GA7 pilot reports a near midair collision at L18 during a practice GPS approach to runway 18. A C172...

Attributes
ACN	1034886
Time
Date	201209
Local Time Of Day	0601-1200
Place
Locale Reference	L18.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Grumman American Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	None
Aircraft 2
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Component
Aircraft Component	VHF
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 160 Flight Crew Total 12000 Flight Crew Type 500
Events
Anomaly	Aircraft Equipment Problem Less Severe Conflict NMAC
Miss Distance	Horizontal 200 Vertical 0

Narrative:

[I was] flying a practice GPS approach to runway 18 at L18. [I] heard a cessna 172 aircraft in pattern. Pilot was announcing position on CTAF; but not every leg of the pattern. I was proceeding straight in and announced my position at 10; 5; 3; and 1 miles relative to a straight in final. Was looking for the C172 but did not have them visually. I picked up relative movement in my peripheral vision and saw the C172 in the turn from left base to final at my altitude. They were about 200 ft in front of me but my speed was 90 KTS; much faster than their speed. As we were both descending I made a hard right climbing turn to avoid contact. As I climbed out I called to ask if they had in fact been broadcasting their position the whole time while in the pattern. No response. Upon further investigation it appears that my #1 comm radio; which was in use at the time; is cutting out after I transmit. It returns to normal after several seconds. This transmit problem seems to be happening intermittently therefore make it difficult to diagnose. I have service scheduled for this unit.

Original NASA ASRS Text

Title: GA7 pilot reports a NMAC at L18 during a practice GPS approach to Runway 18. A C172 was heard in the pattern on CTAF but was apparently not announcing each leg so the reporter was not aware of his position until coming into very close proximity. It turns out the reporter's radio was malfunctioning.

Narrative: [I was] flying a practice GPS approach to Runway 18 at L18. [I] heard a Cessna 172 aircraft in pattern. Pilot was announcing position on CTAF; but not every leg of the pattern. I was proceeding straight in and announced my position at 10; 5; 3; and 1 miles relative to a straight in final. Was looking for the C172 but did not have them visually. I picked up relative movement in my peripheral vision and saw the C172 in the turn from left base to final at my altitude. They were about 200 FT in front of me but my speed was 90 KTS; much faster than their speed. As we were both descending I made a hard right climbing turn to avoid contact. As I climbed out I called to ask if they had in fact been broadcasting their position the whole time while in the pattern. No response. Upon further investigation it appears that my #1 comm radio; which was in use at the time; is cutting out after I transmit. It returns to normal after several seconds. This transmit problem seems to be happening intermittently therefore make it difficult to diagnose. I have service scheduled for this unit.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.