Explore Engines
Aircraft Engines Explained
The engine is the heart of any airplane — and the single biggest factor in what it costs to buy, own, and operate. Whether you're a first-time buyer or experienced owner, understanding engines will save you thousands.
Engine Types: What the Letters Mean
Aircraft piston engines come in four main configurations. Understanding the differences helps you evaluate what you need — and what you're paying for.
Carbureted
Prefix: O-The simplest and oldest fuel delivery system. A carburetor mixes fuel and air mechanically before it enters the cylinders. Reliable and easy to maintain, but susceptible to carburetor icing in certain weather conditions.
Advantages
- ✓ Simple, fewer parts to fail
- ✓ Lower maintenance costs
- ✓ Well-understood by all mechanics
- ✓ Easier cold-weather starting
Considerations
- • Susceptible to carb ice (requires carb heat management)
- • Less precise fuel metering
- • Slightly higher fuel consumption
- • Altitude compensation is manual (mixture leaning)
Buyer's Tip: Carbureted engines are perfectly fine for VFR flying and local trips. Many training aircraft and simple four-seaters use them. Just learn proper carb heat and mixture management.
Fuel Injected
Prefix: IO-Fuel is metered and delivered directly to each cylinder through individual injector nozzles. More precise fuel delivery means better efficiency, smoother operation, and no carb ice risk. Standard on most higher-performance engines.
Advantages
- ✓ No carburetor ice risk
- ✓ More precise fuel metering = better efficiency
- ✓ Smoother power delivery
- ✓ Better high-altitude performance
Considerations
- • Harder hot starts (vapor lock in fuel lines)
- • More complex fuel system
- • Slightly higher maintenance cost
- • Requires understanding of fuel flow management
Buyer's Tip: Fuel injection is standard on most 200+ HP engines. The hot-start challenge is manageable once you learn the technique for your specific engine. Many owners consider it a non-issue.
Turbocharged
Prefix: TIO- / TSIO-An exhaust-driven turbocharger compresses intake air, allowing the engine to maintain sea-level power output at higher altitudes. Essential for flying above 12,000–14,000 feet or operating from high-elevation airports.
Advantages
- ✓ Maintain full power at altitude
- ✓ Higher true airspeeds at cruise altitudes
- ✓ Better climb performance in hot/high conditions
- ✓ Access to higher (smoother, faster) flight levels
Considerations
- • Higher purchase price and overhaul cost
- • More complex systems to maintain
- • Lower TBO on some models
- • Requires careful temperature management (CHT/TIT)
Buyer's Tip: Unless you regularly fly above 12,000 feet, fly over mountains, or operate from high-elevation airports, you may not need turbocharging. The added cost and complexity are real. But if you do need it, nothing else substitutes.
Turbonormalized
Prefix: Various (aftermarket)A turbocharger calibrated to restore sea-level power at altitude — but not to boost beyond the engine's normally-aspirated rating. This gives altitude performance without the stress of overboosting. Popular as aftermarket modifications.
Advantages
- ✓ Altitude performance without overboosting
- ✓ Engine runs at or below normal stress levels
- ✓ Often maintains standard TBO
- ✓ Popular proven aftermarket STCs (Tornado Alley, RCM)
Considerations
- • Still adds turbo system complexity
- • Aftermarket cost $30K–$60K installed
- • Not available for all engine models
- • Adds weight
Buyer's Tip: Turbonormalizing is a sweet spot for many owners — altitude capability without the downsides of full turbocharging. If you find an airplane with a quality turbonormalizing STC already installed, that can add real value.
How to Read an Engine Model Number
Every letter and number tells you something
Example
Common Engine Families
| Engine | Horsepower | Common Aircraft |
|---|---|---|
| O-235 | 108–118 HP | Two-seat trainers (Cessna 150, Grumman AA-1) |
| O-320 | 150–160 HP | Four-seat standards (Cherokee, Skyhawk, Cheetah, Tiger) |
| O-360 / IO-360 | 180–200 HP | The GA workhorse (172SP, Archer, Tiger, TB-10/20) |
| IO-390 | 210 HP | Modern replacement for IO-360 (Cirrus SR20, new Cessnas) |
| IO-540 | 250–300 HP | Six-cylinder power (Bonanza, Saratoga, Trinidad, Commander 114) |
| IO-550 / IO-580 | 300–315 HP | High-performance (Bonanza, Cirrus SR22, Mooney Acclaim) |
| TSIO-550 | 310–350 HP | Turbocharged six-cylinder (Malibu, Mooney, Cessna T206) |
Understanding Engine Time
The single biggest factor in aircraft pricing
Two identical airplanes — same year, same model, same avionics — can be $50,000 to $80,000 apart in price based purely on engine time. Understanding how engine time works is essential before you shop.
