It maybe necessary to prepare special devices that will aid in taking measurements and leveling specific types of aircraft. To measure such data as lengths, angles, and densities, weight and balance personnel require accessories such as levels, plumb bobs, measuring tapes, chalk lines, and hydrometers. Some types of aircraft require special equipment. The equipment will be assembled into a specific type of aircraft kit.

SPIRIT LEVEL. At least one spirit level is required for leveling most aircraft. Two levels are generally recommended. Use one 24-inch level for spanning distances between leveling lugs. Use a 6-inch level for use in places where sufficient space is not available for seating a 24-inch level. The levels should be a machinists bench type of first-class quality.

LEVELING BARS. Several leveling bars of varying lengths are needed for spanning the distances between leveling lugs. One set of bars usually comes with the weighing kit normally maintained by each Naval Aviation Depot (NADEP).

PLUMB BOBS. Plumb bobs are used to project points on the aircraft onto the floor for measuring dimensions in a level plane. Each pIumb bob should have a slot in the head so that excess string can be wound around the neck. Plumb bobs are normally included in the weighing kit.

STEEL TAPES. Use a steel tape 600 inches in length and graduated in inches and tenths of inches. All weighing dimensions must be read to one-tenth of an inch, and are frequently read to one-hundredth of an inch. Using this type of tape reduces the possibility y of errors associated with converting common fractions to decimals. These tapes are usually found in the weighing kit.

CHALK LINE. This is a string, covered with chalk, that is used to mark a straight chalked line on the hangar floor. It is used between the vertical projections of specified jig points. The string should be sturdy and hard finished. It usually accompanies the weighing kit. 

HYDROMETERS.- Use a hydrometer with a calibration range from 5.5 to 7.0 pounds per US gallon for determining the density of fuel. A transparent container for holding fuel samples, a pipette at least 12 inches long, or some other similar device for withdrawing samples from the tank, is necessary for use with the hydrometer. You must take care not to damage the glassware. To determine the density of a fuel sample, you should carefully place the hydrometer into the fluid within the transparent container. The hydrometer must not touch the container when you are reading the density, and you should take the reading at the lowest fuel point. 

NOTE: The hydrometer is used to determine fuel density for full fuel weighing. Since full fuel weighing is permitted only with specific NAVAIR (AIR-5222) approval, a hydrometer will not normally be apart of the weighing kit.