BA 747 100Kts & stick shake?
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BA 747 100Kts & stick shake?
Lots of rumours around about a very recent BA go-round at LHR in a 744 resulting in a very low speed, stick shake and immediate crew suspension. Anyone confirm or deny? Everyone's being too tight-lipped about this - I am therefore very suspicious!
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Yes Sir Kitt, heard the same today. A go-around in good weather due blocked runway is what I heard, with a stall or near stall soon after. Someone in authority refused to confirm or deny or this rumour - not a good sign!
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100KIAS?????
Bu99er! I didn't think a 744 would still be flying at 100?
Is that legit? and if so, could 747Focal or any of the other Boeing chaps advise what she would be capable of at the scary end of the brown underpants scale.
Regards
Bu99er! I didn't think a 744 would still be flying at 100?
Is that legit? and if so, could 747Focal or any of the other Boeing chaps advise what she would be capable of at the scary end of the brown underpants scale.
Regards
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Well the APPCH speed chart goes down to 180T, and the speed is 121kts. So stick shaker @ 100kts sounds right. More realistic with light wt and lo gas is landing wt of 220T, which is 134kts, so still plausible to have stick shaker around 100kts. My guess is that at stickshaker on a GA, not too many people are going to be focusing on precise speed tape reading.
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Possibly with these 'monitored' approaches where they hand over control during the approach no one knew who had control. I'm not sure how the system works though.
Vref an landing is usually around 140kias. Had they gone around and pushed the TOGA button the autothrottle would have engaged which would give speed protection.
But for the grace of God there go a lot of us!
Vref an landing is usually around 140kias. Had they gone around and pushed the TOGA button the autothrottle would have engaged which would give speed protection.
But for the grace of God there go a lot of us!
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srjumbo
I dont know the Jumbo but during a manual GA isnt it posible for the crew to pitch and lose speed before the engines can recover it - i know all the guidance ( a/p and f/d ) is speed related.
I dont know the Jumbo but during a manual GA isnt it posible for the crew to pitch and lose speed before the engines can recover it - i know all the guidance ( a/p and f/d ) is speed related.
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srjumbo, the autothrottle will not give *any* speed protection, as it simply applies maximum (GO-AROUND) thrust. So pitch the aircraft up high enough, and it can do nothin' at all to protect the speed. An Airbus on the other hand.... *ducks* 
Also, no matter what you think of the monitored approach, crews have been trained well enough in performing these approaches, that they know who's in control at what stage, don't worry.
Well that's me, yes, it's also possible to pitch the aircraft up too much before the engines have spooled up.
Then again, it probably is a Sun reporter meeting
Also, no matter what you think of the monitored approach, crews have been trained well enough in performing these approaches, that they know who's in control at what stage, don't worry.
Well that's me, yes, it's also possible to pitch the aircraft up too much before the engines have spooled up.
Then again, it probably is a Sun reporter meeting
I assume that the stick shaker is triggered by a vane that senses angle of attack. Therefore, during a go-around with a high nose up pitch rate the speed will be higher when the critical AoA is reached than it would be during a wings level slow down. In other words, if the stick shaker would be triggered at, say, 100 KIAS in straight and level flight, it would trigger at a higher speed during a dynamic go-around. And the more aggressive the nose-up rotation, the higher the speed.
Perhaps it should be considered that if the aircraft was forced into a very late go-around due to, say, a runway incursion, a very rapid rotation which triggered the stick shaker may actually have prevented an accident! I have no facts, but there are two sides to any coin.
Perhaps it should be considered that if the aircraft was forced into a very late go-around due to, say, a runway incursion, a very rapid rotation which triggered the stick shaker may actually have prevented an accident! I have no facts, but there are two sides to any coin.
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Stall warniing systems
Just for some info, the stall warning system (Stick shaker), looks at Aircraft Speed, Angle of attack and Flap position and also engine speed and flight status. All these parameters are monitored by a stall warning computer, if the correct combination is monitored, then the stick shaker will operate. These could be, low airspeed or high angle of attack with incorrect flap setting.
The point at which the warning occurs is also influenced by engine speed, airspeed, and any asymmetry between leading edge and trailing edge flaps.
The AOA sensor monitors 'relative' airflow, so with a high nos attitude at slower speeds the AOA will be high, but at higher speeds such as climbout it will be less. It is just like a weather vane.
Hope this helps.
The point at which the warning occurs is also influenced by engine speed, airspeed, and any asymmetry between leading edge and trailing edge flaps.
The AOA sensor monitors 'relative' airflow, so with a high nos attitude at slower speeds the AOA will be high, but at higher speeds such as climbout it will be less. It is just like a weather vane.
Hope this helps.
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What a lot of cobblers, i.e. non-news !
You can have the stick shaker going off during all manner of manouvers wherein having the stick shaker going off indicates that you are approaching the stall - not that you have stalled !
E.g. Who here remembers the Continental B747 - 'twas in the late 1980's - which took off from LGW and was ( if my memory serves me right ) bound for MIA i.e. it was very heavy, but wherien it then had one engine fail and another suffered a partial failure, following which it just about missed some hills to the west of Gatwick ( Rushy Hill ? ), i.e. litterally by only a few feet - and pretty much the whole thing ( well certainly the first few minutes ) was flown with the stick shaker rattling away - after which they landed back at LGW somewhile later ( having dumped mucho fuel over Sussex and the English Channel ); the flight crew did an heroic job !
You can have the stick shaker going off during all manner of manouvers wherein having the stick shaker going off indicates that you are approaching the stall - not that you have stalled !
