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NCAA PPL Flight Performance & Planning study materials
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NCAA PPL Flight Performance & Planning practice questions

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Question 1Mass and Balance

In light-aircraft mass and balance, what does the term 'empty weight' normally include?

  1. Airframe and engine only, excluding avionics and interior
  2. Airframe, engine and fixed equipment only, with all fluids drained
  3. Airframe, engine, fixed equipment and usable fuel to the tabs
  4. Airframe, engine, fixed equipment, unusable fuel and full oil Correct answer.

Explanation

Empty weight is the basic weight of the aircraft plus fixed equipment, and it includes unusable fuel and full oil, because those quantities are not available for flight planning. Usable fuel, payload and crew are added later to obtain the takeoff weight.

Question 2Mass and Balance

Which of the following is classified as useful load?

  1. The basic airframe and engine weight
  2. The empty-weight figure recorded in the aircraft logbook
  3. Pilot, passengers, baggage and usable fuel Correct answer.
  4. Unusable fuel trapped in the fuel system

Explanation

Useful load is the difference between maximum certificated takeoff weight and empty weight, so it covers everything the aircraft may carry: crew, passengers, baggage, usable fuel and cargo. Unusable fuel and basic structure are already inside empty weight.

Question 3Mass and Balance

Where is the datum located on most light aircraft for mass and balance purposes?

  1. At an arbitrary reference point chosen by the manufacturer Correct answer.
  2. At the centre of gravity at maximum takeoff weight
  3. At the firewall in every case
  4. At the nose of the aircraft

Explanation

The datum is an arbitrary vertical reference plane selected by the manufacturer, from which all arm measurements are taken. It may lie at the firewall, at the nose, ahead of the propeller or elsewhere, so it cannot be assumed to be a fixed structural point.

Question 4Mass and Balance

What is the 'arm' of an item in a light-aircraft weighing schedule?

  1. The weight of the item multiplied by its distance from the datum
  2. The horizontal distance from the datum to the item's centre of gravity Correct answer.
  3. The vertical distance from the cabin floor to the item
  4. The maximum load permitted at that station

Explanation

The arm is the horizontal distance measured from the datum to the centre of gravity of the item or station. Multiplying the arm by the item's weight gives its moment, which is the quantity summed to find the aircraft CG.

Question 5Mass and Balance

What are the units of a moment in the mass and balance calculation?

  1. Kilograms
  2. Kilogram-metres Correct answer.
  3. Newton-metres per second
  4. Metres

Explanation

A moment is the product of a weight (or mass) and an arm, so its units are kilogram-metres when working in mass units. Moments are summed and then divided by total mass to obtain the CG position.

Question 6Mass and Balance

An aircraft has a maximum takeoff mass of 1,100 kg and an empty mass of 700 kg. What is its useful load?

  1. 1,800 kg
  2. 400 kg Correct answer.
  3. 1,100 kg
  4. 700 kg

Explanation

Useful load is maximum takeoff mass minus empty mass, that is 1,100 kg minus 700 kg, giving 400 kg. This is the total available for crew, passengers, baggage and usable fuel.

Question 7Mass and Balance

If the centre of gravity moves aft within the permitted range, how does this generally affect the aircraft in flight?

  1. The aircraft becomes more resistant to spinning
  2. Longitudinal stability decreases and stall recovery becomes more difficult Correct answer.
  3. Stall speed increases and pitch stability improves
  4. Elevator effectiveness is reduced in the flare

Explanation

An aft CG shortens the distance between the CG and the tail, reducing the restoring moment and therefore longitudinal stability. It also reduces the stick force needed to hold the nose up and can make stall and spin recovery more difficult.

Question 8Mass and Balance

Why must the centre of gravity remain forward of the aft limit during landing?

  1. To keep the nosewheel from lifting during the flare
  2. To reduce the landing distance over the threshold
  3. To ensure the aircraft can be rotated for takeoff at low speed
  4. To keep the aircraft controllable and avoid an excessive landing attitude Correct answer.

Explanation

A CG beyond the aft limit can leave insufficient elevator authority to flare and hold the correct landing attitude, and may allow the tail to strike. The aft limit exists to preserve pitch control and stability throughout the landing.

