Beechjet 400
Air Traffic Control Fully Certified
Workload; Human-Machine Interface; Confusion
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Human Factors; Procedure
I was training on Low RADAR. Our primary RADAR was out of service. We were using CENRAP. CENRAP requires enroute separation; more coordination between Tower and RADAR and training was in progress (both in our Tower and us on low RADAR). The trainee hadn't trained practice approaches with CENRAP before; so this was new territory for him. We didn't have staffing to give us an associate. With all the requirements to separate aircraft by 5 miles and 4 aircraft doing practice approaches at 2 different airports; the trainee got behind. I took over several times to catch him up. In the course of things; a BE40 didn't get a change of frequency to Tower. They had traffic in their pattern. Then when the BE40 was inside the final approach fix he took a turn for another aircraft. This put him in conflict with 2 different aircraft in the airport's pattern. He had his TCAS on and was able to get out of the situation. We brought him back around for another ILS approach. Recommendation: First of all; they took our RADAR out of service the day before during our busiest hours. While working on the RADAR; something broke and they weren't able to restore our RADAR causing us to be on CENRAP 2 days in a row. The fact that we were without normal RADAR services increased our workload with all the aircraft wanting practice approaches both days. Both days we were short staffed due to sickness; jury duty and lack of personnel. RADAR should be worked on during off-peak hours (evenings or weekends) or when we're closed from midnight to 6am. The trainee wouldn't have fallen behind as badly if we'd had an associate to take the calls for release from local; call the inbounds to the airport; issue flight plans to the airport and answer any other calls. He would have been on frequency and not missed some of the details. He wouldn't have fallen behind and had so many problems if we were using approach separation procedures (course divergence; 3 miles; etc).
TRACON Controller described an unsafe condition when forced to use CENRAP during training; noting maintenance practices regarding the use of CENRAP should be better planned.