Moderators: richierich, ua900, PanAm_DC10, hOMSaR
citationjet wrote:Retracting the flaps (and leading edge slats) keeps them from getting damaged by ground equipment at the gate.
cathay747 wrote:citationjet wrote:Retracting the flaps (and leading edge slats) keeps them from getting damaged by ground equipment at the gate.
I have the opposite question from the OP and it's funny this thread came up because I've been wondering about this for some.
Your explanation above is of course the correct & obvious answer but...in many a YouTube trip-report video, I've seen lots of cases where on AA Airbus narrowbodies, particularly here at PHX, where the slats & flaps are not fully retracted after landing...looks like they're only brought up to the takeoff position. Why would that be in a place like PHX where there is no slush/snow/ice issue as mentioned by the poster above? I think I've seen it at DFW too.
Cathay777300ER wrote:I would also say in some airports with longer taxi time it will save enough fuel to make it reasonable to retract the flaps.
paullam wrote:cathay747 wrote:citationjet wrote:Retracting the flaps (and leading edge slats) keeps them from getting damaged by ground equipment at the gate.
I have the opposite question from the OP and it's funny this thread came up because I've been wondering about this for some.
Your explanation above is of course the correct & obvious answer but...in many a YouTube trip-report video, I've seen lots of cases where on AA Airbus narrowbodies, particularly here at PHX, where the slats & flaps are not fully retracted after landing...looks like they're only brought up to the takeoff position. Why would that be in a place like PHX where there is no slush/snow/ice issue as mentioned by the poster above? I think I've seen it at DFW too.
You may look this one up. Airbus recommends leaving flaps at 1 at hot airports. It has to do with heat (obviously), I think it’s about fuel temperature or hydraulic fluid temperature. There are a couple of threads about that on this site.
paullam wrote:cathay747 wrote:citationjet wrote:Retracting the flaps (and leading edge slats) keeps them from getting damaged by ground equipment at the gate.
I have the opposite question from the OP and it's funny this thread came up because I've been wondering about this for some.
Your explanation above is of course the correct & obvious answer but...in many a YouTube trip-report video, I've seen lots of cases where on AA Airbus narrowbodies, particularly here at PHX, where the slats & flaps are not fully retracted after landing...looks like they're only brought up to the takeoff position. Why would that be in a place like PHX where there is no slush/snow/ice issue as mentioned by the poster above? I think I've seen it at DFW too.
You may look this one up. Airbus recommends leaving flaps at 1 at hot airports. It has to do with heat (obviously), I think it’s about fuel temperature or hydraulic fluid temperature. There are a couple of threads about that on this site.
workhorse wrote:Another interesting question is why there is an inconsistency on when the flaps are retracted. Some pilots retract them immediately after leaving the runway while others (within the same airline) taxi with full flaps almost all the way to the gate. Shouldn't there be a checklist saying something like:
When leaving the runway:
- autobrake: off
- spoilers: down
- flaps: 0
- strobes: off
- contact ground
- ...
?
cathay747 wrote:paullam wrote:cathay747 wrote:
I have the opposite question from the OP and it's funny this thread came up because I've been wondering about this for some.
Your explanation above is of course the correct & obvious answer but...in many a YouTube trip-report video, I've seen lots of cases where on AA Airbus narrowbodies, particularly here at PHX, where the slats & flaps are not fully retracted after landing...looks like they're only brought up to the takeoff position. Why would that be in a place like PHX where there is no slush/snow/ice issue as mentioned by the poster above? I think I've seen it at DFW too.
You may look this one up. Airbus recommends leaving flaps at 1 at hot airports. It has to do with heat (obviously), I think it’s about fuel temperature or hydraulic fluid temperature. There are a couple of threads about that on this site.
Hey thanks! Such a quick answer, and it's logical. My case is closed.
cathay747 wrote:Cathay777300ER wrote:I would also say in some airports with longer taxi time it will save enough fuel to make it reasonable to retract the flaps.
Gee, I like your screen-name! LOL
How does retracting slats/flaps on the ground save fuel? You've totally lost me on that comment.
Cathay777300ER wrote:cathay747 wrote:Cathay777300ER wrote:I would also say in some airports with longer taxi time it will save enough fuel to make it reasonable to retract the flaps.
Gee, I like your screen-name! LOL
How does retracting slats/flaps on the ground save fuel? You've totally lost me on that comment.
It's mainly about extra drag requiring more thrust from the engine. The affect of the extra drag might be negligible on short taxis but in larger airports with many start stop taxing it can account to enough fuel to make retracting the flaps make sense.
flight152 wrote:Uh. What? There is no basis of fact on any of this, nice try though.
Cathay777300ER wrote:cathay747 wrote:Cathay777300ER wrote:I would also say in some airports with longer taxi time it will save enough fuel to make it reasonable to retract the flaps.
Gee, I like your screen-name! LOL
How does retracting slats/flaps on the ground save fuel? You've totally lost me on that comment.
It's mainly about extra drag requiring more thrust from the engine. The affect of the extra drag might be negligible on short taxis but in larger airports with many start stop taxing it can account to enough fuel to make retracting the flaps make sense.
mandala499 wrote:flight152 wrote:Uh. What? There is no basis of fact on any of this, nice try though.
