Silly (?) 777 wing question . . .

[pax domina]

I had a good view of the trailing edge of the left wing when on an ATL to MCO 777 earlier today. Please forgive me (since I am not a pilot and people's lives do not depend on me knowing this, and I even still get my debits and credits reversed from time to time) if I say ailerons when I should say flap(s), or vice versa. (Or is a flap just a type of aileron?) My "All You Ever Wanted To Know About Flying" book is still out on loan, so I can't easily look it up. What I mean to talk about is the movable part of the trailing edge of the wing that is located on the *inside* of the wing (nearest the fuselage). I think these are the flaps.

Well, just *outside* of the flaps (or should I say "flap", since I could only see one of them?) there was this other little moveable trailing piece of wing. The strange thing was not that it moved, but that it seemed to, well, bounce around. It didn't look like it was under any sort of control . . . it honestly did look like it was, um, flapping around quite freely. I think I noticed most of this movement during climb and descent, as I seem to recall it remained fairly "steady" during the (brief) cruise.

On the clinb, this sight caused my brief moment of anxiety. I figured the climb was okay, so I wasn't as much bothered when I saw it bouncing around during the descent.

Is this normal, and does anyone know why it happens? Does it have something to do with those ridiculously large engines? (IMHO four smaller engines would have been much more aesthetically pleasing.)

On to more trivial matters . . . the IFE on the 777 wasn't working (not a big deal on a 58 minute flight, and I prefer to read anyway). There were little "remotes" in the armrests. These little remotes also contained the light switches *and* the cabin crew call button. Well, before we took off, I must have accidentally hit the button with my elbow, because the crew member working the section asked I had pushed the call button. "No," I answered, "I must have hit it accidentally with my elbow. Sorry." "That's okay," she smiled, "it's easy to do." "It's very easy to do, didn't they think of that when they put them in?" "No, they designed them and didn't bother to talk to the flight attendants or the passengers."

I believe that the little "dings" heard before take off (and during descent)in the cabin are signals to the flight attendants. Well, I heard a lot of dinging going on during the descent, and I have a feeling it may have been nothing more than elbows hitting the call buttons!

On a positive note, I had a very nice chat with some deadheading pilots while sitting in the departure lounge in ATL. I gave them the address of this web site. So now I've recommended this site to a grand total of four airline pilots. I wonder if in a future life I will be punished or rewarded for having done this. :)

[leftwingdownabit]

Hi Pax Domina,

Just a guess here, but was the flappy bit part of the in flight spoilers which come into play according to the logic of the computers during the climb and descent phases of flight?? In cruise they will not be required due to no need for large manouvers - hopefully! Feel free to shoot me down if I spout b/s!!

[mik]

The trailing edge of a large aircraft has lots of panels which move in/out/up/down.
Starting from the aircraft body, you will typically find firstly a section of wing flap. During cruise, it is retracted into the wing. During takeoff and landing, it comes out and down. This makes the wing generate lift at slower speeds, and also adds drag. It comes out in stages, selectable by the pilot. The slower the aircraft needs to fly, the more the flap comes out. By the way, at the front, or leading edge of the wing are slats. These also make the wing generate lift at slower speeds.

Next is typically the highspeed aileron. This moves up and down. If it moves up, the wing generates slightly less lift, and the aircraft will bank towards the wing. If it moves down, the wing generates slightly more lift and the aircraft will bank away from the
wing. This is called the high-speed aileron because it is used during both lowspeed and highspeed flight.

Next comes more flaps. This is usually the largest section of flaps on the wing.

Finally, you get to the low-speed aileron. This does the same as the high-speed aileron, but is only used at lowish (less than 200mph-ish, depends on the aircraft). speeds. It behaves like the high-speed aileron. This will be the bit you saw apparently bouncing about in the breeze. Like all the other bits of wing, it is under control of the pilot (or autopilot), and does at times move fairly abruptly up and down. Its supposed to!

The ailerons on each wing work together, so when the ailerons on the left wing go down, the ailerons on the right wing go up and the aircraft will bank to the right.

