Posted by JamesB on Wednesday, May 6, 2009 @ 11:50 AM:
For the typical RF5B owner (this excludes Rudy with his ship that climbs like a rocket), climbing in the RF5B at high density altitudes can be entertaining....or the cause of white knuckles depending on what you're seeing through the canopy.
My RF5B usually climbs well to 800-1000' -- but can climb at a leisurely pace after that. If I am trying to make altitude to fly over nearby mountain passes, this is no small challenge -- especially in hot weather. If you just engage the climb prop, you just overheat the engine.
The following formula seems to work.
With the prop in cruise pitch:
- increase rpm's to 2,800.
- trim the glider for max level speed.
- now add upward elevator trim.
- apply gentle forward pressure on the stick so you keep 78-82mph
This get's you enough speed to keep the engine cool. You're not getting on the back side of the power curve. In fact, you're almost keeping it level -- but the upward trim gets you a steady climb.
I find that depending on the actual temps, glider CG and the Humor of the Gods for that day -- the specifics will vary a bit to get the best climb. But the basic technique works. It's the only way I've gotten a steady, reliable climb for thousands of feet without overheating the engine.
Good luck.
Posted by Donald on Thursday, May 7, 2009 @ 08:00 AM:
That seems counter intuitive to me. Is the forward pressure on the stick not just opposing the upward elevator trim, or am I missing something? Brings to mind the old saw about trim tabs, "a simple mechanical device that can fly the plane better than the pilot".
Posted by Mike-RM on Sunday, May 10, 2009 @ 04:13 AM:
Hi James
Do you use mountain soaring techniques to gain height? When we flew in the Alps during CFI World Days we experienced really powerful anabatic lift by flying in the right places - climbed from 6000 to 10000 feet in 4 minutes on the into-sun mountain face with just cruise power! You do have to tuck in close to the rock in the right places though, which may come as a bit of a shock to non-glider pilots without ridge soaring experience, and it doesn't always work. I'm aware that there are some pretty vicious downdrafts as well in mountainous areas so you have to know what you're doing.
[Edit by Mike-RM on Sunday, May 10, 2009 @ 04:13 AM]
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Posted by JamesB on Friday, May 15, 2009 @ 03:04 PM:
Whenever possible. What I'm referring to is a technique that can help if it is just a warm, high pressure day with little useable lift from surrounding terrain.
There are days when the RF5B won't climb hardly at all with simple aft stick pressure. You, in effect, get behind the power curve too easily. Forward pressure keeps the glider level and on the front of the power curve. The upward trim lets you climb.
When I described this to one fellow, he laughed and said that's an old airplane racing technique. It let's the racers both climb and maintain maximum forward speed & cooling. (So it seems that this is likely nothing "new."
