FAA Instrument Flight Instructor (FII)IFR Procedures and ApproachesMedium
An aircraft is executing a published missed approach procedure that specifies a climb gradient of 260 feet per nautical mile to 4,000 feet MSL. During the climb, the aircraft's groundspeed is 120 knots. What minimum rate of climb, in feet per minute, must the pilot maintain to comply with the published gradient?
- A260 feet per minute
- B650 feet per minute
- C390 feet per minute
- D520 feet per minute
Show answer & explanationAnswer & explanation
Correct answer: D. 520 feet per minute
Convert groundspeed to nautical miles per minute: 120 kt ÷ 60 = 2 NM/min. Multiply by the required gradient: 260 ft/NM × 2 NM/min = 520 ft/min. This is the minimum climb rate needed to satisfy the obstacle-clearance gradient at that groundspeed.
Why the other options are wrong
- A. This is the ft/NM value, not converted for groundspeed.
- B. Overstates the required rate; not supported by the given groundspeed.
- C. Reflects an incorrect groundspeed conversion (90 kt), not 120 kt.
Climb Gradient to Rate Conversion
Published climb gradients (ft/NM) must be converted to a required climb rate (fpm) based on groundspeed to ensure obstacle clearance during a missed approach or departure.
- Formula: Rate (fpm) = Gradient (ft/NM) × Groundspeed (kt) ÷ 60
- Higher groundspeed requires a higher climb rate for the same gradient
- Charts often provide gradient tables cross-referenced with groundspeed
Memory trick: 'Gradient times Ground, divided by Sixty' gives Growth rate.