Operating above the maximum weigh (wt) limitations compromise the structural integrity of the aircraft and impairs performances…
Load factor is the ratio of max load that the aircraft can sustain to the gross weight of the aircraft… measured in G’s (the acceleration of gravity)…
- excessive G-forces can be experienced in steep turns or excessive maneuvers (turns, stalls, chandelles, lazy-eights) and turbulent air.
- Load factor has two components; centrifugal force and gravity (see left image)
- Maximum bank for most GA aircraft is 60 degrees… Load factor = 2…
Load factors and stalling speed increases
– Using the above graphs, if an aircraft has a normal unaccelerated stall speed of 50 kts at a load factor of 3 G the new aircraft stall speed is ~75 kts (see yellow dashed line).
– The maximum speed by which an aircraft can be stalled safely is specified as the Va; the designed maneuvering speed… exceeding this may lead to stalls and structural failure.
Weight and Balance
- Excessive weight reduces flight performance… e.g;
- Higher take off speeds and hence longer take-off run
- Reduced rate and angle of climb
- Lower max altitude
- shorter range
- reduced cruising speed
- reduced maneuverability
- higher stalling speed
- higher approach and landing speed
- longer landing roll
- excessive weight on nose/tail wheel (difficult steering)
- pilot is responsible for managing weight loading and management .’, make certain that weights are up to date… e.g repairs may result in the removal or addition of engine parts or equipment results in changes to the center of gravity.
- Lateral imbalance (e.g. fuel in one wing)
- Longitudinal imbalance (e.g. with excess or unsecured baggage)
- Prior to all flights determine the weight and balance checks, refer to loading conditions as set out by the aircraft manual… even in many modern aircraft it’s not possible to remain within weight limits if it is fully loaded with passengers (px), baggage and fuel.
- The following terms are important for calculating weight and balance specifications of any aircraft;
- CG limits; the specified forward and aft points for which the centre of gravity must be located in flight
- CG range; the distance between forward and aft CG limits,
Nb. Standard operating data of aircraft includes the following information for safe and efficient operation; take-off, climb, range, endurance, descent, landing
The density of the air has a pronounced effect on aircraft and engine performance regardless of altitude. Air density is affected by temp, altitude and humidity… the density altitude can be imputed by using pressure altitude and flight level temperature.
With decreased density of air;
- power is reduced; because engine takes in less air
- thrust is reduced; because propeller is less efficient
- lift is reduced; because thin air exerts less force on the aerofoils…
Atmospheric temperature and pressure are the dominant factors that affect the performance of the aircraft..
Air pressure varies with temperature and altitude…
– standard reference at sea level is; 15 deg C, and a surface pressure of 1013 hPa
– all engine instruments are calibrated to the standard atmosphere… therefore corrections must be applied for real-conditions.
– pressure altitude is the height above the standard atmosphere… the altitude in the standard atmosphere corresponding to the sense of pressure.
For illustration purposes only – note pressures are in inches(!!) of Hg (inHg) not hPA,
1 inHg –> 68.9476