Flying at altitude question

[MrGrey]

I live near Chicago and we are at 600 ft. I know that I should know this but would i expect to be able to fly in Utah with a base elevation of 4500' with my gyrobee. I have 65hp and am using 23' DW's. I am around 450lbs totally loaded. What kind of performance could I expect?

[Bill Clem]

Expect to be sitting on the tarmac, sipping a cool drink during the Summer. Preferably one with a little umbrella in it. Making vroom-vroom noises. No, really it's possible but you will have to fly early in the morning, oh, about 0dark30.... when it's nice and cool. And expect long takeoffs and marginal climbouts. Is that 450 lbs with pilot and fuel?

[gyro-3xio]

Bill,
Now I'm curious.
What's the service ceiling of a Gyrobee?

Jim.

[gyropilot]

Matt,

I can answer this one...

My GyroBee weighs about 525 pounds fully loaded ready to fly. It has 23' Dragon Wings, a 50hp Rotax 503, 2.58:1 gearbox, and a 60" 3-blade Ivoprop.

For comparison, when close to sea level on a standard day it climbs at 600-700 fpm maximum at full power.

Every year over Labor Day weekend I take it to south-central Oregon where I fly it from a huge dry lake bed at 4100' MSL. I've flown it at all times of the day and in all wind conditions... temps are typically in the 90's F on the lake bed late in the day with dust devils and powerful (sometimes scary) thermals.

Under the worst case conditions (late afternoon) I experience l-o-n-g takeoff runs and at best see a 300 fpm climb rate at full power. I do spend a lot of time nearly at full power. It's still manageable and fun if I just stay way ahead of the aircraft. If strong downdrafts are present (which exceed my GyroBee's available climb rate) I keep enough altitude to prevent being sent to the ground!

As to service ceiling, one day a couple of years ago I decided to find out.

As I recall, the temp on the lake bed was about 75 and I had 5 gallons of fuel on board, so my Bee's flying weight would have been about 500 pounds. The initial climb rate was about 300 fpm. I climbed at full power (trying various airspeeds) until I'd ultimately reached 8000' MSL where the climb rate had deteriorated to 100 fpm. The view was breathtaking!

At that point I throttled back to idle for a few seconds, then turned the engine OFF completely. I glided all the way back down to the lake bed for a dead stick landing... it was a thrilling ride with a very high descent rate.

So if your GyroBee has 23' Dragon Wings, a 65hp engine, and only weighs 450 pounds in the air, then based on my experience you're not going to have any problem at all! Just be very cautious and always leave yourself an out in case you can't climb out of a difficult situation.

Best regards,

John L.

[gyro-3xio]

John,

If you are in such a down draft,... couldn't you just "power out of it?"
I.e. straight and level and max thrust, or even, if you still have the height, slight nose down and apply thrust?

The reason I ask, does this have something to do with the fact that the gyro plane could be so light and you get tossed around like a leaf.

Sorry for such a stupid question. !!!

Jim.

[Bill Clem]

It's all in the numbers... 90 degrees Fahrenheit, 4100 ft asl works out to be slightly over 7600 ft density altitude. Some AWOS's report density altitude. Otherwise you can work it out based on accepted formulas or charts. Another factor to consider is your prop pitch. I pitch my prop so the engine doesn't overspeed on an average day. But on a high DA day, more pitch can be helpful. I run 25 ft blades most of the time, they are more responsive, seem to fly tighter. But when the DA's start to hit 10,000 ft, the 27's go on. I have flown in and out of Leadville, CO in the Summer where DA's can hit 14,000 ft or higher. Density altitude can bite you in the ass and wobbling your way into the air is a hell of a time to find out. Just be careful and explore the edges of the flight envelope very carefully.

[MrGrey]

Thanks for the info guys! John, i can appreciate your post and think that I should have no problems at all then. I climb easily over 1000 fpm on a nice 80 degree day with my air cooled 65 hp. I guess if i do this trip with my buddy i can expect to at least get off the ground in the morning and I will see what kinda DA the day brings.

[gyropilot]

If you are in such a down draft,... couldn't you just "power out of it?"
I.e. straight and level and max thrust, or even, if you still have the height, slight nose down and apply thrust?

The reason I ask, does this have something to do with the fact that the gyro plane could be so light and you get tossed around like a leaf.

Sorry for such a stupid question. !!!Jim,

As Bill Clem inferred, it's all in the math...

If an aircraft encounters a column of air descending at 500 fpm, and the aircraft is only capable of climbing at 300 fpm (for whatever reason), then that aircraft will continue to *descend* within the column of air at a 200 fpm rate until it A) contacts the ground, or B) it exits the descending column of air!

Out in the high desert I've flown my GyroBee in rising columns of air so strong that I could almost throttle back to idle in order to keep from gaining altitude. It's kind of scary sitting there with the engine nearly at idle, the nose of the gyro pointed steeply down (weathervaning into the relative wind), and yet the gyro is still climbing!

Well what goes up must come down.

At some point the gyro will fly out of the rising column of air and into a column of descending air. It's a rapidly descending column of air that can get dangerous in a high density altitude environment when close to the ground. That's where plenty of altitude is your best friend... that's if you want to stay off the ground. :)

Does that all make sense?

John L.

[gyropilot]

I guess if i do this trip with my buddy i can expect to at least get off the ground in the morning and I will see what kinda DA the day brings.Matt,

Depending on what your friend is flying, probably the worst thing which will happen is you'll have trouble climbing as fast as he does and keeping up with him.

At that dry lake bed in south central Oregon last year I went on a little cross-country trip with a friend who flies a trike. He has the same engine, gearbox, and same size prop. He typically likes to cruise along at about 45 mph, but despite our 6500' MSL altitude, his engine rpm was only about 4800. Contrast that with my GyroBee's engine running closer to 6000 engine rpm while flying alongside him. The net result was my trike friend had plenty of extra power to rapidly climb and explore the surrounding mountains alongside our route, whereas all I could do was pretty much just watch him have fun while I concentrated on holding altitude!

As Ken Brock was fond of saying: "Gyros are very draggy devices."

John L.

[ventana7]

I have never tried to prove this -- but many years ago when my primary flight instructor was giving me a mountain flying course in a Cessna 172 he told me since descending air currents can't go through the ground they are scary but would not actually smash you into the ground but stop descending just before the ground-- of course if they brought you down to trees or something the result would be messy.

Airflow diagrams of microbursts show the air hitting the ground and spreading out like a revers mushroom making upflowing aircurrents on each side of the downflowing air.

I guess I don't have any answers just more things to think about.

Rob