Section 2. Special Operations

  1. Offshore Helicopter Operations
    1. Introduction
      The offshore environment offers unique applications and challenges for helicopter pilots. The mission demands, the nature of oil and gas exploration and production facilities, and the flight environment (weather, terrain, obstacles, traffic), demand special practices, techniques and procedures not found in other flight operations. Several industry organizations have risen to the task of reducing risks in offshore operations, including the Helicopter Safety Advisory Conference (HSAC) (, and the Offshore Committee of the Helicopter Association International (HAI) ( The following recommended practices for offshore helicopter operations are based on guidance developed by HSAC for use in the Gulf of Mexico, and provided here with their permission. While not regulatory, these recommended practices provide aviation and oil and gas industry operators with useful information in developing procedures to avoid certain hazards of offshore helicopter operations.


      Like all aviation practices, these recommended practices are under constant review. In addition to normal procedures for comments, suggested changes, or corrections to the AIM (contained in the Preface), any questions or feedback concerning these recommended procedures may also be directed to the HSAC through the feedback feature of the HSAC website (

    2. Passenger Management on and about Heliport Facilities
      1. Background. Several incidents involving offshore helicopter passengers have highlighted the potential for incidents and accidents on and about the heliport area. The following practices will minimize risks to passengers and others involved in heliport operations.
      2. Recommended Practices
        1. Heliport facilities should have a designated and posted passenger waiting area which is clear of the heliport, heliport access points, and stairways.
        2. Arriving passengers and cargo should be unloaded and cleared from the heliport and access route prior to loading departing passengers and cargo.
        3. Where a flight crew consists of more than one pilot, one crewmember should supervise the unloading/loading process from outside the aircraft.
        4. Where practical, a designated facility employee should assist with loading/unloading, etc.
    3. Crane-Helicopter Operational Procedures
      1. Background. Historical experience has shown that catastrophic consequences can occur when industry safe practices for crane/helicopter operations are not observed. The following recommended practices are designed to minimize risks during crane and helicopter operations.
      2. Recommended Practices
        1. Personnel awareness
          1. Crane operators and pilots should develop a mutual understanding and respect of the others' operational limitations and cooperate in the spirit of safety;
          2. Pilots need to be aware that crane operators sometimes cannot release the load to cradle the crane boom, such as when attached to wire line lubricators or supporting diving bells; and
          3. Crane operators need to be aware that helicopters require warm up before takeoff, a two-minute cool down before shutdown, and cannot circle for extended lengths of time because of fuel consumption.
        2. It is recommended that when helicopters are approaching, maneuvering, taking off, or running on the heliport, cranes be shutdown and the operator leave the cab. Cranes not in use must have their booms cradled, if feasible. If in use, the crane's boom(s) are to be pointed away from the heliport and the crane shutdown for helicopter operations.
        3. Pilots will not approach, land on, takeoff, or have rotor blades turning on heliports of structures not complying with the above practice.
        4. It is recommended that cranes on offshore platforms, rigs, vessels, or any other facility, which could interfere with helicopter operations (including approach/departure paths):
          1. Be equipped with a red rotating beacon or red high intensity strobe light connected to the system powering the crane, indicating the crane is under power;
          2. Be designed to allow the operator a maximum view of the helideck area and should be equipped with wide-angle mirrors to eliminate blind spots; and
          3. Have their boom tips, headache balls, and hooks painted with high visibility international orange.
    4. Helicopter/Tanker Operations
      1. Background. The interface of helicopters and tankers during shipboard helicopter operations is complex and may be hazardous unless appropriate procedures are coordinated among all parties. The following recommended practices are designed to minimize risks during helicopter/tanker operations:
      2. Recommended Practices
        1. Management, flight operations personnel, and pilots should be familiar with and apply the operating safety standards set forth in “Guide to Helicopter/Ship Operations”, International Chamber of Shipping, Third Edition, 5-89 (as amended), establishing operational guidelines/standards and safe practices sufficient to safeguard helicopter/tanker operations.
        2. Appropriate plans, approvals, and communications must be accomplished prior to reaching the vessel, allowing tanker crews sufficient time to perform required safety preparations and position crew members to receive or dispatch a helicopter safely.
