Do props destabilise Aircraft??
07-14-2013, 08:52 AM
#51
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RE: Do props destabilise Aircraft??
Years ago, a fellow club member built an eight engine model with 4-.40's, a couple of .25's and a couple .15's out of a stretched Cub wing and a huge amount of balsa. He wanted to shoot video's out of the rear hatch (it was configured like a C-130). When flying with all turning, it had significant Yaw instability, but when flown on just the .40's it was pretty well behaved. Of course the best part of the design was the incredible sound it had when all eight engines were running and tuned up. Not having all the same size engines made it sound much more real since there were different rpms present.
07-14-2013, 10:23 AM
#52
RE: Do props destabilise Aircraft??
ORIGINAL: HighPlains
Years ago, a fellow club member built an eight engine model with 4-.40's, a couple of .25's and a couple .15's out of a stretched Cub wing and a huge amount of balsa. He wanted to shoot video's out of the rear hatch (it was configured like a C-130). When flying with all turning, it had significant Yaw instability, but when flown on just the .40's it was pretty well behaved.
Years ago, a fellow club member built an eight engine model with 4-.40's, a couple of .25's and a couple .15's out of a stretched Cub wing and a huge amount of balsa. He wanted to shoot video's out of the rear hatch (it was configured like a C-130). When flying with all turning, it had significant Yaw instability, but when flown on just the .40's it was pretty well behaved.
The sound alone must have been sufficient to justify the project !
Dick
07-14-2013, 11:24 AM
#53
My Feedback: (1)
RE: Do props destabilise Aircraft??
I think the difference in flying characteristics was strictly due to differences in prop disk area. The .15's were all noise, they had a tendency to go rich in the air and start 4 cycling (prop pitch was too low) but the .25's ran strong. All the engines were matched (4 ST .40's, two OS .25's, and two OS .15's). In the air, it sounded a bit like a P-3 coming in for a landing at Moffett Field in Mountain View, Ca.
The owner of the eight engine monster liked unusual airplanes. He had a four engine model that was fairly acrobatic. It was able to dive without picking up much speed on the down line when at idle, so you could make amazing landings with a very high approach, dropping 100 feet and then pulling out right at the end of the runway. It was also great for low and slow flying since the loss of a single engine had little effect. There is a Youtube video of a actual C-130 doing stuff at an air show that is beyond belief.
The owner of the eight engine monster liked unusual airplanes. He had a four engine model that was fairly acrobatic. It was able to dive without picking up much speed on the down line when at idle, so you could make amazing landings with a very high approach, dropping 100 feet and then pulling out right at the end of the runway. It was also great for low and slow flying since the loss of a single engine had little effect. There is a Youtube video of a actual C-130 doing stuff at an air show that is beyond belief.
