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captain420

Need help with takeoff values for Aerosoft Airbus using PFPX

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When configuring the MCDU, where can I get the takeoff values for the following entries? I am using PFPX. I know you can use the aerosoft utility to get those values. But I prefer to get it from PFPX. I don't want to use multiple apps just to get this information.

 

FLAPS/THS and FLEX TO TEMP

 

T%253AO+Offset.png

 

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Hi, forgive me if I am stating the obvious that you already know.

 

I use PFPX and transfer all the figures to the Aerosoft load manager and then on to the simulation, which inputs the parameters correctly into the FMS. The FMS is then designed to compute the engine take off power.

 

FLAPS/THS is usually 2 with trim up, automatically computed by the FMS. 3 would be for a short runway take off. The trim is always calculated by the FMC based on Take take Off Mass, Winds and temperatures.

 

As with the "TO Shift" that's highlighted. That figure (in meters) is usually only entered if the take off runway is shortened due to maintenance. Altering that (by inputting a shorter runway length) would force the FMS to compute for a shorter take off with higher power ratings. This is similar to the Flex to Temp, which gives amended power settings for inputted temperatures. Which is again computed by the FMS.

 

So for whatever initial weights, temperatures, winds and runway lengths you input, the FMS will give you the correct power outputs from the engines.

 

The Aerosoft Bus appears to simulate these power settings very well for different conditions, so the code they are using is well researched, insofar as our ESO coded simulation will allow.

 

Still a great sim aircraft though and a joy to fly:-)

 

Regards

 

David

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As with the "TO Shift" that's highlighted. That figure (in meters) is usually only entered if the take off runway is shortened due to maintenance. Altering that (by inputting a shorter runway length) would force the FMS to compute for a shorter take off with higher power ratings. This is similar to the Flex to Temp, which gives amended power settings for inputted temperatures. Which is again computed by the FMS.

 

Or, to say it in other words, you have to take that figure from that airport plate, PFPX does not supply it.

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You mean the SID chart? Where exactly is that information located on the chart/plate?

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In P3D runways are never shortened due to maintenance so you don't have to enter anything there ever. Although you COULD do so to simulate maintenance but in that case you can enter anything you want (though you might want to keep the number realistic).

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As with the "TO Shift" that's highlighted. That figure (in meters) is usually only entered if the take off runway is shortened due to maintenance. Altering that (by inputting a shorter runway length) would force the FMS to compute for a shorter take off with higher power ratings. This is similar to the Flex to Temp, which gives amended power settings for inputted temperatures. Which is again computed by the FMS.

TO Shift is usually used when taking off from an intersection. When you apply FLEX or TOGA power at the end of the runway it updates the aircraft position (last time it really 'knows' where it is), so this field just makes it more accurate. Obviously, these days, most Airbus's have GPS so it's not that important any more but that's why it's there. I suppose it does also act as a reminder to the crew when they calculate/enter the performance data where that data is valid from.

 

Also, in the real aircraft, the FMGC doesn't 'calculate' anything, you have to sort out your own performance figures and enter them all in. It doesn't contain any take off performance data, any calculations the AS Airbus does is just to make life easier for simmers who generally don't have access to a worldwide performance manual or a TOPCATesque program for the aircraft.

 

Hope this helps,

 

Ian

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excerpt from the Thales (MCDU) manual:

 

"Take-off shift: If published full runway length will not be used for take-off, enter distance between threshold and start of take-off in units specified, [M] or [FT]"

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Also, in the real aircraft, the FMGC doesn't 'calculate' anything, you have to sort out your own performance figures and enter them all in. It doesn't contain any take off performance data, any calculations the AS Airbus does is just to make life easier for simmers who generally don't have access to a worldwide performance manual or a TOPCATesque program for the aircraft.

 

So we can enter a maximum take off weight, low flex temp and the FMS will provide the correct power to the autothrottle? A good percentage higher than a minimum take off weight at high flex temp? That's the Airbus FMS as opposed to a Boeing one....once the power levers are set you just leave them alone, the work is done by the system....that's what I was trying to say:-)

 

Cheers

 

David.

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So we can enter a maximum take off weight, low flex temp and the FMS will provide the correct power to the autothrottle? A good percentage higher than a minimum take off weight at high flex temp? That's the Airbus FMS as opposed to a Boeing one....once the power levers are set you just leave them alone, the work is done by the system....that's what I was trying to say:-)

 

Cheers

 

David.

 

Not sure I understand what you're getting at here.

