chuter
Platinum Member
I came across some info this weekend I though I should share here on the conference. I don’t remember seeing it here before, but I could’ve missed it.
Basically, with a tractor design it is good to check the % of fuselage before and aft of the rotor. To do this, put the fuselage in flight attitude (level), drop a vertical line from the rotor head (I’m really not sure if it should be the teter bolt or the pitch pivot), then measure in front of the line to the prop, and behind the line to the front edge of the rudder. The ratio should be about 60/40, with 60% behind the vertical line from the rotorhead. The further away from 50/50 the better.
I was told that a few tractors have gotten into flat spins while in a power climb at low airspeeds; the p factor will start to yaw the fuselage and if you don’t have enough moment arm for the tail it will turn into a flat spin. At least one of the tractors that it occurred to had been flying for several years without incident, and I believe the front to back ratio on them was close to 50/50.
These were not any tractors designs that are currently flying as far as I know: definitely not a LittleWing.
Just a heads-up for anyone tinkering with tractor designs, I wasn’t aware of it when I was building mine. Turns out mine is very close to 60/40, but it’s still good to know and watch out for it.
Basically, with a tractor design it is good to check the % of fuselage before and aft of the rotor. To do this, put the fuselage in flight attitude (level), drop a vertical line from the rotor head (I’m really not sure if it should be the teter bolt or the pitch pivot), then measure in front of the line to the prop, and behind the line to the front edge of the rudder. The ratio should be about 60/40, with 60% behind the vertical line from the rotorhead. The further away from 50/50 the better.
I was told that a few tractors have gotten into flat spins while in a power climb at low airspeeds; the p factor will start to yaw the fuselage and if you don’t have enough moment arm for the tail it will turn into a flat spin. At least one of the tractors that it occurred to had been flying for several years without incident, and I believe the front to back ratio on them was close to 50/50.
These were not any tractors designs that are currently flying as far as I know: definitely not a LittleWing.
Just a heads-up for anyone tinkering with tractor designs, I wasn’t aware of it when I was building mine. Turns out mine is very close to 60/40, but it’s still good to know and watch out for it.