May 2012
Are the side windows of your Piper airplane getting hard to see through?
Have you polished and rubbed with this and that cleaner to little or no avail?
If you’ve been blessed with a little common sense, have developed a semi-organized mind and can follow some step-by-step instructions, you’re a prime candidate to install a whole new set of side windows. It will take less than a day.
Changing pre-made side windows is one task that owners are free to do—and sign off, without supervision by a certificated airplane mechanic—under the preventive maintenance provision listed in Appendix A of FAR Part 43.
A STRAIGHTFORWARD TASK
Even if you don’t possess all the qualities listed above and only feel competent handling a screwdriver, there’s still a good chance that your “windowectomy” will turn out fine, especially if you ask your local A&P technician to provide a little coaching and oversight. Why? Because removing and replacing Piper (single engine) side windows is a straightforward task. In addition, there is plenty of information available online for the neophyte.
“Put it in; check the fit; mask off the window 1/16 of an inch from the edge of the metal; then mask the metal off 1/16 of an inch from the edge of the window; goop it up and stuff it in,” is what John Zofko, partner in Great Lakes Aero Plastics, says about installing side windows.
Great Lakes Aero Plastics is one of the suppliers of sets of side windows and is also a Piper Flyer Association supporter. The others are Cee Bailey’s and LP Aero Plastics. Each company’s website includes helpful tips and hints on working with acrylic plastic windows.
ACRYLIC THICKNESS AND LIGHT TRANSMISSION
Piper side windows are very little more than sheets of semi-formed acrylic plastic. Depending on the Piper model you’re working on, the original thickness of the outer side windows is 0.080 thick, or 1/8 (0.125), 3/16 (0.187) or 1/4 (0.250) of an inch thick. Some Piper singles came from the factory with an even thinner inner window.
An optical and transmission characteristics bulletin by Altuglas International of Philadelphia cites visible light transmission numbers for clear acrylic windows at 92 percent for clear windows, and around 77 to 78 percent for tinted windows. However, the percent of solar energy (heat) allowed to pass through the windows is highest—85 percent—for the clear windows. It’s between 75 and 78 percent for green and gray tints, and only 52 percent for solar blocking windows that were first introduced four years ago. (More about these solar blocking windows later.)
REMOVING THE OLD WINDOWS
This is the easy part. Remove the inner window (if there is one) by backing out the screws in the retainer moldings. Here’s the exact wording from the Piper Lance service manual:
1. Remove the retainer molding from around the window by removing attachment screws.
2. At the forward end of both the right and left window that is adjacent to the second row of seats, the window retainer* is riveted in place and need not be removed.
(*NOTE: This riveted retainer forms a slot to slide one edge of the window into during installation. It is in a different location on each airplane. On my Comanche, the top of the aft windows and the pilot’s side window slides into the riveted retainer.)
3. Remove the window from the frame.
After all the retainers are removed, push the window into the cabin from the outside, starting at the edge that’s farthest from the riveted retainer referred to in step 2.
4. Remove excess tape and sealer from the window frame.
I made a J-shaped hook out of a piece of aluminum to pull out the thick black sealant. Don’t skimp on this step—the old sealant must be removed or it may prevent the new window from laying flat against the inside surface of the window frame skin when installed.
INSTALLING THE NEW WINDOWS
How about installation? Piper’s installation instructions contain a few more words, but not many.
1. Cut or grind the new window to the same dimension as the window removed.
This step is rarely required when installing side windows, but if it is, there is information for grinding/cutting technique on the supplier’s website.
2. Apply a strip of vinyl foam tape (1/8 x 1 inch wide, type 1 PVC. per PMS-K0003) completely around the edge of the window.
3. Apply white (PRC) PR307 sealing compound completely around the outer surface of the window at all attachment flanges.
The materials in step 2 and step 3 are from the Piper Cherokee Six/Piper Lance manual; the window changing procedure in the Piper Arrow IV manual lists different adhesive and sealing materials. The most important phrase in the Arrow IV directions is “or equivalent”—suppliers stock a variety of cushioning and sealing supplies.
