Originally Posted by eflight-ray
There are too many variables to hazard a guess at flight time. Someone may guess on a percentage less flight time than on a 'normal' flight. But it would still be a guess.
I could depend on how charged the packs are, how long they have stood for, how cold the packs are, how much additional power is used, etc etc.
What's the twin ?, if it wont glide, (it won't really fly dead stick or power reduced), I can only assume it has a lot of drag, or horrendous wing loading.
I fly twins, (and a fours), and as there is always that risk of one motor cutting before the other I get a feel for when the motors are staring to loose their edge as the volts start to drop. Then it's gentle flying and start the landing circuit.
During the winter, try to keep Lipos warm, something like an insulated box or bag. Lipos loose their edge quicker if flown cold.
It is a Cessna 310 with 55" WS and about 38 ounces. It is pretty lightly loaded but when it goes dead stick I feel like I am running out of elevator for sure. I was pretty conservative at the field that last time out and every one else was complaining about loosing power and battery capacity. However I fly a lot and I keep my batteries ready, fully charged and don't leave them sitting around to discharge. I fly them down to about 30-35% capacity and then recharge and every once in a while I do a controlled discharge, balance and recharge.
I am just being careful since I have had a long run without crashes and the planes I am building now have a lot of time invested in them.