QF29 stick shaker & turbulence event

[dsam]

ABC report on air turbulence event 100 km prior to Hong Kong arrival:

 

http://ab.co/2p9KSBS

 

I wonder how often turbulence causes a 747 on autopilot to trigger a stick shaker? There were 15 passengers claiming injury, so it must have been quite significant turbulence.

 

Why don't passengers keep their seat belts on??!

 

 

[David2ayo]

I wonder at passengers undoing seatbelts, although the circumstances here are as yet unknown. I never undo mine in RPT, and don't even loosen it off - it feels better tight, and you can still get a good look at the on-board talent (?). The scary bit is a comment in the April Sport Pilot, where pilot and pax undid their belts before impact. I wonder who had custody of the Family Braincell that day?

 

David

 

 

[facthunter]

IF you are off field or forced landing you seatbelt(s) should be tight. Nev

 

 

[rankamateur]

I wonder who had custody of the Family Braincell that day?

Really big assumption that there is one.

 

 

[facthunter]

When the seat belt sign goes off, (allowing cabin service to happen) there's a great rush of people taking their seat belts off. They don't obey the same signs after landing though, where they are left on until the plane stops. Well, planes have been becoming cattle trucks of the air. Perhaps a sheep dog could be used to round them up. Nev

 

 

[turboplanner]

When the seat belt sign goes off, (allowing cabin service to happen) there's a great rush of people taking their seat belts off. They don't obey the same signs after landing though, where they are left on until the plane stops. Well, planes have been becoming cattle trucks of the air. Perhaps a sheep dog could be used to round them up. Nev

People always said aircraft would be like public buses one day, and they appear to have got their wish.

This is the biggest factor in the decline of GA, because it has reduced the cost so significantly.

 

I guess we can't have everything.

 

 

[facthunter]

The new aircraft have seat costs below 18 cents per km. Not much can beat that. Nev

 

 

[DWF]

At 100km (about 55nm) from landing I would expect the seat belt signs would be on and the cabin crew checking that seat belts were fastened, etc. I wonder how many of the casualties were cabin crew.

 

DWF

 

 

[facthunter]

The aircraft would normally be descending at that distance and stall buffet margins would be higher than some cruise levels used for economy..Turbulence in clear air is not very predictable and pilots encountering it usually report it to other traffic.. AS to why the stick shaker activated I know not. In "older" jets you are limited by the MMo (Mach speed limits) and at lower levels by airspeed VMo. reference. At the appropriate time you have to change over. or you may exceed limits.

 

Some auto pilots can be a trap. If you are locked onto a certain parameter you can lose protection on another. Ie Altitude hold . An engine loss of power (even partial) will cause an airspeed decay. Maintains set level.

 

Attitude hold .no control of anything much but basic short term useful. A default situation. Retains current attitude (Pitch.)

 

Vertical speed hold. Ok for flaring onto levels manually or trimming to set airspeed or Mach hold.

 

This is basic stuff for older equipment, where you had to monitor exactly what was going on, but probably applies to any basic autopilot.

 

In the days I'm referring to, IF there was any turbulence you took the autopilot out and hand flew it. THAT was normal procedure. Today the autopilot is considered to be adequate (superior) to human input. Nev

 

 

[Birdseye]

Most of the stuff I have read here and elsewhere refers to a stick-shaker activation. Was this actually a stick-pusher activation?

 

 

[Roundsounds]

Most of the stuff I have read here and elsewhere refers to a stick-shaker activation. Was this actually a stick-pusher activation?

The 747-400 doesn't have a stick pusher

 

 

[Birdseye]

The 747-400 doesn't have a stick pusher

Thanks, just wondered.

 

 

[1958cessna172]

According to th WA "expert" the 747 flew into a descending wingtip vortice from a heavy aircraft that had flown just above that airspace a short period of time before. maybe an A380 or the like on departure?

 

 

[facthunter]

That's possible. We are starting to realise how strong and persistent these effects can be. It used to be considered more a "slow and heavy" phenomenon. The energy in weather systems is of a vastly higher order of magnitude than any of this plane caused stuff as well as orographic effects (Mt Fuji fatal years ago) Avoidance is better than any other fix. Modern aircraft are not built to aerobatic load carrying figures. You can't rule out overstressing the airframe. Nev