Hi everybody, somebody can help me with this?..I have a problem that has been in the sim for some time now, cruise speed dropping to 243 knots on the A320 and 747-8 and it hasn’t been resolved so far, I don’t know what happens
243 is the indicated airspeed (IAS). You are are 34000ft, the air is thin up there, so the indicated airspeed is low. For the real number, look at ground speed (GS) or True Airspeed (TAS).
Why this dont happened before and with 787-10 too dont happen?
not to mention that with o747/737/777 from pmdg in other sims, this does not happen, so I understand that this is not normal behavior for this type of aircraft, before it did not happen in this sim either, but it’s been a long time like that… .also remembering that the A320 doesn’t have this behavior either, I remember Aerosoft in other sims
Chistiano,
I doubt that this does not happen in other sims, unless the IAS is not modeled correctly.
Take a look here for an explanation : https://medium.com/how-to-aviation/understanding-true-airspeed-cc932edaca00
ok, I’m not referring to what speed is what, but rather and only the speed indicated on the artificial horizon, which as far as I know, even more on short flights, doesn’t decrease so much, when they drop from 310 knots (for example with the A320N) , it drops to 295 knots, this is the behavior I’ve seen since FSX and with 737-800 Zibo on XP 11 too, in the end this I understand as being a standard behavior for this type of aircraft
Install the Flybywire A32NX mod and see if it happens there.
I’ve never flown the 747 in game but almost all Auto flight systems in jets switch to Mach number somewhere around 25,000-30,000ft.
A 747 would generally cruise faster than M0.80. A typical cruise speed for the 787 is M0.85.
It looks to me like you’ve climbed in IAS and for whatever reason haven’t switched. You would ordinarily climb at a given IAS until you met your intended Mach number then switch and maintain that. As you get higher the IAS drops but your Mach Number would remain constant. Of course, if your FMC was programmed correctly and you were using VNAV that would all happen automatically, assuming it’s modelled.
That reads like a load of garbled nonsense to me but hopefully it makes sense! 
It absolutely does. I fly PMDG and FSLabs in P3D - it happens on ALL their aircraft as well as in real life.
As you get above, the air becomes thinner, thus the sensors that display indicated airspeed are “confused” by it, so the TAS is the number to go by. Also, at FL340, you should really be using Mach speed, not IAS. Those are specifically used for higher altitude flying because your IAS will change drastically as you climb.
There are a couple of things to check, I did notice your Mach speed is low and also the ref speed is even lower.
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on the FMC, check the crz references. If it’s set incorrectly, it will follow whatever reference speed is listed.
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Although I’m not sure if it’s model correctly or not, but the Cost Index maybe at a lower range. On a 747…it should be at least set at 100. Higher Cost Index just tells the FMC it’s ok to burn more fuel. On an Airbus, the value should be at least 35.
Hope it helps…
No, neither with FBW nor with 787-10
Also, you have a headwind of about 50 knots, which will also slow your plane
Wind has nothing to do with aircraft performance and neither IAS nor TAS are affected.
That would have no effect on the IAS or Mach Number though.
Yeah thats right. It only changes gs, my bad
Excactly. The OP has posted the identical problem in another thread, but with screenshots and there’s no crz speed in the FMC. Only the 310/242kts transition speeds.
yes, you are speaking my language now…however, I use ci of 100 on the 747-8 and it doesn’t seem to make a difference (when it comes to standard aircraft) and on the A320N I use ci of 35 and no difference, they continue with the same behavior
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