SavvyAnalysis Puzzlers

Good news! They’re making Spinal Tap 2, with plans to release it in 2024 – 40 years after the first one. Of all the great quotable lines in ST1, it’s hard to top “these go to eleven”. Sometimes we get a set of screwy engine data that makes us wonder if the data came from one of those “eleven” monitors. When I’m working tickets, I find they fall into three basic categories. First is when I see something familiar, like a clogged injector or weak spark in one of the plugs. Sticky valves are getting easier to spot. Failed and failing probes are usually easy to spot. Second its when I see something that isn’t as familiar, but makes sense in the context of the details on the ticket. Examples are induction leaks, vapor lock, and loose baffles and other cooling problems. The third category are the ones that require a deeper dive. Something is happening and we’re not seeing it in the data. At least not initially. Well start November with one of those. First up is data from a Bonanza 35 powered by a Continental IO-520 engine with data from a JPI 900 with a 1 sec sample […]

A lot of analysis requests begin with “Something bad just happened and we had to divert and land. Is there something in the data that would’ve told us this was about to happen?” Our first reaction is usually relief – that the pilot got on the ground safely and is able to make the request. Then the forensics begin and we start looking through the data for clues. Sometimes the warning signs are obvious. January’s Puzzler tells the story of a 172 making a cross-country trip, with oil pressure dropping at every stop. Eventually the engine quit and the airplane landed in a field. Sometimes the warning signs aren’t obvious, at least to the trained human eye. Savvy Ai is using machine learning to look for patterns and trends that elude detection using our current graphic depictions. Meanwhile, let’s look at some recent events and see what the data can tell us. You’ll notice a different look to the screenshots this month. I’m using the new beta version of the flight data page. First up is a Cessna Turbo 206 powered by a Lycoming TIO–540 and data from a Garmin G1000 with a 1 sec sample rate. This is the […]

Baseball has the cycle – single, double, triple and home run. What would that be for an analyst working a shift? Clogged injector is probably the single. Bad spark plug is probably the double. Let’s say the triple is a stuck valve. And the homer is a detonation event. How about a catastrophic part failure? Clearly a broken bat hit. Foul ball is a failed probe. Still working on the analysis equivalent of a bunt. This month’s puzzler isn’t exactly a cycle, but it should keep you thinking. First up is a Cessna 170 powered by a Continental O-300 and data from am EI CGR-30P with a 1 sec sample rate. EGTs, CHTs and FF. Nothing special about cursor placement – just midway through the flight. The things that jump out are — EGT 2 is high whenever the engine is making power – during idle it drops down with the others. CHT 2 is a little lower than 3 and 4 which are hottest. CHTs 5 and 6 are abnormally low, in the 200 range in cruise. But EGTs 5 and 6 are right there with the others, suggesting that the low CHTs are because of cooling and not […]

Apparently the 80/20 rule is also known as the Pareto Principle. Broadly applied, it means that 20% of your activities will account for 80% of your outcomes. In my previous careers in advertising and education, I would contend that 80% of stuff I spent my time on were caused by 20% of my ad clients – or students. After nearly ten years of reviewing engine data, I’d say about 80% of our tickets are either fuel issues, spark issues or bad sensor data. That’s good news for our clients, because both are relatively easy to fix, and good news for SavvyAnalysis because those are usually easy to spot and we can deliver a quick and accurate diagnosis. But when the Puzzler deadline rolls around each month, it’s the other 20% that are usually more interesting to write about. This month we’ll look at data from a Piper Saratoga, an RV-6, a Cessna 414, and a Cessna 182. First up is data from a Piper Saratoga with a Lycoming IO-540 engine and data from a JPI 700 with a 6 sec sample rate. Even though the older JPI’s shipped with a six second sample rate, we advise clients to reset that […]

