An MD80 crew, while cruising at FL280, experienced an unexplained aircraft roll to the left.

Attributes
ACN	532705
Time
Date	200112
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : pxr.vortac
State Reference	AZ
Altitude	msl single value : 28000
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zab.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	532705
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Airspace Structure Navigational Facility FAA ATC Human Performance
Primary Problem	FAA

Narrative:

After 2 hours on the same heading, direct tnp, the aircraft suddenly began to roll to the left. We stopped it, then the alert came up on the GPS screen. ZAB told us the military was jamming GPS frequencys, though the NOTAM had only been issued 20 mins prior. No conflict with other aircraft, no real problem for us but it seems like somebody in the system should have warned us. ZAB said some other aircraft had similar problems.

Original NASA ASRS Text

Title: AN MD80 CREW, WHILE CRUISING AT FL280, EXPERIENCED AN UNEXPLAINED ACFT ROLL TO THE L.

Narrative: AFTER 2 HRS ON THE SAME HEADING, DIRECT TNP, THE ACFT SUDDENLY BEGAN TO ROLL TO THE L. WE STOPPED IT, THEN THE ALERT CAME UP ON THE GPS SCREEN. ZAB TOLD US THE MIL WAS JAMMING GPS FREQS, THOUGH THE NOTAM HAD ONLY BEEN ISSUED 20 MINS PRIOR. NO CONFLICT WITH OTHER ACFT, NO REAL PROB FOR US BUT IT SEEMS LIKE SOMEBODY IN THE SYS SHOULD HAVE WARNED US. ZAB SAID SOME OTHER ACFT HAD SIMILAR PROBS.

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.