Avgas Aircraft Engines, I
The last couple of years development in aircraft engines has been more or less concentrating on diesel engines. We have seen one off installations to fully developed production lines.
A number of companies are active on this market primarily due to major concern of long term availability and the relative high price of AVgas (Europe). Which makes sense as Jet fuel is available everywhere, even in places where AVgas is not and has to be flown in.
But there are still a lot of AVgas engines manufactured and consequently bought and installed by certified and kit aircraft builders. So its obvious we are going to spend some time with Lycoming and Continental engines.
Ongoing developments in new aviation gasoline fuels, subsystems and FADEC engine propeller control will make sure that these engines will be flying for years to come.
And as perfectly said by Lycoming: Some engines purr like kittens. These roar!
A number of manufacturers are still producing engines running on AVgas. Lycoming, Continental are the most common names. There are also a number of companies producing Lycoming look-a-like engines. These firms took the original design and improved upon that. They use technologies known in automotive engines for years like: multipoint FADEC controlled fuel injection, roller tappets, different, stronger and corrosion resistant alloys and such.
Initially these engines were developed for the experimental aircraft market. Testing new developments was (and still is) relatively easy and flight time and experience in these 'new' designs can be build quite rapidly. And at long last we see these improvements in technology being incorporated in the certified market too.
Roller Tappets in action
A good example: roller tappets. These eliminate the sliding friction between the cam and valve tappet by incorporating a ball bearing in the tappet to reduce friction and increase durability. Another one is electronic ignition and FADEC.
In comparison, these engines are slow turning (max 2700 RPM), big bore pistons, are direct drive engines with high torque. Where as others run higher revolutions (around 4000-6000 RPM) to create power and must use a gearbox to drive the propeller and regain torque from revolutions.
Lycoming, a Textron Company located in Williamsport, PA has been producing aircraft engines since 1929 when they initially build a 9-cylinder radial R-680. About 25000 of these beautiful engines were built and used in Stinson to Stearman aircraft, some of these engines are still flying today.
4, 6 and 8 cylinders
Lycomings are sold in four, six and eight cylinders versions with or without fuel injection, turbo and geared types (for the left turning types in twin aircraft). The four cylinder versions are 235, 320, 360 and 390 cubic inch, with a power output range of 118 to 210 bhp. The six cylinder versions are 540 and 580 cubic inch with power outputs ranging from 235 to 350 bhp (540) and 315 bhp for the 580, and the eight cylinder is 720 cu.in with 400 bhp. For exact details we refer you to the website of Lycoming Textron or one of the files below.
Lycoming started in 2008 to certify its engines to run on Mogas: "Lycoming Engines announced an unleaded automotive gasoline approval program for its standard compression ratio O-360 and IO-360 product lines. Unleaded 93 AKI automotive gasoline conforming to either Euro Norm EN228 or ASTM D4814 will be the basis of this Lycoming specified fuel.", according to Diesel Air Newsletter.
In 2009 Lycoming announced the arrival of three new engines: the IO-233 for the light sport aircraft (LSA) market, the TIO-360-EXP for the experimental market and the TEO-540-A1A for the Lancair Evolution aircraft. Available in 2011.
The IO-233 is a lightweight, electronic ignition fuel injected heavily modified O-235 (weighs some 45 lbs less) and has 100 bhp at 2400 RPM, the TIO-360-EXP is a turbo normalized, 180 bhp fuel injected capable of running on AV and mogas.
The TEO-540-A1A is controlled by a state of the art electronic fuel injection FADEC which is single lever, with knock detection, turbo and propeller control, common rail fuel system and electronic injectors. More in our Lycoming IE2 Engine article.