160 to 4 - deceleration rate (again)

[FlightDetent]

Hello, to clarify a discussion with a new colleague: How quickly do you need us to decelerate from 180 to 160 knots on final approach?

I like to keep 180 until instructed to reduce, and if that comes after GS intercept, say at 7,5 NM, then the flaps/gear sequence provided in the Pilot's Handbook for decelerated approaches would only yield 160 kt by 5 NM.

Those 50 seconds do not feel like doing what was asked for. Hence a different flap/gear sequence needs to be adopted, that would be my point.

Looking for facts to support my case, thanks.

[DaveReidUK]

Originally Posted by FlightDetent

As long as I refuse to decelerate until instructed to do so, to make it 160 to 4 instead 160 by 4, a different sequence to dirty-down needs to be adopted.

Isn't it more a case of being instructed not to decelerate (i.e. "maintain 160 to 4"), rather than not being instructed to decelerate ?

[HEATHROW DIRECTOR]

At the point the instruction is given the aircraft should still be at 180kts and ATC would expect a fairly rapid reduction to 160, especially if 2.5nm spacing is in force.

[wiggy]

How quickly do you need us to decelerate from 180 to 160 knots once instructed on the final approach?

For some reason I've had heard a knot per second being the ATC requirement/expectation for deceleration but no idea if it's an official figure laid down in the manuals.

[DaveReidUK]

Originally Posted by FlightDetent

How quickly do you need us to decelerate from 180 to 160 knots once instructed on the final approach?

The reason I ask is that our aircraft manufacturer's recommendation on decelerated approaches would only yield 160 kt by 4 NM, if starting to slow down at 7,5 NM.

That's a speed loss of about 0.3 kts per second.

[Crazy Voyager]

There is to my knowledge nothing laid down but after talking to various crews one knot per second seems common and I think that matches what controllers would expect.

[ZOOKER]

wiggy,
That figure sounds familiar, but I can't remember where I read it.

[FlightDetent]

I rewrote the original post as it was assembled in a confusing manner.

"... would expect a fairly rapid reduction" has all the emphasis I need.
"1 kt/s" translates to about 0,8 miles, same goal.

Thanks all, happy to see HD still watching over us.