Narrative:

The flight was on an assigned heading of 360 degrees; on a right base for runway 29L at lhr. Autopilot (a/P) was on. We were level at our assigned altitude of 4;000 feet. A few seconds later; we were given an intercept heading of 070 degrees and 'cleared to intercept the localizer.' I armed the localizer and made the callout to my crew. Shortly thereafter; ATC told us to 'descend on the glidepath; cleared for the ILS 29L at lhr.' I pushed the app button to arm the G/south and saw the G/south armed on the FMA. I called this out to my crew and the first officer said something muffled that I took to mean that he agreed. I heard nothing from the international relief officer. The localizer broke case and started to come in. I glanced out the window to the one o'clock position to try to visually acquire the runway environment; but the early morning sun was making it difficult to acquire it visually. I glanced down to the FMC to check my distance to the runway but I was distracted to see the G/south was about 1 dot low and dropping. Wanting to acquire the G/south now that the localizer was captured; I temporarily set 1;000 feet in the altitude window and announced 'flch' (flight level change). To assist with the descent; I partially deployed some speedbrakes. I made the announcement that we were high and the first officer asked what altitude we were descending to. I replied that I was descending to the G/south but during this discussion; we were now almost 2 dots low. The first officer commented he thought we were on a false G/south as the G/south was climbing up again. The international relief officer said he thought that ATC cleared us to 3;000 feet. I set 3;000 feet in the altitude window as I leveled off and retracted the speedbrakes. To that the first officer and I replied that we did not hear that clearance. On the localizer at 3;000 feet; (no lower); I disengaged the a/P and hand flew for a few seconds. Now that we were on localizer and properly positioned to intercept the G/south from below; I reengaged the a/P; called out and pushed the app mode button and confirmed the G/south was armed. Both crewmembers agreed. A few moments later approach control turned us over to lhr tower frequency and tower told us to 'maintain 3;000 feet until G/south was captured; follow the G/south.' a few moments after that; tower 'cleared us to land runway 29L lhr.' the a/P flew down the localizer and G/south normally. A 1;000 feet I disengaged the a/P and hand flew the jet to a normal landing.

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Original NASA ASRS Text

Title: A B777 received a LHR ATC clearance 'Intercept the Runway 9L Localizer; descend on Glideslope' so the Captain engaged APP but because they appeared high on Glideslope he began a FLCH descent to recapture it. The First Officer and IRO realized they were captured a false glideslope so they leveled and re-intercepted.

Narrative: The flight was on an assigned heading of 360 degrees; on a right base for Runway 29L at LHR. Autopilot (A/P) was on. We were level at our assigned altitude of 4;000 feet. A few seconds later; we were given an intercept heading of 070 degrees and 'Cleared to intercept the LOC.' I armed the LOC and made the callout to my crew. Shortly thereafter; ATC told us to 'Descend on the glidepath; cleared for the ILS 29L at LHR.' I pushed the APP button to arm the G/S and saw the G/S armed on the FMA. I called this out to my crew and the First Officer said something muffled that I took to mean that he agreed. I heard nothing from the IRO. The LOC broke case and started to come in. I glanced out the window to the one o'clock position to try to visually acquire the runway environment; but the early morning sun was making it difficult to acquire it visually. I glanced down to the FMC to check my distance to the runway but I was distracted to see the G/S was about 1 dot low and dropping. Wanting to acquire the G/S now that the LOC was captured; I temporarily set 1;000 feet in the ALT window and announced 'FLCH' (Flight Level Change). To assist with the descent; I partially deployed some speedbrakes. I made the announcement that we were high and the First Officer asked what altitude we were descending to. I replied that I was descending to the G/S but during this discussion; we were now almost 2 dots low. The First Officer commented he thought we were on a false G/S as the G/S was climbing up again. The IRO said he thought that ATC cleared us to 3;000 feet. I set 3;000 feet in the ALT window as I leveled off and retracted the speedbrakes. To that the First Officer and I replied that we did not hear that clearance. On the LOC at 3;000 feet; (no lower); I disengaged the A/P and hand flew for a few seconds. Now that we were on LOC and properly positioned to intercept the G/S from below; I reengaged the A/P; called out and pushed the APP mode button and confirmed the G/S was armed. Both crewmembers agreed. A few moments later Approach Control turned us over to LHR Tower frequency and tower told us to 'maintain 3;000 feet until G/S was captured; follow the G/S.' A few moments after that; Tower 'cleared us to land Runway 29L LHR.' The A/P flew down the LOC and G/S normally. A 1;000 feet I disengaged the A/P and hand flew the jet to a normal 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.