Thomas M. Mountjoy, 61, a market engineering consultant with NKA Inc. engineering representatives of Silver Spring, died of cancer Sunday at Providence Hospital.

Mr. Mountjoy moved to the Washington area in 1941. He worked as an engineer and consultant for a number of local electronics and engineering firms, including Litton Industries, Pratt and Whitney Aircraft Corp. and Engineering Research Corp. now a division of The Singer Co., before joining NKA about three years ago.

He was born in Louisville and studied aeronautical engineering and business administration at Purdue University and the University of Kentucky.

Mr. Mountjoy held a private pilot's license and much of his spare time was spent at his lifelong hobby of building and designing authentic-to-scale, radio-controlled model airplanes. He wrote many technical articles for the R/C Modeler and Scale R/C Modeler, publications of the radio-Modeler, publications of the radio-controlled model airplane industry, and was a member of the Prince George's Radio Control Club and the Washington Hangar division of the Quiet Birdman Club.

He lived in University Park, Md., for 22 years.

Survivors include his wife, Beatrice Mensch Mountjoy, of the home; a son, Thomas M. Jr., of Greenbelt; a daughter, Pamela M. Bacon, also of the home; a brother, Morris M., of Hanover, Pa., and one grandchild.