Definition
A precision instrument used to calibrate pressure gauges by applying a known pressure produced by stacking certified weights of specific mass on a piston of known area inside a fluid-filled cylinder. The pressure generated equals the total weight divided by the piston's cross-sectional area, providing a highly accurate reference against which the gauge under test can be compared and adjusted.
Plain English
A test rig that creates a known, exact pressure by placing real metal weights on top of a small piston. Because you know exactly how heavy the weights are and exactly how big the piston is, you know exactly how much pressure is being produced. You then compare a pressure gauge against that known pressure to see if it reads correctly.
Context Anchor
Seen in aircraft maintenance shops when pressure gauges, hydraulic test equipment, or pressure-measuring instruments are being checked for accuracy.
Derivation
Called dead-weight because the pressure source is literally inert metal weights sitting under gravity — no springs, no pumps, no active force. The weight is just there, doing nothing but pressing down. That stillness is what makes it so accurate.
Why Pilots Care
Proper calibration ensures pressure-dependent instruments display accurate altitude and airspeed data, directly affecting flight safety and navigation.
Analogy
Think of a kitchen scale being checked by placing a certified one-kilogram reference weight on it. The dead-weight tester does the same thing for pressure gauges — using known weights to produce a known, trusted pressure.
Intuition Check
Do not read “dead-weight tester” as a tool for testing an aircraft’s weight. Here, “dead weight” means known weights used as the reference for producing an exact pressure.
Example Sentence 1
The instrument shop used a dead-weight tester to calibrate the aircraft's oil pressure gauge before reinstalling it.
Example Sentence 2
Before reinstalling the airspeed indicator, the mechanic verified its response using the dead-weight tester at several known pressure points.