What Not To Do During A Pitot Static Ramp Test

May 2015

The pitot static system is required to be tested every two years. This can be done on the aircraft with test equipment or the units can be removed and sent into an authorized repair station, like Duncan Aviation.

Many of the pitot static units we receive at Duncan Aviation for repair are damaged during the ramp test most often because proper care procedures were not followed. Here are the four most common reasons cited for a damaged altimeter or airspeed indicator during a ramp test.

  1. Test equipment was not hooked up correctly. Pay attention and connect the hoses to the correct port. They are not interchangeable. If a static port tube is connected to the pitot port, it could damage the capsule, which is the heart of an altimeter or airspeed indicator. The capsule expands and contracts in reaction to the change of air pressure around it. If too much or incorrect pressure is applied, that can damage the capsule and make the unit inaccurate.
  2. No air speed pressure applied. After the test equipment is connected properly and before you begin to run up the altitude, you must also have air speed pressure applied. We suggest having at least 100 nm. If you don't have this applied, you could damage the pitot capsule.
  3. Too much air speed pressure applied too quickly. When beginning the ramp test, do not open the valve wide open all at once. Allow the pressure to gradually build. If a blast of air is applied too quickly, the shock on the capsules can crush, crinkle or completely destroy them, requiring the unit to be removed and sent to us for repair.
  4. Air speed pressure released too quickly. Once the test has been completed and you have taken the pressure up to altitude, don't just unhook equipment and suddenly remove pressure from the ports. This could cause the same damage as providing too much pressure too quickly, just in reverse. It may also cause damage to other moving parts at the same time, such as the pivots, jewels or gears on the gear shafts inside the units.