Aircraft Weight & Balance

Weight & balance is important for both the saftey of the aircraft as well as it effiency (fuel consumption, & manauvorability).

- In extreme cases it can cause loss of life due to load shift

The focus of the investigating appears to be pointing toward whether the Cessna 172 was flying too low and too slow while on a mission to observe and count wading birds. “I couldn't believe he was flying like this at 300 feet,” Kelting said. “He was definitely in trouble. He was too low just before stalling the air plane ... I knew something was definitely wrong. I knew if he wasn't careful he was going to crash.” Another possible factor was the aircraft’s weight and balance - and whether it was loaded within limits, Tichy said. With four people on board, it’s possible it was either overloaded or its center of gravity was not within "the operating envelope," he said.

The commuter plane was not able to maintain altitude after taking off from Charlotte-Douglas International Airport and crashed into the side of a hanger and burst into flames. The airplane's loss of pitch control during takeoff was the result of incorrect rigging of the elevator control system compounded by the airplane's center of gravity, which was substantially aft of the certified aft limit. Date: January 08, 2003 Location: Charlotte, North Carolina Aircraft: Beech BE-1900D Reg: N233YV Airline: US Air Express/Air Midwest Flight No: 5481 Fatalities: 21 : 21

Singer/actress Aaliyah Haughton was killed, along with eight others, when the Cessna 402 she was flying on crashed while attempting to take off from Abaco Island, Bahamas. The plane was overloaded. Date: August 25, 2001 Location: Marsh Harbour, Bahamas Aircraft: Cessna 402B Reg: N8097W Airline: Blackhawk Int. Airways Flight No: N/A Fatalities: 9 : 9

The pilot of this turbo otter lost elevator control & crashed. No one was injured The aircraft was loaded in such a manner that the C of G was beyond the rearward limit. This resulted in the aircraft’s aerodynamic pitch control limitation being exceeded. A weight and balance report was not completed by the pilot prior to departure; consequently, he was unaware of the severity of the aft C of G position. Finding as to risk The weight of the passengers was underestimated due to the use of standard weights. This increased the potential of inadvertently loading the aircraft in excess of its maximum certified take-off weight (MCTOW).

The empty W & B and corresponding c of g are determined by the manufacturer at the time of certification

-Aircraft can gain weight ( dirt , grease, etc) over time so reweighing of the aircraft is set out by the manufacturer and Transport Canada.

- The theory of W & B , weight is distributed equally on both sides of the fulcrum. So 1lb on a 2 ft arm would balance a 2lb weight on a 1 ft arm. A lite weight far from the fulcrum is the same as a heavy weight close to the fulcrum - the LEVER ARM x the WEIGHT = THE MOMENT

Another example below

Center of gravity (C of G) is a point from which the a/c is perfectly balanced - See fig 3-1 ( pg 53 of A & P general mechanics handbook) This shows the a/c hanging from it's C of G. The weight must be distributed equally for and aft to keep the c of g within it's range specified by the manufacturer

When any equiptment is added or removed the W & B is changed and must be calculated and adjusted.. Eg.....If you put a new radio system in the a/c this may change the C of G. -The w& b Data can be found in the 1) aircraft specifications, 2) aircraft operating limitations, 3) aircraft flight manual, 4) a/c w & b report.

-The datum is an imaginary vertical plane from which all horizontal measurments are taken. It is at the right angle to the longitudinal axis of the a/c. -This is determined differently for each a/c & is a way for the manufacturer to show locations of the seats , baggage, engines and propellers. This is recorded in the type certificate data sheet. -Usually the datum is in the nose of the a/c

-The datum becomes the fulcrum

-The arm is the horizontal distance that an item is away from the datum. The location is given in inches & either a (+) for aft of the datum or a (-) for forward of the datum will be shown. eg... Seat (+23) means 23 inches aft of the datum.

The maximum weight is the fully loaded weight of the A/C

Empty Weight --Includes all equiptment, hydrolic fluid, and residual oil and fuel (left in the lines)

Useful Load - the difference between the max weight and the empty weight. It includes the flight crew, the passengers and their baggage, the seats, max fuel and oil.

The (EWCG) empty weight C of G and it’s range {which is specified by the manufacturer } is not useful in itself except as a starting point for all calculations Correctly balanced Badly balanaced--tail heavy

-The operating C of G range given in the A/C specifications are determined at the time of design. -The loaded A/C’s center of gravity must be within this range at all times

When weighing a small to medium A/C usually the wheels are placed on scales and the weight is read from axel point Larger A/C can be weighed at their jacking points

When it is needed ballast can be placed in the aircraft (usually in the tail) to help put the C of G back in limits Mostly lead is used but sometimes depleted uranium is used as a ballast as it is very dense

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