Dan Bass saved my ass

[201er]

Picked up my 201 from maintenance, got a CO alarm on my sensorcon right on start up. I figured it might be blowing exhaust back in because I did start down wind of the exhaust. Opened some ventilation. Kept an eye on it during taxi and run up but the alarm was still blaring.

I figured the only way to find out if it’s ground CO or a leak is in the air. So, I took off around the pattern. Normally these ground CO alarms would reduce in climb and clear up once leveled off. It was 50-70 on the ground. Still 20+ on downwind so I turned back in and landed. Reported it to the mechanic and he tightened the exhaust bolts. Said one of them was a little loose. 

I think if it weren’t for Dan Bass, I probably still would not have gotten around to getting a detector and this would have gone unchecked! Thank you Dan and thank you Mooney Summit for the life saving discussion. Dan even recalibrated my sensorcon last Oshkosh. 

It’s all been false alarms up till now with ground exhaust blowing back in or being really close in formation. But this is the first time there was an actual problem and the detector was the only way to find it. They had replaced the muffler so I had a heightened awareness but without the detector there was no way of knowing it was actually leaking.
 

 

Edited May 20, 2020 by 201er

[PhateX1337]

Great report! How did you mount yours on the panel like that?

[carusoam]

Great pirep, Mikey!

Let’s see if @DanM20C is keeping count...

We need to celebrate with a social distanced Mooney fly-in!

Best regards,

-a-

[Ragsf15e]

I’ve got a sensorcon too.  After my last annual an exhaust riser “lost” all its washers/nuts.  It was completely unattached.  I finally got above 30ppm and got an alarm while taxiing in from a 1 hour flight.  Egt anomalies dowloaded from the jpi showed that the riser issue had started one or two flights after annual.  Maybe not tight like the OP?

Either way, it’s nice to have a good CO detector!

[Guest]

Does no one leak check their exhaust systems with a shop vacuum cleaner during annual or when working on exhaust systems?  It seems like a simple thing to do.

Clarence

[Ragsf15e]

37 minutes ago, M20Doc said:

Does no one leak check their exhaust systems with a shop vacuum cleaner during annual or when working on exhaust systems?  It seems like a simple thing to do.

Clarence

Doc, I wanna welcome you to the aviation maintenance jungle... if I could, I’d definitely bring my airplane to you.

[Guest]

7 hours ago, Ragsf15e said:

Doc, I wanna welcome you to the aviation maintenance jungle... if I could, I’d definitely bring my airplane to you.

While no maintainer or shop is perfect I often read these pages with amazement.

Clarence

[jetdriven]

20PPM isnt a concerning number, but a leak is a leak, and it could get worse.

[skydvrboy]

7 minutes ago, jetdriven said:

20PPM isnt a concerning number, but a leak is a leak, and it could get worse.

This is exactly why the Sensorcon is so valuable.  It tells you something is wrong... long before you have a problem!

[skydvrboy]

16 hours ago, PhateX1337 said:

Great report! How did you mount yours on the panel like that?

Not sure how Mike did his, but mine is attached to the panel with industrial hook and loop (Velcro).  I prefer that so I can remove it and take it with me if I'm flying in someone else's plane.

[EricJ]

Just now, skydvrboy said:

Not sure how Mike did his, but mine is attached to the panel with industrial hook and loop (Velcro).  I prefer that so I can remove it and take it with me if I'm flying in someone else's plane.

Same here.   Mine is where the MP gauge used to be. 

 

[gsxrpilot]

4 minutes ago, skydvrboy said:

I prefer that so I can remove it and take it with me if I'm flying in someone else's plane.

Always!

[Ragsf15e]

2 hours ago, skydvrboy said:

This is exactly why the Sensorcon is so valuable.  It tells you something is wrong... long before you have a problem!

Yep.  After using it every flight for a few months, I have a good idea what readings I should see on the ground, climbing, and cruise.  Typically I see ~10-15ppm during taxi depending on wind, door open/closed, etc.  After takeoff, I usually see less than 10ppm.  In cruise it’s 0.  Now when I saw 20 in cruise and 35 on the ground, I knew it wasn’t an emergency, but I also knew something was wrong.

It’s kind of like tracking oil use.  Mine is 4.5 hours/qt.  Maybe yours is 10.  Both acceptable, but if either one changes significantly, something isn’t right.

[1964-M20E]

Speaking of Sensrcon doesn't Mooney summit have a test kit?  I'm due for a calibration.

 

 

[Seth]

 

Good to hear Mike!  And good Dan for sharing your story with the world.  You have made a difference.

 

-Seth

[carusoam]

John,

I think there may be a couple of Sensorcon calibration sets...

