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Driver170

bleeding off vapp speed to vref +5 - PFPX

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Hi guys.

 

I'm running TOPCAT and PFPX together. i'm having trouble understanding the calculations PFPX has thrown at me, also do i bleed off the vapp SPEED before touch down but not below VREF + 5?  here goes...

 

 

** LANDING DATA EGPH 06 **
 
COND:    64635 KG // RWY DRY // +17°C  Q1012  110/08  // LMT: STRUCT
CONFIG:  FLAPS 30 // A/I OFF // A/C ON
SPEEDS:  VREF=148  VAPP=155
ENG OUT: AT 12 DME 'IVG' 108.9 RT TO 'EDN' 341.00 (230 INBD,RT)
 
now is that vapp correct? 155 knots and am i right in thinking i should bleed off that speed untill 153 knots? 148 + 5 

Vernon Howells

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It appears that it incorporated the wind data and used that to determine the correct VAPP. Maintain that speed until the flare. In a perfect world, you'd bleed off down to 148kts and touch down at that speed.

 

 

VREF+5 is really just a guide, not a rule for approaches. It can, and does, change depending on different variables such as wind.


Dave Wegner

 

- Don't be afraid of common sense or the search function.

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Hi kerlix so i will use the vapp speed PFPX / topcat provide for me? and bleed that off over the threshold to 148 kts?

 

is that VREF = 148 with + 5 added to it yeh?


Vernon Howells

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Examples - 

1. Vref 120kts, Runway 18, wind 180/10. Bug set at 125, touchdown at 125

2. Vref 120kts, Rwy 18, wind 180/20G30. Bug set at 140 (steady headwind = 20, 1/2 of 20 = 10. Gust = 10, so 10 + 10 = additive 20), touchdown at 130 (bleed off the steady headwind additive of 10kts & just carry the gust additive of 10kts to touchdown).


Vernon Howells

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also do i bleed off the vapp SPEED before touch down but not below VREF + 5?

 

According to 737 FCTM for landing without autothrottle, you maintain any gust correction to touchdown, but bleed off the headwind correction approaching touchdown (pg 1.18)


Michael Faia

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spin is that correct calculations that PFPX is giving me?

 

also correct me if am wrong, my app speed will be 155 knots and shortly before touchdown i should bleed off 2 knots, leaving me at 148 + 5 for touchdown?


Vernon Howells

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Since I don't know what your winds are, I can guess that you have a headwind component of 14 knots. There doesn't seem to be any gusts since they are a minimum of 10 knots over the steady state, IIRC.

 

So all of the steady state is bled off during the flare.


Matt Cee

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Winds -

 

** LANDING DATA EGPH 06 **

 

COND: 64635 KG // RWY DRY // +17°C Q1012 110/08 // LMT: STRUCT

CONFIG: FLAPS 30 // A/I OFF // A/C ON

SPEEDS: VREF=148 VAPP=155

ENG OUT: AT 12 DME 'IVG' 108.9 RT TO 'EDN' 341.00 (230 INBD,RT)


Vernon Howells

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If the winds are 110 at 8 and Vref is 148, then Vapp should just be 153.


Matt Cee

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Matt you missed something,

 

Runway heading 060

 

Wind direction 110

 

Its not a direct heading its at 110 degrees! 50% for DHW so it can't be half of 8kts?


Vernon Howells

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Matt you missed something,

 

Runway heading 060

 

Wind direction 110

 

Its not a direct heading its at 110 degrees! 50% for DHW so it can't be half of 8kts?

I didn't miss it. :) I just know that any wind of 10 or less, regardless of direction, is going to have a wind correction of 5.

Matt Cee

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Not sure why PFPX is off then?

 

I'll just stick with what it gives me lol

 

Another thing after i takeoff i get the flashing A on the MCP i'm i overspeed for something?

 

Gear is up!

 

Flaps 1

 

V2 153 + 20


Vernon Howells

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