The unpleasantly long heat wave we’d been suffering had just broken, ushered away from the premises by a solid line of thunderstorms and then low clouds, drizzle, and fog—not exactly what we had expected. With nobody flying, I walked into the pilot’s lounge at the virtual airport to see who was occupying the big, ancient recliners as I was hoping to find Tom to discuss some recent accidents.
Tom is an interesting character—he was a student of mine when he was getting his private ticket while working at the University of Michigan’s Highway Safety Research Institute (now the University of Michigan Transportation Research Institute). He had previously been in the pits for a team that raced Formula 1 and Indianapolis 500 cars—and his driver had won Indy in 1974, so he owns a very cool gold ring. Speed and safety were a part of his life, once he picked up his ratings he flew freight in Learjets, Falcons and other high-speed equipment before being snatched up by FlightSafety International where he gravitated to the fastest civilian airplane in the world at the time, the Cessna Citation X, becoming the very first designated pilot examiner in those blowtorches.
I saw Tom as I walked through the door. As good luck would have it, he was talking with Wayne, our resident tailwheel expert. Wayne has more time in Beech 18s than most pilots have in all the airplanes they’ve ever flown.
After Tom and Wayne made appropriate insulting noises as their way of greeting, I said that I’d like their input on three accidents that had happened in the previous few months—two in airplanes, one in an SUV full of teenagers, um, young adults.
The two aircraft accidents were tailwheel utility machines operating in their natural habitat—the backcountry. In one, the strip was a designated landing area. The pilot, carrying a pilot in the right seat, made several observational passes over the airstrip at about 300 feet, while slowed to about 80 knots, to look at surface conditions. They agreed that everything looked good.
After touchdown, rolling out through tall grass on the runway, they felt the airplane hit something. They were both popped hard into their shoulder harnesses momentarily. As the rollout progressed, one wing settled until the wingtip was touching the ground, but the pilot flying was able to keep the airplane straight on the tree-lined runway. The pilots looked at each other, simultaneously asking, “What did we hit?”
They got out, walked back along their ground track, and found that there was a log hidden in the grass. One main landing gear had hit it and bounced over it. The other hit the log and broke off. They were uninjured.
The other tailwheel backcountry accident took place on top of a remote ridge. The pilot had operated out of the area before and was making his fifth landing there that day. As usual, the pilot was making a tail-low, wheel landing because the ground was rough, and he wanted to protect the tailwheel although he wanted to touch down with full flaps and as slowly as possible to minimize energy. He didn’t want to make a three-point landing because of concern for the tailwheel. I fully understand—I’ve broken a tailwheel off on a rough surface.
During rollout, just as the pilot was getting the stick aft to lower and pin the tailwheel on the ground, the airplane hit a swale or depression in the ground that was deep enough to stop the main gear from further progress and the airplane flipped over. In none of his previous operations into the area had the pilot ever seen the low area.
As the mains came to an abrupt stop, the pilot was thrown forward violently. The shoulder harness stopped him from smashing his head into the panel. It held him positioned safely as the airplane nosed over to inverted. He held onto the bottom of his seat with one hand while he released the harness with the other and lowered himself to the ceiling before getting out. He was unhurt.
The third accident involved a gaggle of young adults in an SUV doing as young adults in a group are wont to do. Not surprisingly, the driver lost control making a turn at about 40 mph and the SUV rolled over—at least twice. Sadly, and not surprisingly, few, if any, of the occupants were wearing their restraint systems. Three—not wearing restraints—were “thrown clear” through windows of the vehicle. One was killed by the force of impact with the ground, the other two died from a combination of ground impact and the SUV rolling over them.
Tom and Wayne started talking about the accidents and the sad loss of life in the SUV rollover and I started taking notes.
