What has 53 nipples? Part 2: Return of the Kwaka.
Not my photo. Thanks Flying Red Bulls.
Helicopters are not designed to cut trees. Period. When they do, it makes history and as with all history and the current lack of equipment to aid time travel - it’s there forever.
When a helicopter rolls out of the factory every moment in time is recorded. Where it was sold, disassembled, shipped, registered, reassembled, flown, fixed, stored, owned, reconfigured, modified... and damaged. All these moments in history are expected to be recorded in the airframe or engine logbooks and over a lifetime a helicopter accrues a massive amount of history both good and bad. Good stuff is readily noted. Bad stuff, not so much and while it is a legal requirement and incumbent to record both good and bad, there is room for the unethical to gloss over details.
For instance - like the situation when a helicopter cuts a Eucalyptus tree into bite size pieces completely destroying the Main Rotor Blades but thanks to a set of used blades (that had been healing themselves in the back shed) is returned to service a few hours later...
This incident is called a Sudden Stoppage and it is significantly bad. Imagine seeing in slow motion that first Main Rotor Blade swinging just below the speed of sound towards the tree. The distance closes and leaves are blended into green mist before the leading edge melds into the trunk. At the very moment of impact the kinetic energy is transformed into a torque reaction that completely stops that blade and the kinetic energy becomes a shock wave transferred along the spar, through the grips and down the mast to be disseminated through the gears, shafts and eventually the casing mounted to the deck of the airframe. History is made and microscopic fractures begin to propagate.
Over the course of my pilot career, it has become apparent that the really important stuff is taught by surviving the mistakes you or someone else makes on your behalf. For all the important stuff my Air Transport Pilots Licences suggest I know, nothing in any pilot curriculum educates you what to expect after mistakes are made. The message is always to trust engineering and when a pilot understands how complicated engineering is, then it’s a relationship that you should never question. It is difficult to comprehend when the people you trust to keep you safe, decide to make illegal and selfish decisions that erode that law of trust. This was the case with the Bell 47 vs Tree incident. Every reaction has an opposite or equal reaction and while primary damage was sorted out with a “fresh” set of rotor blades, the secondary damage was evolving as every subsequent hour flew by.
Some months later I was working the Bell 47 on a survey job with a crew of three and through the day the oil pressure gauge had been fluctuating and each time slowly returning to show less pressure than before. Knowing something wasn't correct I returned to base to be told by the chief pilot that I just needed another quart of oil and to hurry the shut up and get on with it. We made it to the last lift of the day and after verticalling out of a confined area, I was passing 40 knots when the engine oil pressure gauge slowly went to zero. I thought a four letter word and looking around at the lack of autorotation options (not helped by my low altitude) quickly decided to climb.
Thinking a seized engine was seconds away and with nothing to lose, I gave the old 47 maximum manifold pressure and prayed for altitude. Seconds turned to minutes and while the pressure gauge was dead, the engine was pulling strong. I turned towards home and kept the climb going. Underneath was no good options but being only 15 miles from base I knew the escarpment gave way to grazing land halfway there. A Bell 47 has class leading autorotation characteristics, so being as high as possible was the priority and I sweated every second as the hundreds of feet became thousands and the options for a successful emergency got better.
At 3000 ft I had pushed my luck enough and with options below I entered autorotation and headed to earth. The landing from the autorotation was unexciting but as the blades coasted to a stop, new information presented in the form of a disturbing sound. Something rotating behind the cabin sounded like that proverbial monkey chewing nuts and I immediately knew that by climbing high - I’d inadvertently put myself into a worse position.
An engineer presented and the “rock catcher” at the bottom of the engine was drained to present a sea of stone grey oil interspersed with iceberg chunks of gear pieces. I had just learned emphatically that the main transmission and the engine of a Bell 47 share the same oil network and the loss of oil pressure was the result of gears being ground into submission before finding their way to the block the oil pick-up.
We had been on the verge of a catastrophic failure. We had been close to death and the damage from the sudden stoppage had finally been evidenced.
I left that company soon after and I am not sure what the moral of the story is. I know the Bell 47 is clearly bulletproof and I learned many things about peer pressure and to only trust engineers to a limit. I survived my mistakes and the mistakes of others to become a better pilot.
It's good to be humble as a pilot because we all make mistakes and as it is said....
If you don't like this mistake, wait five minutes because there's a fresh one brewing.
Stephen Boyce.