Source: Delta Airport Consultants, Inc. analysis

The airport can also be reached by calling FBO at (301) 373-2101 for general airport information or operational requests. Weather sources for St. Mary’s County Airport include the Leesburg Flight Service Station (DCA) which can be reached via telephone at (800) WX-BRIEF. Currently, the nearest automatic weather reporting is located at Patuxent River Naval Air Station (ATIS). The Airport has installed an Automatic Weather Observation Station (AWOS) (301-373-6514) on-site to provide up-to-date weather reporting to pilots utilizing St. Mary’s County Airport. The project was funded and coordinated by the Maryland Aviation Administration.
  

AIRFIELD  INFORMATION
   

Taxiway System

FAA AC 150/5300-13 "Airport Design" also presents design standards for taxiway and taxi-lane development. A taxiway is defined as a path established for the taxiing of aircraft from one part of the airport to another. A taxi-lane is defined as the portion of the aircraft movement area used for the access between taxiways and aircraft parking positions.

The airport has one partial parallel taxiway, three connector taxiways and a turnaround. The current parallel taxiway to runway centerline separation is 207 feet. This does not meet the 240 feet separation required by design standards for B-II airports with not lower than 3/4 statute mile approach visibility minimums. The Airport currently has a "Modification of Standard" (MOS) for this runway/taxiway separation. In addition, the MOS requires that all future taxiway extensions be at the required 240’ separation.

Runway Designation

Runway numerals for each runway end are determined from the approach direction to the runway end and should be equal to one-tenth of the magnetic azimuth of the runway centerline, measured in a clockwise direction from magnetic north. Although the true bearing of the runways will not change over time, the magnetic bearing will change as the location of magnetic north shifts. The magnetic declination in the vicinity of the Airport is 10.7 degrees west (1999). The Runway Bearings Table (below) provides a summary of bearing information for St. Mary’s County Airport. Based on this analysis, the designations for Runway 11-29 are correct. The FAA Published Weight Bearing Capacity: Single Wheel gear is: 12,500 lbs.

Wind Analysis

The orientation of the runway to the prevailing wind direction is critical to the safe operation of aircraft, especially small single engine aircraft which are more susceptible to crosswinds. Crosswinds are winds which tend to be perpendicular to the runway or path of an aircraft while landing or taking off. Wind data for the analysis was obtained from the National Climatic Data Center in Asheville, North Carolina for Patuxent River Naval Air Station (NAS) for the period 1988 through 1997.

The FAA recommends 95 percent wind coverage for various crosswind components based on specific airport reference codes (ARC). The 95 percent wind coverage is computed on the basis of the crosswind not exceeding 10.5 knots for ARC A-I and B-I, 13 knots for ARC A-II and B-II, 16 knots for ARC A-III, B-III, and C-I through D-III, and 20 knots for ARC A-IV through D-VI as detailed in AC 150/5300-13 "Airport Design."

The present ARC classification for St. Mary’s County Airport is B-II. Using the above referenced criteria, wind coverage would be computed for a 13 knot crosswind component. Although the wind coverage criteria recommends coverage based on the ARC of the runway, the runway has also been evaluated for a more conservative 10.5 knot crosswind. This is warranted due to the number of smaller single engine piston and twin engine piston aircraft that utilize the airport on a regular basis and are more susceptible to crosswinds.

Based on this analysis, Runway 11-29 meets the 95 percent wind coverage for B-II runways. Therefore, no additional runways are required due to lack of wind coverage. Although the runway orientation does not provide for 95 percent wind coverage for the 10.5 knot crosswind condition, the runway width of 75 feet provides the Group I aircraft an increased margin of safety. The standard runway design width for Group I aircraft is typically 60 feet.

IFR conditions (when visibility is less than three (3) statute miles and the cloud ceiling is less than 1,000 feet) occur approximately 7.8 percent of the time according to the National Climatic Data Center weather information. The airport is below a 200 foot ceiling and/or one-half mile visibility approximately 1.2 percent of the time during the average year.

 
Airfield Pavements

As part of the Airport Master Plan effort, a Pavement Management Plan is developed. The general condition of the various pavements has been inventoried with a cursory visual inspection. "Excellent" condition connotes new pavement with no cracks or distress. "Good" pavement shows few signs of distress and cracks while "Fair" pavement has minor cracking and shows signs of distress.

Source: Airport Records / Delta Airport Consultants, Inc.