I Now Know What Happened--Detonation Cooked My Engine

I think I know what happened.

I had a chat with Chris, my AME this morning.  About the low compressions and the leaky exhaust valves.  I rehearsed the whole story to him.  Told him how confused I was about what had caused it.

He sat quietly for a moment and then said:  "I think it was the bad gas".

"How so?"  I said, "All it did was carbon up my plugs.  I changed to avgas and everything was fine."

"I don't think so", he said.  "Some bad things happened to your engine while you were running on that Costco gas."  He explained:

"Typically bad gas is low in octane and octane is what prevents detonation in your engine.  Most people think octane in fuel is a performance enhancer  but in reality, it's a performance reducer.   It prevents the gas exploding instantaneously and allows a controlled burning of the fuel/air mixture which is key to smooth and safe engine operation.

People think the gas explodes in the combustion chamber when the spark plug fires.  But it doesn't.  It actually takes several millseconds to burn and it's the progressive energy from that combustion event that forces the piston down smoothly on the power stroke.

If the gas was to explode, in say a few microseconds, the piston would still be on the way up and the resulting heat and shock waves will seriously damage the piston and valves.  That instantaneous explosion is called detonation and it's a very bad thing."

"My sense", said Chris, "is that while you were flying around trying to sort out what was wrong with your plane, you were subjecting the engine to a prolonged period of detonation.  That detonation drove up the cylinder head temps beyond the allowed limit and damaged the components inside.  And since you don't have a cylinder head temp gauge, you were blissfully unaware of what was going on."

Oh my.  I felt sick to my stomach but knew instinctively that Chris was right.   It was all my fault.

Now, the big question was:  just how bad was it going to be?

With my permission, Chris went to work and started dissembling the engine with a view to removing the number two cylinder which had the worst compression.  I couldn't believe how fast he worked.  He had the cylinder off and on the bench in what seemed only a few minutes.  Clearly, he had done this before.

No. 2 cylinder removed.  Connecting rod and big end clearly visible

We peered anxiously into the cylinder head.  At first glance, things seemed to be fine.  No scoring on the barrel.  The valves were where they were supposed to be and neither appeared to be damaged.  The smaller one, the exhaust valve, had a pinkish hue to it which Chris said was evidence of heat distress.

Chris pushed out the valves and we had a look at the valve seats.  Oh, oh.  Both valve seats were badly pitted all around their circumference.  The exhaust valve itself had a noticeable groove worn around it.  It was obvious that neither valve was sealing properly.

Chris explained that the high temperatures had softened the metal of the valves and their seats and both had started to erode under the continuous heat and pounding of the detonation event.

I was aghast.  So there was my poor engine, its components and valves screaming in anguish, helplessly beating themselves to death, while I sat idly by at the controls!  The more I thought about it, the more I felt like crying!

Pulling myself together (well, not really, it's only a machine after all.  Or is it?), Chris and I had a long chat.  He said that it could have been a lot worse.  The cylinder clearly needed to be repaired, but the rest of the engine appeared to be fine.  The key question was just how bad were the other cylinders?

Cost was going to be a big factor.  A new cylinder assembly from Lycoming, factoring in the horrible US exchange rate, was about $2700 CDN.  Add in GST, say $3000 a pop.  So $12K for parts.  Plus labour, say $15K total.  Crazy.  More than half the cost of a new engine!!

I started having trouble breathing.

The other option was to repair the cylinders.  Regrind the seats and valves.  New guides. Clean everything up and reinstall.  Chris said to expect around $1.2K per cylinder.  Not great, but a lot better than buying new.

Suddenly, in a rare flash of brilliance, I suggested we call Jason Crowell, the President of AeroTech Engines in Halifax whose firm had built the engine 5 years ago.  Perhaps he could provide some insight.

