Rich Posted December 12, 2015 Report Share Posted December 12, 2015 Good afternoon, My aircraft has been OOS for three weeks due to some issues with the TT APIII, RPM readout and MAP readout. Seems like there was a resistor that went bad in the unit causing a lower voltage within the unit. RPM's were reading 1700 while the throttle was set at the 75% setting. The AP was flying left wing low (about 3 degrees) while tracking a perfectly straight course in conjunction with the GPS flight plan. Manifold pressure was reading in PSI instead of HG. This was also fixed. What puzzles me is that some oil was found in the MP sensor inside the EFIS. How can this be possible when it's pulling a vacuum? There is no oil being used and the exhaust pipe is clean. Plugs were perfectly clean as viewed in a previous post. Any ideas? Link to comment Share on other sites More sharing options...
Anticept Posted December 12, 2015 Report Share Posted December 12, 2015 Probably not engine oil, more likely machine oil. As to where it came from, that would be the question Link to comment Share on other sites More sharing options...
Roger Lee Posted December 12, 2015 Report Share Posted December 12, 2015 If you have a K&N air filter people tend to over oil them. Sometimes even from the factory and with enough air flow some oil can migrate out. This is most likely the source of the oil that migrated into the balance tube and into the map tube. Even if you don't have that balance tube the filter oil can coat sensors. I have seen this 2 other times. Link to comment Share on other sites More sharing options...
Runtoeat Posted December 13, 2015 Report Share Posted December 13, 2015 Hi Rich. Trying to visualize the TT AP flying the plane with one wing low and staying on course? My TT AP is 2 axis and uses aileron to hold heading or turn the plane. Not sure if your TT III has 3 axis which uses rudder for turns? If the version III doesn't use rudder, I'm thinking the TT was trying to turn the plane and opposite rudder was applied to maintain course? How did your resolve this issue? Link to comment Share on other sites More sharing options...
Doug G. Posted December 13, 2015 Report Share Posted December 13, 2015 You can fly one one wing low by using rudder trim while using the AP. Many of us use that method for fuel transfer on our CTs. Link to comment Share on other sites More sharing options...
Rich Posted December 13, 2015 Author Report Share Posted December 13, 2015 Roger, Thank you. I never would have guessed that. Dick, The TT AP III is not three axis. The III over the II just gives you the opportunity to set your altitude and let the plane fly to it. I'll receive the units back this coming week. Hopefully it will be resolved and the low UNIT voltage was the issue. Lucas and Zach have been easy to work with, however, the units we both have will not have hardware support going forward. TT will be able to fix issues that are not hardware related, i.e. sensors, resistors and so on. Doug, The plane was hands off flying straight and level. When the AP was turned on it went wing low and the ball on the panel went to the left side while the ball on the TT unit was centered. The lower voltage in the TT unit hopefully was the problem. I'll know when I install it this week and take it up for a ride. Thanks to all. Rich Link to comment Share on other sites More sharing options...
Doug G. Posted December 13, 2015 Report Share Posted December 13, 2015 I believe there are TT settings for that, but I have not needed to change anything do I am not certain. I am certain there are others here who will know. The TT manual should tell you if there is a setting. You have a ball on your YT? unit? We are evidently talking about different animals here. Link to comment Share on other sites More sharing options...
Rich Posted December 13, 2015 Author Report Share Posted December 13, 2015 Doug, Take a look at my album section. You'll see the TT AP III that I have. There are no settings that I can make. It had the low voltage problem, so I'll see what happens in a few days. Rich Link to comment Share on other sites More sharing options...
FlyingMonkey Posted December 13, 2015 Report Share Posted December 13, 2015 The AP just maintains a GPS or magnetic heading line, it doesn't care if the airplane has to fly sideways to do it. Link to comment Share on other sites More sharing options...
gbigs Posted December 14, 2015 Report Share Posted December 14, 2015 The AP just maintains a GPS or magnetic heading line, it doesn't care if the airplane has to fly sideways to do it. Which AP are you using? Mine flies to waypoints and will climb and descend in director mode. Link to comment Share on other sites More sharing options...
Doug G. Posted December 14, 2015 Report Share Posted December 14, 2015 The AP just maintains a GPS or magnetic heading line, it doesn't care if the airplane has to fly sideways to do it. True, but it shouldn't always be one direction. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted December 14, 2015 Report Share Posted December 14, 2015 Which AP are you using? Mine flies to waypoints and will climb and descend in director mode. They all work the same. A point to navigate to is selected, and then the AP draws a line between that point and the current location using basic trigonometry** and then the AP keeps the airplane on that line via the servos. If you disconnect the AP and fly significantly off that line, the AP will try to go back to that line when re-engaged, unless you plot a new "direct-to" line for it to follow. A more complex multi-waypoint flight plan is simply a collection of such point pairs, with the end point of one line being the start point of the next. All this layout is done in two-dimensional space**, any climbs or descents dialed in to the AP do not affect the endpoint navigation. ** There might be some variation from a straight line course if the AP is doing "great circle" calculations to account for the curvature of the Earth. In that case everything I said above is still correct, but the course line/curve calculations are made using Newtonian Calculus instead of simple trigonometry. Link to comment Share on other sites More sharing options...
Ian Posted December 14, 2015 Report Share Posted December 14, 2015 Surely spherical triangles rather than calculus? Link to comment Share on other sites More sharing options...
FlyingMonkey Posted December 14, 2015 Report Share Posted December 14, 2015 Surely spherical triangles rather than calculus? Perhaps. I'm not really a math guy. I just assume lines = trig and curves = calculus. Link to comment Share on other sites More sharing options...
Anticept Posted December 14, 2015 Report Share Posted December 14, 2015 Autopilot systems are very simple. They just receive a few things, like heading from a mag compass, course from the nav system (if supported), deviation from course line (if supported), and orientation from accelerators, and do some pretty simple PID control (with some tweaks of course). Nav systems, however, are not so simple. They are the ones dealing with curvature, etc. Link to comment Share on other sites More sharing options...
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