Why did the airplane stop check-in 40 minutes early?
On the first day of your vacation, you couldn't resist staying in bed for a while, then you got up, stepped out the door, and prepared to catch the plane at 10 o'clock.
Unfortunately, you encountered traffic congestion. When you rushed to the airport counter gasping for breath, dragging your luggage behind, the plane had already finished boarding.
"Why can't they make an exception even though the plane doesn't take off for another 40 minutes? During the time from check-in closing to the plane taking off, what exactly is the airplane busy with?"
In order to ensure that every flight you take arrives safely, besides preparing basic meals and cleaning the cabin, the staff also need to work efficiently to complete a major task in just 40 minutes - load balancing.
Simply put, the loadmaster needs to undertake "weight management" for each aircraft, accurately calculate data such as actual boarding passengers, luggage, cargo, fuel, etc., and provide a proper "weight distribution" to ensure the aircraft's weight and balance are within safe limits.
A weight and balance sheet of the Turkish airline company AtlasGlobal | Wikimedia Commons.
This is not making a mountain out of a molehill. The probability of accidents caused by improper loading is very low, but once it happens, it could be fatal.
From 1999 to 2014, for every 100,000 flight hours, there were 6 to 7 accidents in general aviation in the United States. Among these accidents related to weight and balance, only 2 to 3 would occur per million flight hours. However, weight and balance-related accidents accounted for 57% of fatalities, while accidents caused by other reasons were only 21% fatal.
The position of the airplane's center of gravity is closely related to maintaining balance. If there is a slight error, it's more than just a simple "tumble."
The increase in weight will make the aircraft take off and land over a longer distance, increasing the risk of deviating from the runway. During flight, it may also be difficult to clear mountains and other terrains along the route due to insufficient climb gradient.
The Dalian air crash that shocked the whole nation in 2002 was caused by arson. A large number of passengers in the rear cabin rushed towards the front cabin in panic, causing a shift in the aircraft's center of gravity, leading to its loss of balance and crashing into the sea, resulting in the death of 112 people.
In order to balance the stability of the aircraft, flight performance, takeoff distance, fuel consumption, and other factors, the loadmaster often finds a relatively perfect position within a safe range, ensuring that the center of gravity is neither too far forward nor too far back.
Under the same conditions, the further back the center of gravity of the aircraft, the better the flight performance and the lower the fuel consumption. However, if it exceeds the safety envelope range, problems such as stalling may occur.
And this precise result requires the loadmaster to have a comprehensive understanding of the characteristics of the aircraft (such as operating empty weight, maximum takeoff weight, maximum zero-fuel weight), as well as the loading situation of this flight, which mostly comes from the data registered during check-in.
If you handle the boarding procedures after the deadline, your "new data" may disrupt the subsequent calculation process, causing some inconvenience to the staff.
Specifically, how do baggage handlers calculate and make arrangements?
During the check-in process, the system does not register the height and weight of each passenger. The load planner will estimate based on the standard weight of 75kg for adults, 38kg for children, and 10kg for infants.
Sometimes, the discounted adult ticket is cheaper than the child ticket, so parents will buy adult tickets for their children. This behavior poses certain safety risks. It is best to proactively explain the situation to the airline or check-in personnel, just in case.
During the off-peak season, the discount for adult ticket prices from airlines may be lower than 50% (children's ticket prices), which creates a certain security loophole. [9] | Stock Photos Creative
Otherwise, you might experience a thrilling moment just like the passengers of Australian Airlines: 87 elementary school students were mistakenly considered as adults during the calculations, which caused the plane to be "nose heavy" during takeoff. If it weren't for the smooth operation of the captain, it would have been a disaster.
After confirming the weight of the passengers, there is also a particular way to arrange seats for each person.
The seating arrangement of passengers will cause a shift in the plane's center of gravity. Loadmasters not only control the seat allocation in advance but also adjust in real-time according to the check-in situation, continuously securing the seats in the front and back rows.
The consequences of not following instructions can be seen from the "tail strike" incident with Changan Airlines flight 9H6007 in 2018. The plane was taxiing on the runway smoothly when suddenly the tail was damaged, prompting an aborted takeoff. Upon investigation, it was found that the reason was a discrepancy between the passenger seat assignments and the cargo manifest provided by the loading crew.
