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Navigational Aids

Medivac Operations

Precision Approach Path Indicators (PAPIs)

A PAPI is a system of lights that provide visual descent guidance information during the approach to a runway. This system provides a visual glide path that allows for safe obstruction clearance from the start of descent to the threshold. Both Runway 11 and Runway 29 are equipped with 2-box PAPIs installed to the left of the threshold.

Runway End Identifier Lights

REILs are installed at many airfields to provide rapid and positive identification of the approach end of a particular runway. They are effective for:

  • Identification of a runway surrounded by a preponderance of other lighting
  • Identification of a runway which lacks contrast with surrounding terrain
  • Identification of a runway during reduced visibility

These lights consist of a pair of synchronized flashing lights located on each side of the runway threshold facing the approach area. Both Runway 11 and Runway 29 have omnidirectional REILs. In June 2005 the REIL system was replaced with funding assistance from the Maryland Aviation Administration to allow for improved pilot control. Pilots may now adjust the intensity of the lights as they approach for landing by keying or "clicking" the aircraft's microphone in accordance with the Pilot Control Lighting Operating Procedures outlined below.

Runway Edge Lights

Runway edge lights are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity or brightness they are capable of producing: they are the High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and the Low Intensity Runway Lights (LIRL).Runway 11-29 at St. Mary's County Airport is equipped with MIRLs. In addition, the Airport is equipped with runway threshold lights at each runway end.

Taxiway Edge Lights

Taxiway edge lights are used to outline the edges of taxiways. Similar to runway edge lights, these light systems are classified according to the intensity of light they are capable of producing. Limited quantities of MITLs have been installed at St. Mary's County Airport to delineate the taxiway turnoffs as well as the midfield connector.

Obstruction Marking and Lighting

In administering Title 14 of the Code of Federal Regulations CFR Part 77, the prime objectives of the FAA are to promote air safety and the efficient use of the navigable airspace. To accomplish this mission, aeronautical studies are conducted based on information provided by proponents on an FAA Form 7460-1, Notice of Proposed Construction or Alteration. Advisory Circular 70/7460-1K, Obstruction Marking and Lighting, describes the standards for marking and lighting structures such as buildings, chimneys, antenna towers, cooling towers, storage tanks, supporting structures of overhead wires, etc. A new Part 77 final Rule was published on July 21, 2010, and will become effective on January 18, 2011.

Who Needs to File an FAA Form 7460-1

CFR Title 14 Part 77.13 states that any person/organization who intends to sponsor any of the following construction or alterations must notify the Administrator of the FAA:

  • any construction or alteration exceeding 200 ft. above ground level
  • any construction or alteration:
  • within 20,000 ft of a public use or military airport which exceeds a 100:1 surface from any point on the runway of each airport with at least one runway more than 3,200 ft
  • within 10,000 ft of a public use or military airport which exceeds a 50:1 surface from any point on the runway of each airport with its longest runway no more than 3,200 ft
  • within 5,000 ft of a public use heliport which exceeds a 25:1 surface any highway, railroad or other traverse way whose prescribed adjusted height would exceed the above noted standards
  • when requested by the FAA any construction or alteration located on a public use airport or heliport regardless of height or location.

Runway and Taxiway Edge Markers

In 2010, the County received special grant funding from the Maryland Aviation Administration to purchase retroreflective markers to delineate the edges of the runway and taxiway. The markers are a safety enhancement intended to benefit the users of the St. Mary's County Regional Airport. The markers are 2.25-inch diameter colored flexible polyethylene tubes with bands of colored retroreflective material which were FAA Tested & Certified per FAA AC 150/5345-39. The colored bands provide daytime marking, improve ground navigation and also function as snow markers for aircraft and plows during the winter months.

