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Coopz67
21st Jun 2010, 10:04
Hello all, I'd like to know your thoughts on the following.
A wind calm, ILS approach.
Although there probably are lots of different variables and it will differ between SOPs of airlines, Id like to know the most common or safest landing procedure.

1. Vref+15 until when/height ?
2. Throttle Idle when/height ?
3. Flare height ?
4. Autothrust engaged or disengaged ?
5. Autopilot disengage height

I am simming on Wilco Airbus 320 series 1 and I am crunching the landing 400ft per min and speed is too high so any help you can post in order I can grease it a bit more and get the speed off better would be greatly appreciated.

Thanks
Coopz

potkettleblack
21st Jun 2010, 13:16
Taken from the Airbus A320 FCTM (Flight Crew Training Manual)..."

When reaching 50 ft, the auto-trim ceases and the pitch law is modified to flare
law. Indeed, the normal pitch law, which provides trajectory stability is not the
best adapted for the flare manoeuvre. The system memorizes the attitude at 50
ft and that attitude becomes the initial reference for pitch attitude control. As the
aircraft descend through 30 ft, the system begins to reduce the pitch attitude at
a predetermined rate of 2° down in 8 seconds. Consequently, as the speed
reduces, the pilot will have to move the stick rearwards to maintain a constant
path. The flare technique is thus very conventional. Start the flare by
progressively increasing and holding the backpressure on the side stick. From
stabilized conditions, the flare height is about 30 ft. This height varies with
different parameters, such as weight, rate of descent, wind variations...
The roll is a roll rate law until the aircraft is on the ground.
At 20 ft, the "RETARD" auto call-out reminds the pilot to retard thrust levers. It is
a reminder rather than an order. The pilot will retard the thrust levers when best
adapted e.g. if high and fast on the final path the pilot will retard earlier.
In order to assess the rate of descent in the flare, and the aircraft position
relative to the ground, look well ahead of the aircraft. The typical pitch increment
in the flare is approximately 4°, which leads to -1° flight path angle associated
with a 10 kt speed decay in the manoeuvre. A prolonged float will increase both
the landing distance and the risk of tail strike.

So that is what the book says. As you can see when to take power on/off will depend on the day and can be influenced by factors such as weather conditions. Often I have been over the threshold of a runway nicely stabilised and then had a shear and literally fallen from the sky necessitating in a solid dose of thrust to arrest the sudden rate of descent. Sometimes this thrust might have to be kept on below 20ft with the aircraft calling retard, retard. It all depends....

As to whether the automatics are in or out it will all depend on your company SOP's and personal preference. I prefer to use manual thrust and will disengage the auto pilot early in the approach to keep my hand in. Other companys require AT to be left in. If there is the potential for a go around due to traffic being slow to line up or depart then I might keep the automatics in later than usual to make my life easier. Again it all depends.

The AP can be disconnected as late as 80ft assuming Cat3 DUAL is showing on the FMA.