A single engine pilot was told by the local controller that his transponder's altitude encoder was s...

Attributes
ACN	871006
Time
Date	201001
Local Time Of Day	1201-1800
Place
Locale Reference	LAX.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Small Aircraft Low Wing 1 Eng Retractable Gear
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Direct
Flight Plan	None
Component
Aircraft Component	Transponder
Person 1
Function	Single Pilot
Qualification	Flight Crew Instrument Flight Crew Private
Experience	Flight Crew Last 90 Days 23.7 Flight Crew Total 3587 Flight Crew Type 3587
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

After flying 2 hours at 9500 ft; a descent was made to 3500 ft to cross lax within the 'special flight rules area (sfar)'. The class B 'veil' requires an operating transponder with mode C reporting proper altitude. After departing the sfar and contacting my destination's tower for landing clearance; the tower advised that my transponder mode C was reporting over 10;000 ft when I was descending from 2000 ft to less than 100 ft at the surface. It appears that the blind encoder had stuck at the highest altitude of the flight. The blind encoder is being replaced and the altimeter/encoder/transponder/static system will be re-certified.

Original NASA ASRS Text

Title: A single engine pilot was told by the Local Controller that his transponder's altitude encoder was stuck at 10;000' after he had already passed through the LAX Special Flight Rules Area at 3;500'.

Narrative: After flying 2 hours at 9500 ft; a descent was made to 3500 ft to cross LAX within the 'special flight rules area (SFAR)'. The Class B 'veil' requires an operating transponder with Mode C reporting proper altitude. After departing the SFAR and contacting my destination's Tower for landing clearance; the Tower advised that my transponder Mode C was reporting over 10;000 ft when I was descending from 2000 ft to less than 100 ft at the surface. It appears that the blind encoder had stuck at the highest altitude of the flight. The blind encoder is being replaced and the altimeter/encoder/transponder/static system will be re-certified.

Data retrieved from NASA's ASRS site as of April 2012 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.

A single engine pilot was told by the local controller that his transponder's altitude encoder was stuck at 10;000' after he had already passed through the lax special flight rules area at 3;500'.