Getting Ready for AirVenture
Hey folks. We have been working on the plane to get her flying, but are running up against a hard stop this weekend. We have to disassemble her and load her into our car hauler trailer. We have not flown her since Elliot Seguin made the first two flights. We had some issues and they needed fixin’.
The main issues:
Overspeeding the engine. We have adjusted the propeller for 2 more degrees of pitch and this dropped the max static from 2050 rpm to 1950 rpm. We need to fly her to see how well we did. Max rpm is 2380 for three minutes, then 2000 for continuous duty.
High cylinder head temperature. We did two things. First, we re-jetted the carburetor for more fuel in the intermediate jet. This helped across the throttle range. We may up-size it again depending on how we do with issue #1. Second, we have fabricated inter-cylinder baffles and are installing them. I wanted to see how well the engine cooled with our initial setup before adding them in. Well, it didn’t work out so well. So they are going in. Should help a lot with head temperatures. Final fit-up and then painting them this weekend.
Oil blowing out the breather vent tube. We were getting some of this during ground runs and was thinking we had too much oil in the tank. Like my Lycoming if you fill it all the way to 8 qts. We leave it at 6 and it doesn’t go all over the belly of the Grumman Cheetah. Was never enough to worry me for flight testing. However, we lost 2.5 quarts in just 10 minutes of flying. Granted, Elliot was trying to climb and was at high throttle settings for most of it. It finally lost so much that the oil pressure dropped to barely anything. He had to land it. This is a huge safety of crew and machine issue. We have been conducting ground tests and getting crazy weird results. We disconnected the 3/8” drain tube from the separator with the idea that it was a small hose and back-feeding oil into the separator - and that didn’t solve it. We tried various extensions and fittings on the end of the breather tube. Nope. We cured the issue when we added a 2ft long x 1-1/2” diameter hose to the oil tank filler neck and routed it up the firewall and left it open on top. No more oil blowing out. As soon as we covered the end of the big hose, oil was blowing out again. We tried to measure the pressure in the oil tank head space, but our pressure gage wouldn’t read it or there was no pressure. Don’t make no sense. Steve Wolf has been sending us information and images of what he did - and it works fine. So we may have to follow suit . Unfortunately, it would mean removing the oil tank and modifying it or making a new one. Not something we have the time to do before Oshkosh. Dang it!
The pitot system was leaking and we were getting low readings on the airspeed indicator. We found that it was the instrument itself that was leaking and since we needed a few more kts on the indicator for VNE and dive speed testing, we ordered a new instrument. It just arrived and I will install it this weekend.
No airspeed results to publish - due to #4. This is a huge problem for us and we will get it done as soon as we can. I can tell you what we were getting, but remember - it was low and we have no way of knowing if it is consistently low by a percentage, or if it increases or decreases the faster we go. We just can’t extrapolate anything from the flight data. Elliot took off and climbed out at 100 kts indicated. 500 fpm. max speed attained was 115 kts. On the second flight, he climbed out at 80 kts indicated and was seeing 1000 fpm. Again, this was reading low so he may have been actually climbing at 95 kts and way above the best rate of climb speed for the aircraft. Elliot wanted to climb to 5,000 ft and do some stalls to see what speed that would be indicating at. The over temp and then the oil pressure issues prevented any stalls from being done.
We have a whole testing regime to do and will post everything openly. Not trying to hide anything here. We have been knocking out the issues and trying to learn as much as we can. We are getting a lot of good advice from the experts - so I am sure we will get it fixed. We are just running out of time.
There are a bunch of things we still need to do to get ready for AirVenture 2022. Since we have to trailer the plane, we can’t bring the camper. So we are turning the car hauler into a camper for the week. Ton’s to do for that. Then we have to finish and paint the baffles and get them in before we tear the plane apart to put it in the trailer. Scott is working on a first flight video - posting shortly. We are also making brochures and signage. Planning to hit the highway on Friday the 22nd. Arrive on Saturday afternoon. Setup on Sunday morning. Fingers crossed!
