Loading and Performance: forces of flight, stalls, load factor, CG and performance factors
The short version
- Much of this section is about FIXED-WING aerodynamics even though most students fly multirotors. That is deliberate - the certificate covers any sUAS, so the exam asks about wings, stalls and CG whether or not you own one.
- Four forces - lift opposes weight, thrust opposes drag. On a multirotor thrust comes from TILTING the lift vector, not from a separate propeller.
- A stall is the WING losing lift at the critical angle of attack. It has nothing to do with the engine, and it can happen at any airspeed and any weight.
- Load factor rises with bank angle and raises stall speed with it - a 60 degree bank is 2 G. This is what kills people manoeuvring low and slow.
- Performance drops with high altitude, high temperature, high humidity and extra weight. The manufacturer's flight time is a laboratory number.
The concepts
RPIC responsibility for loading 0:02:55
The remote pilot in command must verify before flight that the aircraft is loaded properly - within the manufacturer's weight limits, with any payload secured, and positioned so the balance is not upset.
Loading must comply with the manufacturer's weight and balance specifications.
The governing documents are the Pilot's Operating Handbook or the UAS Flight Manual, depending on what the manufacturer calls it.
Three axes of rotation and their controls 0:04:20
Roll about the longitudinal axis (ailerons), pitch about the lateral axis (elevator), and yaw about the vertical axis (rudder).
The same three axes apply to a multirotor - right stick rolls and pitches, left stick yaws, throttle climbs and descends.
The instructor is explicit that airplane questions WILL appear on the exam because the certificate is not multirotor-specific.
This is not a quadcopter license that you're getting. You're getting a small UAS license, and a small UAS can be a lot of different things.0:04:20
The four forces of flight 0:07:35
Lift opposes weight; thrust opposes drag. Lift acts at the CENTER OF PRESSURE (also called centre of lift); weight acts at the CENTER OF GRAVITY.
In straight-and-level unaccelerated flight lift equals weight AND thrust equals drag.
Thrust equal to drag does not mean stationary - it means CONSTANT speed. Thrust greater than drag means accelerating.
On a fixed wing, thrust comes from the propeller (itself an airfoil producing horizontal lift) along the longitudinal axis.
On a multirotor there is no separate thrust source - tilting the aircraft splits the rotor lift into a vertical component (opposing weight) and a horizontal component (thrust).
Weight always acts toward the centre of the earth.
Airfoil terminology and angle of attack 0:12:04
Relative wind is parallel to the flight path but opposite in direction. The chord line runs from leading edge to trailing edge. The ANGLE OF ATTACK is the angle between the chord line and the relative wind.
Lift acts perpendicular to the RELATIVE WIND, not to the ground.
Lift is proportional to airspeed and to angle of attack - go faster or raise the angle of attack to make more lift.
The resultant force is lift and drag combined.
Angle of attack is NOT the same as pitch attitude - an aircraft can be nose-down and still at a high angle of attack.
Newton's third law and Bernoulli's principle 0:17:16
Lift arises from two complementary effects - air deflected downward produces an equal and opposite upward reaction (Newton), and faster airflow over the curved upper surface produces lower pressure than beneath (Bernoulli).
The hand-out-of-a-car-window analogy is Newton's third law in action.
Bernoulli - constricting flow raises speed and lowers pressure, like pinching a hose.
Higher pressure beneath moves toward lower pressure above, helping lift the wing.
Parasite drag - form, interference, skin friction 0:26:14
Drag that is a byproduct of moving through the air. It INCREASES with airspeed.
FORM drag - the shape of the object.
INTERFERENCE drag - created where two components join; the whole is draggier than the sum of the parts measured separately.
SKIN FRICTION - rivets, chipped paint, insect strikes and other surface imperfections disturbing the airflow.
Induced drag 0:29:28
Drag generated as a byproduct of producing lift. It DECREASES as airspeed increases - the opposite of parasite drag.
The greater the angle of attack, the greater the induced drag.
High angle of attack generally means low airspeed, so induced drag dominates when slow.
On a multirotor induced drag appears once the aircraft moves laterally.
Stalls and the critical angle of attack 0:32:28
A stall occurs when the airfoil exceeds the CRITICAL ANGLE OF ATTACK and airflow separates from the upper surface, destroying lift. It concerns the WING, not the engine.
