<< >> NASA ASRS Report 429295, February 1999

Atx PA31, while descending through clouds on the oak ILS runway 27R approach, initiated an evasive maneuver due to C172 crossing beneath and clear of clouds. Approach had issued a TA on the unknown aircraft.

Attributes
ACN	429295
Time
Date	199902
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : oak.airport
State Reference	CA
Altitude	msl bound lower : 3700 msl bound upper : 4000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air taxi
Make Model Name	PA-31 Navajo Chieftan/Mojave/Navajo T1020
Operating Under FAR Part	Part 135
Navigation In Use	ils localizer & glide slope : 27r
Flight Phase	descent : approach descent : vacating altitude
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : o90.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : multi engine pilot : cfi pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 2700 flight time type : 600
ASRS Report	429295
Person 2
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	conflict : nmac inflight encounter : weather other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued alert flight crew : took evasive action
Miss Distance	vertical : 450
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

While on the oak ILS runway 27R approach, at approximately 23 DME from oak, I was told I had traffic at 1 O'clock moving to 12 O'clock. I was in and out of the clouds, but I was able to make contact briefly with the other aircraft which appeared to be a C172. When I made contact with the aircraft, I was level at 4000 ft MSL then cleared to maintain 3500 ft MSL until established on the oak ILS. I briefly re-entered the clouds in my descent to 3500 ft MSL and was free of the clouds at 3700 ft MSL at 20 DME when the C172 passed under my aircraft at what appeared to be 450 ft. I momentarily leveled off until the C172 passed, then I continued on the approach uneventfully and landed at oak airport.

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Original NASA ASRS Text

Title: ATX PA31, WHILE DSNDING THROUGH CLOUDS ON THE OAK ILS RWY 27R APCH, INITIATED AN EVASIVE MANEUVER DUE TO C172 XING BENEATH AND CLR OF CLOUDS. APCH HAD ISSUED A TA ON THE UNKNOWN ACFT.

Narrative: WHILE ON THE OAK ILS RWY 27R APCH, AT APPROX 23 DME FROM OAK, I WAS TOLD I HAD TFC AT 1 O'CLOCK MOVING TO 12 O'CLOCK. I WAS IN AND OUT OF THE CLOUDS, BUT I WAS ABLE TO MAKE CONTACT BRIEFLY WITH THE OTHER ACFT WHICH APPEARED TO BE A C172. WHEN I MADE CONTACT WITH THE ACFT, I WAS LEVEL AT 4000 FT MSL THEN CLRED TO MAINTAIN 3500 FT MSL UNTIL ESTABLISHED ON THE OAK ILS. I BRIEFLY RE-ENTERED THE CLOUDS IN MY DSCNT TO 3500 FT MSL AND WAS FREE OF THE CLOUDS AT 3700 FT MSL AT 20 DME WHEN THE C172 PASSED UNDER MY ACFT AT WHAT APPEARED TO BE 450 FT. I MOMENTARILY LEVELED OFF UNTIL THE C172 PASSED, THEN I CONTINUED ON THE APCH UNEVENTFULLY AND LANDED AT OAK ARPT.

Data retrieved from NASA's ASRS site as of July 2007 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.