Muddassir
Topic Author
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Joined: Thu Jan 21, 2016 9:58 am

Automatic Flaps

Wed May 03, 2017 8:23 am

With so much automation in modern aircraft especially airliners, why Flap extension /retraction is manually controlled. Except for A380 , where flaps retract automatically from 1+F to 1 once speed increases beyond 212 Knots, IIRC. Nothing being a technological challenge anymore, what could be the reason.
Apologies if this has been discussed earlier.
 
Flow2706
Posts: 223
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Re: Automatic Flaps

Wed May 03, 2017 8:29 am

The A320 also has flap auto retract from 1+F to 1 - if the takeoff weight is heavy the minimum speed in clean configuration can approach or exceed the maximum speed in 1+F, so the flaps retract to archive a margin between minimum and maximum speeds. Its not unusual to see the auto retract in operation at high weights in normal operations (contrary to alpha-lock, which should not activate unless you screwed up).
 
gloom
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Re: Automatic Flaps

Wed May 03, 2017 8:38 am

A couple of reasons, in random order:
1. GA procedures
2. high drag in case you need to go below MLW
3. flying in turbulent

plus probably a hundred more reasons, which are not off the top of my head at the moment.

It's not difficult to handle them, but useful to control them.

Cheers,
Adam
 
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Starlionblue
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Joined: Fri Feb 27, 2004 9:54 pm

Re: Automatic Flaps

Wed May 03, 2017 11:11 am

Muddassir wrote:
With so much automation in modern aircraft especially airliners, why Flap extension /retraction is manually controlled. Except for A380 , where flaps retract automatically from 1+F to 1 once speed increases beyond 212 Knots, IIRC. Nothing being a technological challenge anymore, what could be the reason.
Apologies if this has been discussed earlier.


Because conditions vary and there is seldom an exact number or time for retraction or extension. Flaps are a way to manage speed and configuration. Just to mention one thing, on some departures you accelerate at 1500 feet and others at 3000 feet.

As Flow2706 mentions the 320 has auto-retraction, as do the 330 at 200 knots and the 350 at 210 knots. Not a new feature really. The 1+F to 1 auto-retraction on FBW Airbuses has to do with speed restrictions on departures, a time of heavy workload.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
CosmicCruiser
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Re: Automatic Flaps

Wed May 03, 2017 2:02 pm

using the example you posted re: the A380, the MD-11 had a similar auto flap overspeed protection that would not allow landing flaps above a given speed. I remember one crew that got to see it work first hand.
 
26point2
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Joined: Wed Mar 03, 2010 6:01 am

Re: Automatic Flaps

Wed May 03, 2017 3:18 pm

North American/Rockwell Sabreliner biz jet had a simple, but effective, auto deploy mechanism for the leading edge slats. Springs. Slats controlled by aerodynamic load and not by the pilot.
 
BravoOne
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Re: Automatic Flaps

Wed May 03, 2017 3:41 pm

Not exactly the same design but the 787 has automatic cruise flaps that operate independent of any pilot action to deploy very slightly above 22,000 so as to enhance the aerodynamics in cruise.
 
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Starlionblue
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Re: Automatic Flaps

Wed May 03, 2017 11:38 pm

CosmicCruiser wrote:
using the example you posted re: the A380, the MD-11 had a similar auto flap overspeed protection that would not allow landing flaps above a given speed. I remember one crew that got to see it work first hand.


The 330 and 350 also have flap overspeed protection with auto retraction. However this is not the same system as the flap auto-retraction from 1+F to 1 on climbout.

BravoOne wrote:
Not exactly the same design but the 787 has automatic cruise flaps that operate independent of any pilot action to deploy very slightly above 22,000 so as to enhance the aerodynamics in cruise.


As does the 350.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Horstroad
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Re: Automatic Flaps

Thu May 04, 2017 1:50 am

Starlionblue wrote:
CosmicCruiser wrote:
using the example you posted re: the A380, the MD-11 had a similar auto flap overspeed protection that would not allow landing flaps above a given speed. I remember one crew that got to see it work first hand.


The 330 and 350 also have flap overspeed protection with auto retraction. However this is not the same system as the flap auto-retraction from 1+F to 1 on climbout.

The Flap Limit Function on the MD11 can indeed be used as a form of flap auto extend. The Flap Control Mechanism can limit flap position from 22 to 50 degrees. So once you are at speeds that allow for flaps 22 you just set flaps 35 or 50 and the Flap Limit System supplies a limit to the flap positions as a function of airspeed.
Of course as this is not the intended purpose of the system, using it this way causes some damage, so it must not be done. Flap limiting is done mechanically by a cam and cam follower. Usually it comes into action rarely, only under overspeed conditions, so wear is not really an issue. But when it is used almost every single cycle for convenience, the mechanical parts wear out very quickly.
 
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BawliBooch
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Re: Automatic Flaps

Thu May 04, 2017 2:41 am

26point2 wrote:
North American/Rockwell Sabreliner biz jet had a simple, but effective, auto deploy mechanism for the leading edge slats. Springs. Slats controlled by aerodynamic load and not by the pilot.

The An-2 had a similar system - 5 decades back!
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thepinkmachine
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Re: Automatic Flaps

Thu May 04, 2017 5:18 am

BawliBooch wrote:
26point2 wrote:
North American/Rockwell Sabreliner biz jet had a simple, but effective, auto deploy mechanism for the leading edge slats. Springs. Slats controlled by aerodynamic load and not by the pilot.

The An-2 had a similar system - 5 decades back!


