Inst App - Speed Reduction BLW Init. Seg. Spd.

[FRQ Charlie Bravo]

Below the table "Speeds for Procedure in Knots IAS" AIP Enr 1.15.1 Jepp AU-16 2.3.1 is note 2 which states that "Speed reduction below the initial segment speed range is permitted to enable the final approach speed to be achieved prior to the commencement of the final segment."

Now as far as I can see every minimum initial speed for each category (A - E and H) is already below or equal to the corresponding maximum speed. What purpose then does this exception serve? What am I missing? Do any of you utilize this in practice? All I can think of is perhaps Cats C and D having a bit of latitude to dip below 160 / 180 as it is otherwise the ONLY permissible speed at which they may cross the FAF.

Thanks in advance,

FRQ CB


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[travelator]

It is to facilitate a continual speed reduction/configuration to the final approach speed Vapp without having to hold speed which may not agree with the phase of flight. Depending in the aircraft, this may mean you need to hold the configuration at a point that to achieve the minimum initial speed until crossing the FAF resulting in a more compressed sequence of events and less time stabilize the aircraft and approach after the FAF.

My interpretation and happy to be proved otherwise.

[FRQ Charlie Bravo]

Yes, that does make sense. I think that what hadn't occurred to me was the benefit of permitting a bit of a margin for error in the stable slowing down of the aircraft.

In the case of Cat C for example (Min Initial/Intermediate segment and Max Final Segment speeds are 160 and 160). If the crew are aiming to be at the FAF (or FAP) AT 160 KIAS then without the relief provided by note 2 they would most likely need to achieve 160 knots before the fix (or point for Precision Approach) and then hold the speed. Obviously the safer option is to continue to slow down at the same rate having achieved 160 KIAS at or before.

Thanks Trav.

FRQ CB

PS Although this might look like a self-fulfilling thread I really am looking for feedback, especially if I am wrong.

[Stiff Under Carriage]

You might have a flap restriction below 160kts. Thus to be configured by the FAF a speed reduction below the lowest Initial segment speed is required to achieve the final flap extension.

A reverse sense of what travelator is saying.