For a while now, an ASTM committee that develops the standards for light sport aircraft to operate under instrument flight rules has struggled to reach consensus on a key point -- whether Special-LSAs should be allowed to fly in actual instrument meteorological conditions -- and although the committee members still disagree, they have decided to move forward and change the standards to prohibit the use of S-LSAs in IMC. That proposed change now must go through some further approvals and then be submitted to the FAA for an OK before it takes effect. That process could take until the end of this year or perhaps longer, Dan Johnson, chairman of the Light Aircraft Manufacturing Association, told AVweb on Wednesday. The change will not be retroactive, Johnson said. Any S-LSA that is flying today, or that is built before the new standard takes effect, is not prohibited from IMC flight if the aircraft is properly equipped and flown by a qualified pilot (although manufacturers may choose to prohibit IMC flight in their aircraft even when the ASTM standard allows it).
The IMC change is driven more by committee members' concerns about liability than about safety, Johnson said. FAA officials have not expressed any safety concerns about LSAs operating in instrument conditions, he said. "This is a complex topic that will continue to stimulate debate," Johnson wrote at his blog. The important fact to remember, he said, is that the change is not retroactive. Johnson further told AVweb that under the ASTM process, the standard could change again in the future, in as little as 30 days, if a new consensus is reached on the issue.