Any Aircraft Maintenance Engineers / A&Ps / Aircraft Technicians here?

Hello all!

I'm just a new recipient of an ICD and a having difficulty getting any detail about possible interfaces around heavy jet aircraft. I'm not planned to return to work for another 10 weeks or so, but am looking to see if there are any other AMEs, LAMEs, A&Ps etc in the club. Even the manufacturer Medtronic, admits they have very little detail about my work environment and effects it may have on the device. I asked about aircraft engine Generators, IDGs, VFSGs, TRUs, ATRUs, Static Inverters, High Power Conversion units, Transceivers and Receivers (Nav,Comm, VHF, HF, ATC, TCAS, LRRA, GPS, SATCOM Weather Radar), being near any of the antennas during receive or transmit times. 90 and 120 KVA GPUs. APUs and their Generators. Many of these items are up close and personal while in use.

Kinda, need to know before returning to work. For those who might be able to help, I'm talking about B737 right through to B787, and Airbus A320 right through to A350. So talking about both older radio and Nav Transceivers and antennas, as well as older 115VAC 400Htz and newer 230VAC variable frequency generation and well as their high power AC/DC and DC/AC conversions.

Any thoughts appreciated or other resources that you may know of.



by AgentX86 - 2023-06-11 23:55:33

I don't have any specific detail here but there are a few things here that would worry me.  I'm kinda a special case and my cardiologist is very conservative.  An automotive alternator is a problem for me.  Nothing else one would normally find around the home, though.

Welding is often a problem, also.  Usually 160A is the limit for welding. There are precautions even here.

I'd be worried about the APUs and high-power transmitters.  For OSHA reasons, I doubt maintenance personnel would be exposed to significant high-energy radio or RADAR signals but it could be a problem.


This why I need more detail

by Mike123 - 2023-06-12 02:52:18

I have read much of the published information. A 12 volt alternator at likely a max of 100 amps, is no where near what an aviation generator will produce. Also I think the ignitions systems my also be a problem when we are talking 60000 joules plus! 

But when considering these systems, are they safe if not in use? Example, can you replace the alternator, but just not be near it when it's running?

I also had question about a BMI body weight scale, which I'm told stay away from. The use about 800nano Amps of current, foot to foot. So I asked about my smart watch. The non-invasive blood glucose function that uses only out 60 nano Amps on the wrist to the second pickup on the same wrist. Was told by Medtronic's that shoul be ok! But still a bit concerned. 

Information just seems to be hard to come by!

Hard to come by

by AgentX86 - 2023-06-12 14:29:31

Information is hard to come by because there are so many variables, including lawyers trying to protect their clients from customers eating asteroids (don't take asteroids if you're allergic to them or any of their ingredients.)

In the case of alternators, motors, engines, and such, it's not the amps that's the problem.  It's the rotating magnet that's the problem.  The rotating magnet induces a current wires close to it.  That current can cause "underpacing" because the pacemaker thinks it's getting natural pacing signals from the heart.  It then inhibits its pacing, then there is no pacing going on. When the equipment isn't being used, of course there is no rotating field.

Yes, I'm "allowed" to work under the hood of a car if it's not running.  However, I'm not supposed to even ride a garden tractor because I'd be sitting rignt on top of the alternator.  Yard equipment (e.g. weed whackers) aren't a problem because they don't use alternators.  Their ignition system doesn't cause the same problems. The starter is the clue.

I may be a special case because I'm dependent, have no ventricular escape, and my LV lead is tip-to-can. That makes a relatively large loop.

That's the problem with welding, as well.  The cables and high current cause a large magnetic field.  An AC field can cause this under-sensing phenomenon. Medtronic says, less than 160A, keep the welding cables together and twist them to reduce the area of the "transmitting" antenna.  Also, place the ground clamp as close to the weld as possible.

It seems to me that the ignition system you're referring to would be less of a problem.  Pacemakers are well shielded against RFI. Energy isn't the problem.  It's the old it's volts that jolt but it's mills that kills. That said, RADAR would scare the crap out of me.  It wouldn't make me happy if they were burning holes in me, pacemaker or not. They're dangerous.

The BMI scales pass a current through your torso.  It's small, sure, but it's an overabundance of caution. TENS units on the torso are also discouraged.  TENS on the arms or legs isn't a problem because the current can't pass through the pacemaker (leads). This would be true of any such device, like your blood glucose meter.

Things that may affect your pacemaker

by Theknotguy - 2023-06-13 10:58:06

Being a newbie is really hard because there is so much misinformation out there that gets repeated over and over.  No one seems to check on the misinformation and no one challenges the statements.  As a newbie you really have problems sorting out the factual information from the fantasy. Add in people who like to tell scary stories and it's a mess.

