With an unarmed approach coupler, an A319 pilot in command allows the flight to get below the glide slope and slow at 800 feet MSL while on approach to runway 25L at LAX.
Synopsis
With an unarmed approach coupler, an A319 pilot in command allows the flight to get below the glide slope and slow at 800 feet MSL while on approach to runway 25L at LAX.
Narrative
Rewritten in plain English from NASA’s original all-caps telegraphic report — facts, figures, and terminology preserved.
After a well executed STAR (MITTS runway 25L) into LAX (speed restrictions were what I would have chosen); while descending and slowing from 3500 feet to 1900 feet just slightly above glide slope; I called for local mode and it was captured. I was in open descent at about 2500 feet; called for the gear and before landing checklist as I slowed to 180 knots to the marker as ATC requested.
1 mile to marker and called for managed speed to slow and told the first officer to put the altitude window to 1000 feet (not sure if the first officer actually put in 1000 feet or something lower; I did not verify the altitude as everything was very normal and stabilized) to prevent an autothrottle and autopilot level-off at the marker altitude of 1900 feet. I did realize I was still in open descent but was 1/2 dot above the glide slope and the airplane was slowing to managed speed and full flaps were extended at about 1500 feet. All the while the airplane stayed on the glide slope even then though I had not armed the approach mode.
While still in open descent at about 800 feet; I saw I was slightly below glide slope; kicked off autopilot; and brought the nose up. I was surprised to see that my speed had slowed to reference-10 so I pushed the nose down to increase airspeed and got the glide slope warning. I took off the autothrottles; brought up the power; and leveled off at about 500 feet; caught the glide slope; and continued the approach. Landing was normal. I got no stall warning and no call from the tower. We did end up going 2 dots below the glide slope; and as slow as reference-12. This was caused because I did not call to arm the approach mode when I should have.
Seeing the airplane descending on the glide slope on a clear day; I was lulled into a false sense. Also; I allowed the first officer to leave me in open descent when I should have been in vertical speed just outside the marker and just above the glide slope. I have never had a problem with stabilized approach before from the low energy side. A lesson learned. Next time I will go around.
Show the original NASA report (verbatim, telegraphic)
AFTER A WELL EXECUTED STAR (MITTS RWY 25L) INTO LAX (SPD RESTRS WERE WHAT I WOULD HAVE CHOSEN); WHILE DSNDING AND SLOWING FROM 3500 FT TO 1900 FT JUST SLIGHTLY ABOVE GS; I CALLED FOR LOC MODE AND IT WAS CAPTURED. I WAS IN OPEN DSCNT AT ABOUT 2500 FT; CALLED FOR THE GEAR AND BEFORE LNDG CHKLIST AS I SLOWED TO 180 KTS TO THE MARKER AS ATC REQUESTED. 1 MI TO MARKER AND CALLED FOR MANAGED SPD TO SLOW AND TOLD THE FO TO PUT THE ALT WINDOW TO 1000 FT (NOT SURE IF THE FO ACTUALLY PUT IN 1000 FT OR SOMETHING LOWER; I DID NOT VERIFY THE ALT AS EVERYTHING WAS VERY NORMAL AND STABILIZED) TO PREVENT AN AUTOTHROTTLE AND AUTOPLT LEVELOFF AT THE MARKER ALT OF 1900 FT. I DID REALIZE I WAS STILL IN OPEN DSCNT BUT WAS 1/2 DOT ABOVE THE GS AND THE AIRPLANE WAS SLOWING TO MANAGED SPD AND FULL FLAPS WERE EXTENDED AT ABOUT 1500 FT. ALL THE WHILE THE AIRPLANE STAYED ON THE GS EVEN THEN THOUGH I HAD NOT ARMED THE APCH MODE. WHILE STILL IN OPEN DSCNT AT ABOUT 800 FT; I SAW I WAS SLIGHTLY BELOW GS; KICKED OFF AUTOPLT; AND BROUGHT THE NOSE UP. I WAS SURPRISED TO SEE THAT MY SPD HAD SLOWED TO REF-10 SO I PUSHED THE NOSE DOWN TO INCREASE AIRSPD AND GOT THE GS WARNING. I TOOK OFF THE AUTOTHROTTLES; BROUGHT UP THE PWR; AND LEVELED OFF AT ABOUT 500 FT; CAUGHT THE GS; AND CONTINUED THE APCH. LNDG WAS NORMAL. I GOT NO STALL WARNING AND NO CALL FROM THE TWR. WE DID END UP GOING 2 DOTS BELOW THE GS; AND AS SLOW AS REF-12. THIS WAS CAUSED BECAUSE I DID NOT CALL TO ARM THE APCH MODE WHEN I SHOULD HAVE. SEEING THE AIRPLANE DSNDING ON THE GS ON A CLR DAY; I WAS LULLED INTO A FALSE SENSE. ALSO; I ALLOWED THE FO TO LEAVE ME IN OPEN DSCNT WHEN I SHOULD HAVE BEEN IN VERT SPD JUST OUTSIDE THE MARKER AND JUST ABOVE THE GS. I HAVE NEVER HAD A PROB WITH STABILIZED APCH BEFORE FROM THE LOW ENERGY SIDE. A LESSON LEARNED. NEXT TIME I WILL GO AROUND.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.