47
$\begingroup$

This photo of the XB-70 Valkyrie's main gear shows a small wheel between the two main wheels:

XB-70 MLG
Courtsey of AirPigz.com

This smaller wheel doesn't touch the ground, though I can see where it might as the side walls of the main tires compress under landing weight.

The AirPigz site promised an explanation, but none has been forthcoming (in the 4+ years since that was posted), and I couldn't find any information on it on Wikipedia, either. Does anyone have any information (real or speculative) on what it's for?

$\endgroup$
  • 3
    $\begingroup$ Ha! I spotted that on the video that was posted the other day, but was too lazy to ask. Thanks! $\endgroup$ – Jörg W Mittag Apr 26 '16 at 0:58
69
$\begingroup$

It is a sensing wheel that is part of the antiskid braking system. It contains an electronic sensor to measure the true groundspeed of the airplane. See NASA Technical Note D-4836, Landing Loads and Accelerations of the XB-70-1 Airplane (1968), bottom of page 3 of the document (page 5 on the PDF):

enter image description here

$\endgroup$
  • 3
    $\begingroup$ Wow! A quick and authoritative answer! Did you know this or is your Google-fu that good? $\endgroup$ – FreeMan Apr 25 '16 at 16:54
  • 10
    $\begingroup$ Call it a lucky Google. $\endgroup$ – Fred Larson Apr 25 '16 at 16:56
  • 2
    $\begingroup$ Nice "lucky Google", then Fred! I'm sure I could have done the same, but it's good to have information gathered here on what's quickly become my favorite web-site. Thanks for the image embed, @mikeSowsun $\endgroup$ – FreeMan Apr 25 '16 at 17:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.