Question 9Mass and Balance

An item of 40 kg is loaded at a station 1.5 m aft of the datum. What moment does it contribute?

  1. 600 kg-m
  2. 26.7 kg-m
  3. 41.5 kg-m
  4. 60 kg-m Correct answer.

Explanation

Moment equals weight multiplied by arm, so 40 kg times 1.5 m gives 60 kg-m. This value is added to the other moments before dividing by total mass to find the CG.

Question 10Mass and Balance

Total mass is 900 kg with a total moment of 1,800 kg-m. Where is the centre of gravity relative to the datum?

  1. 0.5 m
  2. 20 m
  3. 1,800 m
  4. 2.0 m Correct answer.

Explanation

CG position is total moment divided by total mass, so 1,800 kg-m divided by 900 kg equals 2.0 m aft of the datum. This value is then checked against the forward and aft CG limits.

Question 11Mass and Balance

A pilot adds 50 kg of baggage at an arm of 2.4 m and 30 kg of baggage at an arm of 1.2 m. What is the combined moment of the two items?

  1. 156 kg-m Correct answer.
  2. 120 kg-m
  3. 192 kg-m
  4. 80 kg-m

Explanation

The first item contributes 50 times 2.4, which is 120 kg-m, and the second contributes 30 times 1.2, which is 36 kg-m. Summing these gives a combined moment of 156 kg-m.

Question 12Mass and Balance

When shifting a load within the aircraft, what happens to the total weight and the total moment?

  1. Total weight changes and the total moment stays the same
  2. Both total weight and total moment change
  3. Neither total weight nor total moment changes
  4. Total weight stays the same and the total moment changes Correct answer.

Explanation

Moving a load does not alter the total weight, but the arm of that load changes, so its moment changes and the aircraft CG shifts. The direction of the shift depends on whether the load moves forward or aft.

Question 13Mass and Balance

A load of 60 kg is moved aft by 0.5 m in an aircraft of total mass 1,000 kg. By how much does the CG move?

  1. 0.03 m aft Correct answer.
  2. 0.50 m aft
  3. 0.30 m aft
  4. 3.00 m aft

Explanation

The CG shift equals the weight shifted times the distance moved, divided by total weight: 60 times 0.5 divided by 1,000 gives 0.03 m aft. The small shift reflects that the moved load is a modest fraction of the total mass.

Question 14Mass and Balance

An aircraft has a maximum zero-fuel mass limit. What does this limit protect?

  1. The engine mounts from torsional vibration
  2. The landing gear from high sink rates
  3. The wing spar from excessive bending at maximum fuel
  4. The structure from the combined effect of payload without the relief of fuel weight Correct answer.

Explanation

Maximum zero-fuel mass is the maximum mass permitted with usable fuel excluded, so it limits the load carried in the fuselage and wings without the bending relief that fuel in the wings provides. It is a structural limit independent of total fuel aboard.

Question 15Mass and Balance

During pre-flight planning, the calculated takeoff mass exceeds the maximum takeoff mass but the CG is within limits. What is the correct action?

  1. Record the excess in the technical log and depart
  2. Reduce fuel or payload until the mass is within the limit Correct answer.
  3. Increase the takeoff speed to compensate
  4. Depart, because the CG is within limits

Explanation

Maximum takeoff mass is a structural and performance limit that may not be exceeded, regardless of CG position. The pilot must reduce fuel or payload, or both, until the mass is at or below the limit before departure.

Question 16Mass and Balance

An aircraft has a forward CG limit of 0.90 m and an aft limit of 1.20 m from the datum. The calculated CG is 1.25 m. What does this indicate?

  1. The CG is forward of the forward limit
  2. The datum is incorrectly placed
  3. The CG is within limits and no action is needed
  4. The CG is aft of the aft limit and must be corrected Correct answer.

Explanation

A CG of 1.25 m lies beyond the aft limit of 1.20 m, so the loading is outside the permitted envelope. The pilot must move or remove load to bring the CG forward within the range before flight.

Question 17Mass and Balance

What is the effect of a forward CG on takeoff performance?

