Hybrid VTOL developer Horizon Aircraft has completed the first transition flight with its large-scale prototype, the first such evolution for an in-wing fan-configured aircraft. Videos of the first flight are available (click HERE).
Observation of the flight sequences shows a number of points which Rotor Hub International raised with Horizon CEO Brandon Robinson:
RHI: Observation of the tell-tales revealed a good deal of turbulent flow during the transition. Was this induced by the fan inflow, angle of attack or a combination of both?
BR: “We set our transition velocity just a bit too low. The aircraft was so controllable and responsive, building up to the fully closed position, that these minor disturbances, mostly caused by the longitudinal panels, didn’t really worry us.”
RHI: Also noticeable was that the canard moved to the closed position before the main wing. We wondered what the reason might be for that?
BR: “Prior to this flight, we investigated numerous sequencing options. We were able to experiment because the aircraft is very stable in this phase, so we were comfortable doing additional research. Since it didn’t matter from a stability perspective, closing the canards first just makes the aircraft more slippery and gives us more thrust. In the transition back to the hover, the main wings configure first, again because of the stability, it didn’t matter much what the sequence was, so we went for the option that would create the most drag to aid deceleration.”
RHI: It’s noticeable on the main wing/wing to hover transition, the centre panels move slightly before the inner and outer sections. Is there a reason for this?
BR: “Both centre sections are currently positioned slightly forward. Speaking frankly, this was not intentional, but it didn’t make any difference. Obviously, on the full-scale aircraft, the position will be closely monitored, but at this scale, the transition was so robust that it didn’t need to be fixed.”
RHI: There seemed to be a good deal of wing flex centred on the wing root rather than along the span. Was there a thinking that drove this, for example, a need to keep the lift fans in a constant plane?
BR: “This is something we’ve had in consideration for years. On the 50% scale aircraft, we wanted to evaluate control problems like low-frequency wing vibration and challenge ourselves with the e-motor fan in wing tuning. We also wanted to make it tough since we knew we’d be punishing it with hard landings, so having the wings flex enabled us to lower fuselage weight. Believe it or not, we put ~3.8Gs on those wings and they were fine, albeit they deflected a lot!”
Horizon now plans to continue flight testing with the 50% scale aircraft, moving on to the construction and testing of its full-scale prototype.
Image: Horizon Aircraft
