Spirit Wing Aviation to seek Single Pilot certification for SpiritJET™
Spirit Wing Aviation is seeking certification for single pilot operation of its SpiritJET™
modification to the 25 series of Learjets. Because of the substantial configuration changes made to install the new Williams FJ44-2C engines and the aerodynamic changes made to the aircraft, the control forces have been dramatically reduced which should allow for approval of the modified aircraft for single pilot operation.
This is a real breakthrough for a light jet with the capabilities of this aircraft. The original Learjet is equipped with pylon-mounted General Electric CJ610 turbojet engines. The canted angle of the original engine mount induces some nose-down pitching moment on the aircraft. To overcome this nose-down force, the tail must exert a counteracting aerodynamic tail-down force. These counteracting trust and aerodynamic forces consequentially increase wing load in flight, effectively increasing the amount of weight being carried by the wing. This additional load on the wing make it necessary for the original aircraft to fly with a higher drag-inducing angle of attack to generate required lift during all phases of flight. The original CJ610 aft-canted pylon and narrow air path between the engines and the fuselage cause airflow accelerations in the pylon area that also adds drag as the plane moves through the air.
When Spirit Wing Aviation engineered the new engine installation, great care was taken to overcome the incremental drag forces associated with the original installation of the GE engine. The SpiritJET™ Williams engine line of trust is now aligned with the aerodynamics of the aircraft which has optimized use of engine trust and has decreased drag. Additionally, the new engines are mounted 16 inches aft of the original CJ610 engine position and 4 inches further away from the fuselage. As a result, the SpiritJET™ Williams engine pylon area airflow speed has been significantly reduced and now matches aircraft speed. These performance enhancements have yielded much lower aerodynamic loads on the aircraft during all phases of flight and facilitate a maximum cruise speed of over 480 knots on the SpiritJET™ while utilizing lower-thrust engines and far less fuel.
An additional benefit which had not been fully appreciated until recently was the resulting reduction in control forces required to fly the aircraft. This was not realized until instrumented flight testing began. Spirit Wing engineers discovered that the control forces have been reduced dramatically and the handling qualities of the modified aircraft have been vastly improved. The SpiritJET™ has a far more effective wing working for it, making for a very mild-mannered aircraft. Company tests indicate that all control force limitations for single pilot certification can be accomplished with room to spare.
We currently have every reason to believe that single pilot certification is within reach and have officially integrated this operational feature in our certification plan. Based on current data, this proposal will very likely produce the first FAA Part 25 aircraft to achieve single pilot certification. Many other SpiritJET™ firsts will make operation as a single pilot easier for the aircraft, including a fully-automatic triple-redundant pressurization system which will operate even if the system is not turned on, as well as full-time engine and full-time wing anti-ice systems. This will be in addition to the safety of a Part 25 certified aircraft, certified to amendment 108, which is the same standard under which the new Boeing 787 will be introduced into service.
All systems, including electrical, hydraulic, pneumatic, de-icing, and environmental will be certified to current regulations, and the existing airframe is still the toughest in the business. The powerful new engines from Williams make the SpiritJET™ the most cost-effective high-speed aircraft in its class. The airframe has no life limits as was built with the same demanding criteria as a Boeing or an Airbus.
Spirit Wing Aviation looks forward to completing certification of the SpiritJET™ during 2008, and plans to announce during the summer of 2008 one or more relationships with modification shops with which customers may contract for the SpiritJET™ modification.
For more information, please contact Blaine McColgin, Director of Operations at Spirit Wing Aviation in Guthrie, Oklahoma, at phone (405) 260-0555, or fax (405) 282-8245.