I was told radio towers, TV towers, cell phone towers, magnets, store security systems, electricity and a host of other things would negatively affect my pacemaker.  What I found out was that, nope, the stuff doesn't affect my pacemaker in normal day-to-day functions.  

Radio towers, TV towers, Cell phone towers, - no effect.  Store security systems - no effect. 

Magnets - you can stop in at your local hospital, ask to see one of your pacemaker reps and they will tell you the magnetic gauss level that will affect your pacemaker and how close the magnet has to be to the pacemaker to affect it.  Personally I've been around the rare earth magnets - the kind you have to use a pry bar to pull  apart - within a foot and no effect on my pacemaker.  Will I put the rare earth magnet on my pacemaker? Absolutelyy not!  But I can be around the magnets with no problems. I have a pacemaker not an ICD.  Rules for ICD's are different.  I'm not talking about ICD's in this comment.

Had to jump start my daughter-in-law's car.  Forgot about my pacemaker and was leaning over the running engine.  No problem.  Don't do it on a regular basis but I'm not really worried about the generator/alternator.

I work in a woodshop. Was drilling pocket holes using a larger 110 volt drill. After about twenty or so holes got tired and started pushing the running drill in with my shoulder.  After about a hundred holes I finally remembered I had a pacemaker.  Had drilled over a hundred holes with my pacemaker being pushed up against a running 110 volt drill.   No problems. Try not to do that but every so often I forget and do it again.  While  I'll tell you not to do it, I'll also tell you not to be worried about it.

Son's garage door opener not working.  Asked him to turn off electricity.  Said he did. Grabbed a live 110 volt line.  It really woke me up.  Told my son he hadn't gotten the right line.  No problem with my pacemaker.  My son got a basic education in electrical circuits. I'll tell you not to do it, but I'm not worried about it.

We've had welders on the forum.  They usually show up ask questions, then disappear. Apparently they've figured something out that works.  Don't know what it is.

Circuit breaker boxes.  You can turn on and turn off circuit breakers.  No problem. And that also means you're within three feet of the box. No problem.

What has given me fits?  We need to trim wood pieces and sometimes use the Saws-all saws.  Heavy vibration.  Grabbed on of the saws and started pushing down hard.  Vibration went up my arm to my pacemaker.  The accelerometer in my pacemaker thought I was running and kicked my heart rate up.  What a rush.  I also ride in the big trucks and they bounce all over the place.  Pacemaker thinks I'm running and kicks up my heart rate. I have to reach over with my right hand and hold my pacemaker to keep it from bouncing. Drivers always tell me I don't have to give them a roman salute for their driving.  Wise guys...  I've also been on some buses. Diesel engine with a lot of vibration.  Same thing.  Have to hold my pacemaker. Otherwise no effect.  

The other thing that gives me problems is lifting heavy objects.  Pacemaker doesn't see the rise in blood pressure and the chest isn't moving so the pacemaker thinks I'm sitting in a chair. Doesn't compensate so after about five minutes I run out of air.  I have to go sit down and gasp for air until I'm back to normal.  I can life about three 55 pound 4x8 sheets and then I have to catch my breath.  No other effects. 

If you want to weight lift you can talk to your EP about adjusting your rate response to do that.  Guy at the hospital was bench pressing up to 300 pounds and finally broke a lead. Said he knew he was pushing it.  Did OK up to the 300 pounds.

I was working at this one place.  Back hall was 950 feet.  I'd walk the hall and run out of air at 900 feet.  Could point to the brick where I'd have to stop.  Talked to EP. Tests and they come to the conclusion I need to have rate response adjusted.  Most of his other pacemaker patients didn't do that much exercise so they hadn't adjusted my pacemaker for that level of activity.  Pacemaker rep went back to a day I was having problems. Pulled up the graph.  Said something about adjusting the what-ja-dinger and I've been OK ever since.

During your recovery period, and if you can, I'd go out to the repair area and watch one of your buddies do some work.  See if anything affects you.  Don't think it will but, at least, you'll know.  

Enjoy your new life with the pacemaker.  Be sure to keep your log books in order. My best wishes. 

may affect your pacemaker

by AgentX86 - 2023-06-13 17:16:20

Radio towers, TV towers, and all that are dangerous, with or without a pacemaker.  There is high energy radiation (often significan X-Rays as well)  in the vacinity of these things.  Indeed there are warning signs and interlocks on transmitter rooms because they will litterally fry you. A 100,000 watt (1MW ERP) transmitter is nothing to play around with. At some greater distance they will disturb any electronics, even with shielding.  The question is "how close".  Walking down the street? No.  In the transmitter "shack", quite likely so.

