Mission essential – Zac Krotzer, airfield systems technician Published Feb. 27, 2013 VANCE AIR FORCE BASE, Okla. -- Senior Airman Zac Krotzer is an airfield systems technician with the 71st Communications Squadron at Vance Air Force Base. Airfield technicians like Krotzer are essential to the mission at Vance. Their expertise keeps the air-to-ground communication systems and navigational equipment supporting the world-class pilots trained at Vance.