Double-check all instrumentation test results before reporting a technical fault.
Instruments that measure altitude by determining the relative air pressure, such as altimeters and GPS (global positioning system) components, can be tested using airfield-location, low-altitude evaluations and laboratory bench testing. They measure the functionality and accuracy of instrumentation to ensure airplane flight safety. Pressure-altitude accuracy measurements, altitude-vibration burn-in cycling and electrical stressing are three widely-used, highly-specialized examples. The same principles of testing are used for diverse applications including weather prediction and manufacturing-scale process control.
Instructions
1. Perform a low-altitude test flight. Measure the altitude using an external parameter such as a calibrated GPS located in a fixed signal box. Set the altimeter to the current altimeter setting. Record the result. Compare the result with the known altitude from the GPS. It should correspond to within 75 feet of your true elevation, according to the Fort Meade Flying Activity (FMFA).
2. Perform a bench test. Aim to achieve instrumentation compliance with the Federal Aviation Administration (FAA) or European Aviation Safety Agency (EASA) standards. Compare the altitude at a specified laboratory pressure to a NIST-traceable pressure standard. The NIST pressure standard is the most accurate of all and is called the mercury manometer. It has an upper limit of 350 kPa (kilo Pascals), as described by NIST's Physical Measurement Laboratory.
3. Run an automated altitude-vibration burn-in cycle test. This simulation of operating conditions requires specialist equipment and engineers skilled in the art of vibration testing. Wear safety goggles and ear protectors. Increase the pressure from an agreed minimum value to a maximum value over a period of eight hours to achieve accurate results, according to Trans-Cal Industries.
4. Conduct electrical stressing for all possible outputs. Use a simulator. Verify the performance of the altimeter, or associated instrumentation such as GPS technology. Record the maximum electrical operating characteristics.
5. Measure the Minimum En-route Altitude (MEA) using an altimeter and on-site calibrated GPS. MEA is the lowest recorded altitude meeting obstacle clearance requirements. It assures acceptable navigational signal coverage. In transition areas, the altitude should not exceed 300 feet. In control areas, the altitude should not exceed 500 feet. If these measurements correspond to on-ground tracking data, the altimeter is fully functional.
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