Wheels down timing

[Philip Argy]

Why is there such a variety of timings for lowering the undercarriage on landing aircraft? Using 16R for example, I've noticed that even for identical a/c types, some pilots lower the undercarriage as far north as North Ryde whilst some wait until Leichhardt.

Is the timing used to modify air speed on approach? Is there any rule about how far out the undercarriage has to be down and locked?

[Will T]

Philip,

The normal ILS procedure for the 747-400 (and I presume a number of Boeing types) directs for Gear Down when the glideslope pointer begins to 'float' (starts moving downwards) on the pilot's nav display, with final landing flap selection on glideslope intercept (usually around 3000ft AGL, depending on the vector given). This makes for a slow and noisy approach, however, and is only used in inclement weather, or when there's a requirement to configure early.

99% of the time, a 'Noise Abatement Approach' ILS procedure is flown, in which Gear Down occurs at 2000ft AGL, followed by landing flap selection. In the case of 16R, this should occur 6.2nm from the threshold (you can use Google Earth to see where this is exactly). However, there are often directions from the radar controller to maintain a certain speed (eg 160kts) until x miles out, in which case the selection of gear might be delayed beyond 2000ft. Similarly, a direction to reduce speed earlier than usual would trigger the taking of gear and landing flap earlier than usual. As such, the point over the ground at which gear down occurs is fairly variable. As you mentioned, the gear is also remarkably good at fixing an approach that becomes a little 'hot', and might be taken earlier for that reason :)

Depending on the operator, the approach should be 'stable' (and in the full landing configuration) by 1000ft AGL.

Hope this helps.

Will

Ps. The normal 3 degree glidepath is approx. 330' per nm, so divide the above heights by 330 to see roughly how many miles from the threshold they are.

[Chris Tully]

Some world-wide operators select gear down at the outer marker location.

[Adam P.]

Is there any rule about how far out the undercarriage has to be down and locked?


Sometime before you reach the ground, one would hope!! :)

[Hugh Jarse]

Obviously your company doesn't have a Stable Approach policy, Adam. :)

Just about every airline, well, those with a High Capacity AOC do.

[Mick F]

For my operator (regional turbo-prop), abeam the landing threshold in a circuit, 5nm's on a straight in approach, or half a dot high approaching "On Slope" on an ILS.

Mick

[Alex G]

GA piston fun..

During IFR i did:
ILS - when GS is captured.
Runway-aligned approaches - over the aid on the outbound leg. If joining from an arc, when the arc is joined.
Non Runway-aligned approaches - Visual in the circling area.

VFR, downwind!


But when you dont have retractable, life is a lot easier :D

[Mick F]

It's also a lot slower too isn't it?? ;)

[Alex G]

Yeah...
but you get to look at the view in better detail!

[Adam P.]

Obviously your company doesn't have a Stable Approach policy, Adam.

Mehh, I wouldn't know - as long as they come back when we send them out (preferably having landed at their destination in the meantime :eek:) I'm happy!

[Alex G]

... (preferably having landed at their destination in the meantime :eek:)...

Hopefully with the wheels down !!!! :p:p