Lap seatbelts are not good enough in modern cars lap & diagonal min. Why are lap belts tolerated in aircraft?

Question

I know there is a weight issue in aircraft but lapbelts are dangerous and can cause serious spinal injuries.

Answer 1

It's mostly to do with the fact that airliner seats are easily moved/removed to reconfigure the cabin & therefore difficult to arrange "proper" seatbelts for. In aircraft with seats which are a more permanent fixture (bizjets, private aircraft etc.)there usually is a more comprehensive seatbelt fit. You'll notice that the crew seats (which aren't moved) do have a full fit.

We have 4 point harnesses in the Cessna and in the glider too.

Answer 2

Because aircraft have different kinds of crashes to vehicles.

Cars usually have impact crashes without warning, needing a 3 point safety belt for maximum protection.

In an aircraft, the best form of protection is to adopt the crash position - head between the knees - which obviously is only achievable with a lap belt and not a 3 point belt.

Answer 3

The idea of the lap belt is to prevent passengers for flying off during turbulence. The reason there is no shoulder harness is that the seat back rest is not structurally strong enough to support the weigh. All back rest are designed with a break point if pushed forward (try forcing the backrest fwd next time you are in an airliner and you will observe they yield). If strapped w a shoulder harness during a crash you will be sling fwd violently and cause more damage. For that same reason the back rest in front of you is designed to absorb the energy of the person behind crashing into it.

At the end it all come down to weigh. In order to build a seat that can restrain a 250 lb man flying at 120+ Kts using shoulder harness the seat wuld have to be constructed with stronger metals thus increasing weight.

Answer 4

Commercial Aircraft SEATS aren't configured nor engineered to take the stresses involved in a shoulder-strap restraint system, much less a 4 or 5 point system.

ComAir belts are really just to keep you in your seat during turbulence (the BIGGEST cause of injuries / death in commercial aircraft), and yes... to hold the body for recovery.

COMFORT is an issue... I used to fly in the SH-60B and S-3B... wearing a 5 or 4 point system for 4 to 8 hours SUCKS !!

Answer 5

I don't think it's a weight issue but all aircraft would need to be retrofitted and cost is what the airlines don't want. Also, most people would not want to wear a diagonal if they were flying for a long time. If you notice, most people when flying, remove their seatbelts anyway, once the seatbelt lights go off. However, as I said before, cost is a major factor in this.

Answer 6

Most car accidents are sudden. You dont get any time to prepare for collision.

Aircraft are different. Most SURVIVABLE accidents give the passenger enough time to get into a BRACE position. This is why seatbelt use and proper BRACE position is taught to you (by flight attendants) at the begining of every commercial flight. When you are in that position, the uppper body wont swing forward suddenly, so you are not likely to need that upper (diagonal) brace as much.

Pilots in aircraft (military for example) who are likely to encounter more unusual G forces, akin to a car accident, wear 4 or 5 point harnesses!

Answer 7

If you are heading in for a crash landing, you are supposed to put your head between your legs and kiss your a s s good bye lol, but no, really your supposed to put your head between your legs to prevent injuries. 3 point belts are not required in aircraft.
Like most of the people stated above, since car accidents are sudden you don't have any time to brace yourself.
As in a airplane crash we will get on the intercom and advise you on what to do in any such emergency. You also got to remember this too, Airline travel is the safest way of travel...

Captain, Chris W T
ATP- Lear 45, B747- A318 - A380
CFI

Answer 8

To understand why some aircraft only have a seat belt and not a shoulder harness you have to under the certification rules for aircraft from the old CAR’s Civil Air Regulation to the current CFR’s Code of Federal Regulations. Under the CAR’s only a lap belt was required and on March 1, 1979 the CFR replaced the CAR’s. The new rules in CFR 23 and 25 required all aircraft manufactured after March 1, 1979 to have both a lap belt and a shoulder harness.

The reason for the shoulder harness was to keep the pilot and co-pilots head out of the instrument panel. The TSO the covers seat belts is TSO-C22 the new standard is all seat belts on aircraft have to survive up to 21 G loads.

A determination of design loads for combined shoulder harness and safety belt installations in civil aircraft has been a long standing issue. Part of the issue has been resolved by the issuance of TSO-C114. Formerly, there was no aviation standard for shoulder harness systems in civil aircraft. Consequently, commercial production shoulder harness systems usually have the same rated strength as the minimum specified for the safety belt. Shoulder harness attachment points designed into aircraft by manufacturers generally follow the same practice. Each safety belt with shoulder harness, must be approved. Each safety belt with shoulder harness must be equipped with a metal to metal latching device.

The human body has the inherent capability of withstanding decelerations of 20g's for time periods of up to 200 milliseconds (.2 second) without injury. Experience with aircraft used in agricultural and military operations shows that even in such unusual operations a high rate of survival in crashes is achieved when a restraint system is designed on the order of 20g to 25g deceleration loads.

A number of combined shoulder harness and safety be1t designs evolved to satisfy the occupant protection requirements of the FAR. Some designs developed for automotive and military aircraft applications may also be applicable in civil aircraft. In conjunction with the shoulder harness and safety belt development, a variety of integral hardware components has evolved to satisfy the coupling, the adjustment, the crewmember movement, and the stowage requirements. An aircraft certification office (ACO) should assist in evaluating data necessary for the addition of a shoulder harness assembly to an installation previously approved with a safety belt only.

Damage to seat belts, such as scuffing, fraying and breakage of fibers is considered acceptable. The seat belt should not be cut, or torn by features of the seat or the belt adjuster mechanism. Cuts or tears should be investigated as to their cause, and appropriate corrective action taken, although a retest may not be necessary.

RELATED READING MATERIAL.

a. TSO-C22f, "Safety Belts," Technical Standard Order, Federal Aviation Administration, February 24, 1972.

b. TSO-C39a, "Aircraft Seats and Berths," Technical Standard Order, Federal Aviation Administration, February 24, 1972.

c. "Motor Vehicle Seat Belt Anchorages Test Procedure - SAE J384," SAE Recommended Practice, 1979 SAE Handbook, Volume 2, pp. 33.08-33.09, Society of Automotive Engineers, Inc., 1979.

For installations In normal category airplanes, apply a test load of at least 1530 lbs. (9g x 170 lbs.). For installations in utility and acrobatic category airplanes, apply a load of at least 1710 lbs. (9g x 190 lbs.). The load should be applied in the forward direction of the airplane longitudinal axis and held for at least 3 seconds without failure.

Design of the Article. Compliance with the standards of TSO-C127, TSO-C39, TSO-C39a, TSO-C39b, or the applicable airworthiness standards may not, alone, ensure that the article has no unsafe features that experience has shown to be hazardous. The persons modifying the article should determine that the design contains no hazardous features.

Notwithstanding § 91.205(b)(12), an approved safety belt needs to be provided for each seat.

RELATED FEDERAL AVIATION REGULATIONS (FAR) SECTIONS. Sections 23.561, 23.785, and 23.1413 of FAR 23; Sections 27.561, 27.785, and 27.1413 of FAR 27;
Sections 29.561, 29.785, and 29.1413 of FAR 29; and Sections 91.107 and 91.203 of FAR 91.

Answer 9

The real answer comes down to paying passanger comfert!
Who would want a shoulder belt on a 14 hr flight.I might add that most buisness aircraft do have shoulder belts

Answer 10

The seatbelts are very rarely needed for helping in deceleration... the two point belts are plenty for holding you in place vertically...