Premature descent on instrument approach. Controlled flight toward terrain. MSAW.

Attributes
ACN	109020
Time
Date	198904
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : btr
State Reference	LA
Altitude	msl bound lower : 1800 msl bound upper : 2000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : btr tower : btr
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial pilot : private
Experience	flight time last 90 days : 42 flight time total : 450 flight time type : 400
ASRS Report	109020
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure other spatial deviation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	flight crew : exited adverse environment flight crew : returned to intended course or assigned course flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

I was talking to btr approach heading 090 degrees, 6 or 7 DME south of the btr VOR. Approach was also talking to some other traffic and I started flying through the final approach course (localizer). I told approach and he said, 'turn 010 cleared for the localizer runway 4 back course, maintain 2100' until established on the localizer.' I acknowledged, glanced at the DME which said about 4 mi, got the localizer within 3 dots, and started descending to 720'. This approach has 2 step down points--from 2100 to 720' 5.5 DME from the localizer, and 720 to 560' 2.0 from the localizer. The approach controller told me to contact the tower and I did. Tower said, 'altitude alert. Check your altimeter. Btr altimeter 30.xx.' I climbed back up to 2100' and said, 'I thought I was cleared for the approach.' tower said, 'yes, but you're supposed to maintain 2100 until leiko (intersection 5.5 DME).' I checked my DME and realized that I had it in the local mode instead of rmt, which would have given me the DME off the station selected on the #1 navigation. I was watching the distance from the btr VOR instead of the distance from the localizer. I flipped the switch and saw I was still 7.8 from the localizer. What really caused the problem was not verifying that the DME was on the proper frequency before starting the approach. Including the DME in my scan would have showed the distance counting up instead of down. I was making an approach to my home field, so was not as vigilant as I should have been. When the controller said, 'maintain 2100 until established on the localizer,' it implies that once you are established you don't have to maintain 2100' anymore. 'Maintain 2100 until lieko' would have been more helpful. It would have let me know that we didn't think I was there yet, so I might have caught my error. I won't be complacent at a familiar field again!

Original NASA ASRS Text

Title: PREMATURE DESCENT ON INSTRUMENT APCH. CONTROLLED FLT TOWARD TERRAIN. MSAW.

Narrative: I WAS TALKING TO BTR APCH HDG 090 DEGS, 6 OR 7 DME S OF THE BTR VOR. APCH WAS ALSO TALKING TO SOME OTHER TFC AND I STARTED FLYING THROUGH THE FINAL APCH COURSE (LOC). I TOLD APCH AND HE SAID, 'TURN 010 CLRED FOR THE LOC RWY 4 BC, MAINTAIN 2100' UNTIL ESTABLISHED ON THE LOC.' I ACKNOWLEDGED, GLANCED AT THE DME WHICH SAID ABOUT 4 MI, GOT THE LOC WITHIN 3 DOTS, AND STARTED DSNDING TO 720'. THIS APCH HAS 2 STEP DOWN POINTS--FROM 2100 TO 720' 5.5 DME FROM THE LOC, AND 720 TO 560' 2.0 FROM THE LOC. THE APCH CTLR TOLD ME TO CONTACT THE TWR AND I DID. TWR SAID, 'ALT ALERT. CHK YOUR ALTIMETER. BTR ALTIMETER 30.XX.' I CLBED BACK UP TO 2100' AND SAID, 'I THOUGHT I WAS CLRED FOR THE APCH.' TWR SAID, 'YES, BUT YOU'RE SUPPOSED TO MAINTAIN 2100 UNTIL LEIKO (INTXN 5.5 DME).' I CHKED MY DME AND REALIZED THAT I HAD IT IN THE LCL MODE INSTEAD OF RMT, WHICH WOULD HAVE GIVEN ME THE DME OFF THE STATION SELECTED ON THE #1 NAV. I WAS WATCHING THE DISTANCE FROM THE BTR VOR INSTEAD OF THE DISTANCE FROM THE LOC. I FLIPPED THE SWITCH AND SAW I WAS STILL 7.8 FROM THE LOC. WHAT REALLY CAUSED THE PROB WAS NOT VERIFYING THAT THE DME WAS ON THE PROPER FREQ BEFORE STARTING THE APCH. INCLUDING THE DME IN MY SCAN WOULD HAVE SHOWED THE DISTANCE COUNTING UP INSTEAD OF DOWN. I WAS MAKING AN APCH TO MY HOME FIELD, SO WAS NOT AS VIGILANT AS I SHOULD HAVE BEEN. WHEN THE CTLR SAID, 'MAINTAIN 2100 UNTIL ESTABLISHED ON THE LOC,' IT IMPLIES THAT ONCE YOU ARE ESTABLISHED YOU DON'T HAVE TO MAINTAIN 2100' ANYMORE. 'MAINTAIN 2100 UNTIL LIEKO' WOULD HAVE BEEN MORE HELPFUL. IT WOULD HAVE LET ME KNOW THAT WE DIDN'T THINK I WAS THERE YET, SO I MIGHT HAVE CAUGHT MY ERROR. I WON'T BE COMPLACENT AT A FAMILIAR FIELD AGAIN!

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.