Arcing up

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image: © Leon Homan

It was a simple, mostly harmless event, but it embarrassed an experienced pilot and caused him to ponder his attitude to risk.

I had been tasked to fly a Pilatus PC12 from Adelaide to Port Lincoln on an evening flight I had done many times before. My shift began after sunset and I arrived at work to check the weather, file a plan and prepare the aircraft. All was good with the aeroplane and flight planning, but the weather was something else. Although there were no storms in the vicinity of Adelaide, they were forecast on my route, albeit with a 30 per cent probability. Standing on the apron, I could see the electrical activity was mostly to the south and southwest, with nothing directly on my route, and a very high cloud base. I was not particularly concerned at this point, as I had flown many times in similar or worse conditions, and was confident I could avoid the isolated storms if I kept visually to the north.

On departure, I contacted Adelaide approach and was initially cleared to climb on course without restriction to flight level 180. Shortly after this however, I overheard an inbound flight asking for weather diversions to the south of his track, and as expected, I was immediately contacted by approach and told to maintain 10,000 due to traffic diverting into my airspace. This was no problem of course, and it gave me additional time to check out the storms that were still to the south and southwest, well away from my track. Besides, if an aircraft was diverting into my airspace, then that should be additional confirmation that my route was clear. Well, that was my reasoning anyway!

Seven minutes later, I was re-cleared to FL180 and I went up without any qualms, entering cloud at around 12,000 feet. The weather radar was tested and operating, and showed nothing of significance in the vicinity at this time, but as I levelled at FL180, I experienced quite a bit of chop and light turbulence. This was more annoying than anything else, so I determined to remain there a while and see if it didn’t improve shortly. The controller was also quite busy at this time and the frequency was unusually congested.

I was still trying to get a word in edgewise on the radio, when I noticed the familiar, low-level growl in my headset, indicative of static buildup and possible imminent lightning strike. My finger was on the PTT, waiting to get a call out to ATC, when I was startled by a very bright and very close lightning bolt in the upper left field of view, associated with a distinct though not loud ‘pop’ over the radios.

At that time, I didn’t think it had been close enough to have hit the aircraft, everything was operating as it should be and the aircraft was evidently happy. Nevertheless, I got onto the radio as soon as I could and asked for a clearance to a lower level to get out of the cloud. This was issued immediately, and I started down, initially for 10,000 ft. Passing 12,500, I was clear of cloud, so I decided to stop my descent at that point and level off at 12,000.

The remainder of the cruise and descent was quite normal, and it was only as I arrived in the circuit and started my pre-landing checks that things started to go awry. Immediately after the undercarriage was selected down, I had a bus tie circuit breaker pop, associated with master caution and chime (lights and chimes at night are not necessarily what you want!). I reset the circuit breaker and cancelled the master caution, and things returned to normal for about five seconds before it all happened again! At this point, I was about to turn base, had three greens and the flaps were travelling fine, so I was content to continue with the landing and sort the problems on the ground. I flew a normal approach and landing, completed my after-landing checks as I exited the runway, continued to the apron and shut down.

After exiting the aircraft, I inspected it thoroughly to see if I could find any evidence of a lightning strike. There was a small burn on the right wingtip at the trailing edge, and the carbon fibre filaments were exposed. OK, that was confirmation that the strike had indeed been on the aircraft.
I didn’t find anything else at this point, but it was clear I couldn’t continue until the aircraft had been thoroughly checked over by an engineer and cleared to return. I was stuck for the night!

The next day, the company sent an engineer over to check my aeroplane and see that there was no serious or lasting damage, and fix my electrical problem too. As it turned out, the electrical problem refused to show itself again (not uncommon of course), and there was no magnetism in the propeller or gearbox. There was a small burn mark on the aft fuselage, which was the likely entry point, but it was well clear of anything delicate or critical and was deemed to be benign, so we were good to go. We flew home VFR on a permit-to-fly, and the aircraft was placed unserviceable on arrival pending a more thorough check.

So, what could I have done differently in order to avoid this situation? Well, for one, I could have not flown at all! This was not an ideal situation as I was tasked there for a reason. However, there was no real pressure to get the job done there and then. I could easily have waited an hour or two and gone later when the storms had passed through. Similarly, I could have diverted further to the north, but the inbound traffic had come from that area, so that would have put me closer to trouble instead of further away.

Probably the best thing I could have done was to simply stay below cloud and in VMC so I could see any activity. The PC12 is quite happy at any level, and I had plenty of fuel for the trip, so my only penalty would have been an additional fuel burn of maybe 45kg (100 pounds). No big deal. My only reasoning for going higher was the better glide range in the case of an engine failure over water (and at night). This is something of course that needs to be considered, but in a turbine aircraft I was statistically much less likely to have an engine failure in the first place, so perhaps my thinking was flawed in this area—much better to stay VMC, even at 12,000 feet.

I had been comfortable in my decision to go, based on the forecast and the observed storm activity. I had been flying for more than 30 years, and often in much worse conditions—the only time I had witnessed a lightning strike was as a passenger! I considered the conditions would be relatively benign on my track. Clearly, I was wrong.

Obviously, the best solution would have been to stay on the ground, and if it had been simply a private flight, I would have. But that raises the other question of get-there-it is … just how much do you need to get there? Is it worth the risk in the first place? Have you taken reasonable measures to avoid unnecessary risk? Do you fully appreciate the risks?

On that night, I have to say I didn’t.

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