Not bad Mary, here is a little more about aircraft windshields and the
requirements for replacing them, and the maintenance effort. Ok, they
are laminated, and each manufacturer puts out specs on how much damage
(layers) and where the damage can occur. If the damage is in the
windshield heat section, or is in a certain structurally unsafe
section, or obscures the pilots scan (safety of flight issues) it's
outta there. It is a relatively easy replacement, the only real issues
are the hundreds of screws, the lengths, making sure you get the right
ones back in the right spot, and the sealant. If it is cold weather
obviously it's gonna take longer for it to seal. It takes additional
time to find hangar space, move assetts, do a respot if it is cold out
and you need 55 deg for a good cure, otherwise you can do it out on
the line. Then you gotta do a pressure check to check for leaks which
requires pressurization of the whole aircraft (neg) on the deck. It's
a requirement for the Navy, not sure about the civvies. I've heard
knuckleheads say, "why do a pressure check? we''ll know if it leaks
when we get to altitude." Usually we take an aircraft off the schedule
for at least 12 hours, (6-12 hours given for cure time, about 2-4
hours for maintenance and the pressure check). Anything less is a
calculable risk made with all professional entities, (ops and
maintenance) dictated by a flight schedule driven by a profit, or
mission accomplishment. Next time you see an aircraft delayed for only
8 hours for a windshield replacement, the only thing that could make
it that fast would be a sealant that has about a less than 2-4 hour
cure time. Wish we could get our hands on some with a milspec.

On Mon, 19 Jan 2004 14:59:45 -0800, Mary Shafer
wrote:

On Mon, 19 Jan 2004 15:35:56 -0500, Howard Berkowitz
wrote:


Mary, are there any provisions to protect the pilot on the damaged from
at least the annoyance of wind? If nothing else, it's going to be COLD.

Usually the windows don't break. They just crack, admitting pureed
bird*, if present. (Eeeuuugh!) In such cases, cockpit heat is good
enough to keep the crew warm.

I think, but don't know and haven't looked, that the rules require
landing soon if the windshield is actually broken out, whereas the
rules allow the flight to continue if it's only cracked. In the only
case I have first-hand knowledge of, they hit the goose and cracked
the windshield while climbing out from San Francisco and continued to
London Heathrow.

*The usual cause of windshield cracking in flight, although
temperature stress can cause it, as can mechanical stress. The X-15
had one of each of the latter two, for example. Like airliners,
research aircraft rarely have any sort of battle damage, so I don't
have any bullet strike accounts to relay for Dryden aircraft.

ObMilitaryAircraft: The convertible F-18 that Bill Dana flew was the
result of a canopy latch problem, not a bird strike or battle damage.
I know a guy who lost a T-38 canopy in flight, again from a mechanical
problem. In both cases, it was pretty bad, cold and windy and too
noisy to hear anyone on the radios. The checklist says something like
crank your seat all the way down, tighten your chin strap and O2 mask,
announce the situation on the relevant frequencies, and land or trap.

In the case of a bird strike on a high-performance airplane with
canopy, the problem is that the canopy usually doesn't hang around
long enough to ward off the subsequent birds, and they smack into the
front-seat pilot's head and face. This is one of the important
reasons why pilots are supposed to keep their clear visors down and
locked.

Mary