Pulling the roll disconnect changes which surfaces respond to the left yoke. With the disconnect engaged, the left yoke no longer drives the ailerons. Instead, its control authority is limited to the multifunction spoilers, which handle roll when the ailerons are disconnected. The elevator and rudder remain controlled by other surfaces or systems, not by the left yoke in this condition. So the left yoke operates only the multifunction spoilers.

The main idea is that the FMS builds its navigation solution by solving for position (x, y, z) and the receiver’s clock bias using range measurements to satellites. Each satellite provides one equation, so you need four independent measurements to determine four unknowns. That’s why four satellites with good geometry is the standard path. If you only have three satellites, you can’t resolve all four unknowns unless you bring in external information for one of them. Knowing altitude from air data fixes the vertical position, leaving three unknowns (x, y, and the clock bias) with three equations, which allows a valid solution. So the combination of four satellites with acceptable geometry, or three satellites plus air data altitude, is sufficient. The other options don’t provide enough information on their own: three satellites alone don’t resolve the clock bias; two satellites with delta altitude isn’t enough data; and four satellites alone is typically valid but doesn’t acknowledge the alternative that three satellites plus altitude can also work.

When a left or right pylon bleed leak is detected, the immediate, memorized action is to set thrust to idle. Dropping to idle reduces engine bleed air generation and the pressure in the affected line, which slows the rate of bleed air loss and helps maintain control and essential system operation while you address the leak. This quick action buys you time to follow the QRH procedures for isolation or remediation without pushing the engines harder and increasing bleed demand. Other options don’t directly address the bleed leak right away: they either don’t impact the bleed system promptly or could complicate the situation.

Landing gear position monitoring is provided by the Proximity Sensor System. It uses sensors placed on the gear to detect whether the gear is extended and locked or retracted, and this position data is sent to the cockpit indicators and gear warning logic. This direct sensing gives accurate, real-time status of the landing gear, which is essential for safe approach and takeoff. The cockpit clock has no role in detecting gear status. The left hydraulic system powers the gear actuators but does not provide the position signals needed for monitoring. The nosewheel steering controller handles steering input, not the gear’s position.