ORIGINAL: flymeaway

I'm flying the Spectrum DX-7 with stock Tx pack (1,500 NiMh If I recall correctly). I generally stop flying when the indicator is just above half, or about 9.4 - 9.6 volts. I ask this question for a couple of reasons, one I simply don't know the answer, and two it always seems that I wish I could squeak just one more flight out for the day but choose not to based on the Tx falling below 9.8.

What voltage is too low to fly?

Thanks.