7.16 Aircraft Weight and Balance Flashcards
What factors determine the maximum allowable weight of an aircraft?
The maximum allowable weight is based on the surface area, the shape of the wings, and how much lift the wings generate at a safe airspeed.
Why is take-off speed important for aircraft safety?
A small light aircraft requiring a take-off speed of about 320 kilometres per hour (200 miles per hour) to generate enough lift to support its weight would not be deemed safe.
What is the significance of an aircraft’s balance?
An aircraft’s balance is significant for safe operation; poor balance can lead to poor manoeuvrability and controllability, increasing the risk of accidents.
How does improper loading affect aircraft efficiency?
Improper loading reduces efficiency, affecting manoeuvrability, rate of climb, speed, and fuel consumption.
What happens if an aircraft is nose heavy?
If an aircraft is nose heavy, higher forces must be exerted at the tail to maintain level flight, creating additional drag and requiring more engine power and fuel.
What is the most efficient condition for an aircraft’s balance?
The most efficient condition is when the aircraft balances at its centre of lift, requiring little or no flight control force to maintain straight and level flight.
What must be included in an aircraft’s weight and balance report?
The report must include the empty weight of the aircraft and the location of the Centre of Gravity (CG).
What is the manufacturer’s responsibility regarding aircraft weight?
The manufacturer must weigh each aircraft produced and issue a weight and balance report based on that specific aircraft.
What is the regulation regarding the percentage of aircraft that must be weighed?
Manufacturers are permitted to weigh only an agreed percentage (10% to 20%) of any particular model and apply the average to the aircraft as a whole.
What triggers the need for an aircraft to be reweighed?
Reweighing may be required for small light aircraft periodically, especially if the weight and balance report is lost or if new equipment is installed.
What are the consequences of an overloaded aircraft?
An overloaded aircraft may require a higher take-off speed, have reduced climb rate, lower service ceiling, decreased cruising speed, and longer landing roll.
What is the purpose of the flight crew operating handbook?
The handbook includes tables or charts that indicate the expected performance for any given weight, aiding in pre-flight planning.
What is a datum line in aircraft weight and balance?
The datum line is a reference point from which the arm of an aircraft’s components is measured.
What is an arm in the context of aircraft weight and balance?
The arm is the horizontal distance from the datum to a part of the aircraft, measured in inches, with positive or negative signs indicating its location relative to the datum.
What is a moment in aircraft weight and balance?
A moment is the product of weight multiplied by its arm, measured in inch-pounds or newton metres.
What is the Centre of Gravity (CG) in an aircraft?
The CG is the point along the aircraft’s longitudinal axis where its weight is concentrated and must be within specific limits for safe flight.
What happens if the CG is too far aft?
If the CG is too far aft, the aircraft becomes unstable and difficult to recover in the event of a stall.
What happens if the CG is too far forward?
If the CG is too far forward, it increases the downward tail load needed to maintain level flight, effectively adding weight.
What happens if the Centre of Gravity (CG) is too far aft?
The aircraft becomes unstable and difficult to recover in the event of a stall. If it enters a spin, recovery is extremely difficult or even impossible.
What is the effect of a forward Centre of Gravity (CG)?
It increases the downward tail load to maintain level flight, causing the aircraft to fly at a higher angle of attack and increasing drag.
What serious problem can occur with a forward CG during take-off and landing?
There may not be enough elevator authority to provide sufficient nose-up force to rotate during take-off and to flare the aircraft during landing.
How does lateral symmetry affect aircraft balance?
The basic design assumes equal weight on both sides of the aircraft’s centerline, but uneven fuel loading can upset this balance.
How can a pilot correct a laterally unbalanced condition?
By using the aileron trim tab until enough fuel has been used from the heavy side to balance the aircraft.
What is the consequence of using aileron trim tabs?
They produce additional lift on the heavy side but also increase drag, causing the aircraft to fly inefficiently.
Why is fuel scheduling critical in swept wing aircraft?
Fuel imbalances as fuel is used from outboard and inboard tanks can move the CG forwards or aft, affecting stability.
How is the Centre of Gravity (CG) typically expressed?
In inches or millimeters from a predetermined reference point called the ‘datum’.
What is the CG range?
The distance between the allowable limits for the CG, where the aircraft is considered to be in balance.
What is the responsibility of the aircraft engineer regarding CG?
To ensure that any repair or alteration does not shift the aircraft’s CG beyond its limits.
What are the steps to determine the CG of a beam?
- Measure the arm of each weight from the datum. 2. Multiply each arm length by its weight to find the moment. 3. Total all weights and moments. 4. Divide total moment by total weight.
What is the Mean Aerodynamic Chord (MAC)?
The chord drawn through the geographic center of the plan area of the wing, used to express the CG position.
How is the allowable CG range expressed?
In percentages of the MAC, which is the chord of an imaginary aerofoil with the same aerodynamic characteristics as the actual aerofoil.
What is the significance of the CG’s position relative to the aerodynamic centre of lift?
The CG must be located ahead of the centre of lift for longitudinal stability.
What is the Maximum Ramp Weight?
The maximum weight approved for ground maneuvers, including start, taxi, and engine run-up fuel.
What is the Maximum Zero Fuel Weight?
The approved maximum weight of an aircraft without fuel, including the aircraft and everything carried on the flight.
What is the procedure for determining passenger mass?
Use actual passenger mass and add a predetermined mass for hand baggage and clothing, which must not be less than specified minimums.
