Left tank dry, right tank 12 gallons left

[Ed Cesnalis]

 

Now, if I am in a CT and turn on the AP, will it hold my 330 degree heading or will it start turning toward my GPS destination?  That is the question

 

 

 

Okay,  Answer is the CT will hold the heading and not cause a fuel imbalance.  We know the CT's AP is likely flying course mode but it could be flying heading mode.  In either case it is tracking as it is programmed to so there is no change.

 

If the CT made a 30 degree course change in this case it would be unusable.

[Ed Cesnalis]

So, IMHO, without a heading bug or heading hold, while trying to fly a GPS course with a cross-wind, the AP is going to "hunt" a little with a series of uncoordinated slipping turns across the course line until it settles in on a heading in straight and level, coordinated flight that holds the airplane on the course line.  ...

 

Different APs use different logic.  All 1 or 2 axis GPS based systems maintain a track in course mode.  Because airecraft drift with the air-mass any logic based on pointing at the way-point in stead of maintaining a track to the way-point is to severely flawed to work.

 

I have recently been through this with my CT, when the AP is hunting the flaperon gain settings are too low.

[Ed Cesnalis]

Heading mode is simple logic.  It requires only 2 turns to capture a heading and only a compass reading for input.  Heading mode cannot fly to a waypoint, its reliant on the pilot for heading adjustments to get to the waypoint.

 

Track mode which apparantly CTs mostly use is more complicated logic.  It takes 4  turns to capture a track and needs positioning input like GPS or LORAN.  Track mode can fly to a waypoint in changing winds.

[Tom Baker]

CT, I don't know about how your airplane gets its information in heading mode, but the TruTrak is created by the GPS. When you select a heading it is not really a heading. It is a GPS track from the point you were at when it was selected. If there is a crosswind the airplane will continually be blown off that track and trying to turn back to it. It does not have the ability to fly a heading that is independent of a

ground track.

 

With the old style AP you can select a heading that really is a heading to maintain your track across the ground while flying in a crab.

[cdarza]

Am i understanding this correctly.   If my next waypoint is 20 miles and heading say 010,  i set the AP on that track/heading 010,  the AP will compensate for the drift off track?   So, even with winds from left or right, AP will get me to my waypoint?

  I just assumed the pilot would make the necessary estimated correction for wind.  So, in example above, if a strong wind from the east, pilot would make a AP 030 heading to compensate for the winds.  This is wrong?

Shows you i have not read the manual and how often i use AP  

[Roger Lee]

Fuel sight tube video. They don't break.

 

 

https://youtu.be/5E3jSy02pic

[Tom Baker]

Fuel sight tube video. They don't break.

 

 

https://youtu.be/5E3jSy02pic

 

Roger, I don't remember the composition of the tube, but I gave had one tear apart easily when being removed for replacement.

[Roger Lee]

But it still didn't give until you were yanking on it to remove it. They just don't tear when in place. So the old myth about them being brittle and falling apart isn't true. The polypropylene won't give under normal use.

[Runtoeat]

The TruTrak 2 axis AP maintains elevation by controlling the elevator and it maintains the GPS directed track to a destination point by steering thru the ailerons ("banking").  It is up to the pilot to maintain "wings level" attitude during AP use by manually monitoring and trimming the aircraft to maintain nose and wings level attitude.  If there is a fairly constant cross wind during flight, the rudder trim (to keep wings level) once set is fairly constant.  It seems that my pitch trim rarely needs to be readjusted once set.  In my CTSW, if there is a variable cross wind and I don't pay attention to my bank attitude (I've solved my ball callibration and it's accurate) and don't adjust the rudder trim to keep the ball centered, the plane will be slipping and fuel is transferred to the low wing.

[FlyingMonkey]

Maybe we should start a new thread titled "Autopilots and how the track" to have the AP discussion. It's a great topic, but I don't think it belongs n this fuel-related thread.

 

Roger: I'd also like to know the diameter tubing to get for the sight tubes.

[Runtoeat]

Andy, 1/2" od X 3/8" id.  which gives 1/16" wall thickness.  Length is critical to prevent kinking.  I think I use exactly 6" but not 100% sure.

 

I agree about the AP.  Good idea for new thread and put this in the Auto Pilot section on the forum.  OK with me to send AP comments made here to there but not sure how easy it would be to do it?

[gbigs]

 

OK, my desired GPS course line to destination is 360 degrees.  I'm 2 miles to the right of my desired course line.  Wind is from 270 degrees.  So, I turn to a heading of 300 degree and intercept my desired course line.  Then, I turn to a heading of 330 to stay on my desired course line.  My heading is 330, my course is 360, my wind correction angle is 30 degrees.  There is no wind shear.  Wind is constant from 270 and I am flying in the moving air mass.

