PA-25 Pawnee
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 25; Flight Crew Total 14000; Flight Crew Type 500
Communication Breakdown
Conflict NMAC
Flight Crew Took Evasive Action
Airport; Human Factors
After releasing a glider at 3;000 AGL and descending to traffic pattern altitude (1;000 AGL) rolled out to enter a right base leg for Runway 18 at ZPH. A Grumman AA5 was coming at me slightly to the left of my nose in level flight at about 1;000 FT AGL. I pulled up and missed the aircraft by an estimated 50-100 FT. The AA5 took no evasive action and did not respond to a radio call. The AA5 continued on a long; wide downwind for left traffic on Runway 22. The AA5 finally made a radio call turning base. No response about the near miss.ZPH is a very busy airport; with sky diving and glider operations on weekends. Per agreement with the airport; skydiving and glider operations are conducted on Runway 18/36; with normal operations on Runway 4/22; wind permitting. All traffic is to the west of the airport; right hand pattern for 18 and 22; left hand pattern for 36 and 04.The glider and skydiving operations report downwind and/or base prior to entry and base to final. These operations have worked will for many years; when everybody monitors the CTAF frequency. It appears that the AA5 did not make a pattern entry call or was on the wrong frequency. The AA5 is a regular user of ZPH and may be based there.
PA25 pilot experiences a NMAC in the traffic pattern for Runway 18 at ZPH with an AA5 entering for left traffic for Runway 22. The AA5 pilot is not on the CTAF and takes no evasive action.