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Spent about 50 hours in the last couple of weeks flying this beautiful bird.

I am suffering with some autopilot problems.  This mostly occurs in turbulence (or should I say it is more accentuated).

When I run the final checks (just before establishing) I get a huge pitch up sometimes up to 30 degrees.  It seems to be worse when the aircraft is in a turn.  I will do more checking, but it seems to be around the time the gear is dropped.  At the time the aircraft is in altitude hold mode.

Also, the Approach mode doesn't seem to work.  It doesn't intercept the glide at all.  Sometimes it does pitch down, but nowhere near enough to follow the glide.  I don't mind this too much, after all, who wants an autopilot flying in CAT1 conditions when you can hone your own skills further by doing it yourself!

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Just completed flight check. Autopilot performs as expected for this vintage.

Autopilot has no problem adjusting to gear and flap extension, kept normal pitch values throughout. Turns had minor pitch deviations but nothing unusual. Appears to successfully track a localizer provided you capture it with the turn knob first (struggles with a 26kt direct crosswind 🙂). Glideslope coupling requires disengagement of altitude hold.

I highly suspect you had insufficient speed thus the pitch up as it tried to maintain altitude.

 

Robert Toten

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Speed was about 160 when it pitched up, Tried a few more tests.  It seems to be weather related.

I still can't get the Approach mode to work though.  I establish on the LOC, disengage the altitude hold and switch to Approach mode before the GS bar comes down, but nothing happens at first, the bar goes down and then it tries to react but never manages.

One thing I did notice, is if you then go back to LOC mode, the pitch is no longer controlled by the Autopilot, you can fly it with the yoke and trim.

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On ‎2‎/‎2‎/‎2019 at 7:47 AM, NeilC said:

This mostly occurs in turbulence (or should I say it is more accentuated).

The autopilots of this vintage tend to struggle in turbulence and are not very intuitive when it comes to the approach mode.  Although there is a LOC and APPROACH mode the autopilots of this generation were not capable and designed to fly precision approaches (my opinion).    When I fly the DC-6 I hand fly all departures and arrivals and only use the autopilot enroute.  

Grace and Peace, 

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4 hours ago, Bluestar said:

The autopilots of this vintage tend to struggle in turbulence and are not very intuitive when it comes to the approach mode.  Although there is a LOC and APPROACH mode the autopilots of this generation were not capable and designed to fly precision approaches (my opinion).    When I fly the DC-6 I hand fly all departures and arrivals and only use the autopilot enroute.  

Grace and Peace, 

However Wilhelm, the Sperry that is modeled in the DC-6 by PMDG is a very good autopilot.  We went through a lot of testing and tweaking during the P3D beta that I think resulted in a solid product.  This autopilot is the state of the 1950s art, sure it is full of tubes and transformers but just because an operational amplifier in a PID loop is a tube instead of a piece of silicon doesn't detract from it's capabilities.  Those engineers created a real work of art.

As for the complaint that GS is not being captured, I've been quiet because I haven't seen enough of an explanation of the problem to understand why it isn't working for the OP but I'm sure the problem is procedural.  I haven't flown the DC6 recently and when i do I also hand fly most of the time because it's fun (not because I need too), but last time I flew a coupled ILS she did exactly what was expected of her.

Edited by downscc

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2 hours ago, Bluestar said:

Although there is a LOC and APPROACH mode the autopilots of this generation were not capable and designed to fly precision approaches (my opinion).

It'll get you down to 200', wouldn't surprise me to learn it's CAT 1.

The other problem you might have Neil is that the autopilot has a maximum control authority of 18 degrees pitch below the horizon. If the combination weight/weather/speed/configuration requires more than 18 degrees nose down to follow a 3 degree slope then the airplane is going to fly high. If you work within it's limitations (and you PMDG guys did a fantastic job on this AP which I have never explored until now 😎) it'll achieve the required performance.

Neil try these conditions: 88,000 LBS, 2400 RPM, 24" minimum MAP, Gear DOWN, Flaps 30, 130 KIAS, Cowl Flaps 2, AUTO RICH. Remember that this AP cannot "capture" a GS, as soon as you command APPR and deselect ALT HLD it pitches for a GS wherever it is. Also it's a little slow (gives a smooth ride?), give it a chance to do it's thing.

