Mass & Balance in Aviation
MASS & BALANCE PERFORMANCE
Prepared for: Singapore Polytechnic School of Mechanical and Aeronautical Engineering
CONTENT DETAILS
MASS & BALANCE
Introduction
Definitions & Terminology
Effects of Mass on Flight
Effects of Balance on Flight
PERFORMANCE
Introduction
Definitions & Terminology
MASS & BALANCE
Introduction
Mass and balance are crucial aspects in aviation.
The safety and efficiency of an aircraft are highly dependent on the loading and balance of the aircraft.
Definitions & Terminology
MASS:
Definition: The quantity of matter in a body.
SI Unit: kg
WEIGHT:
Definition: The force produced when a mass is subjected to gravity.
SI Unit: N
GRAVITY:
Definition: The force that attracts a body towards the center of the Earth, or towards any other physical body having mass.
SI Unit: m/s²
BALANCE:
Definition: An even distribution of weight.
Center of Gravity (C.G)
Definition: The center of gravity is the average location of the weight of an object.
It is a geometric property of any object.
Every aircraft has a front and rear limit.
Additional Definitions
Datum: A fixed point of reference for the aircraft to measure moment arms.
Balance Arm: The distance between a mass from the datum; distances can be before (-ve) or after (+ve) the datum.
Moment Arm: A rotational effect around the datum generated by a mass.
Example Calculation
Given:
Moment Calculation:
Additional Mass Definitions
Basic Empty Mass:
The mass of an aeroplane including unusable fuel, other fluids, lubrication oil, fire extinguishers, pyrotechnics, oxygen equipment, and electronics.
Represents the empty aircraft as it comes from the hangar (no fuel, nobody inside, no payload).
Dry Operating Mass:
Basic empty weight + Crew + Crew luggage + Special equipment.
Reference weight used to calculate C.G and mass; aircraft with crew, no payload and fuel.
Operating Mass:
Basic empty weight + Crew + Crew luggage + Special equipment + Fuel.
Represents a joyride plane with crew and fuel, but no payload.
Traffic Load (Payload):
Passengers, baggage, cargo of any kind.
Zero Fuel Mass:
Basic empty weight + Crew + Crew luggage + Special equipment + Traffic load/payload.
Maximum Zero Fuel Mass:
The maximum allowed zero fuel mass due to structural limitations, including wing root bending limits from the C.G and main gears.
Taxi Mass:
Mass of the entire aircraft before it sorties from the gate/apron, calculated as zero fuel mass + mission fuel.
Maximum Structural Taxi Mass:
The heaviest taxi mass allowable by the manufacturer of the aircraft, considering structural limits and weight on wheels vs pavement strength.
Take-Off Mass:
The mass of the entire aircraft during take-off rotation.
Maximum Structural Take-Off Mass:
The heaviest take-off mass allowable by the manufacturer, considering structural limits and various performance metrics.
Landing Mass:
Mass of the aircraft upon touchdown; includes zero fuel mass and remaining flight fuel.
It is critical for every aircraft to land with a minimum of final reserve fuel tanks, which if not achievable will cause the pilot to declare emergency status.
Maximum Structural Landing Mass:
The heaviest landing mass allowable; also considers stopping distance and conditions affecting landing performance.
EFFECTS OF MASS ON FLIGHT
Increase in Mass will result in:
Higher fuel burn throughout the flight.
Higher inflight drag.
Longer take-off distance required.
Longer landing distance required.
Poorer climb performance.
Poorer glide endurance (glide range not affected by mass).
Poorer range and endurance of flight.
Lower maximum and optimal cruise altitude.
Higher stall speeds.
Poorer maneuverability.
Increased tire and brake wear.
Increased structural stress and fatigue.
Decrease in Mass will result in:
Lower fuel burn throughout the flight.
Lower inflight drag.
Shorter take-off distance required.
Shorter landing distance required.
Better climb performance.
Better glide endurance (glide range not affected by mass).
Better range and endurance of flight.
Higher maximum and optimal cruise altitude.
Lower stall speeds.
Better maneuverability.
Decreased tire and brake wear.
Decreased structural stress and fatigue.
EFFECTS OF BALANCE ON FLIGHT
Optimal C.G Configuration
Leads to:
Lower fuel burn throughout the flight.
Lower inflight trim drag.
Better range and endurance of flight.
Optimal stall and maneuverability stability.
Moving the C.G Forward of Optimal
Effects:
Increased fuel burn throughout the flight.
Higher inflight trim drag.
Reduced range and endurance of flight.
Increased stall speed.
Increased maneuverability stability.
Increased take-off run required.
Moving the C.G Rear of Optimal
Effects:
Increased fuel burn throughout the flight.
Higher inflight profile drag.
Reduced range and endurance of flight.
Increased stall speed.
Decreased maneuverability stability.
Aircraft becomes more responsive to controls.
Flight stability may be compromised.
More susceptible to negative stall characteristics (e.g., tail-slide, spins, flat-spins).
PERFORMANCE
Introduction
Performance encompasses the study of an aircraft’s ability to conduct maneuvers such as climbing, cruising, descending, etc.
Data, such as climb performance, is crucial, especially in aerodromes surrounded by high terrain.
