Narrative:

Conditions were VFR upon arrival and I expected a visual approach to the runway. I was cleared to intercept the localizer for runway 20 then cleared for the ILS approach. I had the runway in sight approximately 7 mi out on final. I was descending to initial approach altitude when I intercepted the localizer. Noticed I was on GS. I initiated a descent on the GS while maintaining visual contact with the runway. Just outside of the FAF; the controller advised I indicated low on the approach. I checked my instruments and showed on GS and on localizer. I maintained visual contact with the runway and analyzed the problem. The GS was erratic with the flag moving in and out of view. I expected the flag to be fully pulled as I was very close to the OM. I questioned the tower if there had been any reports of GS problems. They indicated they had just switched the approach and I was the first one to use it that day landing on runway 20. I leveled the aircraft. Approach reported I was still below normal GS altitude. I proceeded to fly visually to the airport and completed a normal landing. After review of the situation I think there were several opportunities to correct or avoid this problem. They are as follows: I should have prepared for a complete approach even though the airport was visual and the runway was in sight. This lured me into a complacency that may have contributed to not reviewing the charts as completely as I should have. I should not have descended below the initial approach altitude until confirming I had passed the OM and the altitude had checked at the FAF; irregardless of the GS indication. The visual conditions with the runway in sight may have contributed to this. The aircraft had been down for maintenance and I had not flown it for a couple of months. While I was proficient with takeoff and lndgs I had not made an ILS approach in this aircraft in a while. There is not one at my home airfield. I fly EFIS/FMS aircraft professionally and find my instrument scan not as effective as it used to be. EFIS/FMS uses more of an information scan where conventional aircraft require a disciplined instrument scan. It is possible I did not see a GS flag that appeared intermittently when ATC brought the low altitude to my attention. The flag moved in and out of view. If I locked on the GS with a weak signal; the GS nulls to the centered position making it look like you are on GS. I will never allow this to happen again. I have been flying for 35 yrs and have never had an incident or violation of any kind. I operate with very disciplined company sops. I needed to remind myself to operate with the same disciplines when operating GA aircraft. The visual conditions created some complacency and I just assumed a straight in approach to the runway would be all that was required. Had there been a low WX approach I am sure I would have double-checked everything in preparation for the approach. I need to do this every time regardless of WX conditions. I recognize that had this been in low visibility conditions and had the tower not notified me of my altitude; there could have been serious safety ramifications. This was a wake up call to treat recreational GA flying with the same degree of intensity as professional flying. A bad decision can be just as deadly. The aircraft was never in a dangerous position and would not have been out of bounds for a visual approach without the ILS equipment. I did learn a valuable lesson and will not repeat this type of error.

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Original NASA ASRS Text

Title: PA34 PILOT REPORTS GETTING WELL BELOW GS DURING AN ILS APPROACH IN VISUAL CONDITIONS.

