Re: Big hailstorm at DFW

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         02 May 95 13:27:38 
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>I heard on the radio this morning that there was a severe hailstorm at DFW
>and that American Airlines has cancelled hundreds of flights because of
>actual or possible damage to their fleet.  There was no mention of other
>carriers.  Is this selective reporting, or was the storm so localized
>that only AA was affected?

Probably a bit selective, though not unduly so.  Since DFW is AA's
primary hub, they had quite a few more planes in the line of fire than
any other airline.  Including the 24 Eagle (commuter) aircraft, AA had
75 aircraft damaged, whereas an airline without a DFW hub such as CO,
NW, TW, UA, or US, rarely would have more than one or two planes there.
Delta has a sizeable hub at DFW, of course, and I'm a bit surprised to
see no mention of damage to their aircraft.

Also, since AA is a local business, there's going to more interest in
them from the reporters on the scene, which doesn't seem unreasonable.

>Is it likely the airplanes are repairable, or does big enough hail do
>fatal damage to an airframe?

I just posted something in misc.transport.air-industry about a similar
incident in Johannesburg that damaged 11 of SAA's aircraft; some took
as long as two months to repair.  While hail can obviously do some
nasty damage, it's not likely to affect the engines or major structure
and thus I doubt it could produce fatal damage to an aircraft on the
ground, though the damage could easily be enough to justify writing
off an older aircraft that didn't have much life left anyway.  This is
only considering aircraft on the ground; flying through a good hail
storm could probably produce enough damage to crash an aircraft were
one dumb enough to fly into one.

>What fraction of a carrier's fleet is typically on the ground at one
>place at one time so that this kind of thing can happen?

In the SAA incident, roughly 20% of their fleet was damaged.  AA was
significantly less than 10%.  Hubs increase the exposure, but most of
the hub-and-spoke carriers have multiple hubs which distributes the
exposure some.  A carrier like Southwest has a lot less exposure.

The worst case is probably an all-international carrier with a single
hub, such as Virgin Atlantic, which has close to half its fleet at
London (albeit split between LHR and LGW) for a few hours each day.
This may be true for sub-fleets within larger carriers too -- around
noon, United has a remarkable number of 747s, at least 25% of their
747 fleet, on the ground at SFO.

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