IAP localizer approach GA-small aircraft started descent outside outer marker.

Attributes
ACN	108077
Time
Date	198904
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : pdk
State Reference	GA
Altitude	msl bound lower : 1700 msl bound upper : 3000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tower : pdk
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 1900 flight time type : 6
ASRS Report	108077
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approach control cleared us for approach to peachtree airport, ILS 20L was in use. Our aircraft did not have an operating glide slope so we were shooting the localizer 20L approach. We were to maintain 3000 until marker and to contact pdk tower at the outer marker. This aircraft's audio panel did not have a mkr bcn audio button so I glanced at the approach plate and dialed in a radial to identify the marker, in case I did not have the mkr bcn on correctly. I mistakingly put in a radial to identify an intersection 4 mi outside of the mkr. When the CDI set on the intersection radial centered, I contacted pdk tower and started my descent. When passing through 1700 MSL, tower called saying that approach's restriction still applied and if I would not adhere to the restriction, I would be proceeding at my own risk. At this point, I was VFR so instead of climbing back to 3000 and IMC condition, I maintained 1700 until field was in sight. Correct identification of the outer marker would have avoided premature descent.

Original NASA ASRS Text

Title: IAP LOC APCH GA-SMA STARTED DESCENT OUTSIDE OUTER MARKER.

Narrative: APCH CTL CLRED US FOR APCH TO PEACHTREE ARPT, ILS 20L WAS IN USE. OUR ACFT DID NOT HAVE AN OPERATING GLIDE SLOPE SO WE WERE SHOOTING THE LOC 20L APCH. WE WERE TO MAINTAIN 3000 UNTIL MARKER AND TO CONTACT PDK TWR AT THE OUTER MARKER. THIS ACFT'S AUDIO PANEL DID NOT HAVE A MKR BCN AUDIO BUTTON SO I GLANCED AT THE APCH PLATE AND DIALED IN A RADIAL TO IDENTIFY THE MARKER, IN CASE I DID NOT HAVE THE MKR BCN ON CORRECTLY. I MISTAKINGLY PUT IN A RADIAL TO IDENTIFY AN INTXN 4 MI OUTSIDE OF THE MKR. WHEN THE CDI SET ON THE INTXN RADIAL CENTERED, I CONTACTED PDK TWR AND STARTED MY DSCNT. WHEN PASSING THROUGH 1700 MSL, TWR CALLED SAYING THAT APCH'S RESTRICTION STILL APPLIED AND IF I WOULD NOT ADHERE TO THE RESTRICTION, I WOULD BE PROCEEDING AT MY OWN RISK. AT THIS POINT, I WAS VFR SO INSTEAD OF CLIMBING BACK TO 3000 AND IMC CONDITION, I MAINTAINED 1700 UNTIL FIELD WAS IN SIGHT. CORRECT IDENTIFICATION OF THE OUTER MARKER WOULD HAVE AVOIDED PREMATURE DSCNT.

Data retrieved from NASA's ASRS site as of August 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.