On Wednesday, August 7, 2019 at 7:47:45 AM UTC-4, kinsell wrote:
On 8/6/19 4:33 PM, Bob Kuykendall wrote:
Apparently the gauge said there was 20% capacity remaining.
We all know how reliable aircraft fuel capacity gauges are...

Actually, on electric systems they're quite good.

That's a rather dangerous misconception.
With these cells, the actual amount of energy stored is not easy to estimate.
Quite unlike older cell technology where its easily estimated based on
cell voltage and monitoring of cell performance.
Now one has to know the exact cycle history...

You do understand the difference between electricity and gasoline?

A bit ;-)

In the CT accident, my understanding is the pilot was showing
a sizeable percentage energy remaining when the motor quit.

My Antares drastically under-estimated remaining power with
the motor running, then the estimate came back to reality
sometime after shutdown. Better that than the alternative!
And of course as the battery discharges, the max power available
decreases. Not important in Antares but critical in FES which
has little excess power to start.

With any motor-glider, its foolhardy to ever get in a situation
where you don't have a safe landing option as PLAN A.
That includes during:
- take-off (no short fields departing over woods)
- in-air start (extra time, altitude, and field length needed vs. pure glider)
- in-air cruise (never where complete failure puts you in the trees)

When the motor fails, its easy to execute PLAN A.
Plan B is when the motor keeps running, cause for happiness if not surprise...

FES failures have included spontaneous shutdown due to electronics failure.
No electric system is even close to 100% reliable.
Of course you don't need to ask me how I know that...

Be safe out there,
Best Regards, Dave