British Young Pilots ยท Wings ยท Week 2INSTRUCTOR
๐ Welcome
Last week you learned what an aeroplane is made of and the four forces that push and pull on it. Today you find out what the controls really do, how a pilot reads the three most important dials, and then you land an aeroplane on the simulator.
Has everyone booked their flight yet?
๐ฏ Today you will
๐ Recap
Tap a question to reveal the answer.
The aeroplane's body, to which the wings, tail, wheels and engine attach
Source: Pooleys Vol 1 (15th ed.) p.1 (module FT-1.1).
Lift, Weight, Thrust, Drag
Source: Pooleys Vol 4 (10th ed.) p.4 (module POF-1.1).
The downward force attracting all bodies vertically towards the centre of the Earth
Source: Pooleys Vol 4 (10th ed.) p.7 (module POF-1.2).
Provides a balancing, stabilising force, like the feathers on an arrow or dart
Source: Pooleys Vol 1 (15th ed.) p.1 (module FT-1.1).
The amount of matter a body contains
Source: Pooleys Vol 4 (10th ed.) p.3 (module POF-1.1).
Mass ร gravitational force
Source: Pooleys Vol 4 (10th ed.) p.7 (module POF-1.2).
The fin
Source: Pooleys Vol 1 (15th ed.) p.1 (module FT-1.1).
The total weight of the loaded aeroplane: machine, people, fuel, bags
Source: Pooleys Vol 4 (10th ed.) p.7 (module POF-1.2).
๐น๏ธ Part one
You know the names: elevator, ailerons, rudder. Now the real question. When the pilot moves each one, what does the aeroplane actually do?
Part 1 of 10 ยท Module FT-4.1 ยท Flying Training
Full module (its own cards, game and quiz): FT-4.1 Primary Effects of the Main Flight Controls
Stand up and be the aeroplane, arms out as wings. Nod your head: that is pitch, nose up and down. Tip one arm down and the other up: that is roll. Twist to look over your shoulder: that is yaw, nose swinging left or right. Every move an aeroplane makes is one of these three, or a mix, each turning about an imaginary line through its middle.
Source: Pooleys Vol 1 (15th ed.) p.30 and p.34.
An aeroplane rotates about three imaginary lines through its centre of gravity (CG). Pitching (nose up and down) is motion about the lateral axis, wingtip to wingtip. Rolling is motion about the longitudinal axis, nose to tail. Yawing (nose left and right) is motion about the normal axis. The pilot commands each one with a main flight control: the elevator controls pitch, the ailerons control roll, the rudder controls yaw.
Stability is the aeroplane's own tendency to hold its attitude, or return to it after a gust, with no help from you. Most trainers are reasonably stable in pitch: trimmed, they fly hands-off with the nose steady against the horizon. Roll and yaw stability are weaker: a dropped wing can become a descending spiral turn unless you level the wings.
Source: Pooleys Vol 1 (15th ed.) p.30 and p.34.
The elevator is the flap on the back of the tailplane. Pull the stick back and the elevator tips up: air pushes the tail down, so the nose comes up. Push the stick forward and the opposite happens: nose down. Pilots use it to park the nose where they want it against the horizon.
Try it: bend the back edge of your paper aeroplane's tail up a little and throw it. It noses up and climbs. Bend it down and it dives. You have built an elevator.
Source: Pooleys Vol 1 (15th ed.) p.31 and p.36โ37.
The elevator is worked by fore and aft movement of the control column. Conventionally it is hinged to the rear of the tailplane; some types use an all-flying tail, a stabilator, one moving surface doing both jobs, with the same effect. Column back: elevator up, a downward force on the tail, rotation about the CG, nose up. Column forward: nose down. Bigger deflection, faster pitch. At normal speeds the inputs are small and feel like pressure rather than movement.
Use the column to put the nose where you want it against the horizon (to set the pitch attitude), then centralise. Airwork: from level, column gently forward, nose pitches down, centralise, airspeed increases. Column gently back, nose pitches up, centralise, airspeed decreases.
Source: Pooleys Vol 1 (15th ed.) p.31โ32 and p.36โ37.
The ailerons are the flaps on the outer back edge of each wing, and they always move opposite ways. Stick left: the left aileron goes up and the right one goes down. The right wing gets more lift and rises, the left wing gets less and drops, and the aeroplane rolls left. Let the stick go back to the middle and the rolling stops, leaning where it is.
Try it: bend one wing's back edge up and the other wing's down on your paper aeroplane. Throw it and watch it corkscrew.
Source: Pooleys Vol 1 (15th ed.) p.32.
The ailerons are hinged to the outboard trailing edge of each wing and are worked by rotating the control wheel or moving the column left and right. So the column does two jobs: fore and aft for the elevator, sideways for the ailerons. Column, wheel and side-stick all perform the same function.
One aileron goes down and adds lift to its wing; the other goes up and reduces lift on its wing; the aeroplane rolls. Column left: left aileron up, right aileron down, roll left. The roll continues for as long as the ailerons are deflected, at a rate set by how far they are deflected. Centralise and the ailerons go neutral, the rolling stops and the bank angle reached is held. Airwork: wings level, rotate left, it rolls left; centralise, steady bank; rotate right to level, centralise as the wings come level; repeat with different amounts.
Source: Pooleys Vol 1 (15th ed.) p.32 and p.36โ37.
The rudder is the flap on the back of the fin, and your feet work it. Push the left pedal and the rudder swings left, the air shoves the tail right, and the nose swings left, like a boat's rudder swinging the bow round. Right pedal, nose right. It is not how pilots turn (that feels like turning a bike without leaning). Its everyday job is keeping the little balance ball in the middle of its tube: ball slides right, press right pedal.
Source: Pooleys Vol 1 (15th ed.) p.33 and p.38.
The rudder is hinged to the rear of the fin and worked with both feet on the interconnected pedals (one forward, the other back). Left pedal forward deflects the rudder left, the fin is pushed right, and the aeroplane rotates about its CG: nose yaws left. Right pedal, nose right. Yawing alone is uncomfortable and inefficient (it adds drag), like turning a bicycle without leaning.
The rudder's main everyday job is to prevent unwanted yaw: keeping flight balanced. Out of balance, the balance ball slides to one side and you feel pushed the same way; apply same-side rudder pressure to centre it. Airwork: pick a reference point on the horizon, apply left rudder pressure, the nose yaws left and the ball is thrown right; centralise; repeat right. Whatever the attitude, banked or nose-high, every control still works in the same sense relative to the aeroplane.
STRETCHThreat and Error Management (TEM) for this exercise: the threat is other aircraft, so look out most of the time. The errors are two people on dual controls (fixed by "You have control" / "I have control") and clumsy inputs (fixed by following through, holding the controls lightly and using pressure, not big movements).
Source: Pooleys Vol 1 (15th ed.) p.33โ35, p.38 and p.39.
Why the tail moves. Elevator up speeds the airflow beneath the tailplane and lowers the static pressure there, so the net aerodynamic force on the tail acts downward and the aeroplane pitches nose-up about its CG. Rudder left speeds the flow on the right side of the fin, lowering the pressure there, so the fin is pushed right and the nose yaws left. Same mechanism, different axis; a stabilator produces the same result as a hinged elevator.
Primary versus further effect. A single control can have more than one effect. Bank tilts the lift vector, giving it a sideways component; the aeroplane sideslips towards the lower wing, the airflow strikes the keel surfaces behind the CG (fin and fuselage) and the nose yaws towards the slip. The nose drops and a spiral descent begins unless the wings are levelled. Primary effect of ailerons: roll. Further effect: yaw. Module FT-4.2 takes this on.
Source: Pooleys Vol 1 (15th ed.) p.31, p.33, p.37 and p.40.
๐ Activity
Fold a paper aeroplane. Bend the back edge of the wings up a little and throw it. Now bend one wing's edge up and the other down. Then bend the tail sideways. Which control were you copying each time, and what did the aeroplane do?
Try all three. Which one was the elevator, which the ailerons, which the rudder?
Part 2 of 10 ยท Module POF-7.1 ยท Principles of Flight
Full module (its own cards, game and quiz): POF-7.1 Three Axes, Three Controls
Sit up straight and try this. Nod your head: that is pitch. Tip your head towards one shoulder: that is roll. Shake your head "no": that is yaw.
Those are the only three ways an aeroplane can turn. Each one happens about an imaginary line through the aeroplane's balance point, its CG, so there are three axes. Now hold your hand out flat like an aeroplane and do all three: nose up and down, one wing down, nose left and right.
