Certification: Stress and Loading Flashcards
What other exams does the Mass and Balance exam complement?
Flight planning
Operational Procedures
Performance
Where are the performance and design requirements for aeroplanes set out in?
Cs 25
Cs 23
What is the CS 25 and to which airplanes does it apply?
Certification Specification 25:
- All multi-engine jets
- All multi-engine turboprop
- NOT in the commuter catergory
- > 9 passenger seats
- MTOW > 5700 kg
What is the CS 23 and to which airplanes does it apply?
Certification Specification 23:
- All aircraft = or < 9
- Take-off mass < 5700 Kg
- Commuter category propeller driven twins:
- MTOW = or < than 8618 kg and
- 19 passenger seats or less
What are other similar documents in other states?
FAR 25 and FAR 23 in the US
With what other operating rules is the CS25/23 combined? What does it define?
Operating Rules specified in EU-OPs, define the standard of safety for aeroplanes engaged in public transport operations
What are Mass and Balance calculations a essential precursor of? what does it establish?
- Performance calcultations
- Limiting masses that ensure that the space required does not exceed the space available.
What forces create stresses in the aircraft structure?
What is the definition of stress?
What kind of stresses can we find?
How do they act?
What do they do?
- Lift, weight, thrust and drag
- Stress = Force/cross-sectional area to which it is applied
- Twisting or torsion, tension, compression or shear
- Individually or together
- Bend, creates tension on the outside and compression on the inside
What’s the name of the stress at which the structure fails?
Ultimate stress = fail point for a single application of a static load
What can cause cumulative damage and what does it end up in?
- Loading and unloading structure many times below the ultimate stress.
- Structure failing catastrophically well below ultimate stress
What’s metal fatigue and does fatigue affect to other structures? How are civil airliners designed to prevent fatigue?
- cumulative stress in metal structures.
- yes, but they react in a different way
- Creating a safe design where crack-arrest features and parallel load paths allow the aircraft to fail in some degree until a periodic inspection reveals the failures and components canbe replaced
What does MZFM stand for and how is it defined?
Maximum Zero Fuel Mass: maximum permissible aircraft weight disregarding fuel
What are the main loads on a wing?
What do they incorporate?
Beding loads
Tension and Compression (both in flight and on the ground
Where is the maximum bending?
At the wing root
What reduces the bending moment of lift?
Fuel & Engine moment
How are primary bending and shear loads controlled?
By observing “g” and loading limits, in particular MZFM
What does the manufacturer’s limit ignore and what does he/she ensure?
Effect of fuel load in the wings
Ensures that the value of maximum bending of the wing at the wing root is not exceeded at the designed maximum load facto of 2.25g of the aircraft at the MZFM
What is aerodynamic flutter?
An undamped oscillation caused by aerodynamic imbalance
How are foces on spars affected?
By the amount of fuel in the wing
What do the standard fuel management procedures do?
- Keep fuel in the outboard tanks to balance lift and
- Reduce the fatigue loads on the wing root
What is the cause of twisting or torsional loads on an aircraft?
- Shifts in the centre of gravity
- Centre of pressure
- Control surface deflection
How can these loads become extremely high?
- Wing or control surfaces suffer from aerodynamic flutter
How can we decreease the likelihood of flutter?
- Using heavy wings
- Keeping fuel on the outboard tanks (reduces stress on spar)
- Positioning engines by providing a balancing mass forward of the main wing, moving the flexural axis closer to the centre of pressure
What’s the ultimate load?
Which one is usually greater?
It is a vertical force or ‘g’ loading where the structure of the aircraft will fail
Positive g ultimate load
Load envelope
Less than ultimate load.
Edges are called limit load
Safety factor of 1.5 separates the limit and ultimate loads
What is the distinction between Weight and Mass?
