5D - Performance and Limitations - Weight and Balance Flashcards
- If the weight and balance of an aircraft has changed due to the addition or removal of fixed equipment in the aircraft, what responsibility does the owner or operator have?
The owner or operator of the aircraft should ensure that maintenance personnel make appropriate entries in the aircraft records when repairs or modifications have been accomplished. Weight changes must be accounted for and proper notations made in weight and balance records. The appropriate form for these changes is “Major Repairs and Alterations” (FAA Form 337).
- What performance characteristics will be adversely affected when an aircraft has been overloaded? (FAA-H-8083-25)
a. Higher takeoff speed.
b. Longer takeoff run.
c. Reduced rate and angle of climb.
d. Lower maximum altitude.
e. Shorter range.
f. Reduced cruising speed.
g. Reduced maneuverability.
h. Higher stalling speed.
i. Higher landing speed.
j. Longer landing roll.
k. Excessive weight on the nosewheel.
- Define the term “center of gravity.” (FAA-H-8083-25)
The center of gravity (CG) is the point about which an aircraft would balance if it were possible to support the aircraft at that point. It is the mass center of the aircraft, or the theoretical point at which the entire weight of the aircraft is assumed to be concentrated. The CG must be within specific limits for safe flight.
- DUPLICATE*
4. What effect does a forward center of gravity have on an aircraft’s flight characteristics? (FAA-H-8083-25)
Higher stall speed—Stalling angle of attack reached at a higher speed due to increased wing loading.
Slower cruise speed—Increased drag, greater angle of attack required to maintain altitude.
More stable—The center of gravity is further forward from the center of pressure, which increases longitudinal stability.
Greater back elevator pressure required—Longer takeoff roll, higher approach speeds and problems with the landing flare.
- DUPLICATE*
5. What effect does an aft center of gravity have on an aircraft’s flight characteristics? (FAA-H-8083-25)
Lower stall speed—Less wing loading.
Higher cruise speed—Reduced drag, smaller angle of attack required to maintain altitude.
Less stable—Stall and spin recovery more difficult; when angle of attack is increased it tends to result in additional increased angle of attack.
6. Define the following: • Arm • Basic empty weight (GAMA) • Center of gravity • Center of gravity limits • Center of gravity range • Datum • Floor load limit • Fuel load • Licensed empty weight • Maximum landing weight • Maximum ramp weight • Maximum takeoff weight • Maximum weight • Maximum zero fuel weight (GAMA) • Mean aerodynamic chord • Moment • Moment index • Payload (GAMA) • Standard empty weight (GAMA) • Station • Useful load (FAA-H-8083-25)
Arm—The horizontal distance in inches from the reference datum line to the center of gravity of an item.
Basic empty weight (GAMA)—The standard empty weight plus optional and special equipment that has been installed.
Center of gravity—The point about which an aircraft would balance if it were possible to suspend it at that point, expressed in inches from datum.
Center of gravity limits—The specified forward and aft or lateral points beyond which the CG must not be located during takeoff, flight or landing.
Center of gravity range—The distance between the forward and aft CG limits indicated on pertinent aircraft specifications.
Datum—An imaginary vertical plane or line from which all measurements of arm are taken. It is established by the manufacturer.
Floor load limit—The maximum weight the floor can sustain per square inch/foot as provided by the manufacturer.
Fuel load—The expendable part of the load of the aircraft. It includes only usable fuel, not fuel required to fill the lines or that which remains trapped in the tank sumps.
Licensed empty weight—The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization.
Maximum landing weight—The maximum weight at which the aircraft may normally be landed. The maximum landing weight may be limited to a lesser weight when runway length or atmospheric conditions are adverse.
Maximum ramp weight—The total weight of a loaded aircraft, and includes all fuel. It is greater than the takeoff weight due to the fuel that will be burned during the taxi and runup operations. Ramp weight may also be referred to as taxi weight.
Maximum takeoff weight—The maximum allowable weight at the start of the takeoff run. Some aircraft are approved for loading to a greater weight (ramp or taxi) only to allow for fuel burnoff during ground operation. The takeoff weight for a particular flight may be limited to a lesser weight when runway length, atmospheric conditions, or other variables are adverse.
Maximum weight—The maximum authorized weight of the aircraft and all of its equipment as specified in the Type Certificate Data Sheets (TCDS) for the aircraft.
Mean aerodynamic chord (MAC)—The average distance from the leading edge to the trailing edge of the wing. The MAC is specified for the aircraft by determining the average chord of an imaginary wing which has the same aerodynamic characteristics as the actual wing.