AFAIK, the first plane to use it was some pre-WW2 Messerschmitt. As for automatic flaps, I was told MIG-21 flaps were fully automatic. Not practicable on transport category airplanes though, for reasons stated in above posts.
"Tell my wife I am trawling Atlantis - and I still have my hands on the wheel…"
 
trijetsonly
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Re: Automatic Flaps

Thu May 04, 2017 7:05 am

Is anyone here familiar with the Tu-154 flap system? I've heard stories about a semi-automatic flap system as well.
Happy Landings
 
GalaxyFlyer
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Re: Automatic Flaps

Fri May 05, 2017 3:05 am

The North American Sabre fighters and Sabreliner business jets, along with the Helio Courier and AN-2, had Handley-Page slats which are not spring loaded. They are balanced on AOA and just flop out. On the F-100, the preflight check was to manually push them in and let them droop to see they moved smoothly. In flight a quick g pull at around 350-400 knots checked for symmetrical deployment before low level high-g turns.
 
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77west
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Re: Automatic Flaps

Sat May 06, 2017 12:34 am

Cant believe no one mentioned it but Boeing has auto-retract as well:

http://www.pprune.org/archive/index.php/t-260720.html

Called "flap load relief" although I think it is meant for inadvertent speed increases rather than normal ops.
77West - AW109S - BE90 - JS31 - B1900 - Q300 - ATR72 - DC9-30 - MD80 - B733 - A320 - B738 - A300-B4 - B773 - B77W
 
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Starlionblue
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Re: Automatic Flaps

Sat May 06, 2017 6:30 am

77west wrote:
Cant believe no one mentioned it but Boeing has auto-retract as well:

http://www.pprune.org/archive/index.php/t-260720.html

Called "flap load relief" although I think it is meant for inadvertent speed increases rather than normal ops.


Indeed. As mtioned, flap load relief and flap auto-retract on the 'bus are not the same system. Flap load relief activates in case of an (inadvertent) flap overspeed. Flap auto-retraction happens on climbout at 200 knots (330) or 210 knots (350), presumably to decrease workload in a situation when you are accelerating fast and can easily overspeed. The flaps retract but the slats stay out.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
KentB27
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Re: Automatic Flaps

Sat May 06, 2017 9:33 am

trijetsonly wrote:
Is anyone here familiar with the Tu-154 flap system? I've heard stories about a semi-automatic flap system as well.


Sadly I don't think there's really anyone who hangs out on a.net who has extensive experience flying TU-154's or really any other Russian birds. Of course somebody can correct me if I'm wrong about that but I've searched for stuff like what you mentioned and not dug up much.
 
CosmicCruiser
Posts: 2392
Joined: Tue Feb 22, 2005 3:01 am

Re: Automatic Flaps

Sat May 06, 2017 10:33 pm

quoting Horstroad.."The Flap Limit Function on the MD11 can indeed be used as a form of flap auto extend. The Flap Control Mechanism can limit flap position from 22 to 50 degrees. So once you are at speeds that allow for flaps 22 you just set flaps 35 or 50 and the Flap Limit System supplies a limit to the flap positions as a function of airspeed.
Of course as this is not the intended purpose of the system, using it this way causes some damage, so it must not be done. Flap limiting is done mechanically by a cam and cam follower. Usually it comes into action rarely, only under overspeed conditions, so wear is not really an issue. But when it is used almost every single cycle for convenience, the mechanical parts wear out very quickly."


for the reason you mention we were NEVER allowed to do that. In fact it was stressed that being under flap ext. speed is better yet.
 
maxpower1954
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Re: Automatic Flaps

Sun May 07, 2017 3:47 am

thepinkmachine wrote:
BawliBooch wrote:
26point2 wrote:
North American/Rockwell Sabreliner biz jet had a simple, but effective, auto deploy mechanism for the leading edge slats. Springs. Slats controlled by aerodynamic load and not by the pilot.

The An-2 had a similar system - 5 decades back!


The Sabreliner also goes five decades back - first flight 1958.

I flew it a little back in the early 1980's and you could easily push the slats by hand to the retracted position.
 
Muddassir
Topic Author
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Re: Automatic Flaps

Sun May 07, 2017 10:53 am

Why should any of the above limitations inhibit use of auto flap deployment. As with all other automated systems, this would too have inputs from various other systems onboard, to determine which phase of flight rather approach or take off phase the aircraft is, what are the speeds, what are the thrust settings, what kind of approach is flown, hence the system can determine and then set the appropriate flap angle. Similarly, in case of GA,
Needless to say, manual override is always there.
 
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Starlionblue
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Re: Automatic Flaps

Sun May 07, 2017 12:13 pm

Muddassir wrote:
Why should any of the above limitations inhibit use of auto flap deployment. As with all other automated systems, this would too have inputs from various other systems onboard, to determine which phase of flight rather approach or take off phase the aircraft is, what are the speeds, what are the thrust settings, what kind of approach is flown, hence the system can determine and then set the appropriate flap angle. Similarly, in case of GA,
Needless to say, manual override is always there.


Arrivals and departures vary widely among airports. Also any two arrivals to the same port will vary given traffic and weather. Arrival profile management is one of the more involved parts of flying an airliner. We need the ability to fine tune the profile by manually controlling configuration.

Just to cite one thing, extending flaps early gives means slowing down earlier, or vice-versa.

On the 350, the ND "magenta line" (which is green but whatevs...) shows points for slat/flap deployment. However these are "ideal condition" points; guidelines if you will. On an given day, the pilot flying would correctly vary configuration to fit with current conditions.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

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