# What is the flap extension schedule on approach for an airliner?

I understand that there are probably no set altitudes and speeds for flaps extensions, but can someone with insight provide a general guide for speeds, altitude and flaps for an ILS approach in good weather for a Boeing 777-300ER with a landing of Flaps 25 and $V_{ref}$ of 147 knots.

Something like this:

Alt: 5000 ft - Speed: 210 kts - Flaps 1
Alt: 4000 ft - Speed: 190 kts - Flaps 5...


(Boeing 777 manual.)

Substitute altitudes with position to runway. Near an airport an airliner usually flies at around 200 KIAS, this is when you select flaps 1.

Subsequent flap settings are also combined with selecting a lower speed as shown above. The speed tape makes it easy. Flaps 5 should be down by the final intercept path to the localizer or before turning base. Flaps 20 when established on the localizer. Then comes gear down and flaps 30 before the glide-slope is captured.

Initially you wrote PMDG, I recommend check their manuals, they are usually very informative.

For normal procedures on a Boeing 737, the flap settings 2, 10, and 25 are usually also skipped. So it's 1, 5, 15, and 30/40. Non-normal procedures differ.

On most Boeing twinjets (don't know about 747), the flap manoeuvre speeds can be derived or at least estimated with reasonably good precision by adding increments of 20 knots to VREF for the highest landing flap, e.g. to VREF30 for the 777. Minimum clean speed on these aircraft is typically around VREF30+80. The approach speed schedule recommends to extend each flap as you decelerate through manoeuvre speed (up to typically plus 20 knots). This means e.g. on a 777:

Deceleration through - select:

VREF+80 - F1

VREF+60 - F5

VREF+40 - F15 or 20 (15 can be skipped)

VREF+20 - Land flap (25 or 30)

Health warning: This is all from memory. If nobody else can chip in before Monday, I'll try to find quotable sources.

Best wishes, M