Vietnam 787 No gear down

[Mr A Tis]

Surprised, this has not been mentioned before.
How can a 787 get to (alleged) 650ft and not realise gear not down?
https://simpleflying.com/vietnam-airlines-boeing-787-gear-up/
Have I missed something on this story?

[Meester proach]

They would have realised by the warning systems in place ,
whether that
prompted action we don’t know

[Selfloading]

Prompted by ATC
https://www.atsb.gov.au/publications/investigation_reports/2019/aair/ao-2019-051/

[Sailvi767]

The gear warning comes on at 800 feet AGL off the radar altimeter in the 787. Probably got the warning about the same time ATC was calling.

[gearlever]

The gear warning comes on at 800 feet AGL off the radar altimeter in the 787. Probably got the warning about the same time ATC was calling.

Yep, think so too.:ok:

[roundsounds]

The gear warning comes on at 800 feet AGL off the radar altimeter in the 787. Probably got the warning about the same time ATC was calling.
Melbourne is 400’ AMSL, FR24 data shows 650’ making it around 250’ AGL at the GA?

[DaveReidUK]

Melbourne is 400’ AMSL, FR24 data shows 650’ making it around 250’ AGL at the GA?

That would depend on whether the "650 feet" Mode S altitude from FR24 has or hasn't been corrected for QNH.

Given that it corresponded to at a point 1.6 nm from the THR, then I suspect they weren't actually at 250' AGL.

[Capt Fathom]

FR24 displays Altitude based on Standard Pressure. If there is a large difference between that and the local QNH, you will need to apply the difference to see the real altitude.
I recall the local QNH at the time was 1027mb. That’s a 420 feet adjustment.

[fatbus]

Plus crew reaction time

[perantau]

What is the terrain like on the approach? If it slopes upwards towards the runway, then 800ft on the radio altimeter may be low in reference to the runway threshold.

[DaveReidUK]

FR24 displays Altitude based on Standard Pressure. If there is a large difference between that and the local QNH, you will need to apply the difference to see the real altitude.I recall the local QNH at the time was 1027mb. That’s a 420 feet adjustment.
Yes, that's probably correct - while there are, I believe, a very small number of FR24 feeders running software that allows them to input the QNH adjustment at source, we can almost certainly discount that here.

So that would make the altitudes at the initiation of the GA (approximately):
Mode C/Mode S: 650'
AMSL: 1050'
AAL: 625'
Rad Alt/AGL: obviously dependent on terrain (if anyone with local knowledge can help, it was 1.6 nm from the THR, roughly overhead the Keilor Stadium)

[BuzzBox]

So that would make the altitudes at the initiation of the GA (approximately):
Mode C/Mode S: 650'
AMSL: 1050'
AAL: 625'
Rad Alt/AGL: obviously dependent on terrain (if anyone with local knowledge can help, it was 1.6 nm from the THR, roughly overhead the Keilor Stadium)

The elevation in that area is about 80m or 260ft, so approx. 800ft on the RADALT.

[suninmyeyes]

On the Boeing 777 you would get a config warning if you select land flap and the the gear is not down, so the warning would come at about 1500 AGL. I wonder why the logic is different on the 787.

[ScepticalOptomist]

On the Boeing 777 you would get a config warning if you select land flap and the the gear is not down, so the warning would come at about 1500 AGL. I wonder why the logic is different on the 787.

787 is the same.

[BuzzBox]

On the Boeing 777 you would get a config warning if you select land flap and the the gear is not down, so the warning would come at about 1500 AGL. I wonder why the logic is different on the 787.

The CONFIG GEAR warning logic is the same on the B777 and B787:

A landing gear is not down and locked and one of these occurs:

Below 800 feet radio altitude and a thrust lever is at idle
The flaps are in a landing position

A GPWS Mode 4A warning "TOO LOW GEAR" would occur at 500 ft RA.

[ManaAdaSystem]

I’m sure they have a gear warning when you select landing flap without gear down as well, same as the 737.
That will happen much earlier.

[Sailvi767]

On the Boeing 777 you would get a config warning if you select land flap and the the gear is not down, so the warning would come at about 1500 AGL. I wonder why the logic is different on the 787.

Is the same however if you failed to lower the gear you probably did not make the final flap setting. The last backup is the Radio Altimeter alert at 800 feet.

[Centaurus]

In the old days it would be called a low drag approach. Saves fuel. Left the gear down selection a bit late, that's all..

[Diavel]

To me this whole situation seems really strange, either the plane was not configured for landing, or the bells& whistles did not work. Alternatively the twr was wrong

[hans brinker]

FR24 displays Altitude based on Standard Pressure. If there is a large difference between that and the local QNH, you will need to apply the difference to see the real altitude.
I recall the local QNH at the time was 1027mb. That’s a 420 feet adjustment.


Was just looking at the Denver Airport, saw several airplanes at 0feet. Unless they dug a 5280feet hole, I am pretty sure the altitude displayed is at least some of the time based on QFE, not QNH/QFE....

[DaveReidUK]

Was just looking at the Denver Airport, saw several airplanes at 0feet. Unless they dug a 5280feet hole, I am pretty sure the altitude displayed is at least some of the time based on QFE, not QNH/QFE....

Nope. With WoW, altitude is always shown as zero, no QFE required.

