Reducing major injuries
By Fred Workley
We are generally very diligent about adhering to checklists used for flying and maintaining the airplane. One area that needs constant vigilance is seats and restraint systems.
How many people use the seat belt and shoulder harness every time they get in the airplane? I vividly remember sitting in a second floor classroom at Oakland Airport and watching a Cessna 150 stopped on the ramp, flip over. It ended up with the aircraft upside down with the gear pointing up. The airplane got caught in the jet blast of a DC-8 turning on to the taxiway in front of where the C-150 was stopped. Both pilots in the C-150 had shoulder harnesses on and they were very suppressed but uninjured. You cannot predict when seat belts and restraint systems become a very important safety system.
Studies of "serious" accidents, over time, have shown that the proper use of seat belts and shoulder harnesses reduces major injuries by 88 percent and reduces fatalities by 20 percent. Some aircraft incidents and accidents result in minor or no significant risk to the airplane or its occupants. And since Dec. 12, 1986, all small aircraft manufactured must have shoulder harnesses for all seats.
FAA regulations require the seat belts and shoulder harnesses (when installed) be properly worn during takeoffs and landings. A slack restraint system can’t protect you in a serious impact. The reason: the body keeps moving forward until the slack is taken up. At some point your body must abruptly stop to "catch up" with the airplane. In other words, the restraint system should be adjusted as tight as possible within reasonable comfort levels. The goal is to minimize potential injuries.
The seat belt needs to be placed low on your hipbones. This permits the belt loads to be taken by the skeleton strength of your body. If the belt is on your thighs it cannot limit your body’s forward motion. Internal injuries can be caused if the seat belt is too high on the abdomen.
Shoulder harness systems can either be a single diagonal belt or dual shoulder belts. The design of the belts should avoid rubbing the head or neck to preclude neck injuries during an impact. A single diagonal shoulder harness needs to be positioned so that the body’s upper torso center of gravity is within the angle formed by the seat belt and the shoulder harness. The shoulder belt has to be tight enough to prevent the torso from slipping out.
The lower end of the shoulder harness is usually fastened to the safety belt buckle or the buckle insert. Thus the safety belt buckle for a single diagonal strap should be positioned on the side of your hip. This differs from the central location of the buckle that is common when only the safety belt is installed. As the single diagonal shoulder harness is so low on the hip, it has to be unlatched without interference from the interior wall of the airplane, the seat armrest, or aircraft controls.
A dual shoulder harness installation is usually fastened to the safety belt near the center of the torso and the shoulder belts will tend to pull the safety belt up off your hipbones. This may cause internal injuries during an impact. To prevent this, when the safety belt is tightened about the hips the seat belt should be positioned so that it makes an angle of about 55 degrees with the centerline of the airplane. Some dual shoulder harness installations have a tie-down strap from the buckle to the center, forward edge of the seat or floor structure. This tie-down resists the upward pull of the shoulder harness. The tie-down strap needs to be adjustable to remove slack. A properly installed and adjusted tie-down strap should be comfortable.
Only provide safety when used
Unless restraint systems are used they can’t perform their safety function. Accident injuries, in general aviation, have occurred because occupants were not wearing seat belts or shoulder harnesses or the seat belt was loose. If the restraint system is unbuckled there is no time to fasten it in a sudden impact. Seat belts alone will only protect you in minor impacts.