Weight and Balance for PPL Exam

ADVANCE FLYING ACADEMY

Weight and Balance for PPL Exam

Weight and balance is a crucial topic for the PPL exam, as it affects the safety and performance of the aircraft. Here’s a breakdown of key concepts and calculations that you’ll need to understand:

1. Basic Terminology

- Basic Empty Weight (BEW): The weight of the aircraft with standard equipment, unusable fuel, and operating fluids.

- Useful Load: The difference between the maximum gross weight and the basic empty weight. This includes usable fuel, passengers, baggage, and cargo.

- Maximum Gross Weight: The maximum weight at which the aircraft is certified to operate.

- Center of Gravity (CG): The point where the aircraft’s total weight is considered to be concentrated.

- CG Limits: The forward and aft limits within which the CG must fall for safe flight.

2. Importance of Weight and Balance

- Safety: If the aircraft is overloaded or the CG is outside limits, it can lead to poor handling characteristics, increased stall speeds, and a higher risk of loss of control.

- **Performance**: Exceeding weight limits can affect takeoff, climb, and landing performance. A CG that's too far forward or aft can also impact stability and control.

3. Weight and Balance Calculation Steps

1. Determine Basic Empty Weight and CG from the aircraft’s weight and balance records.

2. Add Weights for Pilot, Passengers, Fuel, and Baggage:

- Multiply each weight by its arm (the distance from the datum) to get the moment.

3. Calculate Total Weight and Total Moment:

- Add up all weights and all moments.

4. Calculate the CG:

\text{CG} = \frac{\text{Total Moment}}{\text{Total Weight}}

5. **Check CG Limits**:

- Ensure the calculated CG falls within the specified forward and aft limits for your aircraft at the planned weight.

4. Sample Calculation

Imagine you’re flying a Cessna 172 with the following parameters:

- Basic Empty Weight = 1,500 lbs, Moment = 57,000 in-lbs.

- Pilot and Front Passenger Weight = 340 lbs, Arm = 37 in.

- Rear Passenger Weight = 180 lbs, Arm = 73 in.

- Fuel = 40 gallons (1 gallon = 6 lbs), Arm = 48 in.

Steps:

- **Weight and Moment for Pilot/Passenger**: 340 lbs * 37 in = 12,580 in-lbs.

- **Weight and Moment for Rear Passenger**: 180 lbs * 73 in = 13,140 in-lbs.

- **Weight and Moment for Fuel**: 40 * 6 lbs = 240 lbs; Moment = 240 lbs * 48 in = 11,520 in-lbs.

Total Weight = 1,500 + 340 + 180 + 240 = 2,260 lbs

Total Moment = 57,000 + 12,580 + 13,140 + 11,520 = 94,240 in-lbs

- **Calculate CG**:

\text{CG} = \frac{94,240 \text{ in-lbs}}{2,260 \text{ lbs}} \approx 41.7 \text{ in}

- **Check CG Limits** for 2,260 lbs in your POH to confirm if 41.7 inches is within the approved range.

5. Questions to Expect

- How would you correct an aft CG condition?

- What effect does a forward CG have on aircraft performance?

- How do weight and balance affect takeoff, landing, and stall characteristics?

- Can you calculate the new CG after a passenger moves from the rear to the front seat?

Tips for Exam

- Memorize the general process for calculating CG and total weight.

- Be ready to explain the safety implications of improper weight and balance.

- Bring a calculator and the aircraft POH for reference if allowed.

Mastering these steps and understanding their importance will help you excel in the PPL oral exam weight and balance section. Let me know if you need more specific practice examples!

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