Check with @mike_elliott... and @DanM20C 

Dan was carry his set with him...

This is as true as I can remember...   

Best regards,

-a-

[mike_elliott]

THe Mooney Summit no longer has theirs, it disappeared a couple of years ago. Dan has been bringing his personal testing setup to the Summit to calibrate the units for everyone. Thanks for reminding me Anthony, next Summit Ill see if I can get our team to approve getting another. The Summit is all about safety and this event of Mikes' just drives home the effectiveness. Glad to have this work out for you MIke!

 

[Jim Peace]

I run two of the sensors side by side.....you must check the checker......

I found a exhaust leak one day with the sensors......had some scat tubing detach under the cowl .........

[jetdriven]

To check it, either hold it behind your car ftet you start it up, or fire up your gas powered oven at home, and crack the door it goes ape sht in like two seconds. In both cases

[PT20J]

On 5/13/2020 at 7:35 PM, M20Doc said:

Does no one leak check their exhaust systems with a shop vacuum cleaner during annual or when working on exhaust systems?  It seems like a simple thing to do.

Clarence

That's a great idea, Clarence, and no, I don't think it's common practice (at least not in my experience). What I do know is that every year at annual we find a few exhaust and intake bolts that have lost their torque. There is a lot of info out there that split lockwashers don't do well in high vibration environments. I guess this maybe proves it.

Skip

[Ross Taylor]

I bought and mounted, with industrial Velcro, a CO Experts monitor. That damned thing does not have a programmable alert limit and I can't taxi without it blaring. There are two versions, one that alerts at 10ppm and one at 25ppm...ours is the 10ppm. It's so annoying that I moved the switch (that normally turns it on when it's slid into the mounting bracket) to the bottom of the case, so the toggle protrudes from the bottom. But, of course, if I forget to turn it on in-flight it does no good 

So, thanks for the multiple referrals here to the Sensorcon. I see that it's programmable...perfect. I'm ordering one in the morning and moving the CO Experts unit to our camper (where I can leave it on).

EDIT - in looking at the available models, it looks like the $159 Sensorcon PRO is the version with the adjustable trigger level.

 

[cliffy]

Split ? No!   I prefer internal star lock washers especially  on mags. I never loosen a mag nut without replacing the lock washer. 

[PT20J]

37 minutes ago, cliffy said:

Split ? No!   I prefer internal star lock washers especially  on mags. I never loosen a mag nut without replacing the lock washer. 

That’s great advice, and what Lycoming specifies. Unfortunately, tests show that star washers aren’t any better than splits under high vibration. There are a bunch of youtube videos and a NASA doc attesting to that. 

[cliffy]

44 minutes ago, PT20J said:

That’s great advice, and what Lycoming specifies. Unfortunately, tests show that star washers aren’t any better than splits under high vibration. There are a bunch of youtube videos and a NASA doc attesting to that. 

As we don't have anything else technically available that;s how I do it and I haven't had any problems with doing it that way.  I would like to read the NASA report and see the videos if you have a link

Is the NASA report specific to new unused lock washer ability?  Did they discuss what amplitude or frequency that the internal lock washers failed at?  I really would be interested in reading the report. I have no idea how to find it other than a basic Google search.

Do they offer any alternative way to fasten nuts? Perhaps we should look into that aspect. 

I still think a fool proof way to handle high vibration would be PAL nuts. We used them for decades. 

[cliffy]

"Tooth (or Star) Lockwashers Tooth Iockwashers (fig, 15) are used with screws and nuts for some spring action but mostly for locking action. The teeth are formed in a twisted configuration with sharp edges. One edge bites into the boltbead (or nut) while the other edge bites into the mating surface. Although this washer does provide some locking action, it damages the mating surfaces. These scratches can cause crack formation in highly stressed fasteners, in mating parts, or both, as well as increased corrosion susceptibility."

I found the above in a NASA "Fastener Design Manual"  NASA Reference Publication 1228

Is this the document you refereed to?

It does say that split washers have no locking properties but here on star washers it seems to indicate that there is some locking power BUT they do take exception to the damage the locking arms can do the the work pieces. 

In referring to "highly stressed" fasteners, I would think that our applications do not reach the "high stress" qualifier as say fasteners used in the rocket motors where the amplitude of vibration is WAY above anything our 1935 designed engines can produce. I can see where an engineer designing a rocket motor or space vehicle that will be untouched in space for decades may have issues with corrosion and fatigue cracking of bolts when the parts can't be looked at, once launched forever. 

You may have some info I have never seen. I'm not a PE by any means, just a long time wrench bender .