More On Airplane Windshields

I probably went for two or three years without installing airplane windshields, then suddenly I completed four installations in a two-month period. I noticed a few changes with the King Air windshields; first was pricing. The price of overhauled OEM windshields and the kits to install them has fluctuated wildly.

Five years ago, I wrote an article on windshields for this magazine (“Windshields 101” in the 2010 March/April issue) and they were going for close to $19K per side from Beech. Now, Beech’s price on the overhauled windshields has gone down substantially, but their pricing on the install kit has sky-rocketed beyond belief! What used to be a $550 item is now well over $2,000 for eight rubber seals and 56 screws! Fortunately, there is a PMA kit that is more reasonable, and in my experience, the holes line up better than the factory kit.

What is an
Acceptable Core?

The biggest new wrinkle in the world of airplane windshields is with core acceptability. An overhauled windshield uses the frame structure from an old windshield with new glass. But now, if the serial number on the windshield you are replacing begins with 95 or below (94, 93, etc.) then your core will not be accepted and you will have to pay the core charge on top of the exchange price.

Windshields with serial numbers that start with 96 or higher are acceptable cores. They can be returned to the vendor to avoid the core charge. I had an unacceptable core a month ago with one of the windshields I installed because the serial number began with 94, so we had to pay the core value.

OEM versus PMA

PPG makes the OEM windshields used in King Airs. As far as I know, the only PMA windshield is by GKN. I have installed both with good results over many years. I do know of a King Air owner that recently had a GKN installed and he is very unhappy with the clarity; an unfortunate problem, but one I never encountered before. On the other hand, I once tried to install a PPG windshield that simply did not fit. After a flurry of emails full of detailed measurements
and photographs, PPG made everything right.

Windshield Replacement

If you are monitoring a delamination situation that is gradually getting worse, and you decide to shop around for bids on windshield replacement, check your serial number first so you will know whether you have a viable core. Then, ask about PMA versus OEM, get specific pricing on the installation kit and the labor involved. Remember to factor in shipping costs – the airplane windshields weigh about 85 pounds in the crate.

Be sure to allow plenty of time, as well. This is not a job to be rushed. I estimate between 12 and 18 man-hours to change one windshield for an experienced technician. That does not include the time required for the sealant to cure, which is 48 hours at 70 degrees. In colder temperatures, the cure time for the sealant increases dramatically. I’ve had King Airs in my hangar for days and days with heat lamps on the new windshield, waiting for the sealant to fully cure.

Windshield Failure at Altitude

When a King Air airplane windshield fails at altitude, it really gets your attention. If the outer pane fails, it usually cracks, making a loud snap. If the inner pane fails, it often fractures completely with a very loud pop as little chunks of glass fall into your lap. I mentioned this in my earlier article, but it bears repeating.

Your POH tells you exactly what to do if a windshield fails at altitude, but many pilots have become completely unnerved, declared an emergency, and put their King Air down on the nearest strip, far from a decent repair facility.

Years ago, a C90 en route to California had a windshield shatter at altitude over southern Nevada. The pilot declared an emergency, landed at Creech AFB, left the aircraft there and took the airlines home. The aircraft owner dithered about for the next 10 days trying to decide what to do and how to get a ferry permit from the FAA to move his airplane, etc. The military was not amused and threatened to chop up the aircraft if he didn’t get it out of there. He finally got it ferried to my shop and we took good care of him; but had the pilot consulted his POH, he could have made the necessary adjustments and continued on to his final destination. That would have avoided a great deal of aggravation.

So, check out your POH under “Limitations” and you will find instructions to adjust the cabin pressurization differential to between 2.0 and 4.5 PSID, and to descend to FL250 or below. You will also learn how long you may continue flying in non-icing conditions before replacing the windshield – you may be surprised at what you learn.

Windshield Heat
and Longevity

Use your windshield heat properly to ensure long-lived windshields. Pilots who run “strictly by the book,” use windshield heat all the time. But many King Air pilots dispense with windshield heat in hot weather because they don’t like the distortion created by the heating grid.

As you well know, it’s quite possible to start a trip in hot weather and encounter icing conditions at altitude. If you embark on a trip with the windshield heat in the “off” position (either by choice or by mistake) and you decide to turn it on later to combat the threat of icing, you run the risk of thermal shock to the windshield.

Thermal shock can cause delamination, it can exacerbate existing delamination, and it can cause full-on windshield failure. Of course, safety is always your priority, but should you find yourself in this predicament, consider whether or not it would be safe
to continue flying without windshield heat. Again, safety is uppermost at all times. I cannot stress that emphatically enough. But thermal shock is a good thing to avoid where possible.

Delamination

Delamination does not necessarily condemn a windshield. It is noted at inspections and monitored to see if it spreads to a wider area. Windshield delamination is acceptable as long as it does not interfere with the line of sight. I have seen windshields with delaminated areas that have remained within acceptable limits for many hundreds of hours.

In the photograph (on page 12), there is an example of delamination near the frame. This delamination was not what condemned the windshield; rather, the cracks running through and around the delaminated area were the culprits. The delaminated area was present before the cracks developed, and the windshield was acceptable until the cracks appeared. Also in the photos, you will see a fully fractured windshield – this is what happens when the inner pane decides to go.

Windshield Failure –
A Non-Event

In general, the windshields in a King Air are extremely durable and designed to last thousands of hours. Since they don’t fail very often in the career of the average owner/operator, it can be very startling when it happens. But, as expert King Air pilot Tom Clements says, “A windshield failure in flight is a non-event in a King Air.” The procedure to follow is right there in your POH. You might have to move from the left seat to the right and fly from there in order to see better; but other than that you should be good to go.

Fly safely, as always.