Wayne pointed out that every year AOPA’s McSpadden Report (formerly the Nall Report), with reams of data on general aviation accidents, invariably shows that if a pilot is going to crash, it’s most likely on takeoff or landing and is usually loss of control during rollout. Usually a crosswind is involved, the pilot comes down final too fast, touches down at the speed of heat, swerves, can’t manage the energy involved, whistles off the runway and comes to a quick stop against a hangar, another airplane, or some irregularity in the ground. With a tailwheel airplane the pilot is nearly three times more likely to wrap it up into a ball on landing (or takeoff) than in a nosewheel airplane because of the physics and aerodynamics of a design that places the center of gravity behind the main landing gear.
Making matters worse, Wayne pointed out, in a tailwheel airplane, the pilot is likely to stand on the brakes as things are going south causing the airplane to either flip over or rock onto a wingtip—depending on the direction the airplane is pointed and traveling. In such mishaps, impact is usually at something below stall speed, maybe as low as 20 mph.
Tom spoke up, explaining that the G loads involved in the quick stop mean that the occupants are going to continue to move forward until they are stopped by something inside of the airplane or the ground, a tree or building, if they get thrown out. Research by NASA, the University of Michigan and other organizations, assisted by aircraft manufacturers since World War II (Cessna and Piper donated airplanes to NASA for full-scale crash research), demonstrated that a well-restrained, healthy adult can withstand on the order of 20 Gs for something less than a second during a crash sequence. (Women do better than men—their bodies are more efficient—while G tolerance for everyone drops off with age after 40.)
An impact stopping an airplane from 20 mph in one foot generates on the order of 13 Gs on unrestrained occupants. It is physically impossible for a person to “brace” for such an impact—the arms will be shattered, and the chest and head will hit the instrument panel or the seat frame in front of the occupant—or the ground, a tree or building if the occupant is “thrown clear” of the airplane. That’s an almost certainly fatal encounter, either due to blunt trauma to the head or the aortic arch separating from the heart.
Even if the occupant survives the head impact, the odds are that it will be enough to render her or him unconscious for at least some time, delaying exit from the airplane. Post-crash fires in aircraft are rarely the explosions shown in movies—there is usually enough time for a conscious occupant to exit the airplane before a fire becomes severe. Hitting one’s head can mean the occupant can’t take advantage of the time presented to get out before a fire gets going.
While seat belts have been installed in airplanes almost since powered flight began, their original purpose was to hold the pilot in the airplane in turbulence—yes there were early fatalities involving the pilot being tossed out of the airplane in flight.
A side benefit to seat belts is that they kept the occupant inside the airplane and anchored to the seat during a crash, giving more protection than no seat belt at all.
The problem was that during an impact the occupant’s body is moving forward while the airplane is slowing down, sometimes radically. That means that the only part of the occupant’s body that is restrained is the lower torso/hips so the body jackknifes; everything else—legs, upper torso, arms and head—keeps moving forward. The technical term is that the body flails.
If there is flail space in front of the occupant’s seat, flailing without hitting anything can be survivable. Unfortunately, the reality of aircraft design means that there’s almost never much flail space—the occupant is going to hit the instrument panel, the yoke (side sticks are also good crashworthiness protection), or the back of the seat in front of the occupant. That means an often-fatal quick stop.
In World War I, seat-belted pilots were killed when their heads hit gunsights mounted on top of instrument panels in otherwise low-speed crashes. That led to the development on the shoulder harness. The benefit was immediate—fewer deaths in crashes.
The problem was that, in the civilian aircraft world, safety didn’t sell until the late 1970s—and, amazingly, was actively opposed through the 1950s, ’60s and early ’70s. For example, starting in 1946 Cessna offered shoulder harnesses for every seat in all of its singles—and not a single buyer ordered the option in the over 30 years it was offered. Cessna did make shoulder harnesses standard for the front seats and then for all seats before the FAA mandated them.
However, a lot of pilots refused to wear available shoulder harnesses and the FAA initially only required their use during takeoff and landing—something many pilots ignored—and the march of death in low-speed accidents continued.
Manufacturers began offering integrated belt and shoulder harnesses—as had been done in cars for years—making it more difficult for pilots to wear just the seat belt. From the aerobatic world more sophisticated four- and five- point harnesses started being incorporated in production normal category aircraft—greatly improving the odds for front seat occupants when things went south.
