Hobbs vs Tach Time & SMOH — Aircraft Engine Hours Explained

Hobbs vs Tach Time & SMOH — Aircraft Engine Hours Explained

Mixing up hobsmeter time and tach time is one of the most common sources of confusion in aircraft maintenance records -- and when it goes unresolved, it costs owners money and obscures the real condition of the engine.John breaks down the difference between the two gauges, why they're not interchangeable, and what happens when a mechanic or owner has been flip-flopping between them for years without documenting which one was used. The tachometer measures engine use; the hobs measures how long the master switch has been on. For maintenance purposes, tach time is what drives decisions about overhaul intervals and AD compliance. Jeff explains what to do when a gauge is replaced, fails, or doesn't match prior entries -- and why "estimated" and "unknown" are legitimate and important entries when the true time can't be substantiated. Leaving a time gap unexplained is far worse than flagging it accurately.The conversation gets into time since major overhaul (SMOH) and total time since new (TSN) -- what both mean, how to read them on an overhauled engine versus a first-run engine, and what a remanufactured engine serial number actually tells you. John explains why knowing SMOH is the most critical number when deciding whether to repair or fully overhaul an engine, and what the Continental and Lycoming recommended intervals actually represent.In this episode, we cover:- The functional difference between a tachometer and a hobsmeter -- and which one to use for engine maintenance- Why flipping between tach and hobs time in logbook entries creates confusion and red flags- What to document when a gauge is replaced or fails mid-ownership- When to write "estimated" or "unknown" in a logbook entry -- and why that is the right call- Time since major overhaul (SMOH) vs. total time since new (TSN) -- how to read both- What a remanufactured engine serial number means for Continental and Lycoming engines- Why high total time since new is not the same as a worn-out engine- How SMOH drives repair vs. overhaul decisions at Signature Engines00:00:41 Introduction -- why tach vs. hobs matters00:02:41 How entries should note time and which gauge to use00:05:27 What to do when you only have one gauge00:06:50 Documenting gauge replacements and time gaps in the logbook00:09:21 When "estimated" and "unknown" belong in a logbook entry00:10:30 Time since major overhaul vs. total time since new00:13:27 Remanufactured vs. overhauled -- what zero-time actually means00:16:12 How many times can an engine be overhauled?Get in touch!Web - SignatureEngines.comEmail - Podcast@SignatureEngines.comYouTube - https://www.youtube.com/channel/UCfaCQMkJRkLQ-MUg2kwHy2A

Engine Logbook vs Airframe Logbook — What Belongs in Each

Incomplete or vague logbook entries don't just cost you money at resale -- they can expose you to liability for work done on an aircraft you haven't owned in a decade. John and Jeff walk through how aviation logbooks actually work: the three types (pilot, airframe, engine), what entries should say and why, and the red flags that tell an experienced mechanic something went sideways. They explain the difference between "engine removed for inspection" and an entry that actually tells you what happened -- and why that difference matters when you're the next buyer, the inspector signing it off, or the previous owner when someone gets hurt. Jeff describes a recurring pattern he sees on pre-buy inspections: engines with entries that say just enough to look compliant but leave the real story out. John explains why owners sometimes push mechanics to document less -- and why that strategy backfires.The episode gets specific about what pilots and owners are actually responsible for. Airworthiness directives, their recurring intervals, and how to read an AD list vs. a blanket "all ADs complied with" sign-off. What belongs in the aircraft during flight versus what should stay in a safe. The difference between a prop strike that was handled correctly and one that was quietly buried. And the concept of vicarious liability -- why your documentation obligation doesn't end when you sell the plane.In this episode, we cover:- The three types of aviation logbooks and what each one should contain- Why "engine removed and reinstalled" is one of the biggest red flags in any logbook- How to spot a prop strike or sudden stoppage that wasn't properly addressed in the records- What AD compliance entries should actually say vs. the generic sign-offs that hide problems- Why owners sometimes push for minimal documentation -- and the liability exposure that creates- The difference between records you must carry in flight and original documents that belong in a safe- How vicarious liability works in aviation and why it can follow a previous owner for 10-20 years- What a well-organized logbook looks like to a mechanic walking in cold for a pre-buy00:00:31 Introduction -- logbook confusion and the three types00:03:37 What mechanics look for on pre-buy inspections00:05:30 Why minimal documentation is a liability trap00:08:06 How ADs reference historical maintenance and why complete records matter00:09:09 What to keep in the aircraft vs. what to store safely00:13:16 Vicarious liability -- your obligation doesn't end at sale00:16:43 The inspector as last line of defense -- when work can't be signed offGet in touch!Web - SignatureEngines.comEmail - Podcast@SignatureEngines.comYouTube - https://www.youtube.com/channel/UCfaCQMkJRkLQ-MUg2kwHy2A

