Randall Clague wrote:
At 01:51 PM 9/16/2005 -0700, Greg Retkowski wrote:
At one point ISSI was touring and doing taxi tests with their PDE
demonstrator attached to a long-ez: http://www.innssi.com/pde.aspx
Their engine weighed 800 lbs, and had 150 lbs of thrust. Those
numbers need to be inverted for the engine to provide adequate flight
power to a long-ez.
That would be about 800 lbf of thrust. That's the design point for
the EZ-Rocket. That's a *lot* of performance for a Long-EZ. Even one
400 lbf rocket engine provides more than enough power to fly a
Long-EZ. With two, you have to be careful not to overspeed the aircraft.
150 lbf is in the neighborhood of what the smaller Long-EZ piston
engine (Continental O-200, IIRC) puts out. It would be enough to fly
on if they didn't have a) all that weight requiring more power to lift
and b) all that drag from the supporting plumbing hanging
For an EZ they are spec'd for a lycoming O-235 (O-200's are what the
lighter vari-eze are usually powered by). Nowadays most folks put a
O-320 in their planes. The O-235 is about 115 HP, the rule of thumb for
static thrust for prop planes is 5x horsepower, so the smaller engine on
these planes put out 575 lbs of thrust. O-235 weighs ~260 Lbs, add say
another 40 pounds for accessories and a prop. Doing the math on the
O-320 it's approaching 800lbs.
If they were to take some basic measures to reduce drag, they'd have a
chance of getting that thing in the air. If they reworked the support
plumbing to be half the weight, they could certainly fly under their
own power.
Yeah, it seemed to me there was an awful lot of support hardware for
that PDE. I hate to second guess because I don't know what's down there;
but surely the pressurized induction system, fuel/ignition management,
and all the rest of the supporting hardware have some room for paring down.
And for Pete's sake, no more engine runs at 10:00 at night. Not on an
engine that's annoyingly loud a mile away (God's Leaf Blower) when one
of the Airport District Board members lives three blocks from the wash
rack.
Probably not the most prudent choice. Have they done any more testing
since 2004?
-- Greg
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