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Topic: Why Seat Belt On Planes Not The Inertia Type?
Username: BA747
Posted 2008-11-19 15:19:01 and read 12972 times.

Hi, I was wondering instead of the seat belt that one have to adjust, why airlines don´t put the car type?

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: B747forever
Posted 2008-11-19 15:29:30 and read 12953 times.



Quoting BA747 (Thread starter):
, I was wondering instead of the seat belt that one have to adjust, why airlines don´t put the car type?

I wonder that too. The car belt type seems much safer.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Caryjack
Posted 2008-11-19 15:31:08 and read 12944 times.

I'd guess higher weight, cost and maintenance with lower reliability.  Smile
Cary

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Boeing767mech
Posted 2008-11-19 15:33:01 and read 12934 times.

Quoting BA747 (Thread starter):
Hi, I was wondering instead of the seat belt that one have to adjust, why airlines don´t put the car type?

Two words:

weight and cost. the reels for the seat belts weight about 2 pounds more than a normal seat belt. Also is take 5 mintues to change a seat belt now, with a reel it would take longer and would casue delays on turn arounds.

David

[Edited 2008-11-19 15:36:10]

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Overcast
Posted 2008-11-19 15:35:09 and read 12924 times.

I think Inertia Seat Belts are good at locking in a certain plane, i.e. They will lock when you hit a wall. But not that good if the car gets drops 20 feet vertically.

So in aviation terms they may be ok when you crash land and hit something, but probably won't stop you hitting the ceiling in turbulance.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: B747forever
Posted 2008-11-19 15:35:13 and read 12923 times.



Quoting Boeing767mech (Reply 3):
weight and cost.

Well is weight and cost more important that safety??

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: WN700Driver
Posted 2008-11-19 15:31:23 and read 12924 times.

Not 100% sure, but I'll make like OJ and take a stab at it. It probably has something to do with the fact that seat belts are more to keep you from banging your head into the overhead or PSU's (during severe turbulence or rough landings) than keep you alive through a wreck. Even on our deminuative Dash 8-300s, in a collision at speeds of over 180 per, belts wont do much for you, inertia or otherwise.

Edit: The shoulder straps up front (Pilots, observer's and FA's) are inertia types. But only the shoulder parts. The lap sections are still the manually tightening type. Can't believe I forgot that.   

[Edited 2008-11-19 15:36:41]

[Edited 2008-11-19 15:37:44]

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: DL767captain
Posted 2008-11-19 16:30:43 and read 12816 times.

It seems to me the seat belts are there for if the aircraft plunges (like the Qantas A330) to keep people in their seats, I can't really imagine any type of seatbelt keeping passengers alive in an actual crash

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Tdscanuck
Posted 2008-11-19 16:58:40 and read 12760 times.



Quoting BA747 (Thread starter):
Hi, I was wondering instead of the seat belt that one have to adjust, why airlines don´t put the car type?

I'd agree with weight and reliability.

Quoting B747forever (Reply 5):

Well is weight and cost more important that safety??

Not more important, but when safety is equal, you don't go for more weight and less reliability. An inertia reel isn't really safer than a regular airplane belt, if you're wearing the airplane belt properly.

Also, there is *always* a tradeoff between cost (weight, reliability, etc.) and safety. This rubs a lot of people the wrong way, but it's true. You could make airplanes much safer than they are, but it would drive the cost of flying so high that nobody could afford it, so there's no point. It's the same reason that the FAA doesn't mandate that all AD's be done right away, even though they have that power.

Tom.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Crjfixer
Posted 2008-11-19 17:15:53 and read 12730 times.

The Crew seatbelts on most aircraft are the inertia type, but not for the pax. And as DL767 said the seatbelts are mainly for turbulence and the like. In an actual crash a seatbelt wont help much no matter what type sadly.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: UAL Bagsmasher
Posted 2008-11-19 17:50:23 and read 12662 times.

To change a pax seat belt takes about 30 seconds. To change the inertia reel on a pilot seat (on a CRJ-200) can take over a half hour depending on how any times you've done one.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: VV701
Posted 2008-11-19 17:53:52 and read 12656 times.