Source: Pooleys Vol 4 (10th ed.) p.87.
Every aeroplane has control systems so the pilot can manoeuvre it, and trim it, about each of its three axes. The turning forces that do this are called moments. They are produced by changing the airflow around the aerofoils: altering an aerofoil's shape, or moving its position. The three motions are pitch (nose up and down), roll (one wing down, the other up) and yaw (nose left and right).
The circle-and-dot at the CG is the third axis, pointing straight up out of the page. Source: Pooleys Vol 4 (10th ed.) p.87.
Each motion has its own control in the cockpit, and each control moves its own hinged surface on the aeroplane:
Hold an invisible stick and put your feet on invisible pedals. Nose up: stick back. Wing down: stick over. Nose left: left foot forward.
Source: Pooleys Vol 4 (10th ed.) p.87.
There are usually three sets of primary controls and three sets of control surfaces, all linked to the cockpit:
Note the wording: "longitudinal control" here means control in the pitching sense, and "lateral control" means roll. Say pitch, roll and yaw and you cannot go wrong.
STRETCHIdeally each control would make a moment about one axis only. In practice it is rarely that tidy: deflecting the ailerons to start a roll also produces adverse yaw. Which pedal do you think fixes it?
Source: Pooleys Vol 4 (10th ed.) p.87.
Why are the elevator and rudder right at the back, and the ailerons out near the wingtips? Try a door. Push it right next to the hinges and it hardly moves. Push at the handle, far from the hinges, and it swings with one finger.
The aeroplane turns about its balance point, the CG, so the control surfaces are put as far from it as possible. A long lever means a small surface can give a big turning push. The controls are the aeroplane's door handles.
Source: Pooleys Vol 4 (10th ed.) p.87.
The surfaces the pilot moves are usually hinged and sit near the extremities of the aerofoils, far from the centre of gravity. That gives them a long moment arm and the greatest leverage. Deflecting one changes the airflow and pressure distribution over the whole aerofoil, not just the moving part: the lift of the combined aerofoil and control surface changes, and that produces the moment. How effective the controls are is the aeroplane's controllability.
Stability opposes controllability. Too much built-in stability makes an aeroplane resist change and hard to manoeuvre, so the designer picks a balance for the job: an airliner wants more stability, a fighter wants more controllability. In that sense the controls are destabilisers. Stops limit control travel, and control locks (a pin through the column, or blocks around the surface) protect parked aeroplanes from the wind. They carry flags because they must come out on the walk-round, before flight.
Source: Pooleys Vol 4 (10th ed.) p.87โ88.
The elevator as the worked example. Column forward moves the elevator down. That changes the shape of the whole tailplane-and-elevator section, so the tail now produces a reduced downward force, or even an upward one if the deflection is large enough. The tail force acts a long way behind the CG, so the change creates a pitching moment about the CG that lowers the nose. Column back does the reverse: elevator up, a larger downward force at the tail, nose up.
Every primary control works the same way in principle: a hinged surface reshapes its parent aerofoil, the force on that aerofoil changes, and the long arm to the CG turns that force change into a moment.
Source: Pooleys Vol 4 (10th ed.) p.87โ88. The elevator, stabilator and anti-balance tab get their own treatment in POF-7.2.
Part 3 of 10 ยท Module POF-7.3 ยท Principles of Flight
Full module (its own cards, game and quiz): POF-7.3 Ailerons and Adverse Yaw
The ailerons are little flaps at the back of each wing, right out near the tips. They always move in opposite directions. Push the stick left and the left aileron goes up while the right one goes down. Hold your arm flat out of a car window and tilt your hand so the front edge points up: the air shoves your hand upwards. A down-going aileron does that to its wing, so that wing rises, the other wing drops, and the aeroplane rolls.
Source: Pooleys Vol 4 (10th ed.) p.91โ92.
The ailerons are the primary control in roll. They sit on the outboard trailing edge of each wing and always move in opposite directions: one goes up and reduces the lift of its wing, the other goes down and increases the lift of its wing. The pilot moves them with sideways control column or by rotating the control wheel.
The unequal lift creates a rolling moment. Its size depends on the lift difference and on the moment arm to the CG, which is why the ailerons are placed outboard. The rule: the down-going aileron is on the up-going wing, and the up-going aileron is on the down-going wing.
Source: Pooleys Vol 4 (10th ed.) p.91โ92.
Back to the car window. When your tilted hand gets shoved up, it also gets shoved back. More lift always brings more drag. So the wing with the down-going aileron rises, but it is also held back, like rowing harder with one oar. Pull harder on the left oar and the boat swings right. The rising wing is the hard-working oar: the nose swings towards it, which is away from the turn you wanted. Pilots call this adverse yaw. Roll left, nose sneaks right.
Source: Pooleys Vol 4 (10th ed.) p.92.
A down-going aileron effectively increases its wing's camber and angle of attack, so that wing makes more lift and more drag. The up-going aileron does the reverse: less lift and less drag. The lift difference rolls the aeroplane, but the drag difference (differential aileron drag) holds the rising wing back and yaws the nose away from the direction of roll. This is adverse aileron yaw, also called aileron drag. It is hard to spot unless you look for it, and it is mainly a low airspeed problem, most obvious in a slow turn.
Source: Pooleys Vol 4 (10th ed.) p.92.
Two helpers stop the nose sneaking the wrong way. First, the designers: on most modern trainers the up-going aileron moves through a bigger angle than the down-going one, adding a bit of drag to the dropping wing so the two wings pull back about the same. Second, you: press the rudder pedal on the same side as the roll. Stick left, foot left. Try it now: arms out, roll left by dropping your left arm, and turn your nose left at the same time. That is a tidy turn: ailerons and rudder together.
Source: Pooleys Vol 4 (10th ed.) p.92โ93.
Good design has largely removed aileron drag from modern trainers, using one or more of three ideas:
Whatever remains, the pilot removes with rudder. Rudder's primary effect is yaw, its secondary effect roll; the ailerons' primary effect is roll, their secondary effect yaw. Using rudder to cancel adverse yaw while the aeroplane is rolling is one of the most important elements of aeroplane control.
Source: Pooleys Vol 4 (10th ed.) p.92โ93.
Once banked, the lift is tilted and its sideways component has nothing to balance it, so the aeroplane slips towards the lower wing. That sideways airflow hits the fuselage and the big keel surfaces such as the fin, mostly behind the CG, and the nose yaws progressively towards the bank. With the ailerons back to neutral the yaw continues, and the aeroplane will drift into a spiral descent and lose height unless the pilot levels the wings or applies back pressure.
STRETCHTwo yaws point opposite ways during a turn entry: adverse yaw (away from the roll, while the ailerons are deflected) and the secondary-effect yaw (towards the bank, once banked). Which one is the rudder mainly fighting on the way in?
Source: Pooleys Vol 4 (10th ed.) p.94.
Where the adverse drag comes from. The rising wing's extra drag is the cost of its extra lift: Pooleys' figure labels it high induced drag. The design fixes do not remove it. Differential and Frise ailerons instead add parasite drag to the descending wing (a bigger upward deflection, or an aileron nose protruding into the airflow beneath the wing) so the two wings' drags more nearly balance and the yawing moment shrinks.
Coupled controls. Linking the rudder to the ailerons puts an aerodynamic sideforce on the fin as the ailerons deflect, producing a yawing moment into the bank that opposes the adverse yaw directly.
Source: Pooleys Vol 4 (10th ed.) p.92โ94.
โ๏ธ Part two
A pilot does not steer an aeroplane like a car. They set a picture out of the window (the attitude) and a power setting, and the aeroplane gives them a result (the performance). Watch the model aeroplane.
Part 4 of 10 ยท Module FT-6.1 ยท Flying Training
Full module (its own cards, game and quiz): FT-6.1 Straight and Level at Constant Power
Think of riding a bike along a flat, straight road. You keep the handlebars steady and you do not go up or down any hills. An aeroplane flying straight and level does the same two things at once. Straight means it keeps pointing the same way: wings level, nose not swinging left or right. Level means it stays at the same height.
Try it: arms out as wings, hold them level, and walk a straight line across the room. That is the pilot's job in the cruise, and doing it neatly is one sign of a good pilot.
Source: Pooleys Vol 1 (15th ed.) p.77.
