The las airspace has an arrival fix named trrop on the grnpa arrival and another fix named tropp in ...

Narrative:

About 10 miles north of prino on the tyssn arrival; las ATC asked us to turn northwest. Then; they asked us to go to what sounded like 'tropp'; and 'resume the 'grnpa arrival'. When we were issued this clearance; I told ATC that we weren't on that arrival. He spelled out the fix to fly to. I entered 'tropp' into the FMS; instead of 'trrop'. After ATC saw us flying toward that fix (which was northwest of the airport about 20-30 miles); we were instructed to turn left to 240 heading to intercept 'trrop and the remainder of the arrival. We proceeded to trrop; the remainder of the arrival and landed uneventfully on 19L in las. We were in a high workload environment and were issued a clearance on a arrival that we weren't even on. We should have asked for an initial vector first. As you can see; the naming conventions for the fix were very similar and the fixes were within 30 miles of each other.

Original NASA ASRS Text

Title: The LAS airspace has an arrival fix named TRROP on the GRNPA Arrival and another fix named TROPP in the area. The two fixes were transposed by a flight crew causing a track deviation detected by ATC.

Narrative: About 10 miles north of PRINO on the TYSSN arrival; LAS ATC asked us to turn NW. Then; they asked us to go to what sounded like 'TROPP'; and 'resume the 'GRNPA Arrival'. When we were issued this clearance; I told ATC that we weren't on that arrival. He spelled out the fix to fly to. I entered 'TROPP' into the FMS; instead of 'TRROP'. After ATC saw us flying toward that fix (which was northwest of the airport about 20-30 miles); we were instructed to turn left to 240 heading to intercept 'TRROP and the remainder of the arrival. We proceeded to TRROP; the remainder of the arrival and landed uneventfully on 19L in LAS. We were in a high workload environment and were issued a clearance on a arrival that we weren't even on. We should have asked for an initial vector first. As you can see; the naming conventions for the fix were very similar and the fixes were within 30 miles of each other.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	904406
Time
Date	201008
Local Time Of Day	1201-1800
Place
Locale Reference	LAS.Airport
State Reference	NV
Component
Aircraft Component	FMS/FMC
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying Captain
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Deviation - Track / Heading All Types

The las airspace has an arrival fix named trrop on the grnpa arrival and another fix named tropp in the area. The two fixes were transposed by a flight crew causing a track deviation detected by ATC.