航空专业英语教学课件：Weight and Balance

1、Weight and BalanceWhy do we need to learn about weight and balance?It affects performance Affects how much fuel you burnImproper weight and balance can keep you from taking off, recovering from a stall, clearing obstacles, or reaching your airportWill be necessary to know for flight training and at

2、the airlineObjectives Weight and balance termsHow to determine your CGEffect of weight and balance on performanceWeight termsEffects of weight on performanceEffects of weight on airplane structureMethods of weight and balance controlHow to find CG after shifting weightHow to find CG after adding or

3、removing weightWeight and balance termsDatum An imaginary line from which measurements called arms are takenWeight and balance termsStationA location in the airplane identified by a number of inches or meters from the datumThe datum is at station 0Weight and balance termsArmThe horizontal distance i

4、n inches or meters from the datum line to the station of an itemThe arm is positive if its behind the datum and negative if its in front of the datumWeight and balance termsMomentThe product of weight multiplied by the armExpressed in pound-inches or kilogram-metersWeight and balance termsCenter of

5、gravityThe point about which the plane would balance if it were possible to suspend itCan be expressed as inches, meters, or mean aerodynamic chordWeight and balance termsCG envelopeSpecified forward and aft points that the CG must stay within for a given weightHow to determine your cgWeight * Arm =

6、 MomentTotal moment = CG Total weightMoms overweightFind the cgWeightArmMomentEmpty WeightPilot and PassengerBaggageTotal weight with empty tanksUseable fuelTotal weight with fuelFind the cgEmpty weight is 1153 lbs with a moment of 12562 lb-inRon is flying to Hogwarts. He weighs 170 lbsHarry is his

7、passenger he weighs 160 lbsThey sit at 5.6 inchesThey carry their suitcases full of robes, wands and potions in the baggage compartment and they weigh 40 lbs totalThe bags are at 47.2 inchesTheyre carrying 15 gallons of fuelThe fuel is at 32.44 inchesIs the CG within limits?WeightArmMomentEmpty Weig

8、ht115312562Pilot and Passenger3305.61848Baggage4047.21888Total weight with empty tanks152316298Useable fuel9032.442919.6Total weight with fuel161319217.6Find the cgEmpty weight is 1153 lbs with a moment of 12562 lb-inRose is flying the airplane with Jack. Rose weighs 140 lbs. Jack weighs 175 lbsThey

9、 sit at 5.6 inchesTheyre carrying everything they needfor a new life in New York and it weighs 35 lbsThe bags are at 47.2 inThey have 11 gallons of fuel onboardThe fuel is at 32.44 inIs the CG within limits?WeightArmMomentEmpty Weight115312562Pilot and Passenger3155.61764Baggage3547.21652Total weigh

10、t with empty tanks150315978Useable fuel6632.442141.04Total weight with fuel156918119.04Find the cgEmpty weight is 1153 lbs with a moment of 12562 lb-inBatman and Robin are flying from Gotham to Disney WorldBatman weighs 100lbs and Robin weighs 105 lbsThey sit at 5.6 inThey 100 lbs of bagsThe bags ar

11、e at 47.2 inhesTheyre carrying 13 gallons of fuelThe fuel is at 32.44 inIs the CG within limits?WeightArmMomentEmpty Weight115312562Pilot and Passenger2055.61140Baggage10047.24720Total weight with empty tanksUseable fuel7832.442530.32Total weight with fuel153620952.322.8. CENTER OF GRAVITY The refer

12、ence datum (RD) for the center of gravity (CG) calculation is tangent to the leadingedge of the wing at the root rib. This plane is vertical when the fuselage is horizontal.Procedures for horizontal alignment, as well as particulars with regard to the empty weightcenter of gravity, refer to Chapter

13、6. Most forward CG (all weights) : 7.96 in (202 mm) aft of RD. Most rearward CG (all weights) : 12.49 in (317 mm) aft of RD. Forward cgAirplane is more stableIf the pitch is disturbed, the plane will recover to straight and levelForward cgControllability Arm from the rudder to the CG is longerMore r