So we did.  And Jason was fantastic.  It's his company's name on the engine and I know he takes great pride in his work.  After listening patiently (with me fully expecting him to scream at me for running Costco gas in his precious engine), he offered to do the cylinder work for us.  He recommended pulling all the cylinders just to be safe because we didn't know how much damage had been done to the other three cylinders.

Timidly, almost afraid to ask, I said how much to do all four?  To my surprise and everlasting joy, he said no more than $500 each and maybe less if they were all like #2.  Whoo hoo!!

So that's what we did.  Chris pulled the rest of cylinders yesterday and boxed them up.  I picked them up this morning and delivered them to FedEx in Barrie for shipment to Halifax.  They should get there by the end of the week.

DKX, sans cylinders, is now back in my hangar awaiting its renaissance.  The engine looks so weird.  You can see right through to daylight on the other side!  Check out the pic below.

And never, I mean never, show this picture to my wife.

Stay tuned for the rebuild, hopefully within a couple of weeks!!

It Happened. The Big $$$ One. Now What?

I'm still in shock.

Got some bad news today.  Low compressions on all 4 cylinders.  All 4 exhaust valves are leaking.  One really badly.  Worst case--complete top overhaul.  Huge $$$'s.  After only 600 hours on the engine.  I still can't believe it.

Paradoxically, I was just re-reading a blog from a couple of years ago, where I was musing that in 28 years of aircraft ownership, I've never experienced "the big one", i.e., a completely unforeseen and hugely expensive maintenance issue.

Well, that all changed this morning.

In my last post, I talked about the bad Costco gas and how I thought that had fixed the engine roughness that I had experienced in flight.  I really thought it had.  But during subsequent flights, I could sense that something was still amiss--the engine just didn't feel right.  It seemed fine in the climb and at cruise, but there was a disconcerting low vibration at lower rpm, particularly noticeable when I reduced power when turning base.  Something wasn't right.

A further clue was a noticeable "softness" in one cylinder when I pulled the prop through by hand.  I had had this happen before, but it went away after several more hours of flying.  This time, even after multiple flights, it was still there.  Hmmm.

Last week, Jim, the guy who has a Thorp T-18 in the hangar next to mine, came by and I asked his opinion.  Jim is a true homebuilder, super experienced, very technical and an engineer's engineer.  He pulled the prop through and frowned:  "Yeah, you got a soft cylinder all right.  I've got a compression testing rig at home.  Why don't we meet next Saturday and I'll check all four cylinders for you."

That was this morning.  I drove to the airport with a gnawing sense of dread in my gut.  Hoping it wouldn't be that bad.  Maybe just the one cylinder.  Maybe a simple stuck valve.  Maybe an easy fix.

Nope.  Compressions were:  #1--70/80, #2--40/80, #3--low 60's, #4--low 60's.  #1 was passable, but the rest were horrible, especially #2 where the air hissing out the exhaust pipe was clearly audible.

Complete and utter bummer.

But why?  How?  A relatively new engine.  Flown regularly.  Never abused.  Lots of x-country time.  My last two engines went well past TBO.  I hadn't changed anything in my technique of engine management.

Car gas?  But I had run both of the previous engines on car gas.

Costco gas?  Poor gas quality leading to valve failure?  Maybe a remote possibility.  But I've got to believe that the bad gas incident was a one off.  Maybe a couple of jerry cans worth.  This was a five years in the making problem.

Too aggressive leaning?  This is the red herring that often gets blamed for burnt valves.  But I've scrupulously followed the POH guidelines--lean slowly to the first sign of roughness, then richen back to smooth engine operation.

Now having said that, and thinking back to the previous engines, I used to run them richer.  My mechanic at the time, Frank DeJong, warned me about leaning too much so I'd only lean to peak rpm and then add back in a couple of clicks for good measure.  Clearly running rich of peak (ROP).

But today's thinking says that running lean of peak or LOP is good for the engine.  As long as the cylinder head temps don't get too high, it actually produces cleaner combustion and stops the valve guides from getting fouled with the byproducts of incomplete combustion.  Or so the thinking goes.