Is Your Checklist Actually Protecting Your Engine?

Send us questions by commenting below or emailing John & Jeff at: Podcast@SignatureEngines.com Is Your Checklist Actually Protecting Your Engine? Following your aircraft checklist isn't optional — and skipping a single step like mixture full rich on takeoff can send cylinder head temperatures past 400° before you've leveled off. John and Jeff walk through the checklist habits that actually protect your piston engine. In this episode, John Buckles and Jeff Schanbel talk through the operating checklist the way two mechanics see it from the shop floor — not as paperwork, but as the difference between a healthy engine and a damaged one. They cover why leaning the mixture during taxi keeps spark plugs from carbon fouling, why pushing the mixture full rich before takeoff is the step pilots forget most often, and what high CHT on climb is really telling you. They also get into engine startup discipline, why running up to high RPM right after start beats up the engine, and why turbocharged airplanes need cooldown time at idle before shutdown — not a quick mag check and mixture cut. The bigger theme: most of the engine problems they see trace back to pilots being in a hurry. Move controls slowly, monitor the engine the same way you monitor your flight instruments, and if temperatures or pressures start climbing on takeoff, level off and troubleshoot before pressing on to altitude. You don't have to declare an emergency to tell ATC you need to stay low and sort something out. In this episode, we cover: - Why mixture full rich is the checklist item pilots most often miss before takeoff - How a missed mixture step can push CHT over 400° in a fast climb - Why leaning during taxi reduces spark plug fouling and carbon buildup - What to do when CHT or oil pressure starts climbing during initial climb - How to talk to ATC about leveling off without declaring an emergency - Why high-RPM operation right after startup damages the engine - Why turbocharged engines need idle time before shutdown - The checklist habits that prevent gear-up landings and engine damage alike This one is for owners and pilots who want their engine to make TBO — and who know that the checklist hanging in the cockpit is the cheapest maintenance tool they own. TIMECODES 00:00 The checklist step pilots skip most often 00:32 What to review before you start the engine 01:16 Why mixture full rich before takeoff matters 01:52 How fast CHT climbs past 400° when you forget 02:14 Don't assume you know the checklist — read it every time 02:40 Why rushing the shutdown damages your engine 03:35 Gear-up landings, GUMPS, and why checklists exist 03:53 Move engine controls slowly, every time 04:14 Turbocharger cooldown before shutdown 04:49 If temps rise on climb, level off and assess 05:20 Monitor the engine like you monitor your instruments 06:03 Telling ATC you need to level off without declaring an emergency Get in touch! Web - SignatureEngines.com Email - Podcast@SignatureEngines.com YouTube - youtube.com/@SignatureEnginesInc

