Large transport flight crew descends below assigned altitude.

Attributes
ACN	316080
Time
Date	199509
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mco
State Reference	FL
Altitude	msl bound lower : 26600 msl bound upper : 27000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 100 flight time total : 12000 flight time type : 400
ASRS Report	316080
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : became reoriented
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ZJX initially assigned a descent from FL310 to FL280. Prior to reaching FL280 reassigned to FL270. Captain was flying. I made standard altitude callouts of '2000 ft to go' and '1000 ft to go.' captain acknowledged both calls and began to slow rate of descent at approximately 27500 ft MSL. I went back to checking for icing on the wiper blades, turned on engine anti- ice. Also was checking radar as captain was turning southwest to avoid a cell. Then I heard the altitude alert, looked up and noted our altitude at FL267. Called 'altitude, altitude' and captain disengaged autoplt and initiated recovery at approximately FL266. Captain re-established level flight at FL270 and we continued on the leese 7 arrival to mco. In retrospect, given the distrs of WX (ice and thunderstorms), I should have crosschecked the altitude more and not assumed that a slowing rate of descent meant level off.

Original NASA ASRS Text

Title: LGT FLC DSNDS BELOW ASSIGNED ALT.

Narrative: ZJX INITIALLY ASSIGNED A DSCNT FROM FL310 TO FL280. PRIOR TO REACHING FL280 REASSIGNED TO FL270. CAPT WAS FLYING. I MADE STANDARD ALT CALLOUTS OF '2000 FT TO GO' AND '1000 FT TO GO.' CAPT ACKNOWLEDGED BOTH CALLS AND BEGAN TO SLOW RATE OF DSCNT AT APPROX 27500 FT MSL. I WENT BACK TO CHKING FOR ICING ON THE WIPER BLADES, TURNED ON ENG ANTI- ICE. ALSO WAS CHKING RADAR AS CAPT WAS TURNING SW TO AVOID A CELL. THEN I HEARD THE ALT ALERT, LOOKED UP AND NOTED OUR ALT AT FL267. CALLED 'ALT, ALT' AND CAPT DISENGAGED AUTOPLT AND INITIATED RECOVERY AT APPROX FL266. CAPT RE-ESTABLISHED LEVEL FLT AT FL270 AND WE CONTINUED ON THE LEESE 7 ARR TO MCO. IN RETROSPECT, GIVEN THE DISTRS OF WX (ICE AND TSTMS), I SHOULD HAVE XCHKED THE ALT MORE AND NOT ASSUMED THAT A SLOWING RATE OF DSCNT MEANT LEVEL OFF.

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.