PPRuNe Forums - 787 bounce

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Quote:

Originally Posted by Midland63 (Post 10386125)

Thanks. Didn't appreciate the thing about the gear doors creating extra drag but understand now. But there seemed to be an implication that there was a different procedure re the gear (leaving them down for longer) in a G/A due to windshear compared with other G/As. Or did I misunderstand that wrongly and gear is left down longer in all G/As, for any reason, from a very low height, or having touched, compared with a G/A from higher up.

Uhhh 737 do not really have ' doors' over the main gear- so discussion re gear doors on 737 are ??

Quote:

Originally Posted by Midland63 (Post 10386125)

Uhhh 737 do not really have ' doors' over the MAIN gear- so discussion re gear doors on 737 are ??

https://aviation.stackexchange.com/q...d-from-weather

Quote:

Originally Posted by BluSdUp (Post 10386245)

All my Types have the same: Max Pwr NO Config change!
Industry standard for GPWS and Low level Wind Shear escape I gather:

Greenfields
I do disagree, the Gear stays as there is plenty of times the aircraft touches down after a momentary positive climb.( Microburst mostly).
Secondary touchdown with gear in transit will ruin Your day.
Also remember if You have to trade all your airspeed down towards shaker, that gear does not give you much drag as it is the old " Parasite Drag" so it gets less with less speed.

Can we have one example of an aircraft touching down after a momentary positive climb in a microburst, please?

Airbus have a ‘baulked landing procedure’ for this very situation and it instructs the pilot to make no immediate configuration changes in the go-around from such a situation. The reason is nothing to do with windshear or whatever - it’s because the standard action of retracting some Flap might result in sink. If the gear has been/is being retracted too, you could be in for ground contact and a disaster.

i don’t know if Boeing teach this, but it seems like a good idea to me, and the crew on this flight got it absolutely right.
maybe they were ex Airbus ;)

Quote:

Originally Posted by FlightDetent (Post 10386154)

Midland63 The L/G is kept down during the wind shear escape routine (also) because terrain impact is a possibility. The loads absorbed by the collapsing undercarriage structure make survival of the occupants more likely, any straw counts.

While the doors protruding into the airflow will add drag, and the explanations above that it is accounted for in the EFATO case are sound, the mainstay B737 does not have any on the main landing gear. Go figure? The priority on both GWPS (terrain) and WSHR (loss of lift) scenarios must be to fly the aeroplane up, as the single objective. I gather that history teaches us messing with configuration might be detrimental to the crew's coordinated effort to ensure max thrust is set and peak climb performance is established (with speed-brakes retracted).

My best guess is that avoiding the doors' extra drag applies for GPWS, where the danger of impact is truly immediate. For WSHR, the impact-survival aspect would be the reason, which covers the 737 too. As well you want to keep the procedures simple and similar as much as practicable. What is seen in the video may be better described as a low-level G/A with unavoidable touchdown due to a de-stabilized flare, owing to gust (most likely). The industry standard wind shear model is probably different, though related. Still, the L/G lever is not to be touched!

it was some years ago, but an Airbus Flight Test Pilot, Engineer and performance geek gave a very close answer to the above WRT windshear escape at a getting to grips chat . They stated that in days of old, with older designed airframes, and less powerful engines, raising the gear was performance limiting, in some cases even in benign conditions. These aircraft needed full power for missed approaches , and had little power to reduce for takeoff .
But with modern designed, engine thrust can be reduced by upto 40% for takeoff at lighter weights (A380) and have max landing weights almost 200T lighter than takeoff weights (A380) . For missed approaches reduced thrust is used to limit climb rates. Performance wise, modern design of airframe and engines is far superior to a lot of older designs (not all though) .
As speed when after takeoff or fully configured for landing is low, and for modern Airbus FBW the effect of raising the gear is considered minimal .
However, they consider windshear encountered below 500 feet as the most performance limiting . As on approach speed will be established at Vapp and, with autothrust, Eng RPM may be low, putting the aircraft in a low energy situation. Due to the chance of ground contact, it was decided not to change any procedure, but rather have both pilots fully concentrating on flying the aeroplane without any distraction .

As above
"Due to the chance of ground contact, it was decided not to change any procedure, but rather have both pilots fully concentrating on flying the aeroplane without any distraction ."

That's the answer.

Quote:

Uhhh 737 do not really have ' doors' over the MAIN gear- so discussion re gear doors on 737 are ??

I thought the aircraft central to this discussion was a 787?

