H20 Takeoff = 0-60% ACCEL timer starts

[Nealius]

I noticed something weird today. Could have been a one-off thing but I will have to check again. Before takeoff I do (or try to do) acceleration checks. I hit the OSB button to clear the timer, turned the H20 on since I intended to use it, and the 0-60% timer started ticking. When I turned H20 off the timer stopped.

 

I then cleared the timer again, and ran the engine up to 60% with H20 off. 2.4 seconds, which seems normal. Strangely, after doing an H20 off acceleration check, I tried again with H20 on and the bug did not occur again. I did, however, record video of it happening the first time.

 

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[mvsgas]

The timer will start counting any time the RPM go above idle. So when you place the water switch to TO it will activate. According to the manual it sounds like normal behavior. If you complete the test first and then set the water switch to TO, it won't activate the counter because , well you completed the test.

Edited May 26, 2018 by mvsgas

[Nealius]

Something is inconsistent, though. My second flight this never occurred. I also noticed after re-watching the video, with H20 on the fan RPM showed as 35%. I understood that it should be 34%, and thus not starting the timer.

 

I also understand from the procedures in NATOPS, that the acceleration check should be performed with the H20 at the same settings as takeoff. Ergo, conducting an acceleration check with H20 on if the takeoff calls for H20, and conducting an acceleration check with H20 off if the takeoff calls for H20 off. With this phenomenon, it would be impossible to conduct an acceleration check with H20 on.

Edited May 26, 2018 by Nealius