Narrative:

We were getting close to the FAF and the captain called for gear down which I did and then went through the before landing checks. I glanced at the altimeter occasionally and we were descending normally. I was told to go to tower. As I switched over to tower the captain says 'where did my GS go?' I noticed we were at 900 ft with the GS at full deflection above us and then realized the captain had been descending without being on the GS. The captain was beginning a leveloff and slow climb as I called tower and was given an immediate low altitude alert and told to climb and maintain 1500 ft. My first thought was of the wires crossing our approach which were at 542 ft. We climbed to 1300 ft and intercepted the GS and landed safely. My thoughts were how could I have not seen the fact that we were not on GS and if we were on it initially why didn't we get a call of 'GS' from the GPWS voice when we deviated far from it. What I realized was that when I was busy looking outside and then doing my checklist duties the captain must not have leveled off at the 2500 ft to intercept the GS; but somehow let the autoplt continue down at the set vertical speed so the GS never was captured. Also important to me was that I was watching the altimeter fairly intently as we approached the minimums and I was doing my standard callouts except I never checked or said 'on localizer; on GS' which I usually do on minimums approachs. I never noticed immediately to the left of the altimeter on the EFIS that there was not a GS indication. I just assumed that the airplane was on the GS because we had been descending. I have been flying with this captain; who is 40 yrs my senior; for almost 8 yrs and we are very comfortable to the point of complacency with each other. This episode has taught me a very important lesson in keeping my scan going even when I am the PNF. I know we got closer to those power lines than we should have.

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Original NASA ASRS Text

Title: G200 FLT CREW DESCENDED ON THE ILS LOC; REMAINING BELOW GS UNTIL REACHING 900 FT. LOW ALT ALERT WAS ISSUED BY TWR AND FLT CREW CLIMBED BACK TO GS.

Narrative: WE WERE GETTING CLOSE TO THE FAF AND THE CAPT CALLED FOR GEAR DOWN WHICH I DID AND THEN WENT THROUGH THE BEFORE LNDG CHKS. I GLANCED AT THE ALTIMETER OCCASIONALLY AND WE WERE DSNDING NORMALLY. I WAS TOLD TO GO TO TWR. AS I SWITCHED OVER TO TWR THE CAPT SAYS 'WHERE DID MY GS GO?' I NOTICED WE WERE AT 900 FT WITH THE GS AT FULL DEFLECTION ABOVE US AND THEN REALIZED THE CAPT HAD BEEN DSNDING WITHOUT BEING ON THE GS. THE CAPT WAS BEGINNING A LEVELOFF AND SLOW CLB AS I CALLED TWR AND WAS GIVEN AN IMMEDIATE LOW ALT ALERT AND TOLD TO CLB AND MAINTAIN 1500 FT. MY FIRST THOUGHT WAS OF THE WIRES XING OUR APCH WHICH WERE AT 542 FT. WE CLBED TO 1300 FT AND INTERCEPTED THE GS AND LANDED SAFELY. MY THOUGHTS WERE HOW COULD I HAVE NOT SEEN THE FACT THAT WE WERE NOT ON GS AND IF WE WERE ON IT INITIALLY WHY DIDN'T WE GET A CALL OF 'GS' FROM THE GPWS VOICE WHEN WE DEVIATED FAR FROM IT. WHAT I REALIZED WAS THAT WHEN I WAS BUSY LOOKING OUTSIDE AND THEN DOING MY CHKLIST DUTIES THE CAPT MUST NOT HAVE LEVELED OFF AT THE 2500 FT TO INTERCEPT THE GS; BUT SOMEHOW LET THE AUTOPLT CONTINUE DOWN AT THE SET VERT SPD SO THE GS NEVER WAS CAPTURED. ALSO IMPORTANT TO ME WAS THAT I WAS WATCHING THE ALTIMETER FAIRLY INTENTLY AS WE APCHED THE MINIMUMS AND I WAS DOING MY STANDARD CALLOUTS EXCEPT I NEVER CHKED OR SAID 'ON LOC; ON GS' WHICH I USUALLY DO ON MINIMUMS APCHS. I NEVER NOTICED IMMEDIATELY TO THE L OF THE ALTIMETER ON THE EFIS THAT THERE WAS NOT A GS INDICATION. I JUST ASSUMED THAT THE AIRPLANE WAS ON THE GS BECAUSE WE HAD BEEN DSNDING. I HAVE BEEN FLYING WITH THIS CAPT; WHO IS 40 YRS MY SENIOR; FOR ALMOST 8 YRS AND WE ARE VERY COMFORTABLE TO THE POINT OF COMPLACENCY WITH EACH OTHER. THIS EPISODE HAS TAUGHT ME A VERY IMPORTANT LESSON IN KEEPING MY SCAN GOING EVEN WHEN I AM THE PNF. I KNOW WE GOT CLOSER TO THOSE PWR LINES THAN WE SHOULD HAVE.

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.