What is the Type Certificate Data Sheet (TCDS)?
A document that contains a formal description of the aircraft, including specifications and weight and balance information.
What is the responsibility of the inspecting aircraft engineer regarding TCDS?
To ensure that the aircraft adheres to the TCDS before beginning any weighing or balancing procedures.
What must be done before weighing an aircraft?
The aircraft must be prepared according to the conditions detailed in the Aircraft Maintenance Manual Chapter 8 for the specific aircraft being weighed.
What does Chapter 8 of the Aircraft Maintenance Manual provide?
It provides the steps to prepare the aircraft, find the operating empty weight, and calculate the Centre of Gravity (CG).
What is the ideal environment for weighing an aircraft?
Inside a closed hangar on a level floor, allowing the aircraft to acclimatise for several hours.
How should the aircraft be positioned for weighing?
The aircraft must be placed in the rigged or jigged position with the longitudinal axis parallel to the floor.
What care must be taken when using plumb bobs for measurements?
Particular care must be exercised to ensure accurate readings.
What is a consideration for small, light aircraft with tail-wheel landing gear?
They may have a negative load on the tail when in the rigged position due to the CG being forward of the main wheel axles.
How should a negative load on the tail be managed?
A spring balance must be anchored to the ground and attached to the tail wheel axle to determine the extent of the negative reaction.
What must be added to the spring balance reading?
The weight of the spring balance and any rope used to secure it to the aircraft.
What must be done to the fuselage and airframe structure before weighing?
They must be thoroughly cleaned to avoid discrepancies in weight.
What happens to aircraft weight as they age?
Aircraft tend to become heavier due to the accumulation of dirt and added items.
What conditions must be met to determine an aircraft’s empty weight?
The aircraft must be weighed with no fuel, only residual fuel, or with full fuel tanks.
What should never be done when weighing an aircraft?
Never weigh an aircraft with the fuel tanks partially full.
What is included in the empty weight for aircraft certified since 1978?
The full engine oil quantity is included.
What must be done if only residual oil is part of the empty weight?
Drain the engine oil system to leave only residual oil or check and subtract the weight of the oil to leave the residual amount.
What must be done to hydraulic reservoirs and systems before weighing?
They must be filled, while drinking water and lavatory tanks must be drained.
How must an aircraft be positioned when weighed?
It must be in its level flight attitude, as determined by the Type Certificate Data Sheet (TCDS).
What methods can be used to ensure an aircraft is level?
A plumb line, spirit level across levelling lugs, or spirit level on the upper door sill.
What is the purpose of stress plates under jack pads?
They are installed if specified by the manufacturer to distribute weight and prevent damage.
What must be done if anyone is in the aircraft while it is being jacked?
There must be no movement.
What is the function of electronic load cells in larger aircraft?
They allow the aircraft to weigh itself while sitting on the ground.
What must be adhered to when calculating a weight and balance record?
Certain procedures must be followed to ensure accuracy, including understanding weight and balance terminology.
What documents provide information for weight and balance changes?
Type Certificate Data Sheet (TCDS), Aircraft Operating Limitations, Aircraft Operation Manual (AOM), and others.
What does not require a weight and balance check?
The removal or addition of minor items of negligible weight.
What requires a weighing procedure?
The removal or addition of major parts or equipment that change the CG.
Where should an aircraft be weighed?
It is recommended to weigh an aircraft inside a closed hangar.
What conditions should be met before weighing an aircraft?
The aircraft must assume an even temperature and be free from moisture.
What is required for outdoor weighing of an aircraft?
It must be on firm and level ground with minimal wind force, and the aircraft must be completely dry and free from frost or dew.
Why is weighing an aircraft critical?
Weighing is a critical phase of aircraft maintenance that must be carried out with precision and skill.
What must be done to precision measurement equipment before weighing?
All precision measurement equipment must be inspected and calibrated.
What equipment is necessary for weighing an aircraft?
Scales, hoisting equipment, jacks, levelling equipment, blocks, chocks, sandbags, straightedge, spirit level, plumb bobs, chalk line, and measuring tape.
What are the three types of scales used to weigh an aircraft?
Beam scales, platform scales (mechanical & electronic), and load cells (electronic).
How do beam scales work?
A bar rises when weight is applied, and a sliding weight is moved until the bar is centred.
What is the limitation of mechanical platform scales?
They are limited to small and light aircraft due to their accuracy.
What is the preferred method for weighing large aircraft?
The electronic platform scale, which allows the aircraft to be towed or rolled onto the scales.
How does a load cell function?
It experiences a change in electrical resistance as weight is applied, sending a signal to a display unit.
How many times is an aircraft usually weighed?
The aircraft is usually weighed three times for accuracy.
What is the advantage of using load cells on jacks?
It allows the engineer to easily level the aircraft.
How is a spirit level used in weighing an aircraft?
It indicates a level condition when the air bubble is centred between two black lines.
What is a plumb bob used for?
It helps determine the attitude of the aircraft by hanging down from a specified point.
What must be checked after weighing calculations?
The readings must be compared with the weight and centre of gravity schedule and the Type Certificate Data Sheet (TCDS).
What should be done if weight readings are outside limits?
The aircraft must be checked again, discrepancies rectified, and it must be re-weighed.
What is required before re-weighing an aircraft that failed the weight check?
The aircraft must be re-cleaned and allowed time to dry completely.