        3. Appropriate approvals and direct communications with the bridge of the tanker must be maintained throughout all helicopter/tanker operations.
        4. Helicopter/tanker operations, including landings/departures, must not be conducted until the helicopter pilot-in-command has received and acknowledged permission from the bridge of the tanker.
        5. Helicopter/tanker operations must not be conducted during product/cargo transfer.
        6. Generally, permission will not be granted to land on tankers during mooring operations or while maneuvering alongside another tanker.
    5. Helideck/Heliport Operational Hazard Warning(s) Procedures
      1. Background
        1. A number of operational hazards can develop on or near offshore helidecks or onshore heliports that can be minimized through procedures for proper notification or visual warning to pilots. Examples of hazards include but are not limited to:
          1. Perforating operations: subparagraph f.
          2. H2S gas presence: subparagraph g.
          3. Gas venting: subparagraph h; or,
          4. Closed helidecks or heliports: subparagraph i (unspecified cause).
        2. These and other operational hazards are currently minimized through timely dissemination of a written Notice to Air Missions (NOTAM) for pilots by helicopter companies and operators. A NOTAM provides a written description of the hazard, time and duration of occurrence, and other pertinent information. ANY POTENTIAL HAZARD should be communicated to helicopter operators or company aviation departments as early as possible to allow the NOTAM to be activated.
        3. To supplement the existing NOTAM procedure and further assist in reducing these hazards, a standardized visual signal(s) on the helideck/heliport will provide a positive indication to an approaching helicopter of the status of the landing area. Recommended Practice(s) have been developed to reinforce the NOTAM procedures and standardize visual signals.
    6. Drilling Rig Perforating Operations: Helideck/Heliport Operational Hazard Warning(s)/Procedure(s)
      1. Background. A critical step in the oil well completion process is perforation, which involves the use of explosive charges in the drill pipe to open the pipe to oil or gas deposits. Explosive charges used in conjunction with perforation operations offshore can potentially be prematurely detonated by radio transmissions, including those from helicopters. The following practices are recommended.
      2. Recommended Practices
        1. Personnel Conducting Perforating Operations. Whenever perforating operations are scheduled and operators are concerned that radio transmissions from helicopters in the vicinity may jeopardize the operation, personnel conducting perforating operations should take the following precautionary measures:
          1. Notify company aviation departments, helicopter operators or bases, and nearby manned platforms of the pending perforation operation so the Notice to Air Missions (NOTAM) system can be activated for the perforation operation and the temporary helideck closure.
          2. Close the deck and make the radio warning clearly visible to passing pilots, install a temporary marking (described in subparagraph 10-2-1i1(b)) with the words “NO RADIO” stenciled in red on the legs of the diagonals. The letters should be 24 inches high and 12 inches wide. (See FIG 10-2-1.)
          3. The marker should be installed during the time that charges may be affected by radio transmissions.
        2. Pilots
          1. When operating within 1,000 feet of a known perforation operation or observing the white X with red “NO RADIO” warning indicating perforation operations are underway, pilots will avoid radio transmissions from or near the helideck (within 1,000 feet) and will not land on the deck if the X is present. In addition to communications radios, radio transmissions are also emitted by aircraft radar, transponders, ADS-B equipment, radar altimeters, and DME equipment, and ELTs.
          2. Whenever possible, make radio calls to the platform being approached or to the Flight Following Communications Center at least one mile out on approach. Ensure all communications are complete outside the 1,000 foot hazard distance. If no response is received, or if the platform is not radio equipped, further radio transmissions should not be made until visual contact with the deck indicates it is open for operation (no white “X”).
    7. Hydrogen Sulfide Gas Helideck/Heliport Operational Hazard Warning(s)/Procedures
      1. Background. Hydrogen sulfide (H2S) gas: Hydrogen sulfide gas in higher concentrations (300-500 ppm) can cause loss of consciousness within a few seconds and presents a hazard to pilots on/near offshore helidecks. When operating in offshore areas that have been identified to have concentrations of hydrogen sulfide gas, the following practices are recommended.
      2. Recommended Practices
        1. Pilots
          1. Ensure approved protective air packs are available for emergency use by the crew on the helicopter.
          2. If shutdown on a helideck, request the supervisor in charge provide a briefing on location of protective equipment and safety procedures.
          3. If while flying near a helideck and the visual red beacon alarm is observed or an unusually strong odor of “rotten eggs” is detected, immediately don the protective air pack, exit to an area upwind, and notify the suspected source field of the hazard.

