Electronic interference to onboard navigation instruments.

Attributes
ACN	314810
Time
Date	199508
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : iah
State Reference	TX
Altitude	msl bound lower : 10000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : iah
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 19000 flight time type : 2500
ASRS Report	314810
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 200 flight time total : 19000 flight time type : 400
ASRS Report	314811
Events
Anomaly	other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Tracking inbound on the 234 degree radial of iah VOR, both captain and first officer VOR CDI's were scalloping badly either side of center position. There were numerous thunderstorms in area and we assumed electrical interference. Approach control was so busy, that we could not contact them to advise of the problem. At approximately 30 mi southwest of iah, approach control advised us that he showed us 4 mi north of course and in the same breath gave us another frequency. The next controller on initial contact advised us to turn to a 030 degree heading for radar vectors for an ILS to runway 9 approach. The captain contacted the flight attendant as soon as he could on the interphone and asked her to check for the use of any computer or like equipment by the passenger. Within about 15-30 seconds the course director indicators quit scalloping. The captain checked again with the flight attendant and was advised that a passenger was using a portable computer or some such device. This was after she had made an announcement to turn all such devices off! The passenger stopped using the portable electronic device, the CDI's stopped scalloping!

Original NASA ASRS Text

Title: ELECTRONIC INTERFERENCE TO ONBOARD NAV INSTS.

Narrative: TRACKING INBOUND ON THE 234 DEG RADIAL OF IAH VOR, BOTH CAPT AND FO VOR CDI'S WERE SCALLOPING BADLY EITHER SIDE OF CTR POS. THERE WERE NUMEROUS TSTMS IN AREA AND WE ASSUMED ELECTRICAL INTERFERENCE. APCH CTL WAS SO BUSY, THAT WE COULD NOT CONTACT THEM TO ADVISE OF THE PROB. AT APPROX 30 MI SW OF IAH, APCH CTL ADVISED US THAT HE SHOWED US 4 MI N OF COURSE AND IN THE SAME BREATH GAVE US ANOTHER FREQ. THE NEXT CTLR ON INITIAL CONTACT ADVISED US TO TURN TO A 030 DEG HDG FOR RADAR VECTORS FOR AN ILS TO RWY 9 APCH. THE CAPT CONTACTED THE FLT ATTENDANT AS SOON AS HE COULD ON THE INTERPHONE AND ASKED HER TO CHK FOR THE USE OF ANY COMPUTER OR LIKE EQUIP BY THE PAX. WITHIN ABOUT 15-30 SECONDS THE COURSE DIRECTOR INDICATORS QUIT SCALLOPING. THE CAPT CHKED AGAIN WITH THE FLT ATTENDANT AND WAS ADVISED THAT A PAX WAS USING A PORTABLE COMPUTER OR SOME SUCH DEVICE. THIS WAS AFTER SHE HAD MADE AN ANNOUNCEMENT TO TURN ALL SUCH DEVICES OFF! THE PAX STOPPED USING THE PORTABLE ELECTRONIC DEVICE, THE CDI'S STOPPED SCALLOPING!

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.