Just because something seems reasonable doesn’t mean it is true. It might just mean you want it to be true, as this pilot discovered.

A former boss once warned me that ‘an assumption is the basis of a screw-up’. While I’ve often repeated that maxim to others, it took 5 white-knuckle minutes to teach myself the wisdom of those words.

The weather was ‘severe clear’ that October evening and, with my newly acquired night-flying rating added to my private pilot’s VFR licence, I was looking forward to an hour of circuits to hone my take-off and landing skills. I’d rented a mid-70’s vintage Piper Archer at Buttonville Airport on the northern fringe of Toronto, Canada.

The trouble began innocuously enough during the walk around. The cap on the oil dipstick was screwed on too tight for me to loosen by hand. I flagged down the rental agency’s fuel browser and asked the driver to borrow his pliers. He volunteered instead to take care of the tight cap for me and that’s when I made assumption #1: now that help had arrived, I can continue my walk around. 

So, I was busy checking the fuel for water when I heard the driver unsnapping the 4 cowling latches to access the engine. A few seconds later, he cheerfully informed me he’d unfastened the oil cap and the oil level was fine. I thanked him and heard him drop the engine cowling back into place as I was releasing the rear…