When installing a DME antenna, it should be aligned with which part of the aircraft?

When installing a DME antenna, it should be aligned with which part of the aircraft?

• A. Nose cone
• B. Center of the aircraft
• C. Left wing tip
• D. Right engine nacelle

Answer: (B)

Placing the DME antenna on the centerline of the aircraft is best because the antenna needs a clear, symmetrical path for its signal with minimal obstruction from the aircraft’s structure. The DME system operates in the UHF band and relies on reliable line-of-sight to ground stations. When the antenna is centered, it stays clear of major metalwork and aerodynamic surfaces like wings and engine nacelles, reducing shadowing, detuning, and multipath reflections that can distort the radiation pattern. This helps ensure consistent performance across different attitudes and flight conditions, which improves reliability of the DME readings. Placing the antenna at the nose cone could place it on or near the radome, where materials and shape can affect signal transmission and introduce reflections or attenuation. A wing tip location would place the antenna away from the fuselage’s symmetry, making the pattern more uneven and susceptible to interference from wing structures. A position near an engine nacelle would be close to large metal surfaces that can detune the antenna and worsen performance. Centering the antenna along the aircraft’s centerline minimizes these issues and provides the most uniform, dependable performance.

Placing the DME antenna on the centerline of the aircraft is best because the antenna needs a clear, symmetrical path for its signal with minimal obstruction from the aircraft’s structure. The DME system operates in the UHF band and relies on reliable line-of-sight to ground stations. When the antenna is centered, it stays clear of major metalwork and aerodynamic surfaces like wings and engine nacelles, reducing shadowing, detuning, and multipath reflections that can distort the radiation pattern. This helps ensure consistent performance across different attitudes and flight conditions, which improves reliability of the DME readings.

Placing the antenna at the nose cone could place it on or near the radome, where materials and shape can affect signal transmission and introduce reflections or attenuation. A wing tip location would place the antenna away from the fuselage’s symmetry, making the pattern more uneven and susceptible to interference from wing structures. A position near an engine nacelle would be close to large metal surfaces that can detune the antenna and worsen performance. Centering the antenna along the aircraft’s centerline minimizes these issues and provides the most uniform, dependable performance.