How do aeroplanes fly?

Aeroplanes fly because wings moving through the air at a suitable angle create lift; powered aircraft use a jet engine or engine-driven propeller to provide thrust and maintain speed. When lift supports weight and thrust balances or overcomes drag, the aircraft can take off, climb, cruise, turn and descend under control.

In Aviation & Real-World Flying, the same aerodynamic principles apply as they do in the real aircraft. Every fixed-wing aeroplane, from a glider to an airliner, is managing four forces: lift, weight, thrust and drag.

How do planes fly? Start with the four forces

Every fixed-wing aircraft flies by balancing or deliberately unbalancing lift, weight, thrust and drag.

In steady, straight-and-level flight, lift equals weight and thrust equals drag. If thrust temporarily exceeds drag, the aircraft accelerates. If the force balance changes vertically, it begins to climb or descend.

A steady climb does not require lift to remain greater than weight. Excess power establishes the climb, after which the forces settle into a new balance along the inclined flight path. Basic four-arrow diagrams are useful, but they do not show every force component in a climb, descent or bank.

Engines do not hold an aeroplane up directly. They maintain the airflow and energy that allow the wings to generate lift; a glider obtains that energy by gradually trading height for forward speed. Our explanation of how flight simulators calculate lift, drag, thrust and aircraft response covers how these forces become a flight model.

What creates lift on an aeroplane wing?

A wing creates lift by establishing a pressure difference around itself and deflecting air downwards.

These are not competing explanations. The altered pressure field around the wing and the downward change in the air’s momentum describe the same aerodynamic process from different viewpoints. Air passing over the top is not required to meet the same parcel of air that went underneath at the trailing edge; that common equal-transit explanation is incorrect.

A useful shorthand is L = ½ρV²SC_L. Lift depends on air density, true airspeed through the air, wing area and the coefficient of lift. That coefficient changes mainly with wing shape, configuration and angle of attack.

Angle of attack is the angle between the wing’s chord line and the oncoming relative airflow. It is not the same as pitch attitude, which is the aeroplane’s orientation relative to the horizon. An aircraft can have a nose-high attitude with a moderate angle of attack in a climb, or reach a high angle of attack while descending.

Wing shape helps create an efficient pressure distribution, but curvature alone is not what makes flight possible. Symmetrical aerobatic wings and even suitably angled flat plates can generate lift. Flaps and slats alter the wing’s shape or airflow so that it can produce more lift at a lower speed, usually with extra drag.

Why does airspeed matter more than groundspeed?

Wings respond to movement through the surrounding air, not movement over the ground.

Pilots therefore use indicated airspeed for most take-off, approach and stall references because it reflects aerodynamic loading more directly than groundspeed. The precise target speeds still come from the aircraft’s operating data and depend on weight and configuration.

A headwind increases airflow over the wing for a given groundspeed and normally shortens the take-off run. A tailwind does the opposite. The aeroplane may lift off at roughly the same indicated airspeed, but its groundspeed and runway distance will be greater with a tailwind.

How does take-off actually work?

Take-off occurs when the aeroplane accelerates to the required airspeed and rotates to an angle of attack that can support flight without stalling.

1. Power is applied. Thrust overcomes aerodynamic drag and the rolling resistance of the wheels.
2. The aircraft accelerates. Increasing airflow makes the wings and control surfaces more effective.
3. The pilot rotates. At the appropriate rotation or lift-off speed, gentle nose-up input increases the wing’s angle of attack.
4. The wheels unload. Lift builds until the runway no longer needs to support the aircraft.
5. The climb is established. Pitch, power, trim and flap configuration are adjusted for the required climb speed.

There is no universal rotation speed. Aircraft type, weight, centre of gravity and flap setting determine the reference speeds, while wind, runway slope, surface condition and available length affect the ground run.

Density altitude also matters. On a hot day or at a high airfield, the aircraft needs a higher true airspeed to reach the same indicated airspeed, while the engine or propeller may produce less thrust. The result is usually slower acceleration and a longer take-off distance.

A common simulator mistake is pulling back too early or holding excessive nose-up input. Attitude alone cannot replace airspeed; it only increases drag and may cause a stall or tail strike. Wrong trim, excessive weight, deployed spoilers, an incorrect flap setting or a misconfigured control axis can also prevent rotation. Use our take-off troubleshooting checklist for an aircraft that will not rotate if the aeroplane races along the runway but refuses to unstick.

