B747 captain and relief first officer reported they descended below glideslope in flch mode on an IL...

Narrative:

I was pilot flying; weather IMC with haze; autopilot on during approach. We were given a heading to intercept final approach course at about 2;500 feet and cleared to descend to 1;600 feet. I armed the approach and noted the first officer set 1;600 in altitude window. Aircraft intercepted localizer and we were below glideslope. At proper speed. I checked that the localizer was captured; glideslope was armed and autopilot engaged. I called for landing gear down and landing checklist at about 1;800 feet; still below glideslope and descending in flch. After arming the speedbrakes I looked at intruments to see we were at 1;600 feet and the aircraft had not captured the desired altitude. I looked at the alitude window and the pilot monitoring had set the touchdown altitude before capturing the glideslope and before I called for it. I disconnected the autopilot and manually climbed back to 1;600 feet. We were at about 1;400 feet at the lowest point. At about the same time we captured the glideslope and I flew the approach to an unevenful landing.

Original NASA ASRS Text

Title: B747 Captain and Relief First Officer reported they descended below glideslope in FLCH mode on an ILS approach when the flying First Officer set field elevation before glideslope capture.

Narrative: I was pilot flying; weather IMC with haze; autopilot on during approach. We were given a heading to intercept final approach course at about 2;500 feet and cleared to descend to 1;600 feet. I armed the approach and noted the First Officer set 1;600 in altitude window. Aircraft intercepted LOC and we were below glideslope. At proper speed. I checked that the LOC was captured; glideslope was armed and autopilot engaged. I called for landing gear down and Landing Checklist at about 1;800 feet; still below glideslope and descending in FLCH. After arming the speedbrakes I looked at intruments to see we were at 1;600 feet and the aircraft had not captured the desired altitude. I looked at the alitude window and the pilot monitoring had set the touchdown altitude before capturing the glideslope and before I called for it. I disconnected the autopilot and manually climbed back to 1;600 feet. We were at about 1;400 feet at the lowest point. At about the same time we captured the glideslope and I flew the approach to an unevenful landing.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1187945
Time
Date	201407
Place
Locale Reference	RKSI.Airport
State Reference	FO
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Not Flying First Officer
Experience	Flight Crew Last 90 Days 170 Flight Crew Total 12000 Flight Crew Type 500
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy

B747 captain and relief first officer reported they descended below glideslope in flch mode on an ILS approach when the flying first officer set field elevation before glideslope capture.