DOUBLE ACFT EQUIP PROB AND AN ALTDEV ALT OVERSHOT DURING DSCNT.

Narrative

DURING AN IMMEDIATE RETURN TO MCCARRAN INTL ARPT; THE ACFT DEVIATED 500 FT (PLUS) FROM ASSIGNED ALT. OUR CLRNC WAS: PLT'S DISCRETION TO FL240 INITIALLY. WHILE DSNDING TO FL240 WE WERE CLRED TO FL220. THE AUTOPLT WAS ENGAGED AND ALT ENGAGE WAS ARMED IN THE DSCNT. (ALT ARM WILL AUTOMATICALLY LEVEL THE ACFT AT THE SELECTED ALT FL220 WAS SELECTED). THE DEV WAS NOTICED AT APPROX 21500 FT AND WE QUICKLY CLBED BACK TO FL220. DURING THIS SIT WE WERE RUNNING THE PROCS FOR LOSS OF HYD SYS A WHICH ADDED DISTRACTIONS TO THE COCKPIT. THE AUTOPLT HAD REPEATEDLY BEEN WRITTEN UP FOR ITS INABILITY TO MAINTAIN ALT. SUPPLEMENTAL INFO FROM ACN 297874: IN MY BRIEFING I TOLD THE FO TO CONTINUE TO FLY THE ACFT AND I WOULD WORK WITH THE ENGINEER WITH THE CHKLIST. WHEN I LOOKED UP AT THE ALTIMETER WE WERE ALMOST AT 800 FT OVER ASSIGNED ALT. AT THIS POINT I TOOK CTL OF THE ACFT AND HAD THE FO WORK WITH THE FE WITH THE CHKLIST. I ALSO CLBED UP BACK TO OUR ASSIGNED ALT OF 22000 FT. WE LANDED BACK AT LAS WITH HAVING TO CRANK THE GEAR DOWN AND USED THE ALTERNATE MEANS TO GET THE FLAPS DOWN. WE WERE TOWED OFF THE RWY AND TOWED BACK TO THE TERMINAL. THE ACFT WAS A (B727- 200). THE FO WAS NEW WITH THE COMPANY NEW WITH THE ACFT; NEW TO HEAVY JETS; AND HAD UNDER 150 HRS TOTAL IN B727 ACFT.