2
$\begingroup$

Today, I was thinking about seat belts.

On that note, why do the ones in cars and planes differ? Planes have only belts on the waist, but cars have waist and diagonal. Is there a reason that this is so, or are the difference just... [Insert suitable word]?

$\endgroup$
3
$\begingroup$

There's no doubt that lap and shoulder belts are safer than lap belts alone in both cars and planes. The FAA already requires shoulder/lap belts in small general aviation craft, but not (or not yet) in large passenger aircraft. If you notice, the crew on those planes wear 4 point harnesses.

In any case, there are multiple challenges to implementing safer passenger restraints on commercial aircraft. First is just the engineering challenge of where to place the upper attachment point. In a car, the frame of the vehicle is close and easily accessible while in a plane it's not. That means adding the required structure to the seat.

Adding that structure to the seat will inevitably result in a seat that is more expensive, heavier and physically larger. Just replacing all of the seats on pasenger aircraft would be cost-prohibitive on its own, but a larger seat means there can be fewer seats/plane which drives the actual cost even higher. Finally, the seats would be heavier. Heavier seats mean greater fuel consumption also resulting in higher costs.

Finally, there's the behavioral aspect of shoulder belts. Passengers won't like them, especially on long flights. Flight attendants already have their hands full trying to get people to wear lap belts, a more restrictive belt will only aggravate that problem.

$\endgroup$
2
$\begingroup$

Different types of seat belts are designed for different purposes.

The main function of car seat belts is to stop you being thrown forwards during an unexpected accident. A lap-only belt would not prevent your head hitting the windscreen. The lap belt prevents you sliding forwards feet-first, which could cause injury if the front of the car is crushed, or it could cause problems if you need to get out of the car quickly, for example because the accident started a fire.

The main function of an aircraft seat belt is to stop you being thrown vertically by unexpected turbulence, or simply to keep you sitting in your seat during takeoff and landing. The chance of a horizontal impact in a plane crash is usually predictable, and injuries can be avoided by the "brace position" without the need to wear a diagonal belt all the time.

$\endgroup$
1
  • $\begingroup$ A good portion of aircraft accidents are not of the "plane falling from 6 miles up in the sky, we've got time to brace ourselves" variety, they occur during takeoffs or landings where there may insufficient time for a warning. A significant portion of passenger injuries are due to being restrained only at the midsection by a lap belt and being whipped back and forth. Consider what happened with Asiana Flight 214, The majority of injuries were due to being thrown fore and aft while restrained at the waist only. The accident occurred during the day and in favorable weather with no warning $\endgroup$ – DLS3141 Mar 8 '17 at 17:40
1
$\begingroup$

Originally car seat belts were like the airline seat belts. In 1959 the Swedish car marker Volvo invented the three point seat belt and determined it to be the safest type of seat belt, by the way it restrains vehicle occupants. Volvo let other car makers use the belt for a fee of just one dollar ($1) to save lives around the world.

Airline type seat belts are simple to use & simpler to get out of in an emergency in a bulk passenger situation. The seat belt ends stay on the seat. If airlines used the triple point seat belts that are used in cars some passengers may get injured by the belt buckles as they fly back up to there resting positions.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.