500 ft above airfield elevation in VMC.

Aircraft Deceleration Characteristics

Although deceleration characteristics largely depends on the aircraft type and gross-weight, the following typical values can be considered for a quick assessment and management of the aircraft deceleration capability:
Deceleration in level flight:

With approach flaps extended: 10 to 15 kt-per-nm;

With landing gear down and flaps full: 20 to 30 kt-per-nm;

Deceleration on a 3 degree glide path:

With landing flaps and gear down: 10 to 20 kt per nm.

Note: Unstable  Unstable  V APP -10 kt  /  IdleV APP -10 kt  /  Idle
A 3 degree glide path is typically equivalent to a descent-gradient of 300 ft-per-nm or a 700 ft/mn vertical speed, for a final approach ground speed of 140 kt.
 
Decelerating on a 3 degree glide path in clean configuration usually is not possible. 
When established on a typical 3 degree glide slope path with only slats extended (i.e., with no flaps), it takes approximately 3 nm (1000 ft) to decelerate down to the target final approach speed and to establish the landing configuration.
Speedbrakes may be used to achieve a faster deceleration, as allowed by the aircraft type (i.e. speedbrakes inhibition).
Usually the use of speedbrakes is not recommended when below 1000 ft above airfield elevation and/or in the landing flaps configuration.
Typically, slats should be extended not later than 3 nm before the FAF.
Figure 1 illustrates the aircraft deceleration capability and the maximum possible speed at the OM, based on a conservative deceleration rate of 10 kt per nm on a 3 degree glide path.
The following conditions are considered:
IMC (stabilization height 1000 ft above airfield elevation); and,

Final approach speed (VAPP) = 130 kt.

The maximum deceleration achievable between the OM (typically 6.0 nm from the runway threshold) and the stabilization point (1000 ft above airfield elevation / 3.0 nm) is: 10 kt-per-nm  x (6.0 – 3. 0) nm = 30 kt.
　
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