On Thursday, September 19, 2019 at 3:11:04 PM UTC-4, Andreas Maurer wrote:
On Wed, 18 Sep 2019 15:16:31 -0700, Eric Greenwell
wrote:


I've never had anyone flying the usual PIK, DG, ASH, and Ventus self-launchers
mention plummeting or reduced control authority to me, but I'm sure there must be
some like that. What gliders have this plummet/control authority problem, and how
bad is the plummet (same as half spoiler, full spoiler, etc), and reduction in
control?

Arcus M - you ought to be able to find a operating handbook online.
WIth extended power plant the L/D decreases to 13/1 and minimum sink
rate to 443 fpm.

So far I've seen two DG-400s crash that were trying to land with
extended power plant and didn't reach the runway.

Cheers
Andreas

Some things to consider:

(1) The 'best' sink rate and LD with motor extended are at what speed?
Blue-line is what's quoted for many types, but that's typically much less
than minimum pattern speed, in turn much less than required for safe
round-out from high sink rate.

(2) Drag isn't just prop! In addition to gear doors, there's a
rather large radiator, plus the mast structure and lots of other
bits hanging out in the breeze.

(3) Some models have been fitted with different props over time.
So, your mileage (and plumetting) may vary.

The Ventus 2CM I owned was a real plummeter.
It had significantly reduced pitch and rudder authority
and reduced yaw stability with engine out.
In factory briefing I was warned to be extremely careful not to stall it .
ArcusM engine-out was much less exciting, by far.

I landed both motor out after assorted failures.
The ArcusM was no problem, but the V2CM was pretty exciting.

Hope that helps,
Best Regards, Dave