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Note: This is a sub-section of Boulton Paul Aircraft.
The Boulton Paul P.120 was a British research aircraft produced to investigate delta-wing aerodynamics in the early 1950s. It was very similar to the tailless Boulton Paul P.111 apart from having a horizontal tailplane.
The P.120 followed the earlier Boulton Paul P.111 delta-wing experimental aircraft. It was produced for the Air Ministry to specification E.27/49 and differed from the P.111 in having a swept fin and rudder with horizontal tail surfaces high on the fin to improve longitudinal and directional stability. It had essentially the same wing as the P.111 in the latter's greatest span configuration, an unclipped delta; the wing tips of the P.120 were not removable or replaceable, but they could be rotated differentially or together for lateral or longitudinal trim. Just inboard of these tips the P.120 gained a pair of wingfences. The fuselages of the two aircraft were also identical, except towards the rear.
Although plans were made to convert the earlier P.111 to the P.120 configuration, a decision was made to suspend further development, making the P.120 the last Boulton Paul design to fly.