An MD80 crew allowed the autoplt to begin the turn early, on the arc approach to runway 17 at mtj.

Attributes
ACN	537812
Time
Date	200202
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mtj.airport
State Reference	CO
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	artcc : zdv.artcc tower : mdw.tower
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 17 other vortac
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	observation : company check pilot oversight : pic
Qualification	pilot : atp
ASRS Report	537812
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer instruction : trainee observation : company check pilot
Qualification	pilot : atp
Events
Anomaly	non adherence : published procedure non adherence : far non adherence : company policies other anomaly other other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to intended or assigned course none taken : detected after the fact
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

S80 false localizer capture. I was qualifying check airman into mtj and we decided to do the arc to ILS runway 17 off of pagre intersection for training even though it was VFR. We were on the arc using the GPS to navigation. The ILS frequency and course were in the left side and I was on the VOR frequency to xchk the arc. The DFGS was in side one. About 1/2 way around the arc, my partner armed the localizer. Shortly after that we got localizer capture and the aircraft turned outbound even though we were nowhere close to the inbound course. We caught it after about 5-10 degrees of heading change and corrected back to course using heading select. We reintercepted the arc and then the localizer and the approach was uneventful after that. The concern that I have is that the aircraft turned toward terrain that is over 1000 ft higher about 10 mi away. If this happens in the WX and the recognition of it is slow, you could have a serious problem since the terrain rises rapidly. This is especially true if you don't have a navigation display to enhance your situational awareness. Another concern is that if the navigation mode is used to correct back to course you have to switch to navigation to do so and then back to radial to intercept the localizer. This is time consuming, plus, how do you intercept a course to an arc? There are approachs in mexico that also use air carrier's to get aligned with final so this could be a problem there also. What is particularly onerous about mtj though is that there is no radar on the approach so you are really on your own. Hopefully in mex someone would notify you. There is no information in the operating manual about when to arm the localizer. The S80 is probably designed to properly intercept the localizer when it is on an intercept course. We both flew the F100 and both remember there is no problem arming the localizer when using the navigation mode. However, it appears that the S80 is not. If this is the case, I think that a message should be added to all S80 flight plans so that crews are made aware of the problem. All the approachs that I can think of that use an arc are in mountainous terrain and a mistake could be disastrous.

Original NASA ASRS Text

Title: AN MD80 CREW ALLOWED THE AUTOPLT TO BEGIN THE TURN EARLY, ON THE ARC APCH TO RWY 17 AT MTJ.

Narrative: S80 FALSE LOC CAPTURE. I WAS QUALIFYING CHK AIRMAN INTO MTJ AND WE DECIDED TO DO THE ARC TO ILS RWY 17 OFF OF PAGRE INTXN FOR TRAINING EVEN THOUGH IT WAS VFR. WE WERE ON THE ARC USING THE GPS TO NAV. THE ILS FREQ AND COURSE WERE IN THE L SIDE AND I WAS ON THE VOR FREQ TO XCHK THE ARC. THE DFGS WAS IN SIDE ONE. ABOUT 1/2 WAY AROUND THE ARC, MY PARTNER ARMED THE LOC. SHORTLY AFTER THAT WE GOT LOC CAPTURE AND THE ACFT TURNED OUTBOUND EVEN THOUGH WE WERE NOWHERE CLOSE TO THE INBOUND COURSE. WE CAUGHT IT AFTER ABOUT 5-10 DEGS OF HDG CHANGE AND CORRECTED BACK TO COURSE USING HDG SELECT. WE REINTERCEPTED THE ARC AND THEN THE LOC AND THE APCH WAS UNEVENTFUL AFTER THAT. THE CONCERN THAT I HAVE IS THAT THE ACFT TURNED TOWARD TERRAIN THAT IS OVER 1000 FT HIGHER ABOUT 10 MI AWAY. IF THIS HAPPENS IN THE WX AND THE RECOGNITION OF IT IS SLOW, YOU COULD HAVE A SERIOUS PROB SINCE THE TERRAIN RISES RAPIDLY. THIS IS ESPECIALLY TRUE IF YOU DON'T HAVE A NAV DISPLAY TO ENHANCE YOUR SITUATIONAL AWARENESS. ANOTHER CONCERN IS THAT IF THE NAV MODE IS USED TO CORRECT BACK TO COURSE YOU HAVE TO SWITCH TO NAV TO DO SO AND THEN BACK TO RADIAL TO INTERCEPT THE LOC. THIS IS TIME CONSUMING, PLUS, HOW DO YOU INTERCEPT A COURSE TO AN ARC? THERE ARE APCHS IN MEXICO THAT ALSO USE ACR'S TO GET ALIGNED WITH FINAL SO THIS COULD BE A PROB THERE ALSO. WHAT IS PARTICULARLY ONEROUS ABOUT MTJ THOUGH IS THAT THERE IS NO RADAR ON THE APCH SO YOU ARE REALLY ON YOUR OWN. HOPEFULLY IN MEX SOMEONE WOULD NOTIFY YOU. THERE IS NO INFO IN THE OPERATING MANUAL ABOUT WHEN TO ARM THE LOC. THE S80 IS PROBABLY DESIGNED TO PROPERLY INTERCEPT THE LOC WHEN IT IS ON AN INTERCEPT COURSE. WE BOTH FLEW THE F100 AND BOTH REMEMBER THERE IS NO PROB ARMING THE LOC WHEN USING THE NAV MODE. HOWEVER, IT APPEARS THAT THE S80 IS NOT. IF THIS IS THE CASE, I THINK THAT A MESSAGE SHOULD BE ADDED TO ALL S80 FLT PLANS SO THAT CREWS ARE MADE AWARE OF THE PROB. ALL THE APCHS THAT I CAN THINK OF THAT USE AN ARC ARE IN MOUNTAINOUS TERRAIN AND A MISTAKE COULD BE DISASTROUS.

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.