Aviation Logistics Knowledge Lecture – Airline Overcharged Me for Freight

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Aviation Logistics Knowledge Lecture – Airline Overcharged Me for Freight

Hello everyone, it’s our monthly lecture time again. As soon as I see this title, some friends may say whether I am starting to lie to people. Actually no, this is an example, and I want to share it with you. Recently, I received feedback from my friends that some airlines will charge more for shipping. It is also suspected that there is a chain of contempt in the airlift industry. Hahaha, let’s talk about it today.

The thing is like this, there is a small friend who has tickets and asks the price, and later learns that the airline company accepts the goods of the same destination. 4 times. So ask me. I find it strange that it is normal for the price to vary, but if an agent’s usual performance is not too bad, the price should not be too far off.

So I went to ask for details. The details of this shipment are a single piece of 6 tons, size 500x135x120cm. It turned out to be the case, and as soon as I heard the size, I knew where the problem was. Because this ticket is too long, it belongs to the odd size. And for such a size, a 20-foot board must be installed.

Having said that, experienced friends may know the problem. Generally, the ULD of a cargo plane MD is PMC, so let’s review the size of the PMC. It is a 96-inch board with a size of 318x244cm. So can this shipment hit a PMC? Obviously not. Because the longest side of PMC is 318cm, and the length of this shipment is 5 meters, which is almost the length of two PMC boards. Therefore, ordinary boards cannot hold this ticket.

Due to the size of the cargo, it must be loaded on a 20-foot board. What is a 20-foot board? The representative of the 20-foot board is the so-called PGA board. A typical PGA board length is 605.8x244cm.


In the picture above, let’s ignore the height first. You can see that this shipment can be placed on a PGA, right? But there is still no explanation why the freight is more expensive because since it can be put on it, there should be no problem.

Being able to ask a friend like this is very clear. This problem is related to the problem of aircraft loading. Let’s recall, what is the loading of the general MD? If you can’t remember it, you can go back to my previous articles, and I will simply review them here. The loading of MD, if all of them are PMC, is generally like this (the soul painter is here again):



Everyone has an impression of this ULD combination, right? That is, the long side is arranged vertically, and the short side is arranged horizontally. But if you want to install PGA, how should it be loaded? Don’t worry, we once again invited the soul painter to appear:



Let’s see, if it is a PGA, is the long side of a PGA larger than the long side of a PMC? So what is the effect of occupying more space on the aircraft? The impact can be great.

First of all, a PGA is equivalent to occupying the position of two PMCs, but this PGA still has space for other goods, right? At this time, the person in charge of planning needs to see what the maximum weight of the PGA is. If it does not exceed the weight limit, it is theoretically possible to continue to load other goods. But he couldn’t make a decision when he received bookings. Because to see if there is enough heavy cargo on this flight to match him. Just imagine, if I ignore this factor and directly install the PGA, and then the PGA on the other side, it will be a bubble. So what can go wrong? Will the plane be heavier and lighter during a flight? Is this dangerous? It will also speed up fuel consumption. Therefore, the PGAs on both sides must be about the same weight for the aircraft to remain balanced.

Therefore, here the airline has to consider whether the flight has enough heavy cargo to balance. If it is not enough, it is very likely that the consignment will not move. Moreover, if this piece of PGA is overweight, even if there is room, it cannot continue to put other goods. It’s like having space but not being able to use it. This space is wasted. Therefore, it is completely understandable to charge a higher shipping fee for this shipment. It is by no means that the airline has a contempt chain to deliberately overcharge the freight.

Of course, generally speaking, the weight limit of a PGA will be about 11 tons, after all, it is the position of two PMCs. In theory, as long as the goods on the other side can reach a balance with this side, it will be fine. But in addition to the weight limit of a single ULD, there are many places in the aircraft that need to be considered for trim. For example, if this PGA is placed in different positions on the aircraft, there will be different weight limits. We have explained this before, the position of the nose is always impossible. The weight limit of the ULD is the same as the weight limit of the middle position of the aircraft. The heaviest weight must be placed in the middle, that is, near the wing of the aircraft (see the CG of the plane – aka Center Gravity: where is the center of gravity). At the same time, when trimming, there is also an important consideration of the joint limit, that is, whether the weights of MD and LD match. Therefore, it is not so simple to decide. The safety of aircraft operation is first and foremost, and we must fully consider all possible situations.

Some friends may ask if the PGA is placed horizontally, is it not necessary to consider the balance of the left and right sides? This thinking is very good, know how to try to find a solution. However, in fact, it is impossible. why? First of all, the PGA is 6 meters long, and the aircraft cabin is not that wide. Second, each ULD combination on the aircraft has a corresponding buckle, and currently, there is no plate buckle for the PGA. This means that even if the aircraft cabin is large enough for the PGA to be placed horizontally, the ULD cannot be fixed after it is placed. This is very dangerous.

In addition, the size of the door of the aircraft is limited. Generally, our PGA passes through the door obliquely, and then slowly adjusts its position until the long side of the PGA and the aircraft remain longitudinally aligned. After the PGA enters the hatch at an angle, the horizontal position cannot be adjusted. Let’s take a look at the MD picture of a 747-8F freighter first, and we may have a more intuitive feeling.

See the little wheels on the floor? This is to facilitate the adjustment of its position through electric control after the ULD enters the cabin. The other silver pits are the plate buckles. It can be seen that these plate buckles are fixed and cannot be moved. Therefore, the PGA cannot be placed horizontally.

Then let’s take a look at the door size of a 777-200F. The one on the picture that says Main deck cargo door is the size of the MD’s hatch. It can be seen that the minimum height is about 3 meters, and the minimum width is about 3.7 meters. And such size requires a PGA to enter the cabin obliquely. The long side of a PMC is 318cm, so it can be pushed in naturally. But the PGA will not work.


So speaking of this, everyone should know why these odd-sized goods are more expensive than ordinary goods, right? This is not to say that the airline will deliberately overcharge you for shipping, but it does take up a lot of space.

Alright, that’s it for this issue, see you next time.

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