Lucky

TangoWhiskey

Touchdown! Greaser!
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Feb 23, 2005
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Midlothian, TX
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3Green
Lucky? Yes, lucky that I didn't have an engine compartment fire in flight, with my wife on board. And while I tend to think of myself as a "cautious and careful" pilot, I missed (and dismissed) two clues that could have stopped the chain. That's why I'm writing this story.

Returning to Fort Worth (T67 / Hicks) from a two week trip to New Smyrna Beach ( KEVB ), my wife and I planned a stop in Meridian, MS (KMEI), for a lunch snack and fuel. Meridian is well known in the area for affordable gas, free hot dogs, pizza and popcorn. We filed IFR, and after a quick hop up on top of a 500' OVC, but thin, fog layer in New Smyrna Beach, we were on our way in our 1980 TR182. While we'd flown high eastbound to Florida, on the return trip we stayed low, at 8000', due to the strong westerlies. This ended up being, I think, a "good thing."

After our one hour stop in Meridian, we saddle up and got ready to go. We use a Mountain High O2D2 pulse-delivery system connected to our shipboard oxygen system, and wear it on most long flights at 8000' or above--we seem to arrive fresher and with no headache that way. Pre-engine start, we donned our cannulas, put on our headsets, opened the O2 valve and set the O2D2 unit for D5, as usual. After engine start and avionics on, I remarked to my wife that the engine seemed a little "louder" than normal. She agreed. It almost sounded like we didn't have ANR activated on our Lightspeed Zulu 2's, so we checked that, but indeed it was on. Turning ANR off made it get louder, ANR on was not as loud, but definitely louder than "normal". Not a grinding or metallic sound--just sounded like we had another 300HP! :) Maybe I was dreaming of flying a twin? In any case, after a check of the engine instruments and such (all normal), we decided to go do a thorough runup before departing on our final leg home.

We picked up our IFR clearance and taxied from the FBO's ramp via taxiway Bravo to the run-up area for Runway 4. We did an especially careful and thorough (and longer than normal) runup, double checking our headsets. The engine still seemed loud, but we noticed that when we pushed the earseals in (like pushing on your head when you have a migraine), the sound did get "normal". So, we both wrote it off as a bad ear seal due to the O2 hoses, or some other ANR issue.

On the roll for departure, it took a lot of willpower (and in retrospect, stupidity) to ignore the louder-than-normal sounding engine, but everything was in the green, no issues at all. We climbed direct to 8000 and proceeded 2 hr. 45 minutes home to Fort Worth.

About 30 minutes into our 2 hr 45 minute flight, during a routine scan my eyes alighted on the yellow, green and blue Quantum Eye CO detector I have mounted on the panel (as so many of us do). The dot was dark. Hmmmmmm. That's got my attention!

I have a ultra-sensitive CO Experts Carbon Monoxide detector unit on board, and I pulled it out and fired it up. The levels looked "fine" (25 ppm and under, depending on where we held it in the cockpit), and weren't increasing. (see link below for info on "normal" levels--I will likely adjust my threshold on what defines "fine").

"So why was is dot on the card black?", we wondered. "Oh, yeah, we spent a long time in the runup area with the windows open!", we excused.

"Let's check our O2 levels", I suggested. "Since CO binds to hemoglobin, our SpO2 readings should be lower than normal if we really have a CO problem, the SpO2 measured oxygen saturation levels should be lower than what we've seen historically." We both check, we're both about 95%. "OK! We're good!" We soldiered on. Rest of the flight was, LUCKILY, uneventful.

What was really going on, for which I had at least two clues that I "wrote off" as something innocuous, when in reality my plane was trying to tell me "something's not right, buddy!"?

I was hearing an exhaust leak! A post-flight check of the engine compartment by my mechanic revealed a broken exhaust clamp:

22790717849_6395a23ee0.jpg


Now, interestingly, I had opened up the engine compartment and done my own detailed post-flight inspection and DIDN'T SEE THIS. I'm not sure if I'd have caught it even if I'd listened to the "clues" at Meridian and gone back and pulled the cowl. In the future, of course, I will... knowing what "that" sounds like.

So, a number of errors / lessons learned:

MOST IMPORTANTLY: An SpO2 meter will NOT clue you in on CO poisoning! See the links below. It's this fact alone that sparked me to write the story--pilots need to know this. The molecules for CO "look the same" as O2 molecules to our aviation fingertip SpO2 meters! I quote: "A pulse oximeter cannot distinguish the differences and the reading will show the total saturation level of oxygen and carbon monoxide. If 15% of hemoglobin has carbon monoxide and 80% has oxygen, the reading would be 95%."

