Aircraft used for operations under night and/or instrument flight rules (IFR), shall have their radio and navigation equipment tested, along with airspeed indicators and altimeters, at least once every 24 months.
It is recommended that the airspeed indicators and altimeters of aircraft used solely for operations under visual flight rules (VFR) and limited night flight are tested at least once every 24 months.
ATC Transponders should be tested at least once every 24 months.
Magnetic compasses and gyro compasses shall undergo compass swing when they are believed to show incorrect readings and after maintenance or alterations that could lead to errors in the compass. Other instruments should be tested if there is suspicion that they do not work correctly.
Whether instruments are tested in the aircraft or at the workshop, the use of approved testing equipment which is regularly compared with the approved base standard is required. An aircraft maintenance technician who performs tests on airspeed indicators and altimeters must have undergone special training. If an instrument fails the test, it is considered non-airworthy and shall be sent to a recognised instruments workshop for repairs. Adjustment of the airspeed indicators and altimeters must be carried out in an approved instruments workshop.
The "pitot /static" system shall be leak tested if tubes have been disrupted.

1 Aircraft other than those used in air operations

2 Aircraft used in air operations