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Boost Covers Aren't Flush On MD80?  
User currently offlineZionstrat From United States of America, joined Apr 2001, 226 posts, RR: 0
Posted (13 years 3 months 5 days 9 hours ago) and read 2630 times:

Sitting on the exit row last night I noticed something that surprised me- It seemed that the 2 inboard boost pump covers were not flush on their leading edges. When we climbed out of the soup we were heading east with the sun setting and at that point it was clear that they were casting shadows forward so the leading edge had to be elevated. The 3rd cover that is farther out on the wing was clearly flush and also did not cast a shadow.

2 questions-
-Is this normal and I've just never noticed it before?
-If so, why would drag be tolerated when it seems this would be so easy to fix?

If this turns out to be another NACA opening answer, I think I’ll give up asking these kinds of questions Big grin


4 replies: All unread, jump to last
User currently offlineDalmd88 From United States of America, joined Jul 2000, 2891 posts, RR: 14
Reply 1, posted (13 years 3 months 5 days 6 hours ago) and read 2600 times:

Very observent. Actually the two middle covers aren't flush. You can't see the most inboard from inside. Anyways, This area of the wing as a large anti-ice heating element that has been attached to the top of the wing. It's a large sheet about eight feet across running from just behind the slats to about three feet from the trailing edge. It doesn't go all the way to the trailing edge because it only covers the fuel tank area. The covers you see are not the actual tank plates but just a aerodynamic cover installed over the plates. They smooth out the opening and prevent water from collecting on the plate on the ground.

MD-80s had a pretty bad icing problem before these were installed. The ice wasn't an aero problem but would break off and get sucked into the engine. That's why they were installed in that area of the wing.

They take about four days to install if those two tank openings come in without leaks. The only nasty part of the job is the sealant that helps hold them on. After fixing all the fuel leaks, drilling the twenty holes for the screws, sanding and priming the wing surface you get like four guys to spread the sealant. Six quarts on the wing and six quarts on the back of the blanket. Then you carry the thing up the ladder and carefully put it in place. I used to wear three pairs of latex gloves while doing this. as one pair got too messy off they came. After sticking it in place you had about 30-45 min to get a giant vacuum bag stuck over it to suck it to the wing for the the 36 hour cure time. It then gets ultrasound inspected to check for voids in the sealant.

How well are they stuck down is the common question. We have changed a very few. Usually becuse both heating elements went bad, but we had one with a sealent failure. It came in with about 40% disboned. Even then we had to use a 5 ton crane to peel it off the wing. I'm glad Delta has got all of our fleet done because I got real sick of that mod after two years.

User currently offlineZionstrat From United States of America, joined Apr 2001, 226 posts, RR: 0
Reply 2, posted (13 years 3 months 5 days 3 hours ago) and read 2560 times:

Wow- Completely different angle than I would have ever imagined-This is why I like this board so much!

It sounds like they actually did an incredible job under the circumstance- I doubt the lip was more than 1/8 inch, but I thought I was looking at the original wing top. From a layman's POV, it's amazing that a retrofit of that size could fit that well.

I do remember the DC9 icing problems, but had no idea that such a significant mod had been offered- I had assumed that changes had been planned into the 80/90 line from the factory.

I'm assuming this was optional as opposed to the result of an AD? I usually ignore these on the commercial side and would have missed it, but this would have been very interesting to see. Also here's a shot in the dark- Does anyone have photos of this mod underway? I can imagine what you are getting at, but it would be very interesting to see-

Dalmd88, thanks again for the details!

User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 10
Reply 3, posted (13 years 3 months 3 days 9 hours ago) and read 2488 times:

The heat blankets are indeed optional. TWA didn't use them but AA does. (Lots of mod money going there)
They are needed on the -80 series because the wings are more flexible and the ice that forms when they're on the ground in high humidity conditions breaks off and FOD's the engines. At TWA in one year they took out eight JT8 fan sections due to ice FOD.
There has been a requirement levied by the FAA to do a "bare hand" check of the wing surface prior to taxi since the aircraft were first found to have this problem.
The DC-9-10 to 50 and the 717 wing is not so flexible thus not so much a problem. The FEDS want the check done there anyway.
There have been numerous tests done but the most dramatic I've seen (we use the video in our training classes) is the one where a plane was flown to SEA and in a two hour period over 3/4 of an inch of ice formed on the upper wing.
When the lake was filled in Tempe AZ, a couple of years ago, (two miles east of PHX) what had been a non-issue quickly became a big problem. We actually had to de-ice the planes at the gate on turn-around flights due to the ice that formed with an East wind.

One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently offlineBrons2 From United States of America, joined Sep 2001, 3035 posts, RR: 4
Reply 4, posted (13 years 3 months 3 days 4 hours ago) and read 2471 times:

Ice ingestion also caused a crash of an SAS MD-81 in 1991.


Luckily, nobody was hurt despite the fuselage breaking into 3 pieces (!)

Firings, if well done, are good for employee morale.
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