What was found
(CAN) APPROX. 10 MINS AFTER TAKEOFF UNUSUAL LOW WHISTLING SOUND NOTICED BY ONE OF PILOTS, FOLLOWED SHORTLY THEREAFTER BY NR 2 SERVO WARMING LIGHT ILLUMINATING & NR 2 HYDRAULIC PRESSURE CYCLING BETWEEN 1000 & 3000PSI. SWITCHED OFF #2 SERVO SWITCH AT WHICH TIME HYDRAULIC PRESSURE IND. RETURNED TO NORMAL (INDICATIVE OF LEAK AFT OF SERVO SHUTOFF VALVE. EMERG CHECKLIST FOR "LOSS OF HYD. PRESSURE" PREFORMED. PILOTS REVERSED COURSE&CARRIED OUT PRECAUTIONARY LDG W/O INCID.. POST FLT INSP REVEALED FLUID LEAKING OUT OF BELLY AREA AFT OF BAGGAGE COMPT & NR 2 HYDRAULIC RESERVOIR BELOW MIN.LEVEL. MAINT INVEST. FOUND FLUID LEAK FROM PINHOLE IN NR 2 TAIL ROTORPRESSURE TUBE. TUBE REPL ALONG WITH HYDRAULIC PUMP DUE TO