By Johan Lottering

AS the Robinson R44 Raven II's engine spluttered Willem Boshoff (46) knew the odds. Barely a week before he had to land in the veldt with partial engine power-loss. The engineers had done a field repair by replacing the fuel pump, suspected to have caused cavitation. The icy familiar feeling came all over him, once again. The engine r.p.m. needle was dropping uncommanded. The red annunciator light glared on the panel, the aural warning in his headphones confirming his worst fears. There was no time to even ponder. His training kicked in. He immediately lowered the 'collective' lever to reduce the angle of attack on the main rotors, thereby reducing the load. He simultaneously opened the throttle. But, that caused the engine to quit completely. Suspended in midair Willem and his front passenger, the farmer whose lost Kudu bull they had been looking for, were in real troubleÖ

Today, months later, he still marvels that they had come away unscathed from not merely an under-developed autorotation, but full-fledged 'crash landing' atop a dense crop of trees. [An 'autorotation' is the helicopter version of a fixed-wing forced landing without power]. They were barely 35 minutes into a Part 127 game-spotting operation in his Robinson R44 helicopter. At that crucial moment, Willem knew he had to react 'super fast'. He also instinctively realised nothing short of a miracle would save them. These kind of situations are seldom survived. With only 40 knots and barely 150 feet height there were neither enough time nor any forward or downward momentum as potential energy to re-energize the ailing rotor r.p.m. needed for a safe landing.

The flight regime in which pilot Willem Boshoff was operating seconds before has killed many pilots and occupants in the game-capturing business. It is not called 'dead man's curve' without reason. They felt themselves hurling from about ten storeys high into the crowns of a patch of camel thorn trees. There were no other options. Just before impact he 'flared' real hard with the 'cyclic' stick, thereby changing the attitude nose-up to impact first with the strongest part of the structure, the skids and underbelly. When the severely damaged helicopter came to a dead stop, they unlatched their harnesses and ran to avoid the effects of an imminent explosion. Minutes later he realised he still had half tanks, they could have been incinerated.

Get the 'app'

Willem nowadays would urge fellow-aviators to pay close attention to the effects of high Density Altitude (DA). Since the accident he has loaded Timm Tuckers R44 Gyronimo Raven 2 app on his ipad and regards it as a life-saver. The app can be found via Internet search. It uses basic data to automatically determine safety parameters and automated warnings. Willem now observes strict self-imposed 'termination of operations' parameters by means of the app.

Above 28 degrees Centigrade he lands and waits for temperatures to subside. As he works in the Kalahari area with typical elevations around 4 000 feet in soaring temperatures, he is fully aware the lift generating abilities of the helicopters he fly can be severely impaired in high DA.

Vapour locks

However, he is now also convinced that above 28 degrees Centigrade an additional potential hazard emerges in the form of vapour locks in the engine's fuel injection system and lines. High ambient temperatures have been known to cause cavitation in engine driven fuel pumps of fixed-wing piston aircraft engines. The difficulty for investigators is that once the engine is started during a bench test, it has already cooled down after being primed - the very process 'masking' the original cause of inadvertent power loss].

Hydraulic switch

According to the formal accident report, which Willem considers highly controversial, the primary cause was inadvertent deactivation of the hydraulic system by the pilot. Asked to explain, Willem attributed the different findings to investigators not inspecting the helicopter at the crash site. He was led to believe that farm workers had climbed inside the cockpit posing for cellphone photographs, without authorisation. 'Anything could have happened, as they'd obviously fiddled with the switches and controls'.

Willem's instructor Martin Jacobs of Powered Flight confirmed training pilots for such possibility was part of the curriculum. He conceded such inadvertent action could 'take a pilot by surprise' as more strength would be 'unexpectedly' needed to maintain control. The helicopter would still be able to fly normally, though it might take vital seconds for the pilot to firstly recognise the condition and then adjust to it. He cited an accident some years ago when a pilot and passenger were consumed by post-impact * fire upon colliding with a hangar at Rand Airport. The hydraulic switch, next to the siren button, had been switched off inadvertently. Look and learn and fly safely!

[The lamented Robinson bladder tank modification may well have been a blessing in disguise in Willem's case.]

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