A wing stalls at the critical angle of attack REGARDLESS of airspeed, weight, attitude or CG position.
It is usually associated with low airspeed but can occur at high speed - for example an abrupt pull-up from a fast descent.
Recovery is to LOWER the angle of attack, which for a fixed wing means lowering the nose.
Multirotors do not stall in this sense - lift comes from powered rotors, not a fixed wing.
A stall can happen at any airspeed, but it's usually associated with flying at very low speed.0:32:28
Load factor and bank angle 0:36:51
Load factor is the ratio of the load the structure carries to the actual weight of the aircraft - the G force. It increases with BANK ANGLE in a level turn.
30 degree bank = 1.154 G; 45 degrees = about 1.4; 60 degrees = 2.0 G; 80 degrees = about 5.7 G; 85 degrees = about 11.5 G. The curve is exponential.
At 60 degrees of bank a 10 lb aircraft imposes a 20 lb load on its structure.
Load factor rises in ANY manoeuvre other than straight-and-level - not only turns.
Exceeding the structural limit can fold or shed a wing.
Load factor raises stall speed 0:42:00
Increasing load factor increases the speed at which the wing reaches the critical angle of attack, so the aircraft stalls at a HIGHER airspeed.
A 45 degree bank raises stall speed by roughly 20 percent.
The danger case is low, slow and manoeuvring - an abrupt turn near landing can raise stall speed above your current airspeed and stall you with no height to recover.
The instructor notes this is a genuine killer in manned aviation, not just a model-aircraft nuisance.
Static and dynamic stability 0:45:56
Stability is the aircraft's tendency to return to its original flight path after a disturbance. STATIC stability is the INITIAL tendency; DYNAMIC stability is the behaviour OVER TIME.
Static - positive (starts back toward equilibrium), neutral (stays displaced), negative (diverges immediately).
Dynamic is described assuming positive static - positive dynamic converges, neutral dynamic oscillates forever at constant amplitude, negative dynamic oscillates with growing amplitude.
The PHAK's cup-on-a-table illustration is the standard mental model.
Center of gravity, arm and moment 0:50:14
The CG is the point at which the aircraft would balance. The ARM is the distance from the CG to where a force acts. The MOMENT is arm multiplied by force.
The door analogy - a handle far from the hinges (long arm) needs little force; a handle near the hinges (short arm) needs much more for the same moment.
Centre of pressure is where lift acts; centre of gravity is where weight acts. They are different points.
Forward vs aft CG and their trade-offs 0:54:23
CG is normally slightly FORWARD of the centre of lift, producing a nose-down moment balanced by a tail-down force from the horizontal stabiliser.
AFT CG - shorter arm, less tail-down force needed. Faster cruise, greater range, shorter takeoff, LOWER stall speed. But decreased stability, easier to over-control, harder stall recovery.
FORWARD CG - longer arm, more tail-down force. More stable, easier stall recovery. But slower cruise, reduced range, longer takeoff, HIGHER stall speed, harder to flare.
On a multirotor the CG should sit centrally between the motors; an offset CG makes two motors work harder and risks overheating them.
Payload must be SECURED. The instructor cites a C-130 crash from shifting cargo and a Matrice lost when an unsecured 360 camera shifted on takeoff.
Exceeding CG limits 1:03:02
The CG envelope is the range within which the aircraft remains controllable. Outside it, performance is unpredictable and control may be lost.
Too far FORWARD - nose-heavy, may never rotate off the ground.
Too far AFT - tail-heavy, may stall as soon as it becomes airborne.
On a multirotor, lift off slowly and watch for a tip - a badly loaded aircraft will dig its props in.
Factors that reduce performance 1:06:12
Performance falls with increasing ALTITUDE, TEMPERATURE, HUMIDITY and WEIGHT - all of which reduce the lift available or increase the lift required.
Higher altitude means lower pressure and thinner air, so each propeller revolution moves less air. The instructor describes a drone at 12,000 ft as "mushy" and slow to respond.
High temperature and high humidity both reduce performance; a hot humid day at sea level is the worst combination.
COLD hurts BATTERY endurance specifically, which is separate from motor performance.
Extra weight demands more lift, achieved through more speed or higher angle of attack, both of which add drag - longer takeoff, longer landing, reduced climb.
Manufacturer endurance figures come from ideal laboratory conditions; expect less.
