Modern Aircraft Engines

High Performance Aviation

June 9, 2022

When you look at the different types of engines today the designation of the engine can leave you wondering what they mean. For instance, Lycoming has a TIO-540-AJ1A engine rated at 310 BHP, and Continental has a TSIO-550-C engine, which is also rated at 310 BHP. These numbers are very different and to the manufacturer, it has a particular meaning under the Type Certificate issued by the FAA. In the mix, there are radial engines, horizontally opposed, in-line, Diesel, and V-style engines. Within this mix, there is normally aspirated, turbo normalized, turbocharged, supercharged, and turbo supercharged.

Let’s look at some definitions that will help us to get an understanding of the different types of engines.

Radial Engine:
The Radial engine is an internal combustion engine that has the cylinders radiating out from the center, forming a circle like the spokes on a wagon wheel. Mostly these engines are used on agricultural, old warbirds, and experimental planes.

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V Style Engines:
The V style engine is a modified version of V 8’s in cars that are mostly installed per an STC. The most notable is the Orenda V8 conversion installed on the Aero Commanders. Older V engines include the Wright Hispano-Suiza H, RAF-1a, and Curtiss OX-5 V-8. Most of these were liquid-cooled and do not have very extensive use in general aviation today. See below.

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Inline Engines:
Probably the most famous inline aircraft engine is the Rolls-Royce Merlin, inline Supermarine used on the Spitfire, and the P-51 Mustang. De Havilland produced the Gipsy Six developed by the British and used on pre-WW II aircraft. Like the V style engines, these engines are not used in modern manufactured aircraft. Sethe e examples below.

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Diesel Engines:
Diesel engines in aircraft are not a new concept, they have been around for quite a while. The new modern Diesel is much lighter, uses FADEC for the most part, and is very reliable. The most notable company that has had success with diesel engines is Diamond Aircraft. Their latest addition to the market is the DA50 RG ( which uses the Continental CD-300 FADEC-controlled engine boosting 300 HP max. Diesels come in 4, and 6 cylinders, mostly using a split rail fuel injection, turbocharged setup. This very well could be the future of general aviation and is the only choice for countries that are unable to sell, produce or import 100LL. See the examples below.

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Horizontally Opposed:
The most widely used engines in general aviation is the horizontally opposed. These engines are better known as the Opposed Engine. In the Designator IO-540 engine, the O after the I stands for opposed. Both Continental and Lycoming manufacture most of the opposed engines that you find in general aviation aircraft. They range in 4, 6, and 8 cylinders and come in normally aspirated, turbo charged, turbo normalized, and turbo supercharged.

Normally Aspirated:
An engine that does not compensate for decreases in atmospheric pressure through turbocharging or other means.

Turbocharged/Turbo Supercharged:
Turbo Supercharged and Turbocharged engines maintain above sea level atmospheric pressure in the intake of the engine.

Turbo Normalized:
A turbo-normalization system automatically limits manifold pressure to that at sea level at all altitudes up to the system critical altitude.

Supercharged Engines:
Super charged engines use gears, belts, or electric motors to drive an impellor to increase atmospheric pressure in the intake of the engine.

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Engine Designation Codes
Continental Motors uses the following codes to designate models: Engine Specification Numbers (

For instance: GTSIO-520-N1B


TS=Turbo Super Charged

I=Fuel Injected

O=Horizontally Opposed

520=Displacement in cubic inches

N=Model, Some engine models may be multi-digit

1=Specification Number, may be enclosed in parenthesis

B= Shipping designation, B is wood craft, F is factory packaging

Additional codes for gasoline/Diesel Continetal Engines:

L=Left-hand rotation

L=Can also indicate Liquid Cooled, Example TSIOL-550C

F-FADEC equipped engine

TD=Turbo Super Charged Diesel

Lycoming Disignation codes: CERTIFICATED (

Example: AEIO-540-L1B5D

A=Aerobatic (dry sump)

AE=Aerobatic Engine



H=Horizontal Helicopter

I=Fuel Injected

L=Left Hand Rotation Crankshaft


O=Opposed Cylinders



V=Vertical Helicopter

540=Cubic Inch Displacement

235, 290, 320, 340, 360, and 390 are 4-cylinder engines

435, 480, 540, and 580 are 6-cylinder engines

720 is an 8-cylinder engine

541 is a 6-cylinder engine with integral accessory

L=Indicated change in power section and rating from original design

1=Indicates Nose Section (2nd and 3rd suffix character)

B=Indicates accessory section (3rd and 4th suffix character)

5=Indicates counterweight application (if used, 4th or 5th suffix character)

D=Indicates Dual Magneto (if used, 4th or 5th suffix character)

Lycoming SSP-110-2 goes in to allot more detail (CERTIFICATED ( but hopefully, this brief overview of engines will take some of the mystery out of what all those numbers mean.

Picture Credits:

Aero Engine – Rolls-Royce Ltd, Merlin 46, V-12 Inline, Supermarine Spitfire Vc, Derby, England, 1942 (




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