Sikorsky and Lockheed Martin’s resolution to construct a hybrid tilt-wing expertise demonstrator is a big step ahead for eVTOL plane. We’re in a novel place to say this, as Dufour Aerospace has been designing, constructing, and testing tilt-wing plane for a few years.
We’ll current a few of the causes that we consider Sikorsky has made the correct selection in creating a tilt-wing, together with hover, transition, cruise effectivity, easy transition, robustness, scalability, and naturally security.
What’s a tilt-wing plane?
In contrast to tilt-rotor or tilt-propeller plane, a tilt-wing tilts the entire wing as an alternative of simply the propeller nacelles. Whereas this will likely appear a small element, it’s really a elementary distinction.
Tilt-wing plane are usually not new – they have been designed, constructed, and intensively flown within the 60s and 70s of the final century, at a time when distributed propulsion and superior digital management techniques weren’t but obtainable. Outstanding representatives of this primary tilt-wing wave are the American XC-142 and the Canadian CL-84 plane.
Hover and transition effectivity
Tilt-rotor and tilt-propeller plane lose a few of their thrust throughout vertical take-off and touchdown as a result of the fastened horizontal wing blocks the airflow. This lack of thrust is named “obtain”. The presence of the wing is an obstacle for the plane till it has accelerated past a vital velocity.
Tilt-wing plane, in distinction, maintain the wing aligned with the propeller thrust. This minimizes obtain and drag, and the airflow energizes the wing, producing further elevate as quickly because the plane begins to maneuver ahead.
This attribute is a big benefit for the general energy necessities and configuration of the plane.
Clean transition with massive security margins
Transitioning from hover to ahead flight and vice versa in lots of VTOL configurations is aerodynamically complicated and energy-intensive. The lean-wing design simplifies this transition. By rotating the entire wing ahead, the tilt-wing seamlessly converts from a vertical to a horizontal configuration, with out drastic adjustments in airflow. There is no such thing as a handover between a hover propulsion system and a cruise propulsion system as is the case with lift-and-push configurations. This interprets to smoother, seamless transitions.
Because the wing supplies elevate always, the ability necessities for transition are dramatically decrease than with another convertible idea, leading to excessive effectivity. There are additionally massive energy margins remaining for management and a large hall within the flight envelope, which interprets on to massive security margins always.
Cruise effectivity
As an eVTOL plane flies 90% of the time in cruise configuration, it’s important that the plane is as environment friendly as attainable in cruise. Effectivity comes with what is named a “clear” configuration – as little drag as attainable. Some VTOL configurations, equivalent to lift-and-push, carry the burden of non-lifting parts (equivalent to propellers which might be solely used for hover) throughout cruise flight. These parts create drag, lowering the general effectivity. Everybody who ever flew a propeller plane with velocity brakes is aware of the influence of drag. The lean-wing design could be very clear in cruise, so doesn’t endure from this disadvantage. So the tilt-wing plane is a fuel-efficient long-range cruiser, which can be able to VTOL operations.
Mechanical simplicity and robustness
Hinges on VTOL plane are vital parts but additionally symbolize potential weak factors. They should be strong and redundant. Shedding a hinge in flight and potential cascading failures are a threat that must be eradicated as a lot as attainable.
Crucial hinges are designed to be multi-loadpath and harm tolerant in order that there is no such thing as a single level of failure. This can be a well-known design precept in aviation, and is used for instance on the horizontal stabilizer trim mechanisms of all industrial airliners. (These trim mechanisms are designed and licensed a lot the identical method as our wing tilt system.)
Constructing hinges on this rock-solid method provides weight and inspection necessities, after all. So it is a bonus to have a single hinge, because the tilt-wing does, reasonably than a number of hinges as in a tilt-propeller design.
Dealing with qualities
When speaking about security, most representatives of the eVTOL scene are nearly solely speaking about element certification. There’s little or no dialogue of what issues equally as a lot: the flight habits and management margins of the plane.
Technical failure of a element isn’t the explanation for an accident. 80% of the accidents are attributable to human error – a pilot mistake. So it’s vital that pilots (and automatic flight management techniques) have sufficient management margin to react if one thing unexpected occurs.
A direct studying of Dufour Aerospace’s CEO, Thomas Pfammatter, with over 30 years of expertise in helicopter operations, is that having massive management authority margins is a key component for security.
That’s the place tilt-wing plane excel. The propellers and absolutely energized wing with aerodynamic management surfaces present highly effective and direct management authority in all three axes. Moreover, the flexibility to regulate the wing to any given wind scenario permits for redundant management and easy transitions whereas holding the cabin stage.
This isn’t simply concept: it has been confirmed and examined by lots of of check and armed forces pilots with the CL-84 and XC-142 plane, and by Dufour Aerospace in check flights nearly daily.
Scalability
The air behaves in another way at completely different scales. What works for a multicopter drone, a “flying brick”, doesn’t work so nicely for bigger plane. Whereas multicopters, lift-and-push, and tilt-propeller plane wrestle to scale up, tilt-wing plane can comfortably be a lot bigger. This has been confirmed by the XC-142 at over 20 tons, and is as a result of effectivity of the blown wing.
That makes the tilt-wing idea distinctive in its capacity to cowl the largest vary of transitional plane at an affordable price.
Conclusion
At Dufour Aerospace, we’re nicely conscious of some great benefits of the tilt-wing configuration, as we’ve been constructing and flying tilt-wing plane for a few years, so we perceive the explanations behind Sikorsky’s resolution.
They’ve additionally determined to pursue a hybrid energy strategy, reasonably than utilizing solely batteries for power storage. Electrical propulsion has many benefits, together with noise discount and redundancy. Nevertheless, at present’s battery expertise doesn’t come near the particular power obtainable in gas. The hybrid energy configuration will permit Sikorsky to convey collectively the perfect of each of those applied sciences, and obtain for much longer vary missions, and higher operational versatility, simply as we do at Dufour Aerospace.
From our staff at Dufour Aerospace to yours, congratulations, Sikorsky!