When your airplane’s in annual, you probably monitor the caller ID with dread, living in fear of a call from your A&P that portends something expensive. If your airplane has de-ice boots—approved for known icing or not—they could easily be this year’s money hole. A full-up replacement set can cost, installed, anywhere from $11,000 for a single to $20,000 for twins.
We’ll talk about expected boot life in just a moment, and there are ways to extend it. However, what we did learn from our investigation was that when it’s time to replace one or all of the boots on your airplane, procrastinating is likely to increase the cost. When boots have significant air leaks, it not only means the vacuum pump works harder to inflate them, but the entire system is working constantly to keep them sucked flat against the airframe. That means that moisture is getting sucked into the system.The result is that the valves, hoses, relays and other components, which ordinarily last longer than the boots themselves, are more likely to suffer from early retirement.
In our conversation with Steve Mayer of BE Aerospace, maker of the Ice Shield line of boots, he described a situation he sees too commonly: The owner flies his airplane about 100 hours a year, getting into ice two or three times and uses the boots to handle it. He puts off replacement and either runs into a serious problem in ice when one wing boot works, but the other doesn’t because a corroded valve has failed, or he’s shocked by the cost when he does replace a boot because so much of the underlying system has to be repaired.
Rubber de-icing boots have been in use since 1932 when Goodrich (now UTC Aerospace Systems, but we’ll use the Goodrich name because it’s familiar and the change was so recent) developed them for the Northrop Alpha airliner. Boots have become increasingly sophisticated and now consist of a number of layers of neoprene rubber and polymers that have been impregnated with ingredients designed to protect against the effects of ozone and UV light, the bane of rubber products.
The life of de-icer boots is affected by frequency of use, how much and how high the airplane to which they are attached flies, exposure to sunlight and the radius of the wing leading edge. Over time, the anti-aging chemicals migrate out of the rubber. Everyone we spoke with recommended using Agemaster #1 semi-annually to replenish the anti-UV and ozone ingredients and extend the life of the boots.
After 40 years in the business, Bob Hayes, QA Manager at Yingling Aviation, Wichita, Kansas, expects the shortest boot life to be on commuter airliners. In his experience, boots in that environment—never hangared, flying in the flight levels and being activated often—will last three to four years.
Ken Fisher, manager of the Good-rich Service Center in Akron, Ohio, a facility that does nothing but install and repair de-icing boots, said that boots on airplanes that are hangared so they are kept out of sunlight when not operating, washed regularly with warm, soapy water and are maintained with Age Master will last as long as 20 years. He also said that aircraft with larger radius leading edges do not stress the boots in operation as much as those with tighter radius leading edges, so the boots will last a little longer.
There are two manufacturers of de-icing boots, Goodrich,and B/E Aerospace (formerly SMR). Each publishes repair manuals for its various models which, along with reference to the maintenance manual for the specific type of airplane, provide maintenance instructions and set limits as to whether damage or wear can be repaired or the boot must be replaced.
In general, damage or wear that does not leak air does not need to be repaired, pinholes and tears can be repaired, but replacement is mandated once there are cuts, tears or ruptures of an inflatable tube or that exceed a given size, there is excessive air leakage, pinholes at the leading edge of the boot or there is debonding or bulging.
Once the time comes for replacement of a deicer boot, our recommendation is to have it done at a shop that either specializes in the process or does it regularly. This is not the time to trust your airplane to someone who says that he’s always wanted to replace a set of boots. Not only can much go wrong, it can get expensive paying for someone’s learning curve.For example, Kevin Mead, proprietor of Mead Aircraft Services, which specializes in the Piper PA46 series, has seen installation errors that ranged from lumpy or crooked boots to one coming off in flight.
Experience matters—it takes Mead 11 hours to replace one wing boot on a Malibu while some shops take 20.
What’s involved in replacing boots? Step one is simply to cycle the boots and make sure they work—all of the system components are functioning properly. A routine boot replacement does not include any work on the internal system components and is priced accordingly.
Once the integrity of the inflation/deflation system is confirmed, the boot work can start by protecting the paint on the wing and fuselage around the boot, which means carefully masking the area. Then the technician notes the location of each stall strip, as they will have to be replaced once the new boot is on. Next, the fun part—tearing off the old boot. That usually starts with a razor blade cut along the leading edge, being careful not to nick the metal of the wing itself, and then physically ripping the boot off.
Once the boot is off, care must be taken to then clean the area completely to remove all traces of old boot and adhesive. This is the first area where inexperienced installers get it wrong. Every shop we spoke to emphasized the need to clean down to shiny, bare aluminum (or paint, if such is the case). The newly installed boot will show every bump, so getting the wing clean is a matter of assuring a good bond—any failure to do so is cosmetically obvious.
If any corrosion is found, it must be treated before the new boot is installed. All dents must be filled or fixed as well. So long as corrosion is within tolerance for treatment and dents are minor, no bird strikes, we found that this work was generally included in the quoted price of replacement, although some shops added the cost of this labor to the final bill.
