Area Flow Gage Enables In-Process Verification for Aerospace

The L.S. Starrett Co., a global manufacturer of precision measuring tools and more, has introduced a chordal height gage, also known as a DO gage. The gage is custom designed and manufactured for measuring the opening heights of turbine vanes at specific locations to verify that an aircraft engine will get proper air flow. The Chordal Height Gage is part of the Starrett line of special-area flow gages.

The company notes that sometimes measuring challenges are best solved with a specially made gage, so the Starrett Special Gage Division designs and builds dimensional measuring instruments to meet customer specifications.

The size of the Chordal Height Gage is based on the specific application for which it will be used, with the gage no larger than a tissue box. Despite the small footprint, it has three independent probes used to take measurements, including a free-floating central gage body which allows the middle probe to take accurate readings along the trailing edge, regardless of the variable contours which are often on these nozzles.

The gage is built in a “Lazy-L” shape to enable linear readings to be taken perpendicular to the trailing edge of the blades, giving a dimension for the smallest opening that air can flow through. These features help contribute to the accuracy and repeatability of the Chordal Height Gage, which is within 0.0005", although the indicator readouts are generally set to a 0.001" resolution per customer requirements.

Special Gage Division engineer Kyle Webber notes that typically, operators must remove a nozzle from the production line and bring it to an automated inspection machine, such as a CMM, to take turbine area flow measurements. The company’s Chordal Height Gage is designed for rapid in-process verification of these parts, eliminating time lost on additional teardown and setup of machinery.