MY E-MAIL:

I need some expert evaluation and advice on what was an adventurous aerotow yesterday. Wind was light and variable on the ground, but a little stronger at 1000-1200 ft. Unfortunately, my soaring buddy was flying my Joker on his first tow…

Takeoff and initial climb was normal as was the first turn to the left. I noticed, on the second turn (to the right), the towplane was level or descending, then started to climb again. I noticed the towline was somewhat slack, too, but then tightened as soon as the towplane climbed.

On the third turn (also to the right), a downwind turn to a path directly toward us, I noticed a HUGE towline loop and a slight increase in engine RPM denoting the towplane was again level or descending. About the time I finished saying we're gonna get a real whip effect, the towline looped around the RH stabilator and base of the fin of my sailplane. The towplane actually dragged the Joker backwards a few seconds. After realizing the towline was not going to release from the sailplane I calmly told the towplane pilot to release his end. The Joker started flying almost immediately and was landed without incident. The only damage to either aircraft was some scarred paint around the sailplane's fin LE and stabilator joiner wires.

I flew four more successful tows into strong lift for some really long flights, but my soaring buddy refused to fly the rest of the day.

Talking to the towplane pilot, immediately after the backward tow, he mentioned that he had dialed-in a couple of clicks of down trim "so the plane would fly better". Hence the reason the towplane appeared to descend when initially turning. (I have the towplane trimmed to fly straight and level at half throttle; it will climb at a 20-30 degree angle at full throttle without touching the trim). The trims were returned to neutral and the remaining tows were uneventful.

With respect to the downwind turn, I theorize the towplane leveled-off/descended, and the sailplane turned inside the radius of the towplane's path, perhaps as a result of the crosswind condition. I also surmise the sailplane accelerated, although I had three clicks of up trim dialed in for the tow.

So, my questions to you are, (1) am I correct in assuming the towplane must maintain a positive rate of climb to prevent a slack towline, (2) what do you think of my downwind turn theory, (3) what are your suggestions and theories?

End of email

JOHN DERSTINE, FOUNDER OF THE ANNUAL ELMIRA (NY) AEROTOW:

Never fly over your head or towards yourself, you lose all perspective… Listen for the motor, if it increases RPM, you have already been descending for a while (sound lag)… Sharp turns downwind can be problematic; large sweeping turns are better, and…figure 8's into the wind (like slope soaring) are good in high winds aloft.

Power planes always descend in a turn unless the pilot corrects with elevator. The biggest problem for inexperienced pilots, this is exaggerated while towing, that's why large sweeping turns are easier and smoother.

The only effect the downwind turn has is in the relative difference in towplane/glider inertia, slippery glider vs. relatively stable-in-penetration power plane with big brake on front - prop - to modulate any "perceived " downwind effect. When two planes are tied together this effect can be very real and accentuated.

Don't overanalyze, fly smooth, wide circles or gentle turns, and don't fly overhead or towards yourself. Release if in doubt, don't wait for the airplanes to stop flying to abort the tow…

Experience is the only solution, keep on towing and practice in all wind conditions with the idea that if things are not just right get off and try again. Problems are compounded if one or both pilots are unfamiliar with towing or with the particular aircraft. New situations might be better explored on calm days until you guys get used to each other and each other's aircraft/flying styles.

The tow plane pilot needs to constantly readjust trim for reasons stated above, few tugs perform automatic tows. I had a 1/3 Flybaby Bipe that would fly a tow hands off making its own climbing turns, but that is not the norm, and in windy conditions that didn't work either.

It is hard for me to dissect a tow sometimes because as you will no doubt discover, it all becomes automatic after about 1000 tows. Kinda the ZEN of towing. As tow pilot I keep an eye on both planes, but I now realize that in the beginning I only flew the tow plane or the glider, and waited too long before deciding to get off a bad tow.

LANDON GRINDSTAFF, EXPERIENCED AEROTOW PILOT:

A positive rate of climb of the towplane assists in maintaining a tight towline. The towplane and the sailplane must remain "flying" at all times.

A downwind turn in moderate to heavy wind is not a good idea, as tacking is far more preferable. Tacking yields a greater altitude, very quickly, and also keeps the aircraft in front so you can observe angles of attack and relative speeds. At all times the sailplane must be level with or above the towplane and always on the outside of a turn. Sailplanes like 2 to 3 clicks of up trim and/or 5 to 10 degrees of flap dialed in. This does more to keep the sailplane in the correct vertical position and to maintain a tight towline, than just about anything else you can do.

If wind is blowing 5 to 10 on the ground, it's blowing 15 to 20 at 500 feet. With a steady head wind of 5 to 10 on the ground, it's almost a sure bet you'll be better off tacking into the wind instead of towing in circles. The tack across the wind produces the greatest gain in altitude. The left and right turns at the end of the tack must be gentle and slow and the tow pilot must be prepared to feed-in just a little bit of down elevator to avoid excessive angles of attack and loss of flying speed. The tow pilot should announce the intended turn and give the sailplane pilot time to insure he is in the correct position for the turn. The turn must be wide, gentle and almost flat. The tow plane will typically want to climb too much as it faces into the wind, especially if the turn was gentle and flat. Correct with slight down elevator on the tow plane.

I trim my tow plane for the weight and drag of the sailplane that I am towing…on my towplane an eight-pound sailplane tows very steeply at neutral trim… An 18-20-lb. sailplane tows with 3 to 4 clicks of down trim. A 30 to 35 lb. sailplane tows with as much as 8 clicks of down trim. The need for down elevator when turning into the wind from a crosswind tack still applies and I handled that with the stick, not with trim as it is a temporary condition.

How to make the turns, how to handle the wind and how to correct for different weight sailplanes takes quite a bit of experience. Each tow plane responds differently. Unfortunately, there is no substitute for stick time with a particular tow plane or tow plane/sailplane combination. Don't be discouraged, make gentle turns with the towplane, call the turns ahead of time, and tow into the wind when possible.

ERIC MEYERS, CO-FOUNDER OF HORIZON HOBBY & EXPERIENCED AEROTOW PILOT:

Constant climb rate is essential. Frankly speaking, I think it's very tough to think about "trimming" the towplane. You simply have to FLY it - it won't fly itself. Different planes present different drag profiles, thus the need for flexibility.

It appears the sailplane pilot turned inside the towplane. The most common sailplane flying error is trying to "anticipate a turn". All a sailplane pilot need do is KEEP THE WINGS LEVEL and everything will take care of itself. The towplane will drag the sailplane around. That's all there is to it, but lead the towplane, and all hell breaks loose.

It's easy - once you get everything working right - but until then, I can understand it's a little hectic. Admittedly I was a nervous wreck the first couple dozen times I tried it.

PETE GEORGE, FOUNDER OF THE ANNUAL OC-TOW-BERFEST (ST. LOUIS) AND EXPERIENCED AEROTOW PILOT: