Initially, this sounded like that the lesson (on the 12th of July) would be a pushover. Oh, boy, I was wrong.

It’s not too difficult to keep an aircraft flying straight and level once it’s at that point. What’s difficult, however, is being able to switch power settings and then being able to maintain that straight and level flight. I had a LOT of trouble with this. Not to mention the weather conditions – 15-25 knots at 330 (so, some crosswind for 35L/R) gusting to 30 knots. Needless to say, I didn’t do the landing today (although, it was quite nice on final and on flare).

Basically, there are four types of cruises: fast, normal, slow and precautionary. I can’t exactly remember the speed for these cruises (though I’m thinking it was 105, 90, 75 and 60 respectively), but the power settings are:

  • fast – 2500 RPM
  • normal – 2300 RPM
  • slow – 2000 RPM
  • precautionary – 2200 RPM, 1 stage of flaps

To maintain steady straight and level flight, one needs to maintain a constant amount of lift. The lift formula is:

L = \tfrac12\rho v^2 A C_L

where:

  • L is the lift force
  • \rho is the air density
  • v is the airspeed (velocity)
  • A is the surface area of the aerofoil (wing)
  • C_L is the lift co-efficient

The pilot can only influence three of these factors – airspeed, surface area of the wing (using flaps) and the lift co-efficient. However, in flapless flight, the pilot can not influence the surface area of the wings so this is ignored. Airspeed is correlated with the amount of power (using throttle) is applied. One component, according to the Thin Airfoil Theory, can be controlled by the pilot – the angle of attack. The TAT states that:

C_L = 2\pi\alpha

where:

  • C_L is the lift co-efficient
  • \alpha is the angle of attack

This is, of course, a highly simplified lift co-efficient. It’s good enough for the purposes for piloting, but before you aeronautical engineers cry foul, I know that there is no mathematical relationship between lift and AoA (for some light reading on this topic, click here).

So what does this mean for the pilot? Basically, control of lift in an aircraft correlated as such:

L \propto v \alpha

If the pilot increases their airspeed, the aircraft will gain more lift and will subsequently climb if the angle of attack is kept constant. If the pilot decreases their airspeed, the aircraft will descend if the angle of attack is constant. So, in order to maintain level flight, the pilot will have to reduce the angle of attack at higher power settings in order to maintain constant lift and vice versa for lower power settings. This means that, at the fast cruise setting, the nose attitude will be above the horizon marginally. At the normal cruise setting, the attitude will be about 3-4 fingers below the horizon and further below in the case the slow and precautionary cruise settings.

To change power settings and maintain level flight, follow this checklist:

  • Power
  • Attitude
  • Trim

In order to maintain straight flight, the pilot needs to keep the ailerons level and the aircraft in balance. This is done by putting more pressure on the rudder pedal on the side indicated by the balance ball on the turn co-ordinator (below). S/he will also need to use a reference point in the horizon in order to maintain a good heading.

This lesson was challenging, as there was a lot to learn about how power settings influenced the flight of the aircraft – and how to manage it so that it is straight and level. Add some atrocious weather conditions and you have a party! But, I guess, the challenge of flying is half the fun of it. Unfortunately, I wasn’t able to get a lesson for next week due to the club going on a fly-away, so I have booked my next lesson (on climbing and descending) on the week following.