Frederick Charles Achenbach, 89, of Mt. Airy, a civil engineer and an amateur historian, died Oct. 8 of pancreatic cancer at Abington Hospice at Warminster.

Mr. Achenbach retired in 1993 as superintendent of the McNeil Family Estate in Plymouth Meeting. Earlier he had been an engineer with the Pennsylvania Railroad and the Sun Oil Company.

In retirement, he was able to pursue his interest in Germantown history by working as a guide at Cliveden, the historic Benjamin Chew house in Mt. Airy. Over time, he became an expert on the Battle of Germantown, and, by combining his interest and engineering skills, created three maps outlining the famous Revolutionary War battle. The maps are on permanent display at Cliveden.

Mr. Achenbach also had studied the original planning and surveying of the Mason-Dixon Line.

Born and raised in Mt. Airy, he was a graduate of Germantown High School and received a bachelor’s degree in civil engineering from Villanova University.

During World War II, he served as an aircraft engine mechanic for the Army’s 457th Bomb Squadron at Glatton Air Force Base in England.

An avid musician, he played piano with a preference for New Orleans jazz and sung in barbershop quartets.

Mr. Achenbach is survived by a son, Stephen Charles Achenbach, and two granddaughters. His wife, the former Pauline Dee Boyd, preceded him in death.

A memorial service will be held at 11 a.m. Friday, Nov. 7, at Ivy Hill Cemetery, 1201 Easton Rd., in the Cedarbrook section of Philadelphia, followed by a luncheon for those attending. Memorial donations may be made to the Education Fund, Cliveden, 6401 Germantown Ave., Philadelphia, PA 19144. – WF