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Guest decker009

Speeds

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Heres a situation in the airbus a340 the latest patched version. You set a flight up in the fmc climb to altitude lets say fl350 the system changes to crz mode where a CI entry of 100 in the CRZ page gives me a 330 knot entry for speed. Meaning the aircraft wont go any fast than that which is about mach .60 or so obviously below the red bar. Now when I enter a CI of lets say 500 is still stuck at the ECON speed of 330 no matter what. I would think a CI of 100% should maximise the aircraft speed. Now when I change in the INIT page the FL altitude lets say currently it says fl350 i put fl360 the CI of 500 entry gives me a speed of about 485 knots and the aircraft shoots up to that speed and I could keep on punching a CI of like 600 or more meaning overspeeds of over mach 1. Something is obviously wrong here.

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A CI of 100 does not mean 100%, it is just a figure on a scale of 0 to 999. Most airlines choose a fairly low figure, for example United and GB Airways use 35 and BA uses 28 (although neither BA nor GBL have A340s).A lower cost index results in a slower, steeper climb that gets you to cruise altitude sooner, increasing the time at optimum altitude. It provides a slower cruise mach and a shallower descent profile.A higher cost index results in a faster, more shallow climb, gets you to cruise altitude later, decreases your time at optimum cruise, provides a faster cruise mach (so you burn more fuel) and uses a steeper descent profile.What you have picked up quite correctly is that the MCDU will allow you to enter a CI that will cause severe overspeed warnings and inevitably lead to structural damage. So you don't enter those figures. You select a CI that will give you good trade-off between speed and fuel economy. I stick to to the GBL/United figure of 35 but you may want to try other figures to see what they give you.

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So what youre saying is this aircraft cant fly any faster than 350knots. Cause the red bar is always no matter what at 350 knots max. And there is no way to attain a faster crusing speed under the mcdu unless you raise the FL in the mcdu once youve established cruising altitude. From lets say fl350 to fl360 then the mcdu will do the speed you set in it according to the CI. What Im basically stating is that this bird is suppose to cruise at higher speeds than 350knots, so theres something wrong with this cause you are maxed out at 350 always no matter fuel settings or altitude settings.

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Don't forget we're talking about Mach/IAS here not ground speed.

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I know what Im talking about thats the max speed. It does not hit the typical cruise speed of mach 0.78 - 0.82 it never does unless it is in the redbar and that change of altitude is done in the mcdu. Something is not working right. Can one of the forum admins confirm this why the aircraft never hits under MCDU control the cruise speed of mach0.78-0.82 in any load or altitude. It always maxes out at 350 knots Vmax no matter what load your in when the A340's cruise speed is mach 0.78-0.82

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At low altitudes, the A340's max IAS is 330knots (NB not 350 knots as in the PSS sim). This will correspond to a low mach no. (Don't have wizz wheel to hand, but I guess about 0.5 -ish)Climbing normally at about 300 knots IAS, your mach number and TAS will increase to the point where above FL310 or so you will cruise comfortably at a TAS of around 500 knots and Mach 0.8 (check the PFD and ND), but your IAS will still be below 300 knots.This is normal aircraft behaviour, and (apart from the Vmo) the PSS sim reproduces it accurately.hope this helps

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I understand that and verified that it was indeed doing the mach 0.82 speed at fl310 or up crz speed, but the PFD still displayed a speed of around mach 0.52. Why is that , why doesnt the pfd display the actual airspeed. Ive flown quite a few addons and I may be mistaken here cause this may be different but I will think a pilot would like to see the true mach speed hes doing on the PFD. Cause even on the ND it still shows the actual mach 0.52 or so your doing and not the full 0.82. So basically you got no way of knowing what speed are you actually flying at. Youre ovbiously doing the full mach0.82 cause the mcdu flight plan page times correspond to those speeds but other than that youre guessing cause even on the mcdu fpl page it still says your crz at 0.52 or so instead of the 0.82

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