Unknown origin of part of AP system on a Chieftain

Michael95U

Michael95U

Well-Known Member
One of the Chieftains we operate has been on Part 135 certificates for its entire life. We have had it for three years and it has passed numerous conformity inspections.

Recently, an avionics shop pointed out a little used part of our autopilot (Altimatic X):

It is a switch to the right of the co-pilot instrumentation (with a corresponding Blue light) that allows the co-pilot to switch autopilot input from the pilot side HSI to the co-pilot HSI.

The problem? We can't find who installed it, when it was installed, or if it is even a legal add-on. The number of relays and age of said relays tells us this was installed AGES ago. It is clearly an aftermarket add-on.

Does this capability ring a bell? Has anyone seen it on another altimatic X equipped aircraft? Any idea on flight manual supplements, if it was an STC, or general point in the right direction?

Thanks!

Michael
 
I don't see why you would need an STC for that. Doesn't seem to me to fit any of the major alteration criteria. Switching and relays like that are pretty common in that level of avionics install. You may even have another one that switches the HSI between nav 1 and nav 2. I really would not worry myself about it.
 
Michael95U said:
We are looking for a flight supplement that shows how to use it
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Not to be a jerk, but do you need a flight manual supplement to show how to use all the other switches on the panel too? From your description it sounds pretty straightforward.

If you have an FAA inspector that's riding your butt about it, throw money at the avionics shop and tell them to get with the FSDO avionics/mx folks and do whatever paperwork they need to to make the Feds happy.
 
Roger Roger said:
Not to be a jerk, but do you need a flight manual supplement to show how to use all the other switches on the panel too? From your description it sounds pretty straightforward.

If you have an FAA inspector that's riding your butt about it, throw money at the avionics shop and tell them to get with the FSDO avionics/mx folks and do whatever paperwork they need to to make the Feds happy.
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Trust me, I know where you are coming from. Here is the quick timeline:

1) Airplane comes in for Annual
2) Avionics shop does their required checks. The head avionics guy says, "I have never seen that before in my life. Is that aftermarket or original?"
3) My DOM talks to two FSDO's who tell him he needs to know if there is any scheduled mtx involved with this part of the system
4) Lo and behold, we can find no record of its install (unless it was part of the since-removed Loran system, though it has no Loran function), nor do we know if it is a part of the Altimatic X or some jerry-rigged system.
5) FAA ops guy says, "well, if there isn't a part of the AP AFM supplement dedicated to this function, how do you train your pilots to use it?"

Soooo. Just trying to cover proverbial asses here.

And all because a little avionics guy went Ka'choo.....
 
Ahh, tis as I suspected...dumb Feds involved. There is no requirement for ICAs to be provided for non-major alterations, so a simple "does it work? Yes/no" test should be sufficient in that regard. To keep the ops folks happy you could write a one-sentence blurb about how it works and tack it to the autopilot supplement. If they're really on a rampage and insist that it's a major alteration or some crap like that like Feds are wont to do I'd just pay the avionics folks to reverse engineer it (should be easy if it is working and if they can find pinouts for the relays), prepare a 337 with a 1-page ICA and a 1-page flight manual supplement, and seek a field approval.

Why your DOM even thought about bringing this to the attention of the Feds...
 
He didn't really bring it to their attention. He asked the advice of a neighboring FSDO without mentioning company name or N-number. But he is in "cover his ass" mode and that doesn't bode well for flying airplanes sometimes. This is one of those things that just drives me nuts as a pilot. I have 300 damn hours in that plane and never used that switch (we haven't operated with SICs), it's been in the plane for years, and no one has said anything during that time.
 
Did you guys know about the switch and what it did prior to the inspection?
 
Michael95U said:
I can speak for the pilots and state a resounding "yes".

The DOM is new to our operation and so was the avionics shop.
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Good to hear. I was just imagining situations when that switch gets but in the wrong position for whatever reason and a pilot not understanding why the auto pilot is acting funny. In the helicopter I fly we have a button that does sort of the same thing (slaves nav and processed data to one HSI or the other). Our pilots get oodles of training on it and it's discussed at length in our manuals. I still see my pilots screw it up though and forget to bring the data to their side.
 
Roger Roger said:
Not to be a jerk, but do you need a flight manual supplement to show how to use all the other switches on the panel too? From your description it sounds pretty straightforward.

