Hail damage

[gmcjetpilot]

Originally Posted by CraigH@KRPH

I took a mini tour of the Shepard AFB flightline a few years back. It was the height of the hail season in North Texas, and all of the T-37s / T-38s had thick padded blanket wing envelopes to protect against hail. They must work, because we sure get some nasty stuff up this way on occasion.

Interesting, that was what I was thinking but did not know if it was practical. For home base sure but cross country the pads would be too much to carry around.

Hummmm faster with the dents, I have the ball peen in hand now. Any volunteers?

[mdredmond]

Hmmm. I thought these planes derived a lot of their strength from the stressed-skin construction? Seems like dents everywhere would be begging something to fold or collapse. I'm not sure I'd want to fly around in a plane that was so banged up.

[gmcjetpilot]

Originally Posted by mdredmond

Hmmm. I thought these planes derived a lot of their strength from the stressed-skin construction? Seems like dents everywhere would be begging something to fold or collapse. I'm not sure I'd want to fly around in a plane that was so banged up.

NOT A BAD QUESTION. Some aircraft use the skin to take compression and tension but not in our case.

Flat sheet metal does not take any compression, at least the allowable is very very low. Some manufactures add stringers and tie that to the side of the body. In our case all the shear, bending comes out in the front and rear spar. The torsion is taken as a "couple" between the front and rear spar. Basically the same with the Horz stab.

The design assumes all the bending loads are in the spars (wing horz-stab).

The torsion is in the skin, but the dents don't really affect this. It ain't goodness either.

The fuselage top is almost a faring in that we use the heavy stringer or angle along the "gunnel" (boat term). This angle is called a longeron on aircraft (major structure running from front to rear). The skin on the top of the fuelage is important but not critical.

As long as it is not sharp edge creases or a sharp stress concentration or stress riser where a crack can start, it is not bad.

Disclaimer - It could cause problems? A structural aerospace engineer would need to evaluate by close inspection. I get $150.00 and hour.

[Alex]

Originally Posted by gmcjetpilot

The torsion is in the skin, but the dents don't really affect this. It ain't goodness either.

As long as it is not sharp edge creases or a sharp stress concentration or stress riser where a crack can start, it is not bad.

Why do you think the dents wouldn't affect the torsion buckle limit of the skin? I would expect them to, and the only way to test is with destructive testing.

[jcoloccia]

There are 2 RV's up here at Fox in Lancaster that are pretty beat up from hail and apparently they are just fine. Take it for what it is...anecdotal data

[photoadjuster]

The hail damage does not look any worst than my Skylane. Flown 1,000 since the damage.

You are exactly right, it is 5 knots faster than it should be.

Mike Stephenson

[txaviator]

Your post reinforces the 'hammered' 172's (and a Tomahawk mixed in) at my original flight school. I remember preflighting and thinking "what the **** am I about to fly?" In the end, they all still flew just fine....but what did I know back then?