To avoid false or premature glideslope capture, what sequencing is recommended when preparing for a LOC-based approach?

• A. VOR/LOC may be selected initially, followed by APP once established.
• B. APP first, then LOC.
• C. Disable autopilots until LOC intercept.
• D. Arm both autopilots before any LOC actions.

Answer: (D)

To avoid false or premature glideslope capture on a LOC-based approach, you want the autopilot system ready to fly the localizer guidance before you begin intercepting the localizer. Arming both autopilots before any LOC actions ensures that both channels are prepared to engage the lateral guidance and participate in the approach sequencing as soon as you intercept the localizer. This coordinated readiness helps prevent the autopilot from reacting to stray or unintended vertical signals and reduces the chance of an accidental glideslope capture when you’re still configuring the approach.

If you delay arming one of the autopilots or try to start LOC actions without both channels ready, you increase the risk of unstable capture or an unintended vertical mode activating prematurely. Selecting the approach mode or enabling vertical guidance at the wrong time can lead to a false glideslope trigger or an abrupt change in flight path. By having both autopilots armed beforehand, you establish stable, predictable control as the LOC is captured and the approach is sequenced.