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Originally Posted by hans brinker
(Post 10575500)
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....
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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... |
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. |
Originally Posted by Smythe
(Post 10576190)
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... |
Originally Posted by Centaurus
(Post 10575343)
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.... |
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/pelic...ding-in-a-747/ |
Originally Posted by India Four Two
(Post 10576760)
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/pelic...ding-in-a-747/ Great reminder that we all are fallible India Four Two, thanks! |
Originally Posted by India Four Two
(Post 10576760)
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/pelic...ding-in-a-747/ PPRN at its finest, a true learning network!! |
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. |
Originally Posted by jmmoric
(Post 10578122)
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. |
Originally Posted by DaveReidUK
(Post 10578233)
See posts #7, #8, #11, #20 and #21.
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Originally Posted by jmmoric
(Post 10578263)
Yes, it was meant as a reply to them. Just talking a bit about the secondary surveillance and transponder side of the case :)
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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. |
Originally Posted by wiedehopf
(Post 10578424)
Some newer aircraft also transmit the QNH used by the pilots.
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Maybe they tried to mimic this MD-10 approach? :} |
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