Air carrier flight crew starts down GS before authority/authorized to do so.

Attributes
ACN	437782
Time
Date	199905
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : iah.ils
State Reference	TX
Altitude	msl single value : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : i90.tracon
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 92 flight time total : 6000 flight time type : 92
ASRS Report	437782
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 1800
ASRS Report	437871
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far non adherence : published procedure
Independent Detector	other flight crewa other flight crewb
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Arriving in iah on daisetta 3 arrival after reduced rest night at lga. At daisetta, captain could not get in on approach frequency due to congestion. When he was finally able to get in, we were given a lower altitude, an airspeed reduction and a vector for approach to runway 15L in shotgun fashion. I scrambled to get down and slow down in a short distance. As we were about to level off we were given another altitude and vector to intercept the localizer. As we were intercepting the localizer 1 - 1 1/2 dots below GS, we were cleared for the approach approximately 22-23 mi out and 3 mi in trail of our traffic. I believe due to my fatigue, feeling the pressure to get down and slow down and our close proximity to traffic, I hit the approach button on the MCP and we captured the GS just prior to mkaye. This caused us to descend below 5000 ft just prior to mkaye. At first, we were both surprised at going below 5000 ft and then realized we had captured the GS when we didn't want to yet. I disconnected the autoplt and the captain reset the flight director and MCP and we flew the rest of the approach without incident.

Original NASA ASRS Text

Title: ACR FLC STARTS DOWN GS BEFORE AUTH TO DO SO.

Narrative: ARRIVING IN IAH ON DAISETTA 3 ARR AFTER REDUCED REST NIGHT AT LGA. AT DAISETTA, CAPT COULD NOT GET IN ON APCH FREQ DUE TO CONGESTION. WHEN HE WAS FINALLY ABLE TO GET IN, WE WERE GIVEN A LOWER ALT, AN AIRSPD REDUCTION AND A VECTOR FOR APCH TO RWY 15L IN SHOTGUN FASHION. I SCRAMBLED TO GET DOWN AND SLOW DOWN IN A SHORT DISTANCE. AS WE WERE ABOUT TO LEVEL OFF WE WERE GIVEN ANOTHER ALT AND VECTOR TO INTERCEPT THE LOC. AS WE WERE INTERCEPTING THE LOC 1 - 1 1/2 DOTS BELOW GS, WE WERE CLRED FOR THE APCH APPROX 22-23 MI OUT AND 3 MI IN TRAIL OF OUR TFC. I BELIEVE DUE TO MY FATIGUE, FEELING THE PRESSURE TO GET DOWN AND SLOW DOWN AND OUR CLOSE PROX TO TFC, I HIT THE APCH BUTTON ON THE MCP AND WE CAPTURED THE GS JUST PRIOR TO MKAYE. THIS CAUSED US TO DSND BELOW 5000 FT JUST PRIOR TO MKAYE. AT FIRST, WE WERE BOTH SURPRISED AT GOING BELOW 5000 FT AND THEN REALIZED WE HAD CAPTURED THE GS WHEN WE DIDN'T WANT TO YET. I DISCONNECTED THE AUTOPLT AND THE CAPT RESET THE FLT DIRECTOR AND MCP AND WE FLEW THE REST OF THE APCH WITHOUT INCIDENT.

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.