Question for those using video cameras in planes

[vee1-rotate]

Question directed towards anyone using a video camera in a light aircraft.

I've successfully been able to connect up the audio from the headphone jack in the aircraft to the video camera in other aircraft, although 1 aircraft I'm currently flying (C172) has an issue, whereby when I plug in the single plug into the headphone jack on the aircraft, the whole comms in the aircraft get messed up (can barely hear transmissions from other aircraft, and can barely hear the intercom between passengers onboard). The comms all work fine if I pull the jack out, but with it in I can barely hear anything.

Has anyone dealt with this issue before, and found a fix? I've been able to successfully hook it up in other aircraft, its just this 1 aircraft I've come across the issue.

Any thoughts on what the issue could be or whats causing it?

Cheers

V1

[Peter Fanelli]

Now is this your own 172 or do those avionics you're screwing around with by plugging foreign stuff into it belong to someone else?

[vee1-rotate]

does that help answer my question, or...?

[Homesick-Angel]

Not....

I cant really answer it with any certainty(so please no flames),but having worked in music studios as an engineer Ive heard more than enough annoying noises to last a lifetime ..
Im sure you've already thought of or had a crack with some of these, but I would try.

a)plugging the other free hole with a spare headset jack

b)Try all coms plugs just to see it wasnt an isolated "dirty" pot although this seems unlikely due to the other issues.

c)Try using high quality 1/4 inch jack plugs(you'll find these at music stores that sell studio equipment possibly even JB.

d)borrow another camera and see if the problem is still there.

I have heard of certain headsets(with power) that cause a few problems in the com system, and possibly you are getting a similar issue..

All these are stabs in the dark, but maybe one will work for you?

Maybe your just freaking out the old bird with modern fandangled technology.

[YPJT]

One way I've seen that works well is a miniature microphone inside one of the headset cups direct to the camera .

[tail wheel]

Probably a microphone impedance mismatch. Talk to an avionics engineer about using an impedance matching transformer.

[john_tullamarine]

Similar thread (http://www.pprune.org/tech-log/413203-recording-intercom-radio-transmissions.html) on Tech Log recently - you might get some more words of wisdom there ?

[peuce]

You're taking a "line out" from the socket to the camera .... unfortunately, the socket is probably "speaker out" ... if it goes to headsets normally.

Some sort of adaptor/amplifier required.

[remoak]

Tailwheel had it half right - it is an impedance mis-match, but not with the microphone, with the differing impedances and signal levels of the headphone output.

An aviation headphone is relatively high impedance, most David Clark headsets run at 150 ohms, with some avionics systems designed for 600 ohm headsets (which is why you sometimes get problems running a DC headset with another brand in the same circuit).

Without getting too much into theory (which I don't remember anyway :O), your camera requires a line-level signal if using line in, or a mic-level signal if plugging in as an external mic. What you are effectively doing is shorting out the audio amplifier in your comms system, which is why everything goes quiet.

Does the Cessna have old ARC avionics? if so, that is probably your problem. From memory, You need a simple buffer circuit to match the impedances. Ask an avionics guy.

It's a long time since I had to solve this, so I could be completely wrong, depending on the effective impedance of your camera...

[Bell_Flyer]

The other way is to buy a condensor mike, plug it into the video cam and put the mike in your ear piece - or in a spare headset with the cups rubber banded together.

I do this quite a lot and it works a treat, from helo to fix wing, from noise cancelling to ordinary headsets. You hear everything very clearly.

[vee1-rotate]

Many thanks for all the suggestions and information guys, very helpful...will try and get it figured out going off your information

[JohnnyK]

Just as an aside and off topic. I am compelled to comment on P Fanelli`s post because it seems to me he represents a larger issue endemic in this industry of ours. I just gotta vent a little here.
Here we have a poster asking a perfectly legitimate question seeking a solution to a problem. All of a sudden out jumps Mr Fanelli like a little hitler-in-the-box all but accusing our man of vandalising somebody elses property. Please. Why man why?Do you exist in a permanent state of self righteous indignation?Or does pointing a finger and apportioning blame for no rational reason just make you feel happy? Help me understand because, in the words of the great Ferris Bueller"Understanding helps people like us tolerate people like yourself."
Sorry if you are actually a decent bloke and just having a bad day.But ,dammit, it sure has describes a few of the w:mad:ers I have had the misfortune of working alongside over the years.

[remoak]

Yes I suppose the other point worth mentioning is that nothing you could plug into the aircraft avionics could actually hurt anything... unless of course you are pumping (relatively) high voltages into them... and he isn't.