            FIG 10-2-1
            Closed Helideck Marking - No Radio

            A graphic depicting the marking signifying a closed helideck. The words
        2. Oil Field Supervisors
          1. If presence of hydrogen sulfide is detected, a red rotating beacon or red high intensity strobe light adjacent to the primary helideck stairwell or wind indicator on the structure should be turned on to provide visual warning of hazard. If the beacon is to be located near the stairwell, the State of Louisiana “Offshore Heliport Design Guide” and FAA Advisory Circular (AC) 150/5390-2A, Heliport Design Guide, should be reviewed to ensure proper clearance on the helideck.
          2. Notify nearby helicopter operators and bases of the hazard and advise when hazard is cleared.
          3. Provide a safety briefing to include location of protective equipment to all arriving personnel.
          4. Wind socks or indicator should be clearly visible to provide upwind indication for the pilot.
    8. Gas Venting Helideck/Heliport Operational Hazard Warning(s)/Procedures - Operations Near Gas Vent Booms
      1. Background. Ignited flare booms can release a large volume of natural gas and create a hot fire and intense heat with little time for the pilot to react. Likewise, unignited gas vents can release reasonably large volumes of methane gas under certain conditions. Thus, operations conducted very near unignited gas vents require precautions to prevent inadvertent ingestion of combustible gases by the helicopter engine(s). The following practices are recommended.
      2. Pilots
        1. Gas will drift upwards and downwind of the vent. Plan the approach and takeoff to observe and avoid the area downwind of the vent, remaining as far away as practicable from the open end of the vent boom.
        2. Do not attempt to start or land on an offshore helideck when the deck is downwind of a gas vent unless properly trained personnel verify conditions are safe.
      3. Oil Field Supervisors
        1. During venting of large amounts of unignited raw gas, a red rotating beacon or red high intensity strobe light adjacent to the primary helideck stairwell or wind indicator should be turned on to provide visible warning of hazard. If the beacon is to be located near the stairwell, the State of Louisiana “Offshore Heliport Design Guide” and FAA AC 150/5390-2A, Heliport Design Guide, should be reviewed to ensure proper clearance from the helideck.
        2. Notify nearby helicopter operators and bases of the hazard for planned operations.
        3. Wind socks or indicator should be clearly visible to provide upward indication for the pilot.
    9. Helideck/Heliport Operational Warning(s)/Procedure(s) - Closed Helidecks or Heliports
      1. Background. A white “X” marked diagonally from corner to corner across a helideck or heliport touchdown area is the universally accepted visual indicator that the landing area is closed for safety of other reasons and that helicopter operations are not permitted. The following practices are recommended.
        1. Permanent Closing. If a helideck or heliport is to be permanently closed, X diagonals of the same size and location as indicated above should be used, but the markings should be painted on the landing area.


          White Decks: If a helideck is painted white, then international orange or yellow markings can be used for the temporary or permanent diagonals.

        2. Temporary Closing. A temporary marker can be used for hazards of an interim nature. This marker could be made from vinyl or other durable material in the shape of a diagonal “X.” The marker should be white with legs at least 20 feet long and 3 feet in width. This marker is designed to be quickly secured and removed from the deck using grommets and rope ties. The duration, time, location, and nature of these temporary closings should be provided to and coordinated with company aviation departments, nearby helicopter bases, and helicopter operators supporting the area. These markers MUST be removed when the hazard no longer exists. (See FIG 10-2-2.)

          FIG 10-2-2
          Closed Helideck Marking

          A graphic depicting a closed helideck marking: a diagonal
    10. Offshore (VFR) Operating Altitudes for Helicopters
      1. Background. Mid-air collisions constitute a significant percentage of total fatal offshore helicopter accidents. A method of reducing this risk is the use of coordinated VFR cruising altitudes. To enhance safety through standardized vertical separation of helicopters when flying in the offshore environment, it is recommended that helicopter operators flying in a particular area establish a cooperatively developed Standard Operating Procedure (SOP) for VFR operating altitudes. An example of such an SOP is contained in this example.
      2. Recommended Practice Example
        1. Field Operations. Without compromising minimum safe operating altitudes, helicopters working within an offshore field “constituting a cluster” should use altitudes not to exceed 500 feet.
        2. En Route Operations
          1. Helicopters operating below 750' AGL should avoid transitioning through offshore fields.
          2. Helicopters en route to and from offshore locations, below 3,000 feet, weather permitting, should use en route altitudes as outlined in TBL 10-2-1.