Attitude is simply how the aeroplane is positioned against the horizon: nose up, nose down or level, and wings level or tipped into a bank. Hold a model aeroplane out at arm's length and look at it against the top edge of the classroom wall (that is your horizon). Tip the nose up: a nose-high attitude. Tip it down: nose-low. Dip one wing: a bank.
In a real cockpit the pilot watches where the horizon sits against the nose of the aeroplane, and learns exactly where it should be for cruising.
Source: Pooleys Vol 1 (15th ed.) p.82 and p.84โ85.
Performance is what you get: how fast you are going, and whether you are climbing, level or descending. Two things decide it together: the power (how hard the engine is working) and the attitude (where the nose is pointing). Think of a bicycle on a hill: you need the right angle and enough pedalling.
Pilots say it as a rule: POWER plus ATTITUDE equals PERFORMANCE. Leave the power alone and the nose decides: too high and the aeroplane climbs, too low and it descends, and the one right attitude in between keeps it level. Need a big change of height? Then the power has to change too.
Source: Pooleys Vol 1 (15th ed.) p.83, p.86 and p.88.
Pilots keep their eyes outside most of the time: looking for other aircraft, and checking that the horizon is level and sitting in the right place against the nose. Then a quick peek inside, one or two seconds only. The altimeter says whether the height is holding, and the VSI (vertical speed indicator) says whether you are drifting up or down.
There is also the balance ball: keep it in the middle with your feet on the rudder pedals. The work cycle is Lookout, Attitude, Instruments, over and over. Small, early corrections beat big, late ones.
Source: Pooleys Vol 1 (15th ed.) p.83โ84, p.87 and p.90.
Straight is a constant heading: wings level with aileron, yaw prevented with rudder. Level is a constant altitude: the correct power set and the nose held in the correct attitude, altitude read on the altimeter. In balance is the balance ball kept centred with rudder pressure.
In steady straight and level flight the four forces are in equilibrium: lift opposes weight, thrust opposes drag. They rarely cancel exactly, so the tailplane and elevator add a small balancing force, usually downward, which the pilot adjusts continually with the control column. Reduce the power and the nose tends to drop unless back pressure is held.
STRETCHWhy does the nose drop when power comes off? Two reasons hide in the design: the thrust and drag couple no longer counters the lift and weight couple, and less propwash over the tailplane means less tail-down force (a smaller effect on a T-tail).
Source: Pooleys Vol 1 (15th ed.) p.77โ78.
Angle of attack is the angle at which the relative airflow meets the wing. Pitch attitude is the nose position against the horizon. They are not the same thing. The elevator controls angle of attack: ease back and the nose rises, the wing meets the air at a greater angle, lift increases and the aeroplane starts to climb. Ease forward and the reverse happens. Slow flight needs a high angle of attack, fast flight a low one.
You cannot read angle of attack in the cockpit, so you set a suitable power and a suitable attitude instead. Power plus attitude determines performance: airspeed and rate of climb. At constant power one attitude gives level flight; nose too high and you climb, too low and you descend. Proof of the right attitude: the altimeter holds, with the VSI as backup.
Source: Pooleys Vol 1 (15th ed.) p.81โ83.
Keep the wings level with aileron: the visual clue is the natural horizon lying level across the windscreen. Prevent yaw with rudder and keep the balance ball centred: ball out to the left, more left rudder; out to the right, more right rudder. Rudder trim, if fitted, removes the foot pressure.
Pick a reference point on the horizon ahead. In straight flight it stays in the same place relative to the nose, and inside the HI (heading indicator) and compass read steady. If you wander, first stop the drift (wings level, no yaw), then bank gently, about 5 degrees, back towards the point and neutralise the controls.
Do not fly with crossed controls: one wing down held straight with opposite rudder is a sideslip, adding drag and costing airspeed or fuel. A sloping cloud base is the classic trap. Ball to the centre with rudder, then straight with aileron.
Source: Pooleys Vol 1 (15th ed.) p.83โ84, p.86 and p.89.
Level flight is the correct nose attitude for the power set: the horizon sits at a particular position against the nose cowl or coaming. Use the same seating position every flight so that picture stays reliable. With cruise power set, place the nose in the cruise attitude, let the airspeed settle on the ASI, cross-check altimeter and VSI, then trim off the elevator pressure while holding the attitude.
Climbing? Lower the nose slightly, regain the altitude, reselect the level attitude, retrim. Descending? Raise the nose, regain, reselect, retrim. Small early corrections beat occasional large ones; if the error grows beyond about 100 ft, consider using power.
Eyes outside most of the time: look out for traffic, check the attitude, then a one or two second glance at the instruments. Work cycle: Lookout, Attitude, Instruments (LAI).
Source: Pooleys Vol 1 (15th ed.) p.84โ90.
Stability is the aeroplane's built-in tendency to return to its original attitude after a disturbance with no pilot input. In pitch it comes from the tailplane: a gust that raises the nose presents the tailplane to the airflow at a greater angle of attack, it makes more upward (or less downward) force, and the nose comes back down, exactly like the flights on a dart. In yaw the fin does the same job. In roll, a dropped wing tilts the lift and the aeroplane slips towards the low wing; high keel surfaces (fin, fuselage side) and dihedral turn that sideways airflow into a restoring roll.
Stability is weaker in roll and yaw than in pitch, and an uncorrected disturbance in either eventually becomes a spiral descent. The CG position sets pitch stability: a forward CG gives more stability but heavier elevator forces and, at landing speed, perhaps not enough elevator to flare; an aft CG gives less stability, constant attention to pitch, and at low speed a tail-heavy moment that can stall the aeroplane, possibly unrecoverably. The CG must stay within the Flight Manual's approved range: the pilot's responsibility.
Source: Pooleys Vol 1 (15th ed.) p.78โ81.
๐๏ธ Part three
How does the pilot know the speed, the height, and whether they are going up or down? Three dials. First, how the aeroplane feels the air at all.
Part 5 of 10 ยท Module AGK-24.1 ยท Aircraft General Knowledge
Full module (its own cards, game and quiz): AGK-24.1 Pressures and the Pitot-Static System
Hold your hand out flat and keep it perfectly still. Feel anything? No, but the air is pushing on it from every side right now. That push is called static pressure. It comes from the weight of all the air stacked up above you, pressing down. Fly up high and there is less air on top of you, so the push gets weaker.
An aeroplane feels this push through a small flush hole in its side called the static vent. Nothing blows through it; it just senses the push outside.
Source: Pooleys Vol 4 (10th ed.) p.323.
Now imagine your hand out of the window of a moving car, palm facing forward. Whoosh: an extra push. That extra push only exists while you are moving through the air. It is called dynamic pressure. Faster car, bigger push. Thin air high up, smaller push.
Try it: blow on your palm gently, then hard. Feel the difference?
The aeroplane catches this push with a small tube at the front pointing straight into the wind: the pitot tube. The wind rams into it, so the tube feels the ordinary push and the extra moving push added together.
Source: Pooleys Vol 4 (10th ed.) p.324โ325.
Pipes carry the air from the two holes to three round dials. The airspeed indicator (ASI) needs both pipes: it compares them, and the difference is how fast you are flying. The altimeter needs only the static pipe: weaker push means you are higher. The vertical speed indicator (VSI) needs only the static pipe too: it watches how quickly that push is changing, up or down.
Source: Pooleys Vol 4 (10th ed.) p.326โ327.
Both holes are tiny, so tiny things can block them: a bug, a drop of water, a bit of ice. A blocked hole means a dial telling lies, so on the walk-round before every flight the pilot checks the pitot tube and static vent are clean and undamaged.
Three rules: take the pitot cover off before flight (it keeps water and insects out on the ground), never blow into the tube (the instruments on the end are very delicate), and remember there is a little electric heater in the pitot tube, switched on from the cockpit, to melt ice.
Source: Pooleys Vol 4 (10th ed.) p.326.
Flight instruments fall into three families: pressure instruments (variations in air pressure), gyroscopic instruments (gyroscopic inertia) and magnetic instruments (the Earth's magnetic field). The three basic flight instruments, the ASI, the altimeter and the VSI, are all pressure instruments, and they work with two kinds of air pressure.
Static pressure is the pressure of the atmosphere at a point: the weight of all the air above that point. It acts equally in every direction, needs no movement of the air, and falls as you climb. On the aeroplane it is sensed by a static vent on the airframe surface.
Source: Pooleys Vol 4 (10th ed.) p.323.
