FES underpowered for 18m ship?

That is definitely the future and awesome idea Matthew,

Pasi

On Wednesday, September 16, 2020 at 8:34:19 PM UTC+3, Matthew Scutter wrote:
On Wednesday, September 16, 2020 at 4:44:36 PM UTC+2, Darren Braun wrote:
With RC front electric gliders you need a soft brake to keep the prop from windmilling in flight. Is that the same engine-not-running drag referred to here? i.e do today's FES have a failure mode like this?
Yes it does, I have had it windmill from inadvertently hitting the power off rather throttling down first a few times. I have no idea how much drag it really is, but I was able to continue climbing in a thermal while I restarted it to then stop it properly.
What I'd really like to see is the ability to actually recharge the batteries via the propeller brake, imagine prestart after a self launch, waiting for the line to open for an hour at cloudbase, slowly charging back up. Maybe someone can do the numbers on the drag that would be induced to charge at 1kW to determine if that's a totally harebrained idea.

Flight manual again:
3.7.2 Power loss during flight
If power is lost during flight, the propeller will windmill. Push the control stick
forward gently, to sustain the desired airspeed! You can perform the following actions to
try and restore power:
1. Check first if you unintentionally switched OFF the power switch!
Warning: This can happen in gliders that thave the landing gear lever and
the power switch located on the same side of the cockpit when retracting
the landing gear, i.e. LAK17A&B FES.
If this happens, switch power switch ON and adjust the throttle.
Note: On earlier software versions (before v2.13), it was necessary to
reduce throttle bar to zero manually; otherwise motor did not start due to
safety. Motor restarted when the throttle was reduced to zero
New versions (from FCU v2.13) automatically reset the throttle!
2. If the power switch is ON:
• Switch OFF the “Power switch� and the FCU.
• Turn ON the FCU and check for strange behaviour.
• If the FCU has no issues switch the power switch ON and try to start the motor.
The motor starts but behaves strangely under power:
• Stop the propeller from the windmilling with the electronic brake.
• When the propeller stops, switch OFF the power switch and the FCU.
If you are not able to stop the propeller with the electronic brake, you will need to land
with a windmilling propeller. Note: it is not possible to stop the propeller by
reducing airspeed. Try to land on both landing wheels simultaneously, to avoid potential
damage of the propeller.
Note: It is probably better to use a grass runway in good condition if one is
available than a concrete runway. If the grass runway is in bad shape, use a
concrete runway if one is available.
Warning: Try to avoid landing into high grass or similar.
Note: The L/D of a sailplane with a windmilling propeller is reduced only by
a small amount. With enough altitude will have enough time to choose a
suitable landing field.