Strange looking underside of 737

[wizo]

Not sure where to post this so I'll have a go here. I work in ground ops and noticed the other day that the belly of a 737 at around the area where the wings meet the fusalage had a strange 'rippled' look to it, almost like the effect you see on sand when the tide is going out. I mentioned it to one of the crew who was doing his walkaround who told me it was nothing to worry about and off he went. Just wondered if anyone could shed any light onto what this could be ? it certainly looked peculiar !

[Mr @ Spotty M]

It is well known about and can be seen on about every type of B737 after it has had a few landings.
Used to see it on the 200s, so it has been around for decades and is nothing to worry about.:ok:

[wizo]

Thanks Mr @ Spotty M, any idea what causes it ?

[MathFox]

A hard landing will bend the fuselage, compressing it on the underside. As stresses are strongest near the landing gear, that's where the effects show first and most.

[wizo]

Thanks Matfox :ok: