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Section 2-2 Federal Regulatory Requirements for Measuring Wind Data

Section 2-2.1 FCM-S4-1994 Federal Regulatory Requirements Standards
Section 2-2.2 FAA Advisory Circular 91-54
Section 2-2.3 Conclusion
Section 2-2.4 FCM-S4-1994 Web Site
Section 2-2.5 Federal Web Site Links

Section 2-2.1 FCM-S4-1994 Federal Regulatory Requirements Standards

The federal government has adopted a federal standard for siting meteorological sensors at airports (FEDERAL STANDARDS FOR SITING METEOROLOGICAL SENSORS AT AIRPORTS FCM-S4-1994).

The standard specifies that "siting characteristics are essential for the establishment of a standardized meteorological data network and necessary for aviation and other weather forecasting purposes." Furthermore, it provides "the Federal standard for siting meteorological sensors of automated weather observing systems…to collect meteorological data in support of aircraft operations as well as aviation and other weather forecasting." This standard applies to all "Federally-funded systems," as well as "non-Federally systems that are to be approved by the Federal Aviation Administration…"

Therefor, since the County of Orange has received funding from the federal government for MCAS El Toro and anticipates receiving further future funding, this standard applies to the county’s proposed airport at El Toro.

This federal standard clearly specifies that wind sensors "will be mounted 30 to 33 feet (9-10 meters) above the average ground height within a radius of 500 feet (150 meters)." As noted in the previous Section 2-1, the Marines’ wind sensor was only 9 feet above average ground level, completely inconsistent with this standard. Furthermore, the location of the wind sensor pole used by the marines was below the average grade level.

Section 2-2.2 FAA Advisory Circular 91-54

Of equal importance is the FEDERAL AVIATION ADMINISTRATION ADVISORY CIRCULAR 91-54, which details automatic reporting systems - altimeter settings and other operational data. This Advisory Circular was issued in 1979.

This Advisory Circular specifies that wind sensors are to be located "which will provided the most representative wind information possible," and that they should be at least "20 feet and preferably 33 feet above the average ground level, within 500 feet of the sensor site."

Section 2-2.3 Conclusion

The Federal Standard for Siting Meteorological Sensors at Airports makes all of the wind data used in EIR 563 and 573 completely invalid, based on new information obtained recently by TNMG. The county’s Airport System Master Plan (ASMP) has been developed assuming that the winds recorded for over 30 years by the Marines can be applied to operations of large turbojet commercial aircraft. That assumption is now proven wrong.

A standard wind collection tower should be erected by the National Weather Service and new wind data must be collected. Then a new ASMP must be created that uses accurate wind information to arrive at the conclusions. This is a fatal flaw in EIR 573 that would be improper for the LRA to approve it without significant alterations. The FAA and the Navy cannot develop their required EIS (environmental impact statement) based upon a seriously flawed plan. The airport property cannot be conveyed to the County until the EIS is completed without legal challenges.

The recorded winds were taken by a sensor that is only 10.5 feet above the surface and is located in a depression. This is about 15 feet below the highest point within the required 500' radius, which makes it about 45 feet too low. The resulting wind readings are significantly lower than if they were taken at the official height. For example, the wind reported at 7 knots should have been more like 9 to 12 knots and the direction would also have been incorrect. Whenever tailwinds exceed 10 knots on a runway takeoffs and landings cannot be made. Every knot of tailwind requires large weight reductions. The original decision to operate the new airport, with the wind instead of into the wind, is contrary to conventional aviation standards and was based on the apparent light and misleading historical wind records. Just one knot of tailwind requires the usage of maximum takeoff power, which increases the chances of engine damage and creates far more air and noise pollution.

Section 2-2.4 FCM-S4-1994 Web Site

The complete text of FCM-S4-1994 Federal Standard for Meteorological Siting of Sensors can be found at: http://205.156.54.206/pub/ofcm/FCMS4.TXT

Excerpts from the above web site:

"This document establishes the Federal standard for siting meteorological sensors of automated weather observing systems at airports/heliports to collect meteorological data in support of aircraft operations as well as aviation and other weather forecasting. It will be used by Federal agencies as a basis for developing and implementing specific regulatory or technical documents."