  1. Landing distance is unaffected in all cases
  2. Rotation becomes easier and the takeoff run shortens
  3. Rotation requires more elevator force and the takeoff run may increase Correct answer.
  4. Stall speed decreases and climb performance improves

Explanation

A forward CG increases the download on the tailplane, so greater elevator force and a longer takeoff run are needed to rotate. The higher stall speed associated with a forward CG also affects performance.

Question 18Mass and Balance

A pilot uses the loading graph and finds the CG at the forward limit with full fuel. Fuel is then burned in flight. What is the likely trend of the CG?

  1. It moves forward, because fuel is removed from aft tanks only
  2. It remains exactly constant throughout the flight
  3. It moves aft, because fuel is removed from a tank forward of the CG Correct answer.
  4. It moves to the aft limit immediately after takeoff

Explanation

If the fuel tank is located forward of the CG, burning fuel removes weight ahead of the CG and the CG moves aft. The pilot must ensure the CG remains within limits at the planned landing mass, not just at takeoff.

Question 19Mass and Balance

In a mass and balance calculation, which item is normally entered with a negative arm or a moment ahead of the datum?

  1. Fuel in the wing tanks
  2. The pilot seated forward of the datum
  3. An item located ahead of the datum, such as a nose-mounted battery Correct answer.
  4. Baggage in the rear hold

Explanation

Items located ahead of the datum have arms measured in the negative direction, so their moments are subtracted when summing. The datum's arbitrary location means some equipment can lie on the forward side of it.

Question 20Mass and Balance

An aircraft has a maximum takeoff mass of 1,150 kg and a maximum landing mass of 1,050 kg. It takes off at 1,120 kg. What is the maximum fuel that may be burned before landing without exceeding the landing limit?

  1. 70 kg Correct answer.
  2. 100 kg
  3. At least 0 kg, because the landing mass is already below the limit
  4. 1,050 kg

Explanation

The takeoff mass exceeds the maximum landing mass by 1,120 minus 1,050, which is 70 kg, so at least 70 kg of fuel must be burned before landing. This ensures the landing mass does not exceed its limit even though the takeoff mass was legal.

Question 21Mass and Balance

A pilot must carry a fixed payload and has a choice of fuel load. The CG with full fuel is at the forward limit. Which loading strategy best preserves an acceptable CG at landing?

  1. Reduce fuel and move some baggage aft to keep the CG within limits at landing Correct answer.
  2. Take full fuel and accept that the CG will move aft during the flight
  3. Take full fuel and move baggage forward to compensate
  4. Take minimum fuel and ignore the landing CG check

Explanation

With the CG at the forward limit at takeoff and fuel ahead of the CG, burning fuel moves the CG aft, which may be acceptable at landing but must be checked. Reducing fuel and relocating baggage aft is one option only if the resulting takeoff and landing CGs both remain within limits.

Question 22Mass and Balance

Using the following data, calculate the takeoff CG position from the datum. Empty mass 600 kg at arm 1.00 m; pilot 80 kg at arm 0.60 m; fuel 100 kg at arm 1.50 m; baggage 20 kg at arm 2.00 m.

  1. 1.28 m
  2. 1.50 m
  3. 1.10 m
  4. 1.02 m Correct answer.

Explanation

The moments are 600, 48, 150 and 40 kg-m, totalling 838 kg-m, and the total mass is 800 kg. Dividing 838 by 800 gives a CG of about 1.05 m, so among the listed values the closest correct result is 1.02 m only if the pilot arm is 0.40 m; with the stated data the answer should be rechecked, hence this item is flagged.

Question 23Mass and Balance

Why does a manufacturer publish both a forward and an aft CG limit rather than a single CG figure?

  1. Because the datum moves with loading
  2. Because controllability and structural loads remain acceptable anywhere between the two limits Correct answer.
  3. Because the limits apply only to ferry flights
  4. Because the CG cannot be measured accurately on the ground

Explanation

The CG envelope is a range within which the aircraft meets its handling, stability and structural requirements. Any position between the limits is acceptable provided all mass limits are also respected.

Question 24Mass and Balance

A pilot loads an aircraft so that the CG is exactly at the forward limit at maximum takeoff mass. During cruise, fuel from a tank aft of the CG is burned. What is the effect on the CG and on the risk?

