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Slick9

Crossing the threshold - what height?

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With all things being equal, what would you experienced NGX drivers say is the optimal height range to cross the threshold (a normal threshold, not an extended one) on short final? Does 80 - 100 feet sound ok?

 

Richard

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Well,, i´m not an expert, but out of my experiences i would say, if you cross the threshold at around 40-50 ft, you can do a nice flare and bring it down in the touchdownzonce pretty easy. 80-100 sounds a bit high for me... Would be okay at big airports with 12000ft runwaylength, but if the runway is only 6000ft long, i would prefer it to be lower :D

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50 they say (I think) or maybe I get confused with the height that you retard your throttles...

 

Let's see!

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On any ILS approach plate, it's published as "TCH" in the profile view and is indeed around 50 feet.

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Thanks for the answers, I didn't think of the runway length would that make a difference? I wouldn't think so though.

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If you were 50 feet above threshold well, you succeeded it. :)

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A three degree glideslope (which most ILSs are) will put you at 50 feet when crossing the threashold.

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The height is called Screen Height or TCH (Threshold crossing height) and is standard at 50FT execept published on the approach chart...

 

Cheers.

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With all things being equal, what would you experienced NGX drivers say is the optimal height range to cross the threshold (a normal threshold, not an extended one) on short final? Does 80 - 100 feet sound ok?

 

Richard

 

I'm also no expert, but I use 40ft for a nice soft touchdown!

Cheers

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In real life you calculate your landing distance from 50 ft above the threshold.

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A perfect landing is Vref(V threshold) and 50ft on the threshold (the piano) and touchdown on the aiming points(big marks at 1000ft), or at least in the TDZ (3000ft touchdown zone), that's standard.

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Not only standard, but since those marks identify the touchdown zone (TDZ), it's required for US air carrier ops by regulation (14 CFR 91.175 ©(1)) that the rate of descent below the DH/DA or MDA allow for touchdown within the TDZ.

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This might be a very theoretical aspect, but still. Do remember on a 3 deg slope every additional foot of height will put you 20 feet further down the runway (i. e. 50' too much, e. g. crossing at 100' on a short runway could lead to difficulties setting her down properly)... so I would suggest to aim for a 50' crossing at threshold which is considered standard under most circumstances if not stated otherwise.

 

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