MASS (WEIGHT) & BALANCE CONTROL

LECTURE 3WEIGHT CONTROL, EFFECT OF WEIGHT & WEIGHT CHANGEMASS (WEIGHT) & BALANCE1MBC 3204 - SIR ARIFF AMCIMPORTANT FACTSCRITICAL SITUATION FOR AIRCRAFTTAKE-OFFLANDINGSTRUCTURAL LIMIT2MBC 3204 - SIR ARIFF AMCMBC 3204 - SIR ARIFF AMC3To ensure aircraft can fly safely, limitation are set by the design engineer.

Maximum Take-Off Weight (MTOW): The maximum permissible weight to conduct a takeoff.Maximum Landing Weight (MLW): The maximum permissible weight to conduct a landing.Maximum Zero Fuel Weight (MZFW): The maximum weight of an aircraft which its structural limits would allow.

REMEMBER !!MBC 3204 - SIR ARIFF AMC4For Take-Off: AUW/TOW MTOW

For Landing: AUW/LW MLWAll Up Weight (AUW)MBC 3204 - SIR ARIFF AMC5Where,PAYLOAD = Passengers & CargoFUEL = Flight Fuel + Reserve FuelDOW = Dry Operating Weight

DOW also known as Aircraft Prepared for Service (APS)

AUW = DOW + PAYLOAD + FUELEXAMPLE #1Aircraft fly from M to N, given:MTOW = 6180kgMLW = 5740kgMZFW = 5395kgDOW=4400kgFlight Fuel = 767kgReserve Fuel=250kgCalculate maximum payload that the aircraft is able to carry.6MBC 3204 - SIR ARIFF AMCSOLUTION EXAMPLE #1First we must know that the critical situations for aircraft are:During Take-off (MTOW)During Landing (MLW)In term of structural limit. (MZFW)

So, we have to consider these situation and calculate for all.

7MBC 3204 - SIR ARIFF AMCContinue..For Take-Off: AUW/TOW MTOWWe must ensure the All Up Weight during Take-off must equal or less than Maximum Take-Off Weight.

Fuel = Flight Fuel + Reserve Fuel.Find the PAYLOAD!AUW = DOW + PAYLOAD + FUEL8MBC 3204 - SIR ARIFF AMCContinue..For Landing: AUW/LW MTOWWe must ensure the All Up Weight during Landing must equal or less than Maximum Landing Weight.

Fuel = 0. We have used all the fuel during flight.Find the PAYLOAD!AUW = DOW + PAYLOAD + FUEL9MBC 3204 - SIR ARIFF AMCContinue..Structural LimitTo make sure the structure of aircraft did not fail / damage, we must consider the MAXIMUM ZERO FUEL WEIGHT.

Maximum ZERO FUEL WEIGHTIs the Total weight of aircraft WITHOUT FUEL

MZFW = AUW - FUEL10MBC 3204 - SIR ARIFF AMCComparison . . .Maximum Payload during take-off =

Maximum Payload during landing =

Maximum Zero Fuel Weight =

Select the lowest Payload as your answer. 11MBC 3204 - SIR ARIFF AMCEXAMPLE #2Aircraft fly from A to B, given:MTOW = 41,300kg, MLW = 32,250kgDOW = 23,000kgFuel Flow= 2000kg/hr Mean Speed=455knots (knots = miles/hr)Flight Distance=2150nm (nm = nautical miles)Reserve Fuel=2500kgCalculate maximum payload that the aircraft is able to carry. (**Assume MZFW is not specified)12MBC 3204 - SIR ARIFF AMCSolution #2Step 1 : Calculate Flight TimeFlight Time = (distance/mean speed)

Step 2 : Calculate Flight FuelFlight Fuel = Flight time x Fuel Flow

Step 3 : Same as solution example 1.13MBC 3204 - SIR ARIFF AMCComparison . . .Flight Time = Flight Fuel =Maximum Payload during take-off = Maximum Payload during landing = Maximum Zero Fuel Weight =

Select the lowest Payload as your answer. 14MBC 3204 - SIR ARIFF AMCQUIZ # 1For example, if an airplane is flying at a weight of 5,000 lb and the weight of fuel on board is 500 lb. What is the Zero Fuel Weight?

Some time later, after 100 lb of fuel has been consumed by the engines, the total weight of the airplane is 4,900 lb and the weight of fuel is 400 lb. What is the Zero Fuel Weight?

15MBC 3204 - SIR ARIFF AMCLECT 3 : WEIGHT CONTROLWeight is a major factor in airplane construction and operationManufacturers try to make an aircraft as light as they can. But still they have to consider the strength and the safety of aircraft.Excessive weight cause: Aircraft efficiency reducePoor performance during flight Safety margin available reduceAircraft stability reduceReduce economical profit

16MBC 3204 - SIR ARIFF AMCMK Airlines Flight 1602, a 747-200F, crashed while attempting to take off from Halifax Stanfield International Airport on 14 October 2004. The aircraft's take-off weight had been incorrectly calculated, and the plane was only briefly airborne before impacting an Earth berm at the end of the runway. The seven-member crew was killed.

