Pete, I only assigned all axes in FSUIPC to determine if P3D was somehow the cause, but rolled back all assignments to P3D after determining it did not matter if P3D OR FSUIPC had control over axes.
I was finally able to reproduce the spike with your suggestions. I edited the INI file to include your suggestions, then clicked on "Axis Controls," then "New Log." I waited until the initial spike to start the logging, hoping the next one would happen quickly but it did not until later. I cannot upload one log file but two were created: fsuipc5.1.log and fsuipc5.log (attached). As soon as the ailerons went full left, I stopped the log. Please let me know if there is something else I should do. I copied the beginning 30 or so lines and then skipped to the bottom and copied the last 30 or so lines of fsuipc5.1.log:
Module base=7FF91A1B0000
Windows 10 Home 64 Bit reported as Build 15063, Release ID: 1703 (OS 10.0)
Prepar3D.exe version = 4.1.7.22841
Checking the Registrations now ...
User Name="Jonathan Vida"
User Addr="syndola@@hotmail.com"
FSUIPC5 Key is provided
WIDEFS7 not user registered, or expired
47 System time = 09/01/2018 21:43:24
47 FLT path = "C:\Users\syndola\Documents\Prepar3D v4 Files\"
47 ------ Module Version Check ------
47 acontain.dll: 4.1.7.22841
47 api.dll: 4.1.7.22841
47 controls.dll: 4.1.7.22841
47 fs-traffic.dll: 4.1.7.22841
63 G3D.dll: 4.1.7.22841
63 language.dll: 4.1.7.22841
63 sim1.dll: 4.1.7.22841
63 visualfx.dll: 4.1.7.22841
63 weather.dll: 4.1.7.22841
63 window.dll: 4.1.7.22841
63 ----------------------------------
110 FS path = "D:\Prepar3D v4\"
250 ---------------------- Joystick Device Scan -----------------------
250 Product= Saitek Pro Flight Yoke
250 Manufacturer= Saitek
250 Vendor=06A3, Product=0BAC (Version 3.4)
282 GUIDs returned for product: VID_06A3&PID_0BAC:
282 GUID= {518DE8E0-3626-11E5-8005-444553540000}
282 Details: Btns=23, POVs=(0, 0, 0, 0), Cal=x00000000, Max=R0,U255,V255,X1023,Y1023,Z255
282 Product= CH PRO PEDALS USB
282 Manufacturer= CH PRODUCTS
282 Vendor=068E, Product=00F2 (Version 0.0)
282 GUIDs returned for product: VID_068E&PID_00F2:
282 GUID= {518B77E0-3626-11E5-8004-444553540000}
282 Details: Btns=0, POVs=(0, 0, 0, 0), Cal=x00000000, Max=R0,U0,V0,X255,Y255,Z255
282 -------------------------------------------------------------------
282 Device acquired for use:
282 Joystick ID = 1 (Registry okay)
282 1=Saitek Pro Flight Yoke
282 1.GUID={518DE8E0-3626-11E5-8005-444553540000}
282 Device acquired for use:
282 Joystick ID = 0 (Registry okay)
282 0=CH PRO PEDALS USB
282 0.GUID={518B77E0-3626-11E5-8004-444553540000}
282 -------------------------------------------------------------------
329 LogOptions=00000000 00010091
329 SimConnect_Open succeeded: waiting to check version okay
329 Opened separate AI Traffic client okay
Note:......most of the items between these two lines are identical to the following lines...
765719 ###JOY### Event seen, ID=66504 (0x000103C8), Joy=32, value=-519
765719 Axis calibration: Control=66504, Original=-519, Calibrated=-519
765719 ###JOY### Event seen, ID=66503 (0x000103C7), Joy=33, value=5646
765719 Axis calibration: Control=66503, Original=5646, Calibrated=5646
765766 ###JOY### Event seen, ID=66504 (0x000103C8), Joy=32, value=-521
765766 Axis calibration: Control=66504, Original=-521, Calibrated=-521
765766 ###JOY### Event seen, ID=66503 (0x000103C7), Joy=33, value=5641
765766 Axis calibration: Control=66503, Original=5641, Calibrated=5641
765813 ###JOY### Event seen, ID=66504 (0x000103C8), Joy=32, value=-523
765813 Axis calibration: Control=66504, Original=-523, Calibrated=-523
765813 ###JOY### Event seen, ID=66503 (0x000103C7), Joy=33, value=5637
765813 Axis calibration: Control=66503, Original=5637, Calibrated=5637
765860 ###JOY### Event seen, ID=66504 (0x000103C8), Joy=32, value=-524
765860 Axis calibration: Control=66504, Original=-524, Calibrated=-524
765860 ###JOY### Event seen, ID=66503 (0x000103C7), Joy=33, value=5634
765860 Axis calibration: Control=66503, Original=5634, Calibrated=5634
765907 ###JOY### Event seen, ID=66504 (0x000103C8), Joy=32, value=-525
765907 Axis calibration: Control=66504, Original=-525, Calibrated=-525
765907 ###JOY### Event seen, ID=66503 (0x000103C7), Joy=33, value=5632
765907 Axis calibration: Control=66503, Original=5632, Calibrated=5632
768000 Ready Flags: Ready-To-Fly=Y, In Menu=Y, In Dlg=Y
768000 Sim stopped: average frame rate for last 375 secs = 22.4 fps
768000 Max AI traffic was 184 aircraft (Deleted 0)
[Log closed by user request, and continued in new file]
772985 System time = 09/01/2018 21:56:17, Simulator time = 14:06:13 (18:06Z)
772985 *** FSUIPC log file being closed
Minimum frame rate was 8.3 fps, Maximum was 29.5 fps
Average frame rate for running time of 375 secs = 22.4 fps
Maximum AI traffic for session was 184 aircraft
Memory managed: 151 Allocs, 149 Freed
Thank you again!
fsuipc5.log