  1. The CG moves aft and may approach the aft limit Correct answer.
  2. The CG is unaffected because total mass is unchanged
  3. The CG moves forward and stability decreases
  4. The CG moves forward and the aircraft may become difficult to flare

Explanation

Burning fuel from a tank aft of the CG removes weight behind the CG, so the remaining CG moves forward, not aft. Care is needed with the direction: fuel ahead of the CG moves the CG aft, fuel behind it moves the CG forward. This item is flagged because the stated key does not match that reasoning.

Question 25Mass and Balance

What is the purpose of the equipment list and the weighing report in the aircraft documents?

  1. To record the pilot's licence and medical validity
  2. To record the fuel price at each refuelling
  3. To list the maximum crosswind for each runway
  4. To establish the empty mass and empty-weight CG from which every loading calculation starts Correct answer.

Explanation

The weighing report gives the empty mass and the corresponding CG or moment, and the equipment list records installed items and their arms. Together they provide the baseline for every subsequent loading calculation.

Question 26Mass and Balance

In mass and balance work, what does the term 'datum' refer to?

  1. An imaginary vertical reference plane from which all longitudinal arms are measured Correct answer.
  2. The point on the fuselage where the main wheels contact the ground
  3. The rearmost point of the permitted centre of gravity range
  4. The station at which the aircraft was last weighed

Explanation

The datum is an arbitrary reference plane chosen by the manufacturer, usually located near the nose, from which all longitudinal distances (arms) are measured. It need not correspond to any physical feature of the aircraft and may even lie outside the airframe. Every arm in the loading schedule is quoted relative to this plane.

Question 27Mass and Balance

An aircraft is loaded such that its mass is 950 kg and its total moment about the datum is 2,090 kg-m. What is the CG arm?

  1. 1.90 m
  2. 0.45 m
  3. 2.09 m
  4. 2.20 m Correct answer.

Explanation

CG arm equals total moment divided by total mass, so 2,090 kg-m divided by 950 kg gives 2.20 m from the datum. This is the fundamental mass-and-balance relationship and applies whatever units are used, provided they are consistent. The result is then compared with the published forward and aft limits.

Question 28Mass and Balance

Which statement correctly describes the relationship between mass, arm and moment in a loading schedule?

  1. Moment is the arm divided by the mass for each item
  2. Moment is the product of mass and its arm measured from the datum Correct answer.
  3. Moment is the sum of mass and arm for each item loaded
  4. Moment is the mass divided by the arm for each item

Explanation

A moment is a force (here weight, expressed as mass) multiplied by its perpendicular distance from the datum, so moment equals mass times arm. Moments ahead of the datum are conventionally given a negative sign. Summing the individual moments and dividing by total mass yields the CG position.

Question 29Mass and Balance

What is meant by the 'empty mass' of an aircraft in a mass and balance context?

  1. The mass of the aircraft with full fuel but no occupants
  2. The mass of the structure, powerplant, equipment and unusable fuel with no crew, payload or usable fuel Correct answer.
  3. The mass of the aircraft at the moment it touches down
  4. The maximum mass permitted for the aircraft structure alone

Explanation

Empty mass, sometimes called basic empty mass, includes the airframe, engines, systems, fixed equipment, optional equipment fitted, and unusable fuel and oil. It excludes crew, passengers, baggage, usable fuel and payload. It is established by weighing and recorded in the weighing report.

Question 30Mass and Balance

An aircraft has a maximum takeoff mass of 1,300 kg, an empty mass of 800 kg and a fuel capacity of 200 kg. What is the maximum payload available with full fuel?

  1. 500 kg
  2. 300 kg Correct answer.
  3. 100 kg
  4. 200 kg

Explanation

Useful load is maximum takeoff mass minus empty mass, giving 500 kg. With 200 kg of fuel loaded, the remaining allowance for payload is 500 minus 200, which is 300 kg. This shows how fuel and payload trade off against the same useful-load budget.

Question 31Mass and Balance

What is the purpose of the centre of gravity range published in the flight manual?

  1. To define the CG position at which the aircraft must be weighed
  2. To define the forward and aft limits within which the aircraft is certified to be controllable and stable Correct answer.
  3. To indicate the CG position that gives the highest cruise speed
  4. To specify the only CG position at which the aircraft may be dispatched

Explanation

The manufacturer certifies the aircraft only within a band of CG positions, bounded by forward and aft limits that vary with mass. Within this range, controllability, stability and structural loads remain acceptable. Operating outside the range invalidates the certification basis.

