C172 pilot inadvertently changes the transponder code while within the dc ADIZ.

Attributes
ACN	593515
Time
Date	200309
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : fme.airport
State Reference	MD
Altitude	msl single value : 1300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pct.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level descent : intermediate altitude descent : approach
Route In Use	approach : traffic pattern
Flight Plan	VFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time last 90 days : 32 flight time total : 90 flight time type : 90
ASRS Report	593515
Person 2
Affiliation	government : faa
Function	controller : approach
Events
Anomaly	non adherence : published procedure non adherence : far
Independent Detector	aircraft equipment other aircraft equipment : transponder other flight crewa
Resolutory Action	none taken : anomaly accepted
Supplementary
Problem Areas	Flight Crew Human Performance Airspace Structure
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approximately 3 mi west of tipton (rme) inbound for landing, potomac approach informed me that radar service was terminated, to remain on the assigned transponder code, and frequency change approved. I understood his instructions and acknowledged. In my haste to change frequencys, I inadvertently began to redial the transponder code instead of the radio frequency. When I realized the mistake, I could no longer remember my assigned squawk code. I attempted to reset the code to what I remember it was, but am unsure if I dialed it corrected. I attempted to hail potomac again on the same frequency to ask for my assigned code, but was unable to establish 2-WAY communication again. By this time, I was in the pattern for tipton and thus just quickly landed.

Original NASA ASRS Text

Title: C172 PLT INADVERTENTLY CHANGES THE XPONDER CODE WHILE WITHIN THE DC ADIZ.

Narrative: APPROX 3 MI W OF TIPTON (RME) INBOUND FOR LNDG, POTOMAC APCH INFORMED ME THAT RADAR SVC WAS TERMINATED, TO REMAIN ON THE ASSIGNED XPONDER CODE, AND FREQ CHANGE APPROVED. I UNDERSTOOD HIS INSTRUCTIONS AND ACKNOWLEDGED. IN MY HASTE TO CHANGE FREQS, I INADVERTENTLY BEGAN TO REDIAL THE XPONDER CODE INSTEAD OF THE RADIO FREQ. WHEN I REALIZED THE MISTAKE, I COULD NO LONGER REMEMBER MY ASSIGNED SQUAWK CODE. I ATTEMPTED TO RESET THE CODE TO WHAT I REMEMBER IT WAS, BUT AM UNSURE IF I DIALED IT CORRECTED. I ATTEMPTED TO HAIL POTOMAC AGAIN ON THE SAME FREQ TO ASK FOR MY ASSIGNED CODE, BUT WAS UNABLE TO ESTABLISH 2-WAY COM AGAIN. BY THIS TIME, I WAS IN THE PATTERN FOR TIPTON AND THUS JUST QUICKLY LANDED.

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.