55-60 kts over the fence the Kolb has deadly pitch characteristics at slow speed with the 100 hp Rotax. That aircraft developed severe aero dynamic flutter of the tail I managed to get it on the ground but it was badly damaged…. Hint 100 hp is too much for the tail boom
@@donmccall4634 Thinking of building one of these getting my light sport license. Any suggestions I see from your above statement the Rotax 912 is too big I was thinking of a 582 2 stroke. You mention the tail boom flutters is that from exceeding VNE? Difficult to find transition training for experimental like this. When you say "deadly" pitch characteristics what does that mean? Found a post on homebuilt airplanes forum regarding this flutter.
@@Mike-01234 Hi It would be good for you to do some research on accidents relating to this aircraft for your own education, the following is my opinion as a test pilot for amateur built aircraft.... The tail of the aircraft only protrudes into the thrust stream about 50%. this means that the prop wash is primarily hitting the tail from one side. Because of that it is necessary to either offset the tail/rudder fin or apply a larger trim tab. I did the later, as I did not build this aircraft. Unfortunately the aerodynamic balance gained from the trim tab probably helped induce the flutter. Up until then it always required considerable right rudder pressure to retain balanced flight. In hindsight this probably contained the propensity of the aircraft to develop flutter. The tail went into flutter on climb out about 150-200 feet and no where near the VNE. I think that a 60-80 HP two stroke would be a much better match to the airframe. The pitch and roll controls are no where near balanced and it is extremely easy a slower speeds to get into extreme pitch isolations... It "feels" like the tail just "drops away" or it "noses over" with little or no input. I found small rapid corrections on the controls made it flyable.... Again this is my opinion.... The flutter was witness by numerous spectators on the ground many of whom thought that I would not survive it...
@@donmccall4634 Thanks for the quick reply I found your post and the owners reply on the homebuilt forum. My understanding that this one was purchased either used, or almost completed the owner finished the build off. These were test flights you were doing for him. The question is do you think these flaws you describe is just limited to this one aircraft maybe the prior owner didn't build it right, or do you feel these flaws are a design flaw. I think the Mark 3 is slightly different depending on when it was manufactured. Glad you were able to get it on the ground must have been terrifying. Seems like lot of these Kolbs flying if this was a design flaw, we would hear lot more about it. I wonder if the tail not being 100% in the slipstream of the prop lost effectiveness at slow speeds. Looking though accident reports on the NTSB site 29 since 1989 in all Kolbs most were pilot, or engine failure caused.
@@Mike-01234 Hi yes please do some research there have been a number of fatalities especially where people were too slow on base and or final. You are correct this aircraft was purchased almost complete but I don't believe that it had ever flown. I went over it with a fine tooth comb did my own weight and balance and was concerned about that and some other aspects. I contacted the manufacturer and I was assured that the figures were within the design envelop. It was built according to the plans that were supplied. You are correct there are several versions of the Mark3 there are at least two different undercarriage configurations and changes to the controls doors etc. Some things that concerned me were, the CoG was at 34% of the cord which in my opinion is too far aft, the weight on the tail wheel was around the 50KG mark from memory. The engine originally a 65hp two stroke had been changed with Rotax 100 hp with no change in engine positioning. I have many hours (100s) in pusher aircraft, engine failure on take off in a pusher is fatal if there is inadequate control to get the nose over extremely quickly in a controlled manner, especially with a three bladed prop that acts as a giant break positioned above the CoG. I would agree at slow speeds the tail appears to be out of the slipstream. Good luck and fly very carefully... at the hint of engine failure get the nose over and pointed down.... the glide ratio is somewhat a kin to that of a brick... keep the speed up or become a statistic..
lot of stick work but nice landing
What’s your airspeed on final? That landing seemed a bit fast, but I wonder if it’s just because of the angle.
55-60 kts over the fence the Kolb has deadly pitch characteristics at slow speed with the 100 hp Rotax. That aircraft developed severe aero dynamic flutter of the tail I managed to get it on the ground but it was badly damaged…. Hint 100 hp is too much for the tail boom
@@donmccall4634 Thinking of building one of these getting my light sport license. Any suggestions I see from your above statement the Rotax 912 is too big I was thinking of a 582 2 stroke. You mention the tail boom flutters is that from exceeding VNE? Difficult to find transition training for experimental like this. When you say "deadly" pitch characteristics what does that mean? Found a post on homebuilt airplanes forum regarding this flutter.
@@Mike-01234 Hi It would be good for you to do some research on accidents relating to this aircraft for your own education, the following is my opinion as a test pilot for amateur built aircraft.... The tail of the aircraft only protrudes into the thrust stream about 50%. this means that the prop wash is primarily hitting the tail from one side. Because of that it is necessary to either offset the tail/rudder fin or apply a larger trim tab. I did the later, as I did not build this aircraft. Unfortunately the aerodynamic balance gained from the trim tab probably helped induce the flutter. Up until then it always required considerable right rudder pressure to retain balanced flight. In hindsight this probably contained the propensity of the aircraft to develop flutter. The tail went into flutter on climb out about 150-200 feet and no where near the VNE. I think that a 60-80 HP two stroke would be a much better match to the airframe. The pitch and roll controls are no where near balanced and it is extremely easy a slower speeds to get into extreme pitch isolations... It "feels" like the tail just "drops away" or it "noses over" with little or no input. I found small rapid corrections on the controls made it flyable.... Again this is my opinion.... The flutter was witness by numerous spectators on the ground many of whom thought that I would not survive it...
@@donmccall4634 Thanks for the quick reply I found your post and the owners reply on the homebuilt forum. My understanding that this one was purchased either used, or almost completed the owner finished the build off. These were test flights you were doing for him. The question is do you think these flaws you describe is just limited to this one aircraft maybe the prior owner didn't build it right, or do you feel these flaws are a design flaw. I think the Mark 3 is slightly different depending on when it was manufactured. Glad you were able to get it on the ground must have been terrifying. Seems like lot of these Kolbs flying if this was a design flaw, we would hear lot more about it. I wonder if the tail not being 100% in the slipstream of the prop lost effectiveness at slow speeds. Looking though accident reports on the NTSB site 29 since 1989 in all Kolbs most were pilot, or engine failure caused.
@@Mike-01234 Hi yes please do some research there have been a number of fatalities especially where people were too slow on base and or final. You are correct this aircraft was purchased almost complete but I don't believe that it had ever flown. I went over it with a fine tooth comb did my own weight and balance and was concerned about that and some other aspects. I contacted the manufacturer and I was assured that the figures were within the design envelop. It was built according to the plans that were supplied. You are correct there are several versions of the Mark3 there are at least two different undercarriage configurations and changes to the controls doors etc. Some things that concerned me were, the CoG was at 34% of the cord which in my opinion is too far aft, the weight on the tail wheel was around the 50KG mark from memory. The engine originally a 65hp two stroke had been changed with Rotax 100 hp with no change in engine positioning. I have many hours (100s) in pusher aircraft, engine failure on take off in a pusher is fatal if there is inadequate control to get the nose over extremely quickly in a controlled manner, especially with a three bladed prop that acts as a giant break positioned above the CoG. I would agree at slow speeds the tail appears to be out of the slipstream. Good luck and fly very carefully... at the hint of engine failure get the nose over and pointed down.... the glide ratio is somewhat a kin to that of a brick... keep the speed up or become a statistic..