George says to always apply pressure and vacuum at very slow rates. "Also, you've got to be careful not to apply too much vacuum or you can literally suck the diaphragm out of the altimeter.
"You also need to be careful when arranging the equipment not to step on any of the tubing around the aircraft. This will cause a spike in the system, and again, you're trying not to damage the instruments."
Another thing to be aware of is the differences in the instruments that are connected to the system. For instance, the airspeed indicator cannot withstand as much vacuum as the altimeter, so when you apply vacuum to the static ports, you have to apply vacuum to the pitot tube in order to equalize the pressure in the airspeed indicator. "Just remember that the airspeed indicator is also connected to the static port and you need to protect it from any pressure or vacuum you apply to the static port while testing other instruments," says George.
"You can run the airspeed indicator up by itself from the pitot tube, but you've got to do it very slowly and be sure not to go past the limit of the airspeed indicator or you will rip the bellows."
As with any system on an aircraft, you need to make a complete and thorough study of each and every aircraft before beginning your work to understand all the potential consequences of your actions. The pitot-static system may appear basic, but the instrumentation attached to it is sensitive and highly accurate equipment, which you need to have a working knowledge of before applying any pressure or vacuum to the system.
According to George, Banyan trains all of their technicians who work on these systems to review aircraft maintenance manuals, study the regulatory requirements associated with pitot-static testing, and to review all equipment installed on an aircraft prior to working on that aircraft. As well, they require the technicians to use a customized checklist designed for the equipment they are using to test the aircraft, and for the type of aircraft they are testing.
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