            TBL 10-2-1

            Magnetic Heading


            0° to 179°






            180° to 359°




        3. Area Agreements. See HSAC Area Agreement Maps for operating procedures for onshore high density traffic locations.


          Pilots of helicopters operating VFR above 3,000 feet above the surface should refer to the current Federal Aviation Regulations (14 CFR Part 91), and paragraph 3-1-4, Basic VFR Weather Minimums, of the AIM.

        4. Landing Lights. Aircraft landing lights should be on to enhance aircraft identification:
          1. During takeoff and landings;
          2. In congested helicopter or fixed wing traffic areas;
          3. During reduced visibility; or,
          4. Anytime safety could be enhanced.
    11. Offshore Helidecks/Landing Communications
      1. Background. To enhance safety, and provide appropriate time to prepare for helicopter operations, the following is recommended when anticipating a landing on an offshore helideck.
      2. Recommended Practices
        1. Before landing on an offshore helideck, pilots are encouraged to establish communications with the company owning or operating the helideck if frequencies exist for that purpose.
        2. When impracticable, or if frequencies do not exist, pilots or operations personnel should attempt to contact the company owning or operating the helideck by telephone. Contact should be made before the pilot departs home base/point of departure to advise of intentions and obtain landing permission if necessary.


          It is recommended that communications be established a minimum of 10 minutes prior to planned arrival time. This practice may be a requirement of some offshore owner/operators.


          1. See subparagraph 10-2-1d for Tanker Operations.
          2. Private use Heliport. Offshore heliports are privately owned/operated facilities and their use is limited to persons having prior authorization to utilize the facility.
    12. Two (2) Helicopter Operations on Offshore Helidecks
      1. Background. Standardized procedures can enhance the safety of operating a second helicopter on an offshore helideck, enabling pilots to determine/maintain minimum operational parameters. Orientation of the parked helicopter on the helideck, wind and other factors may prohibit multi-helicopter operations. More conservative Rotor Diameter (RD) clearances may be required under differing condition, i.e., temperature, wet deck, wind (velocity/direction/gusts), obstacles, approach/departure angles, etc. Operations are at the pilot's discretion.
      2. Recommended Practice. Helideck size, structural weight capability, and type of main rotor on the parked and operating helicopter will aid in determining accessibility by a second helicopter. Pilots should determine that multi-helicopter deck operations are permitted by the helideck owner/operator.
      3. Recommended Criteria
        1. Minimum one-third rotor diameter clearance (1/3 RD). The landing helicopter maintains a minimum 1/3 RD clearance between the tips of its turning rotor and the closest part of a parked and secured helicopter (rotors stopped and tied down).
        2. Three foot parking distance from deck edge (3'). Helicopters operating on an offshore helideck land or park the helicopter with a skid/wheel assembly no closer than 3 feet from helideck edge.
        3. Tiedowns. Main rotors on all helicopters that are shut down be properly secured (tied down) to prevent the rotor blades from turning.
        4. Medium (transport) and larger helicopters should not land on any offshore helideck where a light helicopter is parked unless the light helicopter is property secured to the helideck and has main rotor tied down.
        5. Helideck owners/operators should ensure that the helideck has a serviceable anti-skid surface.
      4. Weight and limitations markings on helideck. The helideck weight limitations should be displayed by markings visible to the pilot (see State of Louisiana “Offshore Heliport Design Guide” and FAA AC 150/5390-2A, Heliport Design Guide).


        Some offshore helideck owners/operators have restrictions on the number of helicopters allowed on a helideck. When helideck size permits, multiple (more than two) helicopter operations are permitted by some operators.

    13. Helicopter Rapid Refueling Procedures (HRR)
      1. Background. Helicopter Rapid Refueling (HRR), engine(s)/rotors operating, can be conducted safely when utilizing trained personnel and observing safe practices. This recommended practice provides minimum guidance for HRR as outlined in National Fire Protection Association (NFPA) and industry practices. For detailed guidance, please refer to National Fire Protection Association (NFPA) Document 407, “Standard for Aircraft Fuel Servicing,” 1990 edition, including 1993 HRR Amendment.


