Aircraft suitable for zero g flight

[David Findlay]

I'm interested in learning to do a zero g manueveur as part of my aerobatics
training. I get the idea that this would require certain characteristics
from the fuel system, i.e. the fuel still needs to flow into the engine in
zero g. Will a standard fuel pump system as provided in aerobatic aircraft
be capable of handling this? Liquids in zero g have a tendancy to form
spherical bubbles that just float around, although surface tension still
works.

As for method of doing it, I would expect the best method is the old NASA
method of hanging a small weight from the compass, if the weight goes down
push forward, if the weight goes up pull back. Anyone done it? Thanks,

David

[ShawnD2112]

David,
Depending on what you want to do, you may be thinking about this too hard.

How long do you want to be weightless? Zero G is accomplished by flying a
downward parabola, so it eats up altitude. Unless you're going to start at
10000 ft AGL, you're not going to have a great deal of time in zero G in any
case.

I do zero G maneuvers in a Taylorcraft all the time, for probably about 5-8
seconds at a time. Wouldn't bother hanging anything from the compass. Put
an object (logbook works fine) on the dashboard. Push over until it floats
up off the dashboard. Level off, climb back up, repeat. Great Fun!

Shawn

"David Findlay" > wrote in message
...
> I'm interested in learning to do a zero g manueveur as part of my
> aerobatics
> training. I get the idea that this would require certain characteristics
> from the fuel system, i.e. the fuel still needs to flow into the engine in
> zero g. Will a standard fuel pump system as provided in aerobatic aircraft
> be capable of handling this? Liquids in zero g have a tendancy to form
> spherical bubbles that just float around, although surface tension still
> works.
>
> As for method of doing it, I would expect the best method is the old NASA
> method of hanging a small weight from the compass, if the weight goes down
> push forward, if the weight goes up pull back. Anyone done it? Thanks,
>
> David

[Peter H. Schmidt]

You can reduce altitude loss by pitching up at the beginning of the
maneuver. In the Pitts, I pitch up to about 50 degrees above level,
establish a climb briefly, and then push the stick forward until the G
meter shows 0 and ride it to 45 dgerees nose low or so, then pull to
recover. I picture the arc of a lobbed baseball, and try to fly that.

While zero G is within the G envelope of every aircraft, the risk with
this maneuver is the nose-low attitude at the end. Airspeed will
build, and could cause overstress on the recovery if not managed
properly. And there is also the issue that non-aerobatic aircraft may
not have fuel and oil systems that tolerate zero G well.

Less of an issue with acro aircraft, but they still may experience oil
starvation from what I have been told. The ball valves in a Christen
inverted system, for example, won't be pulled all the way to either
end, and one rule of thumb I've read is to spend 10s or less at 0 G,
at knife edge, or on a vertical line.

ObDisclaimer: Try it with an instructor first. Don't exceed Vne,
Don't pull the wings off. Don't ruin your engine. I am not a flight
instructor, and this is not flight instruction!

Regards -- Peter
--
Peter H. Schmidt `\ /' Burning Blue Aviation Inc.
------^------ 2 Ewell Avenue
www.burning-blue.com | |o| | Lexington, MA 02421
fax: 781 863-8858 ------v------ tel: 781 883-4818
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