AVAT11001: Course Outline 1.Aircraft and Terminology 2.Radio Communications 3.Structure, Propulsion, Fuel Systems 4.Electrical, Hydraulic Systems and Instruments 5.Air Law 6.Aerodynamics: Basics 7.Aerodynamics: Performance 8.Human Factors 9.Meteorology 10.Loading 11.Take-off and Landing Performance 12.Navigation

Stuff to read Required Reading: –BAK Chapter 10, pp –VFG PREP, pp.35-52

Terminology Mass and Weight –Mass is the amount of matter in an object –Weight is the force associated with the mass that is caused by gravity –Kilograms is a unit of mass Unfortunately, it is common usage to refer to an object as having a “weight” of so many kilograms Be sure you understand all the different weights described on pages

Weight Limits Structural –Some of the weight limits imposed on aircraft are based upon how much weight the structure of the airframe has been designed to support MTOW – the wings can only carry so much load MLW – the landing gear can only resist some much impact Performance –Some of the weight limits are based upon how well the aircraft can climb or manoeuvre when its mass is increased. There can be take-off or landing weight restrictions, which will be studied briefly next week and in more detail in AVAT12004

Weight and Performance A heavier aeroplane will have reduced performance capabilities. For example: –Higher stall speed –Higher take-off speed and longer take-off run –Lower climb angle and smaller climb rate –Lower service ceiling –Less manoeuvrability –Higher fuel consumption Less range and less endurance –Reduced cruise speed for a given power setting –Higher landing speed and longer landing distance –Greater braking requirements when stopping

Moments and Balance Recall from Week 6 that a moment is generated when a force acts at a distance from the point of rotation, such as a pivot point. A system is said to be balanced if the summation of all the moments about a particular pivot point is zero. –See Figures 10-7 and 10-8 page 317

Centre of Gravity Properties of the CG –This is the point of balance for an object See Figure 10-9 page 318 –This is the point where you can assume the weight is acting See Figure page 318 –When in the air, this is the point about which the object will rotate when moments are applied

CG Limits, part 1 On the ground –The distance between the CG and the landing gear affects how much moment is required to rotate the aircraft –If the CG is too far aft, the aircraft may tip over See Figure 10-2 page 314 –If the CG is too far forward, it may be difficult to rotate for take-off Weight would cause a nose-down moment that would need to be overcome

CG Limits, part 2 In the air –The distance between the CG and the aerodynamic surfaces (wings, elevator, etc) affect the stability and control of the aircraft A CG too far aft may make the aircraft unstable. –This increases pilot work load. –Also, the aircraft may be impossible for the pilot to control. A CG too far forward may prevent you from trimming the aircraft or manoeuvring. –The elevator typically must counter the moment produced by the wing. –If the CG is far from the centre of pressure of the wing, the elevator may not be able to over come the moment the wing produces. –See Figure page 318

Finding the CG, part 1 You can find the CG by summing the moments produced by the weight of the various components. To do this, you need to pick the point about which you will compute the moments –Remember, a moment is equal to the force multiplied by the moment arm. –The point used as a reference point in CG calculations is called the “datum” point. –It doesn’t make any difference which point is used as the datum point (i.e. nose of the aircraft, the location of the firewall behind the engine, etc) as long as it is clearly defined

Finding the CG, part 2 Once the datum is defined, multiply each weight by the appropriate moment arm –See Figure page 321 Sum up all the weights to get the total weight Sum up all the moments to get the total moment If you divide the total moment by the total weight, you will get the location of the CG relative to the datum –If all the mass were concentrated at this point, its weight would produce the same moment about the datum You must check where the CG will be for the entire flight. –Since the CG changes when fuel is burned, you must check at least 2 points: TOW and ZFW

Loading Systems, Differences There are several different methods of helping pilots to compute CG locations These are called loading systems The different systems present the same information in different formats –Typically, there is some combination of graphs and tables –See pages 328 thru 331 Some systems compare weight to CG location –See Figure page 331 Some systems compare weight to moment about the datum –See Figure page 329

Loading Systems, Similarities No matter how the information is presented the procedure is roughly the same: –Find the total weight –Find the total moment –CG = total moment/total weight You will need to be familiar with the different methods, because different aircraft manufacturers present the information in different ways. –If you practice using the different systems, you will be able to quickly and accurately use the information in any operating handbook.

Loading System Alpha See Figure page 328 You enter the weights for different locations in the right hand column. Start at the index units associated with the basic empty weight. Move left or right as you move down, following the directions on each line Check the full and empty weights on the allowable envelope at the bottom.

Loading System Bravo See Figure page 329 Use the moment arms given in the table to get the moment associated with the empty weight and the oil. For the other loading locations, you can either use the arms given in the table, or use the loading graph. Check if the CG is within the required envelope using the weight (lbs) and total moment (index units)

Loading System Charlie See Figures and pages 330 and 331 Start with a known aircraft empty weight and the corresponding moment index units. For the other loading locations, you can either use the arms given in the table, or use the table data (interpolating as required). Check if the CG is within the required envelope using the weight (kg) and CG location (mm).

Changing the CG What do you do if you find the CG is outside the valid envelope? You have 3 options: –Shift payload Sometimes you can get the CG within the envelope by rearranging some passengers or cargo –Remove payload Sometimes you will be unable to carry all the payload in a single flight, and you will have to remove some of it –Add payload Sometimes you can get the CG in the right place by adding weight in the right locations

For example… If the CG is too far aft, you could –Move people or baggage forward –Remove weight from locations aft of the desired CG location –Add weight to locations forward of the desired CG location If the CG is too far forward, you could –Move people or baggage aft –Remove weight from locations forward of the desired CG location –Add weight to locations aft of the desired CG location

CG Change Calculations Load to shift = (GW x change of CG)/(distance moved) Load to add = (GW x change of CG)/(distance between new CG and where you add the weight) Load to remove = (GW x change of CG)/(distance between new CG and where you remove the weight) When computing the load to add or remove, the GW is the weight before you add or remove any load –When shifting, the GW does not change

For next week… Required Reading: –BAK Chapter 11, pp –VFG EMERG, pp