N112-114 TITLE: Innovative Method for Aircraft Gross Weight and Center of Gravity Estimation

TECHNOLOGY AREAS: Air Platform

ACQUISITION PROGRAM: PMA-299, Multi-Mission Helo (H-60)

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OBJECTIVE: Develop an innovative model for the estimation of the gross weight (GW) and center of gravity (CG) of aircraft under general conditions.

DESCRIPTION: An accurate software-based assessment of the GW and CG for both fixed- and rotary-wing aircraft is critical to establish aircraft fatigue and to estimate life expectancy because these properties greatly affect static and dynamic characteristics. Currently, information pertaining to these values must be recorded manually both on the ground and in flight, a time-consuming and painstaking process. For example, if cargo or stores are released/relocated/picked up during a flight, a log of what and when is required to make the appropriate calculations. The tasking involved imposes a significant burden on the squadron and technicians, as well as a high probability of introducing human error. Furthermore, under the current approach, if there is no instrumentation to indicate the fuel level, several assumptions must be made regarding the fuel burning rate. This situation often results in estimates that are overly conservative to ensure that the aircraft is not overloaded or overstressed.

Over the years, several different methods have been proposed to automatically estimate GW and CG. However, these technologies have various limitations. For example, some of them calculate only the GW or only the CG. In methods that do estimate both the GW and CG, the resultant data represent an idealization of the actual rotorcraft dynamics, so further work may be required to investigate the details of implementation challenges. In addition, the accuracy of the output depends on having accurate information that is readily available, and these approaches do not have the capability of making the necessary adjustments for degradations in performance.

As such, there is a need for a novel, innovative, and sophisticated computational method that overcomes the limitations of current state-of-the-art techniques. An innovative physics-based approach would improve the accuracy of CG and GW estimations for the entire mission duration for calculating airframe fatigue life expended. Such an approach would synthesize flight loads by determining the GW and CG in near real time using in-flight state parameter data from existing sensors provided by the on-board mission computer and Health Usage Monitoring System (HUMS). This approach will remove excessive conservatism in the weight estimate of the payloads and fuel burn rate and provide a much better accurate, near real-time CG and GW information for entire mission including in-flight cargo re-positioning and airdrops/pickups. Having a software-based tool that is able to compute GW and CG information simultaneously, quickly and accurately will enhance situational awareness, reduce the time and effort spent in logging the GW and CG information, improve the fidelity of the data, and increase efficiency. For rotorcraft applications, such a method should provide an estimate of GW and CG and have the ability to track them over the entire flight regime, including in-flight drop-offs and pickups, and must not rely on the data collected during a specific flight regime (for example, hover) to make an accurate determination. The method should also address rotorcraft variability and account for engine/torque/performance degradation over time. The recorded data could then be extracted to ensure GW and CG are known at all times during the flight.

PHASE I: Research and develop a novel software-based concept to estimate aircraft GW and CG and demonstrate the feasibility of this approach in a simulated environment.

PHASE II: Develop prototype demonstrators based on a set of realistic, operationally based scenarios and mission profiles of a Navy aircraft platform. Quantify the degree of uncertainty in the estimates.

PHASE III: Integrate prototype demonstrators with existing operations/applications/onboard tools to obtain real-time measurements of GW and CG.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The methods developed to establish GW and CG can be applied to any military or commercial aircraft. Application is broad, as commercial aircraft can take advantage of this information to better transfer luggage to meet flight envelopes.

REFERENCES:
1. Abraham, M., & Costello, M. (2009). In-flight estimation of helicopter gross weight and mass center location. Journal of Aircraft, 46 (3), 1042-1049.

2. Idan, M., Iosilevskii, G., & Nazarov, S. (2004). In-flight weight and balance identification using neural networks. Journal of Aircraft, 41 (1), 137-143.

3. Morales, M., & Hass, D. (2001). "Feasibility of aircraft gross weight estimation using artificial neural networks," Proceedings of the 57th American Helicopter Society International Annual Forum. (Alexandria, Virginia, AHS International), 1872-1880.

KEYWORDS: Aircraft; Rotorcraft; Weight; Center of Gravity; Gross Weight; Automated Estimation

** TOPIC AUTHOR (TPOC) **

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