Descent Tactics

Source: Wally Moran

Bob Martens:

"How about now, you know when do you start down? When is the most efficient and the most professional way to begin our descent and start our transition from the cruise to the arrival phase?"

Wally:

"Well there are a number of factors, Bob that you need to consider. If there's turbulence down below, 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.

Bob, I'd like to go back and talk about another factor in the descent as well. You know it costs us time and fuel to get 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, that'll give us a good idea when to start our descent. And of course we have GPS and DMEs 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.

Now as we get ready to call the tower again just as we did prior to takeoff, we need to pause just a moment or two and think about what we're going to tell that fellow. If we've been doing our job, we already know what the ATIS is. We know what runway we are expecting to land on. We can pretty much guess what kind of a clearance he's going to give us, either a downwind or a straight-in or a left or right base.

Here again, Bob, the tower may give you a clearance or a request that is not the most efficient. And there's nothing wrong with asking them or suggesting to them something that would work better perhaps for both of you. Remember you're still the Pilot in Command and they want to get you on the ground as painlessly as they can. If you have a good idea, feel free to share it with them.

And of course we want to get all our checklists done before we enter the traffic pattern. Then all we need to do is fly the airplane and watch for other traffic. If we wait to do the checklist, it's very easy to get distracted and miss items once we're in the pattern."