So, please please please read up on Carbon Monoxide poisoning:


Secondly, I had multiple clues, and was willing to write them off to other causes. Yes, I did "diagnose" the problem and had a "reasonable explanation" for why something seemed amiss. But I was WRONG.

Stop. Check it out. On the ground.

I was lucky. I hope I'll be smart in the future, so I don't have to be lucky again.
 
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Good info. Thanks for sharing. Glad you and Mrs.TW are home safe.
 
Yikes! Glad y'all are alright! I'm curious how bad the levels must have been to trip the cheapo dot, though. Any idea what caused the clamp to open?
 
Yikes! Glad y'all are alright! I'm curious how bad the levels must have been to trip the cheapo dot, though. Any idea what caused the clamp to open?

That's a great question. I've written an email to QG Inc a week ago to find out what PPM trigger the green/yellow/blue segments, but haven't heard back yet. Their product data sheet doesn't specify:

http://qginc.com/sites/default/files/qeds.pdf

The clamp has a "T" bar that should extend up into the other half of the clamp... if you look closely you'll see the T is missing, and the shaft is broken. My mechanic said that if the clamp is over torqued, this kind of failure can happen. Proper torque is 25-40 in/lbs. He tightened the replacement to 32 in/lbs, and then safety wired it, too, as a backup.
 
That's a great question. I've written an email to QG Inc a week ago to find out what PPM trigger the green/yellow/blue segments, but haven't heard back yet. Their product data sheet doesn't specify:

http://qginc.com/sites/default/files/qeds.pdf

The clamp has a "T" bar that should extend up into the other half of the clamp... if you look closely you'll see the T is missing, and the shaft is broken. My mechanic said that if the clamp is over torqued, this kind of failure can happen. Proper torque is 25-40 in/lbs. He tightened the replacement to 32 in/lbs, and then safety wired it, too, as a backup.
Ah, I see it. At quick glance earlier I had just assumed it jumped the slot and was laying over.

This reminds me that my card detector expires here in a few days. Need to run in to the FBO and buy a new one.
 
Ah, I see it. At quick glance earlier I had just assumed it jumped the slot and was laying over.

This reminds me that my card detector expires here in a few days. Need to run in to the FBO and buy a new one.

I threw away the old one, but didn't realize that it will 'refresh' itself (even from "black") after about 8 hours of exposure to clean air. They are good for 18 months from opening. In addition to my CO Experts 2014 ultra-low detector, I now have TWO Quantum Eyes on the panel--one on my side, and one on the co-pilot's side, both to increase the odds of seeing a problem more quickly, and to provide a way to validate the results--if both detectors are showing a problem, you're less likely to dismiss it as a card anomaly.
 
Had a similar issue with my mine - minus the noise. On rotation suddenly there was exhaust rolling into the cockpit. Made a 150º and landed. (departed 12, left turn to land on 27) The vertical exhaust stack had slipped and separated.
 
Man, it seems like there's always something waiting in the weeds to bite us in the ass!

Glad you're here to tell us the story Troy!
 
Had a similar issue with my mine - minus the noise. On rotation suddenly there was exhaust rolling into the cockpit. Made a 150º and landed. (departed 12, left turn to land on 27) The vertical exhaust stack had slipped and separated.

Ed, what do you mean by "exhaust rolling into the cockpit"? Could you smell the fumes, or were you getting smoke?
 
Man, it seems like there's always something waiting in the weeds to bite us in the ass!

Glad you're here to tell us the story Troy!

It does seem funny that our cabin heating systems are generally (until you get into bigger twins and jets) designed as a metal shroud wrapped around an exhaust pipe. :) Make sure that thing gets opened up and inspected / poked / prodded each year!
 
It does seem funny that our cabin heating systems are generally (until you get into bigger twins and jets) designed as a metal shroud wrapped around an exhaust pipe. :) Make sure that thing gets opened up and inspected / poked / prodded each year!
I just had my muffler replaced at annual due to a leak in the shroud... Fortunately the mechanic had a spare on his shelf and only charged me the repair on mine to replace his spare.
 
Troy - glad you're okay!

A couple weeks ago I had a student, on a solo flight, with a similar situation. Except he did get smoke in the cockpit, promptly landed, and his exhaust system was just toast. I mean destroyed. Lots of melted wires too. Really glad he landed immediately, he could very easily have caught on fire.

It seems to have started with a loose (in his case) exhaust clamp very similar to yours. But as we played back the last few solo and dual flights, there were many "hints" that something was wrong, but nothing really definitive. Like his carb heat drop was higher than normal - well, maybe it's because it's colder than normal outside (no, the hot exhaust was going right down the carb heat ducting). Or the rattle that started when I opened the fresh air vent on another flight - figured it was just the vent rattling (since it stopped when I closed it), but it was probably the exhaust itself rattling!
 
