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Tundra tire
Maule M-7-235C Orion C-FSRA 04.JPG
Maule M-7-235C on tundra tires

A tundra tire (UK: tundra tyre) is a large low-pressure tire used on light aircraft to allow operations on rough terrain.[1]

Contents

History

The tundra style tire has been independently invented at different times and places. In North America its invention is credited to Canadian Welland Phipps.[1]

Phipps designed and constructed his own balloon tires in the period after the Second World War and fitted them to a Piper PA-18 Super Cub. Phipps then went on to provide air transportation to much of the Canadian high arctic region. He later established his own airline Atlas Aviation, which operated a fleet of De Havilland Canada DHC-6 Twin Otters on balloon tires. Using the tires, Atlas's DHC-6s established airline service to such remote communities as Resolute, Nunavut and Grise Fiord, Nunavut.[1]

Airworthiness issues

In the United States and particularly in Alaska, tundra tires of various designs were often installed under local field approvals by Federal Aviation Administration inspectors. These approvals were usually granted on the basis of visual inspections and did not include flight testing. After a number of accidents with tundra tire equipped aircraft, culminating with a large number in the fall of 1994, the National Transportation Safety Board identified that the tundra tires were connected with the accidents. Starting in April 1995 the FAA carried out flight test experiments to determine whether the tundra tires were a contributing factor.[1]

The tests used a Piper PA-18-150 Super Cub equipped in sequence with five different sets of tires, including standard factory tires and tundra tires up to 35 in (89 cm) diameter. The PA-18 was operated at different weights and center of gravity positions.[1]

The testing on the ground revealed that the larger the tire the more restricted the forward visibility on the ground, that there was a nose-down pitching moment when the tires contacted the ground on landing, particularly on a wheel landing, and that tundra tire-equipped aircraft have substantially poorer ground handling characteristics on pavement. In the air the use of tundra tires reduced top speed, rate of climb, angle of climb, range, useful load and stall warning buffet margins.[1]

The tests did not indicate that tundra tires raise stall speed, but did find that, due to increased drag in turns, the aircraft nose tends to drop excessively with an increase in bank angle. If the pilot counteracts this tendency with rudder and stalls the aircraft, the airplane will rapidly enter a spin.[1]

Alaska bush pilots disputed the experimental findings, but, as a result of these experiments the FAA required that all installed tires be subject to a Technical Standard Order or Parts Manufacturer Approval, have been flight tested and subject to a weight and balance report, determining an acceptable flight envelope. The FAA also limited tundra tires to 35 in (89 cm) in diameter.[1]

Operators

Until the end of the 20th century tundra tires were mostly used by bush operators flying in remote areas. In the early part of the 21st century many sales of tundra tires have been to recreational pilots. Bill Duncan, president of Alaskan Bushwheels a tundra tire manufacturer explains:[1]

"It’s the baby boomers. Here you have a group of people that lost their shirts in the stock market after 9/11 but still have disposable income and are tired of sitting in the office watching the clock. They’ve figured out that a light utility aircraft—a Super Cub, a Husky, a Maule or a Scout, to name the top four, will keep its value over time and may even appreciate in value. And they want to get outside and play."[1]

Charles McDowell, an Aviat Husky pilot stated:

There’s the coolness factor, plus it’s nice to have a little more capability than you may need...We want a rugged plane because it makes us feel a little more independent from the infrastructure.[1]

References

  1. ^ a b c d e f g h i j k Richfield, Paul (September 2005). "Tundra Tire Nation". http://www.flyingmag.com/article.asp?section_id=13&article_id=576. Retrieved 2009-12-13.  
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