 

Now, if I am in a CT and turn on the AP, will it hold my 330 degree heading or will it start turning toward my GPS destination?  That is the question.  Obviously, if it has a heading bug set on 330, it will hold that heading.  What does it do if it doesn't have a heading bug or heading selection and it is simply set on GPS destination?  I don't know.

 

 

The CT and the Cirrus ground track the course line with the nose pointed into the wind direction.  They do not veer back and forth over the course line.  There may be slight variances in ALTHLD dependent on wind strength, like a boat bobbing in water....but the planes will track and not vary.  If the wind changes direction the AP will adjust accordingly.

[Tom Baker]

But it still didn't give until you were yanking on it to remove it. They just don't tear when in place. So the old myth about them being brittle and falling apart isn't true. The polypropylene won't give under normal use.

 

Actually the force required was very small, in fact it was kind of scary how easily it came apart.

[Ed Cesnalis]

CT, I don't know about how your airplane gets its information in heading mode, but the TruTrak is created by the GPS. When you select a heading it is not really a heading. It is a GPS track from the point you were at when it was selected. If there is a crosswind the airplane will continually be blown off that track and trying to turn back to it. It does not have the ability to fly a heading that is independent of a

ground track.

 

With the old style AP you can select a heading that really is a heading to maintain your track across the ground while flying in a crab.

 

Okay, with trutrak you select a heading and get a course, interesting.

 

Here's where you are deviating from 'stick and rudder' basics. : If there is a crosswind the airplane will continually be blown off that track and trying to turn back to it. from Crosswinds do not blow aircraft off of their tracks.  The aircraft drifts along with the air mass that causes the crosswind.  

 

There are many things a 2 axis AP can't do but it has no trouble establishing a crab angle that will result in tracking the course.  Only wind shear (changes in wind) can 'blow the aircraft off course' but the AP immediately does a correcting turn.

 

You have to be wrong saying the AP does not have the ability to fly a heading different than the ground track.  It has to do the on virtually every flight because there is almost always some wind aloft and 358 times out of 360 it will have a cross wind component.

 

Call the Trutrak rep and ask him that exact question if your not convinced.

[gbigs]

Okay, with trutrak you select a heading and get a course, interesting.

 

Here's where you are deviating from 'stick and rudder' basics. : If there is a crosswind the airplane will continually be blown off that track and trying to turn back to it. from Crosswinds do not blow aircraft off of their tracks.  The aircraft drifts along with the air mass that causes the crosswind.  

 

There are many things a 2 axis AP can't do but it has no trouble establishing a crab angle that will result in tracking the course.  Only wind shear (changes in wind) can 'blow the aircraft off course' but the AP immediately does a correcting turn.

 

You have to be wrong saying the AP does not have the ability to fly a heading different than the ground track.  It has to do the on virtually every flight because there is almost always some wind aloft and 358 times out of 360 it will have a cross wind component.

 

Call the Trutrak rep and ask him that exact question if your not convinced.

 

Yes. This is as I have described it above. 

 

Another fun note.  When ATC gives me a vector I switch from NAV mode with GPS as the source and over the HDG mode and turn the HDG knob to the vector ATC has specified.  If there is wind the plane may track a different course, but it's what ATC asks for and that's what I give them when getting close to an airport.

[gbigs]

Here's where you are deviating from 'stick and rudder' basics. : If there is a crosswind the airplane will continually be blown off that track and trying to turn back to it. from Crosswinds do not blow aircraft off of their tracks.  The aircraft drifts along with the air mass that causes the crosswind.  

 

There are many things a 2 axis AP can't do but it has no trouble establishing a crab angle that will result in tracking the course.  Only wind shear (changes in wind) can 'blow the aircraft off course' but the AP immediately does a correcting turn.

 

 

Yes. This is as I have described it above. 

 

Another fun note.  When ATC gives me a vector I switch from NAV mode with GPS as the source and over the HDG mode and turn the HDG knob and bug the vector ATC has specified.  I am guessing ATC doesn't care about ground track (we have had this discussion before I think).  I am always hand flying when getting close to an airport so the AP is not a factor, I just turn to the heading indicted on the HSI.

[Tom Baker]

 

 

You have to be wrong saying the AP does not have the ability to fly a heading different than the ground track.  It has to do the on virtually every flight because there is almost always some wind aloft and 358 times out of 360 it will have a cross wind component.

 

 

 

CT, I know you have a different AP than TT. What is the source of steering for your AP? Here is a simple test to check what I am describing. Go out on a day when you have a noticeable crab when flying in a crosswind. Turn on your AP in heading mode and select a heading with a 90° crosswind. Look at you compass and your GPS ground track. Which is the airplane following? With TT if the GPS signal is available it flies a GPS track when in heading mode.

[Ed Cesnalis]

My AP has a number of modes, some heading and some course.  I even have a heading bug and a course bug.  With my course bug the input is similar to heading but it tracks a course and compensates for changes in the wind.

