Q for LHR ATC

[keendog]

I am lucky enough to live 10 Statute miles East of the the mid-point between 27L and 27R(I think, just North of Putney Bridge), and so have a nice view of the big birds coming in. It's probably me but heights and positions seem to vary at that point. Are all A/c established on the ILS by this time or are some still lining up?

[Trinity 09L]

The same reply for me at the opposite end at Windsor, even better, directly under the path watching the crab/sideslip and any other method used.

[Warped Factor]

The length of final depends mainly on how busy it is and can be anywhere from 8nm to 20nm. The ideal point to be hitting the ILS is around 12-15nm out.

So the answer to your question keendog, is yes :)

Some of the ones you see will be established on the ILS, others might still be on a closing heading and so slightly north or south of the centreline. If you're around 10 miles out they should all be around 3,000ft up, give or take a few hundred feet.

Trinity, same principles apply at the other end.

WF.

[???pax]

As additional query on this theme...

If aircraft are generally becoming fully established at around the 10NM/3000ft point, when would be the best time to drop the wheels (undercarriage)??

If an a/c is happily established at 10 DME and the pilot drops the wheels further on down the approach, will this cause the a/c to deviate from the glide slope?? Or is it the case that the undercarriage is lowered at or around the time when the glide slope is captured??

[flaps]

Dropping the gear varies.

If we manage our own approach profile (rarely at LHR) we'd be Flap 1 Gear Up at 10 miles. Around 5 miles with approx 2000 ft to descend we would take Flap2 and Gear Down, begin to decelerate and take the remaining Flaps so as to be fully configured and at final approach speed by 1000 ft.

If however we are coming in high and fast we may need the extra drag from the gear, I've even had to drop the gear at 10,000ft coming into LHR as we were held high for quite a long time and had to go down quite steeply. A tail wind might also be another reason for lowering the gear early.

At LHR you are often asked to maintain 160kts to 4 miles. I think? that to do this some of the 737's require a certain flap selection which unless the gear is down results in a loud horn sounding, quite off putting).

So in reality, whilst we would all like to drop the landing gear at a similar place, weather, spacing from the a/c in front or behind, ATC and other factors affect this.

Lowering the gear produces a pitch change and adds extra drag. The pitch change is easily countered by the autopilot or human pilot. The extra drag may require a bit more power but we try to do this in conjunction with slowing down.
Hope this helps.




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Stop waggling the stick!

[???pax]

flaps...

cheers for the info.