Question for whirlybird drivers

[[email protected]]

When reading performance specs for helicopters I see the terms IGE and
OGE. I understand they are in ground effect and out of ground effect,
but when the altitudes are given they don't make sense to me. I thought
ground effect was up to one-half the rotor span and anything above that
would be out of ground effect. So what is the difference between hover
ceiling IGE and OGE?

[Matt Barrow]

> wrote in message
oups.com...
> When reading performance specs for helicopters I see the terms IGE and
> OGE. I understand they are in ground effect and out of ground effect,
> but when the altitudes are given they don't make sense to me. I thought
> ground effect was up to one-half the rotor span and anything above that
> would be out of ground effect. So what is the difference between hover
> ceiling IGE and OGE?

You can hover at a higher altitude in ground effect than out of GE and your
service ceiling is going to be higher still.

Say, for example, ceiling is 15,000, HIGE is 8000 and HOGE is 6000.

Realize that hovering takes a lot more power/fuel than cruising does.


--
Matt

---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[Mike Rapoport]

A helicopter can maintain a higher altitude in "clean" air. When it hovers,
it pushes the air down and to maintain altitude it has to "climb" through
this decending air. This effect is strongest out of ground effect. What
this means is that, if the IGE ceililng is 12,000 and the OGE is 8,000" the
helicopter could hover over 11,980' terrain at 12,000' but could only hover
at 8,000' over 7900' terrain.

Mike
MU-2
> wrote in message
oups.com...
> When reading performance specs for helicopters I see the terms IGE and
> OGE. I understand they are in ground effect and out of ground effect,
> but when the altitudes are given they don't make sense to me. I thought
> ground effect was up to one-half the rotor span and anything above that
> would be out of ground effect. So what is the difference between hover
> ceiling IGE and OGE?
>

[[email protected]]

Mike Rapoport wrote:
> A helicopter can maintain a higher altitude in "clean" air. When it hovers,
> it pushes the air down and to maintain altitude it has to "climb" through
> this decending air. This effect is strongest out of ground effect.

Same effect that a fixed wing airplane has: the tip
vortex is large enough to curl around and get into the top of the rotor
on a helicopter, and around the wingtips of a fixed-winger. This
decreases the angle of attack on the affected area and reduces lift.
The helicopter's hovering vortex is ring-shaped, like a doughnut. The
helicopter has another, smaller vortex on the inboard area, too,
curling up next to the mast and into the top.
The air movement extends out a long way, so that near the
ground that movement is hampered, the vortex gets smaller and drag
decreases, angle of attack increases, and lift increases.

Dan (a helicopter pilot wannabe)