[harrowing]

Perhaps Mr Fanelli has a valid point.
Just because something is technically possible does not always mean it is legal or advisable.
Viewed in a slightly different light, consider that he was just advising a cautious approach, instead of diving in head first, and maybe displaying some wisdom gained from experience.
Two sides to every coin.

[VH-XXX]

Had a mate who bought a brand new R44. They hooked up a CD player to it at the dealer pre-delivery. It was wired incorrectly and didn't step down the voltage from speaker output to line-in. Subsequently fried the whole set-up with over $20k damage, including a GNS430 with damage. Ouch!

[ZEEBEE]

Mr. Fanelli has most definitely a valid point.

That the camera is causing the comms to go haywire suggests that an unapproved item is being used with aircraft Avionics that should not be tampered with.

If it is your aircraft, then it is merely a legal question of playing with something you're not licensed to do.

if it's someone else's, then apart from the legal question there is also the ethical one of perhaps damaging someone else's property.

And it may not become apparent right away, but the stressed output transistors may well fail while some other poor sod is out trying to contact ATC.

[Peter Fanelli]

And people wonder why it's getting harder and harder to hire good aircraft.
If I was to invest a 6 figure sum in an aircraft and make it available for other people to use I would certainly not be happy to find someone plugging anything other than an aviation headset into it.

[remoak]

Yeah well while I fully agree with looking after other people's property, some of the suggestions above are just ridiculous.

First if all, the avionics may require approval (well most of them), but you can plug whatever you like into them - the thing you plug in doesn't have to be approved. Show me anywhere in your aircraft's documentation where a specific headset is required, or conversely where another piece of equipment equipped with a 1/4 inch jack is prohibited.

And it may not become apparent right away, but the stressed output transistors may well fail while some other poor sod is out trying to contact ATC.

Complete nonsense. The "stressed output transistors" are part of the audio amp, and have nothing whatsoever to do with the transmitter section of the radio, other than being connected to it. There is no way on the planet that a failed audio output transistor could interfere with someone else's transmission... quite apart from the fact that pretty much every TSO'd radio has output transistors with full thermal and overload protection. And in any case, if those transistors were to fail despite the protection, they would almost certainly fail open-circuit (ie no output at all).

It was wired incorrectly and didn't step down the voltage from speaker output to line-in. Subsequently fried the whole set-up with over $20k damage, including a GNS430 with damage. Ouch!

The only thing it could POSSIBLY fry is the input section of the pre-amp, which in any case should be either fused or overload-protected. There simply isn't enough voltage coming out of a CD player to do that sort of damage. 20K? Don't think so. What was it plugged into? And unless it was plugged directly into the GNS430, there is no way it could damage that either. Sorry, but that story is highly unlikely. Show me the receipt for the repair and I might believe you...

[Peter Fanelli]

First if all, the avionics may require approval (well most of them), but you can plug whatever you like into them - the thing you plug in doesn't have to be approved. Show me anywhere in your aircraft's documentation where a specific headset is required, or conversely where another piece of equipment equipped with a 1/4 inch jack is prohibited.
What a weird attitude.....

"Thanks John for letting me hire your Malibu, by the way, I know you're not keen on it but there's no law which says I can't plug my __________ into the headphone jack, so I'm going to do it anyway and you can't stop me. After all, I'm paying to hire it so I'll do what I want with it"


Wanna bet?

It used to be so nice when there was quite a selection of 210s, Saratogas, Senecas, Bonanzas and yes, a Malibu readily available to people who could respect the owners property.

[TWT]

Ascertain the input/output impedances and AC audio levels of both the aircraft comms headset output and the video camera and then get an avionics engineer to specify a suitable audio isolation transformer and,if necessary,any resistive pads (attenuators).This means that there will be no direct connection between your camera and the aircraft comms system,so nothing can be short circuited or be damaged by DC volts anywhere.

Have the avionics engineer declare that the adaptor will not cause any unforeseen problems with the aircraft systems ( it shouldn't if designed properly) and ask the owner for permission before plugging in....

If all that is too hard/expensive/time consuming,then do as a previous poster suggested and just tape a lapel/lavalier mic onto an approved headset speaker and plug that into the camera.

[remoak]

"Thanks John for letting me hire your Malibu, by the way, I know you're not keen on it but there's no law which says I can't plug my __________ into the headphone jack, so I'm going to do it anyway and you can't stop me. After all, I'm paying to hire it so I'll do what I want with it"


Ok let's talk about weird (read "ignorant") attitudes...

