Precision in Aviation: Mastering Weight & Balance Calculations

Accurate weight & balance calculations are a mission-critical safety issue in aviation. When done incorrectly, the results can be nothing short of disastrous. One example of this is Air Midwest Flight 5481.

On the morning of January 8, 2003, Flight 5481, a Beechcraft 1900D, took off on a regular scheduled passenger flight from Charlotte Douglas International Airport in North Carolina. 

On board were 23 checked bags, 19 passengers, and two pilots. As the aircraft became airborne, it began to pitch up rapidly. The plane reached an altitude of 1,150 feet, then stalled abruptly, pitching down into an uncontrolled descent before crashing into a maintenance hanger and 35 seconds later bursting into flames. 

An investigation found the aircraft was 580 lbs overweight. This weight and balance issue, combined with a substandard maintenance repair the day before, resulted in a total loss of control of the aircraft. Two heavier-than-usual suitcases and a miscalculation of passenger weights resulted in the aircraft’s Center of Gravity (CG) falling 5% outside of the allowable parameters.

Let’s take a closer look at weight & balance, why it’s important, and how to calculate it accurately.

Why Calculating Aircraft Weight & Balance Is Important

Weight & balance have a direct impact on:

• Maneuverability
• Performance
• Safety margins
• Stability
• The structural integrity of an aircraft

Performance problems associated with overloading an aircraft include:

• Increased fuel consumption 
• Higher required takeoff, approach, and landing speeds
• Longer takeoff and landing distances
• Higher stalling speed
• Lower maximum altitude

As a result, these parameters are heavily regulated by safety compliance laws. 

A study conducted by the University of Texas concluded that aviation accidents related to weight or CG are often more fatal than those that result from other causes, such as power plant failure, unintended flight into Instrument Meteorological Conditions (IMC), and Controlled Flight into Terrain (CFIT).

An imbalanced aircraft will result in either nose-heavy or tail-heavy conditions, undermining the pilot’s ability to control the plane, particularly during takeoff and landing, while drastically affecting in-flight stability.

For an aircraft to perform as expected, both weight & balance need to fall within the parameters specified by its manufacturer.

Manufacturers’ Role in Weight & Balance

Weight & balance involve various parties, starting with the designers of the aircraft. The designers carefully calculate and determine the ideal CG and the maximum allowable deviation from this specific location. This is based on operational conditions and structural strength per design, such as the amount of lift the wings or rotors can provide. 

CG parameters are constrained by the control authority of the aircraft’s flight controls throughout the entire flight regime from take-off, through climb, cruise, descent and landing. In particular, the elevator and trim authority in all flap, slat and landing gear configurations is taken into account to ensure pilots always have enough control. 

After that, the manufacturer is required to provide the empty weight of the aircraft and the location of its empty weight center of gravity (EWCG) at the time the certified aircraft leaves the factory. Once this has been determined, the FAA-certified mechanic or maintenance organization responsible for maintaining the aircraft must record any changes to the weight & balance due to repairs, alterations, or additions. 

These weight & balance records must be retained and kept current. They’re used by dispatchers and flight planners for every flight plan. The records ensure the aircraft can be loaded correctly so it stays within structural weight limits and the authorized CG envelope from taxi, through take-off and landing.

Lastly, the pilot in command (PIC) must also know the aircraft's weight & CG limits. The PIC is ultimately the person responsible for the correct loading before every flight; it is their job to make sure the aircraft is within limits.  To achieve this the PIC calculates actual aircraft loading, accounting for crew, passenger, cargo and fuel weights.

Accuracy in Weight & Balance Calculations

On a rainy July 17, 2005, a Cessna CitationJet 525 approached Old Bridge Airport in New Jersey, carrying two passengers. The airplane departed with a full load of fuel, flew approximately 35 minutes, and upon touchdown, weighed approximately 9,500 pounds. 

According to data recovered from the Enhanced Ground Proximity Warning System, the approach became unstabilized 0.1 miles from the runway threshold, triggering an aural sink rate warning. 