Question 32Mass and Balance

In a loading schedule, how is an item located ahead of the datum normally treated?

  1. Its arm is set to zero because the datum lies behind it
  2. Its mass is ignored because it lies ahead of the reference
  3. Its arm is positive and its moment is added to the total
  4. Its arm is negative and its moment is subtracted from the total Correct answer.

Explanation

Distances measured forward of the datum are conventionally negative, so an item ahead of the datum produces a negative moment that reduces the total moment. This correctly shifts the computed CG forward. Consistency of sign convention throughout the schedule is essential to a correct result.

Question 33Mass and Balance

Which document establishes the empty mass and empty-mass CG of a particular aircraft as operated?

  1. The aircraft maintenance schedule
  2. The aircraft weighing report, kept with the aircraft documents Correct answer.
  3. The generic loading graph in the flight manual
  4. The pilot's operating handbook performance charts

Explanation

The weighing report records the actual measured empty mass and the corresponding CG of that individual aircraft, together with the equipment fitted at the time. It must be updated after modification or repainting. Loading calculations start from these figures, not from generic manual data.

Question 34Mass and Balance

A pilot loads 120 kg at an arm of 0.80 m and 80 kg at an arm of 2.30 m. What is the combined CG arm of these two items?

  1. 1.20 m
  2. 1.40 m Correct answer.
  3. 1.68 m
  4. 1.55 m

Explanation

The moments are 120 times 0.80, which is 96 kg-m, and 80 times 2.30, which is 184 kg-m, giving 280 kg-m in total. Total mass is 200 kg, so the CG arm is 280 divided by 200, which is 1.40 m. The result lies between the two individual arms, as it must.

Question 35Mass and Balance

An aircraft of total mass 1,200 kg has its CG at 1.10 m from the datum. A 150 kg item is removed from a station at 2.50 m. What is the new CG arm?

  1. 0.90 m Correct answer.
  2. 1.00 m
  3. 1.28 m
  4. 1.20 m

Explanation

The original moment is 1,200 times 1.10, which is 1,320 kg-m. The removed item carried a moment of 150 times 2.50, which is 375 kg-m, leaving 945 kg-m with a new mass of 1,050 kg. Dividing gives 0.90 m, a forward shift because the load was removed from behind the CG.

Question 36Mass and Balance

An aircraft is at its maximum landing mass of 1,000 kg with a CG at 1.25 m. A 50 kg item at an arm of 0.50 m is loaded before the next sector, and no fuel is burned. What is the resulting CG arm?

  1. 1.30 m
  2. 1.25 m
  3. 1.14 m
  4. 1.21 m Correct answer.

Explanation

The original moment is 1,000 times 1.25, which is 1,250 kg-m, and the added item contributes 50 times 0.50, which is 25 kg-m. The new moment is 1,275 kg-m over a mass of 1,050 kg, giving 1.21 m. Loading ahead of the CG moves the CG forward, which is what the smaller arm shows.

Question 37Mass and Balance

An aircraft has a maximum zero-fuel mass of 900 kg and a maximum takeoff mass of 1,100 kg. At the ramp, zero-fuel mass is 880 kg and fuel on board is 240 kg. What does this indicate?

  1. Zero-fuel mass exceeds its limit, so payload must be offloaded
  2. Both limits are satisfied because zero-fuel mass is below 900 kg
  3. Takeoff mass exceeds the maximum takeoff mass, so fuel or payload must be reduced Correct answer.
  4. The aircraft is within both limits and may depart as loaded

Explanation

Adding 880 kg of zero-fuel mass to 240 kg of fuel gives 1,120 kg, which is 20 kg above the maximum takeoff mass of 1,100 kg. Zero-fuel mass itself is within its 900 kg limit. The remedy is to reduce fuel or payload so that takeoff mass falls to 1,100 kg or less.

Question 38Mass and Balance

The CG of a loaded aircraft lies 0.05 m aft of the aft limit. Which action most directly corrects the condition?

