Harrison began a long association with engineering and air safety when he was posted to Britain for secondment to the Aeronautical Inspection Directorate following the end of World War I. He transferred as a flight lieutenant (honorary squadron leader) to the newly formed Australian Air Force in March 1921, becoming one of its twenty-one founding officers; the prefix "Royal" was added to the service's name in August that year.
Dissatisfied with his RAAF rank considering his leading position in the pre-war Central Flying School, Harrison appealed for greater seniority.
As a result, he was appointed Air Liaison Officer to the Air Ministry in London, with promotion to the substantive rank of squadron leader.
Returning to Australia in 1925, he was appointed Assistant Director of Technical Services in 1927, and soon after helped form the RAAF's Air Accident Investigation Committee.
The following year he became Director of Aeronautical Inspection, receiving promotion to wing commander on 1 July 1928.
Harrison's position took him throughout the country, inspecting equipment and investigating the causes of air crashes.
Promoted group captain on 1 January 1935, he took charge of the Federal government's resources committee for aircraft, aero engines, and motor transport, one of several subcommittees on the Defence Resources Board set up to investigate and report on the readiness of Australian industry to provide munitions for defence in the event of international conflict.

In 1937, Harrison returned to Britain for further study of accident investigation methods, as well as aircraft production.
His position as Director of Aeronautical Inspection was civilianised on 12 March 1938, an event that saw him retired from the RAAF but continuing in the same role.
 He was a member of the court of inquiry into the crash on 25 October of the Douglas DC-2 airliner Kyeema, which overshot Essendon airport in low cloud, killing all fourteen passengers and four crew members.
The inquiry's report singled out Major Melville Langslow, Finance Member on both the Civil Aviation Board and the RAAF Air Board, for criticism over cost-cutting measures that had held up trials of safety beacons designed for such eventualities.
According to Air Force historian Chris Coulthard-Clark, when Langslow was appointed Secretary at the Department of Air in November the following year, he went out of his way to "make life difficult" for Harrison, causing "bitterness and friction within the department", and necessitating the Chief of the Air Staff, Air Vice Marshal Stanley Goble, to take steps to shield the safety inspector from the new Secretary's ire.

Harrison held the position of Director of Aeronautical Inspection throughout World War II, his staff numbering more than 1,200 by 1945.
A reorganisation of the directorate in 1940 had permitted qualified civilian engineers to be recruited for work that required increasing technical expertise, without them having to join the Air Force.
In July the same year, Harrison proposed the construction of a series of test houses to help decentralise chemical, mechanical and metrological testing of materials used in the manufacture of munitions that previously had to go through either the Munitions Supply Laboratories or the National Standards Laboratory.
The result was a major improvement in the speed of testing and, according to the official history of Australia in the war, "a fuller use of the country's scientific and technical manpower".
Harrison's daughter Greta joined the Women's Auxiliary Australian Air Force, and by the end of the war was ranked flight officer.
Harrison began a long association with engineering and air safety when he was posted to Britain for secondment to the Aeronautical Inspection Directorate following the end of World War I. He transferred as a flight lieutenant (honorary squadron leader) to the newly formed Australian Air Force in March 1921, becoming one of its twenty-one founding officers; the prefix "Royal" was added to the service's name in August that year. Dissatisfied with his RAAF rank considering his leading position in the pre-war Central Flying School, Harrison appealed for greater seniority. As a result, he was appointed Air Liaison Officer to the Air Ministry in London, with promotion to the substantive rank of squadron leader. Returning to Australia in 1925, he was appointed Assistant Director of Technical Services in 1927, and soon after helped form the RAAF's Air Accident Investigation Committee. The following year he became Director of Aeronautical Inspection, receiving promotion to wing commander on 1 July 1928. Harrison's position took him throughout the country, inspecting equipment and investigating the causes of air crashes. Promoted group captain on 1 January 1935, he took charge of the Federal government's resources committee for aircraft, aero engines, and motor transport, one of several subcommittees on the Defence Resources Board set up to investigate and report on the readiness of Australian industry to provide munitions for defence in the event of international conflict.
In 1937, Harrison returned to Britain for further study of accident investigation methods, as well as aircraft production. His position as Director of Aeronautical Inspection was civilianised on 12 March 1938, an event that saw him retired from the RAAF but continuing in the same role.  He was a member of the court of inquiry into the crash on 25 October of the Douglas DC-2 airliner Kyeema, which overshot Essendon airport in low cloud, killing all fourteen passengers and four crew members. The inquiry's report singled out Major Melville Langslow, Finance Member on both the Civil Aviation Board and the RAAF Air Board, for criticism over cost-cutting measures that had held up trials of safety beacons designed for such eventualities. According to Air Force historian Chris Coulthard-Clark, when Langslow was appointed Secretary at the Department of Air in November the following year, he went out of his way to "make life difficult" for Harrison, causing "bitterness and friction within the department", and necessitating the Chief of the Air Staff, Air Vice Marshal Stanley Goble, to take steps to shield the safety inspector from the new Secretary's ire.
Harrison held the position of Director of Aeronautical Inspection throughout World War II, his staff numbering more than 1,200 by 1945. A reorganisation of the directorate in 1940 had permitted qualified civilian engineers to be recruited for work that required increasing technical expertise, without them having to join the Air Force. In July the same year, Harrison proposed the construction of a series of test houses to help decentralise chemical, mechanical and metrological testing of materials used in the manufacture of munitions that previously had to go through either the Munitions Supply Laboratories or the National Standards Laboratory. The result was a major improvement in the speed of testing and, according to the official history of Australia in the war, "a fuller use of the country's scientific and technical manpower". Harrison's daughter Greta joined the Women's Auxiliary Australian Air Force, and by the end of the war was ranked flight officer.
Eric Harrison (RAAF officer)