First of all, if John had made it clear that he didn't want folk plugging anything other than a TSO's headset into his Malibu's avionics, no sensible person would do so. In this case, it has nothing to do with the law relating to certification, it has to do with whatever conditions the aircraft owner wants to impose as a condition of hire. Assuming the hirer is informed of those conditions, they form part of the contract with the owner (via an aero club or whatever) and ARE the law.

Secondly, if John wants to impose conditions of hire based on nothing more than misinformation, old wives tales and rumour, he is of course entitled to do so - but he is being somewhat stupid if he does, and only displaying his ignorance of his aircraft and it's systems.

When it comes to the risks of allowing your aircraft to be available for rental, what gets plugged into the headphone socket is a long way down the list of possible issues. Just make sure that you are properly insured and that your contract with the hirer is sensible, and the risk is minimal.

[Clearedtoreenter]

Sorry, but that story is highly unlikely. Show me the receipt for the repair and I might believe you...

Ha ha - can show you plenty of receipts from avionics guys for 'fixing' the 'highly unlikely'! ;)

[VH-XXX]

The only thing it could POSSIBLY fry is the input section of the pre-amp, which in any case should be either fused or overload-protected. There simply isn't enough voltage coming out of a CD player to do that sort of damage. 20K? Don't think so. What was it plugged into? And unless it was plugged directly into the GNS430, there is no way it could damage that either. Sorry, but that story is highly unlikely. Show me the receipt for the repair and I might believe you...

That is your choice not to believe this and honestly I don't care in the slightest that you don't believe it. If you want I'll give you the rego and the owners detail and I'll tell him in advance that some guy on pprune says that he didn't have to wait a few weeks extra for his new R44 and pay $20k to have his avionics and GNS430 repaired and that the avionics technician ripped him a new A-rsehole with the bill and while I'm there I'll let the avionics guy know too and he can call you. Whilst I'm at it I
might email Garmin for a copy of their repair invoice and component list and I'll CC the CEO of Heliflite just to keep him in the loop.

[remoak]

Feel free, the aviation world is full of apocryphal stories, particularly GA. Some of the nonsense spouted in this thread only underlines that.

[ZEEBEE]

Complete nonsense. The "stressed output transistors" are part of the audio amp, and have nothing whatsoever to do with the transmitter section of the radio, other than being connected to it. There is no way on the planet that a failed audio output transistor could interfere with someone else's transmission... quite apart from the fact that pretty much every TSO'd radio has output transistors with full thermal and overload protection. And in any case, if those transistors were to fail despite the protection, they would almost certainly fail open-circuit (ie no output at all).

Hmm! We're an avionics technician are we ?

Remoak, the failed output transistors would render the comms unservicable due to NO audio output.
If ya can't hear ATC then ya can't do much with them. Interference isn't the question.
So while it's true that the POH probably doesn't specify the exact type of headset, it does imply that the comms will be used as per the manufacturers specifications.
You will find a listing of impedance ranges there if you look.
Are you suggesting that you are free to plug in a shorting jack into a headset output ?

[Clearedtoreenter]

Thank goodness for Google - sorted that one out for me in .28 secs.:ok:

Meaning of apocryphal (adjective)
counterfeit; of doubtful authorship or authenticity

I could quite believe a guy got a bill for $24K ... and possibly didn't deserve one quite that big.

I speak from experience.. I have one for $10K myself for not fixing the 'fault' and then when a less apocryphal guy (is that right usage?) found the right fault it cost $180. So yes, I'd agree, we are probably reading some complete garbage from folk who reckon they know what they're on about. Problem is finding the ones who's work is most apocryphal. (Can I end a sentence with apocryphal? How do you say it btw? Great word, has lots of application in GA!)

[remoak]

Hmm! We're an avionics technician are we ?


No, I did a Diploma course in Sound Engineering, back in my rock music days. Covers most of this kind of stuff. Plus I have hand-built a number of amplifiers, transceivers and audio mixers over the years.

the failed output transistors would render the comms unservicable due to NO audio output.

Yes that is exactly what I said... :confused:

Are you suggesting that you are free to plug in a shorting jack into a headset output ?

Depends if you know whether it is shorting or not... but generally speaking, no. I can't see anyone here suggesting that you should... :confused:

I speak from experience.. I have one for $10K myself for not fixing the 'fault' and then when a less apocryphal guy (is that right usage?) found the right fault it cost $180.