 

- You enter a ZFW and the weight of fuel. It assumes (but you can change it) 200Kgs for take off so it shows you a take off weight.

- You then plug that weight plus all the other environmental information (airport, rwy, temp, wind, pressure) into some performance calculation system and it gives you (for each intersection) a Flap, Flex temp, V1, Vr and V2.

- You enter these into the FMGC so when you put the thrust levers into Flex (or TOGA if required) you'll get the right amount of thrust.

 

If you stop before V1 you shouldn't go off the end of the runway and if you rotate at Vr you should safely climb away without hitting anything. At Acceleration Altitude you move the thrust levers to climb and then they generally won't be moved until much later on in the approach.

 

The amount of thrust you get is dependant on the Flex temp you enter (higher temp, lower thrust).

The maximum take off weight is irrelevant and there's no real use for a minimum take off weight.

 

This methodology broadly speaking works for Boeing as well (higher assumed temp = less thrust) but Boeings tend to have some performance data in the FMS. We only use it to cross check the data we get from our performance tool (we should be within 3 kts of the FMS figures) but the performance tool is much more refined and is working with much more information than the FMS.

 

Whether the thrust levers move makes little difference in this arena, in the Boeing the thrust automatically comes back to CLB at Acceleration Altitude and for the whole flight the levers dance forward and back as they see fit but for both types the thrust is managed automatically.

 

Not sure if I've understood your question and hence if I've answered it at all but hope it helps anyway,

 

Ian

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Great info, thank you Ian. I fly the FSL A320 and more info I can vacuum up the better.

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You mean the SID chart? Where exactly is that information located on the chart/plate?

 

Not the SID chart (generally) -- usually runway dimensions and declared distances are shown on the ground chart (AGC in Lido parlance if you use Aerosoft/Navigraph charts).

 

The "full length" dimensions are usually printed within the runway diagram itself (eg 3100 x 45m). If intersections are available for takeoff, there will be a little flag showing the TORA from that intersection (so a particular intersection -- we'll call it B -- might have 2800m available).

 

The shift would be the difference between the full length and the intersection (in this case, 300m). As mentioned above, it is purely to provide the data for an FMGC position update -- in the old days of pure IRS, the FMGC would automatically update its position to the co-ordinates of the threshold of the runway selected for departure when TOGA was selected, therefore if you are departing from anywhere other than the full length (i.e. from an intersection) you would need to enter the shift to improve the accuracy of the position update (in the example above, failing to enter the shift would mean the FMGC position would be 300m out). If I recall correctly, if GPS Primary is available this position update is inhibited anyway on the Airbus so it's not all that critical, though it is possible that the Aerosoft Airbus uses it for calculating the flex temp and V speeds -- I'm not sure.

 

The flap setting is just the flap setting you plan to use for departure. In the Aerosoft Airbus you can just enter a flap setting - 1, 2 or 3 -- and (if you have entered the weights correctly previously) it will automatically calculate a flex temp and V speeds. In real life you would use a performance calculation tool (either paper tables, an on-board laptop/tablet or in some cases you would send an ACARS request back to a computer at the airline head office) which will give you a suitable flap setting and associated flex temp & V speeds. The flap setting depends heavily on airline SOP and the conditions on the day -- if runway length and obstacles are not a factor then many airlines will choose to use as little flap as possible (i.e. Config 1) because this is less draggy and will therefore get you climbing quicker and save some fuel, but the downside is that you will have higher takeoff speeds, a longer ground roll and typically slightly less tail clearance on rotation than with greater flap settings. If field length is limiting, then a higher flap setting will be required (up to Config 3) resulting in lower takeoff speeds and a shorter ground roll, but this will reduce your initial climb performance (because it is more draggy). Software such as TOPCAT will give you this information but it only has a performance profile for the CFM-engined A320. If you want to use the Aerosoft takeoff performance 'cheat' then just pick a flap setting and see if it comes back with an answer; if it doens't give you a flex temp and/or V speeds then the runway is too short for the selected flap setting and you will need to try more flap.

 

The THS entry is your takeoff stab trim setting and this entry is purely a reminder in the Airbus (though obviously actually setting the correct value on the trim wheel before takeoff is important!). The value itself will depend on the loading of the aircraft (i.e. the CG) which in the Aerosoft Airbus you set in the right MCDU when you set the fuel and payload. In real life there is a CG scale on the trim wheel which you should set to the current GWCG prior to takeoff; there is a scale on the bottom of the checklist that converts CG to units of trim, which can be used to complete this entry, but I'm not sure if Aerosoft included it in their checklist.

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