Some simple exercises

Now we are properly airborne, it is time to leave the airfield and try a few manoeuvres. We start by banking about 10° to the left to make a gentle turn on to a course of 90°. We are now approaching 3000 ft and need to level off into straight and level flight. Nose down, let the speed build and, as our cruising speed of 90 knots approaches, we gently throttle back to the cruise engine setting of 2300 rpm. Finally, when things are nicely settled, we use the trim to remove the control force and find the aircraft flies quite happily ‘hands off’. Every 15 minutes or so we do the ‘FREDA’ checks to make sure that all is well:

Fuel – have we got enough?

Radios – on correct frequencies?

Engine – temperature and pressures OK? Pull out the carburettor heat to the on position and check for a small fall in engine speed and a return to the pre­vious speed when the carburettor heat is turned off. This check ensures that we haven’t inadvertently started icing up the engine.

Direction finder – does it read the same as the magnetic compass? (The DF is a gyroscopic instrument and tends to drift slightly with time).

Altimeter – is it set correctly and are we at the correct height?

Checks complete. Now to try a few manoeuvres. First we pull back slightly. After an initial climb, the aircraft settles to a lower speed of 86 knots. We can reset the throttle to remove the subsequent tendency to slowly gain height but as we were flying fairly near the minimum power setting, not much movement is necessary. To speed up we do the opposite; yoke forward and increase throttle slightly to prevent sink. Unlike a car, we do not use the throttle as the speed control, although it may need some slight adjustment. The main thing is to control the angle of attack with the elevators – pull back to slow up and push forward to increase speed.

Now let’s try a descent to 2500 ft. Throttle back to 1500 rpm. When we do this we have to remember that carburettor icing can be a real danger, even on a fairly hot day. We don’t want the engine quitting on us; we have only got one! So we pull on the carburettor heat control, which directs the engine air over the hot exhaust manifold, before it enters the carburettor. We need some slight control input to cope with the change in engine torque and the change in pitching moment, due to its offset thrust line. When we have settled into a steady descent (a descent rate of about 500 ft/min on the rate of climb indi­cator) we can again trim the aircraft, so that it will fly ‘hands off’ in the steady descent. In spite of these other small effects, the main effect of the power change is that the aircraft settles into a steady descent. As 2500 ft approaches, all we need to do is to pull back slightly to level out and return the throttle to the cruise setting (don’t forget to turn off the carburettor heat) and finally retrim in level flight.

Now climb back to 3000 ft. Full power first – we don’t want to lose speed. Pull back slightly until the speed falls to 70 knots (best rate of climb). Trim when things have settled. As we reach 3000 ft, push forward into level flight. Then, as we reach the cruising speed of 90 knots retrim when things have settled. Quite simple in a well-behaved aircraft like this!

Next a stall. Throttle back to idle (carburettor heat to on). Gradually pull back so that no height is lost. Notice as the speed reduces that the controls start to have a ‘soggy’ feel. As the speed drops off and we continue to raise the nose the increased angle of attack causes the suction peak on the top of the wing to move towards the leading edge. Eventually we here a buzz as it trig­gers the stall warning device which detects the pressure near the wing leading edge. When we hear this, we are only a few knots above stalling speed. Normally we would push the yoke forward to reduce the angle of attack (yes, even if we are near the ground!). Now, however, we press on raising the nose, as we wish to experience a stall. We are now down to 45 knots, and, in spite of our efforts to raise the nose, it drops and we have stalled. We entered the stall flying straight and level, so nothing very exciting happens. To recover; push the yoke forward, turn carburettor heat off and select full throttle. As the speed builds up to the cruising speed we pull back to level out and reduce the throttle to the cruise setting.

We tried a gentle turn when we were leaving the airfield circuit in a climb. Now we will try to do some level turns. As with most flying, the secret is to keep your eyes on the horizon. We check for other aircraft from right to left (the direction in which we are going to turn), bank gently to 10° (indicated by the scale outside the artificial horizon) and try to keep the line of the horizon constant in the windshield. Note that, as we get to the required bank angle, we have to remove the input to the ailerons and even reverse them slightly to hold the correct angle. This is because the wing on the outside of the turn has a slightly higher airspeed, so the centre of lift moves slightly towards this wing, promoting a steeper bank than was aimed for. However, the correction is made instinctively and careful observation is needed to see what has happened.

A glance at the altimeter shows a slight descent, so a little backpressure to bring the nose up. (Note that the rate of climb indicator has a response that is too slow to be of use to us here). A glance at the ball in the turn and slip indicator shows a small degree of sideslip. Because the wing symmetry has been disturbed by the increase in speed of the outer wing, there is a slight tendency for the aircraft to yaw away from the turn due to the asymmetric vortex drag. This is countered by a bit of left rudder. It sounds simple but things can get a bit confusing with an over-correction sending the sideslip the other way. Thankfully a simple rule resolves the problem; if the ball is on the right, add right rudder and vice versa.

Now let’s be a bit more adventurous and try a steep (60° bank angle) turn. This seems a lot more hairy as we are pulling a load factor of 2 (remember how the load factor goes up in a turn). The principles are the same but a lot more difficult to control under these circumstances. Additionally we will need to add some power or we will not be able to sustain speed and height. As we know, the power required goes up in a turn. In the shallower turn we were able to leave the throttle as it was and trade off a bit of speed (as we were above the speed for minimum power). Now we need a bit more from the engine to keep us going round at constant height. A check for other aircraft and round we go. The increased load on our bodies makes it quite difficult and, even when we have established a nice level turn, it is not easy to roll out on exactly the right heading and throttle back to re-establish straight and level flight.