Control of Airport Lighting Systems

The St. Mary's County Airport does not have an operating control tower. Therefore, radio control of lighting is provided via airborne control of lights by keying the aircraft's microphone. This eliminates the need for pilots to change frequencies to turn the lights on and allows a continuous listening watch on a single frequency. At St. Mary's County Airport, the MIRLs and REILs can be activated using the designated Common Traffic Advisory Frequency (CTAF), 123.0. At this airport, the CTAF is a UNICOM frequency. In addition, the MIRLs and REILs are controlled by a photo cell and are automatically turned on at dusk and during adverse weather.

Pilot Control Lighting Operating Procedures

Runway Lights

The runway lights are controlled by a photo eye. From dusk until dawn, the runway lights are turned on to the medium setting by the photo eye. The runway lights cannot be changed. During times of heavy overcast, the photo eye may allow the runway lights to come on during "daylight hours".

Runway End Identifier Lights (REIL) Strobes

The REILs are controlled via the CTAF (Common Traffic Advisory Frequency) by "clicking" the microphone, a set timer, and by a photo eye.

Radio Control System

Key Mike Function
3 times within 5 seconds Highest intensity available
5 times within 5 seconds Medium or lower intensity (Lower REIL or REIL - off)
7 times within 5 seconds Lower intensity available (Lower REIL or REIL - off)

NOTE: At any time in the sequence the pilot has the option of sending three, five, or seven pulses to command the intensity level to his/her requirements. The system will remain at the intensity level of the last command received. The solid state timer will continue to operate for 15 minutes after which it will cause the system to revert to the original "off" condition. The timer is reset by the receipt of any command at anytime, reinitiating the 15 minute "run" cycle. A photo eye keeps the REILs from operating during the day, but may allow them to operate during periods of heavy overcast.

Airport (Rotating) Beacon

The airport beacon is installed to indicate the airport's location to aircraft pilots at night. The airport beacon is located on top of a dedicated towering structure on the south west side of the runway. The beacon has two 10-inch metal halide lamps that produce 13,000 lumens each. A photocell controls the rotating beacon operation of an alternating green and white light that rotates 24-30 flashes per minute. It operates from dusk until dawn and may come on during periods of heavy overcast. There are no controls to operate the beacon during daylight IFR conditions.

A new rotating beacon was commissioned on May 27, 2011

Wind Cone and Segmented Circle

The lighted wind cone and segmented circle is used to aid pilots in determining takeoff and landing information at an airport. St. Mary's County Airport's lighted wind cone and segmented circle is located to the north of Runway 11-29 and is in good working condition.

Instrument Approach Procedures

An Instrument Approach Procedure (IAP) is a flight procedure that provides a transition from the en-route flight environment to a point from which a safe, normal landing can be accomplished. U.S. Civil Standard Instrument Approach Procedures are designed and approved for public use by the Federal Aviation Administration (FAA) and are unique to each airport.

While these procedures can be flown during good weather conditions, the instrument approach procedures are especially important during Instrument Meteorological Conditions (IMC). When the cloud ceilings are low and visibility is minimal, all flights must follow Instrument Flight Rules (IFR), and therefore must utilize published instrument approach procedures when transitioning to the landing environment. The FAA has established ceiling and visibility minimums for each individual instrument approach procedure. Currently, there are two (2) published instrument approach procedures for St. Mary's County Airport. These procedures are listed below with the corresponding landing minimums:

LPV 480 FT 1 1/2 MILE

Standard instrument approach procedures are primarily based upon either an on-airport or nearby electronic navigational aid (NAVAID) or the Global Positioning System (GPS). Therefore, the type of instrument approach procedure is determined by what the procedure is based upon.

The instrument approach procedures can be flown using the Global Positioning System (GPS). GPS is a system of 24 satellites, orbiting the earth, which emit signals to receivers below. By measuring the travel time of a signal transmitted from each satellite, a receiver in the aircraft can calculate its distance from that satellite. When receiving the signals from at least four (4) satellites, a receiver can determine latitude, longitude, altitude and time.

