Safely Strapped In

Oddly enough, certification rules have hampered seatbelt development but the aftermarket provides affordable better alternatives.

Try this: Call up a close friend and ask him to put down his Millers and come out to the airport to have a look at the latest installation in your beloved Skylane. Ten to one hell ask you which GPS you bought.

Tell him youve just installed a shoulder harness. There are no odds here. Your friends going to tell you that hes in the middle of a hot cribbage game with his mother-in-law and he cant get away.

Such is the glamour of seatbelts and shoulder harnesses. In the aircraft classifieds, you’ll find proud owners still pimping Mark 12s, Cessna 300 radios and wing levelers. But seatbelts? Not a chance. As one grizzled old FAA bureaucrat told us: Flying airplanes is not about safety. Its about sex. Its about what looks good, goes fast and rides well. The industry might be able to sell safety, but it has to be hidden in a sexy package.

Belts and Harnesses
Amazing as it may seem, there are still airplanes in the fleet with nothing but lap straps. And to be brutally honest, even those with single shoulder harnesses arent much of an improvement.

The lack of overall belt effectiveness is aggravated by misuse of the belts. The aeromedical community suggests that the lap belt be placed low on your hip bones because thats the strongest skeletal area of your body. Wearing the belt high, across your stomach will likely cause internal injuries and if you wear it too low, across your thighs, the belt wont limit your bodys forward motion in a crash sequence.

The diagonal shoulder harness should not rub against your head or neck, but should be positioned so that the torsos center of gravity falls within the angle formed by the harness and lap belt. The safety belt buckle should be positioned on the side of your hip when you attach a shoulder harness, not higher up, towards your belly. (This is a common error.)

When its tightened, the belt system ought to create an angle of 45 to 55 degrees with the vertical centerline of the airplane, which allows the lap belt to resist the upward pull of the shoulder harness. If an aircraft comes to a sudden stop, even a shoulder harness wont prevent an occupant from sliding out from under the restraint system. Engineers call this submarining and new seat restraint systems attempt to solve the problem by positioning the seat to direct impact force upwards, shoving you into the belts, not out.

For most of the aircraft flying today, the only graciously uncomfortable way an occupant can prevent submarining is to wear a five-point harness. The fifth strap is a crotch strap and is standard equipment in most aerobatic airplanes.

The single diagonal harness is simple to use, looks like an automobile belt and has good utility in preventing head and neck injury during longitudinal deceleration, but its weakness is a tendency to roll the torso during side decelerations. For that reason, some owners retrofit double over-the-shoulder harnesses.

Inertia reels, similar to those used in ground vehicles, keep the belt taut and allow the pilot to move freely but restrain him from whacking the instrument panel during sudden deceleration.

Better Seats
If seatbelt design seems somewhat stagnant, it is. These days, engineers work toward improvements not just in belts but in seat systems. The current thinking is that the occupant should be restrained to the seat, the seat to the airplane and the airplane designed so that when the floor or bulkhead deforms during an impact, the seat restraint system remains intact.

Seat restraint testing is hugely expensive. Each sled run may cost $2000 to $3000. As one engineer told us, it may take 10 sled runs just to verify a single idea that ends up in the wastebasket.

The forces involved here are complex and enormous. Researchers define acceleration (or deceleration) as linear-when you take off, land or ditch. When you pull out a dive, you experience radial acceleration and when you spin an airplane, the force is called angular acceleration.

Restraint systems are designed to limit the movement of the body in response to these and other accelerative forces. Time is a factor, too, not just the raw G force. Sudden acceleration lasts for less than a second while prolonged acceleration is a force that lasts more than one second.

The latter is more difficult to resolve since the human body has the capability to withstand 20Gs for 200 milliseconds but far lesser load for longer than a second. During the 1950s, the famed Air Force researcher John Paul Stapp climbed aboard a deceleration sled and survived a force of 46.2Gs, something no one thought was possible. The sled was stopped suddenly while moving nearly at the speed of sound.

Stapp survived because he was we’ll restrained, he was sitting forward and the deceleration event lasted only .008 of a second. On the other hand, the human body falling, in a foot-to-head direction, as you might in a flat spin, can only withstand 3Gs for duration of 5 seconds.

General Aviation restraint systems deal with these forces only in limited ways. Under Part 23 rules, for example, the emergency landing dynamic conditions break down into two tests: A horizontal dynamic test focuses on the restraint system by decelerating a test bed from a velocity of 42 feet per second, peaking at 26Gs for crew seats and 21Gs for passenger seats. (Thats where the so-called 26G seat comes from.)