It’s always fun at Oshkosh when one of the technologies of GA makes a move after spending a lot of time on the plateau. Avgas is the latest example. For years we just pumped it and worried about the short-term cost and the long-term availability, and now we’ve got some interesting new options to consider. A few years ago it was electronic mags. Before that, glass panels, electronic flight bags, flow-balanced injectors, active noise reduction headsets – the list goes on. It feels like we’re at a plateau with engine monitors. For the past thirty or so years we’ve had the same basic thermocouple sensors to gather EGTs and CHTs, and other types of pressure and flow sensors for other engine data. Garmin just made an improvement in their manifold pressure sensors for the G3X Touch, but adding a snubber is more like a small step than a giant leap. (Sorry, I get this way every time an Apollo 11 anniversary rolls around.) Displays are certainly prettier now, and with most units you can program alarms to warn you of trouble. Maybe this Oshkosh will bring a surprise from the engine monitor direction. Meanwhile, we’ve got puzzles to solve. First […]

I’m not spoiling the movie if I tell you that one of the opening scenes of Top Gun: Maverick is a pilot swinging a wrench on an owner-flown piston-powered warbird. That may be enough to make you want to see it, although from the box office numbers so far they don’t need help filling seats. The camera point of view is from the other side of the plane, so naturally the engine data geek in me wondered if he was changing out a faulty probe for his state-of-the-art digital engine monitor. Hey, a guy can dream. It’s tempting to go off on a rant about how GA is often depicted in the movies, but that’s not why you’re here. So let’s look at some data from recent flights. First up this month is data from a Cessna 172RG powered by a Lycoming IO-360 and data from a JPI 700 with a 6 sec sample rate. Cursor is on the beginning of the CHT 3 excursion. FF is logged in liters per hour – 46 LPH is 12.1 GPH. That climb in CHT 3 is from 325º to 525º – exactly 200º – in just over 4 minutes. Can we trust […]

The Greek poet Archilochus wrote, “The fox knows many things, but the hedgehog knows one big thing.” I’m reminded of this when clients ask “Which engine monitor should I buy?” Savvy doesn’t endorse brands or product models, so without naming names, we think the best choice is the one that reliably gives you the information you want in real time and then makes the download/upload process easy to accomplish. On that last point, I know some clients want a system that automatically connects to a wi-fi network and seamlessly uploads new engine data as they taxi down their hangar row. For me, downloading to the thumb drive comes right after mixture and mags, and before master off. Whichever model gets you to do it – that’s the one you want. To generate a report we use EGT, TIT, CHT, FF, RPM, MAP, Oil pressure and Oil temp, OAT, and Bus Voltage – x2 on a Cirrus. GPS Altitude is nice to have to verify what looks like a climb or descent. Sometimes Fuel Pressure is helpful when diagnosing a fuel issue. Carb temp is often helpful when ice is suspected. Those parameters pretty well define the hedgehog monitor, at least […]

We’ve seen an increase in issues related to induction lately. Is it because many airplanes spent more time grounded because of the virus, and issues are emerging as the hibernation is ending? Or maybe it’s just that for most of our US-based clients, temperatures are warming and taking their toll on clamps, sleeves and gaskets. Whatever the reason, we’ll spend this month looking at what’s different about data from induction leaks. It’s tempting to drift into the mechanics of an induction leak, but I’ll stick to how to spot it in the data. John Deakin, Mike Busch and others have written extensively on plumbing, Bernoulli and Venturi if that’s what you’re after. I’ll drift this far – when your MAP gauge is showing 12″ at idle, and ambient pressure is around 29″, your gauge is measuring suction. More accurately, it’s measuring how much of that ambient pressure it’s keeping out of the engine. Knowing that, and before looking at any data, what if we see idle MAP up around 16-17″? It means that for a normally aspirated engine – carb or injectors – air is getting past the closed throttle plate and into the engine. What about turbos? At idle, […]

Are you playing Wordle? It’s fascinating to me how this puzzle has caught on as we look for distractions from that other 5-letter word that begins with C and ends with D and has two non-adjacent vowels. What has this got to do with analysis? Well, sometimes – actually, most of the time – we get symptoms and we’re pretty sure what it is, and it turns out we’re correct. Call it 1/6 or sometimes 2/6. We love those green tiles. Other times, it feels more like 4/6 or 5/6 as we sift through the options.  Do you have a favorite starting word? I have one friend that insists that vowels are the key, so starts with words like adieu and canoe. A different friend insists that if you get the consonants right, the vowels fall into place. Hw mprtnt r vwls anhw? We’ll start this month’s Puzzler with one of the more unusual scenarios we’ve seen. This is from a Cessna 180 with a Continental O-470 and data from an EI CGR-30P with a 1 sec sample rate. Here are EGT, CHT and FF for three flights with about a week between them. Nothing special about cursor placement. The […]

