Mensing died July 26 at his home in Santa Paula after a brief illness, said his family.
A World War II veteran, Mensing opened a precision sheet-metal business called Sheetcraft in Northridge in the early 1960s and became known for his skill in making new parts for damaged helicopters and airplanes.
In 1970, he was offered a different kind of job by the Los Angeles County Fire Department, which in 1957 had pioneered the use of water-drop tanks on the bellies of helicopters for firefighting.
Aircraft Rebuilders, the company that had been making the tanks for the fire department, was no longer in business and the department wanted Mensing to replicate the company's most recent tank.
Working with Doug Mathews, the fire department's chief of helicopter maintenance, Mensing made a number of innovative changes to the 360-gallon tanks he began manufacturing for the department.
"When Mensing got it, we kept improving it," the now-retired Mathews recalled on Thursday. "He came up with a lot of ideas, plus we came up with some ideas."
Mensing not only made the tank lighter by making internal changes, but he changed it from a single-drop tank to a split-drop tank: Instead of the pilot having to drop the entire load of water, he could dump half a load at a time.
"It's commonly known as the Sheetcraft tank or the L.A. tank," said Mathews, adding that the U.S. Forest Service, the state of California, the Los Angeles City Fire Department and the Ventura County Fire Department are among those that later began using Mensing's tanks.
"He was a pioneer in helicopter water-drop tank manufacturing and did an extremely good job improving it," Mathews said.
Over the next 30 years, the product came to dominate Mensing's Sheetcraft business, with his tanks being used in such far-flung locales as Sardinia, Italy; China and South Korea.
Mensing, who moved his operation from Whiteman Airport in Pacoima to Santa Paula Airport in 1975, retired a few years ago.
He was born April 25, 1924, in Calexico and later moved with his family to North Hollywood.
After graduating from high school in 1942, he joined the Navy and spent most of his service time as an aviation mechanic. After his discharge in 1948, Mensing attended the California Aeronautic Mechanic School in Glendale.
He is survived by his wife, Alice; his children, Lisa Morgan, Kelly Mensing, Mindy Foley, Robert Mensing and Barbra Moore; his sister, Prudence Safady; 19 grandchildren; and a great-granddaughter.
Services will be held at 11 a.m. Friday at the Church of Jesus Christ of Latter-day Saints, 604 Ojai Road, Santa Paula.