AD 76-07-12 question

[sleeper-319]

I’ve read the AD, and several threads here (like this one), and am still uncertain whether the applies to my specific aircraft’s switch. The IA that did my most recent annual flagged this as recurring (it wasn’t before). I’m not worried about compliance (it was inspected and passed); just trying to be diligent with records. 

The AD mentions: “Applies to all aircraft employing magnetos and using Bendix ignition switches listed in the table below except switches identified by four digit date code (new) adjacent to the model number or a white dot (modified) on the support plate adjacent to the Bendix logo.”

My switch has some white paint near the Bendix logo on the back, and it is the superseding part number in SB-583.  However it’s not clear to me which number is the date code. Because the number wraps around the switch, it’s hard to get a pic with the entire number in view. But it has 3 lines that read: 

• 10-357210-9 A1
• 8642
• FAA PMA

So… any ideas? Does this actually apply to my switch? Is the white smudge a “white dot?“ Is the 8642 a date code? And why does the 2 look so janky?  I appreciate any help y’all got. 

[MikeOH]

This is such a simple check that I perform it every flight before shutdown.  How much is the A&P charging you to test and document? I'd hope it was just included in the basic annual inspection.

I was ridiculed for doing this every flight...until one day the engine just kept running!  Turns out it wan't the mag switch but the p-lead had frayed and failed. Seems a no cost way to mitigate a potentially fatal risk.

[sleeper-319]

Thanks MikeOH, I tried in the original post to to make it clear I was looking for applicability information. I'm aware it's an easy check, and my A&P is awesome. But that's not why I posted. :-)

[MikeOH]

4 minutes ago, sleeper-319 said:

Thanks MikeOH, I tried in the original post to to make it clear I was looking for applicability information. I'm aware it's an easy check, and my A&P is awesome. But that's not why I posted. :-)

Yeah, I got that.  

I just don't understand why you care so much unless you want to get rid of this recurring AD.  I think that's a bad idea; what happened to me is pretty convincing evidence as to why.

So,

1) The 8642 is the 4 digit date code and being located directly below the model you can argue that it is, in fact, "next to the model"

2) Argue that the 'white smudge' is really the white dot

The next A&P may not be so easily convinced and will spend 10 seconds checking it anyway.

[sleeper-319]

Thanks for the added info.

8 minutes ago, MikeOH said:

1) The 8642 is the 4 digit date code and being located directly below the model you can argue that it is, in fact, "next to the model"

 

[N201MKTurbo]

8642 means week 42 of 1986. If it hasn’t failed yer, it isn’t going to. BTW, if you take it apart and clean it and polish the contacts and sliders and reassemble it with DC4, it will be good for another 38 years.

I just did this on my 1956 Cessna. It should be serviced again in 2090…

[OR75]

On 1/15/2024 at 8:07 PM, MikeOH said:

Yeah, I got that.  

I just don't understand why you care so much unless you want to get rid of this recurring AD.  I think that's a bad idea; what happened to me is pretty convincing evidence as to why.

So,

1) The 8642 is the 4 digit date code and being located directly below the model you can argue that it is, in fact, "next to the model"

2) Argue that the 'white smudge' is really the white dot

The next A&P may not be so easily convinced and will spend 10 seconds checking it anyway.

i had that same thought as the OP a few years back.

Totally agree that checking the mags and the switch  is fast, easy and a great idea. (I am actually one of those who once in a while checks mags in flight (always above or very close to an airport just like when i switch tanks) 

But i would not want to have in the logs a multitude of references to ADs that do not apply.  Referencing an AD once and stating that it does not apply would be OK if the AD is related to my airframe or installed appliances.

[MikeOH]

7 hours ago, OR75 said:

But i would not want to have in the logs a multitude of references to ADs that do not apply.  Referencing an AD once and stating that it does not apply would be OK if the AD is related to my airframe or installed appliances.

That makes a lot of sense.

My concern is that if you are not the type to check the mags for grounding periodically, having this AD active would at least have the check performed once a year by the A&P.  And, as my experience demonstrates, you are checking the whole grounding system, not just the mags.

Knowing that the mags are dead when you shut down is great peace of mind even if you are not one to move the prop.  Parked on a ramp somewhere...I'd feel terrible if someone was injured if they, for whatever reason, moved my prop and it fired!  It's truly a failure mode that will go completely undetected.

[A64Pilot]

So far as checking for a broken mag lead, you do that at every mag check, if you get no drop on one mag, don’t be pleased, be suspicious.

I often check mine too, not every flight just randomly. I check by turning the mags off at idle. You don’t have to kill an engine by running it out of fuel, it doesn’t hurt to turn one off by removing the spark.

I’m a little hesitant to go off and back on, because I’ve seen exhausts damaged by a back fire, actually an after fire but that’s being pedantic, most call it a back fire.

[Kelpro999]

1 hour ago, A64Pilot said:

 

I’m a little hesitant to go off and back on, because I’ve seen exhausts damaged by a back fire, actually an after fire but that’s being pedantic, most call it a back fire.

The concern is very real with me after being brought down by a damaged muffler descending west into San Diego. I did make a runway but preparing to set down on a mountain highway for 20 minutes was extremely stressful. 
  That followed a loud start up backfire in Yuma az.

Edited January 19, 2024 by Kelpro999

[Will.iam]

Well checking the mags does not check past both in the off position. We pull the mixture then turn off the mags presumably to remove the fuel from entering the cylinders when the moter is winging down but when the motor sets for the next 15 to 20 mins the heat from the motor causes fuel to leak in from heat expansion anyways as proof from the hot starts the engine will fire up with the mixture in cutoff when the motor is still hot. When i know i am going to be starting my motor hot like when stopping at the fuel pump to pump in some gas, i shut down the motor with the ignition only. Once it stops i know the mags are both indeed grounded and any unburnt fuel in the exhaust from idling speed will have evaporated in the time it takes me to full up the tanks. Then on next startup i have the mixture in cutoff  when i engage the starter. The moment the engine catches i go full rich on the mixture and off i go. Only if i go use the restroom get something to eat etc and it’s pushing an hour or more when i start the engine and it starts to die i might have to hit the prime button for a 2 sec burst to keep the engine from quitting but then it’s fine after that.