Matthew Piers Watt Boulton is known as the inventor whose 1868 British patent No. 392 nullified any claim of the Wright brothers that they discovered the ailerons (see FIG. 5-7). It seems now that another invention in the same patent (see FIG. 1) shows an engine similar to one that uses the Coanda effect (see the picture: "Diagram of a generic engine that harnesses the Coandă Effect to generate lift (or forward motion if tilted 90° on its side)" for comparison).

The question is: Did Boulton have really in mind the Coanda effect when he proposed the engine in FIG. 1?

This is the explanation Boulton gave to FIG. 1:

"A body is provided having the form of a solid of revolution tapered at the stern and prow on front. An annular jet of aeriform fluid is caused to issue at its fore part in front of its convexity so as to mix with air and create a mixed stream which flows or sweeps over the convex surface, finally quitting it backwards. In this case the action of the jet causes reduction of pressure on the front and thus produces propulsive effect."

"Figure 1 is a longitudinal section of a body or vessel constructed according to my Invention, propelled by an annular jet issuing at its front. a is the body or vessel containing fluid under pressure and shaped so as to offer little resistance to longitudinal movement in the direction of the arrow e; b is a tapering front or prow connected to a by thin ribs; and c is a cavity so formed with an opening round its periphery that an annular jet of fluid can issue by it perpendicularly to the longitudinal axis of a or nearly so. When the jet so issues it tends to reduce pressure on all sides. By virtue of this reduction of pressure the air (or other medium in which the body is placed) in front being free to move flows backwards towards the jet and mingles with it, while the body a being also free to move, moves forwards in the direction of the arrow e. The jet instead of issuing from c perpendicularly to the longitudinal axis of a may be made to issue at any desired angle by suitably forming the passage round the periphery of c."

enter image description here FIG. 1 shows an engine that seems to use the Coanda effect and FIG. 5-7 a wing with ailerons (driven by a pendulum but the patent specifies they can also be controlled by hand). The entire patent of Boulton can be consulted HERE

A diagram of a generic engine that harnesses the Coandă Effect to generate lift (or forward motion if tilted 90° on its side

A diagram of a generic engine that harnesses the Coandă Effect to generate lift (or forward motion if tilted 90° on its side).

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    $\begingroup$ I'm voting to close this question as off-topic because it's about history - "what did this individual know," rather than about Aviation as defined in the Help Center. $\endgroup$
    – Ralph J
    Commented Dec 27, 2019 at 14:59
  • $\begingroup$ Regarding the Coanda effect, I do not know if Boulton referred to this phenomenon or had in mind just the law of Bernoulli and possible other things. Regarding the ailerons, it is clear from his patent (see the explanations from here: en.wikipedia.org/wiki/Aileron) that he proposed ailerons and nothing else for controlling the longitudinal stability of what he called "aerial vessels". He even talked about controlling the flying machine in the vertical and horizontal planes by other means. He was fully aware of three-axes control. $\endgroup$
    – Simplex11
    Commented Dec 27, 2019 at 16:25
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    $\begingroup$ I voted to leave this open...I would be interested in hearing the answer. Also, why would there be an aviation-history tag if history questions were off topic? $\endgroup$ Commented Dec 27, 2019 at 18:32
  • $\begingroup$ Also, @simplex can you provide evidence that the wright brother claimed to have invented the aileron? I was unable to find any evidence of this. The wright flyer, the first "airplane" did not have ailerons but instead used wing warping for roll control. Otherwise, please reword your post. $\endgroup$ Commented Dec 27, 2019 at 22:03
  • $\begingroup$ @bclarkreston The Wright brothers claimed they had invented not only the wing twisting method for stabilizing a plane in roll but the ailerons in general. See the paragraph titled "Patents and lawsuits" of this page en.wikipedia.org/wiki/Aileron. $\endgroup$
    – Simplex11
    Commented Dec 27, 2019 at 23:44

1 Answer 1


The accompanying text clearly describes an application of the Bernoulli effect. However the resultant backwards airflow shown in the drawing is given no explanation, other than that implied by the fact that the device is drawn forwards. So there is no evidence of the Coanda effect, in which the airstream clings to the device skin, being understood. Would it have worked? Probably, but it would have been pretty inefficient.


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