Narrative:

After departure from washington international airport the original clearance of 'runway heading, radar vectors to J211,' was changed to intercept the 009 degree right off armel VOR, fly north and intercept J211 and fly west on our route to detroit. After intercepting the armel 009 degree right north when the CDI began to move on the intercept for J211. We began an immediate 30 degree bank turn left to intercept J211 wbound. As we had turned through about 40-50 degrees of our turn to intercept J211 the departure controller told us to begin our intercept turn that we had overshot J211 and said he was showing us about 4 mi north of J211. Our CDI's both indicated that we were on course. Then just after departure control's transmission the VOR signal began scalloping left and right. We advised the controller of the scalloping problem and the indication problem between our VOR's and his indications problem between our VOR's and his indications of our position. 2 problems exist here. First, the clearance is a bad one for a jet aircraft, because it involved 2 90 degree intercepts in less than about 20 mi. Also J211 runs right up against the boundary between dulles departure airspace and ZNY airspace. Second the intercept problem is further complicated by the scalloping problem of westminster VOR. This scalloping problem is not uncommon for VOR's out east.

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Original NASA ASRS Text

Title: FLT DEVIATED NORTH OF COURSE DURING COURSE INTERCEPT DUE TO UNRELIABLE (SCALLOPING) VOR COURSE INFORMATION.

Narrative: AFTER DEP FROM WASHINGTON INTL ARPT THE ORIGINAL CLRNC OF 'RWY HDG, RADAR VECTORS TO J211,' WAS CHANGED TO INTERCEPT THE 009 DEG R OFF ARMEL VOR, FLY N AND INTERCEPT J211 AND FLY W ON OUR ROUTE TO DETROIT. AFTER INTERCEPTING THE ARMEL 009 DEG R N WHEN THE CDI BEGAN TO MOVE ON THE INTERCEPT FOR J211. WE BEGAN AN IMMEDIATE 30 DEG BANK TURN LEFT TO INTERCEPT J211 WBOUND. AS WE HAD TURNED THROUGH ABOUT 40-50 DEGS OF OUR TURN TO INTERCEPT J211 THE DEP CTLR TOLD US TO BEGIN OUR INTERCEPT TURN THAT WE HAD OVERSHOT J211 AND SAID HE WAS SHOWING US ABOUT 4 MI N OF J211. OUR CDI'S BOTH INDICATED THAT WE WERE ON COURSE. THEN JUST AFTER DEP CTL'S XMISSION THE VOR SIGNAL BEGAN SCALLOPING LEFT AND RIGHT. WE ADVISED THE CTLR OF THE SCALLOPING PROB AND THE INDICATION PROB BTWN OUR VOR'S AND HIS INDICATIONS PROB BTWN OUR VOR'S AND HIS INDICATIONS OF OUR POS. 2 PROBS EXIST HERE. FIRST, THE CLRNC IS A BAD ONE FOR A JET ACFT, BECAUSE IT INVOLVED 2 90 DEG INTERCEPTS IN LESS THAN ABOUT 20 MI. ALSO J211 RUNS RIGHT UP AGAINST THE BOUNDARY BTWN DULLES DEP AIRSPACE AND ZNY AIRSPACE. SECOND THE INTERCEPT PROB IS FURTHER COMPLICATED BY THE SCALLOPING PROB OF WESTMINSTER VOR. THIS SCALLOPING PROB IS NOT UNCOMMON FOR VOR'S OUT EAST.

Data retrieved from NASA's ASRS site as of August 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.