MLG TAXIES INTO THE MUD DURING A PWRBACK FROM THE GATE.

Narrative

PWR BACK TAXI FROM GATE INCIDENT IN WHICH L MAIN GEAR ROLLED FROM HARD SURFACE TXWY ONTO SOFT GND AND SETTLED. NO DAMAGE TO ACFT OR INJURY TO PAX OR CREW. HOWEVER; SETTLING OF L MAIN GEAR PRECLUDED ACFT FROM CONTINUING TAXI UNDER ITS OWN PWR. ACFT WAS THEN DEPLANED; DEFUELED PARTIALLY AND SUBSEQUENTLY TOWED BACK TO HARD SURFACE. FOR THE FLC; A PWR BACK IS A BLIND REVERSE TAXI MANEUVER DURING WHICH DIRECTIONAL GUIDANCE COMES EXCLUSIVELY FROM A GND MARSHALLER. THIS INCIDENT RESULTED FROM THE MARSHALLER'S USE OF CONFUSING AND NONSTANDARD SIGNALS AND THE CAPT'S FAILURE TO IMMEDIATELY STOP ACFT'S REARWARD MOVEMENT WHEN CONFUSION BECAME APPARENT. DURING THE PWRBACK THE FLT ATTENDANTS WERE STANDING PERFORMING THE SAFETY DEMONSTRATION AND FOR THIS REASON THE CAPT WOULD WANT ANY DIRECTIONAL TRANSITION OF THE ACFT TO BE VERY SMOOTH. WERE IT STANDARD PROC TO HAVE THE FLT ATTENDANTS SEATED DURING PWR BACKS THE CAPT MIGHT HAVE MORE EXPEDITIOUSLY STOPPED ACFT'S REARWARD MOVEMENT ALLOWING ACFT TO REMAIN ON HARD SURFACE. RECOMMENDATION: WHILE I WOULD EMPHATICALLY NOT FAVOR ANY FAA PROHIBITION OF REVERSE TAXI OPS I WOULD RECOMMEND TO ANY INDIVIDUAL AIRLINE OPERATOR THAT THIS PRACTICE BE DISCONTINUED BECAUSE OF THE INHERENT PROBS ASSOCIATED WITH ANY BLIND MANEUVER.