Deviation from airway account VOR scalloping.

Attributes
ACN	204616
Time
Date	199203
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : slt
State Reference	PA
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	other vortac
Flight Phase	cruise other
Route In Use	enroute airway : j190
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 90 flight time total : 15000
ASRS Report	204616
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

ZOB 128.57 approximately 100 NM from fix, center asked our heading then gave heading, north correction. Direct slt. CDI was centered. A while later ZOB again asked heading and gave us a south correction. Needles on CDI were being used normally and made corrections to center. I asked if he showed us off course? Controller said first time we were 8 mi south of course then 5.8 mi north. I explained we were navigating using CDI's and both were centered but upon correcting the VOR's showed further corrective needed. Controller finally said that 'they had experienced some scalloping problems with slt VOR and cleared us direct williamsport. Radios worked fine except for slate run. I feel it was the VOR facility in error.

Original NASA ASRS Text

Title: DEV FROM AIRWAY ACCOUNT VOR SCALLOPING.

Narrative: ZOB 128.57 APPROX 100 NM FROM FIX, CTR ASKED OUR HDG THEN GAVE HDG, N CORRECTION. DIRECT SLT. CDI WAS CTRED. A WHILE LATER ZOB AGAIN ASKED HDG AND GAVE US A S CORRECTION. NEEDLES ON CDI WERE BEING USED NORMALLY AND MADE CORRECTIONS TO CTR. I ASKED IF HE SHOWED US OFF COURSE? CTLR SAID FIRST TIME WE WERE 8 MI S OF COURSE THEN 5.8 MI N. I EXPLAINED WE WERE NAVIGATING USING CDI'S AND BOTH WERE CTRED BUT UPON CORRECTING THE VOR'S SHOWED FURTHER CORRECTIVE NEEDED. CTLR FINALLY SAID THAT 'THEY HAD EXPERIENCED SOME SCALLOPING PROBLEMS WITH SLT VOR AND CLRED US DIRECT WILLIAMSPORT. RADIOS WORKED FINE EXCEPT FOR SLATE RUN. I FEEL IT WAS THE VOR FACILITY IN ERROR.

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.