Narrative:

On a ferry flight from lax to san when we arrived in the san area the current ATIS WX was 800 broken, 5 mi haze and fog, temperature 68, dew point 57, wind 270 at 10, altimeter 29.91. With clearance from approach control we flew a localizer runway 27 approach to a missed approach due to being too high on the visual glide path at runway acquisition. This was caused by a low rate of descent from reebo to our MDA. Being a high minimum captain we flew the approach to my minimum, which are 760', 100' above published minimum of 660' MSL. We executed a missed approach with a vector from tower and then approach control vectored us for a second approach. With a localizer intercept just prior to reebo at 2100' assigned we were cleared for the localizer runway 27 approach. Realizing our problem of not having a high enough descent rate from reebo on the first approach and computing a vdp of 3.8 DME or 1 min 15 second at 140 KT, from reebo to the vdp. The descent of 1240' from reebo at 2000' to the MDA of 760' required a descent rate of greater than 1000 FPM to allow for transitions. With this in mind we crossed reebo on the localizer at 2000' in the landing confign and started a descent at 1500 FPM to our MDA. At 850' MSL tower advised us that we were generating a low altitude alert and the minimum altitude for our position was 660'. We leveled off at 800' and gained visual contact with the runway at 4 DME. Having already received clearance to land we then transitioned to a normal final and with the aid of the PAPI made a normal landing on runway 27. When we received the low altitude alert we checked all 3 altimeters and they agreed and were correctly set at 29.91. My concern in filing this report is to why the low altitude alert was generated some 190' above the published MDA or if it was generated due to our rate of descent, which is required to descend 1240' in 1 min 15 second in order to be at the MDA prior to or at the vdp. I am also concerned that the tower may have thought that we were attempting to go below published minimum in order to gain contact with the runway. This was not the case at all. With 800 broken and 5 mi there was adequate ceiling and visibility to fly the approach correctly. The problem was getting to the MDA at or prior to the vdp which required 1500 FPM rate of descent.

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Original NASA ASRS Text

Title: ACR MLG SETS OFF MSAW ALERT ON INSTRUMENT APCH WITH HIGH SINK RATE.

Narrative: ON A FERRY FLT FROM LAX TO SAN WHEN WE ARRIVED IN THE SAN AREA THE CURRENT ATIS WX WAS 800 BROKEN, 5 MI HAZE AND FOG, TEMPERATURE 68, DEW POINT 57, WIND 270 AT 10, ALTIMETER 29.91. WITH CLRNC FROM APCH CTL WE FLEW A LOC RWY 27 APCH TO A MISSED APCH DUE TO BEING TOO HIGH ON THE VISUAL GLIDE PATH AT RWY ACQUISITION. THIS WAS CAUSED BY A LOW RATE OF DSCNT FROM REEBO TO OUR MDA. BEING A HIGH MINIMUM CAPT WE FLEW THE APCH TO MY MINIMUM, WHICH ARE 760', 100' ABOVE PUBLISHED MINIMUM OF 660' MSL. WE EXECUTED A MISSED APCH WITH A VECTOR FROM TWR AND THEN APCH CTL VECTORED US FOR A SECOND APCH. WITH A LOC INTERCEPT JUST PRIOR TO REEBO AT 2100' ASSIGNED WE WERE CLRED FOR THE LOC RWY 27 APCH. REALIZING OUR PROBLEM OF NOT HAVING A HIGH ENOUGH DSCNT RATE FROM REEBO ON THE FIRST APCH AND COMPUTING A VDP OF 3.8 DME OR 1 MIN 15 SEC AT 140 KT, FROM REEBO TO THE VDP. THE DSCNT OF 1240' FROM REEBO AT 2000' TO THE MDA OF 760' REQUIRED A DSCNT RATE OF GREATER THAN 1000 FPM TO ALLOW FOR TRANSITIONS. WITH THIS IN MIND WE CROSSED REEBO ON THE LOC AT 2000' IN THE LNDG CONFIGN AND STARTED A DSCNT AT 1500 FPM TO OUR MDA. AT 850' MSL TWR ADVISED US THAT WE WERE GENERATING A LOW ALT ALERT AND THE MINIMUM ALT FOR OUR POSITION WAS 660'. WE LEVELED OFF AT 800' AND GAINED VISUAL CONTACT WITH THE RWY AT 4 DME. HAVING ALREADY RECEIVED CLRNC TO LAND WE THEN TRANSITIONED TO A NORMAL FINAL AND WITH THE AID OF THE PAPI MADE A NORMAL LNDG ON RWY 27. WHEN WE RECEIVED THE LOW ALT ALERT WE CHECKED ALL 3 ALTIMETERS AND THEY AGREED AND WERE CORRECTLY SET AT 29.91. MY CONCERN IN FILING THIS REPORT IS TO WHY THE LOW ALT ALERT WAS GENERATED SOME 190' ABOVE THE PUBLISHED MDA OR IF IT WAS GENERATED DUE TO OUR RATE OF DSCNT, WHICH IS REQUIRED TO DSND 1240' IN 1 MIN 15 SEC IN ORDER TO BE AT THE MDA PRIOR TO OR AT THE VDP. I AM ALSO CONCERNED THAT THE TWR MAY HAVE THOUGHT THAT WE WERE ATTEMPTING TO GO BELOW PUBLISHED MINIMUM IN ORDER TO GAIN CONTACT WITH THE RWY. THIS WAS NOT THE CASE AT ALL. WITH 800 BROKEN AND 5 MI THERE WAS ADEQUATE CEILING AND VISIBILITY TO FLY THE APCH CORRECTLY. THE PROBLEM WAS GETTING TO THE MDA AT OR PRIOR TO THE VDP WHICH REQUIRED 1500 FPM RATE OF DSCNT.

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.