Altitude readout on radar scope jumping from one altitude to another.

Attributes
ACN	230096
Time
Date	199301
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : srq
State Reference	FL
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : tpa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : initial
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller military : 4 controller radar : 8
ASRS Report	230096
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

Air carrier X, an medium large transport, departed srq climbing to 10000 MSL. I observed the mode C of this aircraft go from 3000 to 6200 for a period of 2 sweeps of my radar and then return to 3200 and resumed normal readout. This is a serious safety problem that tpa approach has been experiencing for far too long. It must be corrected before something bad happens.

Original NASA ASRS Text

Title: ALT READOUT ON RADAR SCOPE JUMPING FROM ONE ALT TO ANOTHER.

Narrative: ACR X, AN MLG, DEPARTED SRQ CLBING TO 10000 MSL. I OBSERVED THE MODE C OF THIS ACFT GO FROM 3000 TO 6200 FOR A PERIOD OF 2 SWEEPS OF MY RADAR AND THEN RETURN TO 3200 AND RESUMED NORMAL READOUT. THIS IS A SERIOUS SAFETY PROB THAT TPA APCH HAS BEEN EXPERIENCING FOR FAR TOO LONG. IT MUST BE CORRECTED BEFORE SOMETHING BAD HAPPENS.

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.