Cpl. Elijah Schellhardt, a Marine Corps Tactical Systems Support Activity Common Aviation Command Control System (CAC2S) support team member, and native of Frederick, Md., shows visiting VIPs the shellback Humvee used to house the CAC2S Phase II servers at the Stoval Auxiliary Airfield, on Marine Corps Air Station Yuma, Ariz., Oct. 8. The shellback Humvee concept provides superior system mobility over the traditional use of large trucks for transport of the aging Marine Air Command and Control System CAC2S is slated to replace. - Cpl. Elijah Schellhardt, a Marine Corps Tactical Systems Support Activity Common Aviation Command Control System (CAC2S) support team member, and native of Frederick, Md., shows visiting VIPs the shellback Humvee used to house the CAC2S Phase II servers at the Stoval Auxiliary Airfield, on Marine Corps Air Station Yuma, Ariz., Oct. 8. The shellback Humvee concept provides superior system mobility over the traditional use of large trucks for transport of the aging Marine Air Command and Control System CAC2S is slated to replace.