If my memory serves me right T6NL is an dual purpose warning light/attention getter:
T6 is for the turbine temperature out of limits (too hot = melting the turbine, too cold = your engine has stopped)
NL = number of revolutions (in percent RPM) of your low pressure turbine out of limits. Adour has 2. Low pressure & high pressure (NH)
So if you are a Hawk mate then it makes as much sense as "gear not down" really
HH2