The basic GPS service provides users with approximately 100 meter (328 feet) accuracy 95% of the time anywhere on or near the surface of the earth.

NOTAMS (Notice To Airmen)

In the event that conditions at the Airport are determined to be unsafe for landings or takeoffs, the airport owner is responsible for providing warning to users, such as adequate marking and issuing a Notice To Airmen to advise pilots of the condition. Where climatic conditions render the airport unsafe, the owner will promptly notify airman by proper notices and, if necessary, close the Airport, or any portion thereof, for a reasonable period of time or until those unsafe conditions can be corrected or no longer exist. Additional information can be obtained from the following Aircraft Owners and Pilots Association web-site.

Current NOTAM's are required by the Federal Aviation Administration and are available from Flight Services Stations at 1-800-WX-BRIEF. Notices restrictions, and advisories may be changed at any time and without notice. Do not attempt any operation in the National Airspace System without first obtaining and understanding a thorough pre-flight briefing. Pilots may also wish to view current NOTAM's for St. Mary's Regional Airport at the FAA website and by typing in "2W6" in the Flight Safety NOTAMs box.


Security-related procedures and requirements are a fact of life for today's pilots, especially those who operate in the Washington, DC Metropolitan Area Special Flight Rules Area (DC SFRA) and the DC Flight Restricted Zone (DC FRZ). Pilots at St. Mary's airport are affected by the DC SFRA rules.

St. Mary's airport is within the 60NM ring of the DC SFRA. Any pilot flying VFR within this airspace is required to complete the DC SFRA course. The primary reason is that this airspace is closely monitored and there are serious consequences for violating the established operating requirements and procedures. The FAA made this course mandatory in order to ensure that pilots understand those requirements and procedures. Anyone can complete this on-line course by going to

The Special Flight Rules Area (SFRA) is codified in 14 CFR part 93. The SFRA, which includes the Flight Restricted Zone (FRZ), is National Defense Airspace. There are serious consequences for violating the established operating requirements and procedures. Check Notices to Airmen (NOTAMs) before every flight.

Laterally, the SFRA is the airspace within a 30-nm radius of the DCA VOR/DME. Vertically, it starts at the surface and goes to, but does not include, flight level 180.

The chart includes markings for a ring located 60 nm from the DCA VOR/DME. The 60 nm ring is charted because of VFR operational (speed) restrictions. Between 60 nm and 30 nm, VFR operations are restricted to 230 knots IAS unless otherwise authorized by ATC. Inside 30 nm, all VFR operations are restricted to an 180 knots IAS or less, unless otherwise authorized by ATC.

To fly IFR to, from, within, or through the SFRA, the aircraft must have an operable two-way radio capable of communicating with ATC on appropriate radio frequencies and an operating automatic altitude reporting transponder. Normal IFR procedures are the same; however, file and activate the IFR flight plan before entering the SFRA, and transmit the assigned discrete beacon code while flying in the SFRA. Never use 1200.

Aircraft must have an operable two-way radio capable of communicating with ATC on appropriate radio frequencies, and an operating automatic altitude reporting transponder. File a SFRA flight plan, which is filed for the sole purpose of complying with the requirements for VFR operations in the SFRA. It does not provide any ATC or search and rescue services. See the course notes for specific reminders on how to file a SFRA flight plan, including use of the directional entry/exit "gates" that pilots use to file the SFRA entry or exit point on SFRA flight plans, identify position and direction of entry or exit when contacting ATC, and void congestion over specific points. There is no need to fly directly to, or directly over, the specific fix for which a gate is named.

Activate the SFRA flight plan by contacting ATC to obtain the discrete transponder code assigned to your flight. Call ATC after takeoff. Check in and monitor the frequency. The controller will advise when you are outside the SFRA boundary. Once outside the SFRA flight plan is considered closed. No further action is required. The VFR inbound procedure is similar.

