Originally posted by kjkimball
Take a look at a few of the airplanes we have built... Python,
Ti-12, Beast. All better than 1:1 thrust to weight at airshow take off
weight. Gets even better than that as fuel and smoke oil burns off.
400hp normally aspirated 6 cylinder parallel valve lycomings make
300-330 hp. the claims of 400 are simple stretches of the truth as it
cannot be done without boost. Also, a supposedly 400hp 11:1 compression
540 with 3 blade 80" Mt prop makes 1250 lb thrust. Not enough to give
1:1 on super stinkers or S2S airplanes. However, the BPE M14P we use
dynos at over 400hp and makes 1850 lb static thrust with the 102" dia Mt
prop.<<
Kevin,
I found some Youtube videos of those airplanes. There weren't a lot of hovering moments in them but I could see the airplanes were pretty much staying at the same altitude. They looked similar to the Sukhoi I saw at Lakeland in 2003. The Sukhoi was right on the edge and did tend to settle if the airplane was truly vertical. If it was flown slightly positive of vertical it did a better job of holding altitude (better inflow to the prop?).
We designed a biplane in 1984 that started out as an attempt to built a legal ultralight that was fully aerobatic. That goal was missed because of the stall speed requirement but the airplane flew well and we headed toward a 1:1 thrust to weight ratio so we could hover, at least briefly. As originally built we had 440 lb of static thrust and a gross weight of around 500 lb. Tantalizingly close.
We hopped up the engine using snowmobile technology and gained some thrust but the engine had such a narrow torque window that it wasn't practical for aircraft use. We put Nitrous Oxide on it and that added some thrust and a bit of weight -- and we still didn't get there. Plus the system was pushing the limits of what you could throw at the engine at it eventually backfired on takeoff and bent the butterfly in the carb.
We felt like we needed more engine and that added weight along with adding thrust. The airplane needed to be beefed up structurally and that also added weight..... We never got to our goal but we made a heavier and unreliable airplane out of what was a nice light and fun to fly machine.
One thing we learned was that to get a really hover-capable airplane, you needed more than 1:1 static. There are loses in hovering flight that take the ratio down to the point where 1:1 won't let you hover. Of course our dream was to be able to accelerate while in a hover and fly out into level fight. We figured you would need to pull the throttle back to do hammerheads, etc. I don't know what the target should have been but I'd guess 1.25:1 would be close to where we needed to be.
One video I found has Ben flying and he did a series of half loops and 1½ rolls. That is similar to my opening maneuver for the airshow sequence in our little biplane; takeoff, half roll to inverted, half outside loop, repeat. That worked well, even in the airplane's original form but I was only gaining about 100 feet per loop (4 lb wing loading and 80mph entry speed). Ben was doing much better than that......
Are any of the three airplanes you mentioned flying airshows in Florida? I wouldn't mind seeing what they're capable of in person.
Edited by: cwilliamrose
