Adjusting the KA 51B Slaving Meter
 

Hi,

The HSI on a plane I fly is about 20 degrees out (sometimes!) and I am not clear how to re-align correctly.

The manual says you switch to the 'Free' mode which is fine. then...

2 Questions...

1) Do I then do a clockwise/counter clockwise adjustment based on the 'Slaving Meter' or the aircraft 'Compass'?

2) Why wouldn't I just adjust to the Compass in which case what is the point of the Slaving Meter which needs to be centered?


Thanks for any advise.

Generally, the remote compass is more precise than a direct-indicating one, provided both are operational. I do occasionally see my HSI fall out of alignment, so I just turn the slaving off and back on while flying straight and level. It resynchronises automatically within a few seconds.

If it is only out sometimes it sounds like you need to swing the compass, I am going to guess that you will find some sort of magnetic interference near the flux detector

The alignment (compass swing) of an HSI involves both rotating the remotely mounted fluxgate magnetometer, and adjusting the KA51B.

20 degrees is quite a lot. I wonder whether somebody has removed the magnetometer (KMT112, usually, on a King system) and put it back in a different orientation?

Or maybe a wire has come off somewhere....

Thank you for your responses.

20 ° is way out of my limits for an HSI to be used under IFR, even if the deviation card for the HSI should show it (which I really doubt). If the deviation card is incorrect by more than 5 °, the plane must not be used for IFR, if I do remember right.

Electric de-icing might cause an additional off-set.

Putting the system in free mode is a good idea in your case and even a legal solution, if placarded at the switch ("slaving u/s, use free mode only").

But since the adjustment is normally not a big deal, the slaving should be fixed.

KA-51B
 

I am grad to reply to any question about KCS55A system, KA51B included.
In fact I have design a tester to check this unit.