 

Robert Toten

Edited by randomTOTEN

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DC-6 COUPLED APPROACH

I have never been able to do an autopilot coupled approach to minimums.  I have no trouble with the localizer, but when the aircraft descends through maybe 1000 ft, it decides to level off, or maybe even climb.  My actions are as follows: Flying along with autopilot, and altitude hold engaged.  Turn knob to select a heading approx. 30degs to the LLZ and positioned about four miles to glideslope capture.  Disconnect altitude hold and arm LOCALIZER.  When captured, engage APPROACH mode.  Aircraft tracking LLZ as glideslope needle starts to move down.  Glideslope captured and approach is exactly as it should be.  As mentioned before, it will continue like this until out of the blue it decides to level off or even climb.  Thankfully in my entire career as an airline pilot, I have never come across an aeroplane that does this.  What am I doing wrong?  PHIL MCCONNELL

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Around 130k - which seems to work, but it flies down from 3000 ft to about 1500 ft and then just levels off or climbs.  The model seems to have a very slippery grip of glideslope whilst localizer is perfect. I flew the DC-4 for four years, so I would like this to work.  Thanks,

Phil McConnell 

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Posted (edited)

Hi,

 

I have been having problems with pmdg s dc6 autopilot. I am flying VOR to VOR, without gps (bendix radios only). I set the VOR frequency and turn on localizer mode to intercept the radial. Problem is that the airplane does not follow the radial in straight line, it banks  left and right, although banking is very small but it does not seem to be right...has anyone had this problem or is this normal?

 

Thank you very much

 

Edited by MikeTheAviator
Mispeling

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4 hours ago, MikeTheAviator said:

has anyone had this problem or is this normal?

Using a weather add-on?

Also: keep in mind that the Sperry A-12 is from the days when autopilots were still novelties...like TVs at home.

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Posted (edited)
8 minutes ago, scandinavian13 said:

Using a weather add-on?

Also: keep in mind that the Sperry A-12 is from the days when autopilots were still novelties...like TVs at home.

I use fsuipc, the aicraft is flying an S shaped route, like always chasing the radial, flying over it, overshooting, and turning on to it again 

Edited by MikeTheAviator

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Posted (edited)

Thanks toten. The thing is that i am a real life profissional pilot and the a320 compensates for the wind when tracking a VOR course. The dc6 probably does not (old AP) and does not have an airdata computer to know wind speed and direction. I just wanted to make sure that it wasnt my simulator bugging. By the way you also experienced this?

 

Many thanks in advance

6 hours ago, randomTOTEN said:

Mike that sounds like normal behavior for VOR tracking.

 

Robert Toten

 

Edited by MikeTheAviator

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On 6/12/2019 at 8:21 PM, MikeTheAviator said:

and the a320 compensates for the wind when tracking a VOR course

Right, but it is from an entirely different era of technology.

On 6/12/2019 at 8:21 PM, MikeTheAviator said:

By the way you also experienced this?

I don't, but from what I remember, Opus causes some weird issues in the sim, wind-wise.

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There is absolutely no reason why the real aircraft wanders around a VOR track, unless the VOR is just about out of range.  The autopilot had 'Range Data Smoothing' in order to stop any wandering, and it did a good job.  As far as needing an FMS for wind speed, rubbish.  The VOR signal causes the aircraft to move further right or left the moment it starts to deviate from the centreline, and it doesn't care what the wind is, as long as it is not a rediculous speed.  Phil McConnell

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On 6/14/2019 at 3:18 PM, philfab2 said:

There is absolutely no reason why the real aircraft wanders around a VOR track, unless the VOR is just about out of range.  The autopilot had 'Range Data Smoothing' in order to stop any wandering, and it did a good job.  As far as needing an FMS for wind speed, rubbish.  The VOR signal causes the aircraft to move further right or left the moment it starts to deviate from the centreline, and it doesn't care what the wind is, as long as it is not a rediculous speed.  Phil McConnell

Ifigured that too. Probably a bug in my sim. I think this airplane is perfectly capable of dealing with a 40kt crosswind at cruise speed. 

I just think pmdgs products are too expensive to have these types of problems.

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9 hours ago, MikeTheAviator said:

I just think pmdgs products are too expensive to have these types of problems.

This is really, incredibly unfair.

While I understand that line of logic, it falls apart entirely when you go deeper than surface level.

 

I have a computer that I built at home for around $8000 - custom all of the things that I designed myself, purchased myself, put together myself, and maintain myself. I could knock over a $0 glass of water and cause all kinds of problems for an $8000 computer. Nothing is ever "too expensive" to have a simple problem, caused by an externality. We in aviation know this incredibly well as "pilot [or human] error." A 757 was brought down years back because someone put tape over a static port while washing it and forgot to take it off. All kinds of emergent technology, for a cool $65M, brought down by a piece of tape and the human condition (both forgetfulness and failing to piece together that the other guy's instruments were fine).