Environmental factors at the launch site - surface type, slope, surface wind and obstacles. Launch from level ground; a tilted multirotor will dart sideways on liftoff.
They had a very controlled environment where they would get the maximum performance out of the drone, out of the battery - and then anything else that you do different than what they did in the lab, you're going to get different results.1:06:12
Using the testing supplement 1:15:35
The FAA supplies a printed testing supplement on exam day containing the figures and legends referenced by questions.
Practise on a COMPUTER, not a phone - exam day is a computer.
In the course quizzes a figure is one click away; on exam day you must FIND it in the book by figure number. Practise flipping to figures.
Appendix 1 holds legends, including the airspace legend - effectively a permitted cheat sheet.
The supplement is shared with private, sport and recreational pilot tests, so many figures will not apply to you. Do not panic at unfamiliar ones.
Figure numbers and page numbers differ; a magnifying glass is a legitimate aid for chart figures.
The instructor recommends not moving on until you score 80-85% on a section quiz.
Every concept, three clicks deep
The same concepts as a quick reference: the closed row is the glance, open is the study card, and every timestamp jumps into the recording.
01RPIC responsibility for loadingThe remote pilot in command must verify before flight that the aircraft is loaded properly - within the man…0:02:55›
The remote pilot in command must verify before flight that the aircraft is loaded properly - within the manufacturer's weight limits, with any payload secured, and positioned so the balance is not upset.
Loading must comply with the manufacturer's weight and balance specifications.
The governing documents are the Pilot's Operating Handbook or the UAS Flight Manual, depending on what the manufacturer calls it.
02Three axes of rotation and their controlsRoll about the longitudinal axis (ailerons), pitch about the lateral axis (elevator), and yaw about the ver…0:04:20›
Roll about the longitudinal axis (ailerons), pitch about the lateral axis (elevator), and yaw about the vertical axis (rudder).
The same three axes apply to a multirotor - right stick rolls and pitches, left stick yaws, throttle climbs and descends.
The instructor is explicit that airplane questions WILL appear on the exam because the certificate is not multirotor-specific.
03The four forces of flightLift opposes weight;0:07:35›
Lift opposes weight; thrust opposes drag. Lift acts at the CENTER OF PRESSURE (also called centre of lift); weight acts at the CENTER OF GRAVITY.
In straight-and-level unaccelerated flight lift equals weight AND thrust equals drag.
Thrust equal to drag does not mean stationary - it means CONSTANT speed. Thrust greater than drag means accelerating.
On a fixed wing, thrust comes from the propeller (itself an airfoil producing horizontal lift) along the longitudinal axis.
On a multirotor there is no separate thrust source - tilting the aircraft splits the rotor lift into a vertical component (opposing weight) and a horizontal component (thrust).
Weight always acts toward the centre of the earth.
04Airfoil terminology and angle of attackRelative wind is parallel to the flight path but opposite in direction.0:12:04›
Relative wind is parallel to the flight path but opposite in direction. The chord line runs from leading edge to trailing edge. The ANGLE OF ATTACK is the angle between the chord line and the relative wind.
Lift acts perpendicular to the RELATIVE WIND, not to the ground.
Lift is proportional to airspeed and to angle of attack - go faster or raise the angle of attack to make more lift.
The resultant force is lift and drag combined.
Angle of attack is NOT the same as pitch attitude - an aircraft can be nose-down and still at a high angle of attack.
05Newton's third law and Bernoulli's principleLift arises from two complementary effects - air deflected downward produces an equal and opposite upward r…0:17:16›
Lift arises from two complementary effects - air deflected downward produces an equal and opposite upward reaction (Newton), and faster airflow over the curved upper surface produces lower pressure than beneath (Bernoulli).
The hand-out-of-a-car-window analogy is Newton's third law in action.
Bernoulli - constricting flow raises speed and lowers pressure, like pinching a hose.
Higher pressure beneath moves toward lower pressure above, helping lift the wing.
06Parasite drag - form, interference, skin frictionDrag that is a byproduct of moving through the air.0:26:14›
Drag that is a byproduct of moving through the air. It INCREASES with airspeed.
FORM drag - the shape of the object.
INTERFERENCE drag - created where two components join; the whole is draggier than the sum of the parts measured separately.
SKIN FRICTION - rivets, chipped paint, insect strikes and other surface imperfections disturbing the airflow.