After this event, it's being renamed the BOING 787, according to my mate Zebedee.....

Quote:

Originally Posted by The Fat Controller (Post 10386576)

After this event, it's being renamed the BOING 787, according to my mate Zebedee.....

As per post #2, for those who have been reading the thread from the start ...

Quote:

Originally Posted by The Fat Controller (Post 10386576)

After this event, it's being renamed the BOING 787, according to my mate Zebedee.....

like it :D

Quote:

Originally Posted by greenfields (Post 10386180)

Unless it was for WINDSHEAR, in which case the TOGA switches are pressed prior to advancing the TLs.

This is a by product of the escape manoeuvres, not a reason for it to remain down. The gear is left down (no change to config) for one reason only - the performance of the aircraft. It is not left down in case of ground contact, rather it is left down to avoid ground contact (by not increasing drag as the doors open.)

NP on the 787 leaves the A/T engaged at all times. A gotcha is that should the main gear contact the ground, the A/T drops out. No idea if the TOGA switches were pressed before or after touch down in this case? Also, if WINDSHEAR is detected the AFDS function is altered. I believe this is common to the 777 and was a factor in the EK accident a while back in which TOGA was presumably pressed but the T/L didn’t advance as the aircraft had touched down and the crew rotated and residual energy started a climb which was short lived as there was no / little thrust.

Happy to be corrected on any / all of the above.

Alternatively, they may have flown a "normal" GA profile, and forgot/failed to raise the gear right away. Seen it happen before.

Good job saving the aircraft though.

Is this thread still going? How? Such a non event!

How many of you here have landed after an aircraft in front has gone around? Or for that matter you have gone around and next aircraft landed?

It is called weather, called gusts for that reason... At one point in time is not the same as a minute later!

I’ve listebed to GA, land, land, GA, GA, land... My turn eeeee it’s rough very GA minded but landed, oh another time thought landing no problem (decent cross) and wala went around.

Aviation 101 taught from day dot.

Missed approaches or go around are frequently mishandled, the most common being delayed gear retraction, no big deal on what will have been a fairly light aircraft with both engines operating.

If if there was wind shear even without a warning I would delay gear/ flap retraction as the wind shear guidance computer gets messed up by configuration change.

TOGA should always be pressed other wise advancing the thrust alone will simply accelerate the aircraft towards the ground as it could still in in G/S mode, one press of TOGA ( TAKE OFF/GO AROUND) will give you a FD pitch up and thrust guidance and change from G/S and normally a 1000-2000 fpm rate of climb using reduced go around thrust, a second press will give you full G/A thrust and a ballistic rate of climb in a light and very powerful aircraft.

For wind shear escape after a wind shear warning (not caution) its all about terrain avoidance and advancing the thrust levers to full thrust ( FDEC prevents exceeding thrust limits) and pitching to the PLI’s ( pitch limit indicators)

In this go around and given the forecast wx covered an extended period I too would have diverted to my alternate, yes they might have got in on a second attempt but why push it? go to MAN refuel and put the passengers on a MAH LHR shuttle if need be.

Filmed from inside the 787 GA - Twas a ruff day mind....

Sure
Quite a few in simulators of say 5-600 instructed if executed wrong or starting of to strong.
It have to be said the CAE models are a bit rough, and if run at 100% it is a bit negative training as it is easy to end up with a crash.
The FAA (Nasa/ Ntsb?) models are a bit better.
Mind You I have not done any Sim Instruction the last 10 years so they may have gotten more realistic.
In real life cant say I recall any, no, Ergo training has worked , Eh Mana!?
Mind you , there is one on approach that is modeled after a US accident were it looks like you are out of the shear and then the BIG one hits. This one is quite late on approach so it ends with ground contact at time , during training.
Anyway
Second touch down or a controlled crash ,just do not mess with the gear until climbing away, and out of shear.

If the gusts were that bad you'd think there'd be multiple videos of planes going around. Airliners don't suddenly nose over, especially at that pitch rate, due to windshear.

Yes they do. Been there, done that, learned from it.

Quote:

Originally Posted by DaveReidUK (Post 10386595)

As per post #2, for those who have been reading the thread from the start ...

A simple "boing" was it seems mostly not enough.

I know what to do next time -

https://cimg2.ibsrv.net/gimg/pprune....00bf566c80.gif

Thanks, https://flamingtext.com.

Quote:

Originally Posted by Locked door (Post 10385393)

Really? You’re confusing windshear with gpws. Back to flight sim.

you’re confusing the two actually.