If you have an FAA inspector that's riding your butt about it, throw money at the avionics shop and tell them to get with the FSDO avionics/mx folks and do whatever paperwork they need to to make the Feds happy.
Click to expand...

A pilot not knowing about this could get themselves killed pretty easily if they're flying multiple aircraft on a regular basis that don't have this function. And if you're single pilot in the left seat, and can't see where that switch is on the right, you could be coupled to the writ side without realizing it.

In my current plane, the designation for which side you're coupled to is top and center on the pfd, because this is incredibly important. Additionally, our hsi needles change color depending on what source we're pulling from.
 
Roger Roger said:
Ahh, tis as I suspected...dumb Feds involved. There is no requirement for ICAs to be provided for non-major alterations, so a simple "does it work? Yes/no" test should be sufficient in that regard. To keep the ops folks happy you could write a one-sentence blurb about how it works and tack it to the autopilot supplement. If they're really on a rampage and insist that it's a major alteration or some crap like that like Feds are wont to do I'd just pay the avionics folks to reverse engineer it (should be easy if it is working and if they can find pinouts for the relays), prepare a 337 with a 1-page ICA and a 1-page flight manual supplement, and seek a field approval.

Why your DOM even thought about bringing this to the attention of the Feds...
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"Continued Airworthiness limited to parts replacement only" is what I have used in the past.
 
Michael95U said:
He didn't really bring it to their attention. He asked the advice of a neighboring FSDO without mentioning company name or N-number. But he is in "cover his ass" mode and that doesn't bode well for flying airplanes sometimes. This is one of those things that just drives me nuts as a pilot. I have 300 damn hours in that plane and never used that switch (we haven't operated with SICs), it's been in the plane for years, and no one has said anything during that time.
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Just be patient and get it sorted out. "No one found it before me" is not a valid defense, especially if you're a mechanic.
 
jtrain609 said:
A pilot not knowing about this could get themselves killed pretty easily if they're flying multiple aircraft on a regular basis that don't have this function. And if you're single pilot in the left seat, and can't see where that switch is on the right, you could be coupled to the writ side without realizing it.

In my current plane, the designation for which side you're coupled to is top and center on the pfd, because this is incredibly important. Additionally, our hsi needles change color depending on what source we're pulling from.
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I don't see it. There is an off button to the AP. Very simple fix.

If you can't figure it out, hand fly the thing and deal with it on the ground. Not a big deal at all. If you get killed in a chieftain because you let the autopilot determine where you go then you had some problems with airmanship to begin with.

I have had several APs go crazy on me. The answer every time was to hit the purty red button on the yoke and hand fly.
 
Maurus said:
I don't see it. There is an off button to the AP. Very simple fix.

If you can't figure it out, hand fly the thing and deal with it on the ground. Not a big deal at all. If you get killed in a chieftain because you let the autopilot determine where you go then you had some problems with airmanship to begin with.

I have had several APs go crazy on me. The answer every time was to hit the purty red button on the yoke and hand fly.
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Nifty, but the suicide switches (NAV/GNSS, AP TRANS, etc.) are very big deals, and need to be clearly labelled and their functions well documented, regardless of the availability of a quick disconnect...
 
I don't understand the AP transfer being considered a suicide switch. I know the others are very important and never said they weren't, but if you can't hand fly the airplane when the AP acts up then you shouldn't fly. Simple as that. If you fly into something because the AP went straight instead of where you put the heading bug then there are some major issues with the person at the controls.

I just say take the switch out, or deal with the stupid squawks that may result.
 
Maurus said:
I don't understand the AP transfer being considered a suicide switch. I know the others are very important and never said they weren't, but if you can't hand fly the airplane when the AP acts up then you shouldn't fly. Simple as that. If you fly into something because the AP went straight instead of where you put the heading bug then there are some major issues with the person at the controls.

I just say take the switch out, or deal with the stupid squawks that may result.
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Excessive distraction divides attention and is deadly.
 
Autothrust Blue said:
Which is why those switches are called suicide switches.
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We regularly have our AP decide to not go where it's supposed to or not capture something.
It goes like this - Ah the AP found that bottle of whiskey I hid for later. Damn... well you can go home now, I'll fly.
And just like that we don't die.
Unless you're sleeping up front you should notice it doing things wrong.
 
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