MD80 Side Body Flex
 

Hi All,

Of course the fuselage on airliners flex. As a pilot, this is something that I am certainly aware of. I am a 320 driver. However, I have a question specific to the MD80:

I was on a flight into ONT today on American in an MD80, build date in 1984, so it was an aged lady to be sure. Well, I happen to be sitting in the exit row over the wing on the window seat. It was pretty windy into ONT today, so we were getting a lot of bumps and rolls. I noticed that the fuselage wall was noticeably flexing and I mean several inches in and out. enough that I could easily see and feel the flex of SEVERAL inches. I could have slipped my arm in between the wall and seat at times, however my arm would have been smashed from the flexing wall.

When I was getting off the plane, the gentleman sitting on the opposite side of my row (other window) actually commented to me about the side wall flex. He was pretty unnerved about it and said "wow, that thing was flexing 4 - 6 inches". I just kind of laughed and didnt say much.

Anyway, for all you MD80 guys out there. Is this normal for the type? I was really surprised myself how much flex was easily visable. Looking forward to comments.

Thanks!

An MD-80 will not flex in and out 4 to 6 inches on each sidewall. In turbulence, there will be some modest twisting of the fuselage structure, and flexing fore and aft, which is particularly noticable when seated in the rear of the cabin and looking forward. It's seen most readily in the form of movement in the overhead bins. Perhaps some of the movement you described between the armrest and sidewall was lateral loading of the seat assembly moving toward the sidewall, or alternatively away from the sidewall.

It's funny you say that as a -320 pilot (I'm not Airbus bashing at the moment, but I'll be happy to do so at the drop of a hat :D). When I first came to the airlines years ago from flying corporate, I used to commute somewhat regularly on an A-320. I was always amazed by how much that fuselage flexed and that I could actually SEE the seats/sidewalls/bins moving in relation to one an other - somewhat unnerving! I guess I'm jaded now, because I don't notice any of them doing so anymore (or maybe it's just because I'm already asleep by the time the door closes!).

Sorry, nothing of any actual value in this post - just chuckling and reminiscing!

I was thinking it was WAY TOO MUCH to be real. But it was still disconcerting to be honest. I have NEVER seen in my 18 years of flying, a plane flex so much. I have been on the 320 for a long time (only bird my airline flies) and never seen anything near this no matter what the ride.