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Apart from using fairings, what ways are there, or have been studied, but not necessarily implemented in reducing drag and noise produced by the landing gear, mainly for commercial aircraft with retractable landing gear, but would also like to know about smaller aircraft, perhaps with non-retractable landing gear.

Is there a study or a design that has been done on landing gear to reduce drag and/or noise produced by the landing gear?

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    $\begingroup$ You should choose between drag and aerodynamic noise, and the aircraft type you are interresting in. Moreover, you should show your current state of research (e.g. do you see the dr 400 landing gear?). $\endgroup$ – Manu H Mar 27 '18 at 18:56
  • $\begingroup$ @ManuH The main aim of the research is to reduce noise, but it seems that there would be the benefit of drag reduction to follow. As mentioned the aircraft type is a commercial airliner, specifically the A350-900. See my comment to the answer below for information on the current state of research. $\endgroup$ – S. Salhab Mar 29 '18 at 2:14
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The biggest noise reduction is achieved by closing most of the landing gear doors again after extension is complete.

Of the factors that influence drag and noise, one is the distance between wheel and fuselage. The picture below is taken from S. Hoerner's book "Fluid Dynamic Drag", chapter XIII.5 of which deals with the drag of landing gears.

Wheel drag in the nose of a fuselage

Another influence is the shape of the landing gear strut. Since most airliner landing gear legs are oleo struts, they are round for practical reasons. Fairing them would already help, as can be seen from the lower line in the plot above. Another improvement can be achieved by covering the wheel hubs. However, the reduction of the drag and noise caused by extended, retractable landing gears has been studied but few of the results have yet found their way into actual aircraft. According to this DLR report, a fully faired A320 landing gear would reduce noise by 10 dB while partially fairing the most noisy parts of an A340 landing gear would reduce noise by 5 dB. The picture below is taken from this report.

Partially faired A340 landing gear

For fixed landing gears, I recommend NACA Technical Report 485 which contains results of full-scale tests on several gears. NACA Technical Report 518 contains results for partially retractable gears.

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  • $\begingroup$ That is exactly what I have been looking into. I am actually trying to retrofit a strut fairing to the main landing gear of the A350-900. The main aim is to reduce noise, but it seems obvious that there would also be the benefit of drag reduction. With that being said, I am currently looking into and trying to figure out the constraints there are to work with, and what exactly is the area or space available to be used to retrofit said fairing. It would have to not restrict any of the mechanisms and take advantage of any space available. $\endgroup$ – S. Salhab Mar 29 '18 at 1:55
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I don't know that non-retractable landing gear make any noise. If they do, it's certainly not audible above the engine.

To reduce drag, fairings are the only method I know of. I am currently replaceing my old beat up 1973 vintage ABS plastic fairings with newer more aerodynamically shaped fairings to reduce drag. All 3 wheels, main gear legs, and also around the nose scissor jack. And going to a more aerodynamically shaped tail cone. All should contribute to a speed increase, and will look sharper after being painted. You can see them here: http://www.aircraftspeedmods.ca/products.htm

If you look at the Red Bull racing airplanes, you can see similarly shaped fairings, and what looks to be much smaller wheels as well (single seat planes vs a 4 seater). Take a look AT Extra 300S airplanes, I think that is what they are using now.

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  • $\begingroup$ Aeroengineer Roy Sobchuk did tests with tufts of string to determine where air was most turbulent to help come up with the shapes used on my model of airplane. $\endgroup$ – CrossRoads Mar 27 '18 at 17:03
  • $\begingroup$ Looks like Red Bull Air Race pilots fly several types of planes <airrace.redbull.com/en_US/article/planes> $\endgroup$ – CrossRoads Mar 27 '18 at 17:10
  • $\begingroup$ Of course they make noise. This adds up, and especially with engine idling during approach the landing gear generates a considerable part of the overall noise of airplanes. $\endgroup$ – Peter Kämpf Mar 27 '18 at 19:15
  • $\begingroup$ What kind of plane are you referring to? In my fixed gear single airplane, they aren't making much noise. $\endgroup$ – CrossRoads Mar 27 '18 at 22:09
  • $\begingroup$ @PeterKämpf All sources of aircraft noise, and the latest technology in reducing aircraft noise are summed up in this DLR presentation. $\endgroup$ – S. Salhab Mar 29 '18 at 2:29

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