Moment—The product of the weight of an item multiplied by its arm. Moments are expressed in pound-inches.
Moment index—A moment divided by a constant such as 100, 1,000, or 10,000. The purpose of using a moment index is to simplify weight and balance computations of large aircraft where heavy items and long arms result in large, unmanageable numbers.
Payload (GAMA)—The weight of occupants, cargo, and baggage.
Standard empty weight (GAMA)—The airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed in the airplane; including fixed ballast, hydraulic fluid, unusable fuel, and full engine oil.
Station—A location in the aircraft which is identified by a number designating its distance in inches from the datum. The datum is, therefore, identified as station zero. The station and arm are usually identical. An item located at station +50 would have an arm of 50 inches.
Useful load—The weight of the pilot, copilot, passengers, baggage, usable fuel and drainable oil. It is the empty weight subtracted from the maximum allowable takeoff weight. The term applies to general aviation aircraft only.
- What basic equation is used in all weight and balance problems to find the center of gravity location of an airplane and/or its components? (FAA-H-8083-25)
Weight x Arm = Moment
By rearrangement of this equation to the forms,
Weight = Moment ÷ arm.
Arm = Moment ÷ weight.
CG = Moment ÷ weight.
With any two known values, the third value can be found.
- What basic equation is used to determine center of gravity? (FAA-H-8083-25)
Center of gravity is determined by dividing total moments by total weight.
- Explain the term percent of mean aerodynamic chord (MAC). (FAA-H-8083-1)
Expression of the CG relative to the MAC is a common practice in larger aircraft. The CG position is expressed as a percent MAC (percent of mean aerodynamic chord), and the CG limits are expressed in the same manner. Normally, an aircraft will have acceptable flight characteristics if the CG is located somewhere near the 25% average chord point. This means the CG is located one-fourth of the total distance back from the leading edge of the average wing section.
- If the weight of an aircraft is within takeoff limits but the CG limit has been exceeded, what actions can the pilot take to correct the situation? (FAA-H-8083-25)
The most satisfactory solution to this type of problem is to shift baggage, passengers, or both in an effort to make the aircraft CG fall within limits.
- When a shift in weight is required, what standardized and simple calculations can be made to determine the new CG? (FAA-H-8083-25)
A typical problem may involve calculation of a new CG for an aircraft which has shifted cargo due to the CG being out of limits.
Given:
Aircraft total weight = 6,680 pounds
CG = Station 80.0
CG limits = Station 70-78
Find: What is the location of the CG if 200 pounds is shifted from the aft compartment at station 150 to the forward at station 30?
Solution:
See book
This same formula may be used to calculate how much weight must be shifted when you know how far you want to move the CG to come within limits
- If the weight of an aircraft changes due to the addition or removal of cargo or passengers before flight, what formula may be used to calculate new CG? (FAA-H-8083-25)
A typical problem may involve the calculation of a new CG for an aircraft which, when loaded and ready for flight, receives some additional cargo or passengers just before departure time.
Given:
Aircraft total weight = 6,860 pounds
CG = Station 80.0
Find: What is the location of the CG if 140 lbs. of baggage is added to station 150?
Solution:
a. Use the added weight formula:
See book
CG change = 1.4 inches aft
b. Add the CG change to the old CG:
New CG = 80.0 in. + 1.4 in. = 81.4 in.
By using “old total weight and new CG,” this same formula may be used to find out how much weight to add or remove, when it is known how far you want to move the CG to come within limits.
- What simple and fundamental weight check can be made by all pilots before flight? (FAA-H-8083-25)
A useful load check can be made to determine if the useful load limit has been exceeded. This check may be a mental calculation if the pilot is familiar with the aircraft’s limits and knows that unusually heavy loads are not aboard. The pilot needs to know the useful load limit of the particular aircraft. This information may be found in the latest weight and balance report, in a logbook, or on a Major Repair and Alteration Form located in the aircraft. If the useful load limit is not stated directly, simply subtract the empty weight from the maximum takeoff weight.
- What factors would contribute to a change in center of gravity location during flight?
The operator’s flight manual should show procedures which fully account for variations in CG travel during flight caused by variables such as the movement of passengers and the effect of the CG travel due to fuel used.
- If actual weights for weight and balance computations are unknown, what weights may be assumed for weight and balance computations? (FAA-H-8083-25)
Some standard weights used in general aviation are:
Crew and Passengers—170 lbs./person
Gasoline—6 lbs./U.S. gal.
Oil—7.5 lbs./U.S. gal.
Water—8.35 lbs./U.S. gal.
Note: These weights are not to be used in lieu of available actual weights!
