One important difference between planes and cars is that planes are in the air and require power to stay up there. That sounds obvious, but I've only begun to appreciate exactly what engine failure means to a plane now that I've started engine-out training. And yesterday I had a real world brush with engine failure that has made the importance of that training very clear.
We were in Ken's Cardinal, over Monterey at 11,000 feet when the engine started running rough. Switching the magnetos fixed it for a minute, but it started running rough again soon after and was producing reduced power. We decided it'd be prudent to land the plane immediately. Ken radioed in "rough running engine, request expedited landing" and we were immediately cleared to land on the big runway at Monterey airport. Neither of us trusted the engine to keep running. Fortunately Ken had no trouble making an uneventful landing; if anything, we had too much altitude and power. The nice fire crew was standing by on the ground, a precaution we were glad was unnecessary.
When a plane engine stops you don't fall out of the sky immediately, you glide. But you'll be landing soon. How soon? Very roughly, for a plane similar to ours, for every 1000 feet above the ground you have about 80 seconds and can travel about 1.8 miles. So if our engine had quit entirely we would have had about 13 minutes to fly up to 18 miles before we were on the ground. (Note: rough estimate, read your POH for actual flight performance!) Our engine didn't actually quit, and even if it did we had a lot of altitude and three airports we could have made. The picture looks quite different if you're only 2000 feet above mountains with no airport around.
Once we were on the ground in Monterey I had some foolish idea that we could try to clear the engine problem ourselves, maybe test it in a run-up and continue our three day trip to Florida. Ken is much wiser than I and said "no way until a mechanic checks it". Which reminded me of various horrifying stories of pilots taking off with flaky engines. One of the worst things that can happen to a plane is losing power 500 feet after takeoff; the only option is to land on whatever's straight in front of you and all that fuel on board makes for a big hot fire.
So instead we parked the plane at the friendly Del-Monte Aviation FBO where it sits until Monday for a mechanic to look at it. We rented a car and had a nice lunch with a glass of wine and made alternate travel plans on Delta Airlines. And now I've gotten a gentle practical demonstration of why all this engine-out training is important.