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Any theories or explanations?

Posted: Sun Aug 17, 2014 9:12 pm
by Copperhead
I have a friend who noticed something odd about their flight a while back, and I was wondering if anybody here could help figure it out?

Here is what they said: They did something weird with the slats on my plane today. It taxied up to the gate with the slats already in takeoff position. They stayed there the whole time it was in the gate and the whole time it taxied. They never moved until we were in the air. I've never seen that done before. Usually the slats would be up in the gate and extended shortly before takeoff. It was actually a bit creepy because it looked like they were broken. It looked that way because the pilots ran standard checks on the flaps and ailerons while we taxied, but the slats didn't move at all. There was nothing wrong with them because they functioned fine on landing, but it was weird. I thought that maybe they had left them down for inspection, but I didn't see any ground crews examining the wings. Besides, if it was an inspection they would've ran checks after, which they didn't. Anybody have any ideas?

Re: Any theories or explanations?

Posted: Sun Aug 17, 2014 11:31 pm
by VNAF ONE
It may help to know what type of aircraft, what airline, and even what location this took place at.

Re: Any theories or explanations?

Posted: Sun Aug 17, 2014 11:42 pm
by Dragon029
If I had to guess, it might have been due to maintenance restrictions on the hydraulic system, but otherwise that's very strange; especially because having them down increases the chance of someone striking them with a vehicle.

It could also be that they had been de-iced or something and needed to be extra-exposed to dry them out or something.

Re: Any theories or explanations?

Posted: Mon Aug 18, 2014 12:29 am
by Turbofan
While not a common occurence, in all of my 20+ years of travel, I've seen slats and flaps down at the gate more than once. Like VNAF said though, it would definitely help to know the aircraft type, airport etc.

It could have also been just an oversight (although very rare) of both pilots not properly checking to make sure the flap lever was all the way up in the 0 position. The way some flap systems work is the slats will deploy first and retract last, so if the flap lever was not properly put back all the way in the 0 position the slats could've still been deployed all the way to the gate. Of course, that's easy for me to say so it's just a possibility, albeit, like I said, small. No judgement here on the pilots, just pointing out a remote possibility.

Sometimes if there is a problem, mechanics will just take a look inside the flight deck to see what it is, so if there was actually was one it was likely resolved within the confines of the cockpit itself. The pilots did not bother to retract the flaps on the way out since they needed to be down anyway for takeoff.

As far as I know, de-icing on commercial jetliners is done only before takeoff, not after landing so I doubt it was that.

Re: Any theories or explanations?

Posted: Mon Aug 18, 2014 4:14 am
by Copperhead
It was an Airbus 319.

Re: Any theories or explanations?

Posted: Mon Aug 18, 2014 3:38 pm
by decaff_42
Yes, De-icing is done before takeoff with gobs of orange liquid they spray on the aircraft. I was one of the last flights out before a blizzard set in bad and it took us a few hours to get de-iced because of the sudden demand by all the planes.

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 1:37 pm
by JupiterBomber79
Anybody experiences this weird Theory from Airbus 320's?

Each time in my travel with Airbus "Cheap Planes" in take off as usual around 20-30 Degree theres nothing like falling off of the flap but Like 1 Hour and 30 Minutes Later landing came and the Flaps were lowered to 30 Degree for like near at the airport decending for the runway then few seconds later Full Flaps came and i notice between 20 Degree Level i saw it was like vibrating but didn't mind it when Full Flaps the flaps were like what the?...It's like gonna fall off from the plane

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 5:57 pm
by Kujo
I tried to read that, and I think it's just the way the plane was built. At an angle it could have looked like it was about to fall off. The shaking could have been the wind or small turbulence. Decaff should know how it looks like that.

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 8:55 pm
by decaff_42
@ Jupiter, Little hard to read that without punctuation... is this a translation?

Anyway, I don't know much specifically about Airbus aircraft, however when you put the flaps down, in addition to providing lift, they also add a lot of drag. This is great because it helps slow the plane down, but as Kujo mentioned, it can cause the flow to separate on the flaps and trailing edge of the wing.

If you treated each segment of the flap like it's own wing, you might see something like this in a wind tunnel:

Image

You can see the flow swirling behind the airfoil on the top section, but below the airfoil, the streamlines are very smooth, or laminar. Those swirls are vortices which can cause vibrations which you might have seen. In general, however, it takes a lot to make an aircraft break. I know Boeing flight test their aircraft to make sure that they will survive some pretty extreme conditions. Under a normal landing, you should never have a wing or flap vibrate off the aircraft unless it hasn't been properly maintained and it is very old and is approaching it's fatigue life.

Flying is pretty darn safe 99.9999% of the time.

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 10:03 pm
by Copperhead
Safer than cars, but its funny how people are still more fearful of flying. :roll:

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 10:19 pm
by decaff_42
The lack of control and general un-naturalness of a human flying can be quite disturbing for many people. I know PhD Engineers who don't like flying.

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 10:21 pm
by Neocon
The vast majority of car crashes don't result in fatalities. :)

Re: Any theories or explanations?

Posted: Wed Oct 22, 2014 11:35 pm
by Gunny
I alwys figure that if I deplaned under my own power without the aid of emergency medical staff it was a good flight ;)

Re: Any theories or explanations?

Posted: Thu Oct 23, 2014 12:33 am
by Copperhead
@Patrick, I know this chart was done a little while back, but I'm pretty sure it still relates well enough today.

Image

@Gunny, "any landing you can walk away from is a good one" lol.