The functions of a car seat belt and an airlimne passenger seat belt are entirely different.

A car seat belt is designed to minimise injury when the car is in a full head-on crash. If you have a full head-on crash in an aircraft . . .

An aircraft seat belt is designed to minimise injury during severe turbulance (be it turbulance caused by a natural atmospheric phenomena, by aircraft performance or relatively low stability during take-off and landing).

Hence the requirement is to wear a car seat belt whenever the car is in motion. But airliners are fitted with "fasten seat belt" signs as it is not required to wear them at all times that the aircraft is in motion.

Clearly if fitting lap belts instead of inertia chest belts is a cost saving exercise designed to save installation costs and weight then the airlines are missing a lot of opportunities. Why go to the bother and cost of fitting the seat-belt signs when they could save that cost and weight simply with a safety instruction card that told the passengers to keep belted up at all times?

Other possible cost savings they could consider would the cost and weight saving of getting rid of WCs and galleys. If passengers had to remain belted-up at all times when the aircraft was in motion they clearly could not use the WCs and serving food and drink during a flight would cause passengers significant problems. So would we need FAs? Or is their safety unimportant? After all if they and the passengers had to remain belted-up throughout the flight what would they do?

Yes. It is all prertty ridiculous. But think about it. Is it any less ridiculous than suggesting airlines are putting cost savings before passenger safety by using lap belts and not inertia reel chest belts?

And a final thought. You are in an airliner and wearing an inertia reel, car-type, crash (not safety) belt. The aircraft is in trouble and is going to crash land. So what do you have to do? First you release the seat belt catch. Only then can you adopt the position recommended by all airlines' safety cards in the event of a crash. So your inertia reel belt would actually be a safety hazzard as on impact you will now be thrown about the cabin.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: DfwRevolution
Posted 2008-11-19 18:03:40 and read 12632 times.



Quoting B747forever (Reply 5):
Well is weight and cost more important that safety??

Yes, there is a cost/benefit ratio to everything. Contrary to what we tell our children, life is not "priceless."

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: NWADC9
Posted 2008-11-19 18:12:04 and read 12609 times.



Quoting WN700Driver (Reply 6):
Edit: The shoulder straps up front (Pilots, observer's and FA's) are inertia types. But only the shoulder parts. The lap sections are still the manually tightening type.

What about the front seats on RJs like the Do328 where they have a shoulder strap along with the lap belt? Are they inertia types too?

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: SPREE34
Posted 2008-11-19 18:20:42 and read 12585 times.



Quoting B747forever (Reply 5):
Well is weight and cost more important that safety??

Who says they are safer?

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: TZTriStar500
Posted 2008-11-19 18:42:36 and read 12539 times.



Quoting WN700Driver (Reply 6):
It probably has something to do with the fact that seat belts are more to keep you from banging your head into the overhead or PSU's (during severe turbulence or rough landings) than keep you alive through a wreck. Even on our deminuative Dash 8-300s, in a collision at speeds of over 180 per, belts wont do much for you, inertia or otherwise.



Quoting DL767captain (Reply 7):
It seems to me the seat belts are there for if the aircraft plunges (like the Qantas A330) to keep people in their seats, I can't really imagine any type of seatbelt keeping passengers alive in an actual crash



Quoting VV701 (Reply 11):
An aircraft seat belt is designed to minimise injury during severe turbulance (be it turbulance caused by a natural atmospheric phenomena, by aircraft performance or relatively low stability during take-off and landing).

While this may seem logical, this is not true. Airline seat belts are designed to regulations to restrain a 50th percentile male in the seat to the same crash and/or dynamic conditions as the seat itself (e.g. a 9g seat requires a 9g seat belt and a 16g seat requires a 16g seat belt). They are dynamically tested with and considered an integral part of the seat and must also meet TSO C22. Seat belts are really designed for crash conditions along with the seats and anything else in the passenger cabin as this is the most critical.

I can recall that mandatory seat belt use used to be only during takeoff and landing, but about a decade or so ago with the increase in turbulence related injuries, airlines have been requiring them more during flight. FAR 121 only requires a seat and seat belt be available for each occupant, but is only required to be secured during movement on the surface, takeoff, and landing.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Mir
Posted 2008-11-19 20:07:38 and read 12432 times.



