ATC radar equipment problem mode C.

Attributes
ACN	236736
Time
Date	199303
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : col
State Reference	NJ
Altitude	msl bound lower : 18000 msl bound upper : 18000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 18500 flight time type : 10000
ASRS Report	236736
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 190 flight time total : 7500 flight time type : 1400
ASRS Report	237187
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

Air carrier X as we were climbing through approximately FL176 (note: the altimeter setting was quite high that day, so the altimeter and altitude alerter were already set to 29.92) to an assigned altitude of FL180, the center queried us as to our altitude. The first officer was flying, so I responded that we were 'about to level at FL180.' the ATC controller then said excitedly that 'I show you at FL185,' and admonished us to 'set your altimeters.' as I previously reported, our altimeter settings were already properly set at 29.92, as we were by then out of FL178 to level at FL180. Needless to say, it is quite disconcerting to have the center put the thought in your head that your pitot static system may be malfunctioning. While the center then said, 'I now show you level FL180,' he didn't offer an explanation as to what really happened on his end. Later that day, I had the appropriate department within my company research the occurrence. They have since informed me that ATC has admitted that for 1 sweep, their scope erroneously indicated FL185 and on the next sweep snapped back to FL178. Also, I have now been informed that their equipment does on occasion make this type of error. As an experienced pilot, I can tell you that when this happens it becomes a matter of safety, since you are very distracted as you try to figure out what's happening.

Original NASA ASRS Text

Title: ATC RADAR EQUIP PROB MODE C.

Narrative: ACR X AS WE WERE CLBING THROUGH APPROX FL176 (NOTE: THE ALTIMETER SETTING WAS QUITE HIGH THAT DAY, SO THE ALTIMETER AND ALT ALERTER WERE ALREADY SET TO 29.92) TO AN ASSIGNED ALT OF FL180, THE CTR QUERIED US AS TO OUR ALT. THE FO WAS FLYING, SO I RESPONDED THAT WE WERE 'ABOUT TO LEVEL AT FL180.' THE ATC CTLR THEN SAID EXCITEDLY THAT 'I SHOW YOU AT FL185,' AND ADMONISHED US TO 'SET YOUR ALTIMETERS.' AS I PREVIOUSLY RPTED, OUR ALTIMETER SETTINGS WERE ALREADY PROPERLY SET AT 29.92, AS WE WERE BY THEN OUT OF FL178 TO LEVEL AT FL180. NEEDLESS TO SAY, IT IS QUITE DISCONCERTING TO HAVE THE CTR PUT THE THOUGHT IN YOUR HEAD THAT YOUR PITOT STATIC SYS MAY BE MALFUNCTIONING. WHILE THE CTR THEN SAID, 'I NOW SHOW YOU LEVEL FL180,' HE DIDN'T OFFER AN EXPLANATION AS TO WHAT REALLY HAPPENED ON HIS END. LATER THAT DAY, I HAD THE APPROPRIATE DEPT WITHIN MY COMPANY RESEARCH THE OCCURRENCE. THEY HAVE SINCE INFORMED ME THAT ATC HAS ADMITTED THAT FOR 1 SWEEP, THEIR SCOPE ERRONEOUSLY INDICATED FL185 AND ON THE NEXT SWEEP SNAPPED BACK TO FL178. ALSO, I HAVE NOW BEEN INFORMED THAT THEIR EQUIP DOES ON OCCASION MAKE THIS TYPE OF ERROR. AS AN EXPERIENCED PLT, I CAN TELL YOU THAT WHEN THIS HAPPENS IT BECOMES A MATTER OF SAFETY, SINCE YOU ARE VERY DISTRACTED AS YOU TRY TO FIGURE OUT WHAT'S HAPPENING.

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.