Service Ceiling limitations

[atcmannm]

I live at a field elevation of 5500' and as the service ceiling is listed as 6000', would the margin of error be so small as to preclude this gyro as a viable aircraft for me (obviously on hot summer days, the density altitude would preclude any options to fly during the heat of the day)? My inital thought was the use of slightly larger blades and the rotax 502 and losing weight to weigh no more than say 180 lbs may overcome the limitation. I understand this would take it out of the ultralight range and this may defeat the purpose of the design . All I really need is the option to routinely and safely fly it at 7000' and below. I would appreciate input from the forum.

[gyropilot]

One hot summer weekend last year I had the opportunity to pilot my Bee to 7,800 feet MSL...

I started from a dry lake bed in southern Oregon at approx. 4,300 feet MSL where the OAT was over 90 degrees F. My Bee has a dual-carb Rotax 503, 2.58:1 gearbox, and a 3-blade 60" Ivoprop. I was using a set of 23' Dragon Wing blades and I had the carbs jetted for the temp and elevation of the dry lake bed elevation... but I always err on the conservative (rich) side of jetting, so it wasn't optimal. Takeoff weight was about 535 pounds.

The climb rate at 7,800 feet had deteriorated to about 150-200 FPM at full power and 50 mph. By that altitude the EGT's had dropped to a level that made me decide it wasn't necessary to go any higher, so I came back down.

With more optimal jetting, or altitude compensating carbs, I'm sure I could have continued the climb to around 10,000 feet MSL.

So I don't see why you can't operate a GyroBee at your elevation... albeit at a reduced performance level. I would definitely use a Rotax 503, 24 foot Dragon Wing blades (maybe even 25 if Ernie Boyette recommends them), and keep the takeoff weight as light as possible.

Go for it!

John L.

[atcmannm]

I appreciate the "been there, done that" data.

[smckenna]

My Bee isn't quite stock - Hirth 2706, 3-blade Precision Prop, & 24 Ft Dragon Wings, but I have about 40 more pounds to lift. The Airpark's base altitude is 5000 ft and I saw DA of up to 6500 before I had to shut down for a few of months. Climbed like a rocket...ended up overpitching the prop to limit the developed HP. I think a 503 & 24 ft DWs will do you just fine as long as you stay below 8000 ft. Since you're lighter, you might work fine with 23 footers. Give Ernie a call...his advice is good.

By the way, 24 ft was the longest that Ernie would sell me for a machine with a Bee's weight. And, he made me give blood oath that if the sustained RRPM was below 300, I'd get a shorter set of blades. Luckily, never had the problem, though RRPM was usually around 305. I'll be interested to see how it changes with DA when I get back up in a couple of weeks.

Steve

[Ralph]

The service ceiling for the Bee is not specified. If you read the associated note (#4 on the specifications page), you will note that we have flown the aircraft past 6K MSL and climb performance was still satisfactory. That was with a 447 jetted for 1K MSL. Projection from the Digipod digital flight record for that flight showed that the aircraft could have easily gone past 7K with reasonable performance - the limiting factor being the Part 103 5 gallon fuel limit.

For your situation I would suggest a 503 and 24-foot DWs. Ernie is correct in that the big issue is the rotor RPM. Too big a disc and the speed will drop. Our prototype always flew at about 305 RPM and I would shorten the blades if there was any indication that they would stabilize below 300 rpm.

Ralph