Quoting B747forever (Reply 5):
Well is weight and cost more important that safety??

There is always a tradeoff. In this case, an inertia seatbelt is not going to be much safer than the standard seatbelt, if at all. Therefore, weight and cost are big considerations.

-Mir

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Caryjack
Posted 2008-11-19 22:06:07 and read 12300 times.



Quoting SPREE34 (Reply 14):
Who says they are safer?

I don't. In fact I don't see how they could be. Inertia types are designed to reel and unreel seat belt fabric for comfort while locking for safety as required. If they fail to reel it in or lock, the belt won't hold and if they fail to reel it out the belt will become too tight. There are just too many moving parts to be as reliable, therefore safe, as the belt now being used.
Cary

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: WNCrew
Posted 2008-11-19 22:17:30 and read 12291 times.

Also, aircraft seats aren't designed to stay stationary (like that in a car) but they are designed to collapse and to be impacted by the human body. Were you to install an inertia reel seatbelt or shoulder harness-strap on an aircraft seat, the seatbelt would pull the seat with it instead of letting it do it's job of absorbing the impact of the occupant behind you. This is something I learned from my FAA training.

When pax say "Why do you get the harness and we just get the seatbelt?" I just say 'We can hardly get you to wear the seatbelt, muchless a harness..." They usually realize my point and smile. I find it funny that pax get up when they see FA's get up regardless of turbulence OR the seatbelt sign, yet FA's stay buckled until taxi-in and Seatbelt sign is extinguished and pax unbuckle as SOON as we land...huh

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: LarSPL
Posted 2008-11-20 02:37:36 and read 12106 times.

i don't know why the safety card is played here.
even on a car seat belt the part around the middle is not inertia.
only the shoulder is an inertia system.
that inertia system is there because if you would have a belt around your shoulder which would not give in during a crash it would lead to more damage than an inertia belt (because of the inertia lock the amount of crash force is absorbed by the inertia reel.).
however: you dont want your waist to move during a crash nore is the inertia system necessary at the waist.
the crash position in aircraft for pax is designed to do the same as a inertia reel; absorbe the crash force.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Bill142
Posted 2008-11-20 02:42:32 and read 12101 times.



Quoting VV701 (Reply 11):
If you have a full head-on crash in an aircraft . . .

Aircraft aren't exactly designed for head on crashes...

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: DocLightning
Posted 2008-11-20 05:11:51 and read 11746 times.



Quoting Overcast (Reply 4):
I think Inertia Seat Belts are good at locking in a certain plane, i.e. They will lock when you hit a wall. But not that good if the car gets drops 20 feet vertically.

Depends on the type. There is one kind of reel that locks if it starts to spin too quickly. So that would not depend on direction of force, just the force.

But that reel is heavier. And if you need the seatbelt to be a bit looser, just loosen it.

For those of you talking about crashes, a seatbelt is worthless when a machine made of thin aluminum hits the ground or water at a few hundred MPH. That's not what it's for.

It's to keep you from getting thrown around the cabin in a sudden extreme maneuver or during turbulence. That's why you should keep it on at all times. I've definitely been on some flights where the seatbelt was the only thing holding me in my seat.

Now, someone needs to throw a few million dollars at a grant to figure out why turbulence ONLY seems to happen 30 seconds AFTER you have been served hot coffee.  Wink

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Voar
Posted 2008-11-20 06:28:29 and read 11295 times.

Seat belts on newer piston aircraft are generally of the inertial type for all occupants, so not sure about the weight argument. Some manufacturers even have airbags on the seat belts for increased protection.

I would think that on an airliner an inertial type seat belt would not be comfortable for passengers as it always is pressing against you, would make it harder to sleep for example. On a light aircraft that is not possible, passengers have to sit upright all the time.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Guth
Posted 2008-11-20 08:39:47 and read 10510 times.

I used to fly a Cessna 172R that had inertia reel belts. They were most annoying. As the belts aged they started to fray and would get caught up in the retraction mechanism. Just before I stopped flying the plane I would have to stick my fingers into the reel every time and manually rotate it to get the belt to retract or unlock or do anything.