Could I have inadvertently over temped the engine and smoked the valves?  I don't have a cylinder head temperature (CHT) gauge.  No C172 does.  They aren't considered necessary.  But could my little bit of extra leaning have pooched the engine??!!!!!!

Again, conventional wisdom says that the Lycoming 0-320 is such a small, de-tuned, low compression engine that it's virtually impossible to hurt it by over leaning.

At the end of the day, who the *(^%$%  knows for sure?

Jim said that it was weird that all 4 exhaust valves were leaking.  Usually, it's just one cylinder that goes bad.  Could it have been a bad batch of valve guides from the factory?  Improper machining of the valve seats?  Bad exhaust valves from Lycoming's supplier?

Clearly at some point, I will need to have a conversation with Jason, the president of AeroTech, the firm that overhauled the engine 5 years ago.  He's a nice guy and there maybe something he can do from a warranty standpoint, but I will need to have all my facts straight first.

Next steps?  A borescope exam of each cylinder to see what's really going on in there.  Hopefully Chris my mechanic will do that next week.

Stay tuned. 

And if you're feeling charitable, please go ahead and start a "Go Fund Me" campaign for my poor, ailing exhaust valves.  They're gonna need it.

Bad Gas. I'm Never Going to Costco Again!!

A few weeks ago when I was up for a local flight, the engine began to run slightly rough.  At first, I thought it was my imagination, but as I flew along, it actually stumbled for a nano second and my adrenaline spiked.  Steve Coonts in his book The Cannibal Queen calls it a "lummer--a shot of cold urine to the heart".  Urine, adrenaline--same concept I guess.

Anyway, it certainly got my attention.  I peeled off back toward the airport and on the way checked the mixture and mags.  The mags were fine, but as I leaned the mixture, the power climbed quite a bit more than usual before it fell off.  Normally during leaning at cruise, the power moves slightly higher, then drops off as the mixture moves lean of peak.  In this case, it climbed.  A lot.  Hmmmm.  Symptomatic of an overly rich mixture??

When I got back on the ground, everything seemed fine during taxi.  But I felt that the engine was running a bit rough at idle.  Or was it my imagination again?

Back in the hangar, I decided to have a look at the plugs.  Their colour is generally a good indication of the state of the mixture.  White or light grey means too lean, light brown is good, dark brown or black is too rich.

I unscrewed the #1 cylinder lower plug  and had a look.  It was soot black!  Not just black in colour, but coated in black soot!  What the ^&%&????  That could be big trouble!!  A stuck valve?  Blocked air intake?  Who knows, but clearly that cylinder was in trouble!

I unscrewed the #2 plug.  Same thing!!  #3 and #4 were also the same!  Soot black.

Ok.  So it wasn't a single cylinder problem.  It had to be carburation.  I checked the air filter.  Clean. No obvious blockages in the intake system.  Hmmm.  Time to talk to Chris my AME.

Chris said yes, it could be a carburetor problem and it might need to be overhauled.  But with only 600 hours on the engine that seemed unlikely.  But he was super busy and couldn't get to the plane for several weeks.  Great.

And then he asked:  "You run car gas right?"  I said yes, most of the time.  He asked: "Where do you get it".  I told him Costco.  I use their premium which doesn't have any ethanol.

He said:  "I remember a fellow a while back who got a load of bad car gas from somewhere and it made his engine run really roughly.  He switched back to avgas and it smoothed out immediately."

OH REALLY??!!!

That was enough for me to hear!  I headed back over to the plane and immediately drained out the gas into several jerry cans.  I then taxied (still seemingly running roughly) over to the airport gas pumps and filled the tanks with 100LL.  At $2.18 per litre it cost over $300!!  Still if that fixes it, it would be worth every penny!

I fired up the plane.  It  ran roughly for a minute or so and then noticeably smoothed out!!  Whoo Hoo!  That was the freaking problem!!

I took the plane flying and it ran normally.  After landing I pulled the plugs.  They were now perfect!  A nice light brown.  No soot at all.  Thank you Lord!!!

Needless to say, that was the last time I bought gas at Costco!   Clearly, the price of their premium gas was attractive, often 20 to 30 cents less than the name brand guys.  But definitely a bad idea.

After checking around on the internet, I determined that Shell Premium had a reputation of being the best quality gas available.

Needless to say, that's where I'll be going from now on!!

Christmas Came Early--Installation of an IFR Certified GPS Navigator!

When pilots upgrade their panels, particularly with equipment used for serious IFR flying, they generally take their plane to an avionics shop.  A week later they show up and fly away with the new gear installed, certified airworthy by a professional shop and generally functioning as expected.  A very large cheque is usually written at some point in the process.

As I noted previously, I always wanted to have a certified GPS navigator in my plane, particularly now that I had an upgraded panel and a digital autopilot.   Clearly, the ideal time to install a new navigator was when I had the panel opened up for the ADS-B install.

However, the cost of certified boxes, e.g., the Garmin GTN series, were big bucks, and would cost more than half the cost of the entire airplane to supply and install.  Way out of reach for this budget minded aviator.  So at the time, I reluctantly said no to a new panel mounted GPS.

That was Feb. 2019.  Later in April at Sun and Fun, true to form, Garmin announced a brand new, low cost GPS navigator, the GPS 175.  Cost?  $4000US!!  I couldn't believe it!  If only....

Regardless, I planned to order one later in the year and make it my winter project to install it.  And that's what I did.

I again sourced the unit from Dave at Eagle Aircraft in Parry Sound and he did up the wiring harness as before.  The harness is pretty simple--power, ground and 3 serial ports to interface with the autopilot, Aera 660 portable and the GTN 225 radio.  Also included was another GPS WAAS antenna and coax.  Unfortunately, I couldn't use the GPS antenna already installed for ADS-B.  As I mentioned previously, it's ok to take the GPS signal from the navigator to the transponder, but not ok to do it the other way round.

The big decision was how to organize the new panel.  In lieu of a panel mounted navigator, I had mounted the Aera 660 portable in an AirGizmos dock at the top of the panel.

The Previous Panel after the ADS-B Install

Clearly, the portable needed to come out of the panel but the 4" whole it left was too large for the 2" GPS 175 to go back into.  Hmmmm.

It looked like everything would have to be moved up.  Plus, convention put the audio panel at the top of the stack (which I had ignored previously).  So it would be, from top to bottom:  audio panel, new navigator, #1 Comm, #2 Comm and transponder.

And yes, you guessed it--all the trays (which, if you read the previous post, were a royal pain to install) would have to all be moved...again.

One of my concerns with moving the trays was having to drill even more holes in the instrument frame.  The plane is 46 years old and has had a variety of radios over the years.  The frame on both sides looks like swiss cheese from all the drilled holes.  Fortunately, the floating nut plates that are used to secure the trays are quite robust and should still work ok.

Once the new navigator arrived, I moved the plane into Chris, my mechanic's hangar, and got to work.  I was amazed at how fast I was able to progress.  Clearly, my trial and error experience with the whole ADS-B installation was paying off.

Trays Arranged and Re-installed

I had the panel stripped down pretty quickly and pulled out the radios and trays.  My technique of stacking the trays with the radios installed on the bench and then making two drilling template went perfectly.  I had the new holes drilled and the trays reinstalled in one day!  The wiring harness went in and I was able to connect everything together the next day, as well as configure the units.

Chris came over, had a look at everything and told me I had made "a very clean installation".  Whoo hoo!

I went flying the next day and was completely blown away by the amazing capabilities provided by the new navigator.

I took off and headed east climbing to 3500 feet.  I pushed the "Procedure" button on the 175 and loaded in the RNAV 31 approach at Edenvale, using SIGLI as the Initial Approach Fix.  I turned the autopilot to GPSS mode and punched "Activate" on the 175, then put my hands in my lap and watched the magic.

The plane turned to a perfect 45 degree intercept to capture the track and then proceeded to follow the approach course complete with perfect turn anticipation to intercept the waypoints.  As the plane turned 90 degrees to intercept the final approach course, the navigator flipped from TERM (Terminal mode) to LPV (Localizer Performance with Vertical navigation) mode.  The autopilot switched to ARM and the glideslope jumped to the top of the CDI.

As we proceeded along the final approach course at 3500 feet, the glide slope slowly came down on the CDI.  Once it hit centre, the flag flipped to CPL (Coupled), the nose dropped and the plane started down, following the profile to the airport.  All I had to do was adjust the throttle to maintain 80 kts, tweek the trim and lower the flaps.  We flew right down to 200 foot minimums (in clear weather of course!).

Once we hit the MAP (Missed Approach Point), I initiated a full power climb for the overshoot.  The 175 then navigated us to the MAHP (Missed Approach Hold Point), made a perfect direct entry into the hold and flew several perfect, wind corrected ovals around the holding fix!!  Absolutely amazing!!

Needless to say, I continue to have fun with my new toys.  Regrettably, my instrument rating needs to be renewed so I can't legally file IFR, but I sure can fly a lot of approaches in clear weather.

Once this COVID-19 thing winds down, I'm hoping the social distancing rules will be relaxed and I can, once again, fly with an instructor and ultimately with a pilot examiner to pass my IPC (Instrument Proficiency Check).

In the interim, I'm reviewing all the approach plates for Erie, PA and Lynchburg, VA where my daughter lives with her husband and children.

Forget about the weather honey!  We're comin' down!!

ADS-B Installation--Connecting Spaghetti--Installation of The Wiring Harness!

So the avionics trays were installed and it was time for the big one--installing the wiring harness!!

As I mentioned before, the avionics shop that supplied the new radios also assembled the wiring harness for me.  I gave them a rough sketch of the interconnects between various components (including the autopilot) and they built it from scratch.

Now sitting on the bench in the hangar, it looked like a large ball of multi-coloured spaghetti and was totally intimidating.  However, upon closer examination, it was relatively easy to sort out and I came to appreciate that it was actually a work of art.

All the D sub connectors for each radio with the appropriate pinouts had been beautifully assembled.  Each wire was labeled and colour coded.  The wires for the 4 place intercom were all there and, as I learned later, were exactly the right length for installation in a C172.  Clearly, the shop had done this before.

The first step was to install new breakers including an avionics master switch in the bottom of the panel.  This was pretty straight forward once the fuse panel had been unscrewed from the panel and pulled forward for better access.  I had to connect the new master switch to the avionics bus and then fabricate a "daisy chain" of wire and ring connectors that looped from the master switch to each of the breakers.  It took me a while to get reasonably competent at crimping the connectors (and there were lots of them!) but with Chris' help I caught on pretty quickly.

The second step was installation of the antennas and coax.

The Garmin GTX 345 transponder requires a WAAS GPS source.  Typically, this is provided by a certified IFR navigator in the panel, but alas, I did not have one of those, yet!  Therefore, a dedicated GPS WAAS antenna was required exclusively for the transponder (which contains its own GPS receiver.)

Installation of the GPS antenna was pretty straightforward as it mounted perfectly through the hole in the cabin roof left by the ADF antenna.  I drilled and installed the antenna and then fished the coax across the roof, down the doorpost and behind the panel.

Next, I connected the second piece of supplied coax to the transponder antenna in the floor of the cabin and left it too, coiled behind the panel.

Now for the big one!!  I literally picked up the whole spaghetti mess of wires and connectors (it took both hands!), carried it over to the plane and literally stuffed the whole enchilada into the big hole in the front of the panel!

The next several hours were spent routing wires and aligning the connectors top to bottom where they would connect to the trays.  The most time consuming part was running the wires and making the connections for the 4 place intercom, particularly the back seat locations which I had fabricated to be located in the old ash trays.

