Small transport did not fly the route given in their clearance.

Attributes
ACN	98574
Time
Date	198811
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : prb
State Reference	CA
Altitude	msl bound lower : 22000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : atp pilot : cfi pilot : commercial
Experience	flight time last 90 days : 90 flight time total : 8000 flight time type : 500
ASRS Report	98574
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	other spatial deviation
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were given a clearance which we understood as our previously assigned route (prb--rom--gilro--sjc). Apparently the controller meant direct to gilro (we were south of prb at the time). The basis of the controller's clearance was the fact that we could go direct to an intersection through the use of a mapping mode on our center screen. Although the capability exists, course guidance is a bit problematic in that there is really no way that one can tell if one is straying from course, thus navigating direct is not approved. The controller thought that we could do it legally. This is a result of some pilots out there not knowing the legal limitations and passing that kind of bum information around.

Original NASA ASRS Text

Title: SMT DID NOT FLY THE ROUTE GIVEN IN THEIR CLRNC.

Narrative: WE WERE GIVEN A CLRNC WHICH WE UNDERSTOOD AS OUR PREVIOUSLY ASSIGNED ROUTE (PRB--ROM--GILRO--SJC). APPARENTLY THE CTLR MEANT DIRECT TO GILRO (WE WERE SOUTH OF PRB AT THE TIME). THE BASIS OF THE CTLR'S CLRNC WAS THE FACT THAT WE COULD GO DIRECT TO AN INTERSECTION THROUGH THE USE OF A MAPPING MODE ON OUR CENTER SCREEN. ALTHOUGH THE CAPABILITY EXISTS, COURSE GUIDANCE IS A BIT PROBLEMATIC IN THAT THERE IS REALLY NO WAY THAT ONE CAN TELL IF ONE IS STRAYING FROM COURSE, THUS NAVIGATING DIRECT IS NOT APPROVED. THE CTLR THOUGHT THAT WE COULD DO IT LEGALLY. THIS IS A RESULT OF SOME PLTS OUT THERE NOT KNOWING THE LEGAL LIMITATIONS AND PASSING THAT KIND OF BUM INFORMATION AROUND.

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.