What was found
INSPECTION TYPE: NA ATB-EMERGENCY DECLARED. CREW O2 MASKS USED, NO OTHER EMERGENCY EQUIPMENT USED. A/C WAS TAKEN OUT OF SERVICE. ACRID STRONG SMELL OF BURNING RUBBER RIGHT AFTER TAKEOFF. EMERGENCY AIR RETURN W/CREW ON O2. CFR RESPONDED. DISPATCH NOTIFIED. R & R'D COALSECER (3 EA) C/W CLEAN PACKS/ DUCTS, IAW AMM 21-53-00. NO ODORS NOTED AT THIS TIME. POSSIBLE CONTRIBUTOR TO SMELL MAY BE NOSE L/G UNLOCK ACT LOCKING. R & R NOSE L/G UNLK CYL, IAW AMM 32-35-02 BLK 401. LEAK CHECK GOOD. ESR 32-35-20-01-J.