MD-11 flap fairings

[Guest A32X]

Does anyone know why there's a difference in the flap fairing design below?http://www.airliners.net/open.file/1193138/L/http://www.airliners.net/open.file/1194523/L/Thanks!

[Guest Basten_TFF754]

As those Lufthansa MD11's are one of the last built I think it's an aerodynamic update / customer option. Not sure if there are other airlines flying around with the same type of flap fairing (carriages?).______________________________Basten HeidemaProud MD11 AddictFLY DC JETS!

[Guest D17S]

Thought I'd heard the answer before, so I re-checked today.At the very beginning, production had manufactured the first 4 airplanes and handed them over to test flight. As the test flight program progressed, it became apparent there was a problem. The MD11 was a bit shy on its launch fuel burn promise. They needed to increase fuel burn efficiency by 2 percent. Every thing hanging out or off the airplane was MD's potential salvation.Maybe a better design on that flap faring? It had worked with the 747-1/2 plyon design. Maybe here too. First, MD built a metal frames to replace the flap fairings. Then, they attached a plywood skin to simulate a proposed re-shape of the faring. They flew the airplane with this frame/plywood contraption in place of the original flap faring. The onboard engineers strained over their onboard instrument packages. Would it help? Could they measures any burn changes? The drama unfolded. The guy I spoke to was a flight mechanic on these MD11 test flights. They would take the airplane out and get a set of in-flight measurements, then land. He'd go out and hack off a bit of the wooden faring (ahhh, I mean, "reshape!") then go fly again. He said they used lots of bondo and speed tape to fine tune adjustments. Other than the onboard measurements, there was not much scientific about this. It was all about experimenting with different shapes just to see what worked. It seems MD was right up against the wall with this. The production setup was already building fairings with the original designs. Early customers were offered a choice. Pay more for the new faring and / or take a later delivery, or just take the old design. Some opted to just take the original design and some opted to wait a bit for the new parts to become available. That's how there 2 designs finally entered the wild. The winglets went through the same late-stage test flight drill. MD really struggled to find that extra 2% of fuel efficiency! The test flight team took off the existing wingletS and replaced them with metal frames. They then attached a "formable" wooden skin (plywood) to the frame. (Lots of bondo and speed tape to smooth things up.) At one point, the winglet was 10 feet taller than it is now . . . all in the name of the great experiment. They used to just go out and whack off a foot at a time to see if that would help the burn problem. I don't think we're gonna see different winglet designs, though. I assume the original ended up being OK. Notice the windshield wipers park vertically? That was one of the "fixes" the test flight team came up with. The origional design had them parking sideways, but were picking up too much drag. The rain gutters (over the doors) had to go too . . . but I see they some how made a come-back. Quietly, I'm sure . . . after the excitement settled down. I'd give up 2 quarts of fuel on a 10 hour flight so I didn't have to duck through Niagara Falls to get into the airplane on a miserable day. 'Nuf is Enough!) GE got involved. Did you know that one GE MD11 can be 18 inches longer that another? Me too, till today. Look carefully at GE equipped MD11s. Some the GE engines have an extended exhaust nozzle. This center nozzle pokes out the back of tail pipe by about a foot and a half. I understand we have both types, but the beasts roosting on the ramp today only had standard exhaust assemblies. Look for it. (Hey, PMDG. Which one are we gonna get?)Also, look at the air conditioning pack's heat exchanger exhaust configuration. Some will have a movable exit door, some not. MD initially thought a faring door over the exhaust duct would be just the aerodynamic thing. Not so, so it was discovered. Early MD11s will have this exhaust exit door, later production models had the door simply and entirely removed. It's just an overboard port at the outlet of the heat exchanger ducting. That was a fine deal, but the pack developed a rumble. That was fixed by attaching a couple of vortex generators (a little "U" shaped piece of metal!) to the inlet door. Fixed it right up. So, if you are walking by the front of one of these things and see a little "poker-upper" on the inlet door, there will be no exit door. We had both types on the ramp today. Still waiting for that GE ubber-nozzle to show up! Roomer has it, we got some. That would put us up to EVERY imaginable configuration of these dumb things.Fun Facts Let's see, what else . . . ?

[Guest A32X]

Really interesting! If an MD-11 has the 'uber-long' GE nozzle it seems also to have the more aerodynamic flap fairings. I wonder what the fuel burn differences bewteen such a variant and the 'basic' MD-11 are...