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Old 22nd Jul 2018, 14:46
  #35 (permalink)  
Bagheera S
 
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Pre spinning wheels is regularly suggested but has never been taken up to any significant degree ( I never knew about the Cutlass NLG.... many thanks for the info). The aircraft landing systems industry wide standards committee, the SAE A5 has seen pre spinning suggested so many times they’ve produced a standard response which from memory is AS5400;- This is factually based, professionally referenced and details the rationale for not doing it. In summary, most of the tyre wear comes from braking + turning at MTOW, a spin up motor torque/power requirements are surprisingly high (it includes a few sums), cups/vanes will never match the landing speed/take way too long and if such a system really was used to lower touch down loads, what does the pilot do on the day the system doesn’t work ....or it jams ?

From memory there’s a reference to a trial conducted by RAE on Tornado where a chap wrote to his MP demanding that this obvious cost saving be investigated. The MP asked questions to the Defence Ministry so the RAE were duly tasked to give it a go. Hence they modified a couple of tyres with rubber cups to provide an urge to spin up. When the trials aircraft took off the pilot braked the wheels to a stop in flight, released the brakes and watched to his horror one wheel spin up in the correct direction and the other spin up in the wrong direction! He made several attempts to see if he could get both spinning in the same direction but failed, so did a very slow descent rate landing with an initial skip to get all the wheels spinning correctly. Upon investigation it was discovered a local turbulent airflow between the fuselage and wheel would cause at least one to spin in the wrong direction. Unsurprisingly the idea was quickly abandoned..........the devils always in the detail.

Wheel pre-spinning is the most patented inventions related to aircraft landing systems over the last 40+years with literally hundreds of fillings, but still we see no practical applications....that alone really tells you all you need to know.
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