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Driver170

VREF + 20 kts and landing flap placard speed help

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In the FCTM it says If VREF + 20 knots exceeds landing flap placard speed minus 5 knots, use landing  flap placard speed minus 5 knots.

 

Now if my vref is 139 kts and i had winds at  02016G18KT  and runway 03, i would add half the headwind (8 kts) plus the full gust (12 kts) = vref + 20 kts and i should bleed off the headwind and land with the full gust of 12 kts.

 

Now as the title says, if VREF + 20 knots exceeds landing flap placard speed minus 5 knots. so should i only add 15 kts? because vref 139 plus 20 is 159 kts and that has exceeded 20 kts. but i just don't get it, why do you minus 5 knots if you have more than 20 kts above your landing speed of 159. so what situation can you have when you can land with the full 20 kts and not minus 5.

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This is to prevent you overspeeding the flaps.

 

The placard speed is a hard limitation. I'm not entirely familiar with the NG, but a quick Google suggests the Flap 40 placard speed is 156kts.

 

Therefore, in your example, if you're landing with Flap 40, Vref40 is 139kts and you add 20kts (half steady headwind + gust), Vapp will be 159kts. This is in excess of the Flap 40 placard speed = bad news. Therefore, to protect the flaps you would use the lower speed of 151kts, which gives you a small margin in case you hit a gust, allow your speed to wander upwards slightly during the approach etc.

 

If you were lighter, and Vref40 was, say, 129kts (plucking figures out of the air -- as I say, I'm a Jumbo man) -- in the same conditions you could add 20kts to give a Vapp of 149kts. This is 7kts below the Flap 40 placard speed of 156kts, so there's sufficient margin to keep the flaps attached to the airframe.

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Now if my vref is 139 kts and i had winds at 02016G18KT and runway 03, i would add half the headwind (8 kts) plus the full gust (12 kts) = vref + 20 kts and i should bleed off the headwind and land with the full gust of 12 kts.

 

The gust factor is 6 knots, not 12.  Vapp would be 153 (139 + 8 +6).  Flap placard speed will not be an issue.

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Am I missing something here?

 

020 at 16 G 18. How are people getting 12? I get 2, which doesn't qualify for a "gust" (at least in FAA-land), as a gust must be a difference of 10 knots between steady state and max wind.

 

I'm guessing that there's a typo somewhere and it should be 020 at 06 G 18. In that case, it's 6/2 + 12 = 15.

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A gust of 2 is correct.  I misread it as 12G18.  I blame the red eye I just got in from.  :)


We do it the easy way.  VREF+5 no adjustments required if A/T used to touch down or the approach is flown using the HUD.  Keeps the math simple.

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Guys it was gusting to 28. My bad! I did retype it and must of put 18 by mistake.

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Am I missing something here?

 

020 at 16 G 18. How are people getting 12? I get 2, which doesn't qualify for a "gust" (at least in FAA-land), as a gust must be a difference of 10 knots between steady state and max wind.

 

I'm guessing that there's a typo somewhere and it should be 020 at 06 G 18. In that case, it's 6/2 + 12 = 15.

Kyle,

 

My neighbor has been a captain on the B737NG for over ten years. He normally uses auto-throttle/HUD for landing using Vref+5.

 

Not about the B737, but I have always used 1/2 of headwind component plus all the gust spread up to Vref+20. I would start to bleed off the headwind component crossing the fence (200 agl) with it gone by 50 agl.

 

Billy Bluestar

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My neighbor has been a captain on the B737NG for over ten years. He normally uses auto-throttle/HUD for landing using Vref+5.

 

This would mesh with what Boeing advises when using A/T.

 

 

 


Not about the B737, but I have always used 1/2 of headwind component plus all the gust spread up to Vref+20. I would start to bleed off the headwind component crossing the fence (200 agl) with it gone by 50 agl.

 

Yeah, that's why I had the formula in the post you quoted: 6/2 + 12 = 15 (steady/2 + gust = comp).

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Let's say -800 and flaps 30 the limit is 175. So your approach Max is 175-5 or 170.

 

Your Vref+additive cannot be more than 170.

 

F40 limit is 162 and your Vapp can't be more than 157.

 

Also, bleed off steady state but keep the gust factor to touchdown (if flying A/T off).

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This would mesh with what Boeing advises when using A/T.

