Mode Confusion During a Late Runway Change
During a late runway change at night, a glass-cockpit twin is cleared to intercept the localizer for runway 09 and descend to 2,500 ft. The crew had briefed a different approach; the captain selects the new approach while the first officer programs the flight management system. The autopilot remains in altitude hold, but both pilots believe it is armed to capture the glideslope. The FMA shows ALT HOLD in green, not G/S. ATC clears the aircraft to 2,000 ft, and the captain increases the descent rate. At 1,200 ft AGL the EGPWS announces 'glideslope,' and the first officer says, 'I think we are not on the profile.' The captain replies, 'I have got it,' and continues. Company stabilized-approach criteria require a stable path by 1,000 ft in IMC and 500 ft in VMC; the weather is 4 km visibility with a 700 ft ceiling.
1. Identify the error chain and the situational-awareness failures that led to the EGPWS 'glideslope' warning.
Read the worked answer
The chain starts with a late runway change: the crew briefed one approach, then reprogrammed under time pressure. The autopilot was left in ALT HOLD, but both pilots assumed it was armed for glideslope capture. The FMA showed ALT HOLD, not G/S; because neither pilot verbalized and cross-checked the mode, the mode confusion persisted. ATC's descent clearance to 2,000 ft reinforced the captain's expectation of a normal profile, and the captain increased the descent rate without confirming the vertical mode. The first officer's 'I think we are not on the profile' was weak and late; the captain's 'I have got it' ended the challenge rather than inviting evidence. The EGPWS warning is the last link. Key situational-awareness failures are failure to monitor the FMA, failure to build a shared mental model after the runway change, and plan continuation. The trap is that the aircraft was doing what it was told, ALT HOLD, not what the crew thought.
2. How should the first officer have intervened, and what should the captain have done differently in leadership and communication?
Read the worked answer
The first officer should use a structured assertion: state the observation, the risk and the required action. For example: 'Captain, the FMA says ALT HOLD, not G/S. We are not on the glideslope and we are descending through 2,000 ft. I recommend a go-around.' This is specific and hard to dismiss. The first officer should also be prepared to take control if the captain does not respond, following the operator's escalation policy. The captain should have verbalized the mode after the runway change: 'We are in ALT HOLD; I will arm the approach and confirm capture.' When the first officer raised doubt, the captain should have asked for the evidence, not said 'I have got it.' Good leadership here means slowing down, assigning monitoring tasks and explicitly inviting challenge. The captain's authority is not threatened by a go-around; it is threatened by continuing an unstable approach. After landing, the debrief should focus on the mode confusion and communication, not blame.
3. Apply threat and error management: what threats, errors and countermeasures are present?
Read the worked answer
Threats: night, late runway change, high workload, expectation bias and a crew that had briefed a different approach. Errors: mode confusion, with ALT HOLD mistaken for G/S; failure to monitor the FMA; weak challenge; plan continuation. Countermeasures: a stabilized-approach briefing before the change; a 'mode, altitude, target' callout after every autopilot selection; explicit cross-check of the FMA by both pilots; a sterile-cockpit rule during reprogramming; and a hard go-around trigger at the EGPWS warning or at 1,000 ft in IMC or 500 ft in VMC if unstable. Threat and error management also means briefing the runway change as a new threat and reducing speed or delaying the approach if reprogramming cannot be completed calmly. The captain should treat the first officer's concern as valuable data. A safety report should capture the late change and the mode confusion so the operator can review approach-change procedures.