A vertical test is actually an incline test where the seat and occupant are pitched up to 60 degrees and dropped, placing a load on the occupants lumbar region. The seat is decelerated from at least 31 feet per second, peaking at 19Gs for the crew and 15Gs for passenger seats. The vertical lumbar load cannot exceed 1500 pounds and the individual harness strap load cant exceed 1750 pounds. The seat design is manipulated to reach that goal.

Under FAR Part 23.561, aircraft structures are certified to give each occupant every reasonable chance of escaping serious injury when the static inertia loads correspond to these load factors: 9Gs forward, 1.5Gs sideward, 3Gs up for normal or utility category airplanes when proper use is made of seats, safety belts and shoulder harnesses provided for the design.

Not What You Have
But your airplane probably has none of this, since the majority of the aircraft flying these days-including new Cessnas-were certified under CAR 3 rules or early FAR 23.

This wouldnt be of interest except that it plays a role when we ask why high-tech seat restraint systems havent evolved in airplanes as quickly as they have in automobiles. The quick answer is that airplane manufacturers are stuck with the original design certificated prior to FAR 23 or perhaps even an early version of FAR 23, which has been amended many times.

A manufacturer would essentially have to create a brand-new aircraft, under a new type certificate to change the seat restraint system significantly. Some manufacturers believe that although aircraft owners demand safety, they would never pony up the sticker price for a new design that only promised increased crash worthiness. Then there’s the liability issue. A new design under an old certificate gives cause for a plaintiff lawyer to ask, my client wants to know why he was injured by a design that you must have known to be faulty because you improved it.

Aftermarket companies offering improved wares don’t have this worry, but still, these companies tell us the FAA is slow to approve aftermarket restraint systems because the agency lacks qualified inspectors to push the paper.

DERs or designated engineering representatives are an expensive option for small manufacturing shops. DERs are in short supply anyway, even if they were qualified to judge restraint systems, which few are. If the regulatory environment is unfriendly to innovative design and current production aircraft are stuck with designs hobbled by 50-year-old certificates, where does that leave an aircraft owner who wants to enhance a safety belt and harness system in his production airplane?

Its not hopeless. In the first place, it doesnt take much technology to enhance the safety of an airplane that has no shoulder harness. Get a harness if your airplane doesnt have one. Research has shown that 88 percent of major injuries and 20 percent of fatalities can be eliminated by simply installing and properly using an aftermarket, TSOd harness. Itll cost you a couple hundred dollars per seat, minimum, but its cheap insurance per seat.

In the second place, how much safety can you buy at any price? Once you have met the problem by equipping your airplane with TSOd belts and harnesses, you use them and make your passengers use them and you maintain the harness integrity, youre flying within the safe envelope of your aircrafts certificated limitations. If you want to be safe while youre giving spin demos in a V-tail Bonanza, youve got problems we cant solve here.

None of this means that you cant, as an owner, seek out improved replacements for what youve got or STCd restraint systems that materially improve safety. That said, lets go shopping.

Whats Available
If you own a production aircraft, there’s quite a variety of new or improved TSOd lap and shoulder harness kits available. You can either buy retrofit kits from your Cessna, Beech, Mooney, Piper or other dealer, for which you’ll need no additional paperwork, but a fair chunk of money, say $200 to $1500 per seat. Or you can look for after market kits from specialty houses.

In some cases, the products will require an STC or Form 337. This means that you’ll have to get FAA approval for an installation not covered by your aircrafts certificate. A field approval can be grease or it can be a nightmare, depending on your FSDO, their familiarity with the product and their staffing.

Some after market harness kits are made specifically for a type of airplane. These are the most painless to install, since theyre TSOd and ready to go, with no need for a Form 337.

STCd Harnesses
The Wag-Aero catalog, for example, features three full pages of belt, harness and webbing options. With the Wag-Aero catalog in one hand and your checkbook in the other, you can enhance your survival in nine colors and at reasonable cost.

Lap belts cost about $40, harnesses about $50 and TSOd combos start around $90. You can buy 2-inch webbing at Wag-Aero for $3.50 per yard (minimum is five yards) or you can buy pre-approved, TSOd and ready to install kits for Cessna 120s through 207s for less than $150 per seat. (These are stock replacement items.)

Piper and Stinson prices are about the same, but an Aeronca will cost nearly $200 a seat and the Beechcrafters will have fork over a bit more than $300 to outfit a 35 series seat (A-G).