On top of the wings are spoilers (or airbrakes). These have several purposes. At low speeds, they help bank the aircraft. You can sometimes see them moving up slightly when the lowspeed aileron moves up.
The spoilers are also used to slow the aircraft down and let it descend quickly without building up forward speed, for example when air traffic control tell the pilots they have to descend to a certain altitude without exceeding a certain speed. You can sometimes feel and hear a gentle rumble when they are up. Finally, the spilers are used on touchdown to both slow the aircraft down and to significantly reduce the lift the wing is producing, so that more weight is on the wheels.

These descriptions are generic, and do vary a lot among aircraft. For example, some large jets have ailerons that droops down during takeoff and landing, so they also act as flaps!

Fascinating things, aircraft wings.

[Jim lovell]

The wing on the 727 is an absolute masterpiece. All of the high lift devices etc just look fascinating(of course this aircraft was designed with short field performance in mind)when they all pop out

[pax domina]

I'm going to show my ignorange by posting this, but if you are referring to the trailing edge of the wing nearest to the fuselage . . . yes, *very* impressive when fully extended.

Great, that last bit sounds more appropriate for Jet Blast! :)

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Laat me het meer oversteken en ik zal niet bang meer zijn van een beek.

[Nostromo]

Slightly off topic, but I read in GO magazine that the engine on a 777 was as big as the body of a 737. Is that true? If so, why waste all that fuel, just fill the engine pods with politicians and get them to blow out lots of hot air...?

[pax domina]

My Collins Jane's Civil Aircraft book (aka my little book of aeroplanes) says, on page 55,

"Fun Fact: the 777's engines, the most powerful aero engines ever built, are housed in nacelles as wide as a 737's fuselage."

On this side of the pond it is an election year. Sunday I unplugged my telephone and answering machine (the caller ID unit I have would list any incoming calls I missed) because of the endless (seemingly one every hour) calls I was receiving from "out of area". Not that I bothered to pick them up - but between the phone ringing, and then hearing the answering machine pick up even after I had unplugged the phone . . . I had to do *something*.

I suspect they were "vote for so-and-so" calls. I am on the Florida "no sales solicitation" calls list, but I know charities may still phone, and I believe campaign calls are also allowed.

How many 777s do you reckon could be powered by the collective hot air emitted by the World's politicians?

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Laat me het meer oversteken en ik zal niet bang meer zijn van een beek.

[Hippo]

Back to the original question-
The bit of the wing you probably saw moving was the flaperon. On the 777 that lies just outboard of the inboard flap and as it's name suggests acts in two ways. At cruising speeds the flaperon acts as a high speed aileron with the left and right flaperons acting differentially. At low speeds (ie Approach) the flaperon acts as a flap with both left and right flaperons moving down together.

Hippo (If pigs can't fly then neither can I!)

[pax domina]

Flaperon? Is it just me or does it sound quite like "flap around"? Which is what it did . . . moving quickly, and seemingly at random. Movements that quick would have to be computer conrolled.

Thanks for the info . . . I'll keep a close watch if I'm ever again in a 777.

[criticalmass]

Hippo's nailed it.

The inner or high-speed aileron is the bank control surface at high speed (usually as soon as flaps are fully retracted after takeoff, it is linked to the flap-lever position on the 747-400, dunno abt the 777 though it may well be similarly-linked) and it is indeed under computer control via the selected flight mode on the autopilot.

I recently flew to and from Malaysia on Lauda Air 777-200IGW, OE-LPB, and spent the return flight watching the trailing edge doing its stuff. In smooth air the high-speed aileron moves very slightly but once the air becomes rougher you will see it moving regularly, and at times, rapidly.

The outer aileron (towards the wingtip) only moves at relatively low airspeeds, and if you observe prior to takeoff you'll see it droops downwards slightly with the flaps for takeoff but becomes flush with the rest of the trailing edge once the flaps are fully retracted.

At slow speeds sometimes you will also see the spoiler panels lifting slightly to assist the ailerons on the downgoing wing. (I noted this on the final turn onto the glideslope returning to Sydney.)

[Hippo]

Thanks for the vote of confidence Critical Mass.
Flaperon is a combination of the words "Flap" and "elevator".
Similar to the naming concept of Concorde's Elevons (Elevators and Ailerons!)

Hippo. (If pig's can't fly then neither can I!)