07Induced dragDrag generated as a byproduct of producing lift.0:29:28›
Drag generated as a byproduct of producing lift. It DECREASES as airspeed increases - the opposite of parasite drag.
The greater the angle of attack, the greater the induced drag.
High angle of attack generally means low airspeed, so induced drag dominates when slow.
On a multirotor induced drag appears once the aircraft moves laterally.
08Stalls and the critical angle of attackA stall occurs when the airfoil exceeds the CRITICAL ANGLE OF ATTACK and airflow separates from the upper s…0:32:28›
A stall occurs when the airfoil exceeds the CRITICAL ANGLE OF ATTACK and airflow separates from the upper surface, destroying lift. It concerns the WING, not the engine.
A wing stalls at the critical angle of attack REGARDLESS of airspeed, weight, attitude or CG position.
It is usually associated with low airspeed but can occur at high speed - for example an abrupt pull-up from a fast descent.
Recovery is to LOWER the angle of attack, which for a fixed wing means lowering the nose.
Multirotors do not stall in this sense - lift comes from powered rotors, not a fixed wing.
09Load factor and bank angleLoad factor is the ratio of the load the structure carries to the actual weight of the aircraft - the G force.0:36:51›
Load factor is the ratio of the load the structure carries to the actual weight of the aircraft - the G force. It increases with BANK ANGLE in a level turn.
30 degree bank = 1.154 G; 45 degrees = about 1.4; 60 degrees = 2.0 G; 80 degrees = about 5.7 G; 85 degrees = about 11.5 G. The curve is exponential.
At 60 degrees of bank a 10 lb aircraft imposes a 20 lb load on its structure.
Load factor rises in ANY manoeuvre other than straight-and-level - not only turns.
Exceeding the structural limit can fold or shed a wing.
10Load factor raises stall speedIncreasing load factor increases the speed at which the wing reaches the critical angle of attack, so the a…0:42:00›
Increasing load factor increases the speed at which the wing reaches the critical angle of attack, so the aircraft stalls at a HIGHER airspeed.
A 45 degree bank raises stall speed by roughly 20 percent.
The danger case is low, slow and manoeuvring - an abrupt turn near landing can raise stall speed above your current airspeed and stall you with no height to recover.
The instructor notes this is a genuine killer in manned aviation, not just a model-aircraft nuisance.
11Static and dynamic stabilityStability is the aircraft's tendency to return to its original flight path after a disturbance.0:45:56›
Stability is the aircraft's tendency to return to its original flight path after a disturbance. STATIC stability is the INITIAL tendency; DYNAMIC stability is the behaviour OVER TIME.
Static - positive (starts back toward equilibrium), neutral (stays displaced), negative (diverges immediately).
Dynamic is described assuming positive static - positive dynamic converges, neutral dynamic oscillates forever at constant amplitude, negative dynamic oscillates with growing amplitude.
The PHAK's cup-on-a-table illustration is the standard mental model.
12Center of gravity, arm and momentThe CG is the point at which the aircraft would balance.0:50:14›
The CG is the point at which the aircraft would balance. The ARM is the distance from the CG to where a force acts. The MOMENT is arm multiplied by force.
The door analogy - a handle far from the hinges (long arm) needs little force; a handle near the hinges (short arm) needs much more for the same moment.
Centre of pressure is where lift acts; centre of gravity is where weight acts. They are different points.
13Forward vs aft CG and their trade-offsCG is normally slightly FORWARD of the centre of lift, producing a nose-down moment balanced by a tail-down…0:54:23›
CG is normally slightly FORWARD of the centre of lift, producing a nose-down moment balanced by a tail-down force from the horizontal stabiliser.
AFT CG - shorter arm, less tail-down force needed. Faster cruise, greater range, shorter takeoff, LOWER stall speed. But decreased stability, easier to over-control, harder stall recovery.
FORWARD CG - longer arm, more tail-down force. More stable, easier stall recovery. But slower cruise, reduced range, longer takeoff, HIGHER stall speed, harder to flare.
On a multirotor the CG should sit centrally between the motors; an offset CG makes two motors work harder and risks overheating them.
Payload must be SECURED. The instructor cites a C-130 crash from shifting cargo and a Matrice lost when an unsecured 360 camera shifted on takeoff.
