Climbing and Descending — Theory Part 1: Climbing

Climbing and Descending — Theory Part 1:

Climbing

CASA Recreational Pilot License (Aeroplane) — Lesson 3, Pre-flight theory

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Climbing and Descending — Theory Part 1: Climbing

Recap — the four forces

Just back again to the analogy of our hand out the car (or aeroplane) window:

  • What are the four forces acting on the "aeroplane"?

The four forces — lift, weight, thrust and drag

  • Thinking about the lift force in particular, can you name some factors that affect the strength of the lift force?
Climbing and Descending — Theory Part 1: Climbing

Recap — the cause of lift

What is the simplest way to describe the cause of the lift force?

Just like your hand, the wing deflects a mass of air downwards resulting in an equal and opposite force upwards.

A diagram showing a wing deflecting a mass of air downwards to generate lift

You can see more detail about this in the 3-minute Veritasium episode How does a wing actually work?

Climbing and Descending — Theory Part 1: Climbing

Recap — climbing in a car

Back when we discussed the effects of controls, we thought about the effect of going up a hill in a car, to see the similarity to climbing in an aeroplane:

Climbing and Descending — Theory Part 1: Climbing

Theory Overview — Part 1

Climbing and Descending — Theory Part 1: Climbing

Learning Objectives — Climbing

By the end of this session, our aim is to be able to:

  • Describe how we manipulate the four forces to produce a climb
  • Apply the performance formula at both the climb entry and climb exit — Power + Attitude = Performance — to climbing
  • Name three types of climbs and when to use each

Later in our flight we'll get to experience and practise each climb.

Climbing and Descending — Theory Part 1: Climbing

The Four Forces in the Climb

Climbing and Descending — Theory Part 1: Climbing

Aerodynamic forces — straight and level recap

In straight and level flight the forces are in balance:

  • Lift = Weight — altitude is maintained
  • Thrust = Drag — airspeed is constant

In level flight we can use excess power available to generate extra speed.

We adjust Power and Attitude, and then Trim

Climbing and Descending — Theory Part 1: Climbing

Aerodynamic forces — Climbing

In a climb, we can use the excess thrust available to generate lift

  • We increase the power and adjust the attitude to maintain our climbing speed
  • The excess thrust is now generating extra lift instead of extra speed.
  • A component of weight now holds the aeroplane back, in addition to the drag force.

More excess thrust → steeper or faster climb. Less excess thrust → shallower climb.

Climbing and Descending — Theory Part 1: Climbing

The performance formula in a climb

The performance formula still applies:

Power + Attitude = Performance

For a climb:

  • Set high power (full throttle or nominated climb power)
  • Set a nose-up attitude (nose above the horizon)
  • Performance — the aeroplane climbs at the expected airspeed

The pilot selects the power and attitude; the airspeed follows. Never chase the airspeed with the controls — set the attitude and wait for the speed to stabilise.

Climbing and Descending — Theory Part 1: Climbing

Climb Entry and Exit

Climbing and Descending — Theory Part 1: Climbing

Climb entry — Power, Attitude then Trim

Climb entry — PAT:

  1. Power — apply climb power (full throttle, or nominated RPM)
  2. Attitude — pitch to climb attitude (nose above horizon)
  3. Trim — trim off the back-pressure; hands off
Climbing and Descending — Theory Part 1: Climbing

Climb work-cycle — ALAP

Maintaining the climb — ALAP work cycle:

  • Attitude — is the nose position correct relative to horizon?
  • Lookout — traffic scan
  • Attitude — confirm the nose still on attitude
  • Performance — quick glance inside: RPM, airspeed as expected?
Climbing and Descending — Theory Part 1: Climbing

Levelling out from climb — Attitude, Power then Trim

Anticipate leveling out around 50-100 ft before your target altitude (or 10% of your climb rate):

  1. Attitude — lower nose to level-flight attitude
  2. Hold climb power while airspeed accelerates to cruise speed, then Power — reduce to cruise power
  3. Trim — trim for hands-off

Lower the nose first, then wait for speed to build — only reduce power once cruise speed is reached. Reducing power too early leaves you slow and flat.

Climbing and Descending — Theory Part 1: Climbing

Types of Climb

Climbing and Descending — Theory Part 1: Climbing

Three types of climb

The handbook for your training aeroplane will give you the values for best angle () and best rate (), and possibly a best cruise speed. As an example, the Piper Warrior 151 gives us values online resources suggest a cruise climb speed:

Climb type Speed Best used for
Best angle (VX) 63 KIAS Most altitude gain per distance; clearing obstacles
Best rate (VY) 75 KIAS Fastest altitude gain per minute; crossing terrain
En-route/Cruise climb 87 KIAS Normal transit; good forward visibility; comfortable
  • VY — steeper nose than cruise climb; reduced forward visibility; for gaining height quickly
  • VX — steepest attitude, slowest airspeed; only used close to the ground (to get away from the ground)
  • All three climbs in the Warrior 151 use full power
Climbing and Descending — Theory Part 1: Climbing

Best angle vs best rate — excess thrust vs excess power

Climbing and Descending — Theory Part 1: Climbing

Factors affecting climb performance

What factors might affect our climb performance?

