# Principles of Flight – About ATPL Subjects

In Principles of Flight, you’ll study lift, drag, thrust, and weight as they affect an aircraft during flight.

Aerodynamics, limitations, and stability will also be discussed during this subject.

This subject requires a good understanding of mathematics.

This is only meant as a guide to the Principles of Flight subject as it applies to the Bristol Groundschool ATPL (A) theory course.

### Principles of Flight (Fixed-Wing) Topics

Below is a look at the individual topics the Bristol Groundschool ATPL (A) course breaks Principles of Flight into and some of the things you’ll learn about in each topic.

The Derivation of Lift

Dynamic pressure, Bernoulli’s theorem, Lift, angle of attack, cambered aerofoils and aerodynamic centre.

Parasite and Induced Drag

Friction drag, turbulent flow, interference drag, induced drag, ground affect and factors that affect induced drag.

Drag Reduction and Total Drag

Minimising induced drag, winglets and induced drag, wing platforms, wake turbulence, the effect of altitude and polar diagrams.

Forces in Level Flight

The forces of level flight, canard configuration, attitude in level flight and stick forces in level flight.

High Speed Flight

The speed of sound, Mach numbers, shock waves, MDET and the bow wave, critical mach number and transonic flight.

Forces in Transonic Flight

Effect of match number on CL and lift, compressibility, shockwaves, the shock stall, supersonic flight, transonic stability, thin wings, swept wings and reducing wave drag.

Climbing and Descending

Forces in the climb, lift in the climb, small climb angles, climb gradient, factors affecting flight path angle, the glide decent and wind.

Turning

Turning and load factors, radius of turn, turning calculations, turn rates, coordinated turns, skidding turn and the hazards of excessive use of rudder.

Stalling

The stall, boundary layer separation, lift and drag at the stall, stall development, control at the stall, swept wing problems, stall warning, level flight, stall recovery, stalling speed, the effect of altitude, CG position and thrust.

Swept Wing Staling and Spinning

Swept wings, deep stall (or superstall), icing and contamination, spinning and the standard spin recovery.

High Lift Devices

High lift devices, vortex generators, flaps, leading edge devices and slats.

Controls Basics

Control basics, coefficients of moment, controls, aerodynamic forces, trim and balance tabs, servo tabs and gear change.

Control – Roll, Pitch, Yaw and Flutter

Ailerons, spoilers, roll response, control in pitch, slab tails, stabiliser trim, control in yaw, crosswind landings, flutter, fly-by-wire controls (FBW), CG position and protection systems.

Stability Basics and Longitudinal Stability

Static stability, dynamic stability, long and short period stability, pilot induced oscillation (PIO), aircraft stability, AC and CG position, wing moments, canards and longitudinal dihedral.

Factors Affecting Stability

Engine thrust, propellers. centre of gravity limits, mean aerodynamic chord, stick forces and stability, mass and weight and manoeuvring stability/stick force per g.

Directional, Lateral and Speed Stability

Directional stability, effectiveness of the fin, yaw and slideslip angles, lateral static stability, sweepback, anhedral, spiral instability and speed stability.

Propellers

Forces acting on the propeller, the effect of forward speed, effect of TAS and power changes, varying propeller RPM, high speed dive, engine failure, feathering, secondary affects and noise.

Forces in Asymmetric Flight

Asymmetric flight, trust and blade effect, the critical engine, counter-rotating propellers, asymmetric drag and lift in asymmetric flight.

Asymmetric Control Problems

Asymmetric sideslip and minimum control speeds, eliminating sideslip “five to the live”, minimum control speeds, VMCG and factors affecting VMCG, take-off safety speed and VMCL.

Limitations and Gust Response

Landing gear and flap limitations, load factor limitations, design airspeed limitations, the effect of altitude, the gust envelope, speed of flight in turbulence, gust response and gust load factor, altitude limits, and buffet boundary charts.

Severe Weather, Icing and Stalling

Flight in icing conditions, wind and rudder icing, contamination and weight growth, horizontal wind shear, steep turns, wake turbulence, thunderstorms and unreliable airspeed.

### Principles of Flight Exams

The exam for Principles of Flight lasts 1 hour and 30 minutes. You’ll have 46 multiple-choice questions to answer during this time, with the pass rate being 75%.

### An Example of a Principles of Flight Exam Question

This is an example of the type of question you may have in a Principles of Flight exam. For more questions like this one, visit the BGSonline question bank to start revising with over 15,000+ ATPL, CPL, IR and PPL questions. Subscriptions start from £23 for one month for access to ATPL/CPL questions.

Question: What can happen to the aeroplane structure flying at a speed just exceeding VA?

A) It may suffer permanent deformation if the elevator is fully deflected upwards.

B) It may break if the elevator is fully deflected upwards.

C) It may suffer permanent deformation because the flight is performed at too large dymanic pressure.

D) It will collapse if a turn is made.

The answer is A, It may suffer permanent deformation if the elevator is fully deflected upwards.

If the elevator is fully deflected upwards at VA, the aircraft will stall at the limit of 2.5g. If flying at a speed above VA, 2.5g will be exceeded without the aircraft stalling (VA is known as the design manoeuvre speed.)

### Need Help Revising for your ATPL or CPL Exams?

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BGS Video Library covers ATPL (A & H), and CPL (A & H) topics and subjects, including Principles of Flight.

Interested? Take a look at our webinar preview below of Principles of Flight – Drag