Both Pilots Able To Bail Out Safely

The Aircraft Factory, the South African company which is developing the Sling LSA, says that at midday on Saturday, February 13th, ZU-TAF, the aircraft in which the company owners, Mike Blyth and James Pitman, circumnavigated the globe during 2009, went down in the ocean while conducting spin testing just off the South African Kwa-Zulu Natal coast. While the staff and owners of The Airplane Factory are devastated to have lost their production prototype aircraft, they believe that comprehensive spin testing of aircraft is an important aspect of an aircraft development program, notwithstanding that it is inherently risky.  

ZU-TAF File Photo

ZU-TAF was The Airplane Factory's second prototype aircraft and has precisely the same aerodynamic characteristics as the production aircraft which the company sells. The only structural differences between ZU-TAF and the production Sling were the sealing off of certain sections of the wing to increase the number of fuel tanks, the marginal beefing up of the composite main gear, making the joysticks removable in flight, and the removal of a cross brace behind the seats to allow the pilots to lie flat on long flights. In all other respects the round the world aircraft was the same as the production LSA Sling.

During July 2009 ZU-TAF was flown 9,000 nm from Johannesburg, South Africa, to Oshkosh, Wisconsin, westwards over a 10 day period. The longest leg included a 2,200 nm leg over the Atlantic Ocean. During August the aircraft was flown 15,100 nm back to Johannesburg, also westwards, over 23 days. The route included Los Angeles, Hawaii, the Marshall Islands, Micronesia, Indonesia, Malaysia, Sri Lanka and the Seychelles. The aircraft performed flawlessly during the entire circumnavigation. In fact the only maintenance related issues encountered were a faulty fuel tank drain valve and a crack in one of the supports for the electric propeller pitch motor.

ZU-TAF File Photo

In view of the aircraft's excellent performance well beyond 1,320 lbs a decision was also taken to certify the Sling not only in accordance with the ASTM LSA standard, but also to 1,543 lbs. This required further flight testing which could be performed at the same time as spin testing, which had not yet been completed. The company therefore arranged for a qualified test pilot, Carlos Garcia-Cabral, and his colleague, Shaun Fraser, to perform spin testing from Virginia Airport, Durban, on the weekend of February 13th. A progressive spin program was agreed incorporating discretion for the pilot to determine appropriate incremental steps and safety requirements.

During the first spin test flight the aircraft proved to recover immediately and predictably from incipient, one turn and one and a half turn spins, using conventional control inputs. The test pilot accordingly requested that the CG of the aircraft be moved backwards to its midpoint, the fuel quantity be increased and a second test pilot fly the next test with him so as to monitor and record the recovery with a film camera.  The aircraft was lost during this follow up flight.

ZU-TAF Arrives Oshkosh 2009

The pilots reported after the accident that in the new configuration the aircraft also initially recovered immediately and predictably from incipient, one and one and a half turn spins, including spins in which incorrect control and throttle inputs were intentionally used. The recovery characteristics of the aircraft from these spins led the pilots to believe that they could safely test it to two full turns, which they accordingly did. Following successful recovery from initial two turn spins, in the final spin of the flight the spin flattened, and notwithstanding their efforts, the pilots were unable to recover the aircraft in the height available. The agreed spin test protocol provided for the implementation of emergency procedures at 4,000 feet agl. At that altitude the engine was accordingly cut and the ballistic parachute deployed. Although the ballistic rocket fired, it failed to pull the packed chute through the parachute cover. It would appear that the weight of the chute and its shape was such that the force required was too great to breach the cover, which subsequent inspection suggests was fastened too firmly. This design is being addressed and testing will be performed.

Notwithstanding the failure of the ballistic chute, both pilots were able to exit the aircraft cockpit and deploy their emergency parachutes. Unfortunately the force with which Carlos Garcia-Cabral's canopy deployed caused him to suffer whiplash which fractured his C2 ad C3 vertebrae. He received excellent medical help and fortunately appears to have suffered little or no nerve damage. He is expected to make a full recovery.

ZU-TAF File Photo

Following the pilots' exit from the aircraft it recovered from the spin and impacted the water, approximately 200 miles offshore, in a gliding turn to the right. Although the aircraft remained intact and floated for approximately 2 hours, the search and rescue services did not attach a rope to it before it sank below the surface. The ocean current subsequently moved the aircraft and some 6 days later it has still not been found.

The Airplane Factory is currently awaiting the full written reports of the pilots. The company will also continue to consider all advice and input from experts as well as members of the public. The Airplane Factory expects to have a new aircraft flying by mid March 2010.

FMI: www.airplanefactory.co.za