New weight and balance information is regularly required for most all aircraft; small or large. Installation or removal of equipment, after repairs and modifications, or a frequent requirement of the aircraft or operators maintenance program, requires that the most accurate weight and balance data is available.
Weighing general aviation (GA) aircraft, helicopters, turboprops, corporate jets, or transport category airliners can be accomplished in two ways: top of jack load cells and platform scales. Equipment selection is dependent on the operator’s needs and or equipment currently on hand, as well as the airframe manufacturer’s recommendations.
Top of jack load cells, as the name implies, can be used on top of the current wing jacks or can be used under axle for larger jets. Platforms are very useful for small shops that do not have jacks for every type of aircraft. All you need is the ability to pull the aircraft onto the platforms and take your weight readings.
Top of jack systems:
The standard aircraft scale is a top of jack, cell-based scale, where each jack point receives a cell-based transducer on the top of the jack. This system’s advantage is, it is very easy to use and level the aircraft during the weighing operation. The system is easy to transport, light weight, and easy to set up.
The operator must have a jack capable of receiving and mounting the cell. Check your jack ram tops for the 1-inch mounting hole; if you do not have the hole, adapters can be provided to assist in the interface required to mount the cells. Cells come in many weight ranges and are dependent on the weight required per point to accomplish the weighing and receiving the actual jack point type.
Platforms are available in many weight ranges and sizes, these systems either use ramps or the aircraft can be jacked and lowered onto the platforms during regular maintenance. Platforms are easy to use and are a choice for many shops that do not have jacks for the many types of aircraft to be serviced.
The limiting factors for platforms are the weight range and the tire size, some aircraft have large tires and the platform may be too small for the specific aircraft tire. Always use the right size scale and platform for the aircraft type and weighing job you’re doing.
Both types of scales feature new technologies using digital indication. Mechanical or analog meter scales have mostly been replaced with the new digital indicators. These indicators are very accurate and easy to use, cranking handles and thumb wheels are a thing of the past, making the weighing job faster to do and giving much higher quality in readings.
Scales are like torque wrenches and you would not use a 100 foot-pound torque wrench to torque a 20 inch-pound nut. Why then would you use a 150,000-pound scale system to weigh a light GA aircraft, turboprop, or helicopter? We see this practice a lot where many shops and or technicians use large scale systems to weigh light aircraft, or they have the wrong size cell top to fit a large jet jack point.
There are many military surplus scale units out there, be careful, many of these units still in use are analog meter movements and may or may not be calibrated correctly. When calibrating scale equipment we always recommend using an aviation-based calibration lab with an Airframe and Powerplant certified technician on staff or returning the unit directly to the manufacturer for calibration. Some units require specific calibration procedures, software access, and or adapters; to complete the calibration properly always audit your provider to ensure that the proper procedures and equipment are being used. Primary National Institute of Science and Technology (NIST) traceable certifications and test equipment are a must.
Safety and use of the equipment is always a big factor. Always follow the aircraft or helicopter manufacturer’s recommendations when jacking and or towing aircraft for weighing.
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