Medium large transport kept high on approach has problem re-engaging autoplt, altitude deviation.

Attributes
ACN	276545
Time
Date	199407
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 1500 msl bound upper : 2000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tower : bos
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 5000
ASRS Report	276545
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATIS advised runway 4R CAT ii operations in use with 1/4 mi visibility, -X west clg. ATC keeps up high with straight in approach. Crew briefs a CAT ii monitored approach. ATC gives descent clearance, and crew attempts a maximum rate descent to achieve profile. Autoplt was engaged during descent. It was becoming difficult to gain GS. Autoplt was disengaged to attempt hand flown GS intercept. When GS started to come into 'on profile' position autoplt engagement was attempted. Elevator/pitch mode was engaged but aileron/roll mode was difficult to engage. During the engagement attempt/problem aircraft descended through GS (by approximately 200-400 ft, approximately 1500-2000 ft MSL). Tower advised us of this low altitude alert as crew was correcting. Also, ATC advised tower visibility had increased to 2400 ft RVR, and a hand flown CAT I approach was successfully flown. It all comes down to a rushed approach is easy to take care of with a missed approach/go around and come back for a stabilized approach. I know better.

Original NASA ASRS Text

Title: MLG KEPT HIGH ON APCH HAS PROB RE-ENGAGING AUTOPLT, ALTDEV.

Narrative: ATIS ADVISED RWY 4R CAT II OPS IN USE WITH 1/4 MI VISIBILITY, -X W CLG. ATC KEEPS UP HIGH WITH STRAIGHT IN APCH. CREW BRIEFS A CAT II MONITORED APCH. ATC GIVES DSCNT CLRNC, AND CREW ATTEMPTS A MAX RATE DSCNT TO ACHIEVE PROFILE. AUTOPLT WAS ENGAGED DURING DSCNT. IT WAS BECOMING DIFFICULT TO GAIN GS. AUTOPLT WAS DISENGAGED TO ATTEMPT HAND FLOWN GS INTERCEPT. WHEN GS STARTED TO COME INTO 'ON PROFILE' POS AUTOPLT ENGAGEMENT WAS ATTEMPTED. ELEVATOR/PITCH MODE WAS ENGAGED BUT AILERON/ROLL MODE WAS DIFFICULT TO ENGAGE. DURING THE ENGAGEMENT ATTEMPT/PROB ACFT DSNDED THROUGH GS (BY APPROX 200-400 FT, APPROX 1500-2000 FT MSL). TWR ADVISED US OF THIS LOW ALT ALERT AS CREW WAS CORRECTING. ALSO, ATC ADVISED TWR VISIBILITY HAD INCREASED TO 2400 FT RVR, AND A HAND FLOWN CAT I APCH WAS SUCCESSFULLY FLOWN. IT ALL COMES DOWN TO A RUSHED APCH IS EASY TO TAKE CARE OF WITH A MISSED APCH/GAR AND COME BACK FOR A STABILIZED APCH. I KNOW BETTER.

Data retrieved from NASA's ASRS site as of July 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.