The Hertrich Aviation Citation touched down fast on the first one-third of the wet runway. The pilot, realizing the plane wouldn't stop in time, attempted an aborted landing, applied full power and retracted the flaps to the takeoff position. The airspeed did not seem to accelerate at a normal rate, and the airplane failed to obtain flying speed. It then rolled off of the runway pavement, colliding with several objects and causing substantial damage to the aircraft. According to performance information, at 9,500 pounds, on a wet runway, 3,550 feet was required, 306 feet greater than available. Fortunately, the pilot received only minor injuries and the passengers were unharmed. 

The National Transportation Safety Board's investigation concluded that the cause of the accident was the pilot's improper preflight planning, failure to consult performance data, and failure to obtain the proper touchdown point, which resulted in a runway overrun. Contributing factors to the accident were the excessive airspeed, overweight condition, and wet runway.

This accident shows the importance of thorough preflight planning and the potentially disastrous consequences of neglecting weight and balance considerations, especially in challenging landing conditions.

How To Automatically Calculate Weight & Balance with ForeFlight

ForeFlight’s Weight & Balance feature allows you to calculate accurate weight & balance quickly, easily, and with perfect accuracy. With hundreds of built-in profiles for popular aircraft pre-loaded, set-up is fast. Once configured, you can input load and fuel details in a matter of seconds. Being fully integrated into the ForeFlight ecosystem, there is also no need to use separate apps that disrupt planning workflows. 

Additionally, since interiors are occasionally modified, profiles are fully customizable, allowing users to continuously customize the weight & balance. Last-minute changes are no problem – ForeFlight Weight & Balance automatically and instantly recalculates whenever a change has been made, ensuring every flight is compliant and safe. 

Adjustments to seat and cargo loads, starting fuel values, and fuel consumption also automatically recalculate, and you can save permanent weight values as part of your aircraft’s Basic Operating Weight, so you only need to add weights that vary between flights the next time you get ready for takeoff. 

Learn more about how ForeFlight Weight & Balance works in the video below:

For safer, easier weight & balance management, choose ForeFlight. 

Frequently Asked Questions

What factors contribute to changes in the aircraft's weight and balance during a flight?

The primary factor contributing to changes in the aircraft’s weight & balance during a flight is fuel consumption. As fuel is burned, the aircraft loses weight, usually resulting in improved performance. Other factors could include cargo or passengers shifting positions during a flight and certain atmospheric conditions.

In emergencies, what considerations should pilots make regarding weight and balance for safe maneuvering and landing?

Pilots should be mindful of the ways in which the aircraft’s weight and balance affect maneuverability and range. If the aircraft is nose-heavy, pilots may experience difficulty controlling and raising the nose during landing. If the aircraft is tail-heavy, this has a serious effect on longitudinal stability, impacting the pilot's ability to recover from spins or stalls. However, if the aircraft’s weight & balance fall within the specified ranges, they should have no effect on handling during an emergency.

How does weight and balance affect takeoff and landing performance?

A heavier aircraft requires more thrust to achieve rotation speed, leading to longer takeoff distances. Heavier aircraft also take longer to stop due to increased braking energy, resulting in longer landing distances.

The center of gravity (CG) location is also important. A more forward CG requires more lift to maintain level flight, increasing induced drag and reducing performance. Conversely, a more aft CG requires less lift, resulting in better performance but decreased stability. Essentially, a forward CG leads to slower speeds and more stability, while an aft CG leads to faster speeds and less stability.

Weight and balance, while critical, is just one input into takeoff and landing performance. Once you have your W&B calculations, you then need to gather the other elements, such as weather information (wind, temperature and pressure settings all affect aircraft performance. For example, high temperatures and high altitudes can decrease aircraft performance, requiring longer takeoff and landing distances) before performing your runway analysis. 

The maximum weight an aircraft can lift from or land onto a runway is limited by either the aircraft's structural limits or its performance limits. 

On a standard day with a long runway, performance limitations are less likely to be a factor. However, when operating from a shorter runway, in high temperatures, with a tailwind, or under other challenging conditions, performance limitations can become critical.