Time Between Overhauls
The manufacturer's recommended maximum hours before a major overhaul. Not a hard limit for Part 91 (private) operations, but exceeding TBO affects insurance and resale value.
Example: A Lycoming IO-540 has a 2,000-hour TBO. At 200 hours/year, that's 10 years between overhauls.
Since Major Overhaul
Hours flown since the engine's last major overhaul by a qualified shop. The engine retains its total-time history.
Example: An engine with 3,450 TT and 450 SMOH was overhauled at 3,000 hours and has flown 450 since.
Since Factory Remanufacture
Hours since the engine was remanufactured at the original factory (Lycoming or Continental). A factory reman gets a zero-time logbook — it's legally a new engine.
Example: A factory reman Lycoming with 200 SFRM is essentially a 200-hour engine with a new logbook.
Since Top Overhaul
Hours since the top end (cylinders, pistons, valves) was overhauled without a full teardown of the crankcase. A top overhaul does not reset time toward TBO.
Example: An engine at 1,400 SMOH with 200 STOH means the cylinders were refreshed but the bottom end has 1,400 hours.
How Engine Time Affects Price
Overhaul, Remanufacture, or Top Overhaul?
When an engine reaches TBO or has issues, you have three main options. Each has different costs, outcomes, and implications for resale value.
Factory Remanufactured
Lycoming or Continental factory only
The engine is returned to the original manufacturer, completely disassembled, and rebuilt to new tolerances using a mix of new and serviceable parts. The engine receives a zero-time logbook — legally, it's a new engine.
Pros
- ✓ Zero-time logbook (highest resale value)
- ✓ Factory warranty (typically 2 years / unlimited hours)
- ✓ New limits and tolerances throughout
- ✓ Built by the people who designed it
Cons
- • Most expensive option
- • Longer turnaround (8–16 weeks typical)
- • Core exchange may be required
- • You get back a different engine (not your original)
Best for: Owners planning to keep the airplane long-term, or sellers wanting maximum resale value.
Field Overhaul (Major Overhaul)
Qualified overhaul shops (Certified Repair Stations)
A qualified shop completely disassembles your specific engine, inspects all parts, replaces what's worn to service limits, and reassembles. The engine retains its total time but hours are reset to "0 SMOH."
Pros
- ✓ Less expensive than factory reman
- ✓ You get your own engine back
- ✓ Can specify new cylinders, cam, etc.
- ✓ Good shops produce excellent results
Cons
- • No zero-time logbook
- • Quality varies significantly between shops
- • Warranty varies (typically 1 year)
- • Requires careful shop selection
Best for: Most owners — especially with a reputable, well-reviewed overhaul shop.
Top Overhaul
Any qualified A&P mechanic or shop
Only the "top end" is overhauled — cylinders are removed, inspected or replaced, pistons/rings replaced, valves reground. The crankcase, crankshaft, camshaft, and bearings are not touched.
Pros
- ✓ Much less expensive
- ✓ Addresses the most common wear items
- ✓ Can extend useful life significantly
- ✓ Faster turnaround
Cons
- • Does NOT reset time toward TBO
- • Does not address bottom-end wear
- • May mask deeper issues
- • Some buyers/insurers view skeptically
Best for: Engines with specific cylinder issues (low compression, damage) but healthy bottom ends.
Pre-Buy Engine Inspection Checklist
Before you buy any airplane, the engine needs a thorough evaluation. Here's what to look at — and what to ask.
Compression Check
All cylinders should be 70/80 or better (differential compression). Any cylinder below 60/80 is a concern. Ask for the specific numbers, not just "all good."
Oil Analysis History
Request the last 5–10 oil analysis reports. Look for trends, not single readings. Rising metal content (iron, chrome, nickel) suggests internal wear.
