my main FlightGear pages

FlightGear low-altitude uneven autothrottle 777 bug fix (versions and


In the Boeing 777 (most likely any of them, although I'm using the 777-200ER), when you're coming in for a landing with auto-throttle, at somewhere between 250 - 320 feet agl, you'll notice that the right and left engine thrust becomes uneven. For example, I've paused the simulator at 250 feet agl: left N1 (percentage) shows 53.8, right 43.8. N2 is also off, of course. When I unpause, the right engine is frozen at 43.8 and the left engine keeps adjusting to conditions. The plane becomes harder to control. (The problem almost certainly begins at 400 ft agl, but I didn't notice it until 340 or 320 or lower.)

90% Solution / best fix I have

Here are the fixes in xml and txt format. In Windows, this is a change to your equivalanet of C:\Program Files\FlightGear\data\Aircraft\777\Systems\777-autothrottle.xml If you use the txt file, you'll have to rename it to the original name and extension, of course. My only changes were to comment out 4 blocks of code, as I discuss.

This is a 90% solution because I break a real-world safety feature--I commented out the feature that keeps AT from engaging under 400 feet. My partial fix is a heck of a lot better than the bug, though, if I do say. Because I'm breaking something, I'm not comfortable submitting this to the code base as a total fix.

At the moment, I have no interest in making a 100% fix, but I might be persuaded.

Multiple descriptions, to try to get web searches:

AFDS.nas Fix

I only mention it here because it was originally mentioned in this page, and the new page didn't exist when I uploaded the .nas file. See the header link just above for an explanation.

Page History

2013/08/14 2:47am - added xml and txt file. Moved diff and commented-out code to another file. Moved AFDS except for brief mention.

Created 2013/04/04 11:54pm EDT or a bit later.

Valid XHTML 1.0 Strict