I had started to write a post about a recent wide body jet I had to deal with in work and about the loading of cargo and bags on it, then realised I better start with an explanation into loading of smaller aircraft.
So you've all seen the ramp guys chucking/throwing/pass the parcel-ing/delicately placing the suitcases into the belly of the aircraft, but have you ever considered it in anymore thought than that? Unless your an aircraft buff/engineer/physicist etc then I hope not but here's a short explanation into what happens.
For example, one of our flights with an A320, with 180 people onboard and nearly all of them having suitcases checked in will result in around 180 bags. At an average of 15kg per bag, those 180 bags amount to 2700kg. That means we have 2700kg of bags to place in the belly holds and that need to be distributed so that the aircraft not only remains in balance, but go one step further and make sure it's distributed to give an aft Centre of Gravity and help reduce fuel burn. Most of the flights I deal with are all lose loaded, the bags are loaded on individually and aren't contained in the big metal bins or Unit Load Devices (ULDs) you'll see on some of the larger aircraft.
On the A320s I work with, there are holds both fore and aft of the wings. The front hold is numbered 1, there is no number 2 hold for reasons beyond me, and then hold 3 and 4 are located aft of the wing. There is also a smaller hold 5 at the tail of the aircraft which we rarely (have to) use. The aircraft in question, without passengers and bags is pretty well balanced, not too nose heavy or tail heavy, so the obvious answer would be to split the bags between the front and back equally. Almost, but that's pretty much what we do.
The standard way we load a full A320 is by putting 1/3 of the bags in H1, 1/3 in H3 and the other 1/3 in H4. So 60 bags each in 1, 3 and 4 resulting in 900kg in each hold. This holds true for when the aircraft isn't full as well, with lighter passenger loads we can still split the bags up into 1/3s among the holds providing the passengers are distributed equally throughout the cabin. 99 times out of 100, this method works fine and if we're feeling adventurous and have the time, we'll co-ordinate with the flight crew to try and refine it to an even more suitable arrangement producing a more ideal CoG.
A321s I don't have a lot of experience with and so I can't tell you off hand the way we usually load them, but we do have to be a bit more careful. The longer fuselage means any weight in H4 or H5 has more of an effect in making the aircraft tail heavy. If you're not careful enough and place too much weight in H3/H4 without any in H2, you'll very quickly find the tail making it's way to the ground and have endless paperwork to fill in as the flight crew berate you, to put it lightly.
For 737s, it varies depending on which series. On the older -300s and -400s, we're generally load around 100-120 bags in H3 and anymore in the front in H2. On the larger -800s, we'll usually fit around 140 bags in hold 3 aft of the wings, and the remaining 30-40 in the forward holds.
For 757s, the numbers are bigger yet again with around 180 bags in the rear split between holds 3 and 4, and then the rest in H2.
Some particular aircraft have their specific quirks about them. For example some aircraft are particularly nose heavy or tail heavy due to modifications, such as those that operate dual role and have a cargo door in the side of the fuselage. We'll always load and unload the aircraft in such a way as to minimise the possibility of it tipping while on the ground, meaning we'll generally load weight in the front first, and start offloading the weight from the rear on arrival. I've had captains call me overly cautious about my order of loading. However, that's easy for them to say, they won't be the one taking responsibility for it if it ends up nose up while sitting on stand.
Anything bigger than these such as 767s, A300s and A330s are in my experience all bin loaded and so get a bit more complicated. At least now the next time you see the ramp guys place some bags in a hold and then moving to the back/front hold before the other is full, you'll have an idea why. Now I can get on with finishing my wide body post...
Subscribe to:
Post Comments (Atom)
4 comments:
Very insightful. Does the 1:1 ratio between people and bags vary depending on the type of flight? (In other words, for domestic, it's 1:1 and for international, the rule might be 1:2?)
I've heard (and take this with a grain of salt -- you know how rumors and lies are in aviation) that the "Hold 2" on the A320 was omitted in case there was a ever a stretch version with a forward plug. The new hold created could then be "Hold 2" without disturbing the numbering of everything behind the wing.
For most of our holiday type flights to exotic locations, it's pretty much 1:1. Throw in a few familes with infants and it starts to vary as things like pushchairs also count.
For some of our shorter domestic flights where many more of the passengers are business travellers, it can vary from 2:1 or 3:1. I've had fligths with around 60 passengers but only 15 bags, but then again sometimes 80 on the same flight and 60 bags.
I think the fewest bags I have ever put on an aircraft, other than zero, was 4. But then again there were only 4 passengers on the flight.
Interesting about the H2 explanation, thanks. I'll have to try and bring it into conversation during our down periods and see what people think.
So I noticed that you actually load the aircraft based on number of bags and not actual weight.
Isn't there the chance of loading up 60 bags in one hold that all happen to be less than the average weight? (ie 5-10kgs?).
Blake,
I've often thought about the same thing, and as a past student of statistical mechanics would be tempted to try and work it out if I had a pencil long enough and piece of paper big enough.
The same question applies to using standard passenger weights, there's always a chance the heavier passengers are seated in one zone and another is dominated by lighter.
There is a miniscule chance that we'll end up with maybe 60 bags that only weigh 5kg and then 60bags that weigh 25kg, and an even smaller chance we'll end up with all the heavier ones in one hold and the lighter ones in another. If it is looking a bit odd and the ramp guys notice an unsually light arrangement, they'll bring it to our attention. If they find they're about to fill one hold with cases that all have the 'Extra Heavy' labels on them, they'll mention it.
On some flights popular with familes, we can maybe end up with around 20 pushchairs. Most of them weigh well below the average 15kg, and so'll we'll ensure we spread them out across the holds to avoid one area being particularly lighter.
Post a Comment