Diving syndrome
06-25-2002, 11:24 AM
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Diving syndrome
Here is what I can think of. I've had all of these problems with other planes, and most of the time, the hit was on the elevator only, and it was never very violent:
1. Can your engine be creating some radio interference? I had the same problem with my PT-19, only it climbed. I found out that my reciever was out of tune. You said you replaced the radio, but if your engine is creating some interference, then that could cause it.
2. Where is your transmitter antenna in relation to the plane? If it is pointed straight at it, or a tiny bit to the side, that can cause it. I can make most of my planes glitch with the TX antenna pointed directly at it. Most stock TX antennas have a deadband right off the tip, and it spreads out in a cone shape the farther it goes.
3. Where is your antenna located inside the fuse? Sometimes it can pick up a stray signal from a servo or battery wire. It should be at least 1 1/2 inches away from other wires, and servos.
I haven't had this problem on my own stuff, but I have seen it before.
1. Is anything moving? like the fuel tank, battery, or wing? I was teaching a guy on his Duraplane, and although it was in a foam block his battery would sometimes move causing unexplained trim changes.
1. Can your engine be creating some radio interference? I had the same problem with my PT-19, only it climbed. I found out that my reciever was out of tune. You said you replaced the radio, but if your engine is creating some interference, then that could cause it.
2. Where is your transmitter antenna in relation to the plane? If it is pointed straight at it, or a tiny bit to the side, that can cause it. I can make most of my planes glitch with the TX antenna pointed directly at it. Most stock TX antennas have a deadband right off the tip, and it spreads out in a cone shape the farther it goes.
3. Where is your antenna located inside the fuse? Sometimes it can pick up a stray signal from a servo or battery wire. It should be at least 1 1/2 inches away from other wires, and servos.
I haven't had this problem on my own stuff, but I have seen it before.
1. Is anything moving? like the fuel tank, battery, or wing? I was teaching a guy on his Duraplane, and although it was in a foam block his battery would sometimes move causing unexplained trim changes.
06-26-2002, 05:31 PM
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Diving syndrome
Try this. With the tank full, let it go into that dive, and see if it will pull itself out. It doesnt have to be abrupt, but dont confuse it with pitching up due to increasing speeds. If it tries to pull out, then it goes up, noses over some, then pulls out, and gets more gradual each time then it is too nose heavy, and is called "overly stable" Check the CG when it is full, and then post how far forward it moved.
Will it even do it with the tank full? If it wont, the CG could be too far back. An airplane with an aft CG can do funny things on the pitch axis. I flew a friends Su-Du-Khoi funfly, and he had his CG very far back. It would all of the sudden pitch up if it was even 1 degree nose high, or vise versa. It wouldnt do it all the time though. (He never flys straight and level long enough for it to matter) Since you said your airplane is overly build, it might be too heavy for it to pitch up quickly.
Will it even do it with the tank full? If it wont, the CG could be too far back. An airplane with an aft CG can do funny things on the pitch axis. I flew a friends Su-Du-Khoi funfly, and he had his CG very far back. It would all of the sudden pitch up if it was even 1 degree nose high, or vise versa. It wouldnt do it all the time though. (He never flys straight and level long enough for it to matter) Since you said your airplane is overly build, it might be too heavy for it to pitch up quickly.
