Matt Kamlet, CBS Los Angeles
EDWARDS (CBSLA.com) — One of the more tragic aspects of a flight crash is the circumstantial fact that, sometimes, the pilot simply does not have control over the anomaly that causes the aircraft to fail.
Ice buildup on the wings, external weather variables and other environmental elements can be decreased, even avoided, by experienced pilots who know the maneuvers or adjustments necessary to reduce their effects. Too little can often be done, however, to predict or address the issue most commonly associated with in-flight disasters — engine failure.
The lack of control over a situation caused by engine failure or shutdown is a dire reality indeed, and it is responsible for the majority of aviation apprehension.
Researchers at NASA's Armstrong Flight Research Center, located in the deserts of Antelope Valley, north of Los Angeles, are working to eliminate, or at least alleviate, part of the engine failure factor from the aviation equation.
The VIPR (Vehicle Integrated Propulsion Research) project, the product of a partnership between NASA, the U.S. Air Force and a number of other agencies and companies, is a series of tests to evaluate health management technologies on commercial engines.
"Our objective is researching engine health technologies," principal investigator John Lekki of NASA's Glenn Research Center said. "We're looking at technologies that will be able to identify aircraft engine faults at the beginning stages. We want to be able to identify those and diagnose them, and then also give an idea of how they're going to change over time."
These tests began in 2011, and have focused on how engine compromise is associated with the pollution or corruption of that engine's sensors. Through implementing environmental fault scenarios in these tests, AFRC researchers are learning more about engine health through new sensors, and are able to asses advances in engine diagnostics.
Two F-117 turbofan engines, provided by the Air Force, were mounted on a C-17 aircraft, on which the tests are performed as the aircraft is grounded. These tests include studying the engine through normal engine operations, seeded mechanical faults, seeded gas path faults, and finally, accelerated engine life degradation through the ingestion of volcanic ash.
The subjection to volcanic ash represents the next stage of NASA's VIPR testing at AFRC.
"Volcanic ash for us, initially, was a medium that we could use to fully degrade the aircraft's engine, and we're interested in degrading the engine to see how well our health management technologies pick up these faults, and how well we can determine what the trend of the engine is going to be. We chose volcanic ash because it's an interesting way to fault an engine, but it's also something that hasn't been carefully studied, and it's something that is definitely a need that we have."
USGS estimates that there are about 1,500 active volcanoes on the planet. Any time there are eruptions, it can create problems for aviation.
When Eyjafjallajökull erupted in Iceland in 2010, the result was a shutdown of much European airspace for two weeks, which had a $2 billion impact on the industry. What damaged the aviation industry further was the subsequent scramble to figure out what airspace was safe to fly in, and what had to be avoided.
This confusion stemmed from the fact that there hadn't been any studies on the effect of this volcanic ash on engine health — until now.
The test works by using a "spider" spray rig, developed by General Electric, to deposit "low to moderate" concentrations of volcanic ash, collected by project partner Rolls Royce, into the C-17's running engine.
Among the sensors under study is a vibration sensor, as well as a thin film sensor — a dynamic temperature sensor which picks up quick temperatures fluctuations in the engine. In the turbine section of the engine, which is a challenging space for instrumentation due to high temperatures, and which is where the "heavy lifting" of the aircraft is done, a microwave tip clearance sensor, developed through the NASA Small Business Innovation Research program, was installed.
"This sensor can measure the gap between the outer wall of the turbine and the tips of the turbine blades," Lekki described. "This is a key measurement in aircraft engines, because if we can measure this, and measure precisely, not only can we tell whether or not there are problems with the turbine blades, which has been one of the really difficult areas to get health management information out of, but we can also look at adding what we call active clearance control to the engine. Active clearance control will give us the benefit of having a more fuel-efficient engine."
Ash accumulation on the engine's compression blades contributes to erosion, ultimately compromising the health of the engine, and therefore, the safety of the flight.
Behind the engine, emissions sensors are installed to read the combustion of the engine, giving more insight to the health of the engine.
Through the volcanic ash test, researchers aim to study the effect of several hours of exposure to the ash.
The tests have three primary objectives:
- The incorporation of smarter sensors designed to improve flight safety and reduce aviation costs.
- The detection of potential engine faults.
- The evaluation of advances in engine diagnostics.
"The primary benefits of health monitoring, in the long term, are mostly economic benefits," Paul Krasa of NASA's Lanlgley Research Center said. "They let you really take a look into the health of the engine that you can work on things when there are issues. That's the primary direction that the (aviation) industry is looking at health monitoring."
NASA considers itself as being in a position of responsibility, to lead the way to frontiers unknown, as well as to make safer those endeavors which we have discovered, and continue to master. The goal of making aviation safer for all of us is one NASA takes seriously, and one which the researchers at AFRC are making a reality.
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