PPL Lesson #20: Second nav route and stealth MATZ penetration

Well, a proper mixed bag for today’s nav session. Maybe I should have taken the misbehaving oil filler cap I encountered on my pre-flight checks as a portent and just gone home but I didn’t, and, after the engineer switched out the worn o-ring so that it would tighten properly, we set off for Thame.

Before we delve in, here’s the Skydemon track:

Learning from my issue last time where I was off course before I began, and also because we can’t depart straight north from Blackbushe due to noise abatement, I’d planned to overfly a local landmark 8nm away as my first leg before turning to Thame. However, I wasn’t sure if this undermined what my instructor wanted me to do as he’d mentioned needing to adjust height as we go due to the lower 2,500’ LTMA shelf, which my new route completely bypassed. As such, I’d drawn both the 2-leg and the direct route from Blackbushe to Thame on my chart (yes, you can see where this is headed) meaning to scrub the other one off before we set off once I’d agreed the route with my instructor. Well… I didn’t, and ended up looking for landmarks along the wrong route for a bit.

Still, once I was looking at the right track the reference features I was looking for - chiefly RAF Benson and Chalgrove Airfield - on that first leg let me know I was heading in the right direction. The other main issue with that leg was altitude. It was the first time I’ve flown with significant haze, and without a horizon to reference I struggled more than I ever have to get the aircraft trimmed for straight and level. That combined with an overly firm grasp of the yoke meant that every time I shifted in my seat to look for landmarks I would inadvertently dip the nose, deviating from my planned altitude and only noticing when I did my next altimeter scan. We eventually made it to Thame at the right time and only slightly left of track, so after repositioning overhead I then turned towards Didcot. I was not prepared for what came next.

Our heading of 241° was essentially directly into the low winter sun, and it felt like I may as well be flying in IMC for all I could see straight ahead. Certainly my visibility of the ground straight ahead was limited only to whatever was reflecting the sunlight back at me - essentially just the rivers and larger flat-roofed buildings - through all the highlighted scratches and swirls on the cockpit canopy.

Something else odd happened on second this leg, and other than a big shift in the wind I can’t really think what happened for me to end up on the outskirts of Oxford rather than overhead the power station at Didcot. The compass and DI were well aligned (instructor confirmed, and I’d checked both before and after the turn at Thame and at the midway point), I’d consistently flown the intended heading of 241° (again, instructor confirmed), my planned track (234°) was correct and with winds at 260@25 I’d properly accounted for wind drift with the whizz wheel during planning. The track I ended up flying was closer to 250°. Messing around with the whizz wheel after I got home, it would have taken something like a 40° southerly shift in the winds at 25kt for my heading to have ended up with that track. I can only think I twiddled the DI the wrong way, neither of us noticed for the whole leg and as a result I was flying 10° off the intended heading. If anyone can spot or suggest what I did wrong I’d be happy to hear it.

Eventually I corrected and ended up overhead the power station at Didcot, and I could finally turn away from the hateful sun and head back to Blackbushe. Visibility on this leg was probably similar to the outbound leg but it felt crystal clear after staring directly at the sun for the previous 13 minutes, and I flew pretty much directly down my intended track all the way back to Blackbushe picking out my references on the way.

I felt a bit crestfallen when we got back to the clubhouse, but after a debrief with my instructor I’m probably being a bit too harsh on myself. He couldn’t quite fathom what went wrong on that second leg, and reflected that my altitude keeping was only really thrown off by the poor vis and trying to peer through the haze to see my reference points. Apparently it went well enough that we’re adding a diversion to the next lesson (on Monday) so that’ll be fun!