Configuration Warning near V1. Continue or stop?
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Configuration Warning near V1. Continue or stop?
In most take off safety briefs the mention is made of the various events that warrant a rejected take off. A Take off configuration warning is one of those events.
Saw it happen in a simulator where the instructor triggered a config warning at 15 knots below V1 and accelerating fast. After a brief hesitation the pilot elected to continue but remained on the runway past V2 rather in shock than a deliberate ploy. A normal rotation was made and although the leading edge devices had retracted (caused by the inconsiderate instructor pressing a special button) the 737 climbed away without any problem around V2 + 25.
This got me thinking. After all it was a successful outcome and it would have been a trifle boorish to criticise a command decision that went the right way. Close to V1 there is little time to ponder exactly what system failure caused the configuration warning to go off. The alternative is an inevitable heavy weight high speed abort with its attendant well documented risks.
Weighing it up, perhaps the greater danger is the high speed abort as against leaving the aircraft on the runway and accelerating to a higher VR before rotation with either an asymmetric or no leading edge devices situation. Of course it could also be the once in a million false warning like some false fire warnings. It made for an interesting post flight de-briefing.
Saw it happen in a simulator where the instructor triggered a config warning at 15 knots below V1 and accelerating fast. After a brief hesitation the pilot elected to continue but remained on the runway past V2 rather in shock than a deliberate ploy. A normal rotation was made and although the leading edge devices had retracted (caused by the inconsiderate instructor pressing a special button) the 737 climbed away without any problem around V2 + 25.
This got me thinking. After all it was a successful outcome and it would have been a trifle boorish to criticise a command decision that went the right way. Close to V1 there is little time to ponder exactly what system failure caused the configuration warning to go off. The alternative is an inevitable heavy weight high speed abort with its attendant well documented risks.
Weighing it up, perhaps the greater danger is the high speed abort as against leaving the aircraft on the runway and accelerating to a higher VR before rotation with either an asymmetric or no leading edge devices situation. Of course it could also be the once in a million false warning like some false fire warnings. It made for an interesting post flight de-briefing.
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I would be inclined to agree.
Generally speaking, the config warning at or near V1 is 'usually' the speed brake lever having just come up a bit on the type that I fly, however at or near V1, the takeoff should be continued, with possibly an overspeed V2(improved climb) used, if at all possible, runway permitting, of course.
Generally speaking, the config warning at or near V1 is 'usually' the speed brake lever having just come up a bit on the type that I fly, however at or near V1, the takeoff should be continued, with possibly an overspeed V2(improved climb) used, if at all possible, runway permitting, of course.
In the type I flew, the configuration warning was theoretically inhibited once the throttle levers were beyond a certain position...
However, on day we received a configuration warning at around 90 KIAS (well below V1), so rejected the take-off. The fault was later proved to be a faulty 'interruptor unit' - the thing which caused the beeping. This was shared with the cabin altitude warning system and it was incorrectly sensing an excessive cabin altitude.
The rejected take-off was very straightforward, but we had the luxury of about 12 simulator sessions per annum and probably 20 or so high speed abort practices in the box. So it was, to some extent, second nature.
What really annoyed me though was to learn that several of my colleagues had also had the horn go off for the same reaon in this jet - but hadn't bothered to snag it...
I never accepted the 'just ignore it' advocates who said they'd continue if the configuration warning sounded during the take-off roll; years earlier an airline operating the same type had a nuisance configuration warning when it was tested prior to flight. They decided not to go - which was just as well. The cause of the warning was an unserviceable tailplane incidence sensor; however, the cause of the unserviceability was significant damage to the tailplane and fin caused by a previous encounter with severe turbulence......
However, on day we received a configuration warning at around 90 KIAS (well below V1), so rejected the take-off. The fault was later proved to be a faulty 'interruptor unit' - the thing which caused the beeping. This was shared with the cabin altitude warning system and it was incorrectly sensing an excessive cabin altitude.
The rejected take-off was very straightforward, but we had the luxury of about 12 simulator sessions per annum and probably 20 or so high speed abort practices in the box. So it was, to some extent, second nature.
What really annoyed me though was to learn that several of my colleagues had also had the horn go off for the same reaon in this jet - but hadn't bothered to snag it...
I never accepted the 'just ignore it' advocates who said they'd continue if the configuration warning sounded during the take-off roll; years earlier an airline operating the same type had a nuisance configuration warning when it was tested prior to flight. They decided not to go - which was just as well. The cause of the warning was an unserviceable tailplane incidence sensor; however, the cause of the unserviceability was significant damage to the tailplane and fin caused by a previous encounter with severe turbulence......
