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Looking at the Snecma C-450 Coléoptère, I was wondering about the (4?) fins towards its tail:

World ugliest plane

Source: Wikipedia

Were they able to pivot to help the pilot control the aircraft? If not, what else was enabling control to the pilot ?

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    $\begingroup$ That is one scary looking aircraft, it just screams unstable. $\endgroup$
    – GdD
    Aug 8 '17 at 7:39
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    $\begingroup$ @GdD It was put down after it tried to kill its test pilot. $\endgroup$
    – Antzi
    Aug 8 '17 at 7:51
  • $\begingroup$ @GdD For some reason, I imagine it rolling off the side of the not-perfectly-level runway and toppling when two castors dig into the grass. $\endgroup$ Aug 8 '17 at 12:58
  • $\begingroup$ The fact that someone actually flew in that thing is amazing. $\endgroup$
    – coteyr
    Aug 8 '17 at 14:30
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    $\begingroup$ @mins The technology demonstrator used before the Coléoptère was just that. A Big reactor with a seat on top: en.wikipedia.org/wiki/SNECMA_Atar_Volant $\endgroup$
    – Antzi
    Aug 9 '17 at 1:29
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Great find, a vehicle with so many new design features in a time before Computed Fluid Dynamics, and hard to test in a wind tunnel where the device could only be mounted in a fixed position.

From this source:

Takeoff, hover, and landing were controlled by deflecting vanes in the engine exhaust: in horizontal flight by four fins mounted just above the castoring landing gear, and in the transition to vertical flight by two retractable canards in the nose.

This source states that the four delta surfaces were movable and were to be used to control horizontal flight. They were puny though, and mounted quite close to the aircraft roll axis. One of the problems encountered during test flight was a slow uncontrolled roll.

For the control of the aircraft in fast flight, there were four cast solid control surfaces allowing in-depth aerodynamic control (horizontal control surfaces) or in rolling and direction (vertical control surfaces). For the phases of vertical takeoff and landing, control was ensured by deviation of the jet (pitching and lace) and of compressed air coming from the compressor (rolling).

The same source has a frontal view of the craft:

enter image description here

So yes the four delta surfaces were able to pivot but were obviously inadequate for providing any control at low speeds. Thrust vectoring was required for slow flight.

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    $\begingroup$ The front view is truly a great help, thanks ! $\endgroup$
    – Antzi
    Aug 8 '17 at 6:48

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