I couldnt remember as it was in the 90's when I went to Don's for my Commerical gyro and heli add on.
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I busted the first check ride in the 18A as It fles so good I forgot to close the canopy while I exceeded the speed for it while it was open. I was just use to the open frame gyros so the wind just didnt bother me. I thought I was doing good and Don said turn around.
It doesn't have a canopy, but there is a cockpit door on the right side. If left unlatched the airflow will ordinarily hold it closed. There is a door-
off max speed that Don may have had in mind, but that applies if you remove the door completely (perhaps for an aerial photography flight).
That 18A always had a good stick bump from one of the rotors being out some. I really didnt care for that.
You can track and balance the blades on an 18A with a Chadwick just like on a helicopter; there are tabs on each blade. The one we have for sale (N6131S) is very, very smooth; most teetering rotor pilots who fly with me in it remark about how much smoother the three blade system is. Al Ball's ship (N6134S, the one that started this thread) was also well tracked and smooth when I last flew it.
You think that forward taxi speed would spin the rotors faster? It does on a J-2. But two totally different ships.
Check a picture of an 18A, see how vertical the mast is, and you can tell that the flow is edge-on to a flat disc, and does diddely-squat for rpm. You're also doing the run with flat collective pitch. Once you put in pitch, you leave the ground at that moment, so you're never running along the ground with positive collective pitch like a teetering system.
My J-2 lost rotor rpm during a take-off run, too. If you tried back stick in the J-2 to build rpm all you would accomplish is lengthening the take-off (if lucky) and not getting off at all (if not lucky). It was designed to spin to more than 100% flight rpm, and I can't imagine why you wouldn't do that. The J-2 flight manual says the
minimum pre-spin is 400.
The process for a short, safe take-off in the J-2 was to spin to the ground redline of 520 rpm, then up-lever, brakes off and immediate full throttle, twitch the stick back at 45 mph, and off she went. By the time you had 45 (typically well under 200 feet of runway for me), the rotor rpm would be down to flight speed, just over 400. I've seen people try to fly a J-2 like an airplane or like a teetering gyro, and it's not pretty to anyone who knows how they were intended to be operated. They'll use runway like it's going out of style for both take-off and landing, managing to fly at all only because it is forgiving.
There's a famous story around here about a J-2 enthusiast years back (owner of a big furniture business) who thought he could shorten his time on the busy runway with heavy traffic departing from an airshow / fly-in, by a quick partial spin followed by charging down the runway to get rpm. He didn't get any, and found himself with lots of ground speed, no runway left, and slow blades.