Similarly, you can take a free weather program that chucks all kinds of out of tolerance variables and have it cause aircraft to misbehave - doesn't matter if you downloaded it off of AVSIM as a free add-on, or paid $1000 for it. If the weather program is feeding the sim (and therefore the plane) bad data, there really isn't too much we can do. The more complex and realistic you make a plane, the more susceptible you make it to misbehaving when programs throw in bad data.

NOTE!

I am not saying "Opus is bad" or "all weather programs are bad" (in fact, my weather program of choice has a rep for causing all kinds of weird issues if you leave the turbulence scalar too high). I'm saying bad data can cause issues. Interestingly, turbulence isn't really modeled in the sim, in a natural way. In reality, it is more of a feeling than a visible thing. Since we can't "feel" the sim, MS took turbulence and made us "feel" it by using visuals, created by beating the plane around. Because a realistic amount of shake would be too subtle, they shake the plane around quite a lot. Weather add-on devs followed suit.

The result is something on the magnitude of 6+ g swings, in just about all directions. You really aren't going to find any APs out there that will handle that gracefully, while also being realistically precise. The additional problem is that this is made worse by the momentary nature of the spikes. Air is actually fluid in how it behaves (in the sense that we can use computational fluid dynamics to model it). Even when we have the most violent rotors (in standing mountain waves and other situations), you will never see that kind of swing. The magnitude of the swing might be that high, but it is not as violent/sudden, as the fluid of one "segment" of air will affect the other on its boundary, spreading it out over time.

...hell, a KAP150's default mode in NAV (VOR or GPS) is to hunt - forever - even in calm wind.

 

 

The solution is to provide the sim with realistic data. This is done by dialing down the turbulence that the weather add-on is injecting into the sim. If the expectation is realism, then realism should be expected on all fronts - to include the weather guys.

[Note: This is shown visually/graphically in a test we conducted in our 777 Intro document, and later in the 747 docs, if you have either of those products.]

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4 hours ago, scandinavian13 said:

This is really, incredibly unfair.

While I understand that line of logic, it falls apart entirely when you go deeper than surface level.

 

I have a computer that I built at home for around $8000 - custom all of the things that I designed myself, purchased myself, put together myself, and maintain myself. I could knock over a $0 glass of water and cause all kinds of problems for an $8000 computer. Nothing is ever "too expensive" to have a simple problem, caused by an externality. We in aviation know this incredibly well as "pilot [or human] error." A 757 was brought down years back because someone put tape over a static port while washing it and forgot to take it off. All kinds of emergent technology, for a cool $65M, brought down by a piece of tape and the human condition (both forgetfulness and failing to piece together that the other guy's instruments were fine).

Similarly, you can take a free weather program that chucks all kinds of out of tolerance variables and have it cause aircraft to misbehave - doesn't matter if you downloaded it off of AVSIM as a free add-on, or paid $1000 for it. If the weather program is feeding the sim (and therefore the plane) bad data, there really isn't too much we can do. The more complex and realistic you make a plane, the more susceptible you make it to misbehaving when programs throw in bad data.

NOTE!

I am not saying "Opus is bad" or "all weather programs are bad" (in fact, my weather program of choice has a rep for causing all kinds of weird issues if you leave the turbulence scalar too high). I'm saying bad data can cause issues. Interestingly, turbulence isn't really modeled in the sim, in a natural way. In reality, it is more of a feeling than a visible thing. Since we can't "feel" the sim, MS took turbulence and made us "feel" it by using visuals, created by beating the plane around. Because a realistic amount of shake would be too subtle, they shake the plane around quite a lot. Weather add-on devs followed suit.

The result is something on the magnitude of 6+ g swings, in just about all directions. You really aren't going to find any APs out there that will handle that gracefully, while also being realistically precise. The additional problem is that this is made worse by the momentary nature of the spikes. Air is actually fluid in how it behaves (in the sense that we can use computational fluid dynamics to model it). Even when we have the most violent rotors (in standing mountain waves and other situations), you will never see that kind of swing. The magnitude of the swing might be that high, but it is not as violent/sudden, as the fluid of one "segment" of air will affect the other on its boundary, spreading it out over time.

...hell, a KAP150's default mode in NAV (VOR or GPS) is to hunt - forever - even in calm wind.

 

 

The solution is to provide the sim with realistic data. This is done by dialing down the turbulence that the weather add-on is injecting into the sim. If the expectation is realism, then realism should be expected on all fronts - to include the weather guys.

