Seaplane down off Miami Beach....

"George Patterson" wrote in message
news:ixoqf.29956$CL.291@trnddc04...
Jim Macklin wrote:
Reports I saws this morning said that the NTSB said they found a fatigue
crack in the main spar, maybe the conversion was not done well or the
maintenance was not though enough. I'll bet the fleet is grounded and
they require immediate, "before further flight" NDT inspections of the
wings, etc.

Chalk's has voluntarily grounded thier Mallards and is performing an
exhaustive test of the spars on one of them now. The NTSB rep voiced the
opinion that age alone would not be sufficient to cause this failure; some
additional stress would be required.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

How frequently were these airplanes operated off of water? Wouldn't water
takeoff's and landings typically be more stressful (because you're getting
bashed around by waves) than landing on a nice smooth runway? I suspect it
would be even worse if you dug in a wing float or hit a wave with a wing
float "at speed".

KB

"Kyle Boatright" wrote in message
How frequently were these airplanes operated off of water? Wouldn't water
takeoff's and landings typically be more stressful (because you're getting
bashed around by waves) than landing on a nice smooth runway? I suspect
it
would be even worse if you dug in a wing float or hit a wave with a wing
float "at speed".

The fleet operates off the water every day. Chalks opts to land on the water
at stations were runways are available. It's part of the experience for the
passengers. Seaplane operations are much more demanding than landplane
operations, particularly in sal****er environs. These airplanes were built
tough, but they were designed when finite element analysis was in it's
infancy.

What the press hasn't mentioned, because they don't know, is that seaplane
operations have more incidents than similar landbased operations. It comes
with the territory. Chalks has had numerous hard landings were floats have
been knocked off. A Chalk's Mallard hit a bridge piling with a wingtip
during take-off from Paradise Island a few years back. It happens much more
often at Chalks than at other South Florida operators because of the water
environment. That's just the way it is. Grumman seaplanes are tough, but
there has been additional stress applied to Chalk's spars. I suspect that
the NTSB rep's opinion may be correct. Additionally, there are areas of the
spar that are difficult to inspect visually. Even with a proper inspection
revealing no cracks, work hardening of the metal may have been reaching
catastrophic limits. How does one inspect metal spars for work hardening if
there are no cracks? How long does it take for a crack to propagate to
catastrophic lengths?

The recent ADs for the T-34 and T-6 fleets, and the Aero-Commander 500 fleet
before that (the spar cracks AD, not the dissimilar metal corrosion AD),
should have instigated more research into aging aircraft and work hardening
of the spars. Perhaps this tragedy will be the catalyst.

D.