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Straight Descents and Descending Turns

The airplane will lose altitude without your help. This maneuver is about losing it on purpose — at a chosen speed, on a chosen heading, stopping at a chosen altitude.

Fundamentals of Flight — FI.VIII.D

Why you learn it

This maneuver sits early in training because it is the first place you feel that pitch and power are one system rather than two separate controls, and that altitude is energy you are spending. Every approach is a descent held to a standard, and so is a power-off landing after an engine failure. Get this right and those are variations; get it wrong and each becomes a rushed, unstable arrival.

So the standard is not that the airplane comes down. The standard is that it comes down in a controlled, stable manner — arriving at the altitude you chose, on the heading you chose, at the airspeed you chose, with the airplane trimmed and you still ahead of it.

Entering and holding a straight descent

A straight descent is a descent flown on a constant heading, wings level. Enter it deliberately:

  1. Clear the area, and pick the altitude you are descending to before you start.
  2. Reduce power to the descent setting in your POH.
  3. Hold the pitch attitude with elevator while the airspeed bleeds off toward your descent speed. Do not push the nose over the moment the power comes back.
  4. As the speed arrives, lower the nose to the attitude that holds it, and let the airplane start down.
  5. Trim off the control pressure, then check the ball and your heading.

Once you are stabilized, the working rule is simple to state and takes a while to believe: set the airspeed with attitude and the rate of descent with power. The two are still one system — pull the power back at a fixed attitude and the airplane will slow down as well as come down faster — but as a way of dividing the job between your hands it holds up. If you are fast, look at the attitude first. If the speed is right and the ground is coming up quicker than you want, look at the power.

Trim is what turns this from work into flying. Trim after the attitude is set, never before. When you can take your hand off the yoke and the airspeed stays put, the airplane is doing the holding and you are free to look outside, run a checklist, and think ahead. An untrimmed descent is where a student's workload quietly doubles.

Leveling off

The airplane has inertia, so you start the level-off before you get there. Lead it by roughly ten percent of your rate of descent — coming down at 500 feet per minute, begin about 50 feet high. What happens next depends on the speed you want when you arrive. Leveling off at cruise speed, add power first and hold the descent attitude while the airplane accelerates, raising the nose to the level attitude as the speed comes up; raise it too early and the airplane mushes along slow and low. If instead you want to keep the descent airspeed after level-off, as you often will in the pattern, add the power and raise the nose together. Either way, retrim once it settles.

Descending turns

A descending turn is the same descent with a heading change layered on top. Bank is what changes, and it changes two things at once. Rolling into the turn tilts the lift vector, so less of it is holding the airplane up: at the same pitch and power the nose wants to drop and the descent rate increases. You need a little back pressure to keep the attitude, and you may want a little power to keep the rate where you want it. Roll out and the reverse happens.

Start shallow and build up, and keep training descending turns at moderate bank. The task standards hold you there, and so should judgment. Steeper bank raises the load factor and the stall speed with it, at a moment when you are deliberately giving away altitude, and it makes the descent rate harder to hold where you put it, because more of the lift is turning the airplane and less is supporting it. A steeper bank also hides more sky behind the wing. There is little in a training descent that pays for any of that.

Coordination is the other half. Ailerons set and hold the bank, rudder answers the adverse yaw the ailerons produce, and the ball tells you whether your feet are awake. The two faults are opposites and it is worth being able to name them. Too little rudder for the bank and the airplane slips: adverse yaw holds the nose back, the turn comes around more slowly than the bank suggests, and the ball falls toward the inside of the turn. Too much rudder and it skids: the nose is pulled around faster than the bank alone would take it, and the ball slides to the outside. The skid is the one that kills people. A skidding turn from base to final, low and slow, with the airplane near its stall, is the classic setup for a spin with no altitude left to recover in. The feet you build here at altitude are the feet you will have there.

What to look at

Fly the attitude outside first. The relationship between the cowling and the natural horizon is your descent attitude, and in a turn the angle the horizon cuts across the windshield is your bank. The instruments confirm what the picture already told you — that is the idea behind integrated instruction, and the order matters. Set the picture and then check the airspeed indicator and you learn an attitude. Watch the needle and pitch at it and you learn to chase, and the chase never ends. Either way, fixation is the failure mode. In visual conditions your eyes belong mostly outside, with short glances in to confirm; the limit is on any one place, not on the time you spend looking out. No single instrument and no single spot on the horizon deserves more than a couple of seconds at a stretch.

What goes wrong

The common errors are consistent enough to name. Pitch attitude too high or too low, so the airspeed is wrong and the descent either drags out or dives. Chasing airspeed with the elevator instead of setting an attitude and trimming. Feet flat on the floor through the turns, so adverse yaw holds the nose out of the turn and every roll-in is a small slip, with the ball resting toward the inside waiting to be stepped on. More bank than the maneuver needs, then a fight to hold it. And a scan collapsed onto one instrument or one point outside, which costs you the heading, the altitude, and eventually your sense of where you are.

Managing the risk

A descent puts you into somebody else's altitude. Clear before you go down and keep clearing on the way, and know which piece of sky your own airplane takes away from you. In a high-wing, the inside wing drops across the view toward the inside of the turn and below — which is exactly where you are going — and that is the reason for the old habit of lifting that wing and looking before you roll. In a low-wing, it is the raised outside wing that covers the view out and above. Traffic displays, advisories and position reports all help, but see-and-avoid is still the technique doing the work.

Prioritize the way you were taught — aviate, navigate, communicate — and treat the descent itself as the aviating. Distraction is what produces the altitude bust, so name the level-off altitude out loud, set it, and cross-check the altimeter rather than trusting the picture to tell you when to stop.

Two items belong to descents specifically. A carbureted engine at low power is in the condition that makes carburetor ice, so use carburetor heat as your POH directs. And on a long low-power descent, advance the throttle briefly now and then to clear the engine — partly to keep it warm, partly to learn that it still answers before you need it to.

Where you meet it next

On the flight instructor practical test this is a Fundamentals of Flight task in its own right, taught and demonstrated to a student next to straight-and-level flight, climbs and climbing turns, and turns to headings. Before that, it hides inside almost everything else: the descent from cruise on a cross-country, the pattern, the stabilized final, the power-off 180, and the emergency descent.

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