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Originally Posted by Centaurus
This got me thinking. After all it was a successful outcome and it would have been a trifle boorish to criticise a command decision that went the right way. Close to V1 there is little time to ponder exactly what system failure caused the configuration warning to go off. The alternative is an inevitable heavy weight high speed abort with its attendant well documented risks.
Weighing it up, perhaps the greater danger is the high speed abort as against leaving the aircraft on the runway and accelerating to a higher VR before rotation with either an asymmetric or no leading edge devices situation. Of course it could also be the once in a million false warning like some false fire warnings. It made for an interesting post flight de-briefing.
Weighing it up, perhaps the greater danger is the high speed abort as against leaving the aircraft on the runway and accelerating to a higher VR before rotation with either an asymmetric or no leading edge devices situation. Of course it could also be the once in a million false warning like some false fire warnings. It made for an interesting post flight de-briefing.
I agree with you, if you consider what Boeing states for aborted takeoff procedures between 80 kias and V1 (engine failure, fire, aircraft unsafe to fly, predictive windshear). But... could the takeoff config warning be a warning of an aircraft that could become unsafe to fly for any reason ?
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GlueBall,
I take it your remark was rather tounge-in-cheek. If not, please expand on that philosophy - I'm eager to learn. I was just brought up with this wimpy "Train the way you fight - fight the way you train"-attitude that is obviously past its sell-by-date
Empty
I take it your remark was rather tounge-in-cheek. If not, please expand on that philosophy - I'm eager to learn. I was just brought up with this wimpy "Train the way you fight - fight the way you train"-attitude that is obviously past its sell-by-date
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In my company, a Config Warning is a compulsory "Stop" call from either Pilot up to V1. So in the Sim, in a politically correct environment, "Stop" it would (have to) be.
In reality, and IMHO, Config Warnings are there to stop the crew making "plonkers" of themselves i.e. trying to takeoff with some major config error, and as a consequence, once you have got takeoff power set, and no Config Warning, it's real purpose is over.
Therefore a Config Warning occurring near V1 is indicating either some major "change" in configuration (and hardly likely to have been crew selected), or an indication fault feeding into the Config Warning system. It then comes down to the situation on the day, and whether it is a "Go" V1, or a "Stop" V1, and your judgement, about whether to "Stop" or not. I know which I'd tend towards
In reality, and IMHO, Config Warnings are there to stop the crew making "plonkers" of themselves i.e. trying to takeoff with some major config error, and as a consequence, once you have got takeoff power set, and no Config Warning, it's real purpose is over.
Therefore a Config Warning occurring near V1 is indicating either some major "change" in configuration (and hardly likely to have been crew selected), or an indication fault feeding into the Config Warning system. It then comes down to the situation on the day, and whether it is a "Go" V1, or a "Stop" V1, and your judgement, about whether to "Stop" or not. I know which I'd tend towards
Config is normally a red warning.
If the reason for the warning is identifiable (i.e. a config error) then the take off should be rejected.
If the reason is not identified then crew must not make any assumption as they cannot judge between an undetected fault and a nuisance warning. Thus, with a config warning less than V1, always stop.
Many aircraft have a pre takeoff ‘embarrassment’ config check button e.g. BAe146. This does not prevent an item in the config circuit moving out of alignment after that check or preclude any operating error.
N.B. BAe146 takeoff accident in China. A config warning was given during the pre-takeoff check. The crew failed to identify the fault (a rather obvious failure to select flap), the crew erroneously deduced a flap gauge fault and overrode the flap config system and commenced the take off. The flap config auto reset was re-enable after approx 20 sec, thus a config warning was given as the aircraft passed the end of the runway – it did not get airborne and there were many fatalities.
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If the reason for the warning is identifiable (i.e. a config error) then the take off should be rejected.
If the reason is not identified then crew must not make any assumption as they cannot judge between an undetected fault and a nuisance warning. Thus, with a config warning less than V1, always stop.
Many aircraft have a pre takeoff ‘embarrassment’ config check button e.g. BAe146. This does not prevent an item in the config circuit moving out of alignment after that check or preclude any operating error.
N.B. BAe146 takeoff accident in China. A config warning was given during the pre-takeoff check. The crew failed to identify the fault (a rather obvious failure to select flap), the crew erroneously deduced a flap gauge fault and overrode the flap config system and commenced the take off. The flap config auto reset was re-enable after approx 20 sec, thus a config warning was given as the aircraft passed the end of the runway – it did not get airborne and there were many fatalities.
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Admittedly, I've only flown older model airplanes(B737/727, DC9/MD80, CV880) but the takeoff configuration warning was triggered by throttle position or perhaps an EPR setting ( in the neighborhood of 1.4) with the existence a configuration problem.
Either of these occurred rather early in the TO roll...mostly before 80 kts. Stopping the TO under this condition was rather a non-event.
Forgive me, but how does one get anywhere near V1 before a configuration warning is sounded and stopping would be a particularly serious problem.
