B400 ground effect at hover...

[HeliMix]

When hovering with the B400 (may be the same with other helis but I figure due to the diff in rotor blade lengths it would vary), how high (in imperial measurement not metric) do you have to be above the ground before you no longer feel the ground effects?

[LockMD]

No expert, but I'm guessing 3 feet. What does everyone else, say?

[Heli Jim]

The general theory is that ground effect distance is equal to rotor diameter.
With airplanes, it's generally figured as the wingspan.

This may not be a "perfect" distance but it's awfully close.

[HeliMix]

No expert, but I'm guessing 3 feet.

The general theory is that ground effect distance is equal to rotor diameter.

Cool. Thanks guys. That is about what I was guessing. In Sokal's hover vid, he does not mention it specifically, but his hand motions (not sure if they are intentional) reflect that distance roughly.

[LockMD]

The general theory is that ground effect distance is equal to rotor diameter.
With airplanes, it's generally figured as the wingspan.

This may not be a "perfect" distance but it's awfully close.

So on my B400 with x-400 plastic blades its about 2 feet

And with the MONSTER soon to be maidened will be 4 feet - wow that makes it even more scary! :wow2:

[HeliMix]

MONSTER soon to be maidened will be 4 feet

Sweeeeet! :Bang

[sokal]

GROUND EFFECT
When hovering near the ground, a phenomenon known
as ground effect takes place. [Figure 3-7] This effect
usually occurs less than one rotor diameter above the
surface. As the induced airflow through the rotor disc is
reduced by the surface friction, the lift vector increases.
This allows a lower rotor blade angle for the same
amount of lift, which reduces induced drag.

[HeliMix]

GROUND EFFECT
When hovering near the ground...


It has been said before and will be said again Im sure, Sokal, you da man! ;)

[skigolfmike]

Ground effect is neat. Sometimes.:roll:

I was looping, flipping, rolling and pirouetting. Went well until I decided to try some tic-tocs. I ticked, but I sure as heck didn't toc. Got completely out of control 3 mistakes high and running out of mistakes fast. Just before turning my B400 into a lawn dart, I got it into a nose in, upright position about 10' up still descending at a very high rate. We're talkin' the crash is imminent. Well, I know what to do with that, full throttle and positive collective. It recovered in ground effect as the skids just touched the grass. Bounded up to about 20' and I got a chance take a breath. I figure it recovered in ground effect - it looked like it rebounded off a spring.

This time ground effect was good. If my B400 had impersonated a lawn dart, that ground effect would have been bad.

[LockMD]

I've hear that practice "fly three mistakes high" if I were to do that, I would not be able to see it. :)

[skigolfmike]

I've seen your back yard, you're luck if you can get 1/2 a mistake high. 3 mistakes high is about 20' right;)

Actually, I was higher than 20', probably 40' or so. If I had been a few inches lower I would have crashed for sure.