L/D of Virgin Atlantic GlobalFlyer

For a gerneral overview, look here at a phantastic NASA report:

Just found on an other site (http://www.luftpiraten.de/glos_g32.html):

Wright Flyer 8.3
Cessna 172 10

Now that's what I call progress!

Stefan

In article ,
Martin Gregorie wrote:

BTW I agree it would be interesting to see how it performed as a glider.
Let's see now:
- restricted vis - I wouldn't want to share airspace with it
- it might run a cloud street, but could it turn tight enough to
core a thermal?
- with a design cruise of 250kts, it may be too fast to use
anything but wave or ridge lift.
- Anybody fancy running the Appalachians in it? A two hour 750
should be on in theory.

The 250 kts is TAS, at altitude. IAS VNE is 170 knots, similar to
modern gliders.

We also know that empty it has about the same wing loading as typical
gliders, and so presumably about the same stall speed and turning
circle. Note that fully fuelled, at which it has six times the wing
loading it has empty, best powered climb is at 100 knots dirty, 130
knots clean. The corresponding speeds with empty tanks will be 2.4 -
2.5 times lower, or 40 knots and 53 knots. So min sink empty probably
lies somewhere around this range.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

did he run bug wipers??

Bruce Hoult wrote:
In article ,
Martin Gregorie wrote:

BTW I agree it would be interesting to see how it performed as a glider.
Let's see now:
- restricted vis - I wouldn't want to share airspace with it
- it might run a cloud street, but could it turn tight enough to
core a thermal?
- with a design cruise of 250kts, it may be too fast to use
anything but wave or ridge lift.
- Anybody fancy running the Appalachians in it? A two hour 750
should be on in theory.

The 250 kts is TAS, at altitude. IAS VNE is 170 knots, similar to
modern gliders.

OK, not as fast as I thought, then, but could still be fun in wave or on
a ridge.

We also know that empty it has about the same wing loading as typical
gliders, and so presumably about the same stall speed and turning
circle.

I'd agree about the speed, but doesn't turning circle also depend in
control surface size and deflection range?

Note that fully fuelled, at which it has six times the wing
loading it has empty, best powered climb is at 100 knots dirty, 130
knots clean.

Not good to winch with full ballast, then.

--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

On the global flyers website, it says that it was sensitive
to turbulance, at it might cause structual failure
(certainly whilst full of fuel anyway!) so maybe a
bumpy ridge or rotor may not be that fun...!

It certainly looks better than ETA though.

Martin Gregorie wrote:
I'd agree about the speed, but doesn't turning circle also depend in
control surface size and deflection range?

No. More control will just enable you to get into and out of a turn faster,
but it has no influence on the turn radius itself.

-Gerhard
--
Gerhard Wesp
Zuerich, Switzerland
+41 (0)76 505 1149 (mobile)
+41 (0)44 668 1878 (office)

Gerhard Wesp wrote:
Martin Gregorie wrote:
I'd agree about the speed, but doesn't turning circle also depend in
control surface size and deflection range?

No. More control will just enable you to get into and out of a turn faster,
but it has no influence on the turn radius itself.

I'd agree for ailerons and rudder, but I think that in a steeply banked
turn elevator deflection can limit the turn radius. Of course that's
only the case if there's not enough deflection to cause a stall at the
turning bank angle.

I'd further suggest that if there's not enough aileron and rudder
deflection for fairly crisp manoevering it all becomes academic if the
plane can't turn sharply enough to get into the thermal in the first place.


--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot