SavvyAnalysis Puzzlers

Recently a client submitted engine data with an erratic EGT trace. It always makes sense to check the connection first, but in this case it looked like a failing probe. When we reported this, he said that he suspected it failed because he hadn’t been flying much lately because of the virus. Then he asked if we had seen an increase in failed probes with people doing less flying. The first thing that came to mind was a tweet by Foreflight’s Tyson Weihs (@tysonweighs) from September that the seven-day average of FAA IFR flight plans filed was well ahead of 2019 for piston, turboprop and jet categories. But we know that not every plan got activated, so let’s accept the premise of the question and say there’s less flying this year. The second thing that came to mind was a chat I had with the trainer at my gym. He noticed that the elliptical machine I was using made a couple clicks on every cycle. I didn’t hear it because I was halfway through a blues playlist on my iPad at the time. Once I took the headphones off I could hear it. He said all the machines had developed […]

I live in California. I moved here from Chicago in 1983. It’s probably safe to say that Californians think about earthquakes every day. Most days it’s a fleeting thought then you go about your life. But when you feel a rumble it becomes top of mind again. I’ve been part of conversations that began in the center of a room, and when we felt a rumble we continued talking as we moved under the protection of a door frame. The best flying and earthquake story I heard was about a flight lesson on final to Burbank airport on the morning of the Northridge quake in 1994, they were lined up nicely and suddenly the runway moved over and back. Then the tower called and announced it was closing and pilots should use the CTAF. I always wondered if that student wound up getting the PPL – or not. For a while after that quake our hangar flying included discussions about what if you were flying at night and there was a quake. You obviously wouldn’t feel it. You wouldn’t see it. How would you know if the runway was damaged until you and your airplane fell in the hole? Then, […]

I’ll go out on a limb and say that priming the engine is not a precise science. Every POH has instructions, but experience often suggests that some engines like a little more and some a little less. What happens to the excess fuel if the pilot over-primes? Cylinder manufacturers thought of that and included sniffle valves to drain excess fuel from the barrel. When they malfunction, sniffle valves can be a source of an induction air leak, which can cause the cylinder to run lean, even with a full rich mixture. Induction leaks are often traced to a loose or failed clamp or sleeve or a problem with the riser and gasket. We have seen a lot of these in previous Puzzlers. A sticky valve is another way that unwanted air can enter the combustion chamber, but let’s save sticky valves for their own focus. At this point in engine data analysis we haven’t discerned the nuance between an induction leak from a riser or gasket and one from a failed sniffle valve. That may be a good project for machine learning – here’s data from a bad gasket and here’s data from a failed sniffle, find the differences in […]

Thanks to the virus, I think we’re all logging more flight simulator time lately. I was talking with a game-designer friend about sims and haptics. To save some of you running to the dictionary, haptics are kinesthetic cues given by electronic devices. Like when your phone buzzes if the ringer is muted. Or when the little circular device they give you at the restaurant blinks and buzzes to tell you your table’s ready. Or when the game controller begins shaking when you drive off the pavement onto a gravel road. Or when you put your simulated airplane of choice into a steep powered dive and get tail flutter before you recover – or buy the virtual farm. Failures have been part of simulators since the beginning. Instrument failures, control surface failures, and different types of engine failure. We can fail things in the sim that would be too dangerous to fail in real life – fires, bird strikes and gear failures for instance. We were wondering how many more releases it will take before sims will realistically render more common non-catastrophic malfunctions, like a clogged injector, carb ice, a failed spark plug or a magneto failure. You can fail a […]

Maybe it’s just a coincidence that we use the same word for a piece of silicone that directs cooling air over an aircraft engine – and a state of bewilderment. In the world of sound it’s also used to describe the box that contains a speaker. Maybe it’s just cruel irony at work. As the Danish humorist Victor Borge used to say “It’s your language. I’m just using it.” I’m writing this on the weekend before AirVenture 2020 was scheduled to start. Normally I’d be making my way there – the last few times in the right seat of Mike Busch’s 310. I’m glad EAA set up so many online events for the week and a little taste of the comeraderie of Oshkosh is better than no taste, but let’s hope next year is more like last year. Let’s start this month with data from a Cessna 172 XP powered by a Continental IO-360 engine and data from a JPI 830 with a 6 sec sample rate. Those are the particulars but the fact is we see this pattern with big bore 6s and smaller 4s – turbos and air breathers, singles and twins. First the “establishing shot” of the full […]

I was talking with a friend recently and he said “I understand it intellectually, but I’m not sure I’ll ever grok it”. I haven’t heard that word in years, maybe as far back as reading Heinlein in high school. (I was more of an Asimov fan in those days.) But it got me thinking about whether I will ever grok engine data analysis — understand it profoundly and intuitively. In golf it’s a big deal when you shoot your age. I’m 68 and this is my 68th Puzzler. I’d like to think by now I understand it intellectually and I’ll probably never grok it, but I’m happy that these articles have found an audience and new issues continue to emerge. Extemporaneous speaking is hard. In February I was interviewed by Brandon Gonzales for his Podcasting on a Plane series. I started an IMC Club at my local airport and Brandon is a tower controller there and an advisor to the club. Last month I was interviewed by Dean Showalter for his Airplane Owner Maintenance podcast. I taught at the college level online and in the classroom on and off for 20 years. I’ve created over a dozen training titles. So […]

Much of the award-winning advertising from the last several decades was produced by Weiden + Kennedy. As they grew and pushed the creative envelope, their motto became “Fail Harder” – if your failures are small you’re not trying hard enough. As pilots and airplane owners it would be nice if nothing ever failed. Since that’s not realistic, maybe we could save time and money if things failed harder. On second thought no thanks – too many rough runners, dead-stick landings and dark glass panels where purple and green should be. Sometimes the engine monitor data gives us great clues on where to start looking. Sometimes the best you can do is rule things out. Let’s begin this month with data from a Cirrus SR22T with a Continental TSIO-550-K and data from a Garmin G1000 with a 1 sec sample rate. EGTs on top, then CHTs and FF. Up to about the 27 min mark things look ok. EGT 3 has pulled away from the pack to the low side, but it’s steady. Cruise CHTs are great at 300º ± 25º. CHTs 1-3-5 are a little hotter than 2-4-6 as a group, but that’s not corroborated in EGTs 1 and 5, […]

I’ll be honest. Writing this month’s column about engine data as thousands continue to die from the virus seemed – trivial. Then two things came to mind. First, you’re probably reading this to get a short break from the news. Second, so much of the story – the hockey-stick spike in unemployment, the colored maps, the flattening of the curve – relies on infographics. And SavvyAnalysis is all about interpreting the graphic depiction of data. So with sincere thanks to the caregivers and all those keeping us healthy and safe, and a tip of the hat to the infographic creators helping us process this pandemic, let’s see what’s in this month’s collection of data. First up is data from a Cessna 400 with a Continental TSIO-550 and data from a Garmin G1000 with a 1 sec sample rate. The image is EGT only because everything else looked normal. With probes, it almost always makes sense to check the connection first. In this case, that’s probably a step we can skip because of the wild swings in EGT. With a loose connection we’d expect to see normal tracking interrupted by drops to zero or spikes to the high limit for that […]

If you can have latitude in your attitude, then a properly-timed set of mags can have – magnetude. I guess it can have magnitude, too, but this column’s about the good, bad and ugly of mags and ignition spark. The EGT pattern of a perfect mag check can be a beautiful thing. But the analysis team is often summoned because things aren’t perfect, and we have to figure out why. Let’s start with data from a 2013 Cessna 172 with a Lycoming IO-360 and data from a Garmin G1000. This is the whole flight with EGTs on top, CHTs below and FF below that. I always start here to be sure that FF is consistent throughout the mag check. I won’t take the space to show you here, but I have lots of examples of FF changing when the pilot switches to a mag with weak spark and the engine gets rough. Some pilots switch back to both mags, some reach for the red knob. We see it all the time, it’s a perfectly natural reaction and will get no criticism from me – but we don’t want to draw conclusions from the data. In this case FF is steady […]

The flip side of a cylinder running too lean is one that runs too rich. If it’s too lean the usual suspect is an injector clog for those with injectors or an induction leak for carbureted engines. When it’s too rich it’s often because of something all too common – an injector misplaced into the wrong cylinder – or something complicated that’s harder to verify and probably expensive to fix. GAMIjectors and tuned injectors from the manufacturer are engineered for a specific pair of cylinders. Typically on a 6-cylinder engine you’ll have three sets, one for each pair as you work your way aft. So you could swap a 5 with a 6 or a 1 with a 2, but not a 5 with a 1. Most of the time those sets give a good result, but we’ve offered our analysis as GAMI or TCM works with clients, especially on new installs, to refine the injector set based on trial and error and mixture sweeps. Once the spread is in the 0.5 GPH range that’s about as good as it gets. With that background, let’s take a look at some recent flight data. First up is data from a Beech […]

Yep, I’m angling for the award for best mis-appropriation of a Latin maxim. The real phrase – de gustibus… – translates literally to “regarding tastes, it should not be disputed” which in common usage has become “there’s no accounting for taste.” If we took it literally, a lot of film, music, food and other critics would be out of work. If we took my mis-appropriation literally and never questioned the data we get from the Master Bus or other parameters tracked by engine monitors, yours truly and other analysts would soon close up shop. Every day we get a little closer to the point where computers can look at engine data and draw conclusions. But there are lots of variables that humans can quickly observe and calculate that so far keep us a step ahead of an app. For instance, did this anomaly happen before or since the event in question, is it getting worse over time, what’s the power setting or flight condition when it occurs – or not, is this even possible given the laws of thermodynamics, what other data can we use to corroborate or refute what we’re seeing, given that not every airplane logs every parameter. […]

The Estonian physicist Thomas Johann Seebeck died a couple of generations before the Wright Brothers demonstrated powered flight. Each December I remember to thank the brothers from Dayton for their courage and persistence that eventually led to the gift of aviation to mankind, and from now on I’ll be including Herr Seebeck. Because it’s his work with thermocouples that eventually led to SavvyAnalysis. Seebeck studied medicine, but preferred physics, and his work led to the modern thermocouple. Had Seebeck preferred medicine, perhaps someone else would have discovered the connection between heat and electricity, but you can say that about any endeavor. Medicine’s loss is our gain and now we have a (mostly) reliable way to measure important engine parameters. On the ground the information helps us satisfy FAR 91.103 requiring us to gather all available information about our upcoming flight. In the air it can help distinguish a life-threatening in-flight emergency from the nuisance of a bad connection or a failed sensor. First up this month is data from a Cessna Cardinal with a Lycoming O-360 and data from a JPI 830 with a 6 sec sample rate. Four ranks this time – since altitude isn’t logged I included OAT as […]

Some words just mean what they mean and that’s all you get. Some words give you options. Scramble can be a verb or a noun. It can mean to order fighter jets into the air immediately, or a way to cook eggs, or a disordered mixture of things. When we confuse or mask radio transmissions so they can’t be intercepted we call it scrambling. If you see scrambled eggs on somebody’s hat you’d better salute. On a golf course it’s a way for a foursome to ignore the three worst shots. Mine are frequently ignored. Sometimes engine data will arrive as a scramble, as in disordered mixture of things. This week I was looking at data for a Cirrus SR22 and noticed the TIT traces were all over the place. Mostly low, jumpy throughout, sometimes erratic – but EGTs looked ok. I happened to glance at max FF and it was around 28 GPH. It should have been closer to 35 for a turbo-normalized 550 or 38 for the TSIO-550-K. Max MAP was 29ish. So this wasn’t a turbo after all. No turbo, no TIT – so what were those probes logging? And were there actual probes installed, or was […]

Last month I said I would write about this so let’s end the suspense. I’ve been saving data for well over a year. I noticed this pattern before that, but started saving examples in mid 2018. So what is it? In the spirit of good Puzzling, I’ll provide three examples and you can take a stab at the common pattern. These are all screenshots using our Gami tool. Here’s example 1… Example 2… Example 3… If you guessed it has to do with mixture distribution, you’re right – although the Gami tool was a pretty good hint in that direction. But what is it about the distribution? These are all from Cirrus SR22’s with Continental IO-550-N engines. Figure it out ? Give up ? In further keeping with the spirit of Puzzling, here’s a graphic display of the answer. Enough suspense. On these sweeps, and dozens more like them, cylinders 1, 2 and 6 peak earlier than 3, 4 and 5. Sometimes the order is 6-1-2, sometimes 1-6-2 – I’ve seen every combination – but it’s almost always those three in some order. Almost ? Yeah, once in a while I get an SR22 that defies this pattern – maybe […]

It’s that time in the baseball season when teams calculate their magic number – the combination of their wins and losses by others that will clinch the pennant. Computer programmers use the term for something unrelated to baseball. Either way, it seems like a mis-appropriation of the word “magic”. When I think of magic it’s Penn and Teller making a cow disappear – oh, sorry [wink] – an elephant. Something unexpected and unexplained. Something…puzzling. Savvy Analysis just blew out the candles on our 7th birthday cake, and I’ve been writing these Puzzlers for five of those seven. It occurred to me that we’ve written a lot of reports but never formally explained our thought process for making a recommendation for adjustment – or not. The explanation page that’s attached to each report explains what we’re looking at, but doesn’t mention numbers. So I thought I would use this month’s Puzzler to shed some light on that. Let’s start with mixture sweeps. For LOP ops in cruise we’re looking for a GAMI spread of 0.5 GPH or less. GAMI says a spread of 0.8 or less should be ok, but our target is 0.5. We often see 0.5 with GAMIs or manufacturer’s […]

When it comes to troubleshooting issues with an aircraft engine, it’s probably safe to say that any engine data is better than no data at all. Data from cruise flights can tell us about the airplane’s normal operations, and when we have enough data from an airframe & engine cohort we can generate report cards and trend analysis reports. But when it’s time to gather specific information about mixture distribution and ignition system health, we use the Savvy Test Profile – a series of slow mixture sweeps, followed by a lean-of-peak mag check. There are so many great resources for flight training now, in all media. When I was coming up in the ’70s and ’80s, we had print – and I had three favorite authors. For me, nobody told a story like Dick Collins, and I always finished one of his articles feeling like he had helped me set my bar for precision and professionalism. Rod Machado’s method of disarming your defenses with humor always worked on me. And Bill Kershner did something that I stole and used almost every day in fifteen years of classroom and online teaching. He would explain a concept, then tell you that “the […]

I have written about this before, but not in two years, and with lots of new clients and a couple of new Savvy services in that time, it seemed like a good time for a biennial review. The comedians are fond of saying, “Timing is everything.” I think the quality of the material is pretty important, too, but I guess their point is that bad timing can ruin good material, and that comedy is a performance art. You might expect an article about timing from the analysis side of Savvy to be about mags, flame fronts, degrees before top dead center, and getting the most bang for the buck from your engine. This one, though, is suggestions from us about how to get the most bang for your buck from SavvyAnalysis. When To Upload Flight Data Let me remind you that all flight data uploaded by Savvy Mx, Savvy QA and SavvyAnalysis Pro clients is scanned for the EGT signature of a failing valve. That happens without you having to ask. If the algorithm is triggered, we visually inspect the data and if we’re confident that the data is not bogus we will notify you. That’s true whether you’re an […]

The US stock market volatility index is sometimes called the fear index. Usually when the VIX is spiking to new highs, investors are bailing out and other indexes are tumbling. We had one of these events last last year – after a jittery October and November, December saw a “blow-off” top, and when the last seller sold, buying resumed and the VIX settled down again. The VIX was created in 1993 by the Chicago Board Options Exchange, which is roughly when digital engine monitors with the ability to store flight data started replacing legacy needle gauges – or monitors without the ability to store data – in our panels. When I look at a stock chart I find it helpful to overlay the VIX, so I get a sense of what the broader market sentiment was as the stock price moved. When I look at engine data, I like to overlay fuel flow, oil temperature and sometimes altitude, to help put the data in context of the flight. There are lots of parameters in stock charts that don’t correlate to engine data – volume, for instance – but a big spike followed by a big drop gets your attention on […]

I grew up in a river town – Cincinnati – then moved to a lake town – Chicago – and then to an ocean town – Encinitas, CA just north of San Diego. I just started listening to David McCullough’s new book The Pioneers and was happy to hear it begin on the banks of the Ohio. My primary flight instruction was out of KLUK and we often flew up and down the river. Later, living in Chicago, I would rent Cessnas for flight lessons and stay-current trips from KMDW to the Mississippi. I also remember staying low over the Illinois Fox to stay under the Class B at KORD, and – while on vacation in Alaska – landing a 172XP on the Chena and the Tanana for my seaplane rating out of KFAI. So maybe I was predisposed when I opened up data from an RV-10 and zoomed into the mag check. I have friends in and from Texas so I know I’m taking a risk being from the upper midwest and talking about the Lone Star state. But I’ll be danged if that EGT 3 trace doesn’t look like the Rio Grande. Ok, so there’s no panhandle and the […]

These days it’s call throwing shade. When I came up, good jazz musicians had a nice-but-direct way of telling wanna be jazz musicians that they weren’t up to the task – “don’t give up your day gig.” Dr. Graeme Smart has a day gig – he’s the Principal Scientist for New Zealand’s National Institute of Water and Atmospheric Research. Recently he converted digitally-stored weather data into musical data, and assigned pitch ranges and instrumentation to temperature, rainfall, windspeed and direction, river levels and sea level. Obviously the artistry in this project is deciding which sound or instrument will play the fast changing data, versus which will play the occasional event, versus which will play the slow persistent cycles like sea level and temperature. It’s not my cup of tea but judge for yourself. Click to hear the results. By now you may be thinking – perhaps even worrying – that I have taken data from my IO-520-K and converted it to music. I didn’t, but it isn’t hard to imagine. The typical flight would be consistent levels – drones – before takeoff except when punctuated with a mag check – then everything would get loud at takeoff, a bit softer […]

I have been flying my Bellanca Viking for 29 years now. I have had two unexplained events – one electrical and one combustion – both in day VMC. I was alone for both. The electrical event was on approach to a central California airport with a tower. I had deployed the first notch of flaps and the gear was down and showing 3 greens. I had contacted the tower but had not yet received landing clearance. Suddenly the whole radio stack and the nav gear went dark and quiet. A few seconds later, as I was refreshing my memory on light signals, everything came back on.  I advised the tower that I was having an electrical problem and planned to continue my approach and land, but that I might go silent again. Power stayed on for approach, landing, and my taxi to parking. The next day I investigated by powering up each radio – one at a time – then the whole stack. Nothing happened that day, or in the many flights since. The combustion issue was on an IFR flight in VMC from Santa Barbara to Palomar just north of San Diego. It was a very windy Spring day […]

Phoebe Snow’s recording of “No Regrets” is on one of my playlists, and I can’t hear the song without thinking of the Milky Way ad where the distracted tattoo artist gives her customer something to – uh, regert. Sometimes engine data will give us something that obvious, but more often we have to dig a little deeper. Let’s see what the data from this month can show us. Our SavvyAnalysis report form has a field for inoperative sensors. We used to just put “none” if everything appeared to be working properly, but we realized that we weren’t telling customers which sensors we had looked at to be able to say none were inoperative. Plus, we don’t automatically look at every parameter that’s logged by every data monitor. There’s lots of navigation and axis data, for instance, that don’t play a role in engine monitor data analysis. But since OAT is often important in analysis, we decided we would at least look at oil temperature, oil pressure and OAT on each flight we analyze, assuming those are logged. With that in mind, first up is data from a Cirrus SR 20 with a Continental IO-360 and data from a Garmin Perspective using […]

They say what goes around comes around. As the new year arrived and I began my 5th year of writing these Puzzlers, I wondered what I could do to keep things interesting and informative. You the reader and I, acting as your agent scrubbing the uploaded data for good candidates, are at the mercy of what gets uploaded. In the past we’ve had data for complete engine failures, fuel lines coming loose, broken con rods, bent push rods, valves failing in flight, alarmingly high CHTs, clogged injectors, GAMIjectors in the wrong cylinders, fouled plugs, bad mag timing – most of what can go wrong with a piston aircraft engine. Some were mechanical failures, some were the result of poor powerplant management, and some were maintenance-induced. Sometimes I wonder what it would be like if I could take requests like a DJ at a wedding – but if I don’t have the data to work with I’m stuck. It does seem to be getting a little harder each month to find an article’s worth of trouble. I know from writing SavvyAnalysis reports that we see fewer examples of max fuel flow set too low than we used to. I’m not complaining […]

If zero tolerance means we won’t tolerate anything but a zero, then I guess zero zero tolerance means we won’t tolerate any zeros. Usually a zero on an engine data monitor isn’t a good thing unless it has an integer or a decimal point in front of it. 40, 300, 2700, 14.0 – all ok. 0 by itself means something isn’t working. The only parameters I can think of where you’d want a zero are the EGT spread or the CHT spread – the difference between highest and lowest – and you’re not likely to ever see that. Some friends recently sent me a link for the You Tube video of the Cessna 210 out of KCGF making an emergency landing about 90 minutes into their flight from northeast OH to north FL. I hadn’t seen it, and for those of you that haven’t I won’t give away the details, except to reveal that the #4 cylinder vibrates, then both EGT and CHT 4 go dark. Kudos to SuperRook for handling the emergency, especially with valuable cargo on board, and for making and sharing the video. The image that sticks with me is the engine data monitor showing no EGT […]