Sikorsky and Lockheed Martin’s determination to construct a hybrid tilt-wing expertise demonstrator is a major step ahead for eVTOL plane. We’re in a singular place to say this, as Dufour Aerospace has been designing, constructing, and testing tilt-wing plane for a few years.
We are going to current among the causes that we imagine Sikorsky has made the proper alternative in creating a tilt-wing, together with hover, transition, cruise effectivity, clean transition, robustness, scalability, and naturally security.
What’s a tilt-wing plane?
Not like tilt-rotor or tilt-propeller plane, a tilt-wing tilts the entire wing as an alternative of simply the propeller nacelles. Whereas this may increasingly appear a small element, it’s really a basic distinction.
Tilt-wing plane aren’t new – they had 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 methods weren’t but obtainable. Distinguished 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 mounted horizontal wing blocks the airflow. This lack of thrust known as “obtain”. The presence of the wing is an obstacle for the plane till it has accelerated past a essential velocity.
Tilt-wing plane, in distinction, hold the wing aligned with the propeller thrust. This minimizes obtain and drag, and the airflow energizes the wing, producing further carry as quickly because the plane begins to maneuver ahead.
This attribute is a major 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 advanced 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 offers carry always, the ability necessities for transition are dramatically decrease than with some other 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 potential in cruise. Effectivity comes with what known as a “clear” configuration – as little drag as potential. Some VTOL configurations, equivalent to lift-and-push, carry the burden of non-lifting elements (equivalent to propellers which might be solely used for hover) throughout cruise flight. These elements create drag, decreasing the general effectivity. Everybody who ever flew a propeller plane with velocity brakes is aware of the affect of drag. The lean-wing design may be very clear in cruise, so doesn’t undergo from this downside. So the tilt-wing plane is a fuel-efficient long-range cruiser, which can also be able to VTOL operations.
Mechanical simplicity and robustness
Hinges on VTOL plane are essential elements but additionally symbolize potential weak factors. They have to be sturdy and redundant. Dropping a hinge in flight and potential cascading failures are a threat that must be eradicated as a lot as potential.
Essential hinges are designed to be multi-loadpath and harm tolerant in order that there isn’t any single level of failure. It is 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 authorized a lot the identical approach as our wing tilt system.)
Constructing hinges on this rock-solid approach provides weight and inspection necessities, after all. So it is a bonus to have a single hinge, because the tilt-wing does, moderately 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 completely speaking about element certification. There’s little or no dialogue of what issues equally as a lot: the flight conduct and management margins of the plane.
Technical failure of a element isn’t the explanation for an accident. 80% of the accidents are brought on by human error – a pilot mistake. So it’s essential that pilots (and automatic flight management methods) 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 ingredient 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 power to regulate the wing to any given wind scenario permits for redundant management and clean transitions whereas retaining the cabin stage.
This isn’t simply principle: it has been confirmed and examined by a whole lot of take a look at and military pilots with the CL-84 and XC-142 plane, and by Dufour Aerospace in take a look at flights nearly each day.
Scalability
The air behaves in another way at totally different scales. What works for a multicopter drone, a “flying brick”, doesn’t work so properly 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 skill to cowl the most important vary of transitional plane at an inexpensive price.
Conclusion
At Dufour Aerospace, we’re properly conscious of some great benefits of the tilt-wing configuration, as we have now been constructing and flying tilt-wing plane for a few years, so we perceive the explanations behind Sikorsky’s determination.
They’ve additionally determined to pursue a hybrid energy method, moderately than utilizing solely batteries for power storage. Electrical propulsion has many benefits, together with noise discount and redundancy. Nonetheless, at this time’s battery expertise doesn’t come near the precise power obtainable in gas. The hybrid energy configuration will enable Sikorsky to convey collectively the very best of each of those applied sciences, and obtain for much longer vary missions, and larger operational versatility, simply as we do at Dufour Aerospace.
From our staff at Dufour Aerospace to yours, congratulations, Sikorsky!
