Flaperon droop on ramp

[Steve Dra 7,588]

It all has to do with the lunar cycle just as it affects wave generation.

When the moon is full and its exerting the most gravitational force on the earth, the surfaces are more prone to droop when not pressurized.  

I know this is true because I read it on the internet.   

[Alpha Floor 237]

It all has to do with the lunar cycle just as it affects wave generation.

When the moon is full and its exerting the most gravitational force on the earth, the surfaces are more prone to droop when not pressurized.  

I know this is true because I read it on the internet.   

 

haha, good one.

 

I have a friend of mine who's an IT technician. Whenever a computer does something that nobody understands, the first thing he says is: Okay people, let's try walking out of the room, and getting back in, maybe that will do it!

 

Surprisingly enough, sometimes systems work like that! haha

[Steve Dra 7,588]

haha, good one.

 

I have a friend of mine who's an IT technician. Whenever a computer does something that nobody understands, the first thing he says is: Okay people, let's try walking out of the room, and getting back in, maybe that will do it!

 

Surprisingly enough, sometimes systems work like that! haha

 

When I was an avionics tech in the Navy, we'd sometimes blame radio communication issues on sun spot activity....sometimes it was actually true.  :wink:

[BrianW 124]

Unlike the other flight controls the only modes the flaperon PCUs have are normal, and bypass. When there’s no hydraulic pressure the PCUs are in bypass mode which allows the flaperon to move freely. They will slowly droop under their own weight when parked. If the PCUs go into bypass mode in flight aerodynamic loads will pull them up. A good example of this is the flaperon during takeoff which is in bypass mode until 100 knots.

 

The other flight controls have also have a blocking/damped mode which behave differently depending on the control surface. The elevator drooping at shutdown it depends on its position when hydraulic pressure is removed. In the case of a failure of both PCUs on an elevator, the PCUs will go to bypass mode until airloads move the elevator within two degrees of being flush. At that point the PCUs will go into blocking mode which hydraulically locks the elevator in place. When you see elevators drooped it’s because the the elevator was more than two degrees trailing edge down when hydraulic pressure was removed. If you remove hydraulic pressure with the elevator up it should not go past the neutral position.

[kevinh 409]

Unlike the other flight controls the only modes the flaperon PCUs have are normal, and bypass. When there’s no hydraulic pressure the PCUs are in bypass mode which allows the flaperon to move freely. They will slowly droop under their own weight when parked. If the PCUs go into bypass mode in flight aerodynamic loads will pull them up. A good example of this is the flaperon during takeoff which is in bypass mode until 100 knots.

 

The other flight controls have also have a blocking/damped mode which behave differently depending on the control surface. The elevator drooping at shutdown it depends on its position when hydraulic pressure is removed. In the case of a failure of both PCUs on an elevator, the PCUs will go to bypass mode until airloads move the elevator within two degrees of being flush. At that point the PCUs will go into blocking mode which hydraulically locks the elevator in place. When you see elevators drooped it’s because the the elevator was more than two degrees trailing edge down when hydraulic pressure was removed. If you remove hydraulic pressure with the elevator up it should not go past the neutral position.

Thanks for the detailed explanation Brian. So why are flaperons often seen not drooping when apparently without hydraulics, as the OP asked?

[BrianW 124]

I don’t have a definitive answer other than there’s nothing system wise that would cause them to droop on one shutdown and not on the next. It most likely comes down to environmental conditions vs.mechanical resistance.

[asadkamal 1]

I have pictures from last week at Vancouver. Couldn't get an AC shot but fortunately there was a Air New Zealand 777 on the ramp. These pictures were taken at least 2 after shutdown if not more. Whats the best way to attach a picture to a reply? , my apologies in advance for my ignorance. 

 

Regards, 

Asad Kamal