Dynamic pressure is the extra pressure a body feels when it moves relative to the air (or the air moves past it), on top of the static pressure that is always present. It depends on two things: speed relative to the air (more molecules strike per second) and the density of the air (denser air, more molecules; in outer space there would be none at any speed).
Total pressure is static plus dynamic. It is also called pitot, ram or impact pressure, and it is measured by a pitot tube facing into the airflow. Subtract the static pressure from it and what is left is the dynamic pressure, which is exactly what the ASI shows, on a scale marked in knots.
STRETCHAt the same airspeed, why does the hand out of the window feel a smaller push at 10,000 ft than at sea level?
Source: Pooleys Vol 4 (10th ed.) p.324โ325.
Two arrangements are common: a combined pitot-static head, or a separate pitot tube (often on the wing) with one or two static vents on the side of the fuselage. The pitot tube must sit where the airflow is not greatly disturbed, often ahead of or beneath the outer wing; a poor position gives significant airspeed errors. Two static vents, one each side, average out the reading when the aeroplane is slipping or skidding.
Source: Pooleys Vol 4 (10th ed.) p.326โ327.
Damage or a blockage in the pitot tube or a static vent gives false readings that can degrade safety, so both are checked carefully on the pre-flight external inspection. The pitot cover (which keeps out water and insects) comes off for the inspection and must be off before flight. Never blow into a pitot tube: very sensitive instruments sit on the end of it.
Pitot heat, an electrical element in the tube switched from the cockpit, guards against ice. Test it briefly on the pre-flight, then switch it off: without cooling airflow the element burns out easily, so it stays off whenever the aeroplane is not flying.
An alternate static source in the cabin covers a blocked external vent. Cabin pressure in flight is usually slightly below outside pressure, so readings on the alternate source are slightly in error.
STRETCHIf the cabin pressure is slightly lower than outside, which way would the altimeter be wrong on the alternate source, and why?
Source: Pooleys Vol 4 (10th ed.) p.326โ327.
Dynamic pressure = ยฝ ฯ Vยฒ, where ฯ (rho) is air density, which falls with altitude, and V is the speed of the body relative to the air. It makes no difference whether the body moves through the air, the air moves past the body, or both: only the relative speed counts. Because the pressure varies with Vยฒ, doubling the speed gives four times the dynamic pressure, one of the square laws common in nature.
Bernoulli's relationship: static pressure (from the static line) plus dynamic pressure (ยฝ ฯ Vยฒ) equals total pressure (from the pitot tube). Inside the ASI, total pressure is fed to one side of a flexible diaphragm while static pressure from the vent surrounds it, so the mechanism responds to total minus static, which is the dynamic pressure, and the scale is calibrated in knots.
Source: Pooleys Vol 4 (10th ed.) p.325. The ASI mechanism in full is module AGK-24.2.
Part 6 of 10 ยท Module AGK-24.2 ยท Aircraft General Knowledge
Full module (its own cards, game and quiz): AGK-24.2 The Airspeed Indicator
Your car has a speedometer. An aeroplane has an ASI, the airspeed indicator, and it does the same job with one twist. A little tube on the wing, the pitot tube, points straight into the oncoming air, so the ASI measures how fast the air is rushing past the aeroplane, not how fast the ground is sliding by underneath.
Think of a swimmer in a river: speed through the water is one thing, progress along the bank is another. Aeroplanes measure the swimming kind. The dial reads in knots, the pilot's unit of speed.
Source: Pooleys Vol 4 (10th ed.) p.328.
The airspeed indicator displays indicated airspeed (IAS), and what actually drives it is dynamic pressure: the pressure of the air ramming into the pitot tube. Dynamic pressure is total (pitot) pressure minus static pressure, and the instrument does that subtraction mechanically. Total pressure is fed to one side of a diaphragm (capsule) and static pressure from the static line to the other side. The diaphragm settles at a position set by the difference, which is dynamic pressure, ยฝฯVยฒ, and a gearing system moves the pointer to match.
Source: Pooleys Vol 4 (10th ed.) p.328.
Hold your hand flat out of a car window (someone else driving, please). Slow: a gentle push. Fast: a hard push. The ASI feels exactly that push.
The pitot tube catches the oncoming air and feeds it to one side of a squashy capsule inside the instrument. The other side feels only still air from a tiny hole called the static vent. The faster you fly, the harder the capsule is squeezed, and a lever and gears swing the needle further round the dial. Speed up, needle up.
FOUNDATIONSClass action: hold a flat hand up and "fly" it; the instructor blows harder and harder, and everyone's needle finger creeps round an imaginary dial.
Source: Pooleys Vol 4 (10th ed.) p.328.
A pressure gauge can only be graduated in speed if you fix the air density. The ASI assumes density stays constant at its mean sea level value (it does not), which lets the scale be marked in units of speed, usually knots. The price is that the reading is exactly right only on an ISA standard day at mean sea level (15 ยฐC, pressure altitude 0 ft). As airspeed rises, dynamic pressure rises while static pressure stays the same, so the diaphragm moves and the pointer reads higher.
Some dials also carry a second scale in miles per hour alongside the knots. Know which units your aeroplane uses before you fly it.
Source: Pooleys Vol 4 (10th ed.) p.328โ329.
Coloured arcs run round the numbers, and they work like traffic lights:
A rhyme to keep them: white is for flaps, green means go, yellow means gently, red means no.
FOUNDATIONSClass action: the instructor calls a situation (cruising on a calm day, landing with flaps down, bumpy air), the class shouts the colour.
Source: Pooleys Vol 4 (10th ed.) p.330.
To assist the pilot, modern ASIs mark speed ranges and specific speeds in a conventional colour code. Reading from slow to fast:
The two stall speeds carry their own codes: VS0 with landing gear down, flaps lowered and power off (the bottom of the white arc); VS1 with landing gear up (if retractable), flaps up and power off (the bottom of the green arc).
STRETCHThe white arc starts at the stall speed at maximum all-up weight. On a day when the aeroplane is much lighter, would the real stalling speed be above or below the start of the arc? Why paint the heaviest case?
Screen colours are theme tokens: on the real instrument the solid inner arc is white, the dashed arc is green, the bright arc is yellow and the radial line is red. The dial speeds are illustrative, not any real aeroplane's. Source: Pooleys Vol 4 (10th ed.) p.329โ330.
Two more things a pilot checks. First, the units: most dials read in knots, but some also carry a second ring of numbers in miles per hour, so you must know which ring you are reading.
Second, the shape. In a modern glass cockpit there is no round dial at all. The airspeed shows as a moving strip, the speed tape, down the left-hand side of the screen, painted with the very same white, green, yellow and red bands. Same rules, new outfit.
Source: Pooleys Vol 4 (10th ed.) p.329 and p.331.
Some ASIs carry blue radial lines for other important speeds, for example the best single-engine speed on a light twin. Every marking on an ASI is an indicated airspeed, never TAS, and wherever weight affects a limit speed (the stall speeds, for instance) the value painted is for the maximum all-up weight (AUW).
On an EFIS the airspeed appears as a moving speed tape, always down the left-hand side of the screen, because the ASI always sits in the top-left corner of the Standard T layout; the glass panel keeps that standardisation with a conventional one. The tape uses the same colour coding as the round dial: coloured bands for the speed ranges and limits.
Source: Pooleys Vol 4 (10th ed.) p.330โ331.
What the needle really measures. Its position is set by ยฝฯVยฒ, the dynamic pressure, so the ASI is a differential pressure gauge. Graduating it in knots needs a fixed density, and the maker uses the ISA mean sea level value (15 ยฐC, pressure altitude 0 ft). Away from those conditions the needle still shows the dynamic pressure the airframe is feeling, expressed as the speed that would produce it at sea level: that is precisely what indicated airspeed means, and why the reading is exact only on an ISA standard day at MSL.
Every limit is an IAS limit. The arcs and radial lines are all indicated speeds, never true airspeeds, and the weight-dependent ones are painted for maximum all-up weight. How IAS relates to true airspeed is a later module.
Source: Pooleys Vol 4 (10th ed.) p.328 and p.330.
Part 7 of 10 ยท Module AGK-24.4 ยท Aircraft General Knowledge
Full module (its own cards, game and quiz): AGK-24.4 The Altimeter
The altimeter is the aeroplane's height dial. It reads in feet, and it works by feeling the air. Air gets thinner the higher you go, so it squeezes less and less on everything around it.
