L1 - What is coastal effect? [ADF system]

Question

BlackTom AI · Accepted Answer

Question restatement: L1 - What is coastal effect? [ADF system]

Answer options:
1) ADF bearing information can only be received from in front of aircraft
2) Hard iron effects in aircraft result in ADF bearing errors
3) Errors introduced in the ADF signal because of p-static and electrical interference
4) Bending of the ADF signal when passing from land to water

Option 1 analysis: This statement claims ADF bearing information is only available from in front of the aircraft. In reality, an ADF system uses a loop antenna and senses a bearing to a non-directional beacon (NDB) from all directions around the aircraft. It is not limited to the front hemisphere. Therefore, this option is incorrect because it misstates how ADF bearing reception works.

Option 2 analysis: “Hard iron effects in aircraft result in ADF bearing errors.” While hard iron distortions can affect magnetic compasses by shifting the local field, ADF systems rely on RF reception and a loop antenna to determine bearing to the NDB. Although aircraft metal can influence radio signals in some ways, this statement more accurately describes compass errors or magnetometer effects, not the coastal effect. Thus, this option is incorrect in the context of coastal effect.

Option 3 analysis: “Errors introduced in the ADF signal because of p-static and electrical interference.” Precipitating p-static and general electrical interference can degrade radio navigation signals, but this describes broad RF noise/interference rather than the specific coastal effect phenomenon. Therefore, this option does not describe the coastal effect and is incorrect as the primary cause of coastal effect.

Option 4 analysis: “Bending of the ADF signal when passing from land to water.” This aligns with the recognized coastal effect: when the aircraft crosses the coastline, the contrast in conductivity and ground impedance between land and sea modifies the ADF signal path, causing the bearing indication to bend or deflect from its true line to the beacon. This option accurately captures the specific phenomenon described by coastal effect and is therefore correct.

Summary of reasoning across options: The first three statements describe general antenna reception, magnetic/iron-related errors, and RF interference—which are not the defined coastal effect. The fourth option explicitly identifies the characteristic coastal effect as the bending of the ADF signal at the land–water boundary, which matches standard aviation navigation explanations for this phenomenon.

25F --Aircraft Navigation Systems (SEC. 501) MIDTERM Exam ATAC506 W25 - Requires Respondus LockDown Browser 25F --Aircraft Navigation Systems (SEC. 501) MIDTERM Exam ATAC506 W25 - Requires Respondus LockDown Browser

L1 - What is coastal effect? [ADF system]

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