Hi, i have recently had problems with my FSX, the contrails coming from the engines are black squares, any help?? Thanks. P.s I have some pics off the internet.

-Hani Freij 

Hi Hani,

Firstly, do you use modified contrails.

Have you made a backup of your \Effects & Effects\Texture  folder  (this might be needed to resolve your issue)

Have you un-installed any aircraft using the aircrafts' uninstaller .exe

Sometimes un-installers can be aggressive and indiscriminate when removing their contents, they can remove things they shouldn't. Hence the black contrail.

Incidentally: you will notice that high altitude AI aircraft have black contrails as well as your user aircraft. (Once you resolve the .fx all contrails should be fixed AI and User craft).

These 2 files you must look for, and confirm they still exist in your effects folder. 
FSX root  \Effects  fx_contrail_l.fx   &   fx_contrail_s.fx   
If they are missing, and you have backups of the Effects folder you can copy the 2 files back to the Effects folder.

Lets see how we go with those 2 files first, then make a plan if things are still amiss.

Corrupted effects file.  Download and run this file from the library here or at Flightsim(dot)com.

gauges_recovery_fsx.zip