Using the last 20% of batteries

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Jeffrey Banks

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May 10, 2020, 4:52:14 PM5/10/20
to FES Owners
Hi all

This is a closed group so lets talk about this.

I was wondering about the glider that ran out of electric power in CT

Was the FES control used to clear all messages (I think it is three presses of the button) to
utilize the last 20% of battery power?



Jeff Banks




Luka Znidarsic

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May 11, 2020, 12:41:56 AM5/11/20
to Jeffrey Banks, FES Owners
Dear FES owners,

Please check page 24 of attached manual, for clear understanding how it works automatic shutdown, and that only one press of throttle knob is required to override automatic shutdown. And even if motor is stopped automatically, pilot can start it again, just this action will be written in the FCU memory in the same way as if he would override automatic stop.

I still do not know what happened as I did not received FCU instrument (there is 16GB internal SD card logging about 50 parameters every second when FCU is turned on) or igc file from investigators. Not sure if there was FES bridge installed. In such case there are 6 FES parameters written in igc file from which is very easy to recognize what happened. Investigators contacted me and I give them some information how to check data but there was no further discussion about.

Even when critical voltage - 90V is reached, there is still possible to use motor for at least 5-10 minutes of level flight using about 4kW of power, as there is still 3.2V per cell. Cell voltage curve drops quickly only below 2.8V per cell, so there is still some reserve of energy, which can be used for level flight. Climbing requires much more energy. So higher power setting should be avoided below 95V.

Regards,

Luka



-------- Izvirno sporočilo --------
Od: Jeffrey Banks <j...@mtaonline.net>
Datum: 10. 5. 20 22:52 (GMT+01:00)
Za: FES Owners <fes-o...@googlegroups.com>
Zadeva: Using the last 20% of batteries

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FES FCU INSTRUMENT manual v1.82.pdf

Jeffrey Banks

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May 11, 2020, 1:38:56 AM5/11/20
to FES Owners
Luka,
Thanks for the update and clarification.   I thought 1 button push to clear yellow caution then a 2nd to clear red warning and a 3rd to stop the 30 second shut down.
I must of been reading into the manual.  It is good it only takes 1 push to get the emergency 20%

The final report has not been published. 
It would be nice to see a report on the recovered data.
I would expect you to see it first.

Sincerely
Jeff Banks
Alaska USA
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