Much of this stuff doesn't have an answer, and can't have an answer, because there are too many variabes.  Store security systems, at one time, could have been problematic.  The manufacturers have reduced the power of these devices, and at the same time, pacemakers have become shielded better.  Bipolar pacing helps, too, but for various reasons not all pacemakers are set for bipolar pacing.

There is a lot of confusion around magnets.  Not all magnets are the same. Magnets, meaning permanent magnets, are used to set the PM to a diagnostic mode.  This turns off all optional features and returns the pacemaker to a base mode, like 60bpm AAI mode. Some will encode diagnostics (like battery condition) in the base heart rate.  An external permanent magnetic field may trigger this mode but if it does, there wouldn't likely be any consequences other than options would be turned off.

The ratings of pacemakers, and MRI machines, referrs to the fixed field strength, which is easy to measure and predict.  This is also why pacemakers are put in a "safe mode" during an MRI.  All features are turned off and the pacemaker put in a fixed mode.  A magnet over the device does the "same thing" but safing the pacemaker in an orderly fashion can allow more variation in the safing sate (AAI isn't going to help someone who needs VVI).

The problem arrises in AC fields, like transformer, motors, and generators/alternators. The field here is moving. It's not permanent.  A moving field induces a current in a conductor which can affect a pacemaker.  How much is impossibe to tell because there such a wide differenc in us, the pacemaker, and how the pacemaker was manufactured. If it happens, the result isn't so benign as putting the pacemaker into a safe mode.  It may trick the pacemaker into thinking that the heart is pacing itself so inhibits, resulting in no pacing at all. This isn't only way underpacing can occur.  There are warnings about radiation leaking from induction cooktops (only happens when a pot is placed off-center), welders, and other high-current devices.  The effect is proportional to the current (not voltage) in the loop (source of the current to the load and back around to the source) and the size/area of the loop. This is the reason welding cables should be run together and twisted.  It minimizes the area of the loop.

This is a complicated problem and it's not surprising that there is a lot of confusion. It's also not surprising the manufacturers are covering their backsides and overstating the possible problems. Why do you need to be told not to take a drug when you know you're allergic to it? A: Lawyers.


So I think without finding any A&P or AMEs with experience - the answer is coming together

by Mike123 - 2023-06-13 21:14:39

What I'm gleaning. Stay away from radio transmission like CB antennas. These tings pump out 4 watts, max 25W if in SSB mode. So and aircraft HF antenna, to which I would not get closer that 25 meters, but they can pump out up to 3000W. And VHF, to which I would easily and often be within inches of, pumps out between 25 and 200W. GPUs to power modern aircraft will be putting out up to 270KVA 3 phase AC, through cables that are not, and can no be twisted around each other. APU power supplying up to almost 500KVA, again through installed wiring I could easily be within inches of and are not twisted. Power conversion boxes changing this AC to other AC voltage, and to high power DC voltages, could be within inches. Dozens of Constant Speed Variable frequency AC high voltage, high speed motors running Air pumps, Fuel Pumps, Hydraulic pumps, coolant pumps, all of which are running and would be within feet. And to boot, in Aviation, we are very often in a work alone situation. Can't afford to pay 2 Engineers to to the job, where one will do!

Sounds to me like the Lawyers, especially for the work insurance cover would have a field day with all this!

Even to work out a risk mitigation plan seem like it would state do not go anywhere near then aircraft (unless you are sitting in the inside on holiday!) Not looking good for a return to work prospects - at least not as it has been, as I am very much a hands on, let me at it Engineer.

Could you ask your employer for environmental testing if they value you?

by Gemita - 2023-06-14 03:21:07

Mike, I expect one problem for you will be exposure to aircraft noise triggering tachycardia events, potentially leading to ICD shocks either appropriate or inappropriate.  Only by exposing yourself to all these hazards will you find out how you are going to be affected.  Would your employers be able to carry out environmental testing or hire a special engineer to do this to determine whether you are going to be safe to work in the environment again? 

I couldn't find much in the way of old posts about aircraft mechanics/engineers, but I attach a few links that might be worth reading which you will need to copy and paste into your main browser to open.  Member JWC might be worth private messaging (?if he is still around) for the results of his environmental testing (see particularly link 2) since there doesn't appear to be any follow up as he promised.  Anyway, hope for the best for you :-

Thanks Gemita

by Mike123 - 2023-06-14 04:09:57

Thanks for taking the time to comment and search for assistance. 

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