Responding to the concerns of pilots and the California Energy Commission (“CEC”) regarding the impact of exhaust plumes from power plants on overflying aircraft, the Federal Aviation Administration’s (“FAA”) Airport Obstruction Standard Committee (“AOSC”) completed a Supplement to FAA’s 2006 guidance [“Safety Risk Analysis of Aircraft Overflight of Industrial Exhaust Plumes”].  The purpose of the Supplement is to enhance current FAA regulations which only address standards for the physical height of the smoke stacks, and omit regulation of the impacts of the smoke plume emitted from the stacks, or the emissions contained in them. 

The Supplement is also aimed at obtaining definitive answers to the questions: (1) how much turbulence is created by exhaust plumes; (2) is this turbulence great enough to cause loss of pilot control; (3) if so, what size aircraft are impacted; (4) is there a lack of oxygen causing loss of engine power or danger to pilots/passengers; and, if so, (5) what is the harm to those pilots and passengers?

For two years, from 2008 to 2010, the AOSC conducted a Plume Report Study, which was ultimately determined to need further verification and validation.  In 2011, FAA retained the Federally funded Research and Development Center, operated by Mitre Corporation to answer the questions specified in the earlier Plume Report.  The Mitre Study was completed in September 2012 and verified both FAA’s model and what the earlier FAA reports and studies had concluded.

Early information released by FAA indicates that the Plume Report determined that: (1) exhaust plumes can create hazards for aircraft by turbulence caused by the plume’s upward motion and reduced oxygen inside in the plume, but only in a limited area above the stacks; (2) reduced oxygen is not a danger to pilots, but could adversely affect helicopter engines hovering over the plume; and (3) the most dangerous conditions include calm winds, low temperatures, and neutral or unstable stratification of the atmosphere. 

Despite the importance of these findings, not only to the general public but also to utilities and others in the business of constructing and operating power plants, rather than sharing the detailed results with those interest groups, FAA will host an “Invitation Only” meeting of aviation interest groups to “ensure their concerns are fully understood.”  Neither the public nor affected utility operators will be able to access the final Plume Report until FAA has consulted with its aviation interest groups.  Consequently, the result of the study may not reflect the interests and concerns of the utility industry, and may result in a significant impact on that industry segment’s ability to locate and operate power generation facilities throughout the country.

Hopefully, the latest version of the Plume Report will be based on quantitative analysis, and not diverted by the qualitative impressions of members of FAA’s aviation constituency.