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Nav-Aids Ltd of Montreal,

manufactures Pitot Static Test Equipment for all segments of the aviation industry

Sample Pitot Static Test Adaptor

Pitot Static System

Pitot/Static and Altimeter Certification and Re-Certification is required by Canadian Aviation Regulations (CAR) 625 Appendix C.

CAR 625 appendix C requires that any aircraft that are operated under Instrument Flight Rules (IFR) or under Visual Flight Rules (VFR) in Class “B” airspace must have the altimetry devices and their associated systems tested every 24 months.

Airspeed Errors due to blockages

Airspeed errors can occur if either the Pitot tube or the Static vent become blocked.

Pitot tube can become blocked on the ground, either by bugs, or ice. In this event the ASI will read zero. The airspeed will not increase as it should during the takeoff.

In Flight Blockage of Pitot - When this first happens, if the aircraft is in steady flight the pilot will not realize there is a problem because the ice simply seals the pressure inside the Expandable Capsule

When the aircraft descends for landing however the pressure inside the capsule will remain constant, whether the aircraft accelerates, or decelerates.

As the aircraft descends the static pressure will increase. This will squeeze the expandable capsule. Thus, the indicated airspeed will decrease as the aircraft descends regardless of the actual airspeed.

The opposite would happen if the aircraft climbed.

In Flight Blockage of Static Vent - As long as the aircraft remains at the same altitude the Airspeed indicator works normally since the correct static pressure is sealed in the case.

When the aircraft descends the static pressure in the case will be lower than it should be. Thus, the airspeed will begin to read progressively higher as the aircraft descends.

If the aircraft climbs the airspeed will begin to read progressively lower.

What happens during a pitot/static test?

A test system is connected to the Pitot and Static systems on the aircraft to simulate the pressures that the instruments would be subjected to during flight. The test system allows the technician to simulate a different airspeed and elevation on the aircraft systems without leaving the hangar. The Pitot system, or the air pressure that identifies airspeed, is tested first, and then the static pressure system is tested next. The system should not leak during this test. If the system does leak, the leak must be identified and then repaired.

During this time all of the required checks of the altimeter are conducted to ensure that the unit is functioning properly and indicating accurately. A very sensitive pressure gauge is connected inline with the system for this purpose.

While all this is going on, a third test set checks the output of the Transponder and encoder systems. The transponder is checked for power output and alignment, among other things, to ensure that it meets the requirements of the regulations. The encoder is checked for proper output and is compared to the altimeter to ensure that its output is correct.

Link to technical article on Pitot