[Note: This is shown visually/graphically in a test we conducted in our 777 Intro document, and later in the 747 docs, if you have either of those products.]

Whereas with the gps it flies perfectly straight

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I fly the PMDG C-118 and have no trouble tracking a VOR radial.  Once on track, it stays there.  In fact, I flew thru a Active Sky 2016 generated thunderstorm between Pendleton, Oregon and Baker, Oregon and the AP continued to track properly even though the plane was being tossed all over the place.  In the real world, a 180° turn would have been in order but the Active Sky alert arrived after I had started my penetration.  

The only problem I have with the VOR is trying to figure out which course heading to fly, the one shown on the flight plan generated by FlightSim Commander, PFPX, FSTramp or the actual Sectional chart.  In any event, what ever course finally ends up at the VOR.

Jim Driskell

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3 hours ago, MikeTheAviator said:

Scandinavian, i did not mear to offend anyone at pmdg. I tried with opus turned off and i still get the aircraft wandering arround the radial

 

7 hours ago, scandinavian13 said:

This is really, incredibly unfair.

While I understand that line of logic, it falls apart entirely when you go deeper than surface level.

 

I have a computer that I built at home for around $8000 - custom all of the things that I designed myself, purchased myself, put together myself, and maintain myself. I could knock over a $0 glass of water and cause all kinds of problems for an $8000 computer. Nothing is ever "too expensive" to have a simple problem, caused by an externality. We in aviation know this incredibly well as "pilot [or human] error." A 757 was brought down years back because someone put tape over a static port while washing it and forgot to take it off. All kinds of emergent technology, for a cool $65M, brought down by a piece of tape and the human condition (both forgetfulness and failing to piece together that the other guy's instruments were fine).

Similarly, you can take a free weather program that chucks all kinds of out of tolerance variables and have it cause aircraft to misbehave - doesn't matter if you downloaded it off of AVSIM as a free add-on, or paid $1000 for it. If the weather program is feeding the sim (and therefore the plane) bad data, there really isn't too much we can do. The more complex and realistic you make a plane, the more susceptible you make it to misbehaving when programs throw in bad data.

NOTE!

I am not saying "Opus is bad" or "all weather programs are bad" (in fact, my weather program of choice has a rep for causing all kinds of weird issues if you leave the turbulence scalar too high). I'm saying bad data can cause issues. Interestingly, turbulence isn't really modeled in the sim, in a natural way. In reality, it is more of a feeling than a visible thing. Since we can't "feel" the sim, MS took turbulence and made us "feel" it by using visuals, created by beating the plane around. Because a realistic amount of shake would be too subtle, they shake the plane around quite a lot. Weather add-on devs followed suit.

The result is something on the magnitude of 6+ g swings, in just about all directions. You really aren't going to find any APs out there that will handle that gracefully, while also being realistically precise. The additional problem is that this is made worse by the momentary nature of the spikes. Air is actually fluid in how it behaves (in the sense that we can use computational fluid dynamics to model it). Even when we have the most violent rotors (in standing mountain waves and other situations), you will never see that kind of swing. The magnitude of the swing might be that high, but it is not as violent/sudden, as the fluid of one "segment" of air will affect the other on its boundary, spreading it out over time.

...hell, a KAP150's default mode in NAV (VOR or GPS) is to hunt - forever - even in calm wind.

 

 

The solution is to provide the sim with realistic data. This is done by dialing down the turbulence that the weather add-on is injecting into the sim. If the expectation is realism, then realism should be expected on all fronts - to include the weather guys.

[Note: This is shown visually/graphically in a test we conducted in our 777 Intro document, and later in the 747 docs, if you have either of those products.]

Found this in an autopilot forum.

Can this be the explanation? Please if anyone notices this “s-shaped” behavior while tracking a vor radial with the dc6 let me know.

 

here it goes 

Autopilots have been around for a while now.  Amazingly, the first aircraft autopilot was developed by Sperry Corporation in 1912!  I seem to have missed the hundreth birthday of the autopilot somehow.
Two decades ago the autopilots on most airplanes still weren't all that hot. They could hold a heading and altitude pretty good, and track an ILS when things were tight. Tracking a VOR radial was like doing S-turns down the airway. The button for airspeed/mach hold looked better than it worked”

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Kyle, my bad and for that i apologize. It Was becoming so  frustrating because i really love the aircraft and studied it so deeply 

 

apparently i needed to update my dc6 via OC. Testing now. So far so good.

 

Mike Simms

 

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