Maybe he taxies his jet in the middle of typhoons all the time.
conaly wrote:The issue with Airbus on flaps 1 is afaik only valid for A320, A330, A340 and A380. On the A350 they fixed the "issue". I've noticed the extracted flaps a few years ago when I arrived in Kuala Lumpur on Lufthansa A343 and asked the flight crew afterwards about that. They explained something with air circulation and cooling issues. Last year I arrived in HND on LH A359 during very hot weather (around 37°C) and there they fully retracted the flaps after landing. The crew said, that this problem doesn't exist anymore on A350 as it has some venting holes in that slats (or something similar).
zeke wrote:The issue has actually been fixed across the board, the practice is continued to retain commonality as most operators have a mixed fleet of new and old aircraft.
If an airline has all newish aircraft, or aircraft with the new sensors the procedure is not required for above 30 degrees, however the other requirements are retained.
Scarebus34 wrote:I mean, why do you put the gear up if you're just going to put it back down again?
VirginFlyer wrote:mandala499 wrote:flight152 wrote:Uh. What? There is no basis of fact on any of this, nice try though.
Maybe he taxies his jet in the middle of typhoons all the time.
It does raise an interesting question though... if one were to taxy on a conveyor belt, what would be the ideal flap setting?
V/F
stratclub wrote:VirginFlyer wrote:mandala499 wrote:Maybe he taxies his jet in the middle of typhoons all the time.
It does raise an interesting question though... if one were to taxy on a conveyor belt, what would be the ideal flap setting?
V/F
I saw that episode of Myth Busters. Probably one of the most bogus "Myth" they ever wasted airtime on. For the proper flap setting, you would have to consult the abnormal operating procedures check list. Just a guess, but it would be the same flap setting you would use if you were backing into a mountain.
VirginFlyer wrote:mandala499 wrote:flight152 wrote:Uh. What? There is no basis of fact on any of this, nice try though.
Maybe he taxies his jet in the middle of typhoons all the time.
It does raise an interesting question though... if one were to taxy on a conveyor belt, what would be the ideal flap setting?
V/F
zanl188 wrote:Flaps up recommended after landing on some aircraft to kill lift and add weight to wheels - enhances braking.
zanl188 wrote:Flaps up recommended after landing on some aircraft to kill lift and add weight to wheels - enhances braking.
zanl188 wrote:Flaps up recommended after landing on some aircraft to kill lift and add weight to wheels - enhances braking.
Starlionblue wrote:Cathay777300ER wrote:cathay747 wrote:
Gee, I like your screen-name! LOL
How does retracting slats/flaps on the ground save fuel? You've totally lost me on that comment.
It's mainly about extra drag requiring more thrust from the engine. The affect of the extra drag might be negligible on short taxis but in larger airports with many start stop taxing it can account to enough fuel to make retracting the flaps make sense.
At taxi speeds, any extra drag would be practically non-existent.
cathay747 wrote:
There is NO aerodynamic "drag" at taxi speeds. There are no aerodynamic forces acting on ANYTHING at taxi speeds
cathay747 wrote:Starlionblue wrote:Cathay777300ER wrote:
It's mainly about extra drag requiring more thrust from the engine. The affect of the extra drag might be negligible on short taxis but in larger airports with many start stop taxing it can account to enough fuel to make retracting the flaps make sense.
At taxi speeds, any extra drag would be practically non-existent.
There is NO aerodynamic "drag" at taxi speeds. There are no aerodynamic forces acting on ANYTHING at taxi speeds, period. I would be most curious to know where on EARTH Cathay777300ER is getting this notion. The only "drag" on a taxiing jet, if you want to call it that, would be friction from the tires on the pavement induced by gravity & weight. Good God in heaven!
workhorse wrote:Another interesting question is why there is an inconsistency on when the flaps are retracted. Some pilots retract them immediately after leaving the runway while others (within the same airline) taxi with full flaps almost all the way to the gate. Shouldn't there be a checklist saying something like:
When leaving the runway:
- autobrake: off
- spoilers: down
- flaps: 0
- strobes: off
- contact ground
- ...
?
N766UA wrote:Every takeoff is different and not every one requires the same flap setting.
workhorse wrote:Another interesting question is why there is an inconsistency on when the flaps are retracted. Some pilots retract them immediately after leaving the runway while others (within the same airline) taxi with full flaps almost all the way to the gate. Shouldn't there be a checklist saying something like:
When leaving the runway:
- autobrake: off
- spoilers: down
- flaps: 0
- strobes: off
- contact ground
- ...
?
cathay747 wrote:There is NO aerodynamic "drag" at taxi speeds. There are no aerodynamic forces acting on ANYTHING at taxi speeds, period. I would be most curious to know where on EARTH Cathay777300ER is getting this notion. The only "drag" on a taxiing jet, if you want to call it that, would be friction from the tires on the pavement induced by gravity & weight. Good God in heaven!
VSMUT wrote:Is that inconsistency something you have noticed within one airline on one type?
Starlionblue wrote:It would be inaccurate to say there is no aerodynamic drag at taxi speed. You're moving an object through the air, after all. It's just so little drag as to be insignificant.
AirKevin wrote:One less thing for the ground crew to crash into if the flaps are retracted.