The Top 10 Actual Transmissions Made in the O’Hare TRACON
The Top 10 Actual Transmissions Made in the O’Hare TRACON
Terms
Reference datum- imaginary vertical plane from which all horizontal distances are measured
Station- a designated location on the fuselage measured from the reference datum
Terms
Empty weight- the weight of the aircraft with all the necessary equipment installed does not include people or baggage
Basic empty weight- the weight of the aircraft with all equipment, oil and unusable fuel does not include people or baggage
Terms
Max ramp weight- max weight of aircraft for taxi operations (it includes start taxi and runup fuel)
Max takeoff weight- max weight approved for the start of the takeoff run
Terms
Useful load- difference between take off weight and basic empty weight
Payload- weight of the occupants, cargo and baggage
Zero fuel weight- weight exclusive of usable fuel useful for calculations when fuel is a variable
Terms
Tare- weight of chocks, blocks, stands ect used when weighing an aircraft
Arm- the horizontal distance from the reference datum
Moment- the force exerted by a weight using an arm usually measured in in/lbs or foot/lbs
Terms
Center of gravity- the point at which an airplane would balance if suspended from that point
Principles Of Weight And Balance
Principles Of Weight And Balance
Useful Facts
Fuel weighs 6lbs per gallon
Oil weighs 7.5lbs per gallon
That’s 1.875lbs per quart
Weight x Arm = Moment
Where Do I Start?
Start by finding the Basic Empty Weight, Arm and Moment
Located in the Aircraft POH (Weight and Balance Chapter) in that particular airplane
BEW = 1520.85 lbs
ARM = 111.71 inches
MOM = 1698.94
Second Step, Front Seats
170@108 and 190@112
Third Step, Rear Seat
10@142
Fourth Step, Usable Fuel
40-2.6=37.4 gallons
Be Aware!
Note: the baggage and rear seat are the same arm
Fifth Step
Subtract out fuel for taxi and takeoff
We use 1 gallon or 6 lbs
Where’s The Beef?
Find your weight and see if your moment is within the two moment values listed
For takeoff W=2109.25 M=2365.07
For landing W=2037.25 M=2280.83
The Cessna Way
Always read the fine print!
High Gross Weights
Longer takeoff run
Shallower climbs
Faster touchdown speed
Longer landing roll
Overheating in climb
High Gross Weights
Added wear on engine
Increased fuel consumption
Slower cruising speeds
Reduced range
High Gross Weights
It is a violation of FAR’s to exceed gross weight limits
Limit load factors normal 3.8 -1.52 utility 4.4 -1.76 aerobatic 6.0 -3.0
These can be exceeded easily if overloaded
High Gross Weights
For example,2150 lbs. At 3.8 g’s is 8170 lbs.
At 100lbs over gross, 2250 at 3.8g’s is 8550
For a difference of 380 lbs!
Stall, spin, die
High Gross Weights
Over loading may accelerate metallic fatigue failures
Baggage floor may have limits on weight for structural reasons
Stability may be effected to the negative if overloaded
High gross weights
The higher the gross weight the higher the stall speed
Less reserve angle of attack
Load distribution
Safety
Manufacturer sets limits for controllability and maneuverability
Certification procedures demand a certain amount of oscillations before dampening out this determines where the aft cg is located
W&B Aerodynamics
Tail down force
Forward cg gives:
Higher stall speed,
Higher elevator control forces (critical in takeoff and landing phase),
W&B Aerodynamics
Slower cruise,
More overall stability,
Longer takeoff and landing distance,
With an aft cg recovery from a stall spin harder or impossible.
Opposites are true for aft cg