I say keep the old style belts as the inertia reel type aren't worth the hassle.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: EMBQA
Posted 2008-11-20 09:05:10 and read 10320 times.



Quoting B747forever (Reply 1):

I wonder that too. The car belt type seems much safer



Quoting BA747 (Thread starter):
why airlines don´t put the car type?

Very simple.... because with a car you have 3 point hard contact points with the floor/frame, the B Pillar and the Clip/Latch... with an aircraft passenger seat you have no way to add the third point.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: VScaptain
Posted 2008-11-20 09:36:07 and read 10100 times.

VS have inertia type belts on there Upper Class Suites.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Boeingluvr
Posted 2008-11-20 09:41:01 and read 10195 times.

An Inertia harness/belt can cost in excess of 700-1000 dollars each! that's huge money when you think of an entire fleet, not to mention spares etc... I think someone said it before. The chances of you hitting a wall where the inertia belt would take effect is pretty slim, not to mention if you did you'd be dead anyways. Also if you have to reject, even the inertia from that isn't enough to cause any damage with the current seat belts. Like everyone else has said, thery do there job of keeping people down when in moderate to severe turbulance, and hard landings. I don't think airlines can justify the cost of replacing them.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Ckfred
Posted 2008-11-20 11:30:38 and read 9560 times.

Here's something that's slightly off the topic. Why don't airplanes use car belt buckles? In a car, you push a button to release the seat belt. On an airplane, you lift a latch. I've heard stories about people, in an emergency situation, pushing on their belt buckles with a finger or thumb, trying to get the belt to separate.

Why? Because that's what they do, when they get out of a car.

I've heard safety experts say that airplane seat belts should have the same types of belt buckles as cars.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Birdbrainz
Posted 2008-11-20 11:31:02 and read 9566 times.



Quoting DL767captain (Reply 7):
It seems to me the seat belts are there for if the aircraft plunges (like the Qantas A330) to keep people in their seats, I can't really imagine any type of seatbelt keeping passengers alive in an actual crash

This is off-topic, but I remember reading somewhere that most passengers are killed by fire, smoke, and fumes, and not the actual impact. This is especially true if they can get into a brace position. The UA 232 crash at Sioux City showed this.

Of course, it all depends on the crash. It wouldn't have mattered for the pax of AA587, but for the Delta Connection CRJ that crashed in Lexington, I'd be willing to bet there were survivors of the initial impact because of the seatbelts.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: JOEYCAPPS
Posted 2008-11-20 13:09:23 and read 9004 times.



Quoting WN700Driver (Reply 6):
Edit: The shoulder straps up front (Pilots, observer's and FA's) are inertia types. But only the shoulder parts. The lap sections are still the manually tightening type. Can't believe I forgot that.

IMHO I believe that jumpseats in most aircraft are rear facing. The inertia seatbelts are a plus because as the aircraft takes off, pax are thrown into their seats, whereas crewmembers need the shoulder harness because they need to remain upright, versus slouching/leaning forward on takeoff.

I don't care what kind of seatbelt is used; if its bad enough to require a shoulder strap to stop you from flying to the front of the cabin, obviously its one powerful impact, I mean...

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: OldAeroGuy
Posted 2008-11-20 15:07:42 and read 8307 times.



Quoting Boeing767mech (Reply 3):
weight and cost.



Quoting Caryjack (Reply 2):
I'd guess higher weight, cost and maintenance with lower reliability

Plus the certification hassle.

Quoting B747forever (Reply 5):
Well is weight and cost more important that safety

Please explain how the current airplane safety belts are unsafe.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: UniTED
Posted 2008-11-20 15:16:04 and read 8264 times.

I actually know of the Inertia type existing in passenger seats. In the new United First Suites, there are the shoulder straps. Interestingly enough, they are not present in the backward
facing new United Business seats.

you can sort-of see the hole in the upper corner of the seat, where the diagonal seatbelt is attached.

Big version: Width: 400 Height: 267 File size: 74kb


maybe it's because this seat is more diagonal than the previous First Suite? But then, why don't VS, DL, CX have this in their "herringbone" configurations? Or do they?

