Datum, Moments, And Determining CG Flashcards
In straight and level flight what is the sum of all the forces
0
What is a moment
The tendency of a force to rotate round an object round a axis
What is the moment formula
Moment = mass x balance arm
What is a balance arm
The distance from the datum point to the CG of mass
What is the formula to find CG position
CG = total moment / total mass
How can you ensure you remain within the CG limits throughout the whole flight
Calculate CG for take off / zero fuel / landing mass
Where must CG fall
Within the Mean Aerodynamic Chord (MAC)
How do you find the %MAC
% MAC =
(CG arm - LeMAC)/ mean aerodynamic chord x100
In what ways can the CG be changed to ensure it falls within the limits
Moving existing load to different parts of the aircraft
Removing or adding load
Adding ballast
What is the formula to determine how much mass you need to move to change the CG
m/M= d/D
How must ballast be entered on a load sheet
As ‘unusable’ fuel
Who’s responsibility is it for weighing a aircraft
Operators responsibility
Why must a aircraft be weight before it enters service
To establish its mass and centre of gravity
What is the period of re-weighing for individual aircraft
4 years
What must happen when a modification on mass and cg is made
Accounted and documented
What must be done if the effects of a modification on mass and centre of gravity are not known
Aircraft must be re-weighed
What is the definition of a fleet aircraft
A group of aircraft of the same model and configuration
What the weighing schedule for a aircraft fleet between 1-3 aircraft
4 years
What is the weighing schedule for aircraft in a fleet of 4-9 aircraft
2/3 of the aircraft must be weighed every 4 years
How many points of contact does a aircraft need to have when being weighed
Min 3
What must the location of the weighing of a aircraft be like
In a hanger with the air conditioning off
What must the exterior of the aircraft be like for weighing
Washed and dry
What must the load of the aircraft be like for weighing
Tanks drained with only unusable fuel remaining
Inventory checked to make sure no extra items
Hydraulics and engine oil full
When must the aircraft be reweighed due to the effect of modifications
When the dry operating mass changes by more than 0.5% of the max landing mass
What is the purpose of standard mass values
To speed up the boarding process
What is the standard mass for flight crew
85kg
What is the standard mass value for cabin crew
75 kg
What is the categorisation of a child
2> 12 years of age
When can a holiday charter flight no longer be classed as holiday charter
When more than 5% of the seating capacity is non revenue load
How often does weighing equipment need to be calibrated
Every 2 years
What are the effects of mass distribution
Stress on the aircraft
What is stress
The force divided by cross sectional area
What are the different types of stress
Torsion (twisting)
Tension ( pulling apart)
Compression (pushing together)
Shear (one layer sliding over another)
What types of stress occur if an object is bending
Tension
Compression
Shear
What are the 3 different options for crew weights
Actual masses of the crew
Standard masses of the crew (85/75kg)
Other standard masses acceptable to easa
If an aircraft had less than 10 seats how is the passenger weight to be calculated
Verbally asking the passenger
Standard mass for a child
35 kg
How must the weight of checked baggage be calculated for a aircraft with <18 seats
Must be weighed
How must the weight of checked baggage be worked out for a aircraft with >20 seats
Standard masses may be used
What is design load
The load (or stress) measured in G that the aircraft is designed to not go over
What is the ultimate load
The load (or stress) measured in G that the aircraft structure will fail at
How is the ultimate load calculated
When the aircraft can hold a load (or stress) of over 1.5 (50% extra) the design load limit for more than 3 seconds
What is the load limit “proof- test”
When the flying controls/ gear etc should function normally for 3 mins at 1.125 times the design load limit (12.5%) over
When is a material said to have “failed” from fatigue
When a small crack reaches a critical size that it instantaneously becomes a large fracture across a component
What does fatigue require before failure
Fatigue requires a number of cycles before failure
It is a medium to long term source of airframe damage
How much does fatigue increase by per % if weight increase
1% weight increase = 5% fatigue consumption increase
Effects of s forward cg
Excessive longitudinal stability
Unresponsive to control inputs
Reduces aircraft performance
Effects of excessive aft cg
Controls feel very light
Easy to overstress aircraft
In light aircraft spin is more difficult / impossible to recover from
If you want to commit aviation with a MSTOM of 63,060 in the MRJT how much taxi fuel can you have
No more than 260kg
What tank do you use first and why
Centre, relieves stress at wing roots
Fuel in roots can be gravity fed
What fuel tank is used for take off and why
Wing tanks
Usually fuel you know works (ie had with you before)
Where as centre tank is usually straight from the bowser
For the MRJT what is the passenger mass
84kg regardless of age
For the MRJT what is the passenger baggage Weight
13kg
For the MRJT what is the crew weights
Both flight and cabin = 90kg (however they are already accounted for in variable load)
How can you gross error check a load sheet
1) ensure allowed take off mass selected is the lowest mass
2) make sure max mass is not exceeded
3) the difference between limiting mass and actual take off mass should be the “underload before LMC”
What are the 4 facts about LMC
Command has to be notified of any LMC
Can happen after engine start
LMC limits set out in operations manual
Underload adjusted by value in LMC
What is factored stall speed
Vs x 1.3
May give you either factored stalling speed or unfactored stalling speed
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