FAA INSPECTOR FOUND COOLING FAN CIRCUIT BREAKER PULLED DURING COCKPIT INSPECTION.

Narrative

DURING GND OPS OF THIS FLT A CB FOR A COOLING FAN WAS PULLED. THIS FAN WAS DESIGNED FOR AN MLG WITH THE GLASS COCKPIT. OUR MLG HAS A STANDARD COCKPIT. WITH THE FAN RUNNING IT IS ALMOST IMPOSSIBLE TO HEAR IN THE COCKPIT. THE FAN DOES NOT RUN DURING FLT. THE AIRLINE IS MODIFYING THESE ACFT TO REMOVE THIS UNNECESSARY NUISANCE TO NORMAL OPERATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THIS FAN CAUSES A LEVEL OF NOISE THAT APPARENTLY CAUSES FLT CREWS TO SNAP AT ONE ANOTHER AS A RESULT OF NOISE INDUCED STRESS. RPTR HAS EXPERIMENTED WITH FAN ON AND OFF AND FOUND HE CAN CTL A LEVEL OF STRESS IN THE COCKPIT. ALSO; THE FAN IS CTLED BY THE NOSE GEAR SQUAT SWITCH AND TURNS OFF THE INSTANT THE NOSE GEAR LEAVES THE GND. RPTR SAYS THIS IS A POOR TIME BECAUSE AS THE FAN STOPS; THE FLT CREW WONDERS WHAT HAS JUST QUIT WORKING; EVEN SUSPECTING THE LOSS OF AN ENG. HE ALSO SAID THAT AT LEAST 4 OF THE 6 ACFT OF THIS TYPE HIS AIRLINE OWNS HAVE BEEN CONVERTED AND THE FANS HAVE BEEN DISABLED. IT SHOULD NO LONGER BE A PROB ON HIS AIRLINE. HE THINKS THIS NOISE CAUSES A SUBLIMINAL BUT PROFOUND EFFECT ON HUMAN FACTORS AND FLT CREW PERFORMANCE. FAA ACI DISCOVERED CB PULLED ON COCKPIT INSPECTION.