Not extending flaps while gear is extending
Thread Starter
Joined: Apr 2009
Posts: 645
Likes: 16
From: Canada
Not extending flaps while gear is extending
Had a Sim recently where the instructor was adamant about not extending flaps until gear extension was completed. But never got a satisfactory answer as to why.
Anyone have an answer?
Anyone have an answer?
Joined: Feb 2011
Posts: 88
Likes: 12
From: usa
Fly safe,
B-757
Joined: Jun 2005
Posts: 954
Likes: 5
From: USA
How much flaps?
If it's FULL flaps, I agree with the instructor. Bad form with the gear not down & locked. Plus I'd like to preserve what's left of my hearing!
The sim profiles are a useful template for speeds and configurations to achieve during each the various segments of an approach. Most jets have one or more increments of flaps deployed before gear extension. Gear extension is often delayed until just outside the FAF or GS intercept. Now, with the gear down and green, landing flaps can be selected for the final approach without all that noise!
Of course each type has it's own manufacturer recommended profile and operators differ as to some of the specific SOPs and techniques, but the idea is to be on profile and in a good position to maintain a stabilized approach. In practice, the timing of flap and gear extension can be adjusted in concert with the noise levers to account for variables such as visuals, slam dunks, short intercept vectors or speed assignments! But keeping those profiles in mind as a template for where "normal" should be gives you something to compare against your actual progress.
If you know each of the sim profiles cold, sim training goes allot more smoothly. When you get on the line, that's when it all comes together and pays dividends. Enjoy.
If it's FULL flaps, I agree with the instructor. Bad form with the gear not down & locked. Plus I'd like to preserve what's left of my hearing!
The sim profiles are a useful template for speeds and configurations to achieve during each the various segments of an approach. Most jets have one or more increments of flaps deployed before gear extension. Gear extension is often delayed until just outside the FAF or GS intercept. Now, with the gear down and green, landing flaps can be selected for the final approach without all that noise!
Of course each type has it's own manufacturer recommended profile and operators differ as to some of the specific SOPs and techniques, but the idea is to be on profile and in a good position to maintain a stabilized approach. In practice, the timing of flap and gear extension can be adjusted in concert with the noise levers to account for variables such as visuals, slam dunks, short intercept vectors or speed assignments! But keeping those profiles in mind as a template for where "normal" should be gives you something to compare against your actual progress.
If you know each of the sim profiles cold, sim training goes allot more smoothly. When you get on the line, that's when it all comes together and pays dividends. Enjoy.
Joined: Jul 2017
Posts: 94
Likes: 5
From: Europe
If it's A320 then it's quite simple - both gear and flaps are hydraulically powered. While the systems (especially pumps) are perfectly capable of operating both at the same time, it may be wise not to demand too much from them at once - if not to avoid sudden failure (which is most likely to occur during such high-load scenario) then simply to reduce wear and tear
Joined: Feb 2000
Posts: 4,704
Likes: 589
From: 500 miles from Chaikhosi, Yogistan
Are there any Airbus references for that theory? Or any statistical data ? What happens in a go around?
Or or are people just [cue best Monty python voice] “making it up as he goes along”.
Or or are people just [cue best Monty python voice] “making it up as he goes along”.
Joined: Jun 2007
Posts: 3,443
Likes: 39
From: Wanderlust
Had a Sim recently where the instructor was adamant about not extending flaps until gear extension was completed. But never got a satisfactory answer as to why.
Joined: Mar 2006
Posts: 2,633
Likes: 137
From: USA
Thanks vilas as usual for your insight (and reference).
Both A320 operators that I've been at have "gear down flaps 3" as a std config change callout. Never heard of anyone having trouble. Perhaps some older aircraft had an issue?
Both A320 operators that I've been at have "gear down flaps 3" as a std config change callout. Never heard of anyone having trouble. Perhaps some older aircraft had an issue?
Joined: Nov 2005
Posts: 88
Likes: 6
From: Here and there
Just a guess as to why: both the gear and the flaps/slats are downstream of the HYD priority valves, and if these two systems simultaneously demand high load in less than ideal circumstances, the prio valves might end up locking them out of the system for a bit, resulting in mismatch between the desired and the actual config for a few seconds. Not being a proper engineer, this would be my guess.
Joined: Feb 2000
Posts: 4,704
Likes: 589
From: 500 miles from Chaikhosi, Yogistan
Villas, agree with the wording for normal SOPs, and it’s the aim for the perfect profile.
However on my A319, the F2 selection is followed immediately by the following note...
no instructions to wait.
The normal “when flaps are at 2” is in the subsequent section.
But is there a restriction / limitation / prohibition on putting the gear out when the flaps are travelling (eg “XXX, reduce to min approach speed immediately “)? (or vice versa) I can’t see hydraulics being a limitation, again, in a go around the gear is often coming up as the flaps are travelling up one stage.
However on my A319, the F2 selection is followed immediately by the following note...
If the aircraft speed is significantly higher than "F" speed on the flight path, or the aircraft does not decelerate on the flight path, extend the landing gear in order to slow down the aircraft. The use of speed brakes is not recommended.
The normal “when flaps are at 2” is in the subsequent section.
But is there a restriction / limitation / prohibition on putting the gear out when the flaps are travelling (eg “XXX, reduce to min approach speed immediately “)? (or vice versa) I can’t see hydraulics being a limitation, again, in a go around the gear is often coming up as the flaps are travelling up one stage.
Last edited by compressor stall; 7th February 2019 at 20:17. Reason: typos
Joined: Feb 2002
Aviation Qualifications: AME
Posts: 4,183
Likes: 1,119
From: UK
The hydraulic pumps can only supply a finite flow/pressure.
From Hursts. Airbus Technical part 14. Hydraulics
Each system also has a priority valve to cut off heavy users (flaps, slats, gear, emergency generator) if system pressure gets too low to operate the flight controls.
Joined: Jan 2001
Aviation Qualifications: ATPL
Posts: 1,709
Likes: 35
From: UK
I’ve always taken it that that the FCOM written in such a way to say that you ‘should’ wait for the gear to be down before selecting F3 but not that you ‘must’ (i.e. there’s no limitation)
Joined: Oct 2009
Posts: 1,061
Likes: 4
From: UK
Precisely, if it was a limitation, it would be in the FCOM-LIM. Years ago I remember a good captain denying me flaps 3 whilst the gear was travelling (after admittedly I forgot to configure in time). We finally selected flaps full out at about 1020ft (so 20ft away from our approach gate) to satisfy his limitation. People get so caught up in this crap that they totally miss the big picture. He would have probably rather have executed a go-around than 'stressing' the hydraulics .
Joined: Mar 1999
Posts: 991
Likes: 128
From: big green wheely bin
Precisely, if it was a limitation, it would be in the FCOM-LIM. Years ago I remember a good captain denying me flaps 3 whilst the gear was travelling (after admittedly I forgot to configure in time). We finally selected flaps full out at about 1020ft (so 20ft away from our approach gate) to satisfy his limitation. People get so caught up in this crap that they totally miss the big picture. He would have probably rather have executed a go-around than 'stressing' the hydraulics .