Navigation Challenges

Thursday, 18th March

From the aviators point-of-view Wednesday 17 March was a disaster. The cloud base in Caernarfon had not got above 300 feet all day and there were frequent torrential downpours. No flying had been possible, and I'd had a good view of the inside of the hotel room all day. Handy for revision for ATPL exams, but useless for any practical flying!

Thursday was better: but not by much. It was clear that a land away was not really a possibility due to an approaching weather front that was set to degrade the weather further in Wales. Flying today would already be a challenge. The wind was 170 degrees at 25 knots with regular gusts up to 35. Phil and I decided that we would fly and that we would do some navigation exercises including diversions and position fixes as preparation for my commercial pilots licence (CPL) course.

We looked at the chart and decide that we'd route up the Menai Strait to Deganwy and then Phil would provide me with diversions, position fix and feature recognition exercises. It was going to be just like the flights we'd done three years earlier whilst I was training with Phil for my PPL.

The takeoff in the gusty wind provided no significant problems and we were soon heading North East up the Menai Strait at 1500 feet. Whilst passing Llanfairfechan we noticed a very large fire on a hill that was billowing smoke into the gloomy day. We reported our observation to Valley Radar who, after a brief delay, informed us that there was gorse burning in the area. Valley did however, thank us for our vigilance.

The first diversion was to Trawsfynydd nuclear power station. I quickly determined a heading and estimated time of arrival for Trawsfynydd, and climbed to an appropriate flight level for the track I'd determined. No sooner had I settled into the climb that Phil asked me to fix my position using whichever radio aids I wished.

I selected the frequency for the Wallasey VOR/DME station and listened to the identification Morse code. Following this, I determined on which radial we were and at what distance, and then used my all-in-one plotter to determine the position. Once I had determined the position, Phil asked me to confirm this using ground features. We were just west of Llanwrst using the town, the four roads into the town and the river running to the West.

Then came the next question: "what is your maximum drift on this heading given the forecast wind?" The forecast wind at this level was 195 degrees 45 knots and I knew the maximum possible drift (tracking at 90 degrees to the wind) at our speed of 100 knots was 23 degrees, which I had rounded up to 24 for ease of mental arithmetic. I knew this because I always mark the maximum drift on the chart along with the wind vector: another of Phil's top tips during my PPL training.

In the air there is not really enough time to use a flight computer to determine the drift, so estimates have to be made. More top navigation tips taught to me during my PPL were the 'drift star concept' and 'clock face technique', which allowed me to quickly determine that on a heading of 210 I should use one quarter of the maximum drift of 24 degrees. This gave me 6 degrees drift on our present heading. Performing the calculation with a navigation computer in fact gives 10 degrees, but for a quick estimate that can be made in the air, 6 degrees is not a bad.

We arrived overhead Trawsfynydd and the next diversion was to Pwllheli. A similar affair ensued with the track and estimated time being determined, and a position fix been obtained near the middle of the leg at Criccieth.

By this time the weather was closing in a little and we elected to route back to Caernarfon for a debrief and a cup of tea and wait for the approaching weather front to pass. Once again as we descended into the turbulent layer below 2000 feet we were in for a bumpy ride. We joined downwind left hand for runway 20 and the wind was now 160 degrees 29 gusting to 39 knots: a crosswind component of 18 knots in the steady wind and 25 knots in the gusts. This would be a very challenging landing, but by no means impossible in an aircraft as capable as the Bulldog, which has a demonstrated crosswind landing capability of 35 knots!

After a bumpy final approach and a very careful flare, we touched down and brought the Bulldog to a walking pace on the runway. We taxied straight to the apron and parked in front of the hangar, with the added bonus that the hangar shielded the aircraft from the brunt of the wind. Just to be sure however, we inserted the control locks to prevent the elevators and ailerons flapping around in the wind. By now the rain had started in earnest, and we both ran inside for a well-earned cup of tea.

In the café I drew the route that we'd flown onto the chart and compared the headings and timings with what we'd actually achieved. As it turned out we'd been fairly accurate on most of the route, but the leg between Deganwy and Trawsfynydd had taken 29 minutes: about five minutes longer than the theory would suggest. This was possibly due to the wind, which was practically all headwind on this leg, been stronger than forecast.

After the weather front had passed and the heavy rain had stopped, Phil and I decided that we'd make one more flight. This time we'd tour Anglesey from the South in a clockwise sense. This would be a flight at low level in weather that was just barely visual flight rules (VFR). The visibility was about 4km and the cloud was overcast at 1500 feet and few at 500 feet. We'd transit Anglesey at 1000 feet in the murky and bumpy weather as an exercise in low-level navigation in poor weather.

Despite the dreadful conditions, the flight was proceeding well and the aircraft was coping superbly. Holding the height at 1000 feet was not difficult despite the regular turbulence, and the airspeed fluctuations were manageable. Once again the Bulldog was demonstrating its immense capability.

We asked Valley for a MATZ transit at 1000 feet, which was approved. This enabled Phil to get a photograph of the airfield as we passed overhead. Despite being only been at 1000 feet, there was so much moisture in the air that Valley was partly obscured in the mist.

We continued to the North past Holyhead and routed to the coast at Amlwch, carefully avoiding the restricted airspace at Wylfa nuclear power station on the Northern coast of Anglesey. We made several orbits at Amlwch for our friend and fellow pilot Andy Reay to see, as he was working in Amlwch that day.

Routing back down the Menai Strait the ride was getting bumpier, but Caernarfon was now in sight. We couldn't see the mountains now, and from this we estimated that the visibility had deteriorated in the hour since we'd departed. We changed to Caernarfon Radio from Valley Radar and, as the circuit was clear, we elected for a straight in approach to runway 20. The wind was a little stronger now at 32 knots, but the gusts were not as significant as they had been earlier. The landing was smoother than the previous one, and the fact that the wind was now practically straight down the runway helped greatly.

We'd had another good day out, but this time in poor weather. Most definitely though this kind of flying had been beneficial and had further improved my confidence in marginal conditions. Back in the café, I responded to the telephone messages I'd received regarding the evening dinner at the Garden Chinese restaurant in Bangor. After signing the paperwork for the days flying, I headed back to the hotel to make myself ready for the evening out.