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Putting an End to the Guessing Game

By Tim Schnettler

Estimating the weight of helicopters during flight for military and medevac operations

Helicopters offer versatility and ease of access that other modes of transportation cannot. From military operations to use in lifesaving medical situations to transporting VIPs, more than 45,000 helicopters are in operation worldwide, making them as common a sight in the skies as airplanes.

By measuring the aircraft responses to the pilot's control inputs, the onboard software package will estimate weight and mass center by using advanced computational methods.

But for helicopters—unlike airplanes—the weight and center of mass can change drastically during flight. In a battle situation, cargo or troops may enter or leave the aircraft rapidly. The pilot may not know precisely how the helicopter's weight has changed, and he or she has little time to figure it out. 

"Currently there is a person whose job it is to estimate the weight of items coming on and off the aircraft," says Texas A&M University aerospace engineering professor Jonathan Rogers. "They are very conservative because they have to be. A pilot's precise knowledge of how much the helicopter weighs would benefit him greatly.

Putting an End to the Guessing Game

Rogers and his students are working to create an avionics package that will provide precise weight and mass center information to the pilot in real time.

"Right now, with these estimates, the pilot doesn't really know [the exact weight and mass center]. So when it comes to questions like, 'Can I operate in certain conditions?' and 'Can I hover at a certain altitude?' it is probably somewhat of a guessing game."

To remedy this, Rogers and his students in the Helicopter and Unmanned Systems Laboratory (HUSL) are working to create an avionics package that will provide precise weight and mass center information to the pilot in real time. By measuring the aircraft responses to the pilot's control inputs, the onboard software package will estimate weight and mass center by using advanced computational methods. 

"This will provide the information he or she needs to make better decisions. What we are going to do is take these helicopters and drop weights off them when they are flying and see if we can filter the sensor data and the control inputs," Rogers says. "Using Kalman filters [an algorithm using a series of measurements observed over time] and potentially more advanced methods, we will attempt to, in real time, estimate the weight change that has taken place."

Once that is determined, the avionics package would give the pilot an estimate of how much the helicopter weighs and where the mass center is located.

Early attempts at solving the engineering problem

Although Rogers' current project is new to Texas A&M, he says it has been tried in various simulations and it has proven effective. 

When Rogers was conducting his postdoctoral research two years ago at the Georgia Institute of Technology, his adviser at the time proposed this system to a consortium of helicopter companies and to NASA, which partakes in a lot of rotorcraft research. But they were less than enthusiastic. 

"They said you can never make it work in practice," Rogers says. "He found out later that at least two of the helicopter companies were pursuing those initiatives internally."

Putting an End to the Guessing Game

Aerospace engineering graduate student Nate Miller is designing autonomous helicopter flight control laws to enable a wide variety of UAV research projects at the Helicopter and Unmanned Systems Lab.

Being spurned didn't cause them to shut down shop. Instead, it only motivated them even more, and Rogers has brought that passion to succeed with him to Texas A&M and has instilled it in his students.

"Our attitude was, 'Let's do this and let's make it work and show everybody that it can work in practice,'" Rogers says. "That is the beauty of having these helicopter vehicles that we have in the HUSL. We can take these ideas that everybody agrees work in simulation and show that they do work in practice.

Because of the conditions helicopters fly in as well as the loads placed on them, certain parts require replacement and repair more often than others.

Other benefits

The operating costs for helicopters are much higher than those of fixed-wing aircraft, such as airplanes. Because of the conditions helicopters fly in as well as the loads placed on them, certain parts require replacement and repair more often than others. 

Rogers contends that his research will help in the area of maintenance as well. Having exact weights, rather than just estimates, means that certain parts of the vehicle would not need to be replaced as often. 

"There are certain life-limited parts in a helicopter that, based on how long it has been operated and at what weight it has flown, have to be replaced," Rogers says. "If we can extend the lifetime of these parts, we can reduce operating costs. That would be one of the huge benefits." 

Dr. Jonathan Rogers
Dr. Jonathan Rogers
Assistant Professor
Aerospace Engineering
979.862.3413