PDA

View Full Version : Af3400 hdg anomoly



Brad Hood
03-24-2010, 09:29 PM
Rob,
I have installed the AF3400 EFIS & EM. All of the functions appear to be working after test flight with the exception of a fairly gross error in heading. This system is installed in a previously flying F-1 Rocket. The magnotometer is located in the aft fuesalage away from all ferrous metal sources. Upon initial power-up of the system (prior to aligning the mag) the heading was spot on on the ground compared to airport references and subsequent test flight proved this to be true as well. I flew the airplane up and down multiple runways and then perpendicular to check hdgs. Since the magnotometer align message was staring me in the face, I decided to align the system and after 2 alignments the heading is off about 15 deg from every checked reference.
The magnotometer is mounted very true in relation to the AHRS/3400 boxes. I followed the directions to the letter during the mag align. One thing I noticed while using a hand held compass alignment instrument was this: I started with the airplane pointed North hdg 360 and then followed the instructions. I turned the airplane until the unit told me to stop which was spot on 360 again. It then told me it needed a 2nd turning circle and again it stopped me at 360 deg. When it was finished I was sure that it must be right, but sure enough when the airplane is flown its 15 deg or so off. The GPS map compass rose appears to be dead on so I can compare the difference in the EFIS hdg that way as well.

Is there any way to force calibrate this thing or trick it some how? Some other brands have provisions to adjust these differences out. I'm hoping you have some ideas, as I am out.
Otherwise, I am very pleased with the whole system. I would really like to see all the letters and numbers increased in size in a future software upgrade. I have 20/20 vision and all the nomenclature is really hard to read due to size. I believe the font size could come up considerably and not detract from the display.

Thanks Rob,
Brad Hood

vic syracuse
03-27-2010, 03:13 PM
Brad, what indicator are you looking at for heading while in flight? If you are looking at the top of the MAP page, then it is actually showing ground track, and it will not match the heading unless in a zero wind condition. The heading indicator on the HSI portion of the PFD should be accurate. It drove me nuts for a while to see the difference between the HSI on the pfd (my screen 1) and the heading at the top of the page on the MFD, which I configured for MAP, until I realized it was showing ground track.

Vic