Retrotechtacular: The US Air Force Has The Biggest Fleet

When it comes to the superlatives of aviation, there are aircraft larger than the C-5 Galaxy. [Howard Hughes]’s Spruce Goose has the largest wingspan, and the Soviet and now Ukranian Antonov AN-225 Mriya has the largest cargo capacity. When it flies in the next year or so, Scaled Composites Stratolaunch – a twin-hulled beast of a plane designed to haul rockets up to 30,000 feet – will be the aircraft with the largest wingspan and the greatest cargo capacity.

These superlatives, while completely accurate, fail to realize these huge planes are one of a kind. There is no plan to build a second Stratolaunch, and the second airframe for the AN-225 is rusting away in a field. If you want to find a fleet of enormous aircraft, there’s only one contender: the C5 Galaxy, the largest plane in the US Air Force inventory.

This video, from the USAF Archives circa 1968, goes over the design, construction, and operation of the C5 Galaxy. It covers the program beginnings, the shortcomings of earlier aircraft, and – of course – completely disregards the initial problems of the C5.

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3D Printed Turbofan Features Reverse Thrust

[Harcoreta] has created a 3D printed model of the GE GEnx-1B Turbofan. This is the engine that powers Boeing’s 787 dreamliner. What sets this model apart is that it has a complete working reverse thrust system. A real jet engine would be asking a bit much of 3D printed ABS plastic. This model is more of an Electric Ducted Fan (EDF). An NTM 1400kv 35mm brushless motor hides in the core, cooled by a small impeller.

jet-nakedWhat sets this apart from other jet models is the working reverse thrust system. [Harcoreta] painstakingly modeled the cascade reverse thrust setup on the 787/GEnx-1B combo. He then engineered a way to make it actually work using radio controlled plane components. Two servos drive threaded rods. The rods move the rear engine cowling, exposing the reverse thrust ducts. The servos also drive a complex series of linkages. These linkages actuate cascade vanes which close off the fan exhaust. The air driven by the fan has nowhere to go but out the reverse thrust ducts. [Harcoreta’s] videos do a much better job of explaining how all the parts work together.

The model was printed on an Reprap Prusa I3 at 0.1mm layer height. [Harcoreta] smoothed his prints using acrylic thinner, similar to the acetone vapor method. Unfortunately, [Harcoreta] has only released a few of the design files on rcgroups, but we’re hoping he will drop the whole model. We can’t wait to see a model dreamliner landing just like the big boys!

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3D Printed Cutaway Jet Engine Sounds Great

Thanks to the wonders of 3D printing, you can now have a 3D printed a jet engine of your very own. Unlike jet engines we’ve seen before, this one comes with no chance of the operator getting burned to a crisp. [Gerry] is a self-proclaimed “broken down motor mechanic” from New Zealand. He’s designed a rather awesome jet engine in 3D Software, and printed it on his UP Plus printer. The engine itself is a cutaway model of a high-bypass turbofan engine. While we’re not sure which make and model of jet engine this cutaway represents, we’re still very impressed.

This isn’t just a static display model – the engine will actually spin up with the help of compressed air.  Separate start and run tubes send air to the turbine and main fain respectively. It even has that distinctive turbofan “buzz saw” sound. While this model is relatively safe, [Gerry] does warn to keep the pressure down, or it could come apart. To that end we’d recommend adding a regulator before the quick disconnect.

The Thingiverse project is a bit light on instructions.  However this situation is remedied by [hacksaw], who posted a pictorial and build log up on pp3d. [Hacksaw] did run into a few problems with the build, but nothing a little bit of superglue couldn’t fix. It may have fewer moving parts, but this definitely puts our old Visible V8 Engine kit to shame.

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