You have seen this trick already: take a sealed crisp packet up a mountain and it puffs up like a balloon. Inside the altimeter is a small sealed metal can that does exactly the same thing. As the aeroplane climbs, the can swells; as it comes back down, the air squeezes it small again. The can is joined to the pointer, so swell and shrink become "up" and "down" on the dial.
Source: Pooleys Vol 4 (10th ed.) p.335.
A pilot needs to know the height of the aeroplane above the ground and above mean sea level (MSL) for three reasons: terrain clearance (not hitting the ground or fixed obstacles), traffic separation (aircraft cruising at different altitudes are kept safely apart vertically) and performance calculations (working out what the aeroplane can do, and flying it safely and efficiently).
The pressure altimeter is simply a barometer, an instrument that measures atmospheric pressure. It relies on one fact: the higher you are in the atmosphere, the lower the static air pressure. Near the surface the pressure falls by roughly 1 hPa for every 30 ft of climb. The most compact and rugged barometer for an aircraft is the aneroid type, the same family as the one on a living-room wall.
Source: Pooleys Vol 4 (10th ed.) p.335.
The instrument case is fed with static pressure from a vent on the outside of the aircraft. Inside sits the aneroid: a sealed metal capsule that can expand and compress, containing a fixed amount of air. As the aeroplane climbs, the pressure around the capsule drops and the capsule expands; a linkage and gearing turn that movement into a pointer sweeping round the scale. As the aeroplane descends the rising pressure compresses the capsule and the pointer winds back to a lower reading.
The scale is graduated in feet, never in pressure units (millibars, hectopascals or inches of mercury), even though pressure is what the capsule actually senses.
Source: Pooleys Vol 4 (10th ed.) p.335โ336.
The dial has numbers 0 to 9 and pointers like a clock. The long pointer counts hundreds of feet: on the 2, that is 200 ft. The short fat pointer counts thousands: just past the 5, that is 5,000 and a bit. Put them together and this dial reads 5,200 ft. A third, very thin pointer counts ten-thousands, so it hardly moves in a small aeroplane.
Tip: read the short pointer first for the thousands, then add the long one.
Source: Pooleys Vol 4 (10th ed.) p.336.
Short fat pointer first (thousands), then the long pointer (hundreds). Shout out each answer before your instructor reveals it.
A: short pointer just short of 2, long pointer on 8: 1,800 ft. B: short pointer just past 0, long pointer on 7: 700 ft.
STRETCHThe thin third pointer sits between 1 and 2, the short one just past 2, the long one on 3. What height is that? (Answer: 12,300 ft.)
Source: Pooleys Vol 4 (10th ed.) p.336.
The conventional altimeter carries three pointers over a 0 to 9 scale: a long 100 ft pointer, a short broad 1,000 ft pointer and a thin 10,000 ft pointer with a small marker at its tip. A striped sector shows on the face whenever the aircraft is below 10,000 ft, as a warning that the thin pointer has not yet completed a lap. The pressure window (the subscale) is set by the subscale knob: the pilot dials in a pressure datum there, and which pressure to set is the subject of the next module.
On an EFIS display the altitude is an altitude tape down the right-hand side of the screen, mirroring the altimeter's top-right place in the "Standard T" panel layout, with a digital pressure setting alongside it that is entered with knobs or buttons.
Source: Pooleys Vol 4 (10th ed.) p.336โ337.
The air reaches the altimeter through a small hole in the side of the aeroplane called the static vent. That is why pilots check it before every flight: if ice or an insect blocks the hole, the air trapped inside cannot change, the sealed can cannot swell or shrink, and the height dial freezes on the last reading even while the aeroplane keeps climbing or descending.
One more thing on the face: the little window. The pilot turns the knob to set a pressure number in it before flying. What number, and why, is the next lesson.
Source: Pooleys Vol 4 (10th ed.) p.336โ337.
Follow the blockage through. Ice the vent during a climb-out and the altimeter stays at the altitude where it froze: it under-reads. Block it in a descent and it holds a reading higher than you really are: it over-reads, which is dangerous where terrain clearance matters.
STRETCHA blocked static vent also upsets the airspeed indicator. Which reading would you trust more in a climb, and why?
Source: Pooleys Vol 4 (10th ed.) p.337.
Sensitivity. With pressure falling about 1 hPa per 30 ft near the surface, a 300 ft height change is only about 10 hPa of pressure change at the capsule. The gearing has to magnify a very small movement into a full pointer sweep, which is why build quality (instrument error) and response time (lag) matter.
Blockage arithmetic. A sealed static line holds the pressure of the moment it blocked. Climb a further 600 ft and the capsule should have seen roughly 20 hPa less pressure; it sees none of it, so the reading is about 600 ft low. Descend instead and the same trapped pressure leaves the reading high by the height lost since the blockage.
Position error is a property of where the vent sits on the airframe, not of the instrument, so a perfect altimeter can still be fed the wrong pressure.
Source: Pooleys Vol 4 (10th ed.) p.335โ337 (the 600 ft and 20 hPa figures are illustrative arithmetic from the 1 hPa per 30 ft rate).
Part 8 of 10 ยท Module AGK-24.5 ยท Aircraft General Knowledge
Full module (its own cards, game and quiz): AGK-24.5 ISA and Altimeter Settings (QNH, QFE, Standard)
Air has weight. Down at the beach the whole sky is piled on top of you, like sleeping under six duvets. Climb a mountain and there is less sky above, so the squeeze is lighter: three duvets. That squeeze is called pressure, measured in hPa, and it drops by about 1 hPa for every 30 ft you climb.
Your altimeter cannot see the ground. It only feels the squeeze and turns it into a number of feet. Squeeze your own fist gently, then harder: that is all the altimeter ever feels.
Source: Pooleys Vol 4 (10th ed.) p.338.
The weather changes the squeeze every day, and the altimeter has no idea. So the pilot tells it. There is a tiny window on the dial with a knob beside it. Dial in today's sea-level pressure, the number called QNH, and the altimeter now shows your height above the sea.
Why the sea? Because every hill and radio mast on the map is printed as a height above the sea. Same ruler, same starting line, so you can see at once whether you clear them.
Say it together: QNH, height above the sea.
Source: Pooleys Vol 4 (10th ed.) p.339.
Now dial in the pressure sitting on the airfield itself. That number is QFE. Parked on the runway the altimeter reads zero, and in the air it reads how far you are above the airfield. Handy when you are flying circuits round and round it.
But every airfield has its own pressure, so QFE from one airfield means nothing at the next. Fly away and it stops being useful.
Say it together: QFE, zero on the field.
Source: Pooleys Vol 4 (10th ed.) p.340.
Here is the trick that fools everyone. Sit still on the ground and wind the knob up: the needle climbs, even though you have not moved an inch. Wind it down and the needle sinks. You are not changing your height, only where the altimeter thinks "zero" is.
There is one more number pilots can dial in: 1013, the "standard" pressure everyone in the world agrees on. It is the pressure of an average day at the seaside, and the altimeter is built around it.
Try it on the sim: dial QNH, read the height. Dial QFE, watch it drop to zero on the runway.
Source: Pooleys Vol 4 (10th ed.) p.338โ340.
UK aviation switched from the millibar (mb) to the hectopascal (hPa) in 2011. The two are equivalent, so only the name changed; millibars still appear abroad and in older books. The USA uses inches of mercury and graduates its subscales in inches.
Real air varies from place to place and hour to hour, so aviation defines a fixed measuring stick, the ISA, and its main job is to calibrate altimeters:
Source: Pooleys Vol 4 (10th ed.) p.338.
The altimeter reads height above whatever pressure level is set in its subscale. The settings are called pressure datums, and the Q codes that name them are shorthand left over from the Morse era:
Pressure altitude is the height in the ISA above the 1013.2 hPa level at which the pressure equals the pressure at the aircraft. If the air round you has the pressure the ISA has at 6,800 ft, your pressure altitude is 6,800 ft, whatever your real height.
Source: Pooleys Vol 4 (10th ed.) p.339โ340.
Terrain and radio masts are charted as heights above mean sea level, so QNH is the setting for checking clearance above them. QFE is only useful while you stay near the aerodrome it came from: every aerodrome has its own surface pressure, so its own QFE. It is often used for circuit operations. In the UK the regional pressure setting (sometimes wrongly called regional QNH) is the lowest QNH in a defined region; its use is covered in Volume 2.
When you land, the altimeter should read zero with QFE set and the aerodrome elevation with QNH set.
