Night Departure with a Failing Attitude Indicator
You are the pilot flying a twin-engine turboprop on a night departure from a regional airport. Weather is 800 ft overcast, 2 km visibility, light rain, and the runway has no centreline lighting. Rotation and initial climb are normal. At 400 ft AGL, as you enter cloud, you notice the captain's attitude indicator has begun to show a slow, steady roll to the left that does not match the turn coordinator, the standby horizon, or the heading trend. The aircraft is climbing at 1,200 ft/min on runway heading according to the standby instruments. ATC has just issued a turn to 040 degrees for traffic. The first officer's primary display is serviceable. Autopilot is off.
1. What is the immediate threat, and how should the crew manage the failed instrument and the ATC turn?
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The threat is spatial disorientation from conflicting attitude information in IMC at low altitude. The captain's attitude indicator is unreliable because it disagrees with at least two independent sources. The crew should first declare the discrepancy and transfer control to the first officer's serviceable primary display, then cross-check the standby horizon and turn coordinator. Do not chase the faulty instrument. Acknowledge the ATC turn but request a delay or a heading that allows a shallow, standard-rate turn using the serviceable display and standby instruments. Reduce workload: engage the autopilot only if it is fed by a reliable source and its behaviour is monitored. Climb to a safe altitude before troubleshooting, and consider a return to the departure airport if the approach environment is marginal. The key judgement is to stop using the failed instrument as a primary reference and to avoid abrupt manoeuvres in cloud.
2. How should the crew decide whether to continue or return, and what information matters most?
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The decision should weigh the reliability of remaining attitude sources, the weather at destination and alternate, fuel, and crew workload. A single serviceable primary display plus a standby horizon is acceptable for continued flight only if both are cross-checked and the autopilot is not masking a fault. At 800 ft overcast with 2 km visibility, a return to a runway without centreline lighting is feasible but requires a stabilised approach and a clear go-around plan. The crew should consider the destination's weather, alternate availability, and whether a diversion airport has better conditions. If any doubt exists about the remaining instruments, return. The most important information is not the failed instrument's indication but the agreement of independent sources and the crew's capacity to fly a precise approach without distraction.