[Avionics Magazine 10-27-2016] A patent awarded to Boeing on Tuesday, Oct. 25, 2016, from the U.S. Patent and Trademark Office (USPTO) could signal the Original Equipment Manufacturer's (OEM) desire to build a Vertical Takeoff and Landing (VTOL) commercial passenger aircraft. Boeing originally filed the patent in June 2014, and described it as being developed specifically as a "response to the problems and needs associated with conventional tilt-rotor, vertical-lift aircraft that have not yet been fully solved by currently available aircraft."
Within the patent, Boeing describes the aircraft as being capable of transporting up to 100 passengers in a regional commercial airframe configuration. The basic configuration is described as featuring two fixed wings with two engines on each wing and tilt-rotors that can be used in vertical or horizontal orientations. The tilt rotors would be used for vertical take off and landings, and then converted to a horizontal orientation to enable the aircraft to be flown like a normal commercial passenger aircraft.
VTOL aircraft can be configured as fixed wing or rotary wing structurally. Currently the U.S. military's VTOL lineup includes the Bell Boeing V-22 Osprey, the AV-8B Harrier II and the short takeoff/vertical landing (STOVL) variant of the F-35 Lightning II, the F-35B STOVL. The V-22 can carry up to 24 troops, but the patent filed by Boeing includes what the company sees as shortcomings presented by problems associated with the designs of tilt rotor vertical lift aircraft that are currently available, mostly for military operators. One such shortcoming described is the high wing configuration featured on currently available VTOL aircraft.
"One such shortcoming includes increased weight and complexity associated with structural reinforcements in the fuselage under the wings that are required to prevent the high wings from crushing the fuselage during a crash. Additionally, due to the placement of high wings on the aircraft, maintaining and fueling the aircraft may be difficult, as well as removing and servicing engines on such aircraft," Boeing states in the patent.
Another shortcoming of the high wing configuration of traditional VTOL aircraft is the difficulty of servicing, taxiing, loading and unloading such an aircraft in a commercial passenger transportation setting, such as an airport.
Boeing also describes two engine configuration of traditional VTOL aircraft as not being sufficient for a commercial passenger carrying airframe. Specifically, the company notes that the power generated by two engines combined can power the tilt rotor assemblies sufficiently, but if an engine were to become inoperable during a flight, that would not be sufficient which is why two engines on each wing are featured in the drawings proposed for the aircraft described in the patent.
"The aircraft additionally includes a power transmission system that is configured to transmit power generated by each of the engines to both of the two tilt-rotor assemblies. According to certain implementations of the aircraft, each of the two tilt-rotor assemblies is coupled to a tip of the respective one of the two fixed wings. The two tilt-rotor assemblies can each rotate a rotor between a vertical orientation and a horizontal orientation. The aircraft can be a commercial passenger aircraft," the patent states.
While the design is an exciting concept, there is the possibility that it may never actually get produced.
“To protect our intellectual property, we file a number of patents every year that we may or may not pursue,” Doug Adler, a spokesperson for Boeing Commercial Airplanes said in an emailed statement.