Autopilot Redundancy

[PTK]

I was told by Mrs. Brye, my very wonderful 6th grade teacher a long time ago that there is no such thing as a stupid question! So here we go:

Is it possible to have dual autopilots in our planes? Much like some turboprops and jets do? For example with my KFC 150, is it possible to have dual KC 192 computers? Not operating simultaneously but with pilot selection if one fails? We have dual Nav/Comms, dual ADI's and we're all about redundancy. So why not dual ap's?

[gsengle]

I was told by Mrs. Brye, my very wonderful 6th grade teacher a long time ago that there is no such thing as a stupid question! So here we go:
Is it possible to have dual autopilots in our planes? Much like some turboprops and jets do? For example with my KFC 150, is it possible to have dual KC 192 computers? Not operating simultaneously but with pilot selection if one fails? We have dual Nav/Comms, dual ADI's and we're all about redundancy. So why not dual ap's?

You’re the redundancy!


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[mike_elliott]

40 minutes ago, PTK said:

I was told by Mrs. Brye, my very wonderful 6th grade teacher a long time ago that there is no such thing as a stupid question! So here we go:

Is it possible to have dual autopilots in our planes? Much like some turboprops and jets do? For example with my KFC 150, is it possible to have dual KC 192 computers? Not operating simultaneously but with pilot selection if one fails? We have dual Nav/Comms, dual ADI's and we're all about redundancy. So why not dual ap's?

Peter, I would be more worried about that fine swiss watch KI256 than I would about the KC192. They like failing.

[PTK]

38 minutes ago, gsengle said:

You’re the redundancy!

 

Yes but that doesn’t answer my question.

Two pilots in the cockpit of a jet are double the redundancy but they have two and sometimes three autopilots. 

[gsxrpilot]

The situation in jets is a bit different in that it's very difficult/impossible to hand fly the jet with people walking up and down the aisles, drink carts, etc. Also, at least the jet's I fly on are typically in the air for more than 10 hours and sometimes close to 20. I'm pretty sure the only time the seat belt sign is off, is when the autopilot is on.

In our little planes a failed autopilot is just a minor inconvenience although expensive one. I'll bet it can be done, but I'll also bet no one has done an STC for such a configuration.

Personally, I wouldn't want the extra weight of a second autopilot.

[takair]

1 hour ago, PTK said:

I was told by Mrs. Brye, my very wonderful 6th grade teacher a long time ago that there is no such thing as a stupid question! So here we go:

Is it possible to have dual autopilots in our planes? Much like some turboprops and jets do? For example with my KFC 150, is it possible to have dual KC 192 computers? Not operating simultaneously but with pilot selection if one fails? We have dual Nav/Comms, dual ADI's and we're all about redundancy. So why not dual ap's?

The certification basis does not allow it.  I’m sure it could be developed, but very expensive and heavier.

[aviatoreb]

1 hour ago, PTK said:

I was told by Mrs. Brye, my very wonderful 6th grade teacher a long time ago that there is no such thing as a stupid question! So here we go:

Is it possible to have dual autopilots in our planes? Much like some turboprops and jets do? For example with my KFC 150, is it possible to have dual KC 192 computers? Not operating simultaneously but with pilot selection if one fails? We have dual Nav/Comms, dual ADI's and we're all about redundancy. So why not dual ap's?

I don't think its a dumb question.

But the answer is it does not exist.  And the certification process doesn't allow it since I think a second autopilot would need to be made to work in a slightly different location than the first and have a protocol of some sort so they can interact with each other properly.  But no one is doing such an STC.  So whether we like the idea or not its just not existing due to regulations.

I do agree that it seems less likely in our easy to fly small airplanes relative to the large very very difficult to fly big jets.

[MIm20c]

2 hours ago, mike_elliott said:

Peter, I would be more worried about that fine swiss watch KI256 than I would about the KC192. They like failing.

More importantly, they can fail in a way that can kill you. My IA has had multiple failures in which two resulted in large deflection changes during cruise. Could have been a real handful at minimums. 

My money would be spent on a new AP system that does not rely on the BK AI’s. 

[gsengle]

Yes but that doesn’t answer my question.
Two pilots in the cockpit of a jet are double the redundancy but they have two and sometimes three autopilots. 

I fly for a regional airline. As an FO one day, I was required crew, as the autopilot was deferred. (aka inop). My captain called OPS to try and swap into an airplane with a working autopilot as it was lousy weather all week. The response came back, you have an autopilot sitting next to you. It was a long week!


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[mike_elliott]

3 minutes ago, gsengle said:

 

I fly for a regional airline. As an FO one day, I was required crew, as the autopilot was deferred. (aka inop). My captain called OPS to try and swap into an airplane with a working autopilot as it was lousy weather all week. The response came back, you have an autopilot sitting next to you. It was a long week!


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remind me not to book on your airline....

[N201MKTurbo]

I don't see a technical reason, if you added duplicate servos. You could bridge the sensors and inputs without any problem.

The big problem would be coming up with some mechanism to make sure there was no way to turn them both on at the same time. They would likely fight with each other.

I think your chance of getting a field approval is zero. It would probably be cheaper to buy a turboprop with dual autopilots then getting an STC for it.