 

Not necessarily.  Autothrottle to touchdown is what's taught by our training department.  The last time I was at the school house I asked about it and was told it came straight from Boeing.

 

With the A/T on it's VREF + 5, A/T off you have to adjust for steady wind and gusts.  The captain can always use VREF + 5 because he has the HUD on his side.  The only time I land with the A/T off is if it's deferred or an abnormal procedure calls for it to be off.

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Not necessarily.  Autothrottle to touchdown is what's taught by our training department.  The last time I was at the school house I asked about it and was told it came straight from Boeing.

 

With the A/T on it's VREF + 5, A/T off you have to adjust for steady wind and gusts.  The captain can always use VREF + 5 because he has the HUD on his side.  The only time I land with the A/T off is if it's deferred or an abnormal procedure calls for it to be off.

 

Are you being intentionally argumentative for some reason, or did you not understand that I literally just wrote the same thing?

 

Billy wrote he has a neighbor who uses VREF+5 with A/T on.

I agreed by saying that would mesh (sync, harmonize, agree) with what Boeing advises.

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Are you being intentionally argumentative for some reason, or did you not understand that I literally just wrote the same thing?

 

Disregard.  You clearly wrote "mesh" which my sleep deprived mind interpreted as "clash".  We are indeed on the same page.

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Disregard.  You clearly wrote "mesh" which my sleep deprived mind interpreted as "clash".  We are indeed on the same page.

 

haha - cool. Sorry for the earlier bluntness. Post day job post and that job always makes me super happy...  :Drooling:

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Do any of you NGX pilots bounce the AC during gusty weather? I can keep it coming down nicely, reduce the ROD about 20 ft and cut the throttles but somehow she keeps on bouncing. I don't know if its due to being too fast because of VAPP?

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Bounced landings are rare.  Once the spoilers come up the jet is going to stay on the ground.  Most of the bounces I have seen are the result of flaring late (or not at all) combined with too much speed.

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I don't know if its due to being too fast because of VAPP?

 

It's all down to landing technique. With gusty winds, you need to set the aircraft down firmly. The FCOM states that you should bleed off the wind additive (down to the gust correction) in the flare, touching down at the gust correction. It also adds that a smooth landing is not necessarily a safe one.

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I'm landing with my full gust of 11kts onto vref + 30 139kts so about 150 i'm flaring with at 20 feet. It seems to float slightly though on the bounce. Its not a hard bounce may i say ;) i do focus my view to the end of the runway. I'm searching everywhere for tips!

I'll keep on trying as i'm flying into LPMA rwy 05 visual :) one of the most extreme airports. Never a day when its not gusty lol

Got a few RW pilots helping me too :)

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Got a few RW pilots helping me too :)

 

The last two guys who answered here are RW pilots (though Joe actually flies the 73 and I don't), too.

 

As I've always said: just because it's from PPRuNe doesn't make it better.

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I'll keep on trying as i'm flying into LPMA rwy 05 visual :) one of the most extreme airports. Never a day when its not gusty lol

 

Perhaps try a less extreme airport while you are learning.  One step at a time.

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The last two guys who answered here are RW pilots (though Joe actually flies the 73 and I don't), too.

 

As I've always said: just because it's from PPRuNe doesn't make it better.

 

Do they fly into Madeira? I only asked on pprune for pilots help and got a good response. Infact i've learn't quite alot more about the AC :)

Perhaps try a less extreme airport while you are learning.  One step at a time.

 

I see myself doing the same old ILS app and wanted a challenge to boost my confidence in flying and getting to know how to handle her.

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Do they fly into Madeira? I only asked on pprune for pilots help and got a good response. Infact i've learn't quite alot more about the AC :)

 

You are asking for advice on landing technique.  The airplane doesn't care if it's landing in Madeira or Chicago.  

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Do they fly into Madeira? I only asked on pprune for pilots help and got a good response. Infact i've learn't quite alot more about the AC :)

 

Glad you got a good response. A landing is a landing is a landing, though...


EDIT: Joe beat me to it.

 

You are asking for advice on landing technique.  The airplane doesn't care if it's landing in Madeira or Chicago.  

 

Exactly.

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I just thought i would mention Madeira. This is the first time i've actually took control of this AC and flew manually and multitasking, but with the help with my FO :D

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