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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 

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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.

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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?

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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).

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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)

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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?

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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.

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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)

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

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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?

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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.

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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

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Flashing A actually means that you have set MCP speed below minimum.

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Well it was set at V2 153 per the FMC?

 

What amount of flaps was that V2 calculated with?  Were you following the speed/flap profile on the PFD?

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Flaps 1

 

V2 153

 

I was following the FD, maintaing V2 + 20

 

Engaged LNAV at 400

 

Engaged CMD A at 1500 thrust reduction height

 

Engaged VNAV at 3000

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i should say a flahing A

 

its happening at 1500 thrust reduction height?

 

i was flaps 1 

 

62.1 t

 

it just goes into LVL CHG after i select CMD A i don't select VNAV till flaps are up.

 

I was following the FD, maintaing V2 + 20

Engaged LNAV at 400

Engaged CMD A at 1500 thrust reduction height

Engaged VNAV at 3000 


soon as i bug up speed to 230 it stops flashing?


oh sorry yes NAD 1

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How about you try it with VNAV from the start.

 

The speed tape is bothering me, too. It doesn't seem right - like you're too heavy.

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soon as i roll the speed bug up, it goes away !

 

well i'm trying to follow a policy engage VNAV above 3000 agl ....

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Still get that flashing A on takeoff without VNAV engaged. The flashing A comes on about 1500 feet thrust reduction height!

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I didn't watch the whole thing, but something about his bugged speed and/or AP settings seems off. In fact, his A/T isn't armed during takeoff. I don't own the 737-series AOA lessons so I'm not sure why.

 

But if you look closely, his speed bug is slightly inside the "stall warning/stall imminent" zone on the speed tape. That's why he's getting the flashing "A" on the MCP.

 

I may be wrong, but I'm pretty sure that if that's happening, then it's a configuration issue on your end. Now, that may be done on purpose (Although I don't know why someone would do that) or it may just be an error/oversight.

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