With a 15 knot headwind while flying the ILS Rwy 9, which is the expected power setting for a rate of descent of 90 knots?

When flying an Instrument Landing System (ILS) approach, particularly with a headwind component, it's essential to compute the necessary rate of descent to maintain the proper glide slope and airspeed. The wind affects the ground speed, and since a headwind decreases ground speed, your required rate of descent must account for this.

At a typical approach speed of 90 knots in a configuration suited for landing, with a 15-knot headwind, the need to maintain the correct descent profile necessitates a slightly higher power setting for descent. The standard calculation for a descent rate on approach can be derived from the formula:

Rate of descent (in feet per minute) = (Ground speed in knots x 10) + 1/2 the altitude in thousands of feet.

Assuming you are at an altitude directly above the runway, this can lead to an expected result. With 90 knots indicated airspeed, applying the headwind adjustment, results in a required descent profile that aligns well with the choice indicating 398 feet per minute.

This choice considers both the wind impact and typical descent rates needed for a stable approach on an ILS. Hence, the calculations and adjustments for maintaining the glide path correctly substantiate the choice of 398 feet per