On Thursday, April 16, 2020 at 8:20:37 PM UTC-7, Eric Greenwell wrote:
2G wrote on 4/16/2020 7:18 PM:
On Thursday, April 16, 2020 at 5:51:04 AM UTC-7, Eric Greenwell wrote:
2G wrote on 4/15/2020 11:48 PM:
On Wednesday, April 15, 2020 at 4:10:28 PM UTC-7, Eric Greenwell wrote:
Dan Marotta wrote on 4/15/2020 2:30 PM:
You're right, Tom.

I recall the time we got low over an airport about 60 nm from home. Rather than
land, I started the engine and discovered that we were low on fuel.Â* Rather than
give up, I climbed straight ahead under power, watching the glide back to the
airport, until I had a certain glide home.Â* I had enough fuel, though not enough
to make me comfortable.Â* I now won't take off with less than about 3/8 of a tank,
or about 12 gallons.

On 4/14/2020 7:38 PM, 2G wrote:
When you are flying a motorglider the FAA considers it to be a glider and fuel
reserves don't apply. The point is that planning launches or retrieves w/o
factoring in reserves is a bad idea. You will NEVER get the promised performance
for a variety of reasons. It would be like planning a final glide using the max
L/D.

Tom

Contest pilots often start their final glide even lower than a max L/D glide, when
they know the conditions on the way to the airport have some rising air. Uvalde is
well-known for that kind of planning. I don't think it is always necessary to
factor in reserves, either, as long as you have a safe place to land if it doesn't
work out. That seems to be what Dan did: not enough fuel to provide an adequate
reserve, but a bail-out plan if he didn't get lucky.

I do agree with your point in general, however, which applies to all glider
flying, powered or not.


I don't worry about what "contest" pilots do - they are trying to win a contest. I would NEVER plan a glide at best L/D where the consequences are a crash - and neither should you or anybody else.

Those contest pilots at Uvalde do exactly what you recommend. My point is your
"reserves" do not have to be fuel in the tank or watt hours in the battery - those
are conveniences. What matters is keeping a safe place to land within "easy"
reach. That's what I do, and that's what I've recommended for decades. It's even
documented in my "A Guide to Self-Launching Sailplane Operation" :^)

Even if you have a safe place to land, most of us use, or our glide computers use via a high McCready setting, a conservative glide angle. This works and we know it works (most of the time). This is a basic element of flying gliders safely. Peter Masak died when he violated this basic principal and went down in unlandable territory. It seems like you are taking the opposite side of this very basic principal to somehow justify eking out the last drop of electrical performance from electric self-launchers. I am cautioning against this because it is, basically, bad policy that will, ultimately, end badly.

Look at my paragraph above yours, where I say "...as long as you have a safe place
to land if it doesn't if it work out". Aren't we advocating the same thing?

This discussion about the performance of electric gliders was based mostly on the
manufacturers numbers. NOBODY suggested these numbers can be trusted to be so
accurate you can discard the normal glider pilot cautions about the uncertainties
in what we do. Still, they are accurate enough to make useful comparisons for the
purposes of the discussion. Case in point: You said none of the electric gliders
could run for more than 30 minutes, and I responded with examples of electric
gliders that clearly can exceed that. That's just factual disagreement, not a
recommendation you fly the glider until the motor stops.

Please Read my "A Guide to Self-Launching Sailplane Operation" (link below) for a
better understanding of what I think are good practices for being safe in a
motorglider.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

The 30 minutes was at full power, not a low power cruise setting.

Tom