Seconds before, I had been sitting on the runway awaiting my turn in the tow line while running through the checklist. I asked my passenger (a friend of my son's) to read each of the steps while I performed the check. When we got to the Situational Awareness line, I explained that now is the time to visualize what you would do if something unexpected happened.
Usually, that's a tow rope break but a few moments later I was dealing with a potential towplane engine problem.
The initial tow up to takeoff speed was SLIGHTLY different but not enough to alarm me. It felt like slow, smooth acceleration but as we rolled down the runway I noticed it took a bit more distance than usual to get airborne and that we weren't accelerating quite as fast as normal. I glanced at the airspeed indicator as I lifted off and it was about 5 knots slower than it should be.
I watched the towplane, still rolling on the runway, pass off of the pavement and onto the grass, bounce once hesitate in the air, then bounce again on the grass and finally stay in the air. As we passed over the brow of the hill, it followed the contour down to gain speed. We were at 60 knots, the proper tow speed for the ASK-21 glider it was towing.
Harris Hill is atop a ridge some 700 feet above the valley and within a few seconds we were blessed with 700 feet of altitude to sort things out. I followed the tow plane, climbing VERY weakly, but at least climbing, as we turned to the West. I made the remark about the tow plane not climbing properly and prepared to release if I saw the propeller stop. We continued West, alternating between a weak climb and maintaining altitude.
I keyed the mike and asked the towplane pilot if everything was okay. No response. I located the emergency...er, ALTERNATE, landing field in the valley below and prepared to land there for the second time in my gliding career. As I did, the tow plane made a 180 degree turn and we headed back toward Harris Hill at what looked like the same altitude as the runway.
We arrived on what I would describe as a very close right base leg and the tow plane rocked its wings from side to side -the signal to a glider pilot to GET OFF. I released immediately but didn't think I had the altitude to get back to the runway. "We're probably going to have to land in the valley below," I told my passenger.
I continued gliding towards Harris Hill and made the decision that I would only try for the field if I was sure I could make the turn - a 90 degree right hander without getting close to the ground. After all, on my left was the safety of the valley and the field below. The last thing I wanted to do was try to be a hero and dig in a wingtip trying to turn too low.
I lost little altitude as I flew down base, but I was MUCH lower than I usually am. I took one more look and decided that not only did I have enough to make the turn safely, but that I might actually have a shot at not landing in the grass short of the pavement. I checked my airspeed (speed is life!) and decided to make a gradual turn with the idea of landing diagonally across the field if I misjudged my altitude or encountered sink. The grass landing would be uphill and there would be no danger of overrun if I had to roll out and land before completing the turn.
I lined up on final, spoilers still closed, and flew a normal approach at the normal speed, easily making the paved threshold of the runway, touching down with spoilers closed. I immediately popped them open and maneuvered us to the edge of the runway to get out of the way of the tow plane who, I was sure, would be right behind us.
He arrived a few moments later and we discussed what happened. "I left the carb heat on somehow." Carburetor heat keeps ice from forming in the venturi and choking off air to the engine. It is usually used on landing and apparently the tow pilot forgot to turn it off. When it is on, it robs the engine of about 200 rpm of power -apparently just enough to make climbing out with a glider attached quite difficult.
Later that evening, I reflected on what happened. I felt good about the fact that I was never particularly alarmed, I kept my cool and made good decisions. My training for rope tow breaks took over right away and everything worked out just fine. It really helped that Harris Hill is on a ridge. If we'd had to clear an obstacle on flat land, the ride would have been much hairier. As it was, I gained more experience and learned a little something about my flying skills.