[Smythe]

Well, knowing where MEL tower is, if they observed no gear down, damn.....

Low drag approach on the 787??....that is a lot of energy to manage on that ac...

the crew did GA...

[EcamSurprise]

The crew went around.

Yes the alert maybe came earlier but perhaps the initial “oh crap” reaction was to drop the gear. Then realisation sinks in and a go around flown.

or perhaps a few seconds where taken in the cockpit “oops, we screwed up, ready to go around? Yup? Ok off we go”.

It doesn’t have to be an instant TOGA.

[AerocatS2A]

Well, knowing where MEL tower is, if they observed no gear down, damn.....

Low drag approach on the 787??....that is a lot of energy to manage on that ac...

the crew did GA...

Apparently it was Essendon Tower that noticed.

[fdr]

In the old days it would be called a low drag approach. Saves fuel. Left the gear down selection a bit late, that's all..


ROFL

The poor schmuck can't win.... put the gear down too soon, you aren't efficient, put it down too late and ATC complain about the impending noise and FOD issue, and associated NOTAMS for runway closure. Now I recall one pilot who used to congratulate his FO's who out of an abundance of caution would lower the gear metaphorically at TOD.... he had a beef on contract terms with "the company". you just can't be too careful....

[India Four Two]

I think this is an appropriate thread to bring this great story by John Deakin to the attention of a wider audience:

Gear-Up Landing In A 747?
https://www.avweb.com/features/pelicans-perch-80-gear-up-landing-in-a-747/

[Mariner]

I think this is an appropriate thread to bring this great story by John Deakin to the attention of a wider audience:

Gear-Up Landing In A 747?
https://www.avweb.com/features/pelicans-perch-80-gear-up-landing-in-a-747/



Great reminder that we all are fallible India Four Two (https://www.pprune.org/members/53523-india-four-two), thanks!

[etudiant]

I think this is an appropriate thread to bring this great story by John Deakin to the attention of a wider audience:

Gear-Up Landing In A 747?
https://www.avweb.com/features/pelicans-perch-80-gear-up-landing-in-a-747/

Just superb. A 100,000 hour team of sky gods about to land a 747 wheels up.
PPRN at its finest, a true learning network!!

[jmmoric]

Normally in older aircraft (I strongly suspect it's the same in newer aircraft), the altitude sent by the transponder is fixed at a standard QNH setting of 1013.25 hPa... So there is no connection between the altitude sent by the transponder and the shown value on the altimeter (where it can be adjusted by the pilots).

The secondary radar systems will the make the conversion to the altitude based on the local QNH that is inserted into the radar system (automatically or manually).

As long as the transponders all just transmit using the standard QNH setting, everything is fine... cause that also ensures the safety nets in for example ACAS, and radar systems....

The altimeter setting by the pilots versus the transponder altitude is what we confirm every time you show up on radar. Sometimes we catch a wrong QNH setting by the pilots, sometime we catch a malfunctioning transponder...

How flightradar24 handles it, I have really no clue... but I suspect it uses the transponder altitude as well, whether it calculates according to local QNH or standard pressure?

EDIT: A response to the FR24 users, not this case in particular.

[DaveReidUK]

Normally in older aircraft (I strongly suspect it's the same in newer aircraft), the altitude sent by the transponder is fixed at a standard QNH setting of 1013.25 hPa... So there is no connection between the altitude sent by the transponder and the shown value on the altimeter (where it can be adjusted by the pilots).

The secondary radar systems will the make the conversion to the altitude based on the local QNH that is inserted into the radar system (automatically or manually).

As long as the transponders all just transmit using the standard QNH setting, everything is fine... cause that also ensures the safety nets in for example ACAS, and radar systems....

The altimeter setting by the pilots versus the transponder altitude is what we confirm every time you show up on radar. Sometimes we catch a wrong QNH setting by the pilots, sometime we catch a malfunctioning transponder...

How flightradar24 handles it, I have really no clue... but I suspect it uses the transponder altitude as well, whether it calculates according to local QNH or standard pressure?

EDIT: A response to the FR24 users, not this case in particular.

See posts #7, #8, #11, #20 and #21.

[jmmoric]

See posts #7, #8, #11, #20 and #21.

Yes, it was meant as a reply to them. Just talking a bit about the secondary surveillance and transponder side of the case :)

[DaveReidUK]

Yes, it was meant as a reply to them. Just talking a bit about the secondary surveillance and transponder side of the case :)

Ah, OK. Your suspicion that newer aircraft also send altitude based on 1013.25 is indeed correct.

[wiedehopf]

All aircraft with altitude reporting transmit their pressure altitude. (altitude based on an altimeter set to standard pressure)

Some newer aircraft also transmit the QNH used by the pilots.
Also some report GPS altitude.

FR24 does not correct for QNH.

[DaveReidUK]

Some newer aircraft also transmit the QNH used by the pilots.

Yes, in fact all aircraft that are equipped with EHS (Mode S EnHanced Surveillance) send the baro setting in the same transmission as Selected Altitude, though only when interrogated for it by a suitably-equipped SSR ground station.

[TopSwiss 737]

Maybe they tried to mimic this MD-10 approach? :}

https://m.youtube.com/watch?v=KDgvWa-EbbE