The first step in the installation is to use a chalk line to mark the precise leading edge of the wing, as it is the basis for aligning the boot. The remainder of the installation procedure depends upon whether you have selected a “conventional” boot or Goodrich’s FASTboot. A FASTboot has the adhesive already applied to the boot, requiring only that the protective paper be peeled off before putting the boot on the wing. Once clean, the wing needs only to have a primer applied before FASTboot installation. A conventional boot, either B/E Aerospace or Goodrich, requires a process of application and activation of a liquid adhesive.
Two coats of 1300L adhesive are applied to the wing and the boot, with a half hour drying time allowed after each coat. The adhesive is then activated with toluene. This is another spot where experience matters. We heard of problems that arose from technicians who thinned the adhesive too much or got it too “wet” in the activation phase, so that the boot did not adhere well.
The boot is then pressed onto the wing, boot centerline to wing centerline, and a metal roller is used to assure there is a good bond with no wrinkles or air bubbles. This step is the same for both a conventional or FASTboot.
Once the boot is on the wing to the satisfaction of the technician, a conductive cement is applied around the edges of the boot. This allows the electrical charges that build up in flight to equalize between the boot and airframe, otherwise there will be static discharges, resulting in pinholes in the boot. Conductive cement loses its conductivity over time and may need to be reapplied if pinholes start to appear in a boot.
Kevin Mead advised us that he has observed corrosion under the conductive cement on Malibus, so he now uses Brushable Black from Sterling Lacquer, a conductive polyurethane that seals out moisture.
Once the conductive cement has been applied, the stall strips are reinstalled and the airplane is ready to go. There is a cure time before the boots can be fired—for FASTboots it is one hour; for conventional boots the time we were told varied from 24 to 48 hours.
For a high-performance piston single, prices for replacement of a set of boots is in a range from $11,000 to $16,000; for light twins, the range is $12,000 to $20,000. Prices for the boots themselves were quite close between Goodrich and BE Aerospace. Goodrich makes boots for all types of de-iced GA aircraft; BE Aerospace does so for about 85% of the fleet.
We found that shopping around can make a difference because the labor time and price varied between installers, different shops could get different discounts on the boots and B/E Aerospace and Goodrich seem always to be offering some sort of deal. These factors accounted for the wide range of prices we quoted at the beginning of the article. Further, installed, FASTboot and conventional boots were competitive in price.
B/E Aerospace has a line of distributors and installers and has dedicated personnel who train personnel at its approved installers.
Goodrich provides its boots through a single distributor, Aviall and does not approve installation facilities except for its own Goodrich Service Center on Akron-Canton Airport. It has been in business some 60 years and offers same-day boot replacement for most aircraft. Its prices were within the ranges quoted by other installers.
It also offers some incentives: Any airplane that has a boot replacement at its facility gets free labor on all boot work—including further replacements—for the life of the aircraft, and until the end of the year, a boot replacement includes a free fuel top off.
B/E Aerospace guarantees 48-hour delivery of boots from the time the order is received, with shipping included in the boot price.
Goodrich does not give a delivery time guarantee but stated that if the boots are in stock at the distributor, they can go out overnight. If they are not in stock, delivery time is generally 30-60 days. The Goodrich Service Center states that it is generally able to schedule airplanes in for replacement within a week or two.
The Goodrich Service Center has the equipment and does boot work on airplanes dating from the 1930s, however, it is not equipped to replace the internal components of de-ice systems or repair major corrosion or airframe dents.
Our inquiries led to an even split between preference for Goodrich and B/E Ice Shield boots. Bob Hayes said he prefers Goodrich, but admitted it was because he’d been installing them for so long that it was purely a personal preference, that he’d installed a lot of Ice Shield boots and thought they were every bit as good.
We did hear some complaints about delays in obtaining Goodrich boots, which may be why B/E makes a point of advertising and promising 48-hour delivery of Ice Shield boots to your installer. We received no indication that either company had the edge on quality—both were well liked.
As to FASTboots versus conventional—the operators who needed a fast turnaround and the ability to use the boots right away, notably commuters, corporate and air taxi operators like FASTboots.
Some shops told us they prefer conventional boots because the adhesive arrangement on the FASTboot means that once it’s on the wing, it tends to be on for good and it’s difficult to fix a misalignment. The wet nature of the adhesive on a conventional boot means there is some play so it can be “finessed” during installation, as Bob Hayes put it, if the initial contact isn’t spot on.
That being the case, unless you are in a hurry to use the boots right out of the shop, it appears to us that conventional boots allow a little more margin for error during installation.
No matter what, we strongly recommend going with a B/E-approved installer or an FBO who has installed a lot of boots.
Finally, we think that a shop should provide a firm quote and stick to it so long as needed corrosion and dent treatment is reasonable. We liked the policy of Goodrich’s service facility: Its manager, Ken Fisher said, “What we quote—that’s what you pay.”