This testset is used to leakcheck the elevator feel system, or keep air pressure on the system allowing a functional test of the elevator feel computer.
The elevator feel system is a feedback system to give the pilot feeling over his elevator steering.
Because the flight controls are powered, the elevator just follows the control collumn when it moves forward and aft but with the incorperation of the elevator feel system the flight crew feels that the control collumn requires more force to move as the airspeed increases.
The elevator feel system in the 737 has it's own dedicated pitot tubes. Because the elevator feel system only needs airspeed information and no altitude information the probe only senses the pitot pressure and not static pressure. These pitot probes are fitted on the vertical stabiliser.
A full system test would incorporate the use of the pitot static testset to simulate a specific airspeed and then use a force meter on the control collumn to verify that the values are all within the set limits for this system but for we will only carry out a leak check of the system.
We have a new pitot static testset with all kind of connections, hoses and probe adapters.
Unfortunately this equipment is in use for the time being so we resort to using the old test equipment.
So now we get started and connect the regulated pressure source to the probes with hoses and clamps and tape off the drain ports with high visibility tape.
The drain holes should drain moisture out of the probes so that it doesn't get into the systems.
If water does get into the systems it travels to the lowest point it encouters at wich point drain tubes are fitted. It are these drain points which we will connect the pressure gauges to.
We connect the testset to a air pressure source so that we can put the 5 psi test pressure onto the system.
We fully close the regulator valve, select the master valve open and carefully increase the pressure.
When the pressure reaches 5 psi we shall close the master valve and start the timer. The pressure must stay within set limits for a two minute period.
The pressure after the two minutes is within limits and the system passed the leakcheck.
We release the pressure from the system and disconnect all the equipment.