Mass and Weight Limits

Question 1

What are controlling regulations for Mass and Balance?

Answer 1

EU-OPS

Question 2

What do the EU-OPS specify for Mass and Balance?

Answer 2

• Loading, mass and CG of the aeroplane must comply with:
  o Limitations in the AFM or Operations Manual, whichever is more restrictive
• Set out requirements to be included in the Operations Manual

Question 3

What’s the Basic Empty Mass (BEM) or Basic Mass (BM)?

Answer 3

The mass of the aircraft with:
- Basic equipment
- Unusable fuel and other fluids
- Lubricating oil in the engines
- Fire extinguishers
- Pyrotechnics
- Emergency oxygen equipment
- Supplementary electronic equipment

Question 4

What’s the Variable load (VL)?

Answer 4

Often referred as the “operational items”, consists of:

• Crew
• Crew’s baggage
• Removable equipment that is required for that flight, for example:
  o Catering
  o Passenger service equipment
  o Food and beverages
  o Potable water
  o Lavatory chemicals

Question 5

What’s the Dry Operating Mass (DOM)?

Answer 5

BM + VL

Question 6

What’s the Useful or Disposable Load?

Answer 6

• Traffic Load:
  o Passengers
  o Their baggage
  o Their freight
• The usable fuel
• The usable oil where appropriate

Question 7

What’s the Traffic Load?

Answer 7

It’s the total mass of:

• Passengers
• Baggage
• Cargo
• Carry-on specialist equipment including any ballast
• Non-revenue load
  o Spare parts
  o Positioning crew

Question 8

What’s the Zero Fuel Mass (ZFM) ? What’s the Maximum Zero Fuel Mass (MZFM)?

Answer 8

Zero Fuel Mass is the total mass of the aircraft NOT considering the usable fuel
- DOM + Traffic Load
Maximum Zero Fuel Mass (MZFM) is a structural limit in the wing roots:
- In some aircraft the mass of fuel in fuselage tanks is included in the ZFM
- Only take account of fuselage fuel in ZFM calculations when specifically instructed to do so

Question 9

What’s the Operating Mass?

Answer 9

DOM of aircraft plus fuel but without traffic load
- It can be thought as the wet operating mass as opposed to the DOM defined earlier

Question 10

What the taxy mass? What’s the Maximum Taxy MAss (MTM)?

Answer 10

Taxy Mass (TM) is the mass of the aircraft before engine start, also known as Ramp Weight or Ramp mass and is sometimes defined as:
- Mass at the start of the taxy

Maximum Taxy Mass (MTM) is a structural limit:
- Greatest mass at which the aircraft can be taxyed

Question 11

What’s the Take-off mass?

Answer 11

It’s the mass of the aircraft at the start of the take-off run
- It may be affected by performance calculations

Question 12

What’s the Maximum Structural TOM?

Answer 12

It is a structural limit defined as:
- Maximum mass that the aircraft can take-off at anywhere in the world in the most favourable conditions in accordance with Certificate of Airworthiness
- Usually the MTM minus Standard Taxy Fuel
o Can be referred to as the Maximum Take-off mass authorized (MTMA)

Question 13

What’s the allowed Take-off Mass?

Answer 13

It’s the mass taking into consideration:
- All possible limitations for take-off including:
o Restrictions caused by the Regulated Take-off Mass and
o Regulated Landing Mass

Question 14

What’s the Performance Limited Take-off and Landing Mass (PLTOM)? What’s the Performance Limited Landing Mass (PLLM)?

Answer 14

Performance Limited Take-off and Landing Mass (PLTOM) is the take-off mass by departure airfield considerations such as:
- Runway length
- Obstacles
- Temperature and
- Altitude
Performance Limited Landing Mass (PLLM) is the landing mass limited by similar destination airfield considerations, it is a limit derived from Performance Calculations

Question 15

What’s the Regulated Take-Off Mass?

Answer 15

Is the lower of:
- Maximum structural TOM and the PLTOM

Question 16

What’s the Landing Mass?

Answer 16

It is the mass of the aircraft as it crosses the threshold on landing

Question 17

What’s the Maximum Structural Landing Mass (MSLM)?

Answer 17

It’s a structural limit

Question 18

What’s the Regulated Landing Mass (RLM)?

Answer 18

It is the lower of:
- MSLM and PLLM

Question 19

What’s the All Up Mass (AUM) or the All Up Weight (AUW)?

Answer 19

It’s the total mass or weight of the aircraft at a particular time

Question 20

What’s the Maximum All Up Mass (MAUM)?

Answer 20

MAUM is the greatest mass that an aircraft can be loaded to. Although the definitions are different, the MAUM and the Maximum Taxy Mass describe the same mass.

Question 21

Can the Maximum In-Flight Mass exceed the MTOM? Can the airborn weight be greater than TOM?

Answer 21

• It can, in theory, exceed the MTOM because the forces in flight and the limitations derived from them differ from those experienced during the take-off roll.
• In practice, however, the airborne weight can never be greater than TOM unless the aircraft has been refueled in flight.

Question 22

What’s Maximum Operational Passenger Seating Configuration (MOPSC)?
What does it exclude?
For what is it established?

Answer 22

The MOPSC is the maximum passenger seating capacity of an individual aircraft
- Excluding crew seats
- Established for operational purposes and specified in the operations manual

Question 23

How often do you have to weight an aircraft if it is considered individually?