How to Keep a Post-Flight Discrepancy Log

Send us questions by commenting below or emailing John & Jeff at: Podcast@SignatureEngines.com How to Keep a Post-Flight Discrepancy Log Most engine problems don't show up overnight — they trend. Keeping a simple post-flight discrepancy log is how you catch them before they ground you, or worse. John and Jeff walk through the habit they wish every owner and pilot would adopt: at the end of every flight, write down what you noticed. A new noise, a vibration, a temperature that ran a little higher than normal — or nothing at all. Even "none noted" with the date and your initials is worth writing, because it gives the next pilot and your mechanic a baseline to compare against. The guys explain why this matters most on aircraft with multiple pilots, where nobody wants to be the one to "make it a thing," and how that silence lets small issues turn into expensive ones. Jeff shares a real example: a young pilot who heard a popping sound out of the left engine for about two months and brushed it off — until they pulled the cowling and found an exhaust stack hanging an inch and a half loose. Hot exhaust gases that close to a wiring harness can melt insulation and kill power to the engine, and a stack that fully breaks loose becomes a hazard on the ground. The fix, caught early, would have taken minutes. By the time it was found, it was a near miss. The episode is about building the awareness and the paper trail that catches problems while they're still cheap. In this episode, we cover: - Why a written post-flight squawk log beats relying on memory - What to write when nothing went wrong (and why "none noted" matters) - How trending small symptoms reveals real engine problems - The communication gap on multi-pilot aircraft, and how to close it - A real-world case: a popping sound that was a hanging exhaust stack - What can go wrong when an exhaust stack hangs near a wiring harness - Why looping in your mechanic — or another mechanic — pays off - How to give your A&P the history they need to actually diagnose an issue If you fly behind a piston engine, this is one of the cheapest habits you can build to keep your airplane airworthy and yourself safe. TIMECODES 00:00 The post-flight habit nobody wants to do 00:27 Why "I think I felt this 3 months ago" is too late 01:18 What to write down — even when nothing happened 02:08 The multi-pilot communication problem 03:23 The popping sound that was a hanging exhaust stack 05:16 What a loose exhaust stack can actually do to your engine 06:00 Call your mechanic — or another mechanic Get in touch! Web - SignatureEngines.com Email - Podcast@SignatureEngines.com YouTube - youtube.com/@SignatureEnginesInc

How to Preflight a Piston Engine the Right Way

Send us questions by commenting below or emailing John & Jeff at: Podcast@SignatureEngines.com How to Preflight a Piston Engine the Right Way A real preflight inspection is more than opening the oil door and checking the dipstick. John and Jeff walk through what they actually look for before every flight — and what most pilots miss. Vibration is the number one enemy of a piston aircraft. Motor mounts crack, components loosen, and parts break between flights. A magneto that ran fine yesterday can be dead today. You won't catch all of it on a walkaround, but you'll catch a lot more than you think if you slow down and know where to look. John and Jeff start under the aircraft — looking for fresh oil, fuel, or hydraulic leaks on the ramp or hangar floor — then work up through the cowl, the propeller, the intakes, and the belly. They talk through the bird nests and mud dauber nests that show up after the plane sits, why a piece of cardboard under the airplane is one of the cheapest diagnostic tools an owner can have, and why a constant-speed propeller deserves more than a glance. Then they move into the cockpit, where checking the throttle, mixture, and prop control for freedom of movement before start can flag a problem before you ever turn the key. In this episode, we cover: - Why looking under the aircraft is the first step, not the oil door - How to tell normal seepage from a developing leak using a piece of cardboard on the hangar floor - What mud daubers and birds get into — breather tubes, carb intakes, pitot — and how to spot the trail - Why you should open the cowl when you can, and what to look for when it's open - How to check a constant-speed propeller for leaks and security on preflight - Why the windscreen, nav lights, and landing lights matter even on a day VFR flight - What a sticky throttle, mixture, or prop control can tell you before engine start - Why a magneto can fail between flights and how the runup catches what the walkaround can't A thorough preflight inspection is the cheapest insurance an owner has — and the difference between catching a problem on the ramp or finding it in the air. TIMECODES 00:00 The preflight habits that separate good pilots from bad ones 00:36 Why most pilots only check the oil and stop there 01:02 Start under the aircraft: looking for oil, fuel, and gear leaks 01:21 Open the cowl when you can — what breaks between flights 02:12 Vibration, motor mounts, and why piston aircraft parts fail 02:31 Inspecting the propeller and checking the intakes for nests 03:00 Mud daubers, birds, and what shows up after the plane sits 04:11 Using cardboard under the aircraft to track leaks over time 04:54 Don't skip the windscreen, nav lights, and landing lights 05:28 In-cockpit preflight: throttle, mixture, and prop control freedom Get in touch! Web - SignatureEngines.com Email - Podcast@SignatureEngines.com YouTube - youtube.com/@SignatureEnginesInc