What have I missed here ?
Either of these occurred rather early in the TO roll...mostly before 80 kts. Stopping the TO under this condition was rather a non-event.
Forgive me, but how does one get anywhere near V1 before a configuration warning is sounded and stopping would be a particularly serious problem.
What have I missed here ?
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...unscheduled config-changes, inadvertent positioning of flap lever, uncommanded slat retraction, inadverdent speedbrake deployment, uncommanded stabiliser movement - to name a few 
I do agree with what many people in this forum have said about near V1-cuts, but when it comes to trying to outsmart the safety systems in a fraction of seconds, I must admit my limit is reached. Yep, we can all be rocket scientists when sitting at home with a cuppa, but there is no time for focus groups or mental artistery at V1 -10. You brief it as you want it done - end of story.
Is it me or is there - in several threads relating to V1 - an attitude creaping in that a) there is room for meddling with V1 and b) serious failures are so rare that it's much better to assume spurious warning & continue, rather than stopping and potentially damaging the aircraft in a 40 kt. overrun?
Are there any examples of rejected takeoffs that have been carried out by the book, from at or below V1 that have resulted in personal injury? If so, when we weigh them against the outcomes of the cases where the take-off should have been rejected (but was continues) - which one would you rather be associated with?
Empty.
I do agree with what many people in this forum have said about near V1-cuts, but when it comes to trying to outsmart the safety systems in a fraction of seconds, I must admit my limit is reached. Yep, we can all be rocket scientists when sitting at home with a cuppa, but there is no time for focus groups or mental artistery at V1 -10. You brief it as you want it done - end of story.
Is it me or is there - in several threads relating to V1 - an attitude creaping in that a) there is room for meddling with V1 and b) serious failures are so rare that it's much better to assume spurious warning & continue, rather than stopping and potentially damaging the aircraft in a 40 kt. overrun?
Are there any examples of rejected takeoffs that have been carried out by the book, from at or below V1 that have resulted in personal injury? If so, when we weigh them against the outcomes of the cases where the take-off should have been rejected (but was continues) - which one would you rather be associated with?
Empty.
Originally Posted by Empty Cruise
...unscheduled config-changes, inadvertent positioning of flap lever, uncommanded slat retraction, inadverdent speedbrake deployment, uncommanded stabiliser movement - to name a few : .
Well, I suppose anything is possible, but I'd be interested to hear from people who've had the things you mention actually happen to them after TO power was set and the IAS neared V1. "...uncommanded slat retraction...inadventent speedbrake deployment...inadvertent positioning of the flap lever..." ? Inadvertent positioning of the flap lever AFTER to power is set and the IAS has progressed to near V1 ?
I guess it's the probability I question. All seems rather unlikely. Admittedly, I haven't heard of every case that ever happened but in 35+ years of operating these airplanes I never had anything of the sort happen or even heard of these cases in the literature I read.
I learn new stuff all the time....give me some documented "new stuff" to support your contention.
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Not a jet I know but I've had an unscheduled autofeather of an engine (PW123) just on rotate. There was nothing wrong with the engine as such, just a faulty PFM box.
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Bafanguy,
We operate the MD90 with a "Dial A Flap" system, this allows any variable flap setting to be selected within a certain band. we used to have plenty of high speed configuration warnings when operating at the limit of a band (say Flaps 13) due to the external forces moving the flaps sufficiently to activate the micro switch, ie Flaps 12!
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We operate the MD90 with a "Dial A Flap" system, this allows any variable flap setting to be selected within a certain band. we used to have plenty of high speed configuration warnings when operating at the limit of a band (say Flaps 13) due to the external forces moving the flaps sufficiently to activate the micro switch, ie Flaps 12!
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In the simulator you should always abort before V1, do the exercise for training purposes,...to learn the stopping power of your airplane.
Aborting at V1 in a heavy jet can be a violent maneuver, especially when your gross weight is runway limited, not to mention the condition of the brakes and tires and the delay in applying immediate maximum brake pressure if no RTO auto braking is available.
My crew is always briefed as such that when my hand comes off the throttles that it's a "go" decision and not even to think about stopping. In the real airplane my hand may come off the throttles up to 15 knots before V1, depending on gross weight, weather conditions, runway conditions and runway remaining. And that's the way it is.
Aborting at V1 in a heavy jet can be a violent maneuver, especially when your gross weight is runway limited, not to mention the condition of the brakes and tires and the delay in applying immediate maximum brake pressure if no RTO auto braking is available.
My crew is always briefed as such that when my hand comes off the throttles that it's a "go" decision and not even to think about stopping. In the real airplane my hand may come off the throttles up to 15 knots before V1, depending on gross weight, weather conditions, runway conditions and runway remaining. And that's the way it is.