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Can anyone explain what is the teardrop-shaped item behind the cockpit?

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1 Answer 1


It is the RDF antenna 'bullet' (or teardrop, actually) fairing. This image shows the (loop) antenna itself.

RDF antenna

Source: mission4today.com

Initailly, RDF antennas were circular loops mounted above or below the fuselage.


"Earhart-electra 10" by Originally uploaded by w:User:Logawi - Transferred from en.wikipedia, description page is/was here.. Licensed under Public Domain via Commons.

Later loop antenna designs were enclosed in an aerodynamic, teardrop-shaped fairing.

B 17 loop antenna

Source: airpages.ru

  • 2
    $\begingroup$ The change, IIRC, is that the RDFs evolved into ADFs, which rotated to find the relative angle from the nose at which the beacon signal was strongest, allowing the pilot to get a fix from the beacon without having to change course or manually manipulate the antenna. The motorized rotating antenna, however, was much less aerodynamic and prone to damage at high airspeed, so it needed a housing to contain it. $\endgroup$
    – KeithS
    Oct 21, 2015 at 19:54

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