  • Engine power — more power = better climb rate; engine power reduces with altitude
  • Airspeed — only VY gives maximum rate of climb; too fast or too slow reduces climb rate
  • Weight — heavier aeroplane = more mass means greater thrust required for same climb = reduced climb rate
  • Wind — headwind improves best-angle performance (more altitude per ground distance); no effect on best rate
  • Density altitude — hot, high, humid conditions reduce both engine and aerodynamic performance

Monitor engine temperatures during a prolonged climb — the engine is working harder than in cruise.

Climbing and Descending — Theory Part 1: Climbing

Recap

Climbing and Descending — Theory Part 1: Climbing

Part 1 Recap — Climbing

Can you answer each of these?

  • Which of the four forces change and which remain the same when transitioning from level flight to a climb entry?
  • What is the climb entry sequence? (three letters)
  • What is the level-off sequence, and why does the order differ from the entry?
  • Name three types of climbs — what speed and attitude does each use?
  • When would you choose VX over VY?
  • Name two factors that reduce climb performance (e.g. on a hot day or at high altitude)
Climbing and Descending — Theory Part 1: Climbing

Arrival

Building directly on straight and level flight from Lesson 2. The student knows the performance formula; this session applies it to gaining altitude. Key theme: set the attitude and power, let the performance follow — same as always.

Part 1 covers the climbing side. Part 2 will cover descents and instrument indications.

Return to these at the recap. Ask the student to answer each from memory before revealing.

Click Direct-To to advance to The Four Forces in the Climb.

Demonstrate: - 60% with 4 degrees, - 70% with 2.5 degrees, - 90% with 1.5 degree Note the speed for each.

Keep this simple. The key insight: climbing requires excess thrust. Try: - 100% with 8 degrees - around 500 ft/min Best rate of climb: - 100% with 12 degrees is 650 ft/min @ 90 knots = 650 / (90 * 6000 / 60) = 7.2% climb Best angle of climb example: - 100% with 15 degrees is 600 ft/min @ 78 knots = 600 / (78 * 100) = 7.7% climb That's why we use full power for VX and VY.

Reinforce: the most common student error is trying to correct an incorrect attitude by chasing the airspeed. Set the attitude, let the speed stabilise, then make small adjustments. Examples: - 100% with 8 degrees - around 500 ft/min @ 100kts Best rate of climb: - 100% with 12 degrees is 650 ft/min @ 90 knots = 650 / (90 * 6000 / 60) = 7.2% climb Best angle of climb example: - 100% with 15 degrees is 600 ft/min @ 78 knots = 600 / (78 * 100) = 7.7% climb

Click Direct-To to advance to Climb Entry and Exit.

Set: - Throttle to 40% Ask, at what point in a car, would you add power? - Right before the bottom of the hill. Right before our attitude changes due to the hill. **Power**, Attitude, Trim.

PAT gets you into the climb; ALAP keeps you there. Three of the four steps keep eyes outside — that's the point. Only Performance requires a glance at the instruments. Repeat the cycle continuously throughout the climb.

APT for level-off. The sequence differs from climb entry (PAT) because we need the speed to build before reducing power — lowering the nose alone won't accelerate the aeroplane quickly enough if power is pulled at the same time.

Click Direct-To to advance to Types of Climb.

Use the model aeroplane or a whiteboard diagram to show the nose attitude difference between all three.

Demo script — left chart first, then right: - Before touching anything, ask: why do best angle and best rate happen at two *different* speeds? - Left chart: drag the cursor to where the green gap between thrust available and thrust required is widest — it snaps at VX. Excess *thrust* is what pulls us up most steeply per metre travelled: best **angle**. - Right chart: drag to where the gap between power available and power required is widest — it snaps at VY. Excess *power* is height gained per minute: best **rate**. - Have the student predict before revealing: is VX slower or faster than VY? (Slower — the thrust surplus peaks earlier than the power surplus, and the charts show why.) - Drag slower than VX and watch the excess shrink again — we'll return to this region ("behind the curve") in the stalling lesson. The model is generic but calibrated (vs=43, cruise-kts=148) so VX and VY land on the Warrior's 63 and 75 KIAS from the previous slide.

Introduce density altitude gently. The key takeaway: on a hot summer day, the aeroplane will not climb as well as the book figures suggest. The POH performance charts assume standard conditions.

Click Direct-To to advance to the recap.

Ask one at a time; let the student answer before revealing. End positively — this content is the foundation for the descent session that follows.