4. Install the window in the frame and install retainer molding; secure with screws.
I went overboard when I replaced the windows in my Comanche and ordered new screws and washers. I’d suggest you do the same. The new ones are shiny and look a lot better than the old hardware which was starting to rust and was a mishmash of different styles.
THICKER IS QUIETER…
One suggestion from everyone I spoke with was to put in thicker—usually ¼ inch—side windows. Thicker windows flex less than the original windows and also result in a quieter cabin.
Installation of the ¼ inch thick windows eliminates the original equipment inner window. The riveted retainer does not need to be modified if there’s sufficient clearance built in for the installation of the thicker windows. If the screw holes don’t line up after the installation of the thicker windows, new holes will have to be drilled.
In most cases new screw holes do not have to be drilled in the retainer moldings since the difference between the thinner original window and the thicker new window is not so great that the existing screw holes won’t line up as the foam tape is compressed.
…but is It a Major Alteration?
There’s no question that side windows that are identical replacement for the original windows can be replaced under the preventive maintenance rule, but I wondered whether the installation of thicker side windows constitutes a major alteration and therefore requires either a supplemental type certificate (STC) or a field approval.
The following is the FAA’s definition of a major alteration from FAR Part 1:
Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications—
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.
My opinion, based on the FAA’s definition, is that installation of thicker windows does not appreciably affect any of the factors listed in item 1; therefore, it’s not a major alteration. Hence all that’s required would be the installation followed by a logbook entry.
However, not all certified A&P mechanics or FAA maintenance examiners share my view on this subject. If you elect to install thicker windows, talk it over with the mechanic who does your annual inspections before buying your set of windows.
If your mechanic says the installation of thicker windows is a major alteration, check with the company you’ll be purchasing windows from to ensure that it hold the STCs needed to install thicker windows. I spoke with LP Aero and was told that the company supplies STCs with its windows.
COOLER CABINS THROUGH BETTER WINDOWS
Four years ago, LP Aero began selling side windows and windshields that are much more efficient at blocking ultraviolet (UV) rays and infrared (IR) radiation than original equipment. These products are called UV-SG (solar gray) and UV-GT (green tint).
According to George Mesiarik at LP Aero, these windows block 100 percent of UVA, 99 percent of UVB and are 30 percent more effective than previous windows at reducing near infrared radiation (heat). UV and IR radiation blocking is significant because even though older windows are pretty effective at blocking radiation at sea level, the blocking effect decreases by approximately 5 percent for each 1,000 feet above sea level.
The UV-SG and UV-GT windows not only reduce the effects of UV and IR on skin and eyes, they reduce temperatures inside the cabin by up to 30 degrees. Mesiarik said the UV windows also end sun-related degradation of nonorganic materials used in interiors and avionics, and that lower cabin temperatures reduce wear and tear on air-conditioning systems.
The UV window systems are about 30 percent more expensive than standard tinted windows, but Mesiarik said customers are starting to grasp that these windows may cost a bit more up front, but they can pay for themselves in the long run with increased comfort and reduced maintenance costs.
Great Lakes Aero also sells windows with the same UV and IR blocking advantages. It markets its blocking windshields and windows under the Solar Control (SC) name, and offers SC products in gray tint.
Looking out at the world—and scanning for traffic—through new side windows is such a quantum improvement over the previous look-out experience that pilots are stunned by the difference.
If it’s time to remove the “cataracts” from your airplane’s side windows, do it now. You’ll be amazed at how easy it is—and at the difference it makes.
Steve Ells has been an A&P/IA for 38 years and is a commercial pilot with Instrument and Multi-Engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as Associate Editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to editor@www.piperflyer.com.
RESOURCES
LP Aero Plastics, Inc.
LPAero.com
Great Lakes Aero Products, Inc.
– Piper Flyer Supporter
glapinc.com
Cee Bailey’s Aircraft Plastics, Inc.
ceebaileys.com