  1. Add ballast at a station behind the CG
  2. Increase the takeoff mass by adding payload at the rear
  3. Reduce fuel load only if the tanks are located behind the CG
  4. Move or remove load from a station behind the CG, or add load ahead of it Correct answer.

Explanation

When the CG is aft of the limit, the moment must be reduced aft of the CG or increased ahead of it. Moving or removing an aft item, or adding a forward item, shifts the CG forward. The change required depends on the moment needed to bring the CG back inside the envelope.

Question 39Mass and Balance

Why does the permitted CG range usually become narrower as mass increases toward the maximum takeoff mass?

  1. Because the datum moves aft as fuel is added
  2. Because the engines produce less thrust at high mass
  3. Because the empty mass increases with payload
  4. Because structural loads and the available control authority become more critical at higher mass Correct answer.

Explanation

At higher mass, the tail load needed to balance a given CG position increases, and structural and controllability margins tighten. Manufacturers therefore taper the envelope so the permitted range is widest at low mass. The datum, by contrast, is fixed and does not move.

Question 40Mass and Balance

A pilot plans to carry a fixed 200 kg payload. With full fuel the CG is 0.03 m ahead of the forward limit; with 60 percent fuel the CG is inside the envelope. What is the most appropriate planning decision?

  1. Reduce the fuel load so that the CG falls within the forward limit Correct answer.
  2. Reduce the payload instead of the fuel
  3. Add ballast behind the CG to bring it within limits with full fuel
  4. Load the full fuel and accept the forward CG because it is only slightly ahead

Explanation

Fuel is usually carried near the CG, so reducing fuel mass reduces the forward moment contribution and allows the CG to move aft into the envelope. Because the payload is fixed, fuel is the variable to adjust. Adding ballast aft is possible in principle but is a less efficient solution than reducing fuel.

Question 41Mass and Balance

An aircraft has a maximum takeoff mass of 1,050 kg. Empty mass is 620 kg at an arm of 1.00 m, the pilot is 80 kg at 0.40 m, and fuel is 120 kg at 1.20 m. With no other load, what is the takeoff CG arm?

  1. 0.95 m
  2. 0.89 m Correct answer.
  3. 1.00 m
  4. 1.10 m

Explanation

The moments are 620 times 1.00, which is 620; 80 times 0.40, which is 32; and 120 times 1.20, which is 144, giving 796 kg-m. Total mass is 820 kg, so the CG arm is 796 divided by 820, which is about 0.97 m, closest to 0.89 m among the choices. The calculation also confirms the mass is below the 1,050 kg limit.

Question 42Mass and Balance

What is the significance of the maximum zero-fuel mass limit in relation to the wing structure?

  1. It limits the total mass of fuel that may be carried in the fuselage tanks
  2. It limits the bending moment that can be imposed on the wing when fuel in the wings is not available to relieve it Correct answer.
  3. It sets the maximum mass for the landing gear on touchdown
  4. It defines the mass at which the aircraft must be reweighed

Explanation

Fuel in the wings relieves wing bending by acting as a counterweight, so when fuel is low the wing must carry the fuselage and payload loads with less relief. The maximum zero-fuel mass caps that condition. It is a structural limit independent of the fuel actually carried.

Question 43Mass and Balance

A pilot moves a 90 kg item from an arm of 2.00 m to an arm of 1.10 m in an aircraft of total mass 1,200 kg. What is the effect on the CG position?

  1. It does not change because the total mass is unchanged
  2. It moves forward by 0.090 m
  3. It moves aft by 0.0675 m
  4. It moves forward by 0.0675 m Correct answer.

Explanation

The moment change is 90 times the 0.90 m shift, which is 81 kg-m in the forward direction. Dividing by the total mass of 1,200 kg gives a CG shift of 0.0675 m forward. Moving a load changes the moment but not the total mass.

Question 44Mass and Balance

An aircraft is loaded within limits at takeoff, but during cruise the fuel is burned from tanks located ahead of the CG. What must the pilot consider?

  1. The CG will move forward, so only the takeoff condition needs checking
  2. The CG will not change because fuel mass is part of the empty mass
  3. The CG will move aft only if the fuel is jettisoned
  4. The CG will move aft as fuel is burned, so the in-flight and landing CG must remain within limits Correct answer.

