Flight crew experienced problems with their long range navigational equipment resulting in becoming ...

Attributes
ACN	324670
Time
Date	199512
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : kbv
State Reference	FO
Altitude	msl bound lower : 41000 msl bound upper : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : txkf
Operator	common carrier : air taxi
Make Model Name	Learjet 35
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Route In Use	enroute : atlantic enroute : other oceanic enroute airway : a300
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 140 flight time total : 3300
ASRS Report	324670
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : became reoriented other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

The flight was in a learjet model 35A from pne to tncm. The flight plans were done by universal and we departed using GPS and 2 VLF omegas for navigation to tncm. While in cruise, the GPS was displaying erroneous information and we turned to our 2 VLF omegas for navigation. While proceeding sbound, we tuned in bermuda VOR to double-check our position. We noticed our bearing and DME to bermuda did not agree with our 2 VLF omegas. It was at this time when we realized our VLF omegas were inaccurate! Mins later, commercial radio asked us to switch over to bermuda approach. Bermuda approach asked us our position. We read our latitude and longitudes from our VLF omegas and bermuda confirmed that our findings were correct, the VLF omegas were inaccurate. Bermuda was aware of our navigation equipment malfunction and twice they gave us our latitude and longitudes so we can reprogram our VLF omegas. Once our VLF omega matched bermuda's position on us, we were given a new routing to st maarten and we continued without further complications. Bermuda approach informed us that this error caused us to be approximately 90 mi east of course! No evasive action was required during this occurrence. Contributing factors were erroneous GPS and VLF omegas. (We were not aware of VLF omega error.) I do not know why we received such errors in our system as they have worked well in the past. My suggestion to prevent such an occurrence would be to have system status and accuracy checks prior to any overwater flts where navigational facilities are sparse.

Original NASA ASRS Text

Title: FLC EXPERIENCED PROBS WITH THEIR LONG RANGE NAVIGATIONAL EQUIP RESULTING IN BECOMING OFF COURSE APPROX 90 MI OVER AN OCEANIC RTE.

Narrative: THE FLT WAS IN A LEARJET MODEL 35A FROM PNE TO TNCM. THE FLT PLANS WERE DONE BY UNIVERSAL AND WE DEPARTED USING GPS AND 2 VLF OMEGAS FOR NAV TO TNCM. WHILE IN CRUISE, THE GPS WAS DISPLAYING ERRONEOUS INFO AND WE TURNED TO OUR 2 VLF OMEGAS FOR NAV. WHILE PROCEEDING SBOUND, WE TUNED IN BERMUDA VOR TO DOUBLE-CHK OUR POS. WE NOTICED OUR BEARING AND DME TO BERMUDA DID NOT AGREE WITH OUR 2 VLF OMEGAS. IT WAS AT THIS TIME WHEN WE REALIZED OUR VLF OMEGAS WERE INACCURATE! MINS LATER, COMMERCIAL RADIO ASKED US TO SWITCH OVER TO BERMUDA APCH. BERMUDA APCH ASKED US OUR POS. WE READ OUR LATITUDE AND LONGITUDES FROM OUR VLF OMEGAS AND BERMUDA CONFIRMED THAT OUR FINDINGS WERE CORRECT, THE VLF OMEGAS WERE INACCURATE. BERMUDA WAS AWARE OF OUR NAV EQUIP MALFUNCTION AND TWICE THEY GAVE US OUR LATITUDE AND LONGITUDES SO WE CAN REPROGRAM OUR VLF OMEGAS. ONCE OUR VLF OMEGA MATCHED BERMUDA'S POS ON US, WE WERE GIVEN A NEW ROUTING TO ST MAARTEN AND WE CONTINUED WITHOUT FURTHER COMPLICATIONS. BERMUDA APCH INFORMED US THAT THIS ERROR CAUSED US TO BE APPROX 90 MI E OF COURSE! NO EVASIVE ACTION WAS REQUIRED DURING THIS OCCURRENCE. CONTRIBUTING FACTORS WERE ERRONEOUS GPS AND VLF OMEGAS. (WE WERE NOT AWARE OF VLF OMEGA ERROR.) I DO NOT KNOW WHY WE RECEIVED SUCH ERRORS IN OUR SYS AS THEY HAVE WORKED WELL IN THE PAST. MY SUGGESTION TO PREVENT SUCH AN OCCURRENCE WOULD BE TO HAVE SYS STATUS AND ACCURACY CHKS PRIOR TO ANY OVERWATER FLTS WHERE NAVIGATIONAL FACILITIES ARE SPARSE.

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.

Flight crew experienced problems with their long range navigational equipment resulting in becoming off course approximately 90 mi over an oceanic route.