I also had to connect all the grounds (there were 14 of them!) to a common ground point under the panel.  I used a couple of bolts drilled into the parking brake bracket as the terminal attach points.

I then reinstalled the trays, carefully connecting each D plug to the appropriate tray.  I then slid all the radios into the trays, sat back and admired my work.

It looked freaking awesome.

But would it work?!!

It was time for the moment of truth!

With Chris sitting beside me, I carefully double checked all the connections.  All looked good.  I then pushed on the master switch, waiting with bated breath to see if anything untoward happened (like breakers popping or smoke curling up under the panel).  Nope.  Nothing.  So far so good.

Next I flipped on the avionics master and boom!! everything on the panel lit up!!!! Wow!!   I swear the panel looked like something out of the Starship Enterprise!  And on a lowly 172!!  I wanted to hug someone.  Anyone.  But Chris was the only one there and that would have been weird, so we just sat there and smiled at each other.

I won't bore you with the configuration and set up process that had to be done for each unit using the installation manuals as a guide.  Eventually, everything was talking to everything else as it was supposed to.

It was time to put the plane back together and go flying.

ADS-B Installation--Trial and Error Mounting the Avionics Trays

I\ve gained a new appreciation for the complexity (and the high cost) of avionics work.

The ADS-B new radio stack project has taken way, way longer than I expected.  As you know, I've chosen to do all the work myself (under the supervision of my AME) and I realize that I move at a glacial pace (compared to the avionics techs, who do this all the time)

This stuff is really complicated.  There are wires running everywhere and I'm having to learn a lot about electronic components and nomenclature.

Nevertheless, I'm enjoying the process immensely.

Once everything had been ripped out of the plane, the first step in the rebuild was to mount the trays for the new radios.  This process turned out to be way easier said than done.

Initially, I figured I'd start at the bottom (with the new transponder), mount that tray and then work my way up.  Dave at Eagle suggested that each tray should be separated by a minimum of 40 thousand, so I cut a couple of strips of .040 aluminum to act as spacers.

Each tray is secured by four #6 machine screws that screw into floating nut plates that are clipped on each side of the instrument panel frame.  Needless to say, the hole pattern in the new Garmin trays were not the same as the old tray pattern.  So new holes had to be drilled.

After fitting and marking, I used Chris' air powered, right angled drill to drill the new holes.  Each hole had to be centre punched big time to prevent the drill bit from wandering, but I managed ok.

I clipped on the nut plates, slid in the tray and fastened the screws.  It looked pretty good.  So on to the next tray (my old Narco Mk 12D radio).

What became quickly apparent however, was the difficulty of trying to judge the how far back in the frame to mount the tray, without the two radios being in place.  And if I slid the radios into the trays, it was impossible to mark the location of the holes!

So I took my best guess and drilled away.  After screwing in the second tray and sliding in the radios, I was dismayed to see that the radios were about 1/8" out of alignment!!  Oh, oh. Clearly my "bottom up" approach was not going to work!

After chatting with Chris, I came up with a different approach.  I decided to stack all the trays (5 of them, 6 including the AirGizmos panel dock) on the bench and clipped them together using cleco clamps.  I slid in all the radios and then tweaked the trays to ensure everything lined up.

I then removed the radios and clamped two aluminum stips to each side of my temporary "stack" and marked the hole locations using a fine tipped marker.  Voila!  I now had two perfect templates for the hole locations.

I then drilled out the holes on the drill press, mounted the templates on each side of the instrument frame with cleco clamps and drilled away using the template as a guide!  This time I was confident that everything would line up properly and it did!!

All the radios slid in nicely and were perfectly lined up top to bottom.  Beauty!  Standing back, the whole thing looked pretty awesome.  However, it was only a facade because there were no wires connecting anything yet.

So stay tuned!  Installing the wiring harness is next!!