Was just wondering if it is standard to turn window heat on before takeoff or is it only under certain conditions, because I have noticed from some MD-11 inflight pictures that window heat is not on.Thanks, Dave S

Window heat is normally off until top of descent, where it is places on and in NORM. This is to prevent window fogging during descent. In heavy icing, HIGH window heat may be used. Normally, the window defog is enough during flight, thats why you dont use window heat until TOD.

Window heat is normally off until top of descent, where it is places on and in NORM. This is to prevent window fogging during descent. In heavy icing, HIGH window heat may be used. Normally, the window defog is enough during flight, thats why you dont use window heat until TOD.

The HIGH setting is also used if you expect high humidity conditions... like descending into Bangkok where humidity is always way too high ;)Markus