For an ILS approach, what altitude should be set in the MCP when using VNAV to meet altitude constraints prior to the published FAF?

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Multiple Choice

For an ILS approach, what altitude should be set in the MCP when using VNAV to meet altitude constraints prior to the published FAF?

When using VNAV on an ILS with altitude constraints, you set the MCP to the altitude published for the Final Approach Fix on a precision approach. Crossing the FAF at that specified altitude ensures the vertical profile up to the start of the final approach segment adheres to the published constraints, allowing VNAV to manage descent properly and then hand off to the precision guidance (glideslope) after the FAF. Why this fits best: the FAF altitude is the official constraint for the final approach segment on a precision approach. Setting the MCP to that altitude prevents descending too early and guarantees you meet the required crossing height before the final approach begins, which is essential for all subsequent steps and for a clean transition to the glideslope. Why the other options aren’t correct: the DA/DDA/MDA figures apply to decision or minimums for non-precision or other procedures, not to the pre-FAF VNAV constraint on a precision approach. The minimum crossing altitude is a specific crossing height for a particular fix, not the general FAF altitude used to constrain the VNAV profile before the FAF. A fixed value like 2000 ft isn’t appropriate because the FAF altitude varies by approach plate and must be taken from the published procedure.

When using VNAV on an ILS with altitude constraints, you set the MCP to the altitude published for the Final Approach Fix on a precision approach. Crossing the FAF at that specified altitude ensures the vertical profile up to the start of the final approach segment adheres to the published constraints, allowing VNAV to manage descent properly and then hand off to the precision guidance (glideslope) after the FAF.

Why this fits best: the FAF altitude is the official constraint for the final approach segment on a precision approach. Setting the MCP to that altitude prevents descending too early and guarantees you meet the required crossing height before the final approach begins, which is essential for all subsequent steps and for a clean transition to the glideslope.

Why the other options aren’t correct: the DA/DDA/MDA figures apply to decision or minimums for non-precision or other procedures, not to the pre-FAF VNAV constraint on a precision approach. The minimum crossing altitude is a specific crossing height for a particular fix, not the general FAF altitude used to constrain the VNAV profile before the FAF. A fixed value like 2000 ft isn’t appropriate because the FAF altitude varies by approach plate and must be taken from the published procedure.

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