Recently I saw an ad for a furniture store encouraging me to “kickback in style”. I remember hearing that word a lot as a term for relaxation when I moved to southern California in the early 80s. Before moving, I had read that word a lot in the Chicago papers in regards to unscrupulous public servants. And years before that, it was what my Royal Enfield 750 liked to do on cold mornings. In the world of aviation, we usually hear it in regards to starters – and it’s usually not good news. Usually engine starts happen before the avionics bus goes to ON and before the engine data monitor starts logging – which is why you’ll rarely see engine starts as a topic in this column. But I do have a good one for you. Recently Savvy account manager Dean Showalter discussed a problematic engine start event that resulted in a cracked starter housing on his Airplane Owner Maintenance podcast. Dean and I worked together on a ticket for a 172, and that’s where we’ll start this year’s set of puzzles. First up is data from a Cessna R172K Hawk XP with a Continental IO-360 and data from a […]

“A guy opens his door and gets shot and you think that of me? No, I am the one who knocks!” — Walter White. Sometimes I look at my airplane the way Skyler looks at Walt in that scene. On my recent annual it was a crack in the flange of the muffler can. On the 2-4-6 side of the engine, inboard, hairline crack about 3 inches long with the precision of a laser. Could only see it with a mirror and reflected light. And just like that my annual, which had been routine and painless to that point, got filibustered. It’s repaired now, but it reminded me how airplanes offer so many opportunities for — as Walt would say — someone to knock.  We’ll wrap up this year with data from a Piper Archer, a Cessna 175 Skylark, a Cirrus SR22 and a Cessna 210. First up is a Piper Archer with a Lycoming O-360 and data from a JPI 900 with a 1 sec sample rate. First a comment on that, and judging books by their covers. When an Archer or a 172 or a Musketeer has signed up for our service, the assumption might be that data will be minimal and […]

Would you know the symptoms of a broken valve spring in your engine data? We’re pretty good at spotting clogged injectors and fouled plugs from their distinctive patterns. We even developed our FEVA scan for detecting burned valves. Broken valve springs can be, like the song says — as restless as a willow in a windstorm, as jumpy as a puppet on a string. Sometimes the decision tree is more like a forest as you work through the possibilities and rule things out. A broken valve spring is rare enough that it’s usually not the first thing we suspect. Or even the fifth thing. But they’re out there and the more of them we see the better we’ll get in spotting the data patterns for them. It’s not much of a puzzle if you get the answer ahead of time, so without telling you which one, we’ll tell you that one of this month’s cases was a broken valve spring. We’ll start with data from a Cirrus SR20 with a Continental IO-360 and data from a Garmin Perspective with a 1 sec sample rate. The concern was “severe surges in the takeoff roll” so since CHTs are normal and aren’t […]

In our last episode, we looked at events that seem to happen randomly, versus something that breaks and stays broken. Let’s call them hiccups. I had too many for one Puzzler, so this is Hiccups Part 2. The annoying thing about hiccups is there’s no guarantee it won’t happen again. Part of you is glad it’s just a hiccup that appears to have corrected itself, but there’s this nagging feeling that it might happen again — and probably at the worst possible moment. Or maybe I’ve just read Fate is the Hunter once too often… We’ll start this month with data from a Cessna 340 with RAM VII modified Continental TSIO-520 engines and data from a Garmin G1000 with a 1 sec sample rate. Here’s the overview of the 23 min flight. Nothing special about the cursor placement, just getting it out-of-the-way. The client reported — L engine dropped RPM and MP significant enough to cause yaw on the takeoff roll. On a following flight, this did not occur. Has been fine since, not sure what this was. Plane sat for 3 days prior to this flight, I did not notice any water or debris in fuel samples taken immediately […]

