Aviation Logistics Knowledge Lecture – Aircraft Weight and Balance

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Aviation Logistics Knowledge Lecture – Aircraft Weight and Balance

Hello everyone, it’s time for a new lecture on aviation logistics. Let’s talk about the balance of the aircraft in this issue. Doing balance, commonly known as Weight & Balance, is also called Trim in the industry. I’m sure everyone has heard of it. Every time the plane takes off, it must be balanced before it can take off smoothly, otherwise the tower will not let the plane take off, and it is very dangerous to fly without a balance. Colleagues who install machines at the bottom of the machine also need to hold the installation list after the balance is completed to install the machine.


I haven’t done balancing myself, but I know the basics of aircraft balancing. Let me share with you what I know.


The person who usually does the balance is called the Load Master. They will send a final manifest to the load master after all the ULDs are loaded. The manifest will show what ULDs have been laid and the weight of each ULD. Of course, this also includes loose bucket cargo. The cargo in the loose bucket is placed at the rear of the lower warehouse of the aircraft. The compartment that does not use ULD is usually called the loose warehouse. The load master will assign where each ULD should be on the aircraft based on the weight of each ULD and the current balance point of the aircraft.


Don’t think that the balance point of the aircraft is the same, even if it is the same type of aircraft, the balance point may be different according to its service years, weather and other factors. So it’s a matter of balance every time the plane takes off.


To give a simple example, the engines of many aircraft are in the middle, so the heavy ULDs are required to be placed in the middle, and the light ULDs are placed at the ends of the head and tail, so that there will be no top-heavy or top-heavy. . And each ULD will have a limited weight, each position will have a limited weight, and the upper and lower warehouses will also have a combined weight limit. So it takes time to do this calculation well. Of course, most of the balancing is done by computers now, and there are also cases where manual balancing is done, but doing it manually will have a higher chance of making mistakes, so in many cases, it is handed over to the computer, and then manually fine-tuned. After it’s done, the captain will also look at it, and if he thinks there is no problem, he will sign and agree to release.


So sometimes, we hear that the goods are pulled because they are overweight, which is the reason. The balance cannot be achieved. Putting this ULD or this ticket on it will exceed the weight limit. Let’s take a look at what a balanced manual sheet looks like.

Load and Trim Sheet

Load and Trim Sheet


We know that there are many factors that affect payload. Usually, we only know how many tons a plane can hold at most. In fact, when you are really doing balancing, the data you need to look at is not just the simple payload, but even this so-called payload cannot be used as the data that you need to know for professional balancing. Let’s see what data to look at now.


MTOW: Maximum Take Off Weight – Maximum Take Off Weight

MLW: Maximum Landing Weight – Maximum landing weight

MZFW: Maximum Zero Fuel Weight – Maximum Zero Fuel Weight

DOW: Dry Operating Weight – Body Weight+Crew+Pantry

DEAD LOAD: Baggage weight + Cargo weight + Mail weight (that is, the total weight of all cargo and mail bags)


Let’s explain them one by one. We know that the aircraft itself has weight, and there are weight restrictions on ULDs. But you may not know that there are restrictions on the above data. The maximum take-off and landing weight is well understood, which is the weight that the entire aircraft cannot exceed when taking off and landing. During the flight, the aircraft will consume aviation fuel, but it will not consume the captain, nor will it lose the cargo, so before landing, the weight lost will only be aviation fuel. Then I deduct the consumed aviation fuel, and I can get the weight of the entire plane when it landed. And this weight cannot exceed the maximum landing weight. The maximum fuel-free weight of MZFW is the fundamental indicator for judging the payload. What he means is: the weight of the aircraft + DEAD LOAD. Then we add ZFW to the amount that needs to be refueled, and we can get the take-off weight. Then use this number to compare the maximum take-off weight to know whether it exceeds the MTOW value. Therefore, the fuel-free weight is the weight excluding jet fuel + cargo luggage.


If you are a little confused, you can take a look at the picture below. The picture is very intuitive to explain the connection between the various data.

Load and Trim Sheet

Load and Trim Sheet


So there are many factors to consider when balancing. It is not simply to add up the weight of all the goods.


After talking about weight, let’s take a look at what else to consider about balance. We know that when the plane takes off and lands, it is not parallel to the ground, but forms an angle with the ground plane. As shown below (well, you can laugh at my artwork).

The angle between the aircraft and the ground

The angle between the aircraft and the ground


This angle is also specified and cannot exceed a certain angle range. Example: What happens if the angle between the tail and the ground is too large during takeoff? Scrape to the tail. Then the tail will keep scraping the ground and taxiing. If you say this, you may not feel it. Then imagine, if everyone’s car keeps rubbing against the ground while driving, will everyone feel distressed? When taking off, if the angle is too large, the balance is not done well, this indicator is not up to standard, and the tail of the aircraft must be in close contact with the ground. The balance must be redone. Fortunately, the balance of computers can take this into account now, so generally this situation does not occur.


Finally, taking into account all the data and the circumstances that need to be considered, combined with factors such as the weather, route, and route weather at the origin and destination on the day of the flight, it is possible to estimate the amount of jet fuel that needs to be used. Then the load of the plane is basically out.


From the airline’s point of view, doing balance does not mean it’s done, there are other things to look at. Among them, Underload is a very important indicator. What he meant was simply “surplus karma”. This indicator directly shows the loading situation of this flight. For example, the maximum load of a flight is 100T, and the current Underload is 500kg. Then this data is very beautiful. Because the remaining payload is only 500kg, that is, 99.5T has been used. The loading rate has reached 99.5%. The Allowed Traffic Load has been utilized to the greatest extent. At the same time, this underload will also increase if the range requires the aircraft to add more fuel. This figure will also have guiding significance for pulling goods. So it’s really not easy to do a flight balance. Like our Load Master! I also hope that everyone can better understand the concept of aircraft balance, so as to support the work of airlines more.


Hope the above basic knowledge can help you. The development and growth of the airlift industry is inseparable from everyone, and everyone understands the truth, in turn, can positively promote the development of the industry. The two are dialectical and complementary. As long as we have the right concept, we can all contribute to the airlift industry.


Finally, let’s lay the foundation together and play our brilliance in the airlift industry.


That’s it for this issue, see you next issue. Good luck to everyone!

NB: Karron is the owner of the “NatureCalls” Wechat Official Account.

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