Flying straight and level

After a gap of a couple of months, I get aloft once more and learn an unexpectedly tricky manoeuvre: flying in a straight line without turning, climbing, or descending.

It's been a bad Spring for the Flying Group. After a Winter of bad weather, we had one of our two Moths in for repairs for all of March and April, and the second one away for its 50-hour inspection for the last couple of weeks. April also saw a closure of Cambridge Airport. But suddenly everything has come together: runways in good condition, both aircraft serviceable and ready to fly, and April's blustery weather replaced by May's calm and sunshine.
Two Tiger Moths on grass parking
Two Tiger Moths ready to fly. This has been a rare sight lately. The weather is a lot better than it looks in the photo!
Even though the weather has been warm enough for shorts lately, it's a lot colder at 3,000 ft, so I put up with sweaty legs in my jeans on my way to the aerodrome. The Winter gloves stayed at home, but I still had to don a couple of layers under my thick leather jacket.
I've run through the pre-flight actions a few times before, so it wasn't long before we were sat in the cockpit ready to start the engine. I was a little nervous of flying again: the gap has been long enough to forget how comfortable it feels when I'm in the air. There was a little extra reason to be nervous today: my mate Chris, who is also learning to fly, was in the other Tiger Moth behind me, so if I went wrong I knew I could expect some mockery later.
Once again I got to taxi us out to the end of the runway. I think my taxying has improved a lot: though I remembered to make clearing turns to left and right, we didn't weave across the whole width of the runway like usual. There was a brief pause at holding point juliet while a home-built plane that looked like a toy landed in front of us. After that, we made quite brisk progress to the end of the runway: at one point, my instructor even shouted at me to slow down. It was quite hard to maintain a steady speed. Because of the small bumps all over the grass, it needed a lot of throttle to start moving, but if I wasn't quick enough to reduce the power, the aircraft would end up going too fast. It's a lot harder than in flight, where you can just set the right power and then leave the throttle alone.
Still, before long I got to experience once more the slightly uncomfortable feeling of the airplane flying under someone else's control, as we climbed away from the runway. The tower had advised us to turn left after take-off, so we did so as soon as we'd crossed above the aerodrome's boundary fence. We continued climbing as we turned onto our new course towards the local practice area: an area with a good landmark nearby, but not over the town, and not on any major routes.

It was now time for me to take the controls and build on the earlier lesson about their effects. It's one thing to know that pitching up tends to reduce airspeed and increase height, but it takes continuous adjustments to maintain a desired airspeed, height, and course. First I had to set cruise power with the throttle: decreasing it slowly from climb power until the tachometer reached 1950 rpm. At this setting, the aircraft ought to maintain level flight at about 80 mph. Like my attempt at flying the circuit, I had to judge the attitude of the aircraft against the horizon, and also keep one eye on the airspeed indicator, to correct the speed by pitching slightly up or down. That went a lot better this time - I managed to always push the stick in the correct direction - but we were still very wobbly.
This time I also remembered to keep the aircraft in balance, using the rudder to make sure we were flying straight and not sideways through the air. One thing that really struck me was the big difference between using the rudder on the ground and in the air. On the ground, because the rudder has a skid to steer the tail of the aircraft, I really need to push hard on the pedals to have any effect. In the air, however, because there's little resistance to its movement, and because the airflow over it is so much faster, it only needs tiny changes to have a big effect. Before I realised this, I overcompensated a lot, swinging the aircraft from one side to the other, and making the side-slip indicator wobble about like a pub sign in a storm. But once I appreciated what was happening, I found it much easier to control. It's not so much pushing the pedals to move them, more about changing the pressure from one to the other.
Close-up of the tail skid on a Tiger Moth based in Germany. The control cables for the rudder and elevators are also visible. The story that goes with the photo is pretty interesting.

