When Instruments Let Ya Down…
Below we’ll take a look at a few different types of instrument failures. Some you should recognize from just a still image, others you will have to play a short video to get a sense of what instrument has failed. The videos are short intentionally. We want your eyes to be trained to detect the lying little gauge as quickly as possible.
Attitude Indicator Failure
Cross-referencing the Attitude Indicator with the Turn Coordinator, DG, and Compass shows us that the Attitude Indicator has failed. Given that we do not see a GYRO flag on the instrument, it is either not equipped with one, or there is still vacuum suction going to the instrument, but it has failed internally.
The inner workings of your VSI are pretty delicate. We’re all familiar with how the VSI can sometimes read 100fpm climb on the ground or 100fpm descent, and that is actually legal to fly with under IFR. However, these delicate little instruments can break and be quite distracting. When it does fail, cover it up and go back to pitch and power flying!
Turn Coordinator Failure
Here the Attitude Indicator, DG, and Compass all indicate a turn while the Turn Coordinator does not. The Turn Coordinator has failed to Coordinate and should be covered up!
When DG’s fail, either due to internal failure or vacuum failure, they typically freeze in position. Changing the heading of the aircraft as evidenced by the Compass, Attitude Indicator, and Turn Coordinator show no change on the DG, thus the DG has failed and should be covered up.
Airspeed Failure / Iced up Pitot Tube (inlet and drain plugged)
This picture here could be from ice building around the pitot tube, trapping the air pressure inside the static lines and giving you the same indication regardless of changes in speed. We know that our Cessna 172 cannot climb at 800fpm, at 100 knots at 2,200rpm, thus something is wrong with the picture we are seeing!
Now that you’ve had a look at some of the failure modes of instruments and what it will look like when they do fail, let’s put that to use in some scenarios and test your skills in the next TOPIC!