Logbook Continuity
Ensure the engine logbook is complete from new or last overhaul with no gaps. Missing entries are a red flag — you don't know what was or wasn't done.
AD Compliance
Verify all Airworthiness Directives for the specific engine model have been complied with and documented. Your mechanic should check this.
Oil Consumption
Ask the owner about oil consumption rate. A quart every 8–10 hours is normal for many engines. A quart every 3–4 hours suggests cylinder wear.
Borescope Inspection
A camera inspection of cylinder interiors reveals valve condition, scoring, corrosion, and carbon buildup without removing cylinders. Standard in any serious pre-buy.
Time in Service vs. Calendar
An engine with 500 hours in 15 years may have more corrosion than one with 1,500 hours in 5 years. Engines that sit deteriorate. Regular flying is healthy.
Engine Manufacturers
The companies that power general aviation.
Lycoming Engines
Piston — 108 to 400+ HP
The most common piston engine in general aviation. Lycoming powers the majority of Piper, Grumman, Mooney, Cirrus, SOCATA, and many Cessna aircraft. Known for robust, reliable horizontally-opposed four- and six-cylinder engines from 108 to 400+ HP.
https://www.lycoming.com →
Continental Aerospace Technologies
Piston & Diesel — 100 to 550+ HP
Powers most Cessna singles, Beechcraft models, and many Mooney aircraft. Continental recently expanded into Jet-A piston engines (CD-series diesel) for the European and global markets. Now Chinese-owned (AVIC).
https://www.continentalaerospace.com →
Rotax (BRP)
Piston — 80 to 141 HP
The dominant engine in Light Sport Aircraft and modern two-seat trainers. Austrian-built, the Rotax 912/914/915 series are lightweight, fuel-efficient, and can run on auto fuel. Increasingly found in certified aircraft (Tecnam, Flight Design, Pipistrel).
https://www.flyrotax.com →
Pratt & Whitney Canada
Turboprop — 500 to 2,000+ SHP
Powers the majority of single-engine turboprops including the Pilatus PC-12, Daher TBM series, and Cessna Caravan. The PT6A is arguably the most successful turboprop engine ever produced — over 51,000 built.
https://www.pwc.ca →
Honeywell (formerly Garrett/AlliedSignal)
Turboprop — 575 to 1,600+ SHP
Produces the TPE331 turboprop engine series found in Mitsubishi MU-2, Fairchild Merlin, and various Aerostar conversions. Also manufactures auxiliary power units and turbofan engines for larger aircraft.
https://aerospace.honeywell.com →
Engine Operating Costs by Horsepower
What does it actually cost per hour to run an engine? Fuel is the obvious cost, but smart owners also reserve money toward the eventual overhaul.
Based on avgas at ~$6.00/gallon. Overhaul reserve = estimated overhaul cost ÷ TBO hours.
| HP Class | Example Aircraft | Fuel Burn | Overhaul Reserve | Fuel Cost | Total Engine $/hr |
|---|---|---|---|---|---|
| 108–120 HP | Cessna 150, Grumman AA-1 | 6–7 GPH | $12–15/hr | $36–42/hr | $48–57/hr |
| 150–160 HP | Cessna 172, Cherokee, Cheetah | 8–9 GPH | $14–18/hr | $48–54/hr | $62–72/hr |
| 180 HP | Cessna 182, Tiger, Archer III | 9–11 GPH | $16–20/hr | $54–66/hr | $70–86/hr |
| 200–260 HP | Bonanza, Commander 114, Trinidad | 12–15 GPH | $20–28/hr | $72–90/hr | $92–118/hr |
| 300+ HP (Piston) | Cirrus SR22T, Bonanza A36 | 14–18 GPH | $25–35/hr | $84–108/hr | $109–143/hr |
| Turboprop | TBM, PC-12, Caravan | 30–60 GPH (Jet-A) | $50–100/hr | $150–300/hr | $200–400/hr |
Important: These are engine costs only. Total hourly operating cost also includes insurance, hangar, annual inspection, maintenance reserves, and other fixed costs. Engine costs typically represent 40–60% of total hourly operating expense.
Ready to Find Your Airplane?
Now that you understand engines, explore aircraft by type or browse by manufacturer.