14Exceeding CG limitsThe CG envelope is the range within which the aircraft remains controllable.1:03:02›
The CG envelope is the range within which the aircraft remains controllable. Outside it, performance is unpredictable and control may be lost.
Too far FORWARD - nose-heavy, may never rotate off the ground.
Too far AFT - tail-heavy, may stall as soon as it becomes airborne.
On a multirotor, lift off slowly and watch for a tip - a badly loaded aircraft will dig its props in.
15Factors that reduce performancePerformance falls with increasing ALTITUDE, TEMPERATURE, HUMIDITY and WEIGHT - all of which reduce the lift…1:06:12›
Performance falls with increasing ALTITUDE, TEMPERATURE, HUMIDITY and WEIGHT - all of which reduce the lift available or increase the lift required.
Higher altitude means lower pressure and thinner air, so each propeller revolution moves less air. The instructor describes a drone at 12,000 ft as "mushy" and slow to respond.
High temperature and high humidity both reduce performance; a hot humid day at sea level is the worst combination.
COLD hurts BATTERY endurance specifically, which is separate from motor performance.
Extra weight demands more lift, achieved through more speed or higher angle of attack, both of which add drag - longer takeoff, longer landing, reduced climb.
Manufacturer endurance figures come from ideal laboratory conditions; expect less.
Environmental factors at the launch site - surface type, slope, surface wind and obstacles. Launch from level ground; a tilted multirotor will dart sideways on liftoff.
16Using the testing supplementThe FAA supplies a printed testing supplement on exam day containing the figures and legends referenced by…1:15:35›
The FAA supplies a printed testing supplement on exam day containing the figures and legends referenced by questions.
Practise on a COMPUTER, not a phone - exam day is a computer.
In the course quizzes a figure is one click away; on exam day you must FIND it in the book by figure number. Practise flipping to figures.
Appendix 1 holds legends, including the airspace legend - effectively a permitted cheat sheet.
The supplement is shared with private, sport and recreational pilot tests, so many figures will not apply to you. Do not panic at unfamiliar ones.
Figure numbers and page numbers differ; a magnifying glass is a legitimate aid for chart figures.
The instructor recommends not moving on until you score 80-85% on a section quiz.
Tools referenced
| Tool | Coverage | Moment | Context |
|---|---|---|---|
| Pilot's Handbook of Aeronautical Knowledge (PHAK) | mentioned | 0:00:00 | Chapters 4 and 5 for loading, performance and aerodynamics. The instructor calls it the single most important reference in the course. |
| FAA-H-8083-22 Remote Pilot Study Guide | mentioned | 0:00:00 | Chapter 4 covers this material in condensed form. |
| Airman Certification Standards (ACS) | mentioned | 0:00:00 | Defines the task list this section is built to satisfy. |
| FAA Testing Supplement | mentioned | 0:00:00 | Figures and legends provided on exam day; buy or download and practise with it. |
Session materials
Archived locally on V: — click to open. Companion pages link to the LMS.
Action items
Resources mentioned
Extraction notes
This page was built from an auto-generated transcript, which garbles product and people's names. Those were corrected silently in everything above and logged here for transparency. The warnings flag claims that were true on the recording day but change fast.
Transcript corrections applied
| The transcript says | The trainer actually means |
|---|---|
| FA / EFA | FAA |
| p-hack / PHAC | PHAK (Pilot's Handbook of Aeronautical Knowledge) |
| APS | ACS (Airman Certification Standards) |
| fixed swing | fixed wing |
| trailing X | trailing edge |
| construction pipe / construction point | constriction (in the Bernoulli explanation) |
| my radar | my radio (the RC transmitter) |
| solo cup | correct as heard - the PHAK stability analogy |
| the airplane is 33 pounds ... wingspan is 38 pounds | garbled question read-back; the load factor example is 33 lb at 30 deg bank giving about 38 lb of supported weight |
| 2 for appendix 2 and then 56 for page 56 | figure numbering convention in the testing supplement |
True on recording day — verify before relying
- Mavic 2 endurance figures (32 min claimed, 25-27 min achieved). - STATUS: POINT-IN-TIME product detail. The teaching point - manufacturer figures are laboratory best-case - is stable.
- Load factor and stall-speed percentage figures. - STATUS: STABLE physics, unchanged.
- Testing supplement structure and figure numbering. - STATUS: Verify against the CURRENT FAA testing supplement; appendix and figure numbers are revised periodically.