Kosala and Associates hold STCs for many earlier Piper aircraft belt and harness installs including the J-3, PA-11-24 -30-39. The kits are available for front and rear seats, with or without inertia reels.

you’ll need your aircraft serial number when you order and you can expect to pay $320 to $520 per seat for 14-different kits. Black is the standard color but Kosala will work with you on custom color options.

Hooker Custom Harness hold STCs for V- or Y- style harnesses for the Cessna 120 through the 210F for about $175 per seat. Jack Hooker, an icon in the harness industry, has developed what he calls the Hooker Quickie Shoulder Harness, which uses the rear seat belts as an anchor for the front seat shoulder harness system.

In our view, this is a fundamental improvement over no shoulder harness or even a single diagonal harness. It provides at least some resistance to submarining. Hooker believes that since most four-place airplanes are flown with two on board, the Quickie is a good solution. (The backseats might be usable, but not conveniently.)

Hookers fixed anchor harness, such as the model 300100 for most strut-braced high wing Cessnas, have been static-tested to 3600 pounds or about a 36G impact with a 180-pound person. The cost is about $175 per seat with all necessary hardware, double shoulder harness and double adjustable seat belts. Not a bad deal, in our view.

Install time for the Hooker restraint systems depends on your A&Ps experience. Most systems take about 60 to 90 minutes with headliner removed, if the A&P has previous experience. If he hasnt been there before, you’ll pay for the education and the labor will probably exceed the cost of the belt kit.

B.A.S. Inc. offers STCd inertia reel shoulder harnesses for most of the larger Cessnas. The Y-style harness is attached to the main carry through spar. The harness models for the Cessna 170 to 210F cost about $865 per seat if the airplane has a fabric headliner and $910 if its plastic.

The C-177 Cardinal costs $910; Model 190-195s cost $1030 which includes floor mounts for the lap belts to replace the original seat-mounted brackets. Black webbing is standard.

Bud Blancher at B.A.S. is another industry icon who has been in the harness business for years. Like Jack Hooker, he believes in the ability of creative people in the field to find and manufacture top-notch safety restraint systems. Its worth your time to give these guys a call before you jump into the market for new and better belts.

Chief Aircraft sells lap belts -in 20 colors-and theyre TSOd. But Chief reminds you in print that a shoulder harness installation outside your aircrafts certificate will require an STC or field approval. This could be expensive, depending on whether the shop has experience in the field.

You can buy basic lap belts for $59, add a shoulder harness for another couple of pounds and pay $114. Pay $169.95 total and you can have a state-of-the-art inertia reel system.

Chief also sells four-point release systems for $349.95 with an inertia reel and $299.95 without. Five-point release systems with inertia reels cost $369.95.

Aircraft Belts will produce custom TSOd belt and harness installations to your specs in 25 colors with a custom-dyed web option. ABI offers a complete line of fittings including inertia reels and a wide variety of buckle styles and finishes.

You can buy a gold buckle and get it engraved if you want. ABI serves many jet completion centers and theyre happy to work with individuals on custom assignments. ABI manufactures their own systems but theyll refurbish yours and even work out same day service, for a slight extra charge.

Beltmaster Corporation is another major supplier of belt systems which serves the corporate jet world and yet will work on special projects with individual owners.

Beltmaster will refurbish your webs and hardware, replace parts and re-certify a belt thats worn and frayed. They offer a wide range of colors, plus custom dye webbing to match your sample. Safety Limited supplies custom harness assemblies to your specs in 13 colors. Safety Limited can sell you new, over-the-shoulder belts for $49.95 or re-web and re-certify your harness for $31.95.

Are You Safe?
Sure. Pilots have been motoring around with loose lap belts for so long and dying of old age that its hard to make a case for a seat-restraint crisis. (That said, the FAA is busily preparing a new safety initiative encouraging both the use of shoulder harnesses and retrofitting better equipment. It will include a video and a Web site, neither of which is available yet.)

Still, we think some attention to seatbelts is warranted, to include a detailed inspection to check for serviceable webbing and aircraft fasteners, not hardware store junk.

The addition of Y-type shoulder harnesses isn’t especially expensive and will materially improve survival odds and reduce injuries in certain kinds of accidents. Better to think about that now rather than after the crash.

Also With This Article
Click here to view “Seatbelt Legalities.”
Click here to view Addresses.
Click here to view “The Cirrus Experience.”
Click here to view the Checklist.

By Richard A. Coffey

Dick Coffey is editor of Aviation Consumers sister magazine, IFR Refresher. He owns a Beech M35 Bonanza.