Section 2-1 Microsoft Word document. Size:1.09MB

Section 2-1 Historical Wind Data for MCAS El Toro

Section 2-1.1 38-Year History Overview
Section 2-1.2 Wind Measurements

Attachments pertaining to Section 2-1:

Figure 2-1.1 Wind Rose - All Weather
Figure 2-1.2 Wind Rose - IFR conditions
Figure 2-1.3 Wind Records at MCAS El Toro
Figure 2-1.4 Wind Sensor at MCAS El Toro

Section 2-1.1 38-Year History Overview

Wind data is one the most important parameters that is required in designing an airport layout.

The thirty year historical wind data for El Toro MCAS on the attached two pages indicate that:

1. the winds are less than 10 knots 90.8 % of the time, and
2. the winds are less than 16 knots 94.35 % of the time, and
3. the cross winds on a North-South oriented runway would be less than 13 Knots more than 95 % of the time,
4. the winds during IFR conditions are less than 6 Knots 98.7 % of the time, and
5. the winds (when infrequently greater than 6 Knots) during IFR conditions are from the South,which would be consistent with an ILS approach to runway 16L from the North over Loma Ridge.
6. since the aerodynamic force from wind increases exponentially with the square of the velocity of the air, tail-winds become dangerous because they exponentially decrease the effectiveness of the rudder [when there is loss of thrust from a wing-mounted engine during the takeoff acceleration while the aircraft is still on the ground (between V1 and VR)] which can cause the aircraft to be driven off the side of the runway into a catastrophic ground-loop.
   

The Code of Federal Regulations 14, Part 151. Federal Aid to Airports, Paragraph151.79 (a) & (b) Runway paving: second runway; wind conditions indicates clearly that FAA grant funds would not be granted to re-grade and re-pave runways 07/25, because the cross winds on a North-South oriented runway would be less than 13 Knots more than 95 % of the time.

Section 2-1.2 Wind Measurements

The county’s Airport System Master Plan (ASMP) for El Toro, through Environmental Impact Report EIR 573, used historical wind measurements recorded by the Marines during military use of El Toro. These wind measurements were recorded using a sensor that is roughly 9 feet above ground level.

Since 1958, it has been documented by the Marines that the wind measuring sensor used was located 9.0 feet above ground, and was used as such, up until the closure of the base in 1996, and remained at the same height and location for over 38 years.

See Figure 2-1.1 Wind Rose - All Weather, and Figure 2-1.2 Wind Rose - IFR conditions.

Figure 2-1.3 shows the hourly wind observations at MCAS El Toro for all weather conditions from 1964 to 1994.

Based on the location of the sensor, it is important to note that the wind sensor is located in an area generally lower than the surrounding area.Figure 2-1.4 shows the wind sensor at MCAS El Toro and a horizontal level plane, parallel to the building roof tops and perpendicular to the vertical towers. This imaginary plane slopes from the top of the automobile wheels at the base of the control tower (through the pole holding the wind sensor) to the camera lens located 2 feet above the intersection of the centerlines of Runways 16L-34R and 7L-25R.

Since the imaginary plane passes through the 9-foot pole holding the wind sensor just above the 3-foot high box next to the wind sensor pole, the base of the wind sensor pole must be 3 feet below the level of the imaginary plane. This places the base of the 9-foot high wind sensor pole 1-foot below the sloping ground plane extending from the runway intersection to the control tower, but not necessarily below an average slopping ground-plane circle around the sensor with a radius of 500 feet.

This historical wind data collected by the Marines is significant, because it was provided to other federal agencies, including the National Atmospheric and Oceanic Administration (NOAA), became part of the federal wind measurement data base and then was used by the county in preparing the ASMP and EIR 573.

Compiled 08/10/01 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
Next: Section 2-2 Federal Regulatory Requirements for Measuring Wind Data

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