"Micromaster"-- Centerline twin using small industrial engines


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Well-Known Member
Lifetime Supporter
Jan 24, 2011
Just to re-iterate.

In my interpretation this does not exclude two or more seats. I see that you could have two or more seats and (1) get instruction from a qualified instructor or (2) fly solo.
Right, but what you or I think doesn't seem to matter much.
Regarding a single-seat twin: The important thing is what the DAR writes into the operating limitations when the airworthiness certificate is issued. From what the EAA has seen with Cri-Cris (another single-seat twin), it could go either way. I didn't get a reply back from Kitplanes magazine (I noticed that the "ask the DAR" column is not in the latest edition--maybe Mel isn't writing for them anymore). I probably need to follow this up with the FAA or a DAR (hopefully a really young one who might still be in service if I ever finish building a twin aircraft!)
Regarding two-seats: I agree with you--there's no special treatment for E-AB multi engine aircraft if you are flying passengers: If you fly with a passenger, you'll need an MEL rating. IIRC, it is permissible to use the E-AB for your own instruction (if you can find an instructor willing to do that). At the end of the multiengine instruction in your own MicroMaster, you'd certainly be better trained to fly it than if you'd gotten the training in an old Aztec.
There's no way a 2-engine Micromaster with 30 HP engines and two people aboard would be able to climb with one engine out. It's probably very feasible to design a triple with engines this size (or even smaller) and two seats that could climb with one engine out (we did some thinking about this before). Now, a BeetleMaster (with two seats and two 75HP VW engines) looks like it could climb safely on just one, and be a very good performer with both engines running and (approx 1600 to 1700 lbs MTOW)

Dan Thomas

Well-Known Member
Sep 17, 2008
A turbine only burns something like 20% of the air that goes in the intake under normal conditions. Any extra air you can cram in contributes to cooling and as most turbines are temp limited it means you can squeeze out more power.
Yup, around 25% for combustion, and the rest for cooling. The flame in the combustors has to be kept away from the metal, so there are many points of entry for the air to form a cushion between the flame and metal. The turbine rotor blades and guide vanes are usually drilled for air passages, to cool them and provide a layer of air between them and the hot gases.

Besides all that, the engine nacelle has to be kept cool, and on airplanes like the P3 (I worked on Lockheed Electras for a time) the long exhaust duct is in a housing atop the wing and has cooling air flowing through it. All that is from the prop.