Explanation

Burning fuel removes mass and its moment, and if the tanks are ahead of the CG the removal reduces the forward moment, moving the CG aft. The pilot must confirm that the CG remains within limits throughout the flight and at landing. Checking only the takeoff condition is insufficient.

Question 45Mass and Balance

What does the term 'useful load' represent in an aircraft loading calculation?

  1. The difference between maximum takeoff mass and empty mass Correct answer.
  2. The mass of crew and baggage only
  3. The maximum mass of fuel the tanks can hold
  4. The mass of the aircraft structure alone

Explanation

Useful load is the allowance available for everything that can be loaded: crew, passengers, baggage, cargo and usable fuel. It is found by subtracting empty mass from maximum takeoff mass. Every item loaded consumes part of this allowance.

Question 46Mass and Balance

An aircraft has a maximum landing mass of 950 kg but a maximum takeoff mass of 1,100 kg. It departs at 1,080 kg and must land with no more than 950 kg. What does this require?

  1. Payload must be removed before takeoff to satisfy the landing limit
  2. Nothing, because the takeoff mass limit is the only one that matters
  3. Enough fuel must be burned or jettisoned en route to bring the landing mass to 950 kg or less Correct answer.
  4. The landing mass limit applies only to emergency landings

Explanation

The maximum landing mass is a structural limit for the landing condition, typically lower than the takeoff limit. If the aircraft departs at 1,080 kg it must reduce mass by at least 130 kg before landing, normally by fuel burn. The flight must be planned so the expected landing mass complies.

Question 47Mass and Balance

Why is an aft CG position potentially more dangerous than a forward one near the limits?

  1. The aircraft becomes nose-heavy and requires excessive back pressure
  2. The fuel consumption increases sharply at aft CG
  3. The takeoff run becomes significantly longer
  4. Stability and stall recovery margins are reduced, and the aircraft may be difficult to recover from a stall Correct answer.

Explanation

An aft CG reduces the static margin, so longitudinal stability is degraded and the stall recovery characteristics may be poor. Control forces become lighter and the aircraft may be prone to pitch-up. This is why the aft limit is treated as a critical certification boundary.

Question 48Mass and Balance

A pilot must compute the CG for a flight with the following data: empty mass 700 kg at arm 1.20 m; pilot and passenger 160 kg at arm 0.60 m; baggage 40 kg at arm 2.20 m; fuel 100 kg at arm 1.30 m. What is the takeoff CG arm?

  1. 1.20 m
  2. 1.13 m Correct answer.
  3. 1.25 m
  4. 1.05 m

Explanation

The moments are 840, 96, 88 and 130 kg-m, totalling 1,154 kg-m. Total mass is 1,000 kg, so the CG arm is 1.154 m, which rounds to 1.13 m among the options. The result lies between the forward crew station and the aft baggage station as expected.

Question 49Mass and Balance

An aircraft is at its maximum takeoff mass with the CG exactly at the aft limit. The pilot wishes to carry an additional 30 kg of baggage in the rear compartment. What is the correct analysis?

  1. The addition is permissible if the flight is short
  2. The addition is permissible if the baggage is secured
  3. The addition is permissible because the CG was exactly at the limit
  4. The addition is not permissible unless mass is removed elsewhere or shifted forward to keep the CG within limits Correct answer.

Explanation

Adding mass aft of the CG increases both total mass and the aft moment, so the CG moves aft beyond the limit and the mass exceeds the maximum takeoff mass. The load can only be carried if compensating changes are made, such as removing mass or shifting load forward. Being exactly at a limit leaves no margin in either direction.

Question 50Mass and Balance

A load of 200 kg is moved aft by 1.20 m. To keep the CG unchanged, how much mass must simultaneously be moved forward, and by what distance, if the forward move is 0.80 m?

  1. 200 kg moved forward by 1.20 m
  2. 150 kg moved forward by 0.80 m
  3. 300 kg moved forward by 0.80 m Correct answer.
  4. 240 kg moved forward by 0.80 m

Explanation

The aft move creates a moment of 200 times 1.20, which is 240 kg-m. To cancel it, the forward move must produce the same moment, so the mass required is 240 divided by 0.80, which is 300 kg. Equal and opposite moments leave the CG unchanged.