Air carrier medium large transport altitude deviation overshot crossing restriction not met.

Attributes
ACN	190154
Time
Date	199109
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : lax
State Reference	CA
Altitude	msl bound lower : 7500 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival : profile descent
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 80 flight time total : 13000 flight time type : 80
ASRS Report	190154
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 80 flight time total : 14000 flight time type : 500
ASRS Report	190096
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance non adherence : published procedure
Independent Detector	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:

We were on a civet 2 arrival to lax, and cleared to intercept 24R ILS, maintain 10000 ft. By the time we were cleared the 24R ILS approach, we had gone slightly above the GS. After clearance for the approach, I engaged the approach mode of the autoplt. Even though we were slightly above the GS, the autoplt captured the GS and descended to get on the GS. What a descent! The aircraft pitched over an excessive amount and dove for the GS, the airspeed increased to above 250 KTS (285) while I frantically tried to put the autoplt on vertical speed or altitude hold and extended the speed brakes. When I realized that I could not deprogram the autoplt from the approach mode, I disconnected the autoplt and leveled the airplane. However, by this time, we had descended to 7500 ft before we got to denay as the autoplt had overcompensated and had gone below the GS. The first officer told me that the only way to get out of the approach mode is to disconnect the autoplt and turn off the flight directors. I am fairly new in the airplane, had never been told this before, and had never flown an airplane with an autoplt which could not be deprogrammed once engaged on a particular mode. I consider this a less than desirable design feature and I wish someone had told me this earlier.

Original NASA ASRS Text

Title: ACR MLG ALT DEV OVERSHOT XING RESTRICTION NOT MET.

Narrative: WE WERE ON A CIVET 2 ARR TO LAX, AND CLRED TO INTERCEPT 24R ILS, MAINTAIN 10000 FT. BY THE TIME WE WERE CLRED THE 24R ILS APCH, WE HAD GONE SLIGHTLY ABOVE THE GS. AFTER CLRNC FOR THE APCH, I ENGAGED THE APCH MODE OF THE AUTOPLT. EVEN THOUGH WE WERE SLIGHTLY ABOVE THE GS, THE AUTOPLT CAPTURED THE GS AND DSNDED TO GET ON THE GS. WHAT A DSCNT! THE ACFT PITCHED OVER AN EXCESSIVE AMOUNT AND DOVE FOR THE GS, THE AIRSPD INCREASED TO ABOVE 250 KTS (285) WHILE I FRANTICALLY TRIED TO PUT THE AUTOPLT ON VERT SPD OR ALT HOLD AND EXTENDED THE SPD BRAKES. WHEN I REALIZED THAT I COULD NOT DEPROGRAM THE AUTOPLT FROM THE APCH MODE, I DISCONNECTED THE AUTOPLT AND LEVELED THE AIRPLANE. HOWEVER, BY THIS TIME, WE HAD DSNDED TO 7500 FT BEFORE WE GOT TO DENAY AS THE AUTOPLT HAD OVERCOMPENSATED AND HAD GONE BELOW THE GS. THE FO TOLD ME THAT THE ONLY WAY TO GET OUT OF THE APCH MODE IS TO DISCONNECT THE AUTOPLT AND TURN OFF THE FLT DIRECTORS. I AM FAIRLY NEW IN THE AIRPLANE, HAD NEVER BEEN TOLD THIS BEFORE, AND HAD NEVER FLOWN AN AIRPLANE WITH AN AUTOPLT WHICH COULD NOT BE DEPROGRAMMED ONCE ENGAGED ON A PARTICULAR MODE. I CONSIDER THIS A LESS THAN DESIRABLE DESIGN FEATURE AND I WISH SOMEONE HAD TOLD ME THIS EARLIER.

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.