Keeping Your Cockpit Cool:
An Interview with Ron Kensey, President of Kennon Aircraft Covers
There has long been a raging debate about which is the best way to protect the windows and interior of an unhangared aircraft: exterior aircraft covers or internal sun shields. We decided to ask a real expert — Ron Kensey of Kennon Aircraft Covers in Sheridan, Wyoming — whose company makes both.
Ron, I notice Kennon makes exterior aircraft covers as well as sun shields that install inside the aircraft. Which keeps the cockpit cooler?
Our sun shields actually keep the cockpit cooler. Both exterior covers and sun shields keep the temperatures inside the cockpit at acceptable levels, that being below 135º Fahrenheit. As long as you use one or the other, you will achieve that objective.
What makes 135ºF the magic number?
Most manufacturers advise not to power up avionics in temperatures greater than 135ºF so we use that as reference point.
What difference does it make which you use — exterior covers or sun shields — if both achieve the temperature objective?
Exterior covers help solve other problems that sun shields don't, such as preventing cabin leaks, keeping ice, snow and frost of the windshield, and protecting the windows from blowing sand and atmospheric chemical fallout.
So why not always use exterior covers?
It's a harsh environment outside the airplane. When we first introduced our sun shields, our customers told us of the experiences they had with exterior covers blowing in the wind and scratching their windows or trapping moisture that later clouded the Plexiglas.
Later on, when we started making exterior covers, we had to take all of that into account to build the safest cover on the market. But still, mother nature is stronger than any plane and certainly any cover. I have seen the very best covers ripped off airplanes, and it's not a pretty picture.
Well then, you are saying sun shields are safer to use?
Yes, in most cases...and I will discuss the exceptions later. There simply are more things that can go wrong outside. I know that just from all the time and effort we expend building safety into our exterior covers.
Let me give you an example. A foreign company sold 100 exterior covers to the U.S. Marines during Desert Storm. Those covers did $1.5 million damage to the transparency systems because they had fuzzy liners that felt soft to the touch but collected sand that later scratched the acrylic.
So instead of using a fuzzy liner on our canopy covers, we use soft slippery satin. Satin that is so slippery that nothing will stick to it. Our research shows it's the safest material to use as a liner for exterior window covers. Of course, slippery satin is difficult to work with when you are sewing it, so it takes us extra time. But we think the extra time is worth it in terms of the extra safety that it provides.
Do you guarantee that your exterior cover won't damage the aircraft?
Our guarantee has always been that the customer must be satisfied or we give them their money back, and we never put a time limit on it. But no cover manufacturer can ever be certain that their exterior cover will not damage an aircraft under any circumstances, no matter how hard they try to make a safe cover.
Back to sun shields for a minute. Don't sun shields reflect the heat back to the window? Can this damage the Plexiglas?
That's a question we are asked almost every day. The answer is that the heat-producing infrared rays of the sun behave exactly like light rays: they pass right through transparent materials like acrylic aircraft windows. Only when the infrared rays are absorbed — by opaque materials — do they produce heat.
Kennon Sun Shields reflect 93% of the infrared rays back though the windows before they are absorbed and produce heat. The aluminum surface of our sun shields is a terrific reflector. Only 7% of the rays are absorbed by the shield.
On the other hand, without the shield the sun's rays penetrate the window, are absorbed by the aircraft interior, and heat is produced. It is produced inside the cockpit which acts like a greenhouse and the heat cannot escape.
An acrylic aircraft windshield is shaped with heat. It begins as a flat sheet, and when it gets hot again it wants to return to its original flat shape — it has a "memory." That is why you first begin noticing crazing on the curved areas of the windshield. Extreme temperature fluctuations inside an unprotected aircraft cause that windshield to change its shape back and forth.
For example, during Desert Storm, the cockpit temperatures inside the closed unprotected aircraft exceeded 200ºF. Hot enough to change the shape of the canopy to the extent that canopies once opened could not be closed and latched. They were actually warping in the heat.
So what did they do?
At that time there wasn't much they could do. The aircraft were put out of service. We were told that the allied air forces flying the Tornado, an aircraft with a hinged side-opening canopy, had to actually file the closing latch on the canopy in order to get the canopy to close. That makes me wonder what happened when the canopy cooled in flight and returned to a more normal shape. Would that filed latch hold?
Doesn't sound like a very permanent solution.
It probably wasn't. The USAF charged Wright-Patterson Labs to come up with a solution to the cockpit heat build-up problem that they were having with the F-15s. An alert aerospace engineer noticed a set of our sun shields on a Bonanza at the local airport and called us. We designed both an exterior cover and an internal sun shield for that aircraft for the engineers at Wright-Pat to test.
We actually recommended that they use the exterior cover in the desert because of the blowing sand and chemical warfare. But ultimately they decided on sun shields, because the environment inside the aircraft was more predictable, and based on their painful past experience with exterior covers. Economy also had a lot to do with it: the sun shields cost a fraction of what exterior covers would have.
The engineers tested the shields, ran extensive computer models on the effect of the shields on the temperature of the canopy, and were satisfied that the shields were safe to use. Since then Kennon has designed shields for practically every military aircraft flown by the all services of the U.S. Department of Defense.
