Day 30 - Lesson 16

Navigation exercise via Glastonbury and Warminster

Posted by Owain Abraham-Williams on Saturday 23rd January 2016

The weather was perfectly flyable today. However, the wind was blowing straight across the runway, not along it, meaning there’d be a strong crosswind; not the ideal conditions for circuits and certainly not for my first solo. So instead Derek suggests we do a navigation exercise.

I take out my half mill chart and recently acquired chinagraph pencils and start plotting a route via Cheddar, Glastonbury, Warminster & Radstock. Derek says to use the blue pencil as you can’t read details on the chart behind the line if you use the black one.

We study the map very closely, following the lines I’ve drawn. Derek asks me to look at what we’ll be flying over; towns, rivers, railway tracks, roads, lakes, etc. He also tells me to visualise key features to the right and left of our intended track and ahead of us. It’s really quite intense and I come to realise how much information is captured in the map that I hadn’t noticed previously.

We head out to the plane; today I’m in G-BCJN, the Piper PA-28-140 that was involved in an accident last September. I thought I’d seen the last of Juliet November, but they’d managed to repair it. The oil in the new engine was so clear, it was hard to see its level on the dip stick.

Take off

ATC give me my clearance and soon I’m lifting off from the runway battling against the crosswinds. Last week the wind had been been quite light, which meant the aeroplane took its time to climb as less lift was being generated by the wings. Today, with 20kt gusts, the wings had no problem lifting us into the sky and we were at 1,000 feet before I knew it, so I turned towards Cheddar Reservoir and flew away from controlled airspace.

As I fly over the reservoir Derek asks me to inspect my map, verify our location and identify the town to the left of us, which of course is Cheddar. Then we turn towards Glastonbury and Derek points out the Tor (a hill in Glastonbury which is easily identifiable as there’s a monument on top of it). He also points out the town of Street next to Glastonbury and shows how the two are separated by a river, as indicated on my map.

Derek explains that as I get more experienced I will need to prepare proper flight plans that take into account air speed, the bearings I need to fly, the forecast wind speed and direction so I can correct for drift and how long it will take to fly each leg of the plan. Today though he says we’re just enjoying ourselves!

Next we turn towards Warminster and en route I identify the TV mast near Wells (the tallest structure in South West England), the town of Shepton Mallet, how high ground is depicted on the map, and both disused and active railway tracks. Interestingly, disused railway tracks are specifically marked on the map as although they are not in use, they’re still a very good visual landmark from the air. Junctions in railway tracks (either disused or active) are also great visual cues as they are a prominent feature that can be used to very accurately fix your location.

We fly over the railway track heading into the town of Frome on our left and are soon over Warminster. I can be sure of where I am because I can see a bend in the railway track and a station which are shown on my map. I can also see from my map that it is a town in a valley, surrounded by higher ground. We turn back towards Bristol and fly past Frome again, still on our left (so we’ve flown right round it) and over the railway tracks now going north east away from Frome, not into it.

Returning to Bristol

I am on the lookout for the towns of Radstock and Midsomer Norton as these are just south east of Bristol’s controlled airspace. Once identified I radio Bristol Radar and ask for permission to rejoin the ATZ. I’m told to report my position to Bristol Tower so switch over to their frequency where I’m given permission to enter.

I can see Chew Valley Lake ahead of me and further in the distance Blagdon Lake. Derek asks me where the airport is and I point straight past it. It’s really surprising how difficult it is to identify prominent landmarks from the air if you’re not sure where to look.

Next I identify Barrow Tanks (the reservoirs near Barrow Gurney) and Derek tells me this is now just like being in the circuit. I note that the altimeter shows I’m flying at 1,600 feet when I’d normally be at 1,000 feet, so think I’ll have to descend faster than usual, but our profile is no different to normal.

It’s then that I realise I’m using the pressure setting for mean sea level (QNH), not height above the aerodrome (QFE). Bristol Airport is about 600 feet above mean sea level, so 1,600 feet above mean sea level is almost the same as 1,000 feet above the aerodrome. This also explains how I climbed to 1,000 feet so quickly on take off, because I was starting from 600 feet, not zero.

If you’re interested you can read more about Q codes and pressure settings in my Circuits at Cardiff post I wrote in September last year.

I turn onto final, descend towards the runway and am given permission to land. The crosswinds are still strong and my little aeroplane is buffeted from side to side on the approach. I try to counteract it by turning into wind with the knowledge that I’ll need to straighten up before touching down. The amount of corrections I’m having to do and the effect the wind is having is daunting. I try to round out and flare while kicking straight but it’s just too much for me to take in and I end up touching down quite hard.

I felt rather disappointed after this landing, but since watching the video I can see it was really rather hairy in that crosswind, so perhaps I was being a bit too hard on myself. Hopefully the weather will be better next weekend and I can finally go on my first solo flight.