Hold your nose and drink a glass of water. Take a deep breath and hold it. Have someone scare you. There are lots of “cures” for the human hiccups. Don’t try these when your airplane hiccups. If you could choose, would you rather deal with something that breaks and stays broken, versus something that seems to happen randomly – and never when the shop has the plane? Neither is very welcome, but sometimes there are troubleshooting clues in the engine data. This month we’ll take a look at hiccup events and see if we can determine what caused them. We’ll start with data from a Bonanza 33 with a Continental IO-520 and data from a Garmin G3X with a 1 sec sample rate. The request noted intermittent oil pressure fluctuations during recent flights. Rather than show my standard ranks of EGT, CHT, FF and Oil temp, let’s start with oil pressure isolated. The arrows on the left are partially hiding the trace, but it’s a little steadier there than later. There are three noticeable jumps in the trace – at 10 mins, at 20 mins and a short blip at 2 hrs. I wondered if they were coincident with changes in power, […]

Pilots think of ground effect as the reduced aerodynamic drag that happens under the wing to cushion a landing or help with a short-field takeoff. Analysts, who are also all pilots by the way, think of it as what happens when a poor ground connection for an engine data monitor interferes with collecting the data. What’s to be gained by looking at crummy, unreliable data? If you saw these indications in the air they’d be unsettling. If you saw them while reviewing the data after the flight you’d be tempted to put the airplane in the shop. But what do you tell the shop? Replace all the probes? That might be an expensive trip to nowhere, since you would spend a lot of money and not solve the problem. So let’s review some data and determine if they are ground issues or not, so if you see a pattern like this you can take the appropriate next steps. Let’s start with data from a Cub Crafters Carbon Cub with an ECi 340 engine and data from an EI CGR-30p with a 1 sec sample rate. The client submitted a flight and when we opened it we saw this. It looks […]

I have written about this before, every two years since 2015, and with lots of new clients and some new services since last 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 (B4Y$) from SavvyAnalysis. When To Upload Flight Data 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 Mx, QA or Pro client. The Failing […]

I’ll admit that coming up with a clever title is one of the rewards of writing a monthly article. But I didn’t spend a second trying to find a clever or arcane title for this one. I wanted it to be clear what this month’s topic is. The puzzle is which engine data parameters should we look at, and what patterns should we expect to see? Before we formally opened the doors for SavvyAnalysis in 2012, we knew that engine data could reveal clogged injectors, misfiring spark plugs, failing sensors, and other common maintenance issues. As time marched on, we began to recognize the oscillating patterns of failing valves, which evolved into FEVA, then FEVA 2.0 and now FEVA 2.1. We now have a pretty good decision tree for spotting a sticking valve, which I wrote about in December and January. In the 79 Puzzlers preceding this one, we’ve looked at failed mags, detonation, vapor lock, runaway props, induction leaks, and some catastrophic failures. In some of those cases, we thought it through and looked for a rise in this or a drop in that. So let’s apply that process to cam lobes. Every time your cam rotates those lobes […]

Of all the anomalies that can quickly grab your attention in-flight, which one is second on your list? Because obviously a fire is at the top of the list. For me it’s a rough runner, but a change in oil pressure is right there with it. The IO-520-K in my Bellanca Viking settles in around 50 psi so it would be easy to spot if it moves either way. Fortunately, so far at least, it hasn’t – knock a wing. Lately the analysis team has had a bunch of oil pressure and oil temp tickets. So I thought we could devote the May Puzzler to oil. Let’s not forget that it’s so much easier to recognize a loose connection or a failed probe after the flight ends and the data is uploaded. The pilots in these scenarios had to figure it out on the fly, with no guarantees that something worse wasn’t about to happen. Savvy thinks that reviewing these patterns will help pilots make more informed decisions when oil becomes turmoil. Let’s get started. This is data from a Beech Bonanza 36 with a Continental IO-550 engine and data from an Insight G3 with a 1 sec sample rate. […]