Narrative: CONDITIONS WERE VFR UPON ARR AND I EXPECTED A VISUAL APCH TO THE RWY. I WAS CLRED TO INTERCEPT THE LOC FOR RWY 20 THEN CLRED FOR THE ILS APCH. I HAD THE RWY IN SIGHT APPROX 7 MI OUT ON FINAL. I WAS DSNDING TO INITIAL APCH ALT WHEN I INTERCEPTED THE LOC. NOTICED I WAS ON GS. I INITIATED A DSCNT ON THE GS WHILE MAINTAINING VISUAL CONTACT WITH THE RWY. JUST OUTSIDE OF THE FAF; THE CTLR ADVISED I INDICATED LOW ON THE APCH. I CHKED MY INSTS AND SHOWED ON GS AND ON LOC. I MAINTAINED VISUAL CONTACT WITH THE RWY AND ANALYZED THE PROB. THE GS WAS ERRATIC WITH THE FLAG MOVING IN AND OUT OF VIEW. I EXPECTED THE FLAG TO BE FULLY PULLED AS I WAS VERY CLOSE TO THE OM. I QUESTIONED THE TWR IF THERE HAD BEEN ANY RPTS OF GS PROBS. THEY INDICATED THEY HAD JUST SWITCHED THE APCH AND I WAS THE FIRST ONE TO USE IT THAT DAY LNDG ON RWY 20. I LEVELED THE ACFT. APCH RPTED I WAS STILL BELOW NORMAL GS ALT. I PROCEEDED TO FLY VISUALLY TO THE ARPT AND COMPLETED A NORMAL LNDG. AFTER REVIEW OF THE SIT I THINK THERE WERE SEVERAL OPPORTUNITIES TO CORRECT OR AVOID THIS PROB. THEY ARE AS FOLLOWS: I SHOULD HAVE PREPARED FOR A COMPLETE APCH EVEN THOUGH THE ARPT WAS VISUAL AND THE RWY WAS IN SIGHT. THIS LURED ME INTO A COMPLACENCY THAT MAY HAVE CONTRIBUTED TO NOT REVIEWING THE CHARTS AS COMPLETELY AS I SHOULD HAVE. I SHOULD NOT HAVE DSNDED BELOW THE INITIAL APCH ALT UNTIL CONFIRMING I HAD PASSED THE OM AND THE ALT HAD CHKED AT THE FAF; IRREGARDLESS OF THE GS INDICATION. THE VISUAL CONDITIONS WITH THE RWY IN SIGHT MAY HAVE CONTRIBUTED TO THIS. THE ACFT HAD BEEN DOWN FOR MAINT AND I HAD NOT FLOWN IT FOR A COUPLE OF MONTHS. WHILE I WAS PROFICIENT WITH TKOF AND LNDGS I HAD NOT MADE AN ILS APCH IN THIS ACFT IN A WHILE. THERE IS NOT ONE AT MY HOME AIRFIELD. I FLY EFIS/FMS ACFT PROFESSIONALLY AND FIND MY INST SCAN NOT AS EFFECTIVE AS IT USED TO BE. EFIS/FMS USES MORE OF AN INFO SCAN WHERE CONVENTIONAL ACFT REQUIRE A DISCIPLINED INST SCAN. IT IS POSSIBLE I DID NOT SEE A GS FLAG THAT APPEARED INTERMITTENTLY WHEN ATC BROUGHT THE LOW ALT TO MY ATTN. THE FLAG MOVED IN AND OUT OF VIEW. IF I LOCKED ON THE GS WITH A WEAK SIGNAL; THE GS NULLS TO THE CTRED POS MAKING IT LOOK LIKE YOU ARE ON GS. I WILL NEVER ALLOW THIS TO HAPPEN AGAIN. I HAVE BEEN FLYING FOR 35 YRS AND HAVE NEVER HAD AN INCIDENT OR VIOLATION OF ANY KIND. I OPERATE WITH VERY DISCIPLINED COMPANY SOPS. I NEEDED TO REMIND MYSELF TO OPERATE WITH THE SAME DISCIPLINES WHEN OPERATING GA ACFT. THE VISUAL CONDITIONS CREATED SOME COMPLACENCY AND I JUST ASSUMED A STRAIGHT IN APCH TO THE RWY WOULD BE ALL THAT WAS REQUIRED. HAD THERE BEEN A LOW WX APCH I AM SURE I WOULD HAVE DOUBLE-CHKED EVERYTHING IN PREPARATION FOR THE APCH. I NEED TO DO THIS EVERY TIME REGARDLESS OF WX CONDITIONS. I RECOGNIZE THAT HAD THIS BEEN IN LOW VISIBILITY CONDITIONS AND HAD THE TWR NOT NOTIFIED ME OF MY ALT; THERE COULD HAVE BEEN SERIOUS SAFETY RAMIFICATIONS. THIS WAS A WAKE UP CALL TO TREAT RECREATIONAL GA FLYING WITH THE SAME DEGREE OF INTENSITY AS PROFESSIONAL FLYING. A BAD DECISION CAN BE JUST AS DEADLY. THE ACFT WAS NEVER IN A DANGEROUS POS AND WOULD NOT HAVE BEEN OUT OF BOUNDS FOR A VISUAL APCH WITHOUT THE ILS EQUIP. I DID LEARN A VALUABLE LESSON AND WILL NOT REPEAT THIS TYPE OF ERROR.

Data retrieved from NASA's ASRS site as of January 2009 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.