How High Should I Be When I Turn Final?
Hey Mom,
Got a question for you about flying the traffic pattern. It seems like there’s a gauge for just about everything-when to turn crosswind, how high to fly downwind, when to reduce power, when to add flaps, when to turn base, except I don’t know how high I should be when I turn final. I feel like if I had a number to plan for, it would help me to not be high sometimes and low the rest of the time. It always gets worked out somehow, but if I knew what altitude I should turn final at, it would help a lot and I might not always have to make so many adjustments on final.
Thanks,
How High Shall I Fly?
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Hidy Ho, How High-
High enough to glide safely to the runway, of course! Short of that, the short answer is that there isn’t one. The correct altitude depends on a multitude of variables, a plethora of particulars, scads of changeable factors. How so? Consider the conditions that will cause your glide distance to vary. Density altitude (which varies by pressure and temperature, of course), headwind component on final or complete lack thereof, power and flap settings, airspeed, and the size of your traffic pattern for starters, not to mention that different winged wonders will demonstrate variations in glide performance that could make your head spin! To be a little more specific;
Higher temperature and/or lower pressure will make the air less dense. We refer to this as high density altitude, meaning that the air is as dense as it would be if we were actually at a higher altitude on a standard day. High density altitude will decrease aircraft performance. You aren’t going to glide as far. Good to know. And have you ever noticed how on a still day, planes seem to land longer and go around more frequently? We’re used to that headwind decreasing our ground speed on final, giving us time to lose more altitude while inbound. The greater the headwind component, the more likely we are to wind up low, adding power to drag it in over the threshold.
Variations in power setting will also play havoc with your glide distance, as will changes in the size of your traffic pattern. Flying a little farther out on downwind causes you to lose more altitude AND fly a longer final back inbound, decreasing your altitude still farther and once again, demanding the addition of power unless you don’t mind landing a little short of the lights. Don’t forget the flaps. Adding lift and thereby increasing your induced drag, they’ll steepen your descent without increasing your airspeed. Neat. The reason many POHs list a different speed for a normal landing as opposed to a short field has to do with efficiency of the glide. Peg it at a speed other than best glide, and you’re on your way down in a hurry, baby: a major advantage if you’re inclined to plunk your wheels down on a specified spot and bring your flying machine to a stop before reaching the end of a shortish strip.
The long and short of it is that you’re going to have to keep a practiced eye out to monitor changing conditions. Yes, every time. Anticipating density altitude and wind conditions can get you part of the way there, but extending your downwind to accommodate other traffic is not always something that can be preplanned, nor are failures of things like flaps. Or engines. When’s the last time you practiced a no flap landing, my friend? Looks a little different than you’re used to, doesn’t it? And could you really glide to the runway from any point in that traffic pattern if your engine were suddenly to go kaput? No? Then perhaps that pattern you’re flying is a little on the wide side…food for thought. And for practice! Of course, if you’re finding yourself consistently outside your comfort zone, grab a CFI and get little bit of dual. They should have a few insights for you regarding power settings for your chosen airplane and local landmarks for your traffic pattern.
Pitch for airspeed, power for altitude, and don’t be shy about going around,
Mom
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