Therefore, if you see the front three rows of seats on the airplane empty but they don't allow you to sit there, don't feel upset. These restrictions are all for your safety considerations.
This is also why you can't just walk around on an airplane like you can on a train, and you need to consult with the flight attendant if you want to change seats. Every move you make affects the balance of the aircraft.
The seat by the window offers an excellent view and is convenient for leaning against the cabin wall to rest, but it's not a seat you can just sit in anytime. | Tuchong Creative
Adjusting the center of gravity sometimes requires the help of "ballast." These ballasts are usually heavy sandbags or lead bars securely fastened in the baggage compartment.
For example, due to the engine being positioned in the rear, the ARJ21 aircraft model operated by Chengdu Airlines is more prone to having its center of gravity shift towards the back. When it is observed that there are fewer passengers on board, the loadmaster will promptly assess the weight and quantity of ballast sandbags needed to be loaded on the aircraft to prevent the center of gravity from exceeding the safe range [13].
When arranging luggage and goods, the same principle applies. Factors such as type, weight, volume, etc., all need to be comprehensively considered.
Now that the "traveling weight situation" is known, the loadmaster will calculate the airplane's fuel reserve based on this.
In fact, the plane we are on has more than one fuel tank, and fuel can even be stored in the wings for the purpose of maintaining balance. The aircraft's fuel system can also transfer fuel between different tanks to help adjust the center of gravity.
The amount of fuel for an airplane depends on various factors such as the distance of the flight, weather conditions, weight, etc. If the waiting time in line for takeoff is too long, the plane may need to return to the apron to refuel.
In short, the load controller reaches a reasonable arrangement through a series of calculations, ensuring that the aircraft is not overloaded while maintaining balance.
This information is printed on the load balance manifest and handed over to the ground department. The ground handling personnel will then load the cargo, mail, and passengers' luggage onto the aircraft according to the instructions.
"From checking in at the airport to the departure of the plane, the airport staff can be said to have considered everything thoroughly. Everything is for flight safety. Therefore, next time when in a rush to catch a flight, it's best to leave home early and peacefully arrive at the destination, waiting an extra 40 minutes isn't a big deal."
Reference/References
Chen, H. R. (2023). Research on performance-based aircraft load balancing. Civil Aviation Journal, 81-84+92.
美国交通部。 （2024）。 美国通用航空安全数据。
道格拉斯·D·博伊德（2016年）关于超出飞机重量/重心限制的一般航空事故。
China News Network. (2002). 5.7 Airline Crash: The last moments of the arsonist and how the cause of the crash was determined.
Civil Aviation Network of China (2020). Aviation Popular Science: Why can't you sit in empty seats on airplanes?
Duan Huangke & Zhang Li. (2023). Research on the balance risk of aircraft cabin loading. Journal of Civil Aviation Flight University of China (01), 41-46+50.
Civil Aviation Administration of China. (2019). Regulations on Aircraft Weight and Balance Control.
[8] Civil Aviation Administration of China. (2020). Aviation FAQ: Passenger Travel Notes (Carriage Edition).
[9] Wu Tao. (2014). Load Balance - The Weight of Life That Cannot Be Lost. Air Cargo Business, 11, 20-22.
[10] China Daily website. (2014). Mistakenly counting 87 children as adult weight, an aircraft of Qantas Airways took off unbalanced.
[11] Civil Aviation Report of China. (2017). How are seats on airplanes allocated?
[12]U.S. Department of Transportation. (2016). Weight & Balance Handbook (FAA-H-8083-1B).
[13] China Civil Aviation Network. (2023). The small cargo in the cargo hold: safety matters.
Civil Aviation Administration of China. (1996). China Civil Aviation Cargo Domestic Transport Regulations.
[15] Goraj, Z. & Zakrzewski, P. (2005). Aircraft fuel systems and their influence on stability margin.
[16]Sharma, S., Singh, P., Sinha, R., & Kaurase, K. P. (2015). Review of aircraft fuel system. IJARIIE, 1(1), 6.
[17] Civil Aviation Network of China. (2019). Authoritative Popular Science | China United Airlines re-refueling event: in line with operational procedures.
Article: Lin Ke
WeChat editor: Yumy
Photo editing: Lin Ke
Content Editing: Lazy Sheep
Review edit: Strange and wonderful.