14、udder effectivenessMore controllable with respect to yawSince so much up elevator is already required, can run out of elevator effectivenessHave to hold a nose high elevator attitude just to maintain straight and levelMight not be able to pitch up as much as necessaryForward cgHigher stalling speedH

15、olding the nose up requires a greater tail down forceThis makes the airplane “heavier” which means we need more liftIn order to create more lift we must do what to our AOA?Increase itPlane stalls at the critical AOA, youll be closer to it if you already have to keep a high AOA to create liftForward

16、cgBetter stall characteristicsCan get the nose down very easily to recoverSlower cruising speed at a given power settingCaused by the drag from having a high AOADecreased range and enduranceIncreased fuel consumption at a given airspeedAft cgAirplane is less stableIf the pitch is disturbed, the plan

17、e may continue to oscillateAft cgControllabilityArm from the rudder to the CG is shortControllability with respect to yaw is decreasedMore elevator effectivenessNot necessary to hold as much if any elevator pressure to stay straight and levelAft cgLower stalling speedLess tail down force is required

18、 which means a “lighter” airplaneLess lift required so AOA is lowerKeeps you away from critical angle of attackAft cgWorse stall characteristicsMay not be able to get the nose downFaster cruising speed at a given power settingSince AOA required is small, there is less dragLonger range and enduranceL

19、ess fuel used at a given airspeedWeight termsStandard empty weightAll operating systems permanently installed on the airplaneIncludes hydraulic fluid, unusable fuel, and full engine oilBasic empty weightStandard equipment plus optional equipmentMx-20 Weight termsMax zero fuel weightMaximum weight wi

20、th no fuel aboardProtects the wings from being overstressedToo much weight means the wings have to produce too much lift and can be stressedAlso might not be able to take off if too heavyWeight termsMax ramp weightTotal weight of a loaded plane with fuelHigher than max takeoff weightMax takeoff weig

21、htMax allowable weight for takeoffMax landing weightMax weight allowed for landingProtects landing gear2.7. WEIGHT Maximum Ramp Weight : 1660 (753 kg) Maximum Take-Off Weight : 1653 lbs (750 kg) Maximum Landing Weight : 1653 lbs (750 kg) Maximum permissible weight : 44 lbs (20 kg) only permissible i

22、n the baggage compartment with baggage harness WARNING EXCEEDING WEIGHT LIMITATIONS MAY LEAD TO OVERLOADING OF THE AIRPLANE AND CAUSE LOSS OF CONTROL OF THE AIRPLANE AND/OR STRUCTURAL DAMAGE. Weight termsUseful loadRequired crew, bags, useable fuel, and drainable oilMax takeoff weight basic empty we

23、ight = useful loadMax takeoff weight all required equipment = how much weight in the form of fuel, baggage, cargo and people you can haveIf max takeoff weight is 1653 lbs and BEW is 1000 lbs, how much useful load can you take?Weight termsPayloadPassengers, baggage, and cargoZero fuel weight basic em

24、pty weight = payloadWant to max out your payloadEffects of weight on performanceLonger takeoff runLonger landing distanceMore momentum than a lighter airplaneSame as with a car and a motorcycleShallower climbNeed to keep the nose down to maintain airspeedReduces angle and rate of climbEffects of wei

25、ght on performanceReduced cruising speedHigh AOA required just like with forward CGCreased more drag which reduces cruising speedShorter rangeCreating more drag so more thrust is required to overcome itWill burn more fuel trying to maintain airspeedEffects of weight on performanceManeuverability is

26、decreasedAbility to change direction while withstanding the stresses imposed on the planeCant change course quickly Might not be able to pitch up or add power so turns must be shallowEffects of weight on airplane structureYour airplane weighs 3,000 lbs at straight and levelYou do a 60 turnWhat happe

27、ns to load factor?How heavy does the plane feel?Methods of weight and balance controlHow can we control our weight and CG location?Take less fuelTake fewer peopleDont take baggageTake fewer bagsImpose a weight restriction on bagsIf the weight is fine but CG is out of limits, move thingsRemember not to exceed weight limits for each stationHow to find cg after shifting weightYou decide to move a bag from the seat to baggage. Now what?You could recompute the w