How To Maintain And Repair Aircraft Instruments?

By Author: Joseph Polizzotto
Total Articles: 18
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Even small quantities of dust and dirt entering data ports of various aircraft instruments are often sufficient to throw a fit at the most inopportune time. When receiving a newly purchased aircraft instrument, have it thoroughly examined and as far as possible, fully tested before installation and take off.

The installation process itself should be handled with care. Tighten the nuts (or screws) too much and you could end up destroying the outer casing which in turn could severely damage the internal parts.

Aircraft instrument repairs are supposed to be handled by approved shop and done under controlled conditions. Every repair shop says so in the brochure. But the reality is usually something else. While these shops are run by properly licensed mechanics and engineers, they in turn, hire assistants who have little or no experience handling delicate aircraft Fuel Flow Instruments.

Often times, damage can occur during a maintenance schedule itself. Surprised? Consider this; an inattentive mechanic’s assistant who drops an instrument just 6 inches, will subject its internal components to almost 2 G’s ...
... of force! This is enough to damage a lot of sensitive instruments especially Gyros. Similarly, careless assistants can result in contaminates or even tiny nuts and screws getting into the internal mechanism of an Aircraft Digital Instruments – imagine what that could do when the plane is being tossed around during a turbulence. It’s a headache you don’t want.

Tips to maintaining aircraft instruments:

1. Do not lubricate fittings on vacuum gyros as it could result in over- tightening of screws and damage the fitting and the back-plate ports.

2. Cover / tape all ports when shipping to reduce possibility of dirt or dust entering the ports or Aircraft Sensors.

3. Gyros should always be allowed to run-down before removing. This is done to prevent damage to the gimbals and ultra-sensitive bearings. Similarly if you need to keep a gyro in storage for more than a month or two, it needs to be "powered-up" and operated for no less than 39 minutes so as to allow the bearings to be adequately lubricated.

4. If you need to check the accuracy of the Manifold Pressure Indicator or Aircraft Fuel Flow Indicator, you should ideally compare it with the Altimeter's baro setting. Also remember, that some altimeters have vibrators in them. These vibrators are installed to reduce friction within in the instrument and thereby enhance accuracy. During maintenance, the mechanic needs to ensure that the vibrator is functioning properly.

5. Whenever the True Airspeed Indicator is taken out for maintenance, the mechanic needs to make sure the capillary tube is intact otherwise; the true airspeed indicator will have to be replaced.

6. It is very important that any instrument like Aircraft Engine Monitoring Systems should be properly tagged before handing over for repairs.

7. Always make sure the connectors on your fuel probes or Oil Temp Probes are clean and shiny.

For more information on Aircraft Instruments, please visit: https://www.jpinstruments.com/