        Certain operators prohibit HRR, or “hot refueling,” or may have specific procedures for certain aircraft or refueling locations. See the General Operations Manual and/or Operations Specifications to determine the applicable procedures or limitations.

      2. Recommended Practices
        1. Only turbine-engine helicopters fueled with JET A or JET A-1 with fueling ports located below any engine exhausts may be fueled while an onboard engine(s) is (are) operating.
        2. Helicopter fueling while an onboard engine(s) is (are) operating should only be conducted under the following conditions:
          1. A properly certificated and current pilot is at the controls and a trained refueler attending the fuel nozzle during the entire fuel servicing process. The pilot monitors the fuel quantity and signals the refueler when quantity is reached.
          2. No electrical storms (thunderstorms) are present within 10 nautical miles. Lightning can travel great distances beyond the actual thunderstorm.
          3. Passengers disembark the helicopter and move to a safe location prior to HRR operations. When the pilot-in-command deems it necessary for passenger safety that they remain onboard, passengers should be briefed on the evacuation route to follow to clear the area.
          4. Passengers not board or disembark during HRR operations nor should cargo be loaded or unloaded.
          5. Only designated personnel, trained in HRR operations should conduct HRR written authorization to include safe handling of the fuel and equipment. (See your Company Operations/Safety Manual for detailed instructions.)
          6. All doors, windows, and access points allowing entry to the interior of the helicopter that are adjacent to or in the immediate vicinity of the fuel inlet ports kept closed during HRR operations.
          7. Pilots ensure that appropriate electrical/electronic equipment is placed in standby-off position, to preclude the possibility of electrical discharge or other fire hazard, such as [i.e., weather radar is on standby and no radio transmissions are made (keying of the microphone/transmitter)]. Remember, in addition to communications radios, radio transmissions are also emitted by aircraft radar, transponders, ADS-B equipment, radar altimeters, DME equipment, and ELTs.
          8. Smoking be prohibited in and around the helicopter during all HRR operations.
            The HRR procedures are critical and present associated hazards requiring attention to detail regarding quality control, weather conditions, static electricity, bonding, and spill/fires potential.
            Any activity associated with rotors turning (i.e.; refueling embarking/disembarking, loading/unloading baggage/freight; etc.) personnel should only approach the aircraft when authorized to do so. Approach should be made via safe approach path/walkway or “arc”- remain clear of all rotors.


            1. Marine vessels, barges etc.: Vessel motion presents additional potential hazards to helicopter operations (blade flex, aircraft movement).
            2. See National Fire Protection Association (NFPA) Document 407, “Standard for Aircraft Fuel Servicing” for specifics regarding non-HRR (routine refueling operations).
  2. Helicopter Night VFR Operations
    1. Effect of Lighting on Seeing Conditions in Night VFR Helicopter Operations


      This guidance was developed to support safe night VFR helicopter emergency medical services (HEMS) operations. The principles of lighting and seeing conditions are useful in any night VFR operation.