17MBC 3204 - SIR ARIFF AMCIt concludes that the crew carelessly transferred and used weight data from the aircrafts previous flight while calculating performance criteria for the next take-off. The obsolete data misled the crew to derive incorrect thrust settings and critical speeds for take-off.About two-thirds of the way along Halifaxs runway 24, the aircraft rotated, but failed to become airborne. Its tail struck the ground twice, the second time with just 130m (420ft) of the 2,682m runway remaining. The jet overran the runway by 250m and briefly lifted off for a distance of 100m before it struck an earth berm, the impact severing the tail section and causing the 747 to crash 370m beyond. All seven crew members on board were killed.1718MBC 3204 - SIR ARIFF AMCEFFECT OF OVERLOADED AIRPLANEIncreased Takeoff Speedbecause more lift is necessary to counter the additional weight, higher speed is necessary to create sufficient lift to attain flight.Longer Takeoff Rollthe increase in necessary speed for takeoff and slower acceleration due to increased weight translates to more runway required to accelerate the airplane to takeoff speed. It is possible to overload an airplane to a point where no amount of runway is sufficient to reach takeoff speed. Were it not for forces such as aerodynamic drag and friction of the landing gear against the runway, this would not be true, but these forces are present and limit the performance of the airplane.Reduced Climb Angleincreases in weight must be countered by additional lift. Lift that is otherwise available for climb performance now must support the additional weight. The airplane's capability to out climb obstructions near the airport may be compromised.Reduced Rate of Climbfor the same reason that the angle at which the airplane can climb is reduced, the rate at which it can climb is also reduced. This means more problems if an engine fails during or shortly after takeoff.Lower Ceilingsbecause air density normally decreases as you go up in the atmosphere, there is an altitude at which an airplane climbs no more. This is known as the absolute ceiling of the airplane, and it occurs where the maximum indicated airspeed in level flight is just above stall speed. As the weight of the airplane is increased, the stall speed increases. Accordingly, an increase in weight results in a reduction in absolute ceiling and, in severe situations where there is high terrain, it may be impossible for the airplane to climb above the terrain.Lower Cruising Speedsproduction of additional lift to counteract greater weight results in an increase in drag. This increased drag reduces the speed at which the airplane travels, thereby exacerbating the problem of the increased stall speed.Shorter Range because cruising speeds are reduced by overloading the airplane, the range of the airplane is also reduced. On a trip that calls for most of the airplane's normal range, the destination may prove to be unreachable.Less Maneuverabilitythe heavier the airplane is, the less maneuverable it becomes. This is so because the force necessary to change the speed or direction of an object in motion increases with the mass of the object.Higher Landing Speedsbecause stall speed is higher when the airplane is overloaded, higher approach and landing speeds are necessary.Greater Landing Distanceincreases in touchdown speed increase roll out distance exponentially. Therefore, an increase in weight that requires touchdown at a speed that is only five percent greater than normal may have a significant impact on the required runway length.Aircraft Structure Overloadalthough the primary concern of an overloaded airplane is its effect on aerodynamic performance, a secondary concern is its effect on structural components, such as landing gears.

18Effects Of overloaded airplane1. Increased Take-off SpeedBecause more lift is necessary to counter the additional weight, higher speed is necessary to create sufficient lift to attain flight.

2. Longer Take-off RunThe increase in necessary speed for takeoff and slower acceleration due to increased weight translates to more runway required to accelerate the airplane to takeoff speed. 19MBC 3204 - SIR ARIFF AMCClimb angle:Rate of Climb:Ceilings:Range: Maneuverability:

19Effects Of overloaded airplane3. Lower Cruising SpeedsProduction of additional lift to counteract greater weight results in an increase in drag. This increased drag reduces the speed at which the airplane travels

4.Less ManeuverabilityThe heavier the airplane is, the less maneuverable it becomes. This is so because the force necessary to change the speed or direction of an object in motion increases with the mass of the object.Maneuverability = aircraft ability to turn away from its previous path.

20MBC 3204 - SIR ARIFF AMCEffects Of overloaded airplane5. Reduced Landing PerformanceOverloaded can cause higher approach and landing speeds are necessary. Higher landing speed thus lead to greater landing distance.

6. Aircraft Structure DamageAlthough the primary concern of an overloaded airplane is its effect on aerodynamic performance, a secondary concern is its effect on structural components, such as landing gears.

21MBC 3204 - SIR ARIFF AMCWEIGHT CHANGESItems that contribute to weight changes:Fuel LoadCargo and PassengerEquipment and Modification

Fuel Load The operating weight of an aircraft can be changed by simply altering the fuel load. During flight, fuel burn is normally the only weight change that takes place. As fuel is used, an aircraft becomes lighter and performance is improved.22MBC 3204 - SIR ARIFF AMCContinue. . . Cargo & PassengerThis weight cant be altered during flight.But we can monitor this weight before our journey.

Equipment & ModificationChange of fixed equipment have a major effect upon aircraft weight.Installation extra radios or instrument may affect the weight.Aircraft modification and repairing may contribute to weight change.

23MBC 3204 - SIR ARIFF AMC