Troy - glad you're okay!



A couple weeks ago I had a student, on a solo flight, with a similar situation. Except he did get smoke in the cockpit, promptly landed, and his exhaust system was just toast. I mean destroyed. Lots of melted wires too. Really glad he landed immediately, he could very easily have caught on fire.



It seems to have started with a loose (in his case) exhaust clamp very similar to yours. But as we played back the last few solo and dual flights, there were many "hints" that something was wrong, but nothing really definitive. Like his carb heat drop was higher than normal - well, maybe it's because it's colder than normal outside (no, the hot exhaust was going right down the carb heat ducting). Or the rattle that started when I opened the fresh air vent on another flight - figured it was just the vent rattling (since it stopped when I closed it), but it was probably the exhaust itself rattling!


Exactly! So easy to dismiss the symptoms!

Your student did a good job in aeronautical decision making! Did s/he land at an airport or off-field?
 
Here's my #2 cylinder exhaust pipe, discovered 1400nm from home when already a day late for departure...

12140647_10153618820208286_4224634514668019510_n.jpg


Not sure how, but the dot detector stayed yellow. I'm guessing I flew it that way for 2-3 hours before discovering the problem. Luckily within a couple of hours I found an outstanding certified welder on the field who could weld stainless.
 
Would that not be a left 210º turn ... ?

:wink2:


Now that you mention it, yes. That's what taking 5/325 will do to your math skills - which is why I'm self grounded for a few days! :goofy:
 
This type of failure is so typical of aircraft exhaust systems. many of these pipes are installed under tension and eventually will crack.
This is why a total engine compartment inspection is so important during the oil change.
 
Glad you are here to tell the story, TW.
I vaguely remembered that CO shows up in the O2 sat readings on pulse oximeters but thanks for the refresher, now it will hopefully stay in my mind.
And I am also happy to have a digital CO detector with alarm in the plane. Works well.

As for how the clamp broke, you should back off your Navy landings. How do you rate your landings on a scale of ... let's say ... Richter? :D
j/k of course

Glad to have you still among us. We all should learn from this episode of "how I lived another day", I know I will.

Thanks for the writeup! :thumbsup:
 
I'm curious how bad the levels must have been to trip the cheapo dot, though. Any idea what caused the clamp to open?

That's a great question. I've written an email to QG Inc a week ago to find out what PPM trigger the green/yellow/blue segments, but haven't heard back yet. Their product data sheet doesn't specify:

http://qginc.com/sites/default/files/qeds.pdf

Here's some updated information, from the manufacturer, on how much CO (in PPM) vs. time (in minutes) it takes for the Quantum Eye CO cards to change colors:

23342565062_1bbb12eae5.jpg


They've changed their product packaging to include this in a new insert.
 
Exactly! So easy to dismiss the symptoms!

Your student did a good job in aeronautical decision making! Did s/he land at an airport or off-field?

He was in the pattern at a local airport (but not the one where he keeps his airplane). He says he briefly considered whether he could make it back to home (about 9 nm) but then heard my voice in his his head calling him a moron if he tried it, turned everything electrical off and landed quickly.

He did a great job I thought. It was interesting to hear his decision-making process, which obviously occurred in less time than it takes to read this sentence.
 
Someday I will tell you the full story of my experience with a cracked exhaust pipe on the backside of the pipe (couldn't see it due to the heat shield) and before the turbocharger. Mechanic didn't see it either. I finally found it by feel, confirmed with a mirror on a stick. Had the entire exhaust "refurbished" with new pipes.

Clues were:
1) White deposit on outside, lower section of cowl near cooling outlet
2) Reduced climb rate due to lower power & slight change to throttle settings
3) Exhaust deposits inside engine compartment, and
4) probe failure indication on the JPI due to the probe wiring being burnt.

No real change to the engine sound. And no action on the CO detectors as the vent air inlets are either in front of the cooling outlet or up on the vstab. Like you, though, I use oxygen and had enough time in the plane to know where the flow setting should be for good O2 saturation through the cannula.

The placement of the heat shield kept it from being more damaging.
 
Someday I will tell you the full story of my experience with a cracked exhaust pipe on the backside of the pipe (couldn't see it due to the heat shield) and before the turbocharger.

I look forward to hearing the story. Having an inspection mirror is critical! It's in my travel kit.
 
Moral of the story is a Pulse Oximeter won't help you without a quality CO detection device.

We all know aviation is expensive.....yet we find cheapest ways to supplement what I feel is one of the most important pieces of equipment in your aircraft.

Excellent post to the OP. Gets everyone thinking...and a little safer.
 
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