INTERNATIONAL
Airstrip Gradient Calculation by Mike Feeney
The history of this simple graph goes back to 1981 when, working for the NZ Civil Aviation Division of the Ministry of Transport, I devised a similar ‘user-friendly’ means for pilots to quickly determine to what extent airstrip slope increased its effective operational length. It was published in articles I wrote for their “Flight Safety” journal and was primarily intended as an aid for the training of pilots undergoing specialized flight instruction for an Agricultural Pilot Rating. In the early 2000s, I joined Wanganui Aero Work, a large New Zealand operator of fixed-wing agricultural aircraft and Part 135 helicopters. In my role as as Quality Assurance and Safety Manager, I was involved in airstrip standards, including advising growers on improvement methods and, on a few occasions, the siting and works planning for new airstrips. At this time, A 16 | agairupdate.com
there were no country-wide standards for farm airstrips; particularly for the increasing number of heavy turbo-prop aircraft which are unable to economically operate from many of the historic strips which suited types such as the Fletcher FU24, DHC-2 Beaver, Cessna 188 Agwagon, etc. Some pilots may operate their aircraft from sloping rural airstrips. This article may well prove of interest to them. If you are not sure how to work out the gradient of an airstrip, there is an easy method which you can use. Simply note your altimeter reading at the top and bottom of the airstrip (or you could use your GPS if you are viewing several satellites), then walk out the length and use the formula: Height difference divided by airstrip length and multiply by 100. Example for a typical airstrip: Length = 1,300 feet. Height difference = 90 feet
