Small aircraft circling to locate a private strip has near midair collision with twin.

Attributes
ACN	219055
Time
Date	199208
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : den
State Reference	CO
Altitude	msl bound lower : 7500 msl bound upper : 7500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : acy
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other other
Flight Plan	None
Aircraft 2
Make Model Name	Small Transport
Flight Phase	cruise other
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 40 flight time total : 450 flight time type : 40
ASRS Report	219055
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Miss Distance	horizontal : 0 vertical : 75
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Trying to locate a small private strip north of denver (parkland), I was circling to compare my map with reference points on the ground when a medium twin passed close beneath me. I checked the transponder and verified the reply, light was blinking normally. I assumed the other aircraft was also flying VFR. Since then I have considered the possibility that my transponder was not squawking altitude. The manufacturer, model, is controled by a 3 position toggle switch (off, on, altitude) which moves vertically through a small angle. The visual indication is very similar in the on and altitude position. Now I verify the altitude position by feeling for 2 distinct clicks when turning the transponder on. Callback conversation with reporter revealed the following: reporter states he thought by squawking 1200 controller would get a conflict alert if 2 aircraft in close proximity. Thought transponder was the magic box that would take care of him, especially within the 30 mi veil. Counseled that see and avoid is his only protection.

Original NASA ASRS Text

Title: SMA CIRCLING TO LOCATE A PRIVATE STRIP HAS NMAC WITH TWIN.

Narrative: TRYING TO LOCATE A SMALL PRIVATE STRIP N OF DENVER (PARKLAND), I WAS CIRCLING TO COMPARE MY MAP WITH REF POINTS ON THE GND WHEN A MEDIUM TWIN PASSED CLOSE BENEATH ME. I CHKED THE TRANSPONDER AND VERIFIED THE REPLY, LIGHT WAS BLINKING NORMALLY. I ASSUMED THE OTHER ACFT WAS ALSO FLYING VFR. SINCE THEN I HAVE CONSIDERED THE POSSIBILITY THAT MY TRANSPONDER WAS NOT SQUAWKING ALT. THE MANUFACTURER, MODEL, IS CTLED BY A 3 POS TOGGLE SWITCH (OFF, ON, ALT) WHICH MOVES VERTICALLY THROUGH A SMALL ANGLE. THE VISUAL INDICATION IS VERY SIMILAR IN THE ON AND ALT POS. NOW I VERIFY THE ALT POS BY FEELING FOR 2 DISTINCT CLICKS WHEN TURNING THE TRANSPONDER ON. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR STATES HE THOUGHT BY SQUAWKING 1200 CTLR WOULD GET A CONFLICT ALERT IF 2 ACFT IN CLOSE PROX. THOUGHT TRANSPONDER WAS THE MAGIC BOX THAT WOULD TAKE CARE OF HIM, ESPECIALLY WITHIN THE 30 MI VEIL. COUNSELED THAT SEE AND AVOID IS HIS ONLY PROTECTION.

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.