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tecboy99

A/T During Flare

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Question, It seems like if I leave the A/T on for landing, The throttles retard at around 15 feet. Causing a floating effect. I thought the real aircraft brings the throttles to idle at 25-ish feet. Is this a bug, or am I doing something wrong?

 

 

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Have you set the correct approach speed in the FMC and is this speed selected and active on the MCP?
 

Looks a bit like you're landing too fast. FMC speed from the LEGS page active (170 kts), maybe?

Edited by olli4740

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It's more likely that your flare is too steep. Common mistake.

 

Its always 4-5 deg. Maybe I should be a little more gentle? 

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I've been flying VREF + 5. Generally around 140 ish knots.

 

 

For a test, see what happens during an autoland in clear weather: Do your throttles retard the moment you expect them to do?

 

If yes, I concur with James. Likely something related to your landing technique. Like not being fully stabilized or starting to chase the G/S just before crossing the threshold.

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I thought the real aircraft brings the throttles to idle at 25-ish feet. Is this a bug, or am I doing something wrong?

 

The manual states that A/T will begin the flare between 25-50' radio altitude.  Closing the throttles is a relatively slow process, though.  Cutting the throttle too quickly could result in a hard landing.

 

Edit:

I'm with the rest of the guys here, though.  My bet is that it's probably technique.

Edited by scandinavian13

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For a test, see what happens during an autoland in clear weather: Do your throttles retard the moment you expect them to do?

 

If yes, I concur with James. Likely something related to your landing technique. Like not being fully stabilized or starting to chase the G/S just before crossing the threshold.

 

I do tend to chase the G/S. Maybe I'll turn off the F/D so I'm not so tempted ^_^ . I'll do some patterns tonight and let you guys know what I find out. Thanks!

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I do tend to chase the G/S. Maybe I'll turn off the F/D so I'm not so tempted ^_^ . I'll do some patterns tonight and let you guys know what I find out. Thanks!

 

Don't turn off the flight director, you'll want it on should you need to activate G/A. Just ignore it once you're closing in on the threshold as the ILS "cone" becomes too small to actually follow at this point. Your loc and G/S readings will be way too sensitive below around 100ft AGL (roughly).

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Don't turn off the flight director, you'll want it on should you need to activate G/A. Just ignore it once you're closing in on the threshold as the ILS "cone" becomes too small to actually follow at this point. Your loc and G/S readings will be way too sensitive below around 100ft AGL (roughly).

 

Will do!

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I override and cut the throttles at 20ft (F1 shortcut) - done a lot in the real world too. They do retard to idle pretty slow at times coming from a high approach N1. 

 

Remember that the 77L lands a bit faster than it should when you're around 215t and below with Flap 30 due to the 137 knot restriction on the GE90-110/5B engine. I use Flap 25 a lot now which averages 145 knots with wind correction and flies a bit better. When Flap 25 is 140 knots and below- I wouldn't bother using Flap 30 if the LDA is acceptable and not an autoland. 

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A bit off topic with the 137kt restriction. I notice that when landing at higher elevation airports (usually the ones above 4000ft msl) the vref for flaps 30 does indeed go below 137, I've seen it go to 135. just wondering why?

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There are two switches just aft of the power levers, if you flick both of these to OFF it does wonders for your return to earth. Start the APU before hand however.

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A bit off topic with the 137kt restriction. I notice that when landing at higher elevation airports (usually the ones above 4000ft msl) the vref for flaps 30 does indeed go below 137, I've seen it go to 135. just wondering why?

Your TAS will be higher even though your IAS reads 135kts. Since the 137kt Vref floor is based on Vmca (I assume at ISA) the FMC probably factors for the conditions at a high altitude airport.

 

Regards

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Question, It seems like if I leave the A/T on for landing, The throttles retard at around 15 feet. Causing a floating effect. I thought the real aircraft brings the throttles to idle at 25-ish feet. Is this a bug, or am I doing something wrong?

 

 

PMDG did say they were adding the capability to override the throttles for the flare. Should make it nice and easy. 

 

However... I've just looked in the issue tracking thread and any mention of it seems to have now been removed.

 

Must admit I've found the same re the flare. Autothrust "begins" to power back at 15 feet. Don't think it's related to spool down time.

 

In any case, all will no doubt change in SP1.

Edited by martin-w

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