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When in aerotow in a glider, I thought the correct way to get the towplane to turn right (say) was to move gently to the left. That would gently nudge the towplane’s tail to the left, which would then point the nose to the right and be a good signal that the glider pilot wants to turn right.

The FAA glider flying handbook displays the opposite technique in a diagram: towplane turning instructions for a glider

I don’t understand this. If you move right to ask the towplane to turn right, doesn’t that put the glider on the inside of the turn, and put you in the wrong place to follow the towplane around?

Which is the correct direction?

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    $\begingroup$ the inside turn has slower airspeed (good fir a high light glider) and not in the wake of the towing aircraft. $\endgroup$
    – ratchet freak
    Sep 30 '15 at 18:27
  • $\begingroup$ I learned to keep the tow-plane on the inside during my towing rating. $\endgroup$
    – SentryRaven
    Oct 1 '15 at 6:14
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The glider flying handbook is wrong. The glider signals to the tow pilot by moving to the outside of the turn.

We glider pilots have been trying toget the FAA to fix this and many other errors in the GFH for years. See the newsgroup rec.aviation.soaring

Also, many tow pilots ignore tow steering directions because they think they know better than the glider pilot where the lift is.

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    $\begingroup$ Three Instructors at my local glider port Have repeated the same. $\endgroup$
    – Akin Okegbile
    Jun 28 '18 at 20:17
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The turning radius R is given by,

$R \ = \frac{V^{2}}{11.26 \ tan \theta}$

where,

  • V is the true airspeed in knots

  • R is turning radius in feet and

  • θ is the bank angle in degrees

If the glider is turning at a radius greater than the tow plane, i.e. it is in the outside of the turn, it must be flying at a higher speed in order to complete each circle in the same time. For glider in the inside turn, the opposite is true i.e. the glider is flying at lower speed compared the tow plane.

Turning inside towplane

Image from FAA Glider Flying Handbook

Also for outside turn, the bank angle of the glider should be higher than the tow aircraft to compensate for the higher speed. The reverse is true for an inside turn.

Turning outside towplane

Image from FAA Glider Flying Handbook

Therefore, the only way the two aircraft can fly coordinated with the same bank angle is if they have the same speed and turning radius.

Flying the glider in inside of a turn is preferred because it is easy to give corrections (to have same speed and turning radius) compared to outside turn. The glider bank angle can be reduced till it returns to the correct position. Since the glider is flying at a lower airspeed (than the tow plane) it will accelerate as its turn radius increases so there will be no tendency for slack to develop in the tow line.

For gliders in outside turn, the bank angle has to be increased to reduce the turn radius. However, as the glider is flying faster compared to the tow plane, it (glider) will tend to overtake it as turn radius is reduced, developing slack in the line unless airspeed is also reduced (usually by yawing the glider away from the towplane). In this case, the correction process is more difficult.

For this reason, it is advisable to

...match the tow plane bank angle and point the nose of the glider at the tow plane's outer wing tip.

at-least for small bank angles.

In general, it is better to be in the inside of turn rather than outside:

If you have to err on one side or the other, it is better to err on the inside – especially when at a low altitude. This way, you’re not in as much danger of locking out.

as long as you are not too far inside so as to sink and stall.

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  • $\begingroup$ this is some useful content, but my primary question is: which way to go to indicate a turn to the towplane, and less what to do when the towplane is turning. $\endgroup$
    – Peter
    Oct 2 '15 at 4:09
  • $\begingroup$ @Peter I'm sorry I misunderstood your question. There are two versions of this signaling, of which the soaringsafety version makes more sense to me. Apparently there have been efforts to correct the handbook. $\endgroup$
    – aeroalias
    Oct 2 '15 at 5:16
  • $\begingroup$ Land-lubber question here: if the glider turns slightly to the right, causing the tow plane to yaw left he will correct with right rudder then turn right. Slight risk of sideslip. But if he turns left with the left yaw the risk would be for a skid, which is worse - am I correct? Also if the glider turns right he would be at a right bank. If the tow plane then pulls him left it would put the glider at an extra high aoa. All this can be corrected with control, but an outside turn seems to have a slightly higher risk of instability and would require more aggressive control inputs. $\endgroup$
    – TomMcW
    Oct 2 '15 at 13:53
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    $\begingroup$ This has nothing to do with signaling the tow pilot to make a turn $\endgroup$
    – rbp
    Jul 17 '16 at 20:42

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