Source: Pooleys Vol 4 (10th ed.) p.339โ341.
Hold a constant level and wind more hectopascals onto the subscale: the altimeter winds on more height, about 30 ft per hPa. Wind them off and the reading falls. The aeroplane has not moved; only the datum has. An invented example: level with QFE 996 set, the altimeter shows 2,100 ft above the airfield. Wind up to 1013 (17 hPa, about 510 ft) and it shows 2,610 ft pressure altitude. Wind on to a QNH of 1021 (another 8 hPa, 240 ft) and it shows 2,850 ft altitude.
Pre-flight checks on the apron: within 50 ft of the airfield elevation with QNH set; zero plus or minus 50 ft with QFE set; and the main scale must increase as the subscale increases, and vice versa.
STRETCHYou fly from high pressure towards low pressure without touching the subscale. As the flight goes on, does the altimeter over-read or under-read your real height? Reason it out from "wind off hectopascals, wind off height".
Source: Pooleys Vol 4 (10th ed.) p.340โ341.
Density altitude is pressure altitude corrected for non-standard (non-ISA) temperature. When it is high, the aircraft performs as though it were taking off or cruising higher than it really is. The performance consequences are covered under Flight Performance and Planning.
True altitude is the actual vertical distance above mean sea level. In a non-ISA atmosphere it is calculated from indicated altitude on the CRP-1, and the first step is always the pressure altitude. Invented example: QNH 998 hPa, indicated 4,000 ft. Standard 1013 sits 15 hPa higher, about 450 ft, so the pressure altitude is 4,450 ft; the OAT then goes into the CRP-1 to finish the correction.
Source: Pooleys Vol 4 (10th ed.) p.341.
Part 9 of 10 ยท Module AGK-24.6 ยท Aircraft General Knowledge
Full module (its own cards, game and quiz): AGK-24.6 The Vertical Speed Indicator
The VSI (vertical speed indicator) answers one question: are we going up, going down, or staying level? Needle above the middle: climbing. Needle below the middle: descending. Needle resting in the middle on zero: flying level. The number tells you how many feet you gain or lose every minute.
Try it: hold one arm out flat as the needle. Arm up, you are climbing. Arm flat, level. Arm down, descending.
Source: Pooleys Vol 4 (10th ed.) p.342โ343.
Picture a balloon sealed inside a biscuit tin, with one tiny pinhole in the lid. The balloon is joined to the outside air, so when you climb into thinner air it feels the change straight away. The tin only catches up slowly, one whisper of air at a time through the pinhole.
While the two are different, the balloon shrinks (climbing) or swells (descending), and that movement is what pushes the needle round. The faster you climb or descend, the bigger the difference, and the further the needle swings. Fly level and the two catch up with each other, so the needle drifts back to zero.
FOUNDATIONSReal VSI, real words: the balloon is a capsule, and the pinhole is called the metered leak.
Source: Pooleys Vol 4 (10th ed.) p.342โ343.
Because the tin takes time to catch up, the VSI takes a few seconds to tell the truth after you move the nose. Pitch sharply and it can even twitch the wrong way for a moment.
So on the sim: look out and set the nose picture you want, wait, then check the VSI to confirm your descent rate. If the VSI sits on zero while the ground is clearly getting closer, the small air hole feeding it (the static vent) may be blocked, and it will just keep reading zero.
Where to find it: on a classic panel it is the dial in the bottom right corner.
Source: Pooleys Vol 4 (10th ed.) p.343โ344.
You could estimate how fast you are changing altitude by timing the altimeter against a stopwatch, but that is tedious and distracting. The vertical speed indicator gives a direct read-out of the rate of change of altitude.
Like the altimeter, the VSI is a pressure instrument resting on the same fact: air pressure decreases with altitude. It converts a rate of change of static pressure into a rate of change of altitude, presented in hundreds or thousands of feet per minute (fpm, or ft/min). It is also known as the rate of climb indicator.
Source: Pooleys Vol 4 (10th ed.) p.342.
Static pressure is fed directly into a capsule. The case around the capsule receives the same static pressure, but only through a metered leak (a capillary, or "choke"), so the case pressure always lags behind.
Begin a descent and the new, higher pressure arrives inside the capsule at once while the case is still catching up through the choke. The capsule expands and a linkage drives the pointer round a scale graduated in fpm to show a rate of descent. In a climb the capsule pressure falls first, the capsule compresses, and the pointer shows a rate of climb. Mechanical stops limit the travel.
In level flight the pressures either side of the capsule equalise and the pointer rests on zero. A blocked or iced static vent produces the same equalisation, so the VSI reads zero even while the height is changing.
Source: Pooleys Vol 4 (10th ed.) p.343.
The practical habit: attitude first, VSI second. Set the pitch attitude, let the needle settle, then read the rate.
STRETCHWhy does a blocked static vent make the VSI read zero rather than freezing at its last reading? Think about what happens to the two pressures once nothing new can reach either of them.
Source: Pooleys Vol 4 (10th ed.) p.343โ344.
On a conventional panel the VSI occupies the bottom right corner of the standard instrument layout. On an EFIS screen the vertical speed is placed along the right-hand side for exactly that reason: the glass panel keeps the geometry a pilot already knows.
EFIS designs vary, but most present vertical speed as a tape that shows a rate of climb, a rate of descent, or level flight, with zero mid-tape, climb above it and descent below.
Source: Pooleys Vol 4 (10th ed.) p.343โ344.
๐ Activity
๐ฌ Part four
To land you first have to come down. Not a dive: a gentle, controlled slide downhill, with the dials telling you it is going to plan.
Part 10 of 10 ยท Module FT-8.2 ยท Flying Training
Full module (its own cards, game and quiz): FT-8.2 The Powered Descent
Going down in an aeroplane is gentle. You take a little power off, hold the nose a touch lower than level, and the aeroplane slides downhill through the air at the same speed it was flying before. Nothing dramatic happens. Picture a toy plane rolling down a gentle ramp: it does not fall, it just follows the slope.
Try it now: hold your flat hand out like a wing. Tip the fingertips down just a little. That is a descent. Point them at the floor and that is a dive, which is not what pilots do.
Source: Pooleys Vol 1 (15th ed.) p.127โ128.
Exercise 8b: control the rate of descent and the flightpath with power, while holding a constant airspeed. What the aeroplane does (its performance) depends on two things together: the power set with the throttle and the attitude held with the control column. To change how steeply you descend without letting the speed wander, you adjust both. That is exactly what happens on every normal approach to land, and in a cruise descent.
The rule to memorise: attitude controls airspeed; power controls rate of descent.
Source: Pooleys Vol 1 (15th ed.) p.127 and p.130.
In a descent each hand has one job. The throttle decides how fast you go down. The control column sets the nose position (the attitude), and that decides how fast you fly forward.
Think of a bike coasting down a hill. A steeper hill is like less power: you go down faster. Leaning is like the nose attitude: it changes your speed. Pilots use the two together: less power for a steeper slope, then the nose a little lower to keep the speed the same.
Source: Pooleys Vol 1 (15th ed.) p.130.
Monitor the rate of descent on the VSI (vertical speed indicator), or on the altimeter with a clock. Then:
A power change brings a pitch and yaw tendency: balance it with rudder and column pressure. Watch the ASI while you set the new attitude.
Source: Pooleys Vol 1 (15th ed.) p.129โ130.
Two dials tell you if the descent is right. The VSI shows how fast you are going down: the further its needle drops below the middle, the faster you are descending. The ASI shows how fast you are flying forward.
Class action: left hand is the VSI needle, right hand is the ASI needle. When the instructor says "add power", the left hand rises towards the middle (descending more slowly) and the right hand stays put, because the nose comes up to keep the speed the same.
Source: Pooleys Vol 1 (15th ed.) p.128โ130.
Hold a constant nose attitude and find the ground feature that stays fixed in the windscreen: that is your aiming point, where the descent will meet the ground. On the approach, adjust the flightpath with power and attitude until the chosen point on the runway is the one that stays still, and act positively the moment it is not.
The cruise descent saves time at the end of a long cross-country: start down some miles out, reduce power slightly and lower the nose so the airspeed stays at the cruise figure.
STRETCHTwo aeroplanes descend at the same airspeed, one with more power. Which has the higher nose attitude, and which reaches the ground first?
Source: Pooleys Vol 1 (15th ed.) p.128โ129.
