Grumman AA5 has near midair collision with small twin while entering traffic pattern at pdk.

Attributes
ACN	795198
Time
Date	200807
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pdk.airport
State Reference	GA
Altitude	msl single value : 3700
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	tower : pdk.tower
Operator	general aviation : personal
Make Model Name	Cheetah Tiger Traveler
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	None
Aircraft 2
Controlling Facilities	tower : pdk.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private pilot : commercial pilot : instrument
Experience	flight time last 90 days : 70 flight time total : 770 flight time type : 600
ASRS Report	795198
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Miss Distance	horizontal : 100 vertical : 50
Supplementary
Problem Areas	Airspace Structure Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

I had contacted pdk tower 9 NM (065 degree radial) from the field for a full stop landing in VFR conditions. I was told to report 4 NM out and to identify (1200). At 6.4 NM (by later checking my GPS) I visually saw a twin engine climbing at my 2 O'clock position. If I had continued on my present course (which I was beginning a gradual descent at this point) I am certain that we were on a direct course to the same point in the sky. I immediately took evasive action and turned into a right steep bank dive with the hope that he would visualize me and pass overhead; which he did. He continued without any apparent change in direction to fly overtop and slightly ahead of my position. I realize he had the right of way and that the tower controller had not mentioned that he had me radar contact but I decided to report it to him anyway. I believe it was a baron that passed by and when I reported it to the tower the controller said that the 'baron was at 3700 ft;' while I was at 3100 ft. I told him that 'I dropped pretty fast' to which he acknowledged. I do not know who was talking to the baron at the time and I do not believe that anyone is at fault. It makes me realize that ads-B or some similar traffic awareness system may soon become a necessity in as busy an airspace as this.

Original NASA ASRS Text

Title: GRUMMAN AA5 HAS NMAC WITH SMALL TWIN WHILE ENTERING TRAFFIC PATTERN AT PDK.

Narrative: I HAD CONTACTED PDK TWR 9 NM (065 DEG RADIAL) FROM THE FIELD FOR A FULL STOP LNDG IN VFR CONDITIONS. I WAS TOLD TO RPT 4 NM OUT AND TO IDENT (1200). AT 6.4 NM (BY LATER CHKING MY GPS) I VISUALLY SAW A TWIN ENG CLBING AT MY 2 O'CLOCK POS. IF I HAD CONTINUED ON MY PRESENT COURSE (WHICH I WAS BEGINNING A GRADUAL DSCNT AT THIS POINT) I AM CERTAIN THAT WE WERE ON A DIRECT COURSE TO THE SAME POINT IN THE SKY. I IMMEDIATELY TOOK EVASIVE ACTION AND TURNED INTO A R STEEP BANK DIVE WITH THE HOPE THAT HE WOULD VISUALIZE ME AND PASS OVERHEAD; WHICH HE DID. HE CONTINUED WITHOUT ANY APPARENT CHANGE IN DIRECTION TO FLY OVERTOP AND SLIGHTLY AHEAD OF MY POS. I REALIZE HE HAD THE RIGHT OF WAY AND THAT THE TWR CTLR HAD NOT MENTIONED THAT HE HAD ME RADAR CONTACT BUT I DECIDED TO RPT IT TO HIM ANYWAY. I BELIEVE IT WAS A BARON THAT PASSED BY AND WHEN I RPTED IT TO THE TWR THE CTLR SAID THAT THE 'BARON WAS AT 3700 FT;' WHILE I WAS AT 3100 FT. I TOLD HIM THAT 'I DROPPED PRETTY FAST' TO WHICH HE ACKNOWLEDGED. I DO NOT KNOW WHO WAS TALKING TO THE BARON AT THE TIME AND I DO NOT BELIEVE THAT ANYONE IS AT FAULT. IT MAKES ME REALIZE THAT ADS-B OR SOME SIMILAR TFC AWARENESS SYS MAY SOON BECOME A NECESSITY IN AS BUSY AN AIRSPACE AS THIS.

Data retrieved from NASA's ASRS site as of May 2009 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.