What keeps an aeroplane flying after take-off?

Once airborne, the pilot or autopilot manages pitch, power, speed and configuration so that the wings continue producing the required lift.

In straight-and-level cruise, lift balances weight and thrust balances drag. In a climb, engine power adds potential energy. During a descent, some height is converted into speed or used to overcome drag.

Pitch and power are linked rather than independent controls. Changing either one can affect airspeed, vertical speed and angle of attack, so the aeroplane must be allowed to settle before it is retrimmed. Trim relieves sustained control pressure; it does not create lift, lock the attitude or act as an autopilot.

At altitude, thinner air produces a higher true airspeed for a given indicated airspeed. Many aircraft can cruise efficiently there, but available thrust, Mach limits and stall margins are type-specific, so higher altitude is not automatically better.

How do pilots make an aeroplane turn without falling?

Pilots turn by banking the aeroplane, which tilts the lift force and gives it a horizontal component that pulls the aircraft around the turn.

Because part of the lift is now acting sideways, a level turn requires greater total lift. The pilot normally adds back-pressure or trims as appropriate to increase angle of attack. This raises load factor and stall speed; in an ideal 60-degree banked level turn, the load is 2g and stall speed is about 41 per cent higher than in wings-level flight.

• Ailerons roll the aircraft and establish the bank.
• Elevator controls pitch and helps set the required angle of attack.
• Rudder controls yaw and coordinates the turn rather than acting as the normal primary turning control.
• Flaps increase lift and drag for low-speed phases such as take-off and landing.
• Spoilers or airbrakes reduce lift and increase drag on aircraft fitted with them.

Why do aeroplanes not fall if the engine stops?

A fixed-wing aeroplane with an engine failure descends in a glide rather than dropping straight down.

As it moves forwards and downwards, airflow continues over the wings and they continue to generate lift. Gravity supplies the energy previously provided by the engine, so the aircraft trades altitude for distance.

The pilot’s immediate aerodynamic priority is to establish the published best-glide speed. Flying too slowly risks a stall, while flying too quickly normally reduces the distance available. Wind changes the distance covered over the ground but not the basic glide through the surrounding air.

Airliners, light aircraft, fighters and purpose-built gliders all obey these fixed-wing principles, although their glide performance and operating speeds differ greatly. Helicopters use rotating wings and rely on autorotation rather than a fixed-wing glide after a total loss of power.

What is a stall, and is it the same as engine failure?

A stall occurs when a wing exceeds its critical angle of attack; it is not caused simply by low speed or by an engine stopping.

Beyond the critical angle, airflow separation grows, lift stops increasing normally and drag rises sharply. Warning signs may include buffet, a stall warning, weak control response, an uncommanded roll or a nose drop, depending on the aircraft and flight model.

Low speed makes a stall more likely because the pilot must use a higher angle of attack to maintain lift. However, an aircraft can also stall at high speed during a hard pull-up or steep turn. The wing can be stalled with full engine power, while an aircraft with no power can remain fully unstalled in a controlled glide.

The first aerodynamic action in a stall recovery is to reduce angle of attack. The pilot then levels the wings as appropriate, applies power if available and manages the configuration according to the aircraft’s procedure. Pulling harder to stop the descent delays recovery.

How can I see these forces in a flight simulator?

The clearest simulator demonstration is to use a simple training aircraft, calm weather and plenty of altitude, then change only one control at a time.

1. Establish straight-and-level flight. Trim the aircraft and record its indicated airspeed, power setting and pitch attitude.
2. Reduce power slightly. Watch the speed decay and note how pitch must change if you want to hold a chosen speed or altitude.
3. Enter a medium bank. Apply enough back-pressure to maintain height and observe the higher angle of attack and load factor.
4. Practise slow flight. Extend flaps in stages and compare the lower speed capability with the extra drag and changed pitch response.
5. Approach a stall at safe simulated altitude. Recognise the warning, reduce angle of attack and recover without pulling abruptly.
6. Try an idle-power glide. Hold the aircraft’s recommended glide speed and observe how altitude becomes the source of forward energy.

Automation, auto-rudder and simplified assistance settings can hide some of these effects, while individual aircraft add-ons vary in flight-model quality. A complete circuit is the best way to combine acceleration, lift, turns, descent and landing; our guide shows how to practise a correct traffic pattern in the simulator.