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Aldarean

Read distance to any waypoint

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Hello,

 

is there any possibility to check the distance of any waypoint, for example when I want to calculate the correct sinkrate and TOD for my descent for my own. The only way I know is the ND shown distance but it Shows just the distance to the next waypoint. Only to set the range on the ND is not enough because the flightplan don't follow a straight route everytime.

 

Thanks and much thanks for the grate bus to the wohle development team.

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Hi, you can always use  PROG page and then type waypoint you need in BRG/DIST row. Regards.

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vor 18 Minuten, brtkstn sagte:

Hi, you can always use  PROG page and then type waypoint you need in BRG/DIST row. Regards.

Thank you, I will try this

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I'm not able to check it right now, but i think that solution will give you direct distance to that waypoint and not the track distance with all other points in your flight plan. Regards.

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On ‎06‎.‎11‎.‎2018 at 13:24, brtkstn sagte:

I'm not able to check it right now, but i think that solution will give you direct distance to that waypoint and not the track distance with all other points in your flight plan. Regards.

 

Yes, you are right. I've tried the PROG page and got the direct distance. Any other solutions? I mean, how does a pilot calculates his descent if he don't know the correct distance? I want a descent with 3° . Wich descent angle is calculated by the MCDU at the TOD?

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32 minutes ago, Aldarean said:

 

Yes, you are right. I've tried the PROG page and got the direct distance. Any other solutions? I mean, how does a pilot calculates his descent if he don't know the correct distance? I want a descent with 3° . Wich descent angle is calculated by the MCDU at the TOD?

 

The MCDU calculatest the angle resulting of the speed entered for descend using IDLE thrust, taking into account any restrictions in the F-PLN page.

If you want to calculate your descend manually make sure to use a sensible distance. Using the direct distance you get from the PROG page is not always the best idea.

 

What we do in my airline is to make modifications to the FPLN without executing/inserting them, that way the computer calculates predicted crossing altitudes. We then enter one of them as a hard altitude in the flightplan after erasing the temporary plan again.

This way we get a good usable VNAV path from the FMC while maintaining the whole arrival routing in case ATC needs us to fly the whole procedure.

While we descend down we periodically update those estimation based on new info from ATC, etc.

Example: Arrival at Hamburg for an ILS23 via the NOLGO23 transition. Assuming there is not a lot of traffic expected at the estimated time of arrival I would enter a direct from DH611 to PISAS and a speed of 185 at PISAS. This gives me about what I expect to get lateron from ATC.

The FMC will then predict new altitudes backwards on the arrival. Let's say it would predict NOLGO at FL80. I would then erase the modifications we have just done and afterwards enter NOLGA at FL080 which I then execute/insert.

Now the VNAV will bring us down "on profile" for the expected shortcut while we still have the whole transition in the box in case we do not get the shortcut.

 

This is just a general procedure which works at most airports and arrivals. Of course occasionally you will have to fly a longer track which means you'll use up some more fuel because you have been lower, but better you're too low than too high.

 

If you still want to calculate it in your head I use this way:

Altitude x 3 + 1NM for each 10kt IAS above 200 +/- 1NM per 10kt head/tailwind.

This gets you down quite well. But here again, make sure to calculate with some sensible info. If you're coming in from the wrong side and have to fly around the airport there's no sense using the direct distance from the PROG page (or the FIX INFO page) as you will fly at least another 25NM.

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Another way to do it is keep the distance the same and adjust the v/s based on winds.

 

(ALT to Lose /1000)* 3 = TOD

Ground Speed/2 + 0 = VS

 

So 30,000/1000 = 30 * 3 = 90 nm TOD

GS say 460 Knots / 2 = 230 + 0 = 2300 FPM

 

So lead it by 2 NM  @ 92 NM out start down at 2300 FPM and do checks every 5000' on your way down to ensure you're still on profile.

 

At 25000  ... 25 *3 = 75 NM out verify

at 20000  ... 20 * 3 =  60 NM out .etc.  if your high or low adjust.

 

remember your TAS goes down as you go down wind depending so you will have to divide your new GS in half and add a 0 to get the new VS to stay on 3 deg path.

 

very easy actually.

 

EDIT:  This doesn't account for deceleration at 10,000 or for approach and configuration only to keep you on a 3 deg slope.  Also you have to take into account Field elevation.  if you are 30K and field is at 5K you only have 25K to lose.

 

Also plan to be down at 10000 say 5 nm early so you cna slow to 250, so you will add that distance to your TOD and each altitude / dist check.

 

Complicated??? maybe initially but very easy after you get the hang of it.

 

 

 

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14 hours ago, Emanuel Hagen said:

Altitude x 3 + 1NM for each 10kt IAS above 200 +/- 1NM per 10kt head/tailwind.

 

Always works for me. This is a rule of thumb. 

 

Only, if there is headwind then you need to subtract miles, not add. Since you're in fact going slower than your indicated speed.

If there's tailwind, you add miles. In Emanuel's formula that may not be understand correctly.

 

Example:

ALT: You're at 35.000, final altitude before GS capture is 3.000. So you've 32.000 to lose. 32 x 3 = 96 MILES

SPD: IAS = 320 knots. So: 320 - 200 = 120. That means + 12 MILES

WND: Descent headwind component 30 knots. That means - 3 MILES

 

96 + 12 - 3 = 105 MILES (Track distance) to start your IDLE descent

 

 

Check this. They explained many things pretty good and easy to understand..

https://www.vatnz.net/pilots/pilot-guides/energy-management-descent/

 

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Thank you for your detailled reports. My calculations are looking like bill3810 said. But my main question is, where can I see the track distance between miy PPos and FAF when I want to calculate it by myself?

 

To take Emmanuels example with EDDH at STAR NOLGO23: At PISAS I have to be on or below 3000ft and my present Position is 80nm before NOLGO at FL 320 and my IAS 320knt/ GS 460 (to take ozgulkagans example). I want to descent with a 3° angle so that I am at 3000ft at PISAS.

 

FL320- FL030 = 290

290/3 = 97 nm

SPD: 320-200 = 120knt = + 12nm

WND: -3 nm (as in the previous post) = - 3nm

TOD = 97 + 12 - 3 = 106 nm before PISAS

V/S = 460/2 = 2.300 ft/min

 

Where is this TOD Point when I fly the complete Transition route?

 

Edit: Okay, it's stupid because you don't know where PPos is, but there must be a possibility to check out the track distance

 

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Just take the total distance which is in the last line of the FPLN page and subtract the distance of the approach procedure that is in the charts (or just add the milage by looking at the approach waypoints in the MCDU, and subtract that total milage) to get the distance to the FAP/FAF. 

 

 

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vor 38 Minuten, Frank Docter sagte:

Just take the total distance which is in the last line of the FPLN page and subtract the distance of the approach procedure that is in the charts (or just add the milage by looking at the approach waypoints in the MCDU, and subtract that total milage) to get the distance to the FAP/FAF. 

 

 

It could be so simple, yes :D. Thank you

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