Aeropropulsion lab uses VXI to test helicopter engines

Several months ago, a boat manufacturer needed to verify the performance of the surplus gas turbine helicopter engines he was going to buy from the US government to power speedboat racers. The problem was finding a test lab with the right capabilities. Testing helicopter engines for use in speedboats, is, after all, not a common requirement. The lab he finally chose was the Aeropropulsion Lab in Ottawa, ON, Canada.

Figure 1 Brian Barry, technical officer and data-aquisition specialist, makes an adjustment during an engine test in the NRC Aeropropulsion Lab, Ottawa, ON, Canada.

The laboratory provides consulting services, engages in collaborative research, and licenses its technology to clients who need to perform design, strength, durability, structural-integrity, and performance tests of aircraft, gas-turbine engines, and space structures. The engine test cells of the Aeropropulsion Lab are flexible enough to test a tank engine one day, an after-burning turbojet the next, and a helicopter engine after that.

The engines destined for speedboats were Lycoming T53-L-13 1400 shp (shaft horsepower) engines used in Huey helicopters designed for military and medical service during the Vietnam war. This type of engine can produce 1400 shp at 64 psi of torque on a standard day (59° F) at sea level (29.92 HG). When installed in a UH-1D "Huey" helicopter, the engine provides enough power to carry up to 12 troops with a crew of two up to of 293 miles at 127 mph.

In the NRC Aeropropulsion Lab engine test cells, the T53's were mounted on a dynamometer and connected to VXI instrumentation. Technicians started the engines and monitored several parameters, including horsepower and torque, to verify engine performance.

Brian Barry, technical officer and data-acquisition specialist at the Aeropropulsion Lab, explains that two of the facility's test cells are equipped with VXI systems. The lab first purchased PC-based SCXI (Signal Conditioning Extension for Instrumentation) equipment, but the SCXI instrumentation did not provide the performance they needed.

"If you look at the specs of VXI equipment," says Barry, "you'll see that the temperature accuracy is better, channel rates are higher and reliability is presumably better. We've only had our VXI equipment since 1998, so I don't consider that long enough on which to judge reliability. Also, it's a multivendor standard, so we're not limited to specific vendors."

The Aeropropulsion Lab has two test systems for measuring engine parameters (see "Components in the test system," p. S8). The lab purchased its VXI and signal-conditioning modules from KineticSystems (Lockport, IL). One reason Barry chose the KineticSystems signal-conditioning modules is their "tweak-ability." "You can set prefiltering gain in groups of eight and post-filtering gain individually," says Barry.

Typically, test specs call for less than 100 channels of data acquisition, and often only 30 to 40 analog channels. Barry notes, however, that the lab will soon need up to 300 channels acquiring data at rates up to 100 kHz.

Barry explained that one of the engine test cells was large enough to accommodate two engines, so they divided the cell into two. By installing a separate counter module and two additional multiplexers, the lab was able to make measurements from two test beds using only one mainframe. Although they cannot conduct tests in both test cells simultaneously, the engineers have significantly shortened configuration time between tests.

As a result of the testing performed by the Aeropropulsion Laboratory, the customer decided to purchase the T53 gas turbine engine. The customer is now using the engine in off-shore racing.

You can e-mail Steven C. Krebs c/o tmw@reedbusiness.com.