Air carrier medium large transport altitude deviation in response to TCASII RA.

Attributes
ACN	199631
Time
Date	199201
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ott
State Reference	MD
Altitude	msl bound lower : 28000 msl bound upper : 29000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 17000
ASRS Report	199631
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude altitude deviation : overshoot conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise dca center advised us of converging traffic at 9 O'clock climbing to FL280. According to our TCASII the traffic continued to climb through 280 to 288. Our TCASII gave us a RA to descend. We initiated a right turn and descent. During this time ATC questioned the aircraft about it's altitude. ATC radar showed his altitude at 286. Next TCASII showed us clear of the traffic and the acfts altitude descending back to FL280. We turned back on course and questioned ATC. Their reply was 'we believe it was an erroneous mode C.'

Original NASA ASRS Text

Title: ACR MLG ALTDEV IN RESPONSE TO TCASII RA.

Narrative: DURING CRUISE DCA CENTER ADVISED US OF CONVERGING TFC AT 9 O'CLOCK CLBING TO FL280. ACCORDING TO OUR TCASII THE TFC CONTINUED TO CLB THROUGH 280 TO 288. OUR TCASII GAVE US A RA TO DSND. WE INITIATED A R TURN AND DSCNT. DURING THIS TIME ATC QUESTIONED THE ACFT ABOUT IT'S ALT. ATC RADAR SHOWED HIS ALT AT 286. NEXT TCASII SHOWED US CLR OF THE TFC AND THE ACFTS ALT DSNDING BACK TO FL280. WE TURNED BACK ON COURSE AND QUESTIONED ATC. THEIR REPLY WAS 'WE BELIEVE IT WAS AN ERRONEOUS MODE C.'

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.