Pilot's tip of the week

Descent Tactics

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Subscriber question:

"Descending from cruise altitude, I'm not sure the best time to start down, how quickly I should descend, etc. Is there a rule of thumb, or things I should consider?" - Anonymous

Wally:

“Well, there are a number of factors that you need to consider. If there’s turbulence down low, you want to avoid that as long as possible. On the other hand, you don’t want to stay up too long and have to make a fast descent and perhaps damage passengers’ ears. So if you have a passenger that’s sensitive to the descent, you’re probably going to want to start earlier. If you have passengers that are sensitive to turbulence you may want to start later. It’s a judgment call, of course, and it’s different every day.

You need to think about children in your airplane. Their ears tend not to ‘flex’ as well as our older ears. And of course, you need to think about obviously, the winds, the weather down there, the cooling of your engine – it’s not good to cool the engines very fast. So you need to consider all of these things as you’re approaching your destination to make a decision.

There’s another factor in the descent as well. You know it costs us time and fuel to get to this altitude, so let’s see if we can get some of that back now in the descent. If we do some planning we can simply pick up 5, 10, 15 knots of speed, assuming the weather and flight conditions allow, and get a few minutes back and save a little bit of fuel during our descent.

Typically our ground speeds in the airplanes we fly are around 120 knots. So if we think about losing approximately 1,000 feet every six miles (350 FPM), that’ll give us a good idea when to start our descent. And of course, we have GPS and sectional charts and other aids to tell us our distance from the airport. And a good airman plans to make a nice, smooth descent and recapture any energy they lost on the climb if they can.”

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