NASA researchers are planning to put the engines of a C-17 cargo transport plane on a diet of cereal and crayons as part of a series of tests of new health diagnostic sensors that they hope will become an early warning system for potential engine failure.
The space agency says its Aviation Safety Program is working on new engine diagnostic technology that will identify early symptoms of glitches in jet engines, including changes in vibration, speed, temperature, and emissions. The goal of the new sensors is to help ground crew and jet mechanics identify potential problems sooner and repair them before they threaten the safety of pilots, crew, and passengers.
Technicians prepare a US Air Force C-17 for engine health monitoring tests as part of the Vehicle Integrated Propulsion Research program -- a collaboration by NASA, the Air Force, and Pratt & Whitney to create a sensor system for early diagnosis of engine problems. (Source: NASA)
The new sensor system is being designed and developed as part of the Vehicle Integrated Propulsion Research (VIPR) program, a joint project of NASA, the Air Force, and Pratt & Whitney, the company that developed the C-17 engines. A number of engine health sensors are being tested as part of the project, including a model-based performance estimation and diagnostics system; an emissions sensor system to monitor the output of carbon, oxygen, and other gases; a self-diagnostic accelerometer; and high-frequency vibration sensors. Other sensors are tracking the effects of foreign materials on legacy instrumentation, including an inlet debris monitoring system and high-fidelity fuel flow measurement.
Engineers are putting the sensors through a series of ground tests at NASA's Dryden Air Flight Research Center using the engines of a retired C-17 on loan from the Air Force. The first test, conducted in December, activated the sensors on one of the C-17's two turbofan engines and ran water through it to see how the sensors would react. In a second test scheduled for early next year, the plane's engines will suck up crayons and cereal to monitor the ability to detect small bits of debris. The cereal and crayons will leave a colorful trail of grains and wax that the researchers can see and study to gauge how well the sensors work.
Following that, a final test on the system will introduce hard, glass-like particles that will simulate volcanic ash, which is too small for the eye to see. NASA says researchers will evaluate how early the sensors and related software can detect the particles and report a problem.
In fact, volcanic ash is one of the reasons for interest in developing a diagnostic sensor system. In 2009, an ash cloud from the Eyjafjallajökull volcano eruption in Iceland caused major air travel disruptions. Airlines would not fly through the cloud, because of the potential damage to jet engines, and they were forced to cancel an unprecedented number of flights. NASA says researchers are trying to determine the effects of ash early on to avoid such issues in the future.
The Air Force has conducted tests in the past on the effects of ash on jet engines, but this is the first time sensors are being used as part of that testing.
Given the recent incidents not only with volanic ash, but planes getting into trouble hitting flocks of birds, this kind of testing is critical. Interesting choice of materials to test with. Any backstory on why cereal and crayons to simulate debris that a plane might encounter mid air?
Well, I'm impressed. I remember when all of those flights to and from Europe were cancelled. It's nice to see that someone is looking into improving our ability to detect the volcanic glass -- and thus probably avoid it. I know the flight folks were criticized from over-caution. With the sensors, the airlines will be able to determine whether there is actual danger or not.
Rob, I also remember when a lot of those flights were cancelled because of the volcano. I believe one of the big trade shows in Europe lost thousands of attendees because of it. I would imagine that some of the big carriers also lost money as a result of it.
Yes, Chuck, the big carriers lost tons. They were furious with the government, beliving they were being overly cautious. The advantage of these sensors is that the decision to fly or not could be made based on evidence rather than speculation.
I have to admit, Rob, I too thought they were being too cautious at the time. But after reading TJ's comment below, I'm not so sure. Apparently, one aircraft had four engines flame out after encountering an ash cloud in 1982, it says.
Yes, Chuck, I remember at the time reading about the serious danger. So caution made sense, especially since they didn't know exactly where the ash was or how dense it was. Presumably, sensors in the turbines would allow the aircraft to divert from an ash cloud before the engines were destroyed.