E.g. Who here remembers the Continental B747 - 'twas in the late 1980's - which took off from LGW and was ( if my memory serves me right ) bound for MIA i.e. it was very heavy, but wherien it then had one engine fail and another suffered a partial failure, following which it just about missed some hills to the west of Gatwick ( Rushy Hill ? ), i.e. litterally by only a few feet - and pretty much the whole thing ( well certainly the first few minutes ) was flown with the stick shaker rattling away - after which they landed back at LGW somewhile later ( having dumped mucho fuel over Sussex and the English Channel ); the flight crew did an heroic job !
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Devil's Advocate,
I remember the Continental 747 incident and it was Russ Hill that it just missed. They were cleaning fuel off everything in the area for days afterwards.
If for some reason it was a late go around call which required a rather prompt pull on the column could you end up with a false stick shaker warning as the AoA temporarily read excessively high especially if the speed was slow, maybe close to Vref?
chc
I remember the Continental 747 incident and it was Russ Hill that it just missed. They were cleaning fuel off everything in the area for days afterwards.
If for some reason it was a late go around call which required a rather prompt pull on the column could you end up with a false stick shaker warning as the AoA temporarily read excessively high especially if the speed was slow, maybe close to Vref?
chc
Last edited by carbheatcold; 31st Mar 2004 at 15:26.
There, there, don’t get too excited … sounds like a commercial for insurance, but that is exactly what a stick shaker system is. It is an alert to an unusual condition; more forceful than a call from the NFP, like a friendly poke in the arm giving the handing pilot additional awareness or, if necessary, a wakeup call.
As described earlier most SS systems alert at approx 1.1Vs, but with even earlier alerts for applied load factor (g) and high pitch rate, the latter features are available from alpha and alpha rate. Depending on aircraft type and SS system, the SS alert may be over sensitive to certain turbulence conditions, gusts, or even sideslip. Thus, providing recovery action is initiated there isn’t very much to get overexcited about, you still have 10% of stall speed as a margin.
We must wait for the details of this event, but bearing in mind that the certification and operational requirements of the aircraft require maneuvering close to the boundaries of alerting systems we should not be surprised if occasionally the limit is encountered. A max rate go-around could generate 1.25g, although most GAs are much less. This g level equates to an increase in the stall speed and corresponding SS speed to values not far from the normal GA speed Vref (1.3Vs) e.g for 100kt Vs x SQR 1.25g =111 kts. For a GPWS pull up crews should be taught to aim for 1.3 g, similar for ACAS until the maneuver is established. For a Windshear encounter crews are taught to fly ‘at’ but to respect the stick shake speed i.e. just short of an alert.
It would be disappointing for the industry if this crew were suspended for what appears to be a benign event; crews have enough stresses without the addition of such action. I detect an unhealthy trend in the industry where managers suspend pilots for the most minor of events (even good GAs); possible this is due to the continuing good safety record and there are fewer serious events to investigate. However this management attitude does little to maintain an open reporting and ‘just’ safety culture, nor does it encourage crews to fly near to limiting speeds when demanded by procedure or warranted by crew judgment.
Let us wait and see what actually happened during the GA.
As described earlier most SS systems alert at approx 1.1Vs, but with even earlier alerts for applied load factor (g) and high pitch rate, the latter features are available from alpha and alpha rate. Depending on aircraft type and SS system, the SS alert may be over sensitive to certain turbulence conditions, gusts, or even sideslip. Thus, providing recovery action is initiated there isn’t very much to get overexcited about, you still have 10% of stall speed as a margin.
We must wait for the details of this event, but bearing in mind that the certification and operational requirements of the aircraft require maneuvering close to the boundaries of alerting systems we should not be surprised if occasionally the limit is encountered. A max rate go-around could generate 1.25g, although most GAs are much less. This g level equates to an increase in the stall speed and corresponding SS speed to values not far from the normal GA speed Vref (1.3Vs) e.g for 100kt Vs x SQR 1.25g =111 kts. For a GPWS pull up crews should be taught to aim for 1.3 g, similar for ACAS until the maneuver is established. For a Windshear encounter crews are taught to fly ‘at’ but to respect the stick shake speed i.e. just short of an alert.
It would be disappointing for the industry if this crew were suspended for what appears to be a benign event; crews have enough stresses without the addition of such action. I detect an unhealthy trend in the industry where managers suspend pilots for the most minor of events (even good GAs); possible this is due to the continuing good safety record and there are fewer serious events to investigate. However this management attitude does little to maintain an open reporting and ‘just’ safety culture, nor does it encourage crews to fly near to limiting speeds when demanded by procedure or warranted by crew judgment.
Let us wait and see what actually happened during the GA.
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Stick shaker...well, that's what it's there for, is it not?
To alert the crew of a too low speed.
OTOH, did have a stick pusher malfunction in an HFB320 some years ago, just after takeoff at about 200agl.
Tried to bury the column in the instrument panel....now that will get your attention.
To alert the crew of a too low speed.
OTOH, did have a stick pusher malfunction in an HFB320 some years ago, just after takeoff at about 200agl.
Tried to bury the column in the instrument panel....now that will get your attention.
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Heard the handling pilot screwed up taking out A/THR at touchdown and hit TOGA button ONCE instead. He was trying to land, a/c wanted to fly (just). Took a while before crew realised quite what was happening. Low slow fly by and close to losing the aircraft. Subsequent landing was non-event.
That's all I will say.
That's all I will say.