B727 flight crew has poor reception of VOR on overwater flight between islands. Heading deviation.

Attributes
ACN	339317
Time
Date	199606
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : stt
State Reference	FO
Altitude	msl bound lower : 3000 msl bound upper : 3000
Aircraft 1
Controlling Facilities	tracon : sju
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	339317
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	339316
Events
Anomaly	other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Air Traffic Incident	other
Situations
Navigational Aid	Unspecified

Narrative:

ATC facility þ sju. Location þ sju/113/50. Departed stt on palco 5. Leveled 3000 ft and intercepted 113 degree radial inbound, 293 to sju. We were VOR needle centered. Then needle became erratic, but was equally erratic on both sides from centerline. Was unable to check off with stt tower. He was covering both ground and tower frequencys and was swamped. So 5 mi from stt VOR I went over to sju 128.65. They told us we were 4 mi north of centerline, 1 mi south of stt runway centerline. I think basing a departure on a VOR that's 50 mi away with an aircraft at 3000 ft could be part of this problem. At 3000 ft and 50 mi away it may be causing an erratic signal because we were on the centerline of the radial on the palco 5 according to our navigation information. Supplemental information from acn 339316: the apparent problem with the departure procedure is in using a VOR located 50 mi away on a hilly island for an intercept. I recommend review of the departure to provide a greater margin for the safe separation of aircraft in the departure/arrival corridor.

Original NASA ASRS Text

Title: B727 FLC HAS POOR RECEPTION OF VOR ON OVERWATER FLT BTWN ISLANDS. HDG DEV.

Narrative: ATC FACILITY þ SJU. LOCATION þ SJU/113/50. DEPARTED STT ON PALCO 5. LEVELED 3000 FT AND INTERCEPTED 113 DEG RADIAL INBOUND, 293 TO SJU. WE WERE VOR NEEDLE CTRED. THEN NEEDLE BECAME ERRATIC, BUT WAS EQUALLY ERRATIC ON BOTH SIDES FROM CTRLINE. WAS UNABLE TO CHK OFF WITH STT TWR. HE WAS COVERING BOTH GND AND TWR FREQS AND WAS SWAMPED. SO 5 MI FROM STT VOR I WENT OVER TO SJU 128.65. THEY TOLD US WE WERE 4 MI N OF CTRLINE, 1 MI S OF STT RWY CTRLINE. I THINK BASING A DEP ON A VOR THAT'S 50 MI AWAY WITH AN ACFT AT 3000 FT COULD BE PART OF THIS PROB. AT 3000 FT AND 50 MI AWAY IT MAY BE CAUSING AN ERRATIC SIGNAL BECAUSE WE WERE ON THE CTRLINE OF THE RADIAL ON THE PALCO 5 ACCORDING TO OUR NAV INFO. SUPPLEMENTAL INFO FROM ACN 339316: THE APPARENT PROB WITH THE DEP PROC IS IN USING A VOR LOCATED 50 MI AWAY ON A HILLY ISLAND FOR AN INTERCEPT. I RECOMMEND REVIEW OF THE DEP TO PROVIDE A GREATER MARGIN FOR THE SAFE SEPARATION OF ACFT IN THE DEP/ARR CORRIDOR.

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.