Straight & Level Flying

In which I discover that flying an aircraft in a straight line at a constant height is harder than it sounds.

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After two weeks of study/exams (ew) I was back to Lilydale for my next lesson… Today the topic was ‘straight and level flying’.

First there was the usual briefing where we discussed what we were going to try today. First we talked about what straight and level flying actually is.

Elements of straight and level flying:

  • Constant heading (flying in a straight line)
  • Constant attitude
  • Constant speed
  • Constant height
  • Balance (wings level)

Next we went over the different cruise types of the plane. There are three main types of cruise – normal cruise, fast cruise and slow cruise. Each one requires different power levels and a different nose attitude.

There’s a formula for this: Power (rpm) + Attitude = Performance

We used J’s perception of attitude since I hadn’t tried it yet, but kept in mind that mine would be rather different since I’m about a foot shorter. Basically, attitude is the perception of where the nose is in relation to the horizon. For example, at normal cruise speed, the horizon for J is about 1/2 way up the windscreen.

Power is measured by the revs of the engine. The revs change at different cruise speeds. J asked me ‘When moving to a slow cruise, do the revs go up or down?’. Bemused I replied ‘down’. He was like ‘You’d be surprised how many people get that wrong’. I was like ‘You’re kidding’. I mean, really, to go slower the engine goes slower and has less revs. That’s obvious. Who, exactly, are these people who get confused and what are they thinking at the time?

Power for different cruise speeds:

  • Normal – 3000rpm
  • Fast – 3200rpm
  • Slow – 2400rpm

However, as with most things it seems, the difference on the Jabiru is mainly comparative, but the differences become more obvious on other planes.

Then we went over the first ‘sequence’ (can’t remember the proper word) to remember and go through when flying – ALAP.

A – Attitude
L – Lookout
A – Attitude
P – Performance

Basically, when flying (especially when starting new maneuvres like turns) you should go through this sequence. First, Attitude (where the nose is in relation to the horizon), then Lookout (look left, centre, then right looking for other planes, mountains, various other things to crash into), Attitude again, and Performance (airspeed, power (rpms) and balance).

Then it was time to head out to the plane. This time, we started going through the checklists for flight. First was the pre-start up checklist. This involved moving different switches for fuel pumps etc. J said that before starting the prop, the pilot has to yell ‘clear prop’ to warn others that the prop is about to start. He tells me this, then turns to the door and says (barely louder than normal conversational level) ‘Clear prop!’. I was like ‘nice yell :P’. I got to taxi to the runway again, then we went through the pre-takeoff checklist which involves checking the controls and the flaps etc. Then, takeoff.

We got to a cruising altitude of about 2000ft then I was given a few minutes to get used to the controls again. I’m definitely getting more confident with them which is nice!

First we tried straight and level flight at normal cruise. When doing this, you have to keep the wings level (balance), a constant airspeed and constant attitude. I discovered that, for me, the horizon is about 1/3 of the way up the windscreen when at a normal cruise At a normal cruise, the airspeed should be around 100kts (knots). After J’s demonstration, I got to try and it was definitely harder than it looked. There’s a lot of things to remember at the same time and it took a fair bit of concentration. I was definitely getting the hang of it though.

Then J demonstrated the transition from normal cruise to slow cruise. This introduced another sequence to remember – PAST.

P – Power
A – Attitude
S – Speed
T – Trim

First, the pilot needs to change the power of the plane (in this case, lessening the power from 3000rpm to 2400rpm. This is done by pulling the throttle out). Next is checking (and changing) attitude. When moving to a slow cruise, the nose needs to raise as the airspeed is less and therefore the wings are creating less lift. To compensate for this, the nose attitude needs to be changed which changes the angle at which the wings meet the air (also known as the Angle of Attack). Then the airspeed needs to be checked – at slow cruise, it should be around 75-80kts. Finally, the pilot needs to trim the elevator as they will be pulling it back quite far to raise the nose to the required level.

At slow cruise, for me, the nose is just above the level of the horizon. First I had to take it from a normal cruise to a slow cruise following PAST. It wasn’t too difficult, I’m getting better at controlling the throttle. Then I had to try flying straight and level at a slow cruise. It’s important to remember, that at a slow cruise, the angle of bank (roll of the plane) has to be less. It was definitely more challenging to keep it straight and level at a slow cruise, it has a tendency to roll and move a little more than at a normal cruise.

Then we took it up to a fast cruise, following PAST again. At a fast cruise, the horizon is about halfway up the windscreen. When moving into a fast cruise, the pilot has to push the elevator forward to lower the nose, and this needs to be adjusted with the trim lever. At a fast cruise, the airspeed should be around 110kts. It is far more challenging to keep it straight and level at a fast cruise as, at faster speeds, there is more turbulence and the plane bounces far more. I also found it harder to keep a constant altitude, it seemed to me that we were flying level, but according to the altimeter we were actually climbing a bit.

We then had to head back to the airport. I got to fly most of the way back, but had to give up the controls for the landing. I can’t wait until I get to do the take offs and landings, although I’ll probably be terrified when it actually comes!

Unfortunately it’s another two weeks before my next lesson, since I have an internship during the week and J was booked up next weekend. I’m pretty disappointed because I had an absolute blast today!

Next lesson, depending on weather is either Turning (if it’s cloudy) or Climbing and Descending (if it’s a nice day).

Random things I learnt today:

  • I’m actually managing to get the hang of the throttle
  • It’s a lot easier to fly with a cushion (sigh)
  • The yell of Clear Prop doesn’t actually have to be a yell
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