Unfortunately, the progress of our part 23 certification effort has slowed down while we reach out for additional financial assistance. Our application and submission for both the turbine 650T and the 5 place model 500 remains in good standing with the Alaskan ACO and a considerable amount of drawings and engineering has been completed to move the project forward. Because of the continued interest that has been expressed about our original 5 place model we are incorporating a scaled down version of Sherpa’s big turbine wing that will replace the original 5 place wing and will continue drawings and engineering efforts with this new wing. We are pushing hard to complete the process within 30 months depending on the finances. As most of our support groups know, Byron and I are now in our 27th year in an effort to develop of these great aircraft.
The old song, “You can’t have one without the other”, pretty much sums up the recent development in the design requirements for the latest 8 place 650T turbine slated for delivery to Alaska. As crazy as it may seem, we made some aerodynamic design change improvements to the wing and flap system to improve the speed range of the aircraft that turned out far more effective than we hoped for. After completing an upgrade to the design of the trailing edge of the wing and flaps and the nesting position of the flaps our slow speed performance dropped from the mid-40s to the low 30s and our cruise speed increased by 10 to 15 MPH. As a result of this unexpected major impact on the airspeeds it became difficult to reach the low speeds that allow the desired three point stall landing. One would normally think that with an aircraft, the slower the better. In this case however, we were able to fly so slow that the tail surfaces weren’t getting enough air flow to remain effective and the 840HP 331-5 engine that normally powers aircraft that land at much higher speeds produces so much thrust at the standard idle cut off setting we couldn’t slow the airplane down under 50 MPH. When we used full flaps at 40 degrees to slow the airplane down we made matters worse by creating so much disturbed air that we blank out the tail.
One of the first issues we are dealing with is to adjust the normal propeller blade angle from 4 degrees to 1.5 or 2 degrees as was necessary on Sherpa’s first turbine prototype. This change should reduce the thrust so that the airplane can slow down. In addition, a relocation and complete redesign of the old style Super Cub flat horizontal stabilizer and elevator is being modified to include a flying tail that was originally considered for the original 650T prototype. It is likely that the flaps setting will also be restricted to 30 degrees or less as was the done in the original flying prototype.
The company understands the challenge of producing an aircraft that pushes the limits in so many areas:
- The Sherpa wing is very efficient and produces gigantic lift that maintains directional control at very slow speeds
- The massive flaps can produce extreme drag and lift for the slow speed operation
- The combination of Honeywell’s 840 HP 331-5 low 1591 RPM power plant and Hartzell’s powerful 116inch long 3 blade propeller produces unbelievable static thrust
Put that all together with a Sherpa’s tough undercarriage and structural design with great pilot visibility and you end up with the best of all worlds.
That’s our Sherpa!
FAA Staff Members join forces with Sherpa Company personnel for an official type certificate board meeting at Sherpa headquarters in Scappoose. The group, shown by one of the companies latest turbine aircraft, takes the opportunity to make a first hand inspection of the aircraft as it nears final completion for delivery to Anchorage, Alaska.
Pictured above is the signing acceptance of Sherpa’s official certification plan. Pictures (l-r) Glen Gordon; President Sherpa Aircraft, Della Swartz; Program Manager FAA Anchorage and August Asay; Office Manager FAA Anchorage
Sherpa is upgrading the K-500 which was originally produced as Sherpa’s first flying prototype. Innovation in the new five passenger aircraft will be the removal track mounted seat feature and the employment of the same wing designed for the big 8-place turbine. Gross weight will be increased to 5000lbs. Certification of the new K-500 will run parallel with the certification process of the 8-place turbine which is now underway.
Certainly no lack of power shown here with Sherpa’s first pull test measuring 2675 pounds of static thrust with the powerful combination of Honeywell’s 331-5 turbine engine and the 116 inch 3 blade Hartzell propeller.
It came as no surprise that hundreds of excited 2010 show attendants swarmed Sherpa’s display throughout the entire show. Viewers were continually amazed with the off airport performance capabilities for such a big aircraft that can cruise more that 200 mph and still land under 40 mph.
Interests varied as viewers considered the many tasks the new turbine Sherpa was capable of performing. Of particular notice was the amount of interest expressed from the different law enforcement groups, missionary organizations, life flight emergency services and mining operators.
Representatives from New Zealand, Australia, Brazil, Argentina, Switzerland, Germany, Russia and more expressed amazement that such an aircraft exists.<