Overhauling an airspeed indicator is not as simple as you would think. A typical overhaul includes all of the following steps:

Total disassembly and inspection.

Determine and correct the cause of failure.

Ultrasonic cleaning of all jewels, pivots, and gears

Reassemble internal components.

Silk-screen dial and/or range mark

Calibrate the unit to manufacturers and/or FAA specifications

Assemble unit into case.

Seal Case.

Verify calibration of final assembly.

Accomplish cosmetic touch-up.

Complete all FAA mandated paperwork and certifications.

The typical time required to overhaul an airspeed indicator can range from 1 hour for a simple unit to over 4 hours for complex units.

Calibration of an airspeed indicator is a complex process. Airspeed is a non-linear function, which must be displayed on a linear dial. There are at minimum seven calibration points that are all interactive with each other.