Weight And Balance 1

Question 1

Define arm, datum, moment

Answer 1

Arm - horizontal distance from a reference datum to the CoG, aft = positive, forward = negative

Datum - point from which all measurements are taken and is determined by the manafacturer.

Moment - the turning effect about a point, depends on the size of the force (kg) and the moment arm (mm) (Kgmm)

Question 2

Define CoG, longitudinal range and limits of CG, station, index units,

Answer 2

CoG - the point where all weight of the aircraft acts, all three axes run through this point and is the balance point of the aircraft.

Limits - CoG will change according to weight distribution, must be kept within these limits for it to be stable.

Station - reference to datum, STA 0 is the datum

Index units - when numbers are too big, divide by 10,000. 1 IU = 10,000kg-mm

Question 3

Define BEW, empty weight centre of gravity position, Aircraft prepared for service weight/Basic operating weight, payload

Answer 3

BEW - empty weight incl airframe, engine, unusual fuel, full oil and hydraulics

CoG position - position of the aircraft at BEW, calculated by engineers

APSW - includes BEW, pilot and crew, crew baggage, food. Or total load minus payload and fuel

Payload - commercial load, includes passengers baggage and freight.

Question 4

Define Zero fuel weight, MZFW, ramp weight, gross weight (AUW), take off weight, landing weight

Answer 4

ZFW - APSW + payload

MZFW - a limitation for some aircraft due to weight fuel in the wings of an aircraft applying a downward force which counters the stress caused by the lifting force of the wings.

Ramp weight - max gross allowed prior to taxi, may be higher than the MTOW. ZFW plus fuel

Gross weight - total weight of aircraft at any time, cannot exceed allowable weight for a given manoeuvre

Takeoff weight - gross weight at takeoff

Landing weight - gross weight at landing

Question 5

define MCTOW, MCLW, CoG envelope, specific gravity, specific gravity and weight of fuel of AvGAS or jet A-1

Answer 5

MCTOW - maximum weight aircraft can be at takeoff

MCLW - maximum weight aircraft can be at landing

Specific gravity - AvGas taken to have a SG of 0.72. Avtur 0.79.

Question 6

Explain the principles of aeroplane balance.

Answer 6

Lift acts through the Centre of Pressure (CP), Weight acts through the Centre of Gravity (CG) forming a nose-down couple. Thrust and drag form a nose-up couple

Question 7

Explain the function of the tailplane in providing the final longitudinal balancing force.

Answer 7

The tailplane balances residual pitching moments, Both the CP and the CG move in flight

Question 8

Describe the effect on longitudinal stability and resultant handling issues with the aeroplane loaded with the centre of gravity:

(a) forward;
(b) outside the forward limit;
(c) aft;
(d) outside the aft limit.

Answer 8

(A) stable longitudinally - nose heavy
(B) nose heavy, T/O and landing problems, harder to hold an attitude
(C) less stable longitudinally - tail heavy
(D) tail heavy, Stick forces too light, lack of forward elevator authority.

Question 9

Explain the significance of lateral fuel imbalance and the limitations typically applied.

Answer 9

Lateral fuel imbalance occurs when one wing has more fuel than the other, causing it to be heavier, causing the wing to drop, and the pilot will need to use aileron to raise that wing.

aircraft are often designed with a “cross feed” system, which lets fuel flow from one tank to the other over time. it is important to remember to change tanks every 30 minutes or so

Question 10

Explain the expected effect of fuel burn on the centre of gravity position.

Answer 10

Fuel tanks have an arm and so fuel usage will cause a change in an aircraft’s CG.

If your fuel tank/s are aft of the aircraft CG, as fuel is used the CG will move forward.

Using fuel from the inner wing tanks will cause the CG to shift aft

Question 11

How many US Gall = L

How many pounds to kg

Answer 11

3. 78 L = 1 US Gall

2. 2 lb = 1kg