UNICOM Communication

The airport is served by a UNICOM radio licensed by the Federal Communications Commission for frequency 123.0 MHz through July 8, 2023. All pilots of aircraft having radio equipment permitting two-way communications should contact the Airport UNICOM to obtain advisory information and announce their intentions when within ten (10) miles of the Airport. Pilots are also encouraged to maintain a listening watch on the frequency when operating within a ten mile radius of the Airport. All departing aircraft shall announce on the UNICOM their intention and runway to be used for departure. In communicating with a UNICOM station, the following practices will help reduce frequency congestion, facilitate a better understanding of pilot intentions, help identify the location of aircraft in the traffic pattern, and enhance safety of flight:

Select the correct CTAF frequency. State the identification of the UNICOM station you are calling in each transmission. Speak slowly and distinctly. Notify the UNICOM station approximately 10 miles from the airport, reporting altitude, aircraft type, aircraft identification, location relative to the airport, and whether landing or over-flight. Request wind information and runway in use. Report on down-wind, base, and final approach. Report leaving the runway.

GCO (Ground Communications Outlet)

The airport is served by a GCO licensed by the Federal Communications Commission for frequency 121.725 MHz through October 10, 2018. The GCO allows pilots to communicate directly with air traffic controllers located at the Patuxent River Naval Air Station. The GCO at the Captain Walter F. Duke Regional Airport @ St. Mary's was provided by the Maryland Aviation Administration and installed and commissioned in 2004 as a part of a cooperative effort between Naval Air Station, the Airport Advisory Committee, and County Airport staff. The system is an affordable way to access ATC from the ground. By making such remote access available, pilots won't have to chose between climbing out of the airplane to make a phone call or launching into marginal conditions to gain the altitude needed for radio contact. Pilots must obtain a clearance to depart, prior to entering clouds or areas of poor visibility (instrument conditions). Pilots needing a clearance can tune in aviation frequency 121.725 MHz and key their microphone four times. The GCO recognizes the clicks and automatically dials a restricted number. The pilot then has the ability to communicate directly with the controller.

How to Use the system:

  1. Pilots on the ground at St. Mary's should tune a COM radio to Frequency 121.72 MHz and slowly click the microphone FOUR times ( ie. one click per second).
  2. You will hear approximately two rings of the phone line.
  3. A controller from Pax River NAS will answer you can then begin your communication.
  4. After you complete your communications, the controller will hang up and the system will automatically disconnect. Note: If there is no communication for more than approximately 30 seconds, the system will automatically disconnect.

AWOS (Automatic Weather Observation System)

The airport is served by an AWOS licensed by the Federal Communications Commission for VHF frequency 453.1125 MHz and UHF frequency 119.575 MHz through February 15, 2024 and September 19, 2015, respectively. The AWOS will provide information on wind speed and gusts, wind direction, air temperature, dew point, precipitation, barometric pressure, visibility, cloud/ceiling height etc. The sensor data is processed in accordance with ICAO and WMO regulations. The data is displayed as instant values in a monitoring window, formatted and automatically assembled into various reports. The operator can switch the system into a semiautomatic mode and supplement the automatic data with his/her own observations. All parameters are stored in a direct access database and can be displayed graphically. The generated reports (METAR, SYNOP, METREPORT, SNOWTAM, CLIMATE) are transmitted to a meteorological network (AFTN, METCOM) and distributed locally (workstations, CCTV). AWOS sends coded messages to other systems such as the ATIS speech synthesizer or radar processing units. The AWOS system also allows also for remote control, monitoring and surveillance of sensors.

Wireless Network (WIFI) A wireless network has been established at both the terminal building and the county hangar. A WIFI connection is available free to the general public for mobile device access. A computer terminal has been installed at the pilot's lounge and Piedmont Flight Center where pilots can readily access on-line applications for weather briefings and flight planning. A telephone is available in the pilot's lounge with free access to local and 800 numbered calls. The pilot's lounge is located within the county hangar office spaces.