Strange slip indication on the factory installed 30 year old turn coordinator on my Turbo Arrow. When taxying in a straight line, and parked up stationary, the slip indicator is offset to the right out of the neutral marks. I had previously thought the “aircraft” turn symbol to be electrically driven but the slip ball to be passive, much like a spirit level. Am I right in now saying this is not the case and I have a fault? In the air it reads the same and suggests I need an enormous amount of right rudder to stay in balance, which leads to a low left wing state.
If so, I think it’s time I binned this ancient relic and fitted a more useful electric instrument in its place. I have a suction driven Artificial Horizon and a conscious I have only one vacuum pump with no redundancy. Perhaps an electrically driven AH with slip indicator in place of the old turn co-ordinator would be a sensible option.
I should add that I have a Bendix King KAP150 autopilot. I’m concerned that removing the turn coordinator may upset the feed to the computer of this. Is this a correct assumption? I have a KI525A HSI that still functions well.
Any thoughts or experiences / recommendations of modern systems to fit would be appreciated.
Yes, the skip indicator is nothing bit a spirit level. The instrument can be rotated in the instrument panel and thus the zero indication can be adjusted. Avionic shops can do that since they normally have piece of tarmac that is known to be perfectly level (for example where they do compass swings). Your instrument might have “crept” somewhat and it could potentially be a very easy fix.
I don’t think the KAP150 uses a turn coordinator at all. It uses the vacuum AI (KI256, or earlier model if no flight director) for pitch/roll information.
You can’t get rid of the vacuum AI and still keep this autopilot. There are options which are technically fine but the best ones are not paperwork-viable. I have some notes deep in here – search for “how to get rid”.
The Aspen EFD1000 or the Garmin 500 will enable removing the vacuum AI because they provide an emulator for it (EA100 or GAD43 respectively).
Boscomantico is right, it seems the instrument is just not level in the instrument panel. The holes for this instrument are enlonged so it can be rotated to read level with the aircraft level, it should be very easy to adjust unless the slip indicator won’t move freely / has friction.
If you want to upgrade to glass the Aspen EFD1000 Pro is a senseble option as Peter suggest. The G500 lacks free European STC’s, so with the G500 on an EASA aircraft you should consider you pay a reasonable amount extra for an STC. The Aspen comes with an STC for a lot of aircraft.
If you fly N reg both come with an American STC so the price difference between them is much smaller.
Offcourse your aircraft must be on the AML list of the STC to benefit from this.
Allthough the KI256 can be removed and simulated with the EA100 or GAD43 it should be considerd if you want this. As in most installation you would be required to get an extra AI besides the EFD1000 or G500.
Problem solved by adjusting the instrument on the ground as you described. Thanks for the advice.