The FAA began tracking injury and fatality data in aircraft crashes and correlated it to the use of available shoulder harnesses. Its data (and all other studies to date have confirmed it) showed that use of shoulder harnesses reduced crash injuries by 88 percent and deaths by 20 percent.
That’s huge. Yeah, it qualifies as a silver bullet.
Tom went through the two bush ops accidents with us. In both cases the airplanes were at relatively low speed—on the order of 30-40 knots. In both of those cases that was fast enough that when the airplanes suffered an impact—the log or the swale—the deceleration would have put the occupants into the instrument panel. With just a seatbelt it would have been headfirst; with no restraint it would have been head and torso.
In the log incident, without the shoulder harness, jackknifing over the seatbelt and hitting his head on the panel would probably have caused loss of control of the airplane and potentially a swerve into trees, multiplying the effects of the initial impact and possibly killing the occupants. As it was, the pilot stayed in position and was able to keep the airplane going straight as it decelerated to a stop.
In the nose-over accident, the pilot would undoubtedly have jackknifed headfirst into the instrument panel when the main wheels came to a quick stop and the nose came down to impact the ground. He would probably have suffered a serious head injury, either killing him or disabling him for some time. As it was, he was unhurt and able to use his satellite tracker to make an emergency call for help. He was so deep in the bush that a helicopter didn’t get to him until the next day. Had he had a head injury it is likely that he would have bled out before help arrived—or that he could not have sent a satellite call for help at all.
In the SUV rollover the unrestrained occupants were tossed around the interior of the vehicle, subject to hitting anything that happened to be in their way or to break a window and be ejected even though the vehicle had airbags. A restraint system that holds the occupant in position is a predicate to an airbag to be able to protect them.
Being blunt, a pilot or motor vehicle occupant who dies because she or he doesn’t wear all available restraints fully qualifies for a Darwin Award.
Wayne went on to point out that over the years, a lot of the tailwheel airplanes he flew did not have shoulder harnesses, but as he’s done his homework, he’s found that almost all can have shoulder harnesses retrofitted. For many Cessnas, it’s simple: Order the parts and install them—the shoulder harness hardpoint is already there. For most others there is an aftermarket solution at reasonable prices.
If you want the very best, AmSafe (www.amsafe.com) offers airbag seatbelts that can be retrofitted to any seat in any general aviation airplane. It doesn’t get any better than that.
The chances are that your airplane has a silver bullet for crashes installed. I recommend that you wear that shoulder harness all of the time because as an old friend used to say to me, “When you least expect it, expect it.”
See you next month.
Pogo: “I have met the enemy and he is us”.
Pogo nailed it.
Flying the “unimproved” airstrip environment in utility tailwheel airplanes our motto was “restrain occupants and cargo as though you’re going to.crash, then fly the airplane as though occupants and cargo are not restrained.” Occupants were restrained with 5 point harnesses. Decades later, the first $400 I spent on my ‘46 120 was to buy some peace of mind and install a pair of Hooker Harness belts. That was the best money I spent on that airplane.
I’m the second owner of a 1959 C172. The original owner saw no need for a shoulder harness, despite being barely five feet tall and in her 80’s when I bought it. The first thing I did after ferrying it home was to replace the stock lapbelts with inertial dual-strap shoulder harnesses in the front seats. In the thirty years I’ve owned it, I have never needed them to lock me down. But it’s the cheapest insurance policy I ever took out.
Flew for years without shoulder harness. Then, at about 15 years of ownership of my last Aeronca, a Chief, I put them in it. After the first flight, I could not imagine not having had them through all the years. But also…sitting right in front of me was the gas tank, and right below it in the panel were two ash trays with a fuel primer right below them. Attitudes change.
I found it surprising that a 20-mile-an-hour crash could be so dangerous. But thinking about it, I watched a football game this weekend where the announcers commented that a player hit 20 miles an hour running back a pick. If I imagine that player running full tilt into a brick wall, the danger becomes a lot more clear.