If the ground is coming up too quickly, do not pull the nose up on its own. Add some power and let the nose come up a little to keep the speed. The slope gets gentler and you reach the ground further ahead. Need to get down sooner? Take some power off and hold the nose a little lower. The slope gets steeper.
Pilots have a trick for knowing where they will land: whatever spot on the ground stays still in the windscreen is where you are heading. Hold a finger on it and watch.
Source: Pooleys Vol 1 (15th ed.) p.128โ130.
Even with power on, the setting is lower than normal, so engine icing remains a threat. In a prolonged descent, warm the engine periodically and use carburettor heat as required. Keep an eye on the RPM as you do.
The classic error on approach is not controlling the rate of descent enough. Decide the airspeed and rate of descent you want and take positive action to get them, while keeping a good lookout. Airmanship in this exercise means positively controlling your flightpath and airspeed.
Source: Pooleys Vol 1 (15th ed.) p.128โ129.
In a glide, a component of weight acting along the flightpath does the pulling that balances drag. Apply power and the thrust now balances some of that drag, so the weight component along the flightpath does not need to be as large for the same airspeed. A smaller weight component means a shallower flightpath, hence a higher pitch attitude and a lower rate of descent than the glide at the same speed. This is why the pitch attitude for a powered descent is not as low as for the glide.
Source: Pooleys Vol 1 (15th ed.) p.127. The glide itself is module FT-8.1.
๐น๏ธ Put it together
The instructor goes first, then everyone gets five minutes. Keep your eyes moving between the runway and the three dials. The instructor talks you through the last part, the landing itself, which you will learn properly later in the course.
Coach questions: What do you notice on the VSI right now? Is the airspeed holding? Which control fixes a dropped wing? Which pedal straightens the nose?
โ Quiz
Twelve questions covering this week and last week. Do it while you wait for your simulator turn. It counts towards signing off 1.2, 1.3 and 1.4 in your logbook.
๐ Wrap up
Quick questions: what does the VSI tell you? Which control did you use to keep the wings level? What was the attitude when you landed?
Book tip: How to Become a Pilot: The Ultimate Guide to Aviation. Website tip: NASA's Science in the Air pages at nasa.gov.
Next week: pre-flight checks, flying straight and level, climbing and descending.
Resources: model aeroplane, plain paper for paper aeroplanes, revision cards, board pens, the end-of-topic quiz (the โ Quiz tab, or the paper sheet), logbooks. Simulator set up at a big airport with a long runway (the BYP plan uses Heathrow) in a simple trainer.
Pre-class: play a flying clip as they arrive and ask who has seen it (the BYP deck used the Top Gun: Maverick trailer, youtu.be/qSqVVswa420, verified live 2026-09-16). Ask who has booked their flight yet.
Sign-offs this week: 1.2 flying controls and the three axes, 1.3 effects of the controls, 1.4 reading basic instruments. Mark the quiz by next week, then tick the first three topics in their syllabus and logbooks.
Present mode: press โถ Present (top right) and use the arrow keys or a clicker. Foundations is the Wings layer; tap PPL on if an older group wants more. The ๐ฒ Dice tab cold-calls a student with a flash card from any module in this lesson.
Instructor copy only.
Misconception 1: "the rudder turns the aeroplane." Pooleys' bicycle line kills it: a yawing turn is like turning a bike without leaning. Ailerons bank, rudder balances.
Misconception 2: "the elevator makes it go up." It sets the nose attitude; the airspeed changes as a result. Attitude first, then centralise.
Props: one paper aeroplane per pair. Fold, fly, then bend one surface at a time (tail edge up, one wing edge up and the other down, a small tab on the fin) and fly again. The class sees pitch, roll and yaw happen.
Hook: "stand up and be the aeroplane" (nod, tilt, twist) before a word of theory. Then the game: it is Wings sign-offs 1.2 and 1.3 in one screen.
Delivery tip: pressures, not movements. Let students "follow through" on the sim yoke while you demonstrate, and use the "You have control" / "I have control" handover every time, even on the sim.
Wings delivery: project the four Foundations cards in Present mode (about 12 minutes, one wobble per card), run the paper-aeroplane activity (10 minutes), then play the Which-control game on the projector with the class calling answers (5 minutes). Sim slot afterwards: elevator first (attitude and airspeed), then ailerons, then rudder against a reference point, exactly the Airwork 4a order.
Instructor copy only. Sources: Vol 1 (15th ed.) p.30โ40.
Misconception: "the rudder steers the aeroplane like a car." On these pages the rudder yaws the nose; keep the language to yaw, and let FT-4.1 and the sim show what actually turns it.
Misconception: "longitudinal control means roll." Pooleys' phrase is "longitudinal control in pitch": it describes the plane of control, not an axis name. Drill pitch, roll, yaw out loud. The formal axis names belong to POF-6.2 and FT-4.1, not here.
Props: a paper plane with three skewers through its balance point (nose to tail, wingtip to wingtip, top to bottom): spin it on each one. A door for the leverage demo: push by the hinge, then by the handle.
Hook: the whole class nods, tips and shakes their heads on command, then flies a flat hand: "nose up", "left wing down", "nose right". Speed it up until they laugh.
Delivery tip: when a child calls the stick-sideways motion "turning", accept it and rename it roll on the spot; the turn itself is FT-4.1's story.
Wings delivery: project the three Foundations cards (about 8 minutes) with the head-and-hand drill after card one, then put the label game on the projector and have volunteers tap the six chips (about 7 minutes). Fifteen minutes total, then straight to the sim for FT-4.1's primary effects. Wings sign-off 1.2.
Instructor copy only. Sources: Vol 4 (10th ed.) p.87โ88.
Misconception 1: "the down-going aileron pushes that wing down." It is the opposite: the down-going aileron makes more lift, so that wing rises. Drill the pair "down aileron, wing up" until it is automatic.
Misconception 2: "adverse yaw means the aeroplane refuses to turn." It still rolls and turns; the nose just starts by swinging the wrong way until rudder tidies it up.
Props: two rulers taped to a pencil (the pencil is the fuselage, the rulers the wings) to show one aileron up and one down; a rowing mime with two imaginary oars for the yaw.
Hook: ask who has held an arm out of a car window. Flat hand, nothing much. Tilt the front edge up and the arm gets shoved up AND back. That is the down-going aileron in one gesture.
Delivery tip: stand facing away from the class so left and right match theirs when you do the arms-out roll. Say the drill out loud with them: "stick left, foot left".
Wings delivery: project the three Foundations cards (about 6 minutes), run the arms-out roll-and-yaw drill from card 3 (2 minutes), then the "Which aileron?" sort game on the projector with the class voting by hand (5 minutes). Total about 15 minutes; it slots into Week 2 effects of controls before the sim, and pays off again in Week 4 turning. Sign-off 6.3.
Instructor copy only. Sources: Vol 4 (10th ed.) p.91โ94.
Misconception 1: "attitude is how the pilot feels." Kill it in the first minute: attitude is a picture, the aeroplane against the horizon. Hold the model up and say the word every time you move it.
Misconception 2: "angle of attack and attitude are the same." The source is explicit that one is measured against the relative airflow and the other against the horizon. For Foundations, leave angle of attack out entirely.
Misconception 3: "the balance ball shows which way you are turning." It shows balance. Feet push towards the ball to centre it.
Props: a model aeroplane (attitudes against the wall-top horizon); a marble in a clear curved tube, or a spirit level, for the balance ball; a picture of a bike on a hill for the two ingredients, angle plus pedalling.
Hook: "Perfect straight and level is almost impossible. Even airline captains are correcting all the time; the good ones just correct early and small." Then reveal the one or two second instrument glance rule: most of the time the pilot is looking out of the window.
Delivery tip: the whole exercise collapses to two loops. Loop one: select attitude, hold, adjust, trim. Loop two: Lookout, Attitude, Instruments. Write both on the board before the sim and point at them while students fly.
Wings delivery: Week 2 "Attitude and Performance" segment, about 20 minutes. Project the four Foundations cards in Present mode (roughly 10 minutes): arms-out level walk on L1F, model aeroplane demo on L2F, bicycle-on-a-hill on L3F, then the peek rule and the ball on L4F. Run the "Attitude or Performance?" sort on the projector as a whole-class tap game (about 5 minutes; a ten-year-old should clear it after the cards). Then straight onto the sim: cruise power set, hold height and heading for two minutes using Lookout, Attitude, Instruments. Weeks 3, 6 and 7 (sign-offs 6.2 and 7.1) reuse the PPL cards L1 to L4 and the flash-card dice.
