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Meet: Robert Jercinovich

Instrumentation Engineer, 12' Wind Tunnel
Ames Research Center, Moffett Field, CA

My journals
Who am I
The performance of aircraft is defined by drag, lift, efficiency, etc. In order to quantify these characteristics and improve efficiency we do wind tunnel testing. These parameters cannot be measured directly but can be calculated from other characteristics that can be measured. During wind tunnel testing the Instrumentation Engineer is responsible for converting physical phenomena that can be measured into electrical signals so that they may be manipulated by a computer.

Some of the phenomena that can be measured are pressure, force and temperature. Pressure distributions across a wing will quantify the lift characteristics, force measurements will quantify the drag characteristics, etc. Pressure, for example, may be measured a number of different ways, to wit: diaphragm transducer, silicon piezoresistive element, or pressure sensitive paint. It is the Instrument Engineer's job to determine which type of transducer is best suited for the job in order to obtain the best quality data. The factors that need to be considered to determine the best type of transducer are: response time, accuracy, resolution, physical size, signal type, etc. The Instrumentation Engineer must also interface the transducers to the data system by specifying the gains, filters, channel assignments, etc., on the computer. Thus the instrumentation Engineer must be cognizant of both hardware and software.

For each test we have a pretest meeting with the customer and the researchers. They describe what they are looking for, their model, and what they are bringing to the test. We plan the instrumentation requirements based on their needs. Pressure taps for instruments are built into the model. We connect pressure sensors to these taps with tubing. The Instrumentation engineer must specify the type of tubing to use and must consider things like the pressure and temperature the tubing will be used at. Also, he must consider flexibility and termination of the tubing. Thus, a Instrumentation Engineer must be a Jack-of-all-trades.

We call a data run a sweep. For a sweep we record the measurements at a series of angles of attack or different pitches of the model (Alpha sweep) or angles of side slip, left to right (a Beta sweep) for a given Mach speed or Reynolds number in the wind tunnel. The measurements we make include the pressure distribution across the wings, the forces through a balance on the model, and temperature to correct for any thermal characteristics. We always measure force. But for some tests we look for some unique data.

My Career Path
In college, at University of California at San Diego, I studied electrical engineering. My emphasis was in Systems and Control. After college I worked at the Naval Ocean Systems Center where I was in communications. After that I worked at McDonnell Douglas where I worked on instrumentation for structures and simulators. To test aircraft structures we did durability and metal strength tests measuring the forces on the skin or substructures. The simulator testing was for aircraft hydraulic systems and computer systems.

What I Like About My Job
I get to play with a lot of equipment. I like that my work is objective.

The Early Influences
When I was a kid I liked to take apart cars and rebuild them. My parents encouraged me to study science or engineering.

Advice
Take as many science and math classes as you can.

Future Plans
I look forward to continue working with the newly remodeled 12' wind tunnel. It is unique in that it runs at pressure levels at up to six atmospheres. By pressurizing the wind tunnel you can scale up the model. The 12' wind tunnel can go from vacuum to 90 pounds per square inch. In sea water every 33' you go down is one atmosphere.

 
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