"The standard applies to all Federally-owned and Federally-funded systems, as well as non-Federal systems that are to be approved by the Department of Transportation's (DOT) Federal Aviation Administration (FAA) or the Department of Commerce's (DOC) National Weather Service (NWS). Multiple users of meteorological data exist, and to the greatest practical extent, they have been considered in the development of this standard."

"This standard is intended to serve as the most fundamental reference for sensor siting. While this document is not of itself regulatory in nature, it is to be implemented through appropriate agency orders. Likewise, this standard may be modified or enhanced by agency directives. This document does not require agencies to change existing sensor installations solely to comply with this standard. It will be applied as new stations are established. The inclusion and description of a particular sensor in this document does not imply that such sensors will be used in all system applications."

"In applying this document to the planning of an automated weather observing system site at an airport with a control tower, no site shall be finalized without consulting with representatives of both NWS and FAA."

"Sensor siting in accordance with this standard meets the requirements of Section 77.15(c) of the Federal Aviation Regulations (FAR) and is exempt from further Part 77 study. Any exceptions to the standard or special situations will require an FAA Obstruction Evaluation/Airport Airspace Analysis (OE/AAA) study in accordance with Part 77 of the FAR to determine if a substantial adverse effect would be created for aircraft operations."

"Sensor siting shall not violate runway or taxiway object free areas, runway or taxiway safety areas, obstacle free zones, or instrument flight procedures surfaces as defined in FAA Advisory Circular (AC) 150/5300-13, Airport Design, or FAA Handbook 8260.3, TERPS."

"Notwithstanding these constraints, the sensor exposure will strive to minimize or eliminate the effects of manmade or geographical obstructions. The tower used to mount the wind sensor is not considered an obstruction to the sensor collection system, but it will (with the exception of the temperature, dew point, and pressure sensors) be at least 10 feet (3 meters) away from the other sensors. Sensors should be located as far as practicable from cultivated land to reduce contamination by dust and dirt. It may be necessary to increase the heights of some sensors based on the average maximum snow depth for the location, which will be determined by averaging the maximum annual snow depths over the period of record."

"The wind sensors (wind direction and wind speed) will be oriented with respect to true north. The system software will be used to make required adjustments to magnetic north. The site should be relatively level, but small gradual slopes are acceptable. It will be mounted 30 to 33 feet (9 to 10 meters) above the average ground height within a radius of 500 feet (150 meters). The sensor height shall not exceed 33 feet (10 meters) except as necessary to: (a) be at least 15 feet (4.5 meters) above the height of any obstruction (e.g., vegetation, buildings, etc.) within a 500 foot (150 meters) radius, and (b), if practical, be at least 10 feet (3 meters) higher than the height of any obstruction outside the 500 foot (150 meter) radius, but within a 1,000 foot (300 meter) radius of the wind sensor."

"The minimum acceptable height for the wind sensor in this situation is 20 feet (6 meters). If side mounting (i.e., perpendicular to a tower) is necessary, a boom will be used to permit installation of the sensor at a minimum of 3 feet (1 meter) laterally from the tower. Side mounting is to be utilized only if top mounting is not practicable and the tower is of open design to allow for free airflow."

Section 2-2.5 Federal Web Site Links

Federal standard for siting meteorological sensors at airports:
http://www.ofcm.gov/siting/text/a-cover.htm

Office of the Federal Coordinator for Meteorology:
http://www.ofcm.gov

The National Weather Service:
http://WWW.nws.noaa.gov

Federal Meteorological Handbook:
http://205.156.54.206/oso/oso1/oso12/fmh1/fmh1toc.htm

Federal Standard for Siting Meteorological Sensors at Airports:
http://www.ofcm.gov/fp-fy97/text/app-c.htm

Siting of wind generators-mentions height increases wind:
http://solstice.crest.org/renewables/re-kiosk/wind/theory/siting.shtml

Compiled 09/26/01 The New Millennium Group
Written by: Charles E. Griffin and Russell Niewiarowski

The entire Engineering Section containing all section, is available on CD-ROM.

griffin@ocxeltoro.com for a CD-ROM copy
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