I’m in the middle of Walter Isaacson’s new book on Nobel Prize winner Jennifer Doudna. She co-founded CRISPR which is an acronym for clustered regularly interspaced short palindromic repeats. Imagine having the tools to make humans immune to viruses or other diseases. We could eliminate baldness. And glasses. And hearing aids. And maybe cancer. All sorts of ethical questions arise when we talk about genetic engineering to remove human “flaws”. But it would be nice to have it for airplanes.   Maybe we do – sort of. Certified airplanes “technically” leave the factory per the FAA-approved Type Certificate Data Sheet and with zero flaws in the airframe and powerplant. “Technically” because there are Mondays and Fridays and no guarantees that everything was assembled to perfection. With experimental airplanes often the goal of the first few flights is to uncover the flaws. Even if we were to achieve perfection at zero hour, it’s what happens to airplanes in service that causes most of the trouble. So while we dream about the perfect world, fortunately we have tools to help us cope with the real one. First up this month is Cirrus SR 20 with a Continental IO-360 and data from a Garmin […]

I heard a weathercaster dig up the old “In like a lion, out like a lamb” line recently in reference to the weather in March. As I write this we don’t know if this year’s “out” will be a lamb or something more fierce. But it got me thinking about airplanes named for animals. We’ve got Mustang, Beaver, Camel, the F-14 Tomcat and its whole Grumman family of cats, and then a long list of birds from the SR-71 Blackbird and the F-16 Falcon to the Skyhawk and the Swift. And the Gypsy Moth. Sometimes when we suspect a failure of an EGT or CHT probe we wish it went out like a lion. One last big roar and then o wim o weh o wim o weh – the lion sleeps tonight. More often we see a lamb-like baaaaa that’s either distracting to the pilot in real time or confusing to the analysts looking at the data. Fortunately, from an employment perspective, we’re happy that it still takes the human animal to put the data in context and draw meaningful conclusions. And it gives me something to write about every month. So let’s get started. We’ll start this month […]

Part of the job of engine data analysis is separating relevant, useful information from red herrings. I always wondered why there were two definitions for red herrings; the first is a smoked fish and the second was something meant to distract from the main issue in an argument. What did one have to do with the other? It turns out that the smoked fish – which turned red in the smoking process – was used to train hunting dogs to focus on the scent of the prey and to ignore distracting smells. Sometimes we get an analysis request that contains a piece of information that’s tempting to chase, only to find it’s a separate issue or not an issue at all. Pilots have to deal with red herrings in real time. The mother of all red herrings is failure of a flight instrument. Shortly into my instrument check ride, with me under the hood, the attitude indicator went toes up. The DPE waited for me to say something – it didn’t take long. We weren’t far from base so we shot a partial panel approach, swapped that Archer for another, and finished the ride. There’s nothing about it in the […]

This is part two of an article about sticky valves. Part one is here. The cliffhanger was a Cessna 182 with a wobbly trace in EGT 4 for the first 14 mins of ground ops. Your homework was to decide if it was a sticky valve or something else. Here’s the whole flight. One of the questions we get most often is “should I have seen this in the data before the event?” In this case the answer is yeah, there’s something going on with cyl 4 before takeoff, but it settles down at takeoff and the EGT 4 trace just before the event at the 21 min mark looks pretty normal. And then all of a sudden it’s a five cylinder engine. And it gets worse at the 28 min mark when cyl 5 drops out – no hint of trouble from 5 in the earlier data. Here’s a picture of the push rod tubes for cyl 4 taken after the successful forced landing. In part one, I built a table for each sticky valve incident. Here’s the table for this one. Engine Model Cyl# Length of Event (mins) Drop in CHT? Drop in TIT? RPM fluctuation? Oil Temp […]

It has been a while since we took a look at sticky valves. I’m not going to write about why valves stick and how to keep it from happening, although I have a great resource for that. Earlier this year Mike Busch wrote an article for AOPA Pilot called Why Valves Stick. And here’s a link to his EAA webinar on the same subject. I’m also not going to write about how to fix a sticky valve, although I have a great resource for that too. Here’s Paul New’s article about Lycoming exhaust valves with references to Lycoming’s Service Bulletins and Instructions. This Puzzler is about what it looks like on your engine monitor when a valve sticks, so you can spot it in real time as it happens, or spot it as you review your data after a flight. Our eventual goal is to see if there’s some clue in the data leading up to these events that could prevent them from occurring. We’re not there yet but it’s a good project for machine learning. In the sprit of good puzzling, there are some verified examples of sticky valves, but not all of the examples are sticky valves. Ground […]