So when would you recommend an exterior cover over sun shields?
In a number of situations: when you have a leak and you can't fix it; if you do a lot of winter flying and want to keep snow and ice off the windows; if you are parked close to salt water or at an airport are with a lot of airborne pollution. And if you are covering the rest of your plane to protect the paint from fading, then an external canopy cover is the best solution.
Also, any windshield that has metal components laminated between layers of acrylic — such as the heated windshields on known-ice-equipped airplanes — should be covered with an exterior cover in my opinion.
Are you saying that sun shields will damage those heated windows?
No, but the sun will. Sunlight is particularly damaging to these windows because the embedded metal gets hot and expands at a different rate than the acrylic window itself. Interior sun shields can't prevent this because they do not block the sun before it reaches the window.
We've been working with a major aircraft manufacturer who is seeing bubbling and delamination of these heated windshields on unhangared aircraft. They believe the black glareshield is getting so hot that it is also heating up the metal in the windshield, causing the windshield to delaminate. But I think the main culprit is the heat produced when direct sunlight is absorbed by the metal.
Covering the windshield or keeping the plane hangared is the only way to prevent this problem. I think manufacturers who use such windshields will start insisting that they be covered as a warranty requirement. Some of those windshields cost upwards of $60,000 to replace, so why take a chance?
Obviously safety of the aircraft is a concern to you. Is it product liability that drives that concern?
Partially, but you can insure for product liability — and Kennon does. The fact that we are strictly an aircraft coverings company has a lot to do with it. We don't build boat tops, tents or awnings, so we can devote our complete attention to the development of the best aircraft covers. Therefore our customers depend on us.
Also, we readily admit our mistakes — and learn from them. Our first reflective sun shield product did not have the protective coating that we use now to prevent scratching to the soft Plexiglas windows. Aviation Consumer wrote a glowing review article on that product, but shortly afterward they issued a service alert warning customers that Kennon Sun Shields could cause scratching...and they were right. The uncoated shield left the aluminum exposed, and if that aluminum oxidized, it could create a scratchy abrasive film.
Fortunately, we figured out how to coat our shields with a clear film that prevented oxidization and scratching. We called or wrote each of our 4,500 customers and told them of the potential problem. We offered them three options: a free windshield replacement sun shield with the new clear coating, a complete new set of coated sun shields for half-price, or their money back. It has always been our policy to offer an unconditional money back guarantee.
Our customers were surprised to hear from us, and I think they respected the fact that we contacted them. Almost all of them were delighted with the way the shields kept the cockpit cool, and the majority took advantage of the half-price upgrade, while many felt that they didn't have a problem and would continue to use what they had.
Since that experience seven years ago, we know how important is to ask the safety questions first and build safety into every one of our products.
Ron, I've noticed that there are other firms that sell products that look just like yours. Are they the same? How do you feel about these competitors?
We have always been fortunate to lead the industry in the development of new products — first the sun shields, then spoiler wing covers, a better insulated engine cover, our satin-lined canopy covers, and now our newest product, the Kennon Dust Cover (which is really a hit, by the way). We do have plenty of imitators, but they say imitation is the highest form of flattery!
Walt Disney is my hero, and he once answered a question like yours by saying that his shop had ideas for new improvements and new products that they didn't even have the time to implement yet. If others copy your product, then at least you don't have to worry about them beating you to the punch with something new. Disney was a forward thinker, and I'd like to think that applies to all of us at Kennon, too.
But what do you say to the competitor who "borrows" your product ideas?
I believe that competition makes us all build better products. So I would say to the competition: don't just take the idea and copy it...make it better! R&D is hard work, it's expensive, and there are risks involved.
And if you copy something, at least copy the state of the art. Here's an example to the contrary. It has been seven years since the service alert in Aviation Consumer about the potential for uncoated sun shields to scratch acrylic windows. Yet there are still companies in the aviation business that sell sun shields or sun shield material without any protective coating!
Right now, I'm looking at the latest catalog from the world's largest aviation mail-order firm. In the ad for their "do-it-yourself sun screen kit" it states that the material might scratch the windows, and suggests that Velcro be used to keep the material away from the windows. But you can't use Velcro in many cases. In fact, what put Kennon Sun Shields "on the map" in the first place was the fact that they wedge into the window molding and fit without the need for Velcro or other fasteners fasteners. So why does this big catalog firm say this and offer the uncoated material? Certainly not to offer value to their customers.
Now, the average aircraft owner sees the material in the catalog and since it looks exactly like Kennon Sun Shield, he thinks it is. He buys it, uses it, and maybe it scratches his windows. Now he's turned off to the sun shield concept forever — even our product! And he probably tells his friends.
This is the sort of "competition" that makes me mad.
What do your customers think?
I know that a lot of our customers are in business for themselves and can appreciate value. I often say that there are a lot more stamp collectors than aircraft owners. Aircraft owners are a special breed. And our customers are a very special subset of the total group of aircraft owners: they protect their property and the property of others. We feel quite lucky to work with people like them every day.