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Steep Turns: More Than Meets the Eye

Steep Turns, also called Steep Power Turns, are another "performance" maneuver that is useful for more than passing your checkride, or expediting a course reversal in visual conditions.

Steep Turns, also called Steep Power Turns, are another "performance" maneuver that is useful for more than passing your checkride, or expediting a course reversal in visual conditions. They're not as complicated as the chandelle or lazy eights -- no plan view or plots of pitch & bank vs. heading needed for this one -- but they still require smooth coordination of (and anticipation for) pitch, bank, and power. They're also great for refining control techniques and developing the ability to divide one's attention. For many, it's the first exposure to what a higher "g" load feels like. Another important benefit is the introduction to the realm outside normal static lateral stability: the "overbanking tendency". Once you're familiar with how to do it, you just roll into a steep bank and fly a circle, then another in the opposite direction. Of course, there's a little more to it than that...

Overbanking Insights: Things like dihedral and keel effect normally cause a return to wings level after small aileron movement, which is positive stability. By roughly 30 degrees of bank, most airplanes will remain in the banked turn, with a little nose-up trim, which is neutral static lateral stability. But beyond that, differential outside wingtip speed and centrifugal force overcome this stability, and the bank will get steeper, all by itself.

BEYOND THE COMMERCIAL
This one is on just about every checkride -- even the Practical Test Standards (PTS) for recreational pilots say one 360, 40 to 50 degrees of bank, within 10 degrees on roll-out heading, and 200 feet on altitude -- but they call it a "constant altitude turn." Private pilots might be given the option to roll out and begin a second turn in the opposite direction, as specified by the examiner -- the commercial PTS says "immediately followed by" a circle in the opposite direction. And the instrument PTS says "either 180 or 360, left and right". By the way, PTS tolerances for heading roll-outs are given as plus or minus five degrees for all levels. In the same manner, the PTS lists airspeed tolerances as plus-or-minus five knots. The tolerances for maintaining maneuver entry altitude from private through ATP are plus or minus 100 feet.

FAA-isms: All of the various PTS are not written by the same person, so some may say "plus or minus 100 feet", some may say "plus or minus 50 feet", or "within 100 feet." They are all supposed to mean the same thing: your window is 100 feet. The same applies for almost all the other criteria. And the most central criterion of all is, of course, bank angle.

BANK ANGLE
That's where it gets interesting. All levels specify 45 degree banks, plus or minus five degrees (though the ATP calls for "at least 45 degrees"), with the exception of the commercial check ride, which requires 50 degrees, plus or minus five. Almost all require that you remain above 1500 AGL at all times, though it's 3000 for ATP and multi-engine folks, and for ATP it's "or as recommended by the manufacturer", so if you do it in a Seminole, you'll be at 4000. You're expected to establish either the manufacturer's recommended maneuver airspeed or an airspeed not to exceed maneuvering speed, Va.

Inside Information: It might be a good idea to calculate your "actual" Va relative to the published Va, which is for max gross weight (MGW). To get the right number, multiply the listed Va by the square root of the ratio of present weight to MGW.

FROM METRICS TO MAGIC
It's easy just to say "enter a smooth, coordinated 360-degree steep turn" and "divide attention between airplane control and orientation." But, not so easy to do -- so, here's some help...

BEFORE

  • Use cruise power for entry; any less requires even more pitch and bank input. (Practicing at reduced power improves anticipation and yoke skills... it will also put you closer to a stall.)
  • Be smooth and quick with your entry into the banked turn.
  • Pick a point on the windshield at eye level, offset from the aircraft centerline by the same distance as your head, (read: in front of your face) and keep it on the horizon. This will help you avoid gaining altitude in a left turn, or losing it when turning to the right (a phenomenon typical for pilots of side-by-side seat aircraft).
  • Use prominent land features for heading references -- remember to keep watching for them!
  • Expect and react: Don't add back-pressure or open the throttle in the turn until the airplane needs it.
  • Right rudder: Be sure to lead any steep turn to the right with enough rudder.

DURING

  • Two full turns of trim will often release most of the back pressure required. (There are two schools of thought on this: the trimmers, and the "no trimmers".)
  • Scan for traffic on the outside horizon, while also scanning your heading indicator, attitude indicator, & turn coordinator. Just because you're busy doesn't mean you won't hit somebody ... actually, it increases those chances.
  • About five degrees of pitch is required to maintain altitude in a 50-degree bank.
  • Use a little "outside aileron" to keep the bank from getting too steep, and "inside rudder" to correct for adverse yaw. (You'll need more, going right.)
  • Bracing your elbow against a door handle (or whatever is handy) will help you hold attitude and bank.
  • Decrease bank to correct a small altitude loss rather than adding back pressure, which could help induce an accelerated stall.

AFTER

  • Lead roll-out by half the bank angle; and remember to use enough forward yoke.
  • Level off with positive forward pressure when exiting the turn, to prevent a sudden altitude gain -- if trimmed for the turn.
  • Take out any trim (and extra power) when leveling out after recovery.

BOOK LEARNIN' -- THE MATH BEHIND THE MAGIC
As far as the "exhibits knowledge of elements related to steep turns" criterion, there's a whole world of complex interactions out there, but a few simple reference points may serve to anchor a deeper understanding:

  • Stall speed is a function of the square root of load factor (which in turn is the reciprocal of the cosine of your bank angle). Example: bank = 60°, cosine = 1/2, load factor = 2, stall speed goes up by 1.414 or 41%! Regardless of airspeed, a given bank angle always results in the same load factor -- assuming level flight is maintained (or more strictly speaking, flight with no vertical acceleration).
  • At any given angle of bank -- for any aircraft -- turn radius increases as the square of velocity.
  • At a given airspeed, turn radius decreases as bank angle increases (actually, its tangent).
  • At a given airspeed, rate of turn increases with bank angle (again, its tangent).
  • And the final point: banking multiplies wings-level induced drag by that reciprocal of the cosine of bank angle. Theoretically, the tightest turn allowable for normal category airplanes would be at Va, at a bank angle reaching its design g-load (+3.8g) without stalling, which would be almost 75°. However, for most airplanes, the power required just isn't there. Most 172s at anything much over 55° will simply lose the ability to maintain level flight. That's another useful realization in working on the commercial steep turns!

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