After flying moderately straight and level for a while, we practised turns. I was comfortable with these from earlier lessons, and managed to maintain a good bank (roll) angle while also keeping the aircraft in balance. I did have a bit of a hard time keeping the nose up. When you roll, the lift generated by the wings is no longer acting straight upwards, so there isn't enough lift to balance the weight of the aircraft, and it will descend slowly. To counter this, you have to "pull up" slightly, but if the aircraft was in trim before the turn, it'll keep trying to level the nose again, so you have to keep up the backward pressure on the stick to stop it.
Next up was maintaining a rate of climb. First I had to increase the throttle to climb power, slowly inching it forward until the needle of the tachometer wavered around 2100 rpm. It's not as easy as the dials in your car: the needle doesn't settle on one number, but jumps and wobbles about like a pressure gauge in a disaster movie. Right away, the airspeed started to increase, so I had to pull back on the stick to pitch up, holding the right angle until the airspeed decreased to 65 mph, which is the speed for best rate of climb. The instructor told me to judge it by keeping the bottom of the cabane struts against the horizon. The cabane struts are the vertical ones either side of the front cockpit. If you look at the earlier photo and imagine me sitting in the rear cockpit, my eye line is about level with where they join the fuselage, so that angle of pitch is about right.
By the time our speed stabilised, I was pulling back on the stick quite hard. Because of the tendency to level off, the nose kept lowering, causing the airspeed to creep back up. To fix this, I moved the trimmer in the same direction I was pulling, until the stick stayed in position on its own. I found trimming the aircraft a lot easier than when I was trying to fly the whole circuit.

After some more climbing and descending, we had a quick illustration of the secondary effect of power. I trimmed for level flight, then the instructor told me to take my hands and feet off the controls completely. We were still almost as stable as when I was flying the aircraft properly! Next he told me to open the throttle wide. I did so a little gingerly, and kept my right hand near the stick, anticipating what would happen. The nose came up alarmingly, and we started to roll and yaw to the right. I felt like we would stall any moment, but the instructor was relaxed. It's easier to keep your cool if you know exactly what the limits of the aircraft are. After a few moments of flying out of control, he told me to recover. I eagerly grasped the stick, and pushed forward and left to level off. At the same time, I put a little pressure on the left pedal, to bring us straight again.
Once recovered to straight and level, we did the same exercise again, but this time by closing the throttle completely, to idle power. This is the same thing you do to simulate engine failure. As expected, it had the opposite effect, as we pitched down, and rolled and yawed to the left. This felt even more alarming than the climb, like a fighter that's being shot down. For several seconds we were falling out of the sky, until again the instructor told me to recover. This time I started by increasing the throttle to cruise: we wouldn't be able to maintain level flight without power. That stopped us falling out of the sky, but again I had to use the stick to bring us level, and the pedals to straighten us up.

The next exercise was similar, but with the trimmer. After trimming for level flight, I had to take my hands off the stick while the instructor pushed the trim lever all the way to the front, making the nose drop. I then had to recover to level, and re-trim the aircraft. I was surprised by how easy it was this time, especially as I had trouble judging the correct trim earlier. That was the last thing to do before flying back home. Once we'd navigated as far as re-joining the circuit (with a standard overhead join, if you're interested), the instructor handed back control to me. I had to descend to circuit height while turning onto the downwind leg.
If the previous lesson was hard because I had to do everything at once, this one felt much more relaxed. I had plenty of time to monitor our altitude and airspeed, while also looking out to check our attitude against the horizon and watch for other aircraft, and keeping the aircraft balanced with the rudder. It all seemed to work a lot better this time, and I kept the downwind leg parallel to the runway. The turns onto the base and final leg, and the descent, also felt a lot easier than last time, until the instructor

In a way, that summarises the whole flight. I felt like I hadn't really learned anything new in particular, but everything felt a lot easier. In the case of balancing with the rudder, I could feel it getting easier and having to think about it less even over the course of the hour. My reactions when controlling airspeed and roll angle were a lot better and more natural. I might even worry about getting cocky about how good the improvement was, but I know there are lots of tricky things I haven't even started learning about yet. I get a reminder of this every time we land. I follow through every time, but the movements of the stick and pedals are so dramatic it still feels totally beyond me. In a way it's very scary, but at the same time I know I'll get a lot more flying practice before I have to do it myself.

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