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: TZTriStar500
Posted 2008-11-21 08:03:18 and read 7990 times.



Quoting Ckfred (Reply 27):
Here's something that's slightly off the topic. Why don't airplanes use car belt buckles? In a car, you push a button to release the seat belt. On an airplane, you lift a latch. I've heard stories about people, in an emergency situation, pushing on their belt buckles with a finger or thumb, trying to get the belt to separate.

Why? Because that's what they do, when they get out of a car.

I've heard safety experts say that airplane seat belts should have the same types of belt buckles as cars.

Because its likely the push button latch would not survive the 16g airline seat belt requirements.

Quoting OldAeroGuy (Reply 30):
Please explain how the current airplane safety belts are unsafe.

They are not as they meet current regulations.

Quoting UniTED (Reply 31):
Interestingly enough, they are not present in the backward
facing new United Business seats.

Because rear facing seats don't have the same loading as a forward facing seat in the interface of the occupant.

Quoting UniTED (Reply 31):
maybe it's because this seat is more diagonal than the previous First Suite? But then, why don't VS, DL, CX have this in their "herringbone" configurations? Or do they?

No, a shoulder harness is not a regulatory requirement, but may have become necessary to meet the headstrike and 16g forward regulatory requirements. Yes, the herringbone or diagonal seat placement does make it more difficult to design and certify as the fwd load vector is at an angle to the seat and the occupant.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: Bongodog1964
Posted 2008-11-21 09:06:08 and read 7935 times.

The requirements for a car seat belt, and a plane seat belt are entirely different.

A car belt has the requirements to allow movement of the upper body, in order to reach for things, but to be available almost instantaneously to provide protection. As it is worn at all times when the car is in motion, the inertia reel system provides that movement. In addition the car belt has a shoulder strap as the car impact position for passengers is upright, to prevent contact with the dashboard, which in a front impact will be heading towards you.
Hence the car belt has an inertia reel.

When you are in a plane seat, the belt is not there to restrain you in the event of sudden incidents; it is there to provide restraint in the event of a pre warned incident in which you would assume the "brace" position. An inertia reel system would provide no protection if you already have your head jammed against the seat in front, you are as far forward as you are going, unless the seat in front disappears. If that goes there's not much hope anyway.

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: 123
Posted 2008-11-22 06:57:32 and read 7709 times.

In the SQ new C Class, you have two seatbelts: When the seat is in normal position, it´s a special seatbelt with an airbag (yup!) - normal locking/size adjustment system.

Whe the seat is in lie-flat position, you have another seatbelt, like the cartype, which is fantastic because you get to move around when you are lying, yet are not restrained, and also nevertheless secured.

SQ: They know how to do things better  Smile

Topic: RE: Why Seat Belt On Planes Not The Inertia Type?
Username: PGNCS
Posted 2008-11-22 10:37:12 and read 7596 times.



Quoting Crjfixer (Reply 9):
The Crew seatbelts on most aircraft are the inertia type, but not for the pax.

Correct me here if I am wrong, but for most airliners the LAP BELTS in the cockpit are NOT inertial. I have flown 8 types of airliners under FAR 121 and the lap belts have never been inertial, only the shoulder harnesses have. Since the cabin on almost all airliners solely has lap belts for the passengers, I don't see any differentiation. The FA seat belts vary widely by type, but I believe that most lap belts are not of the inertial type, either, similar to the cockpit. I have ridden on several different FA jumpseats and have never seen an inertial lap belt.

Quoting JOEYCAPPS (Reply 29):
I believe that jumpseats in most aircraft are rear facing.

They face both directions. The forward FA jumpseats are normally rear facing, but further back it varies widely by configuration.

Quoting B747forever (Reply 1):
Quoting BA747 (Thread starter):
, I was wondering instead of the seat belt that one have to adjust, why airlines don´t put the car type?

I wonder that too. The car belt type seems much safer.

How does it seem safer?

Quoting TZTriStar500 (Reply 32):
Quoting OldAeroGuy (Reply 30):
Please explain how the current airplane safety belts are unsafe.

They are not as they meet current regulations.

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