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Use of Safety Belts and Shoulder Harnesses – Advice in AC 605
From January 2015 Bits & Pieces Newsletter
By Ian Brown, Editor – Bits and Pieces, EAA 657159
The following is extracted from the recent Transport Canada Civil Aviation Advisory Circular (AC) 605-004. TCCA recommends that installed safety belts and restraint systems be inspected in accordance with the manufacturer’s schedule or the approved maintenance standard. All observable tearing or fraying should be promptly reported to maintenance personnel as this can reduce the design protection of the entire safety belt.
Proper Use of Safety Belts and Shoulder Harnesse
- While it is important to wear a safety belt and shoulder harness where provided, they will not provide full benefits if worn improperly, and in some cases, may even cause injury in a serious impact.
- Crashworthiness tests have shown that slack in a restraint system should be minimized as much as possible while being worn. During impact, the occupant’s body continues to move until the slack is taken out of the restraint system, but then the body must abruptly halt to catch up with the forces of the aircraft. The restraint should be adjusted as tightly as one’s comfort will permit to minimize potential injuries.
- The safety belt should sit low on the hip bones so that the belt loads will be transferred to the skeletal system. Otherwise, internal injuries can result if the belt is placed across the abdomen. If the belt is positioned on one’s thighs rather than the hip bones, it cannot effectively limit the body’s forward motion.
- Shoulder harnesses can consist of a single diagonal upper torso strap, similar to those used in automobiles, or dual upper torso straps. The straps should not rub against a person’s head or neck. Not only is this uncomfortable, but it can also cause neck injuries during an impact.
- Single diagonal shoulder harnesses should be positioned so that the torso’s centre of gravity falls within the angle formed by the shoulder harness and the lap strap portion of the safety belt. Otherwise, a person’s torso could slip out of the shoulder belt during impact and compromise his protection. The lap strap buckle should also be positioned on the side of the occupant’s hip. This differs from the central location of the buckle when only a lap strap is available for use. The buckle should also be unlatched without any interference at all from the seat armrest, aircraft controls, or the interior wall of the aircraft.
- If the shoulder harness consists of dual upper torso straps fastened to the lap strap near the centre of the body (i.e. a four-point harness), the upper torso straps will tend to pull the lap strap up off the person’s hip bones. This may lead to internal injuries during an impact. It is important that the lap strap be positioned low on the hips and tightened properly in order to resist the upward pull of the upper torso straps, reducing the risk of internal injury.
- Alternatively, if the shoulder harness consists of dual upper torso straps along with a tie-down strap from the buckle to the centre-forward edge of the seat (i.e. a five-point harness), it should be adjusted to remove all of the slack when the restraint is used.
- TCCA reminds all aircraft operators of the regulatory requirements to wear safety belts, including a shoulder harness, if installed. TCCA strongly encourages the use of safety belts and shoulder harnesses at all times when the aircraft is in motion.
Turbulence and the Use of Safety Belts
In-flight turbulence is the leading cause of in-flight injuries to passengers and crew members.
There have been accidents and incidents over the years involving clear air turbulence that have resulted in serious injuries and fatalities to passengers and crew members. Numerous post-accident reports reveal that while the safety belt sign was on when the aircraft hit turbulence, passengers and crew members had not been wearing their safety belts.
These post-accident reports highlight the importance of keeping safety belts fastened throughout the flight while seated.
Editor’s note: From personal experience, the seat belt should feel uncomfortably tight to most people if it’s tight enough. A very small amount of slack can allow a passenger to move a lot in a light aircraft in turbulence. Fly safe, and snug up that safety belt.