Hi,

 

I am having a repeating problem with my aircraft in P3D mainly the NGX and aerosoft airbus, where I'm cruising at flight level and the speed slowly starts to bleed back, the autothrottles then move forward but the speed continues to bleed back. I checked my aircraft fully over, the gear, flaps and spoilers are up.

 

Any ideas what maybe happening

 

Joe

Hi Joe, do you have pitot heat on?  It could be freezing over.  

The pitot heat is on

 

Joe

Hi,

 

I think of two factors that could explain that: wind aloft and icing.

How is the weather managed in fsx? real fsx weather, weather scenario, weather addon?

 

Is the wind changing when the speed drops?

Are you flying in clouds?

Hi Joe, do you have pitot heat on?  It could be freezing over.  

 

It would then remain constant, and would only change if you tried to climb or descend.

 

 

 

Is the wind changing when the speed drops?

 

This is my bet. Probably a weather add-on not smoothing the wind enough.

Check your OAT on the eicas display. It should show a minus temp.

Ditto Dave's recommendation.  A loss of thrust at altitude is almost always a problem with the simulated temperature. You have immediate access to TAT on the ND and SAT is available in the FMS. You should be familiar with the expected temperatures.

 

 

It would then remain constant, and would only change if you tried to climb or descend.

 

Ah yes, right you are, just read up on it.

Hi Guys,

 

I am using ASN as my weather engine as I remember a problem with the default weather, the winds stayed the same (a tailwind at around 30 knots), and the TAT is -19

 

Joe 

Hi,

 

As it happens with different aircrafts, I still suspect an external cause probably environmental.

 

Regarding the speeds, Have you checked and compared the IAS, Mach, TAS and GS along with the wind?

 

Also as you are using ASN, can you check in the debug window if there is any icing?

 

Last, does it occur at specific altitude?

Hi,

 

As it happens with different aircrafts, I still suspect an external cause probably environmental.

 

Regarding the speeds, Have you checked and compared the IAS, Mach, TAS and GS along with the wind?

 

Also as you are using ASN, can you check in the debug window if there is any icing?

 

Last, does it occur at specific altitude?

 

Romain,

 

The GS is also decreasing with the indicated, both AFCT start to slowly pitch up, to the point of stalling.

 

I'll check ASN when i have my next flight going. Also both flights were at FL350

 

Joe

Well, if both the IAS and GS decrease at the same time, I don't think it comes from the wind.
Stalling because the wind is not smoothed enough usually occurs if the wind turns backward too fast or if it was already from the stern, then increases too fast. In this case, the IAS decreases while the GS tends to increase.

If both IAS and GS decrease at the same time while the engines spool up, it means that either the engines are loosing power or something is slowing the aircraft down.

 

So either you have a failure active with the engines (I haven't checked if some failures exist that could cause a loss of thrust on the engines without a loss of rpm and alarms), or you have some icing on the wings, that creates a loss of lift, compensated by an increased angle of incidence, which induces an increase of drag and eventually a loss of speed.

 

However, icing at FL350 is not so common, but if it could be if you fly in bad weather conditions.

 

Can you also check your SAT and if you fly in the clouds.

 

Finally, it could also come from something else that I have totally missed out!  :wink:

I have got service based failures on but when I look at the fmc it says nothing's active

 

Joe

Joe,

 

Just to tag on to what Romain was getting at.  Is there any chance this could be the Icing effect? Have you turned on WAI and TAI to see if the situation improves? 

I'll test this, but I won't have time till the weekend, due to A-Levels.

 

Joe