Forward CG or Rearward CG?

June 15, 2025

好耐無溫書，曾經作為load control，一定會比人問同埋要考慮load頭定load尾好，by rule of thumb, 我果陣普遍幫佢裝頭，點解？係時候溫返書～

一齊睇下AI分析先：

Forward CG:

Increased Stability:A forward CG means the aircraft’s center of gravity is closer to the nose, leading to a more stable flight. The aircraft is more resistant to pitching up or down, and it’s easier to maintain a desired attitude.
Easier Stall Recovery:The increased stability from a forward CG makes it easier to recover from stalls, as the nose tends to drop naturally when the aircraft slows down.
Higher Drag and Stall Speed:A forward CG results in a higher angle of attack (AOA) to maintain level flight, leading to increased drag and a higher stall speed. This means the aircraft needs to fly faster to generate enough lift.

Aft CG:

Reduced Stability:An aft CG means the center of gravity is further back, making the aircraft less stable. It becomes more sensitive to control inputs and more susceptible to stalling, especially at slower speeds.
Increased Risk of Stall:With an aft CG, the aircraft is more prone to stalling, and recovery can be more challenging, requiring more control input and potentially a higher sink rate.
Reduced Drag and Stall Speed:Aft CG can reduce drag and stall speed, potentially improving performance in some phases of flight, but this is a trade-off for reduced stability.

In Summary: While a forward CG might be considered safer due to increased stability, pilots must balance this with the potential for increased drag and stall speed. Understanding the effects of both forward and aft CGs is crucial for safe and efficient flight operations.

Airbus 文章撮要：

Sure! Here’s a summarized bullet point version of the key concepts regarding weight and balance in aviation:

Understanding Weight & Balance

Importance of CG (Center of Gravity):
CG affects aircraft response through flight controls; incorrect CG can lead to safety issues.
CG position is critical for stability and maneuverability.
Safety Incidents Linked to Weight & Balance:
Tail Strikes: Caused by incorrect CG after passenger and luggage loading.
Unexpected Pitch-Up: Cargo shifting aft during climb led to loss of control.
Tipping on Tail: Incorrect unloading sequence due to inadequate training.
Take-off Issues: Incorrect weight entry led to a tail strike.
Stall and Crash: Load shift caused violent pitch-up after take-off.
Statistics:
21% of accidents due to overweight.
35% due to CG exceeding certified limits.

Forces Acting on Aircraft

Weight: Acts at the CG.
Lift: Acts at the Center of Pressure (CP), which is behind the CG.
Pitch Moments: The distance between CG and CP creates a pitch-down moment needing compensation from the Trimmable Horizontal Stabilizer (THS).

Effects of CG Position

Forward CG:
Increased pitch-down moment affects maneuverability and performance.
Difficulty in achieving correct take-off rotation.
May exceed nose landing gear structural limits.
Aft CG:
Increased pitch-up moment during go-arounds and take-off.
Reduced nose wheel control, especially on wet runways.
Risks exceeding structural limits on main landing gear.

Ensuring Safe CG Throughout Flight

Operational Envelope: Define CG limits with safety margins.
Weight Variations: CG changes during flight due to fuel consumption and passenger movements.
Measurement Challenges: No robust systems to measure CG in real-time.

Safety Margins and Assumptions

Factors Affecting CG Calculation:
Dry operating weight assumptions.
Average passenger weights.
Last-minute changes in loading.
In-flight configuration changes (flaps, landing gear).
Fuel weight and distribution inaccuracies.

Free Seating Implications

Impact on CG: Unknown passenger seating may lead to CG discrepancies.
Cabin Sectioning: Essential to model passenger distribution for accurate CG calculations.

Last Minute Changes

Loading Decisions: Last-minute cargo can affect weight and CG.
Impact Assessment: Calculate maximum impact of last-minute changes and integrate into safety margins.