Mass could be described as the inertia of an object whereas weight is the force of gravity or acceleration acting on it
Convert to the metric system the next units of mass and distance:
- 1lb to kg
. 12” or 1 ft to m - 3ft or 1 yd to m
- 2.2 lbs to kg
- 3.28 ft
- 0.454 kg
- 0.305 m
- 0.9144m
- 1 kg
- 1m
Convert the next units of volume:
1 IG to US gal
1 USG to IG
1 IG to litres
1 USG to litres
1.2 US gal
0.83 IG
4.454 litres
3.785 litres
What’s the specific gravity of fuel?
Fuel is lighter than water, its volume weights about 70% to 80% of the equivalent volumen of water.
IG of aviation fuel may weight 10x0.8 lbs = 8 lbs
SI Units (Systeme International)
What is 1 g in SI units?
What’s the wing loading?
a= 9.81 m/sec^2 and therefore 1 Kg exerts exerts a weight of 9.81 N
F=ma
Aircraft weight / wing area (N/m^2) in SI units, not in Kg/m^2
What are the Fuel and Oil Requirements?
A flight must not be commenced unless, taking into account both the meteorological conditions and any delays that are expected in flight, the aeroplane carries sufficient fuel and oil to ensure that it can safely complete the flight. In addition, a reserve must be carried to provide for contigencies
How is the fuel load split under EU-OPS?
Taxy Fuel
Trip Fuel
Contingency Fuel
Diversion Fuel
Final Reserve Fuel
Block or Ramp Fuel
What’s Taxy Fuel?
Fuel to:
o Start up
o Taxy to the end of runway
What’s trip fuel?
o From take-off to touchdown (burn-off or sector fuel)
What’s contingency Fuel?
o Extra fuel, usually a set percentage of the trip fuel, to allow for unforecast winds ant ATC re-routes. Contingency fuel can be calculated by a number of methods, see Operational Procedures.
What’s Diversion Fuel?
From point of diversion to touchdown at alternate
What’s the Final Reserve Fuel?
o Jets: 30 mins holding at 1500 ft above destination alternate aerodrome
o Reciprocating engine aeroplane: fuel to fly for 45 minutes
What’s the block or Ramp Fuel?
o Addition of all the above “standard” fuel elements
What’s the additional fuel?
- Fuel that would cater for failure of a power unit or loss of pressurization, assuming that the failure occurs at the most critical point.
- Includes fuel to descend as necessary, proceed to adequate aerodrome and hold for 15 minutes at 1500 ft and make an approach and landing
What’s the Extra Fuel?
Fuel added at the discretion of the commander
- Factors that are taken into account:
o Weather
o Likelihood of holding
How is freight secured?
ULDs (Unit Load Devices)
- Containers
- Pallets
- Bulk cargo restrained with nets
How is the size and shape of a container decided?
- Overall dimensions of fuselage
- Lower deck
- Single or dual aile system
What are the Advantages of using a container?
- Easy loading of:
o Cargo into container
o Container on and off the aircraft
o Better protection against weather and damage
o Prevention of unauthorized access to the contents
Why do we use polletised cargo and how is it secured?
- Freight dimensions are unsuitable for container ULDs
- Pallets with load spreading bars are used.
- Freight is secured with a cargo net and covered with a fire containment blanket if required.
Can you name two components of a cargo securing system?
ULD latches: YZ or XZ types
Roller tracks: which use PDUs (power drive units) to move the ULD fwd and aft within a cargo compartment
What is produced before and after loading the aircraft?
How do you check incorrect loadings?
What do you do if there are any deviations?
Instruction/report, after the loading of the aircraft, a completed load and trim sheet are produced and given to the air comander.
Incorrect loadings must be picked up bu a visual checking process
Resulting effects upon aircraft weight and balance, and take-off trim should be determined and verified before take-off
For what is bulk cargo used?
How is it loaded?
What kind of nets can you also use?
o Odd shape luggage
o Freight and mail
o Late delivery items
- Cargo is loaded randomly and secured by tie down and cargo nets
- Partition nets may be used for separate cargo loading areas
What are the two Floor Loading Limits and what are its formulas?
Distribution Load Intensity: Load / Floor or contact area
Floor Running Load: Weight / Length of the load the aircraft fore and aft axis
What’s the Manual of Mass and Balance from which exam questions are drawn?
CAP 696