[PTK]

1 hour ago, N201MKTurbo said:

I don't see a technical reason, if you added duplicate servos. You could bridge the sensors and inputs without any problem.

The big problem would be coming up with some mechanism to make sure there was no way to turn them both on at the same time. They would likely fight with each other.

I think your chance of getting a field approval is zero. It would probably be cheaper to buy a turboprop with dual autopilots then getting an STC for it.

I'm not talking about dual servos. Only dual computers that would be switchable by the pilot. They would not be on at the same time. Only one at a time and when one is on the other is turned off.

[thinwing]

My only Autopilot failures have been Servo related..both on STEC and BK Autopilots...both resulted in U commanded spiral dives,one of which occurred over mountainous terrain and prompting ATC to query our flight status!

[N201MKTurbo]

25 minutes ago, PTK said:

I'm not talking about dual servos. Only dual computers that would be switchable by the pilot. They would not be on at the same time. Only one at a time and when one is on the other is turned off.

That would take a lot of switching relays and would leave the most failure prone components with no redundancy.

[gsengle]

remind me not to book on your airline....

 

And you call yourself a pilot...

 

If your crew can’t handle the airplane without an autopilot (like Korean Air in SFO) *then* you should be worried...

 

I was joking a bit, but honestly, if you aren’t proficient enough to in the unlikely event of an autopilot failure, to bring it home...

 

In fact we are required to have it off (powered down) for takeoff and then off when done using it on approach as a malfunction during a critical phase of flight is more risky than not using it in the first place.

 

 

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[mike_elliott]

And you call yourself a pilot...

If your crew can’t handle the airplane without an autopilot (like Korean Air in SFO) then you should be worried...


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Personal minimums are not to fly in a plane that is broken. I'll leave that to the time builders. I also choose not to fly with airlines that fly with broken planes. Its sad to hear you work for one of them. But I guess they help keep the NTSB well staffed.

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[gsengle]

Personal minimums are not to fly in a plane that is broken. I'll leave that to the time builders. I also choose not to fly with airlines that fly with broken planes. Its sad to hear you work for one of them. But I guess they help keep the NTSB well staffed.

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Airlines don’t fly broken. They use minimum equipment lists to defer non essential items. All the time. Safely.


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[jaylw314]

Just now, gsengle said:

 

 

Airlines don’t fly broken. They use minimum equipment lists to defer non essential items. All the time. Safely.


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Technically, if there is a MEL, that means they fly with something broken. 

[gsengle]

Technically, if there is a MEL, that means they fly with something broken. 

Name me an airline that doesn’t defer anything? Just one....

But I’d be happy to cancel your flight and leave you stranded for a burned out landing light for a day VFR flight if you like


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[jaylw314]

2 hours ago, gsengle said:

 

 

Name me an airline that doesn’t defer anything? Just one....

But I’d be happy to cancel your flight and leave you stranded for a burned out landing light for a day VFR flight if you like


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I know, I was just being a smart-ass

[Andy95W]

11 hours ago, gsengle said:

 

I fly for a regional airline. As an FO one day, I was required crew, as the autopilot was deferred. (aka inop). My captain called OPS to try and swap into an airplane with a working autopilot as it was lousy weather all week. The response came back, you have an autopilot sitting next to you. It was a long week!


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I've flown with a deferred autopilot, definitely not a fun day.  I also made sure that Dispatch and Maintenance Control knew that after 6 or 7 hours of duty time, we would be fatigued. If they wanted us to keep flying after that, they'd have to swap us into an airplane that had a working autopilot.  Guess what- they found us another airplane.

14 hour duty day, 7.5 hours flight time, 6 legs.  Makes me tired just thinking about having to do that again.

[gsengle]

I've flown with a deferred autopilot, definitely not a fun day.  I also made sure that Dispatch and Maintenance Control knew that after 6 or 7 hours of duty time, we would be fatigued. If they wanted us to keep flying after that, they'd have to swap us into an airplane that had a working autopilot.  Guess what- they found us another airplane.
14 hour duty day, 7.5 hours flight time, 6 legs.  Makes me tired just thinking about having to do that again.

Amen!


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[Yetti]

It would not be that hard to carry a spare unit and an allen wrench.   Slide one out slide the new one in.  No switching relays, no STC.   Mostly can be done by a pilot certificate.

[EricJ]

42 minutes ago, Yetti said:

It would not be that hard to carry a spare unit and an allen wrench.   Slide one out slide the new one in.  No switching relays, no STC.   Mostly can be done by a pilot certificate.

Radios, yes, autopilots, no.    Unfortunately those are excluded from owner maintenance.   Officially, anyway. 

 

[Jerry 5TJ]

1 hour ago, Yetti said:

It would not be that hard to carry a spare unit and an allen wrench.   Slide one out slide the new one in....

Several models of the panel mounted autopilot computers have a static port that must be unhooked behind the panel before sliding it out.  KFC150, for instance, requires some wrenching to disconnect the static line.  

The otherwise excellent KFC225 system tends to go through servos, not computers. Mine just blew a pitch servo last Saturday.   That servo had been replaced in 2014.   And several times before, too.  

At least the KS270 pitch servo can be removed without removing the pitch capstan and bridles.  If you happen to have a spare servo you can swap it out in about an hour.