 

Just like any other GPS based 2-axis AP the source for steering is the GPS in course mode and the magnetometer in heading mode.

 

If your trutrak flies a gps track in heading mode it is really in course mode and that's fine, no point of contention there.

 

Our point of contention is whether or not your AP has the ability to fly a heading different than the ground track.  You say no I say yes, of course it can.  I already pointed out that 358 times out of 360 when there is wind aloft it has to fly crabbed to its course line to maintain it.

 

Just look at it from the logic or programmers point of view.  When he is tracking a GPS course all input he needs to decide to continue on course or initiate a correcting turn is GPS input, magnetometer input can provide a crab angle which becomes useful when the decision to correct the course comes in.  With the addtional magnetometer input the programer can add the logic to decide if the first correcting  turn is a left or a right and even if its a steep or shallow turn.

 

The logic of what you describe doesn't exist, its completely illogical.  You are describing a heading mode that is really a course mode that seeks to conflicting things: 1) the usually incorrect heading; 2) the course.  You point out that it results in searching.  Consider that the searching comes from AP gain settings and such and not crosswind confusion on the part of the AP.

[FlyingMonkey]

 

If your trutrak flies a gps track in heading mode it is really in course mode and that's fine, no point of contention there.

 

Our point of contention is whether or not your AP has the ability to fly a heading different than the ground track.  You say no I say yes, of course it can.  I already pointed out that 358 times out of 360 when there is wind aloft it has to fly crabbed to its course line to maintain it.

 

 

My TruTrak uses GPS heading for its reference.  What I am not sure of is whether it flies a heading (always pointed to the same heading) or a course (on a course line in the heading direction from the time you engage the heading mode).

 

The unit does say HDG mode.  But I can't remember is if once you roll a heading in if the display says CRS or HDG.  If it's actually flying a course when it says it's a heading, that could cause potential problems.  I tend to like a course better because it's more precise, but ATC and pilots need to be on the same page when they request us to fly a heading...

 

I'll have to do some testing on this with the TT to know the answer, unless somebody else has already tested this or knows the answer.

[Tom Baker]

TruTrak uses a GPS track for its heading source under normal operations. At least this is the way it is for the Digiflight 2. There is a backup magnetic heading mode if the GPS source fails, but as long as the GPS is working it flies a GPS track on the heading selected.

 

I'm not going to try it, but I bet you would revese the aileron servo and set the airplane up flying backwards in a strong headwind and the AP would maintain your GPS heading while the aircraft is pointed 180° the oposite direction.

[gbigs]

My AP has a number of modes, some heading and some course.  I even have a heading bug and a course bug.  With my course bug the input is similar to heading but it tracks a course and compensates for changes in the wind.

 

 

The CRS function is used to dial in a VOR radial.  It will behave the same way as a HDG bug in NAV mode except it is used to track a radial on a VOR.  If there is wind the AP will still crab the course and radial to the VOR based on the CRS setting.  In other words, both CRS and HDG achieve the same thing in the same way.  There is no magic as you have noted CT in regard to wind.  The nose of the plane will point into the wind...but the ground track may be different dependent on ground track to the VOR or a LAT/LONG equivalent in a GPS waypoint.

[Ed Cesnalis]

The CRS function is used to dial in a VOR radial.  It will behave the same way as a HDG bug in NAV mode except it is used to track a radial on a VOR.  If there is wind the AP will still crab the course and radial to the VOR based on the CRS setting.  In other words, both CRS and HDG achieve the same thing in the same way.  There is no magic as you have noted CT in regard to wind.  The nose of the plane will point into the wind...but the ground track may be different dependent on ground track to the VOR or a LAT/LONG equivalent in a GPS waypoint.

 

You have learned well, I'm glad.

[Ed Cesnalis]

My TruTrak uses GPS heading for its reference.  What I am not sure of is whether it flies a heading (always pointed to the same heading) or a course (on a course line in the heading direction from the time you engage the heading mode).

 

The unit does say HDG mode.  But I can't remember is if once you roll a heading in if the display says CRS or HDG.  If it's actually flying a course when it says it's a heading, that could cause potential problems.  I tend to like a course better because it's more precise, but ATC and pilots need to be on the same page when they request us to fly a heading...

 

I'll have to do some testing on this with the TT to know the answer, unless somebody else has already tested this or knows the answer.

 

Such a test is tricky.  You need some shear to trigger a reaction and then determine if its reacting to a loss of course while on heading or a loss of heading while on course or a loss of both.

[gbigs]

You have learned well, I'm glad.

 

Instrument training.  And looking for the right answers, like the ones you put out.

[FlyingMonkey]

Such a test is tricky.  You need some shear to trigger a reaction and then determine if its reacting to a loss of course while on heading or a loss of heading while on course or a loss of both.

 

Agreed, conditions have to be right to test.  A steady track crosswind would be best to test.

 

BTW, I get confused by your apparent use of "shear" to mean "wind"...