C172 preflight checklist failure!

It was a normal Saturday morning at the start of fall. The ceilings were high, the winds were calm, and I decided it was the perfect opportunity to get in a bit of pattern work before I had a two week break from flying to take a business trip. However, the general aviation gods were not smiling on me today … what seemed like a simple mission in very low risk conditions could have gone very badly wrong for me today.

After arriving at my home airport, I picked up the keys to a trusty Cessna 172M – the very same bird I made my first solo flight in – and walked out onto the ramp to begin my pre-flight inspection. I usually take my time over this, having had the importance of the check drummed into me by my very experienced and risk savvy flight instructor.

About 10 minutes into the inspection, and nearing the end of the C172 preflight checklist, I crouched down to take a look at the main gear assembly on the pilot’s side. The tire was OK, and there was no sign of any fluid leaks. I peered down and around the brake disc, trying to check the condition of the pads. Here is what I saw:

c172 brake caliper assembly
c172 brake caliper assembly

Can you see the problem? Take a close look. There is one pad visible immediately below the disc in the above image, but no sign of the other!

Initially, I thought that one of the brake pads was missing. But on closer inspection, something else was wrong. Part of the caliper assembly was loose, and had swung away from its normal position. Look closely just underneath the tire in the above image, you’ll see a part of the assembly rotated around from its normal position (around the bolt head you can just make out towards the bottom of the image).

It turns out that one of the two bolt holding this part in place had broken right in two!

c172 brake caliper broken bolt
broken bolt from brake assembly

Now I’m no mechanic, so I don’t really know how serious an issue this could have been, but I’m assuming it could have been BAD. The loose part was rubbing against the wall of the tire, and who knows how effective the brake action would have been. Perhaps the second bolt would have broken under increased load, leading to no braking action at all on the left main! I’m assuming that the outcomes of this could have been very dangerous – everything from a burst tire to a runway excursion caused by uneven braking. It could have been nasty.

Obviously, I grounded the plane. I decided not to fly today, despite other planes being available. For some reason, the general aviation gods were not smiling down on me today! I know this isn’t rational, but I decided to call it a day anyway.

The moral of this story is of course that you must always do a thorough preflight inspection guided by the appropriate checklist! Pay close attention, and don’t be tempted to rush through it. It is an essential tool in every pilot’s ongoing responsibility for risk management.