Ab Initio 40: “Navigating the Showers”

In which a howling crosswind gives me an excuse to get out of the circuit and do some ‘best guess’ navigation to lots of places beginning with Ll.

“Bright and breezy with showery spells,” said the TV weather. This turned out to mean, in real terms, “Howling crosswind and intermittent downpours.”

Nevertheless, off to Pembrey I went. You have to love an airfield where a query about the weather is met with “Well there’s a crosswind as usual.”

Seeing as both the instructors, and I, rather wanted the aeroplane returned in one piece, solo circuits were off the menu today, and we decided in favour of a little chart reading / navigation exercise instead.

I was flying today with the new part time instructor, Carl. (new to Pembrey, not to instructing — day job is flying the post!) It was a bit odd at first having someone different sat there, though not as off putting as I think I’d have found it earlier in my training. At least I felt reasonably confident that I wouldn’t get anything too embarrassingly basic very wrong…

Carl picked Llandovery as our destination, pointing out some of the useful landmarks, and that it had some good line features, roads and railways all running up the valley towards it. I didn’t think there’d be much hope for me if I couldn’t follow all of that!

There’s a river as well but he mentioned that rivers aren’t always as easy to see on the ground as they are on the chart, as they’re more easily obscured by trees and overgrowth.

Llandovery is northeast-ish of Pembrey so I estimated a nil-wind heading of 045. (Measured back on the ground it was 050 which wasn’t exactly spot on, but close enough to mildly surprise me)

The strongish north wind was going to blow us to the right of that so we decided to steer 035 and see how it worked out. With all those line features we’d soon know whether we needed to allow more or less for the drift.

An estimate for the distance was done measuring using the top joint of a thumb for ten nautical miles and this gave us about 30nm. (measured later with a scale rule gave 27nm)

Doing 90 knots and not allowing for wind would have us covering the ground at 1.5 nautical miles per minute so Pembrey-Llandovery would take about twenty minutes. Plan was to look at how long it took us to get to a radio mast about 10 nm along our track, see how much the wind was slowing us down and re-estimate our time at Llandovery from that. We’d also at that point be able to see whether we were on track or not. If so, the mast should be about a mile to our right.

Well that all sounded simple enough on paper. I was looking forward to seeing how it worked out in the air!

We looked next at a safety altitude and the airspace for the route. That mast was the highest thing near enough to be a concern, at 1522′ so we decided to fly at 2500′ to allow a good margin but still keep us under the cloud. No controlled airspace nearby, we’d be well beneath the airway L9, and we’d stay aware of the danger area to the northeast of Llandovery. If we overshot too badly we’d be in that, and it’s an artillery range up to 50,000′! Not tempting.

I trotted out to the aeroplane and did the checks, then Carl joined me and off we went. We climbed in the circuit to depart overhead and take up our heading of 035. Gross error check before we hared too far off, so a look out to check Kidwelly was under the left wingtip so we were pointing in the right direction at least!

The weather was still suffering “showery spells” and though they were pretty easy to spot and route around, there were some decidedly claggy moments which would probably have been cause to turn back had it been a solo exercise. It was also rather on the bumpy side.

Carl though seemed to think it was a good learning exercise–“If it had been clear you could have seen Llandovery from the circuit, and where’s the challenge in that?”

We were due to cross the M4 motorway just before reaching our mast and for some reason I didn’t see the road until we were almost on top of it. Carl had already spotted it and also pointed out a small lake.

“Can you see a small lake on your chart”.

Um, no. Not in the right place I couldn’t. The only one I could see was before the motorway and we’d just crossed that.

After some umming and ahhing from me, Carl pointed it out. Right at the base of the mast! So we were on track, even if the mucky vis meant we didn’t see the mast itself for another mile or so. I hadn’t spotted the lake when we were picking landmarks but in the weather conditions it was much easier to see from a distance.

Next en route landmark was Llandeilo. Nice and easy, lots of roads going in, and the river and railways going through it.

Llangadog, the next town along wasn’t as simple. Both it, and nearby Llanwrda (still following these names?) had roads diverging out and at both, the railway crossed the river on a bridge. If we were on track then Llangadog should have been to the right and Llanwrda just after it to the left. In fact it turned out to be Llangadog I was looking at and we were a bit right of track.

Llandovery was coming into view by now though now so it wasn’t too much of problem. We did a quick orbit overhead to check we were where we thought. The river and the road split into three at the town and the railway followed the middle branch. It was also the only town in a long way, big enough to warrant a square instead of a circle on the chart.

“Alright then, let’s go to Carmarthen,” said Carl. “What heading do we want?”

I guessed 240 when it was more like 250 and with the wind as well we ended up steering more like 260. Just over two thumbs away, so 20ish nautical miles and about 12 minutes flying.

For landmarks we had Llandeilo again, this time out to the left of us. Not as far to the left as it should have been by the time we passed it though. Either my steering, or the wind had put us rather left of track and we ended up tracking almost due west along the river and past the botanic gardens (“glass dome” on the chart) towards Carmarthen.

“How do we know it’s Carmarthen?”

Motorway the biggest clue, closely followed by 90 degree change of direction of the railway track which comes in from the south and goes out o the west. The river broadening out into the estuary, and again the fact it’s the largest place for some distance. Big enough to be a ‘Carmarthen-shaped blob’ on the chart.

Pembrey from here was easy. One thumb due south (well, 9nm at 185 in fact), and from here you could already see the ‘dent’ in the forest which marked the extended centreline of the runway.

While I got us pointing in the right direction and trimmed, Carl drew an overhead join on the edge of his pad. We’d be using 22 and were coming in almost due south so it would be quite easy to just move to the deadside as we got close and descend to rejoin the left hand circuit.

We called Pembrey. The radio wasn’t the clearest, though we could hear Laurie and his student on the ground quite clearly. Overhead we could see them waiting at the hold. This is the way it’s supposed to work and hopefully, had we not been the only aeroplane about, we’d have seen anyone else in the circuit too.

They waited for us to pass and started rolling as we turned downwind.

22 was a pretty arbitrary choice at this point as, on the ground, the wind was still straight across and the crab angle coming down final was enough to make my hair stand on end. I did straighten it up with a lot of wingdown by the time I landed but it was a bit of a thump!

I’d enjoyed the trip though. Pleasant change of pace and gave a nice overview of how all this navigation stuff is meant to work. I think it’ll be easier to get to grips with the full planning gubbins having had a bit of an overview and the ‘rough guess’ version.

Looking forward to it!


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