Instructor copy only. Sources: Vol 1 (15th ed.) p.77โ90.
Misconception 1: "the pitot tube measures speed." It measures total pressure; speed only appears when the ASI subtracts the static pressure. Keep saying "the ASI compares the two".
Misconception 2: "the static vent is an air intake." Nothing flows through it; it just senses the pressure outside. Flush hole, not a scoop.
Prop: a desk fan or hairdryer and a drinking straw. Straw pointing into the airflow (pitot) versus straw held sideways across it (static): a finger over the far end feels the difference.
Hook: the hand out of the car window. Every child has done it; palm forward versus palm flat sideways is the whole module in one gesture. Say "PEE-toe" from the first mention so nobody settles on "pit-ot".
Delivery: Foundations groups keep the Technical toggle off. Do not drift into how the dials work inside (that is AGK-24.2, 24.4 and 24.6); this module is the plumbing only.
Wings delivery: Week 2 (sign-off 1.4, reading instruments). Project the four Foundations cards (about 8 minutes), do the palm-forward / palm-sideways action on card 2, then run the label game on the projector with the class calling out which box each name belongs in (about 8 minutes). Close with three or four dice-roll flash cards. Around 20 minutes, straight before the sim, where the same three dials are on the panel.
Instructor copy only. Sources: Vol 4 (10th ed.) p.323โ327.
Misconception 1: "the ASI shows how fast we are going over the ground." Use the swimmer in a river: the pitot tube only feels the air going past, so the dial shows speed through the air.
Misconception 2: "yellow is just a faster green." Yellow is a permission with a condition (smooth air only); red is a wall. Say it that way and it sticks.
Props: a hairdryer and a strip of paper (harder blow, bigger bend, bigger number), or the hand-out-of-the-car-window memory every child already has. A printed dial with the arcs coloured in makes the game tangible before the projector version.
Hook: ask who has seen a car speedometer with two rings of numbers (mph and km/h). The knots-plus-mph ASI is the same trap, and pilots have to know which ring they are reading.
Delivery tip: teach the arcs as a traffic-light rule before any V-speed letters. Only the PPL layer needs VS0, VS1, VFE, VNO, VNE; at Foundations the colours carry the whole meaning. The gentle rhyme on the Foundations card ("white is for flaps, green means go, yellow means gently, red means no") replaces the older, harsher classroom version.
Wings delivery: Week 2 (sign-off 1.4, reading instruments; revisited Week 11). Project the four Foundations cards in Present mode (about 10 minutes, with the hand-out-of-the-window and traffic-light call-outs), then run the labelling game on the projector with volunteers tapping the chips (about 5 minutes), then go straight to the simulator and have the class read the ASI aloud during the take-off roll and on the approach: "white arc, flaps allowed" and "green, all good" become the sim commentary.
Instructor copy only. Sources: Vol 4 (10th ed.) p.328โ331.
Wings delivery: project the four Foundations cards in Present mode (about 12 minutes): the crisp-packet card, "read it like a clock", the two practice dials (answers are behind the "Show the answers" fold, so cold-call before you open it), then the static-vent card. Follow with the labelling game on the projector with the class calling the taps (5 minutes), then send them to the sim to watch the altimeter wind up in a climb and back down in a descent. Total about 20 minutes, sign-off 1.4 "reading instruments".
Misconception 1: "the altimeter measures how far above the ground I am." It measures pressure and shows a height above whatever pressure is set in the window. Do not chase this in Week 2; just plant the phrase "it is a barometer in disguise" and leave QNH/QFE to the next module.
Misconception 2: "the long pointer is the big number, like the hour hand." It is the opposite of a clock: the long slim pointer is the hundreds, the short fat one is the thousands. Drill "short first, then long" until it sticks.
Props: a sealed crisp packet (or a balloon tied off part-inflated) and a photo of one puffed up at altitude; a wall barometer if you have one. A bike pump with your thumb over the outlet shows air being trapped, which sets up the blocked-vent story.
Hook: "This dial cannot see the ground. So how does it know how high you are?" Let them guess before the crisp packet comes out.
Delivery tip: when the practice dials come up, make every student commit an answer out loud before revealing. Reading errors of a full thousand feet are common at first and are exactly the habit you want to break early.
Boundary: pressure settings, ISA and the QNH/QFE/standard datums live in AGK-24.5. Here the window is only "where the pilot sets a pressure".
Instructor copy only. Sources: Vol 4 (10th ed.) p.335โ337.
Misconception: "the altimeter measures height." It measures pressure and converts it to feet using the ISA, which is exactly why the pilot has to feed it a datum. Every other idea in the module hangs off that sentence.
Misconception: "QFE is the safe one." Zero on the runway feels comforting, but hills and masts are charted above sea level, so QNH is the clearance setting. QFE is for staying near one airfield.
Prop: any altimeter, and a sim panel counts. Sit still, wind the knob, let the class watch the needle move while the aeroplane does not. Then the reverse: same subscale, climb, and the needle moves for a real reason.
Hook: ask who has felt their ears pop coming down a big hill in a car. The altimeter is an ear that never stops popping.
Delivery tip: keep the ISA numbers (1013.2, 15ยฐC, 2ยฐC per 1,000 ft) on the PPL cards. The Foundations class needs only "pressure drops as you climb, about 30 ft per hPa", QNH, QFE and 1013 as a name.
Wings delivery: Week 2 (reading instruments, sign-off 1.4). Project the four Foundations cards (about 6 minutes, with the two chants), play the QNH / QFE / 1013 sort game as a whole class on the projector (about 5 minutes), then on the sim: dial QNH and read the altitude, dial QFE and watch it fall to zero on the runway (about 4 minutes). Roughly 15 minutes in all. The Week 2 quiz answer they must leave with: QNH reads height above sea level.
Instructor copy only. Sources: Vol 4 (10th ed.) p.338โ341.
Misconception 1: "the VSI tells me my height." It does not; it tells you how fast the height is changing. Zero means level, not "on the ground". The sort game's "parked with the engine running" item is there to surface this.
Misconception 2: "the needle moves the instant I pitch." The lag is several seconds, and a sharp pitch change can flick it the wrong way first. Drill the habit: attitude first, VSI second.
Prop: a balloon inside a biscuit tin with a pinhole in the lid. The balloon is the capsule, the pinhole is the metered leak; no equations needed for the whole mechanism.
Hook: the sim landing. On final ask "what do you notice on the VSI right now?", then "look at your descent rate". Have them say the number out loud in feet per minute.
Delivery tip: project the three-dial slide and get every arm in the room pointing up, flat or down before touching a mouse.
Wings delivery: Week 2 (reading instruments, sign-off 1.4). Project the three Foundations cards (about 8 minutes: dial, biscuit tin, lag), run the Up/Down/Level sort game as a whole-class tap-and-shout round (about 5 minutes), then carry it into the sim landing where you call "VSI check" twice on final and once after the flare. Total about 15 minutes of the session.
Instructor copy only. Sources: Vol 4 (10th ed.) p.342โ344.
Misconception: "push the nose down to go down faster." On its own, nose-down gives more airspeed, not a steeper descent at the same speed. It is the power reduction that steepens the path; the lower nose only keeps the speed where it was. Say the two-job rule until it is boring: attitude controls airspeed, power controls rate of descent.
Props: a toy plane on a gentle ramp (a descent is a slope, not a drop). A bike coasting down a hill: the gradient is the power setting, the lean is the attitude.
Hook: the aiming point. Put a finger on the projector screen or a window: the spot that stays still under your finger is where you are going. Children get this instantly and it is the same trick they will use on the sim approach.
Delivery tip: teach the pair of drills as symmetrical: add power and raise the nose, or take power off and lower the nose. Then send them to the VSI and the ASI to see the effect. Never teach one without the other or they will chase speed with power on the sim.
Wings delivery: project the four Foundations cards (about 8 minutes, hands-as-needles action on card 3), run the "Power or attitude?" sort game as a whole-class tap vote (5 minutes), then straight to the sim: "reduce power, lower the nose, descend and land the plane", coaching only "look at your descent rate" and "keep the speed the same". Sign-off 7.2 comes from the sim, not the slides.
Scope note: levelling off and the step-by-step descent entry are not on these pages; they live in the glide exercise (FT-8.1). Do not test them from this module.
Instructor copy only. Sources: Vol 1 (15th ed.) p.127โ130.
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