Austman

Here's one:

http://flightsafety.org/hf/hf_may-jun98.pdf

There are others including a UK study that showed that the weight of bags in lockers had very little to do with safety in a crash. The study noted that it's almost impossible, with carry on luggage, to exceed the overhead bin load rating.

Dave Noble

The weight of items in an overhead locker has a big impact when someone drops them. 7 Kg falling onto someone likely to do a lot less of an injury than 23Kg

Also, with the weight limit, people are less likely to take the bags onboard - if it isn't there the risk is even lower

With heavier ones being checked in, then more room in bins to accommodate the hand luggage of passengers - cannot remember last time that bags were having to be taken off and checked in due to lack of space in the cabin

nzkarit

Also as the weight goes up people find it harder to lift the bags up and down. If the bags start getting too heavy for people to control while above head height, going to injury people while putting the bags up and getting them down. There are already enough people who don't seem to do this safely and knock/clip people currently.

Also if you can encourage people to have smaller bags which can fit under the seat you can fill and empty the plane faster. If bags got heavier and people needed help putting them in the bins and getting them out of the bins and people needed help to lift etc it will slow things down even more.

Austman

Except the studies show in fact it's the opposite. The smaller, lighter objects cause far more injuries.

But where to draw the limit? I know many people who couldn't safely lift even 5kg. And many others where 15kg is not a problem. The pax has to be able to lift their bag - that's a given.

Considering legal sized bags are often around 4kg when empty, setting the weight limit to what one of those is when filled with typical travel items would seem reasonable to me. Perhaps somewhere around 10kg? But 7kg does seem too light.

Even Jetstar allowed 10kg up to fairly recently, I don't see how playing the safety card when the 7 kg limit is exceed by 2 or 3 kg is actually justified.

nzkarit

Quantity and severity are two difference dimensions. The heavier the object the more likely the person will need time off work, physio, etc

Airlines in this part of the world seem to be currently picking 7kg as the mass. So be it. The PR will say safety, fair access for all passengers to overhead bins (don't want the US where people fight to get on first, so get first dibs on the bins).

But 3kg x Y passengers = fuel costs, lost opportunity to sell checked baggage, etc

A quick google shows that legislation has no fixed number for mass that can be lifted but now need to do a risk calculation based on mass, repetition, environment, etc

og

Overhead bins have a load rating - as is visible from stickers in each overhead space. Airlines adopt a conservative approach to maximum expected loading for that space. I assume there is no way that they will allow passenger bag weight to even approach the manufacturers load rating for those bins. If they do, then there could be a litigation liability in the case of an accident.

nzkarit

And with turbulence, etc which increase the G load the weight of the bags will increase (talking about weight in N rather mass in kg).

I know with rope systems the rope may be capable of 3000kg (~30000N (using gravity at 10ms^-2 rather than 9.8ms^-2)) but will never load it with more than 300kg as with 1s of free fall that 300kg goes from ~3000N to ~30000N. Just as an example for why the maximum loadings are very different from usable loading.

Austman

I've read studies that have shown the bin load rating is almost impossible to exceed on large aircraft. It's just not a safety factor, apparently, if luggage is limited by volume.

Why was 10kg OK before for Jetstar? For many years. Did reducing it to 7kg have anything to do safety? I doubt it.

Dave Noble

You seem blinkered solely on whether the locher can withstand the weight. That is not the only cause of accidents. Much more common is carelessness when taking items out of the lockers . If someone drops 10Kg on someone rather than 7Kg , I would say it is pretty obvious that the risk to the person is higher

Also, if the weight limit is lower, then the number of items taken on board is likely to be lower as more items will be checked in and less of a fight for space => less time requred to get passengers boarded

US airlines seem to need to start boarding 30 minutes before departure where QF may use 20 and do not have issues getting space for hand luggage

og

Without knowing the real reason, I'd suggest consistency across the QF/JQ fleet and possibly more importantly is turn around time for JQ. The more carry ons = the slower turn time as pax and FAs struggle to find space (as per USA). JQ manage to turn in 30 minutes and their schedule so tight that small loading delays compound throughout the day.
I reiterate my comment about JJ with 5 kg where they load fast, everyone pops their stuff overhead and last to board still has overhead space.

lokijuh

I think this is one component of the reason for 7kg maximum, the other is purely commercial in driving people to pay for luggage. Give business (and some leisure) travellers that push to pay for checked luggage - it's actually not that easy to get a few days worth of clothes and a spare pair of shoes AND a laptop into 7kg, especially with older laptops that might take half of the allowance by itself. When they had 10kg it was much easier.

As an aside, I tried once to take 1x7kg wheelaboard and 1x5kg backpack on a Jetstar flight, and told at check-in I needed to check one of the items due to "safety reasons" . Which was convenient untruth, as both were beneath the individual bag limit which was deemed as safe. [Nb: I was just trying it for the sake of convenience - as I had already paid for checked luggage through a plus package, so no big deal for me to check it, conversely if I carried it on, Jetstar would not have missed out on a cent of revenue either]

Austman

But that's all to do with SIZE not weight. If the carry-on is within the size limits, weight seems to have nothing much to do with it - on larger commercial aircraft.

vbroucek

You can argue here as much as you can, but you will not achieve anything. Basically, we all are wasting our time here. If airline says it's X, Y, Z, it is X, Y, Z, full stop.

This is the same as if you were arguing about speed limits. You can produce hundreds of studies that 150kph is no more dangerous than 110kph (LOL, just example), but will they listen to you? No, they will not.

Austman

That's a terrible comparison!!

But what airlines could do is state that carry-on weight limits are "company policy". In other words it's a commercial decision. When they say a 5kg or a 7kg limit is a safety issue compared with eg 10kg, they are basically lying (for modern larger aircraft).

Platy

BUT the airline does not apply the rules on carry on bags consistently (XYZ is not XYZ in practice).

Significantly, if the rule was for safety it would be applied rigorously, uniformly, and consistently, akin to other safety orientated rules (seat backs up, tray tables up, etc).

The rule would also be audited by the safety regulator (CASA) thus encouraging compliance.

As stated by Austman, the rules are for commercial convenience: whether 7kg or 10kg, one bag or two.