Merlin III
Air Traffic Control Fully Certified
Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
Human Factors
A SW3 checked on and I instructed the pilot to expect Visual Approach. I gave descent to 080. At approximately 35 miles north of the airport; I issued the vector of 'fly heading 160 vector to final approach course; descend to 070.' The pilot read back descend to 060; fly heading 180. I corrected the heading but did not hear the incorrect read back of altitude. I noticed the aircraft below 070 when it was at 067 and descending; I called out to the aircraft to maintain 070. No response and I again tried the aircraft with another failed attempt on the second. I believe on the third I just used the full call sign and no instructions; the pilot acknowledged and I instructed to maintain 070. He said he was issued 060 and was climbing back up to 070. The area that the aircraft descended through was a 070 foot MVA. No further incident occurred other than going below the MVA by 010 feet.
TRACON Controller described a below MVA entry event when failing to note an incorrect altitude assignment during the clearance read back.