I have had the same experience. It is normally because the technician doesn't want to fix the fault, he just wants to replace the board rather than identify and replace the component on the board that is actually faulty. Some won't even do that, they'll just send the whole box back and get an exchange one. That's when it starts costing big bucks...

[ZEEBEE]

my statement
the failed output transistors would render the comms unservicable due to NO audio output.
your response;
Yes that is exactly what I said...

Oook I'm glad we agree.:D

Would you then agree with me that if the said lack of audio output were to occur, the victim of the failed comms equipment might well be unable to communicate ???

That was my point....I thought I had made it pretty clear.

And it may not become apparent right away, but the stressed output transistors may well fail while some other poor sod is out trying to contact ATC

So if you're not an Avionics technician then you really have no legal business mucking around with the avionics of the aircraft.
Neither ethically or more importantly, legally.
Try putting your proposition to a CASA Field rep and see if you get a dissenting view.

[remoak]

And it may not become apparent right away, but the stressed output transistors may well fail while some other poor sod is out trying to contact ATC Your statement implies that someone OTHER than the victim of the failure may have issues communicating, which further implies that the failure causes interference when it happens. It is exceptionally unlikely to do so (although it is possible).

I'm having a little trouble understanding what your point is.

So if you're not an Avionics technician then you really have no legal business mucking around with the avionics of the aircraft.
Neither ethically or more importantly, legally.Sure. However, you don't seem to understand what that means. Legally, you can't interfere with the inner workings of your avionics, or the wiring that connects them to the aircraft electrical system or the aerials. However, where your avionics make available an external port (like a headphone or microphone socket), unless the radio station approval or the Flight Manual or the avionics manual specifically prohibits you from connecting equipment other than a standard headset, you are perfectly free to do so. Whether that is wise or not, is up to you. Some things in aviation really are up to you...

I'm not sure where ethics comes into it, I have never really investigated the morality of avionics usage, but yeah, whatever floats your boat...

[Peter Fanelli]

"And it may not become apparent right away, but the stressed output transistors may well fail while some other poor sod is out trying to contact ATC "


Your statement implies that someone OTHER than the victim of the failure may have issues communicating, which further implies that the failure causes interference when it happens. It is exceptionally unlikely to do so (although it is possible).

I'm having a little trouble understanding what your point is.

It's not rocket science, he's suggesting that the failure may occur when someone else, not involved with making videos for youtube, is using the same aircraft at a later time.

[remoak]

It may not be rocket science, but it is ambiguous (and based on a misunderstanding of how transistors work).

[Biggles78]

I would be more concerned with a pilot fiddling with the video camera when they should have their Mk1 Radar scanning instruments and outside the perspex. Passengers can shoot the video, pilots can fly the plane.

Using a mobile phone while driving is dangerous (even if you have a handsfree device), shoot video when flying is most likely even more so.

[OZBUSDRIVER]

Using a mobile phone while driving is dangerous (even if you have a handsfree device),

Unbelieveable! And what do you do if tower calls late final with your landing clearance?

Yes, some people are dangerous behind the wheel even attempting to have a conversation. Not a reason to blanket ban everyone...unless there is revenue to be made:E

[OZBUSDRIVER]

Simple description of the problem to be solved...Make the device so that all the comms system sees is the exact same impedance as a headset.

Best description for aviation comms...borrowed from old telephone technology. High impedance headsets and old carbon microphones. Modern gear still mimics these characteristics.

Try looking at a preamp for the lineout. Impedance to look for is about 150 to 300 Ohms.

Test the equipment using a handheld to ensure you will not fry aircraft equipment.

[ForkTailedDrKiller]

Using a mobile phone while driving is dangerous (even if you have a handsfree device), shoot video when flying is most likely even more so

Better tell the A380 drivers out there!

Dr :8

[Biggles78]

Unbelieveable! And what do you do if tower calls late final with your landing clearance?
Yes, a good point. I shall remember that next time I exit the roundabout, change lanes, merge into the traffic and line up on 05L. :*

[ZEEBEE]

It may not be rocket science, but it is ambiguous (and based on a misunderstanding of how transistors work).

Remoak

No ambiguity there...you f with the electronics....possibly stress the components and it fails when some other bod is flying the aircraft. doesn't get any simpler than that without resorting to pictures.

And you're telling me ????...

As one who has been working with transistors et al for approx 35 years both in the design and operation phases, it IS possible to fry output stages DESPITE overload protections etc etc.

[remoak]

Not with the output from a CD player it isn't. How does it magically bypass the input stages?