out on the 747. 
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On the 737 it is very easy to close the thrust levers and disconnect the A/T simultaneously. If you see something else in the sim, the guys just don't execute the procedure correctly.
No need to change the procedure, just teach them how to do it correctly. It is no big deal.
@Gorter: On the 737 the RTO brakes kick in as soon as the thrust levers are closed as long as the groundspeed is over 90 kts.
No need to change the procedure, just teach them how to do it correctly. It is no big deal.
@Gorter: On the 737 the RTO brakes kick in as soon as the thrust levers are closed as long as the groundspeed is over 90 kts.
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My friend rejected a takeoff in a 767 at high speed on a long runway and the RTO went to max braking when he reduced the throttles. Caused him a lot of grief at the hearing since the fuse plugs caused the tires to deflate. The ground crew in Brazil opened the side cockpit windows during the day and didn't close them properly so it opened on take off roll. He forgot to check if it was locked, not just closed. Sometimes that automatic stuff can really screw up your day.
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I don't think he got problems because of RTO braking, it was rather about stopping for a not closed flightdeck window which is not a stopping item and can easily be closed once airborne. There is even a nice boeing training video about that out there.
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The ground crew in Brazil opened the side cockpit windows during the day and didn't close them properly so it opened on take off roll. He forgot to check if it was locked, not just closed.
In fact boeing has done a series of unlocked window takeoffs with a 737 to demonstrate this. Furthermore, a major german charter airline includes a takeoff with a open cockpit window as training for their 757/767 crews.
The boeing video used to be on youtube or still is (too lazy to find it) but in any case the crew continued the takeoff with no problems whatsoever, leveled off and closed it without any problems.
Edit: Didn't see what Denti wrote before me, but he is spot on!
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Kicking it out is something one sees a lot in the simulator with somewhat inexperienced or badly trained chaps. Seems many have a "nerve memory" reaction to hit the brakes
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Never mind the unlocked window! What is more worrying is that bubbers 'friend' was surprised by max braking on the RTO. I think I would be more careful with whom I flew.
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Kicking it out is something one sees a lot in the simulator with somewhat inexperienced or badly trained chaps. Seems many have a "nerve memory" reaction to hit the brakes and do their own braking during a rejected take off, however that will quit the RTO function which is already max possible braking. Especially interesting to see on a limiting runway when they depart the end at 50 kts...
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Just a slight correction for "Seat 0A'....post #4, if I may!
I understand the GS only needs to 60 knots for RTO (90 for antiskid)
Please correct me if I'm under the wrong impression!
For 'Denti'...I was simply referring to 'under control' as a factor in getting the thing stopped before the end of the hard stuff, because unless I'm going close to doing that, I don't want to grind to a halt with RTO still selected. Hence to kick it out when things are under control.
Cheers
I understand the GS only needs to 60 knots for RTO (90 for antiskid)
Please correct me if I'm under the wrong impression!
For 'Denti'...I was simply referring to 'under control' as a factor in getting the thing stopped before the end of the hard stuff, because unless I'm going close to doing that, I don't want to grind to a halt with RTO still selected. Hence to kick it out when things are under control.
Cheers
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gorter . . .
close thrust lever and disconnect a/t
deploy speed brake
full reverse thrust.
deploy speed brake
full reverse thrust.
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Tee Emm - site wide problems with DTG stamps and other odds and sods at the moment.
The one you have cited has popped up on numerous forum threads. Hopefully, with the US holiday over in a day or three, the relevant IT tech folk will fix some of the problems.
Indeed, as you can see, in spite of posting about an hour after you .. my post is logged around 7 hours before yours. It's driving everyone mad at the moment but there is naught we can do until the US folks are back on deck.
The one you have cited has popped up on numerous forum threads. Hopefully, with the US holiday over in a day or three, the relevant IT tech folk will fix some of the problems.
Indeed, as you can see, in spite of posting about an hour after you .. my post is logged around 7 hours before yours. It's driving everyone mad at the moment but there is naught we can do until the US folks are back on deck.
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