Answer 23

4 years

Question 24

What if fleet advantages are used?

Answer 24

9 years

Question 25

What are the weighting conditions if aeroplanes are transferred between EASA operators?

Answer 25

They do not need to be weighted unless 4 years have passed since the last time the weights were checked

Question 26

What must the operator account for and document in this case? How can they do this?

Answer 26

Accumulated effects of modifications and repairs between weightings.

By either weighting the equipment added and removed, or by using standard masses

Question 27

What’s the margin they can afford to a change of the DOM?

Answer 27

By > 0.5% of the MLM
CG shifts > 0.5% of the MAC

Question 28

What happens if these margins are not respected?

Answer 28

Aircraft must be reweighted and CG re-established
Exceptionally, this can be done by calculation, but the operator has to justify the method used to the Authority

Question 29

By whom must the weighting be carried out in the Aircraft Weighting Conditions?

Answer 29

o Manufacturer
o Approved Maintenance Organization

Question 30

Which normal precautions must be taken?

Answer 30

o Checking for completeness of the aeroplane and equipment:
 Established by reference to an equipment list
o Determining that fluids are properly accounted for
o Ensuring aeroplane is clean
o Ensuring that weighting is accomplished in an enclosed building (important)
o Three points of support

Question 31

How must the weighting equipment be?

Answer 31

o Properly calibrated
o Zeroed
o Used in accordance with the manufacturer’s instructions
o Must enable the mass of the aeroplane to be established accurately

Question 32

By whom and when do the scales need to be calibrated?

Answer 32

o Calibrated by:
 The manufacturer
 Civil deparment of weights and measures or
 Appropriately authorized organization

o Calibrated within:
 Within 2 years or
 Within a time period defined by:
* Manufacturer or
* The Weighting equipment, whichever is less

Question 33

What needs to be done once the BEM and CG have been established?
How are the changes tracked?

Answer 33

o It is recorded
o Changes are tracked in a document known as the “Weighting Schedule”
 Form part of the aircraft technical log

Question 34

To whom must the manufacturer give the weighting report?

Answer 34

To the operator

Question 35

What must the operator do with the weighting report? What’s the operator’s responsibility?

Answer 35

 Add the variable load to establish the DOM
 It is the operator’s responsibility to ensure that the aircraft has been weighed correctly

Question 36

Where are the CG limits of the aircraft found?

Answer 36

In its Operating Data Manual (ODM)

Question 37

What’s the name of the equipment used to weight the aircraft? What must be done to find the net weight?

Answer 37

Tare Unit:
o Must be subtracted from the scale reading to find the net weight

Question 38

What’s the unit of weighting points?
What does it allow?
What does also need to be listed in the weighting report?

Answer 38

Stations:
o Allows calculation of the moment and the CG position

• Missing Equipment or variations to the BEM

Question 39

What operators work out if they have a fleet that meets certain criteria?

Answer 39

A single DOM and CG position

Question 40

According to the EU-OPS:

Tolerances

1 What’s the margin of a DOM of any aeroplane or the calculated DOM of any aeroplane of a fleet for that aeroplane to be omitted from that fleet?

2 What happens if aeroplane’s mass is within DOfM tolerance but its CG position falls outside the permitted fleet tolerance?

3 What happens if there’s a physical accurately accountable difference that causes exceedance of the fleet tolerances?

4 What happens if no MAC is published?

Answer 40

1
> ± 0.5% of MSLM from the established Dry Operating Fleet Mass (DOfM) or

CG position varies by more than ± 0.5% of the MAC from the fleet’s CG

2

Aeroplane may still be operated under the applicable DOfM but with an individual CG position

3
Aeroplane may be maintained in the fleet provided that appropriate corrections are applied to the mass and/or CG

4
i. Aircraft must be operated with their individual mass and CG position values or
ii. Must be subjected to a special study approval

Question 41

According to the EU-OPS:

Use of fleet values

1 What happens if after weighting of an aeroplane, or if any change occurs in the aeroplane equipment or configuration?

2 What happens if the aeroplane is not weighted since last fleet mass evaluation?

3 How can an aeroplane be added with flee values?

4 When do fleet values need to be updated?

Answer 41

1

i. Operator must verify that this aeroplane falls within the tolerances specified in subparagraph (i) above (tolerances)

2

i. Can be kept in a fleet operated with fleet values, provided that
a. Individual values are revised by computation and
b. Stay within the tolerances defined in subparagraph (i) above

ii. If individual values no longer fall within the permitted tolerances, the operator must either determine:
a. New fleet values fulfilling the conditions of sub-paragraph (i) above
b. or operate the aeroplanes not falling within the limits with their individual values

3

i. Operator must verify by weighting or computation that its actual values fall within the tolerances specified in subparagraph (i) above

4

Fleet values must be updated at least at the end of each fleet mass evaluation

Question 42

When must the operator weight during fleet mass evaluations?

Which aeroplanes need to be selected?

What’s the interval between 2 fleet mass evaluations?

How must the CG be expressed?

When must fleet masses be recalculated? What about individual aircraft?

Answer 42

• See table in BGL
• Aeroplanes in the fleet which have not been weighed for the longest time must be selected
• Must not exceed 48 months
• CG must be expressed as %MAC
• Every 4 years for fleet masses and every 9 years for individual aircraft