Thanks for writing about this. It's good to see that warning systems for engines are being put into place. Like Beth, I also wonder why these particular materials were used--cereal and crayons. And when it comes to flying, I can't imagine what "over-caution" would mean.
This article was very interesting. The choice of materials used as stated in the article: "The cereal and crayons will leave a colorful trail of grains and wax that the researchers can see and study to gauge how well the sensors work." It kind of a "blood splatter pattern" for detecting the efficiency of the sensors. Quite clever if you ask me!
I did notice--as no doubt others did--the statement in the article about what cereal and crayons will accomplish. What I'd like to know is why cereal and crayons for this purpose, instead of something else? For example, was the choice based on size of particles, consistency, or other factors?
BA flight 9 on June 24, 1982 demonstrated the very real danger; all four engines flamed out after encountering an ash cloud.
This seems like testing for minimum safe exposure to a heavy metal poison. I'd just as soon avoid it completely.
I like the idea of ever better engine damage detection. But there should be some attention paid to detecting hazards such as ash clouds from a distance, to better quantify the reach of the cloud. Instead of shutting down air travel over the entire continent, a much more narrow exlusion zone can be defined to minimize travel disruption while still completely avoiding the cloud.
I wonder if some of the latest radar technologies (millimeter wave, synthetic aperture) could be tweaked in effort to discern the density and spread of ash clouds.
TJ, what is interesting along those lines is that there have not been such sensors employed until now. Sensors will give us a better picture of what the restrictions should be. That and the detection of the clouds and their composition should allow a more fine grained safety zone definition.
When you are going 500-600MPH, by the time the sensor has anything useful to tell you, the Engine has already suffered damage. These sensors would be more useful to help schedule maintainance of the Engines (e.g. knowing when the Engine has suffered enough cumulative wear and tear to need an overhaul).
Radar or Lidar mapping of the area in front of the plane seems much more useful for volcanic damage avoidance. It would let the pilot know that they need to climb or descend to avoid the cloud of debris. Even better, would be satellite mapping of areas or routes to avoid (just like weather, but tuned to detect airborne volcanic debris).
Water or snow entering the engine can be quite impressive. One night (way way back) I was in an airport tower and saw one of the big planes land on a runway that had a light dusting of snow. The explosion out the back of the engine was distressing (at least to me). Not seeing anyone even notice, I asked what had just happened, and they told me that it was a compressor stall from snow sucked up into the engine. Apparently it happens all the time.
There is a Suit of sensors in your everyday jet engine now. These sensors can help you monitor, control, and plan maintenance. Some are even indicator only. I don't know what this extra suit of sensors will do for us? Maybe increases cost and adds weight? Other than research purposes I don't think this research has much to offer. Just an opinion, I would like to see the report to this when all is done.
Elizabeth, thanks for this article. The first A in NASA stands for Aeronautics, yet NASA's aeronautics programs get much less attention than the space program.
Great article.I am always amazed at the resourcefulness engineers bring to the table when developing tests and executing programs.Several years ago, the Air Force had a program to evaluate bird strikes when ingested into inlets of jet engines. This came after several near-fatal accidents at Shaw Air Force Base in South Carolina.I was in basic training shortly before one such incident occurred.The pilot ejected successfully but the F-4 was lost. He was making touch and go landings when a swamp buzzard got into the act.It happens in a heartbeat but can be devastating.To get some idea as to severity, dead chickens were tossed into stationary aircraft, with engines running, to see what damage might result.The test was aborted due to PETA.(The chickens were dead, by the way.) This program is much more structured; consequently, you would expect the results to be much more beneficial to investigators in the process of proving sensors. I do know also that volcanic ash although infrequent, represents a real problem to aircraft engines.Again, great article.
I agree - thanks for the article This sort of testing is the unglamorous "grunt work" that leads to advances in safety and improved performance over time. Kudos for highlighting a critical part of the design process - understanding how products perform in the real world.
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