Phases of Flight
Take-Off
Climb
Cruise
Descend
Landing
TAKE-OFF PHASE
Take-Off Definition
Defined as the sequence from the application of takeoff power through rotation to an altitude of 35 feet above runway elevation or until gear-up selection, whichever occurs first.
Rejected Take-off
Defined as the period during takeoff, from the point a decision to abort has been made until the aircraft begins to taxi out or comes to a complete stop.
The decision to reject/abort take-off must occur before V1.
Take-Off Distances
TORA (Take Off Run Available):
Amount of runway available for which an aircraft's gear can be in contact during the takeoff run.
ASDA (Accelerate Stop Distance Available):
The amount of runway available for an aircraft to accelerate to V1, reject take-off, and come to a complete stop without damage to the aircraft or runway.
TODA (Take Off Distance Available):
Distance from the start of applying take-off power until the aircraft is 35 feet above airport elevation.
Additional Distance Definitions
TORR (Take Off Run Required):
The runway required for aircraft to reach V1-lift off from stationary.
TODA and ASDA Calculations: Can be assessed with environmental factors affecting runway conditions.
V Speeds for Take-off
VMCG (Velocity Minimum Control Ground):
Minimum speed for controllability with the critical engine inoperative on the ground.
V1:
Maximum speed where take-off can safely be rejected.
VMCA (Velocity Minimum Control Air):
Minimum speed for controllability with the critical engine inoperative in the air.
VMU (Velocity Minimum Unstick):
Minimum speed to safely lift off; below this, the aircraft may drag its tail.
VR (Velocity Rotate):
Speed at which the pilot can initiate a nose pitch up.
VLOF (Velocity Lift Off):
Speed when the aircraft fully lifts off the ground.
V2:
Takeoff safety speed; minimum speed for a safe climb with one engine inoperative.
Factors Increasing Take-Off Distance
Aircraft Factors:
Increase in total mass or weight, lower take-off flap settings, flapless takeoff, thrust de-rated take-off.
Runway Factors:
Uphill runway, high elevation, wet/snow/grass/contaminated runway.
Environmental Factors:
Decrease in air density, increase in ambient temperature, decrease in ambient pressure, increase in ambient humidity, tailwind.
CLIMB PHASE
Climb Definition
For an aircraft to gain altitude.
Climb Terms
Maximum Altitude: Highest altitude the aircraft can reach in its current configuration.
Optimum Altitude: Recommended altitude for best cruise performance.
Service Ceiling: Height where aircraft can no longer climb faster than 100 feet per minute under standard conditions.
Best Angle of Climb (Vx): The climb performance that provides the best angle of trajectory; requires maximum excess thrust available.
Best Rate of Climb (Vy): The climb performance providing the best sustained climb rate; requires maximum excess power available.
Econ Climb: Climb performance balancing fuel burn and altitude gain.
Factors Affecting Climb
Increases Rate/Angle of Climb
Decrease in mass of aircraft.
Increase in engine power/thrust.
Decrease in aircraft total drag.
Clean aircraft configuration.
Increase in air density, pressure, and lower altitudes.
Decreases Rate/Angle of Climb
Increase in mass of aircraft.
Decrease in engine power/thrust.
Increase in total drag (flaps, gears).
Head wind or tail wind effects on performance.
CRUISE PHASE
Cruise Definition
Aircraft moving at a constant altitude at economy speed.
Cruise Terms
Top Of Climb (TOD): The point where the aircraft levels off after climbing.
Vmo (Velocity Maximum Operation): The maximum indicated airspeed rated structurally.
MMo (Mach Maximum Operation): The maximum mach number the aircraft is rated to prevent local airflow over parts from going supersonic.
Vne (Velocity Never Exceed): Any operation at this speed or higher can result in structural damage.
VBE (Velocity Best Endurance): Speed to remain airborne the longest.
VBR (Velocity Best Range): Speed to achieve the furthest range.
DESCEND PHASE
Descend Definition
Flight with minimal engine thrust is called gliding.
Glide Performance
Glide range depends solely on maximum lift/drag ratio.
Glide endurance focuses on the velocity minimum power of the aircraft.
APPROACH PHASE
Approach Definition
The phase where the aircraft is descending on the glideslope to line up for the runway until 50 feet above the threshold.
Approach Terms
Localizer: Instrument aid for horizontal alignment to the runway.
Glideslope: Instrument aid for vertical descent alignment to the runway.
VREF (Velocity Reference): Speed calculated to buffer the stall speed of the landing configuration.
LANDING PHASE
Landing Definition
The process of terminating flight on the runway, starting from 50 feet above the threshold until exiting the runway or coming to a complete stop.
Landing Terms
Touch Down Point/Marker: Expected point of aircraft touchdown, marked by solid white bars 1500 feet from the threshold.
LDR (Landing Distance Required): The distance needed to come to a stop or safely exit the runway.
LDA (Landing Distance Available): The distance available on the runway.
REFERENCES
CAE ATPL (CAA) Textbook
CAE ATPL (CAA) Computer Based Training Slides
ICAO Reference Materials
FAA Reference Materials
Google Image Search
END OF CONTENT
Thank you
Prepared for Singapore Polytechnic School of Mechanical and Aeronautical Engineering