How tiny vanes glued to the C-17 fuselage are saving millions in fuel costs

[onetrack]

An interesting little story here, showing how even small tweaks to proven designs can add up to improvements in airflow and substantial reductions in fuel costs, over time.

 

It'd be good to find out what level of money and effort they spent on designing and testing of the vanes, just to see what went into them in total, but I guess the effort and money was repaid within a relatively short time frame, with overall fuel savings.

 

Tiny vanes glued to planes promise big savings for US Air Force

NEWATLAS.COM

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A surprisingly simple tweak is making a venerable military transport aircraft more efficient. Literally gluing a few microvanes to the rear fuselage of a C-17 Globemaster III cargo plane can result in fuel...

 

[facthunter]

The President is extremely VAIN. I hope it makes HIM GO faster.   That will save a lot of money.  Nev

[IBob]

Them's pretty big vanes at 4" x 16". Be interesting to see the detail of how they reduce drag, which the article says is the result of the upswept loading door/s shape.

[facthunter]

The rear doors probably make a lift force in a downwards direction which you'd be better off without. It's shaped that way to enable the lift off Pitch angle without the tail contacting the runway  Nev

[IBob]

I guess, the way they are angled, the vanes will act to lift the tail. Though why that should induce less drag than lifting it with elevator trim, I don't know.
Another possibility is that the modified airflow serves to reduce the 'downwards lift' of that rear section. Perhaps they disrupt the laminar flow, so causing that downward lift (or part of it) to stall?

[facthunter]

Reduce the existing deficit of pressure in the area. Another way of looking at it..  Nev

[IBob]

They've been working on this for 9 years. The fact that they can 'only' get a 1% reduction in drag seems to indicate that the thing was pretty well optimised to start with?

[facthunter]

Not really. They might just accept it as inevitable to have other advantages, Like driving up the ramp  to load and being able to slide stuff off it in flight. Nev

[Red]

They look to be a boundary layer control device, possibly energising an area of flow stagnation

[johnm]

parasites ................................... parasitic drag ?

[facthunter]

Drag not associated with lift production is termed Parasitic. Nev