Aircraft Weighing Systems

One of the important factors in the safe and efficient operation of aircraft includes maintaining proper weight and balance of the aircraft at all times. The weight and balance system commonly used by aircraft operators consists of there important elements:

 

 

Any inconsistency in even one of these actions will cause problems in the system. The final loading calculations are useless if either the aircraft has not been accurately weighed or the records are not kept securely.

 

In general, the weight of one person or one piece of luggage is of no importance to the operation of a large commercial jet. Commercial airlines have developed statistical data to estimate the average weight of passengers and baggage loaded on the planes. Statistics are used to determine safe weight loads for each flight and reasonable margins are kept to ensure flight safety.

 

Load sheets

One cannot know exactly how much is the combined weight of all the passengers, luggage, and fuel on an aircraft. However, very good estimates are made. This is the work of the loadmasters. They are responsible for the freight and all load on board. This includes passengers and their baggage. The total weight thus calculated is conveyed to the pilot before each flight.

 

Why accurate weight measuring is important?

Improper loading decreases the efficiency and performance of an aircraft from flying correctly. The speed, acceleration, altitude, maneuverability, rate of climb, etc. all depend on the weight of the aircraft as one of the important factors. Improper loading causes abnormal stresses on aircraft structure and changes its flying characteristics. Wrong data can be a cause of a crash due to improper loading and weight distribution.

 

Type of weighing equipment

An empty aircraft weight can only be determined by weighing it on an accurately calibrated scale. The size of a commercial jet aircraft is quite large and special weighing equipment is necessary to determine its weight.

There are two types of aircraft weighing systems, the Jack type or the Platform type:

 

Jack Type Devices

The Jack-type scales are a reliable means to weigh an aircraft. With this method, the aircraft is lifted on special jacks with electronic load cells which are placed between the jack and the jack pads on the aircraft. The aircraft is raised on the jacks until the wheels are lifted off the floor and the aircraft appears to be in a level position as in flight. The weight is then measured at each load cell as indicated on its control panel. The data from all the cells are collected and by an algorithm, the total weight of the aircraft is determined.

 

In some cases, aircraft are weighed by rolling them onto ramps in which load cells are embedded. This method does not require the aircraft to be jacked up off the ground. However, most commonly aircraft is weighed by jacking the aircraft up and then lowering them onto load cells. Extra care is critical when raising an aircraft on jacks for weighing. If the aircraft has spring-loaded landing gear then the landing gear will slide inward as the aircraft is lifted and the weight is taken off of the wheels. In such a case the aircraft may slip over the jack and tip over.

 

 

For some aircraft, special stress plates are required to be installed before the aircraft is raised with wing jacks to distribute the weight over the jack pad. It is important to follow the aircraft manufacturer’s recommendations whenever an aircraft is jacked up. When using two wing jacks, they must be raised simultaneously; otherwise, there is a risk of aircraft slipping off the jacks.  As the jacks are raised, it is necessary to have safety collars screwed down against the jacks, to avoid the aircraft from slipping off, if one of the jacks fails due to low hydraulic pressure.

 

Platform Scales

Jacking an aircraft off the ground from all load points can be inconvenient, as well as a safety risk, which some operators would prefer to avoid by opting for more expensive but simpler-to-use equipment. They use platform scales. These weighing platform scales typically take less than half the time to weigh an aircraft as compared to load cells.

 

Platform scales or ramp wheel scales are designed in a low profile, which is easy to handle, quite safe, and reliable to use. The aircraft is pushed or towed on these scale pads which remain at ground level. Each scale can measure up to a load of 60,000 pounds, which is quite sufficient to weigh in the largest of aircraft.

 

Platform scales are designed to weigh such large items, and the scales send the weight readings to remote computers which calculate the total weight of the aircraft.

 

Intelligent Scales

The intelligent platform weighing system is a wireless weighing system based on the Internet of Things. The weight of the aircraft is measured by three weighting platforms with sensors under three wheels. The voltage signals of the sensors are converted into digital signals through the digital modules and uploaded to the server through the 4G wireless module. The computer reads the measurement data of the sensors in real-time by logging in to the server program, then calculates the total weight of the aircraft. It also calculates the position of the center of gravity of the aircraft by a mathematical formula.

 

Protection of weighing scales

All scales for aviation use, manual or electronic, must be stored in a safe place when not in use and protected from rough weather conditions. They must be checked periodically for accuracy as per their manufacture’s recommendations. The maximum period between calibration is normally one year, however, this period may be reduced depending on their usage. Scales in daily use may require a shorter testing interval to ensure their accuracy.

 

Why calibration is important?

All scales for aviation use, manual or electronic, must be checked periodically for accuracy. The maximum recognized period between calibration checks is 12 months; however, this period may be reduced by an airworthiness authority dependent on the conditions of use. Scales in daily use may require a shorter interval and/or testing to determine the continued accuracy of the unit. Scales should be returned to the manufacturer for proper calibration and testing.

 

Calibration is extremely important as the incorrect weighing of aircraft can have serious safety implications. If the loadmaster determines the weight of the aircraft which is incorrect, the aircraft may be overloaded and unbalanced. This can have serious safety issues if the pilot attempts to fly the aircraft with incorrect weight information.

 

 e2b calibration can calibrate your aircraft weighing equipment to industry standards. We perform calibration procedures in our ISO 17025: 2017 accredited facility. Please contact e2b calibration for more information.

 

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