Today several of us plan to fly the PW5. After preflighting it, I spend some time with private pilots M and S explaining the features of the Borgelt B50 computer and the MicroAir radio. We also spend some time with the winch launching section of the PW5 manual. Important points include adjusting the seat position and the trim according to the pilot's weight. S is heavier than M or me... one concern we have is that with lighter pilots, the way the wheels and the CG hook are arranged, it's quite possible that the moment of acceleration could cause the cockpit to rotate up and the tail boom to slam down. The manual has some advice on how to hold the stick.
And then there's this interesting comment: "During the steep climb the stick forces are of small value." Some winching experts have pointed out that stable gliders tend to climb at the angle that is the most efficient, i.e. the horizontal stabilizer will tend to orient the wings directly into the relative wind to achieve stability, and so the angle of attack and speed will tend to become optimized. They claim you can unhand the stick and a stable glider will climb well on its own. (I won't try that for quite a while!) The PW5's elevator is really small compared to the wings and the horizontal stabilizer, so it can't override the orienting effect. More on that later.
We set up today on the main runway, launching to the west due to the wind direction. We get an earlier start, which is good for practicing, but it also means the l
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ift isn't working for the first few flights. A visiting glider pilot (not a member) wants to go for a ride, so I go up with him in the Blanik (me in front, him in back). He's been a winch launch passenger once before, so it's not all new to him. We get a good launch, but with no headwind and since I'm not terribly aggressive in the climb yet, we only get up to 900' AGL. We turn left to look for lift, but we get into 5 knot sink right away, so essentially we have to turn back and never get out of the pattern. We come in for a good landing and roll right up to the launching point. Fun, but short. No one else was finding more than 1-2 knots of lift this early in the day, so I don't think we had much of a chance for a longer flight anyway.
Later in the day I set up for a flight in the PW5. As expected, the tail boom comes down, but not very hard. If this winch was as aggressive in the first two seconds as the OCSA winch is, this rotation could be an issue. Once I get off the ground, I get into a slight PIO (which means "pilot-induced oscillation", pitching up and down due to not controlling perfectly). It's not much as PIO's go, and only lasts for about two cycles. But as I mentioned yesterday, if you don't pitch up at least a little bit right away to present a load on the cable, you can overrun it. My two seconds of horizontal flight getting out of the PIO is too long, and I see the parachute slip below me to the left, so I release just before someone on the radio calls "abort, abort". I make a safe and smooth landing on the right side of the runway (to avoid the cable), and roll out about two thirds of the way down toward the winch. This is what we call a "PTT" or "Premature Termination of Tow". It's a long walk back with the glider behind the truck.
After a few Blanik launches and our club pres in his PIK, I'm up again in the PW5. This time my takeoff is smooth and I rotate up and start a pretty good climb. Someone on the radio calls to the winch driver "more power, more power". Before long my airspeed is 67 and flirting with 70 knots. The maximum allowed according to the manual is 65, so I start pulling back to try to adjust the speed (forgetting for a moment the statement "During the steep climb the stick forces are of small value."). Probably my next move would be to call for less speed, but suddenly the speed drops off and I hear/feel the cable release. Bummer - PTT #2. Hmmm... I can't see the chute or the line by this time, but I can't imagine that I overran it at this angle. But there's no time to analyze it: I'm at 400' AGL. That's high enough to turn around for a downwind landing, so that's what I plan to do. I have had a
rope break at 300' during auto-towing solo in a Blanik, so I've done this before.
I nose over and ensure I have flying speed. There was very little crosswind when I took off, so it doesn't matter much which way I go. Since the normal pattern is left-hand, I turn left and do a 270-degree turn and get lined up on the runway. Hmmm... The next Blanik is already lined up at the launching point. I know that when you have a PTT from an auto-tow or winch launch, where you go up steeply, you can't really land in the distance available back to the starting point. You would have to descend at the same 40+ degree angle you went up at, and that's not likely in a slippery glass ship. Maybe in a Blanik with flaps and a big slip, but not in this glider. Hmmm... passing over the launching point to the other end of the runway is not an option either, because our pres is landing his PIK there. There's a nice wide taxiway, just as long as the runway, so that's the obvious choice. Since I'm already lined up on the runway, I S-turn to the left and line up again. There's nothing in the way, and I make a nice smooth landing and roll to a stop about 100 feet beyond the launching point. No problem. But there's no way I could have landed back on the runway without overrunning the launch point. It's nice to have options!
So far today I have employed two of the three PTT landing procedures.
I discuss the flight with S, and can't quite figure out why it released. People on the ground thought my climb angle looked good. My slight pulling up and backing off on the stick to adjust the speed shouldn't have dropped the line very much. I'd be ready to go again after a waiting for Blanik or two to launch. But then the winch guys call in on the radio: we're done for the day due to a failed universal joint. Later on I see the U-joint pieces in the hangar - an old repair failed and it spun itself apart. That occurred during my launch, so now at least I know the cause of the sudden power loss and back-release.
By now it's 2:00 in the afternoon, so we break for lunch and tear down the gliders... and change a flat tire on one of the trailers. It was fun while it lasted, but the lift was weaker than expected so no one really "got away" today. The last of us leave the airport about 6:00. Hot and dusty, and grateful to the host club, we drive off into the sunset.