GA-small aircraft with faulty glideslope indication gets low altitude alert from controlled flight t...

Attributes
ACN	98407
Time
Date	198811
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : orl
State Reference	FL
Altitude	msl bound lower : 1000 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mco
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
Experience	flight time last 90 days : 20 flight time total : 360 flight time type : 20
ASRS Report	98407
Person 2
Affiliation	Other
Function	other personnel other
Qualification	pilot : private
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared for ILS 7 approach to orl, to maintain 2000' until G/south intercept. Received apparent G/south intercept and started to descend. Had needles crossed when controller called, said he had low altitude alert on me and asked to confirm that I was at 1000'. I confirmed 1000', he said I was to be at 2000'. I immediately commenced climb to approximately 1600'-1700' when actual G/south was intercepted. Copilot/safety pilot confirmed that I had the needles crossed descending prematurely to 1000'. Landing took place west/O incident. No conflict with terrain or obstacles. Continued descent west/O correction would have been serious but with safety pilot do not believe problem would have resulted. Problem caused by exclusive use of G/south indicator west/O considering DME or OM reading. Lesson learned not to rely on single indicator. Plane has single G/south receiver. I thought I was flying a perfect ILS approach and was unpleasantly surprised at low altitude alert. Very valuable lesson. Will have G/south checked/repaired.

Original NASA ASRS Text

Title: GA-SMA WITH FAULTY GLIDESLOPE INDICATION GETS LOW ALT ALERT FROM CONTROLLED FLT TOWARD TERRAIN.

Narrative: CLRED FOR ILS 7 APCH TO ORL, TO MAINTAIN 2000' UNTIL G/S INTERCEPT. RECEIVED APPARENT G/S INTERCEPT AND STARTED TO DSND. HAD NEEDLES CROSSED WHEN CTLR CALLED, SAID HE HAD LOW ALT ALERT ON ME AND ASKED TO CONFIRM THAT I WAS AT 1000'. I CONFIRMED 1000', HE SAID I WAS TO BE AT 2000'. I IMMEDIATELY COMMENCED CLB TO APPROX 1600'-1700' WHEN ACTUAL G/S WAS INTERCEPTED. COPLT/SAFETY PLT CONFIRMED THAT I HAD THE NEEDLES CROSSED DSNDING PREMATURELY TO 1000'. LNDG TOOK PLACE W/O INCIDENT. NO CONFLICT WITH TERRAIN OR OBSTACLES. CONTINUED DSCNT W/O CORRECTION WOULD HAVE BEEN SERIOUS BUT WITH SAFETY PLT DO NOT BELIEVE PROB WOULD HAVE RESULTED. PROB CAUSED BY EXCLUSIVE USE OF G/S INDICATOR W/O CONSIDERING DME OR OM READING. LESSON LEARNED NOT TO RELY ON SINGLE INDICATOR. PLANE HAS SINGLE G/S RECEIVER. I THOUGHT I WAS FLYING A PERFECT ILS APCH AND WAS UNPLEASANTLY SURPRISED AT LOW ALT ALERT. VERY VALUABLE LESSON. WILL HAVE G/S CHKED/REPAIRED.

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.

GA-small aircraft with faulty glideslope indication gets low altitude alert from controlled flight toward terrain.