      While ceiling and visibility significantly affect safety in night VFR operations, lighting conditions also have a profound effect on safety. Even in conditions in which visibility and ceiling are determined to be visual meteorological conditions, the ability to discern unlighted or low contrast objects and terrain at night may be compromised. The ability to discern these objects and terrain is the seeing condition, and is related to the amount of natural and man made lighting available, and the contrast, reflectivity, and texture of surface terrain and obstruction features. In order to conduct operations safely, seeing conditions must be accounted for in the planning and execution of night VFR operations. Night VFR seeing conditions can be described by identifying “high lighting conditions” and “low lighting conditions.”
      1. High lighting conditions exist when one of two sets of conditions are present:
        1. The sky cover is less than broken (less than 5/8 cloud cover), the time is between the local Moon rise and Moon set, and the lunar disk is at least 50% illuminated; or
        2. The aircraft is operated over surface lighting which, at least, provides for the lighting of prominent obstacles, the identification of terrain features (shorelines, valleys, hills, mountains, slopes) and a horizontal reference by which the pilot may control the helicopter. For example, this surface lighting may be the result of:
          1. Extensive cultural lighting (man-made, such as a built-up area of a city),
          2. Significant reflected cultural lighting (such as the illumination caused by the reflection of a major metropolitan area's lighting reflecting off a cloud ceiling), or
          3. Limited cultural lighting combined with a high level of natural reflectivity of celestial illumination, such as that provided by a surface covered by snow or a desert surface.
      2. Low lighting conditions are those that do not meet the high lighting conditions requirements.
      3. Some areas may be considered a high lighting environment only in specific circumstances. For example, some surfaces, such as a forest with limited cultural lighting, normally have little reflectivity, requiring dependence on significant moonlight to achieve a high lighting condition. However, when that same forest is covered with snow, its reflectivity may support a high lighting condition based only on starlight. Similarly, a desolate area, with little cultural lighting, such as a desert, may have such inherent natural reflectivity that it may be considered a high lighting conditions area regardless of season, provided the cloud cover does not prevent starlight from being reflected from the surface. Other surfaces, such as areas of open water, may never have enough reflectivity or cultural lighting to ever be characterized as a high lighting area.
      4. Through the accumulation of night flying experience in a particular area, the operator will develop the ability to determine, prior to departure, which areas can be considered supporting high or low lighting conditions. Without that operational experience, low lighting considerations should be applied by operators for both pre-flight planning and operations until high lighting conditions are observed or determined to be regularly available.
    2. Astronomical Definitions and Background Information for Night Operations
      1. Definitions
        1. Horizon. Wherever one is located on or near the Earth's surface, the Earth is perceived as essentially flat and, therefore, as a plane. If there are no visual obstructions, the apparent intersection of the sky with the Earth's (plane) surface is the horizon, which appears as a circle centered at the observer. For rise/set computations, the observer's eye is considered to be on the surface of the Earth, so that the horizon is geometrically exactly 90 degrees from the local vertical direction.
        2. Rise, Set. During the course of a day the Earth rotates once on its axis causing the phenomena of rising and setting. All celestial bodies, the Sun, Moon, stars and planets, seem to appear in the sky at the horizon to the East of any particular place, then to cross the sky and again disappear at the horizon to the West. Because the Sun and Moon appear as circular disks and not as points of light, a definition of rise or set must be very specific, because not all of either body is seen to rise or set at once.
        3. Sunrise and sunset refer to the times when the upper edge of the disk of the Sun is on the horizon, considered unobstructed relative to the location of interest. Atmospheric conditions are assumed to be average, and the location is in a level region on the Earth's surface.
        4. Moonrise and moonset times are computed for exactly the same circumstances as for sunrise and sunset. However, moonrise and moonset may occur at any time during a 24 hour period and, consequently, it is often possible for the Moon to be seen during daylight, and to have moonless nights. It is also possible that a moonrise or moonset does not occur relative to a specific place on a given date.
        5. Transit. The transit time of a celestial body refers to the instant that its center crosses an imaginary line in the sky - the observer's meridian - running from north to south.
        6. Twilight. Before sunrise and again after sunset there are intervals of time, known as “twilight,” during which there is natural light provided by the upper atmosphere, which does receive direct sunlight and reflects part of it toward the Earth's surface.
        7. Civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished.
      2. Title 14 of the Code of Federal Regulations applies these concepts and definitions in addressing the definition of night (Section 1.1), the requirement for aircraft lighting (Section 91.209) and pilot recency of night experience (Section 61.67).
    3. Information on Moon Phases and Changes in the Percentage of the Moon Illuminated
      From any location on the Earth, the Moon appears to be a circular disk which, at any specific time, is illuminated to some degree by direct sunlight. During each lunar orbit (a lunar month), we see the Moon's appearance change from not visibly illuminated through partially illuminated to fully illuminated, then back through partially illuminated to not illuminated again. There are eight distinct, traditionally recognized stages, called phases. The phases designate both the degree to which the Moon is illuminated and the geometric appearance of the illuminated part. These phases of the Moon, in the sequence of their occurrence (starting from New Moon), are listed in FIG 10-2-3.

      FIG 10-2-3
      Phases of the Moon

      A graphic depicting the 8 stages of the moon: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent.
      1. The percent of the Moon's surface illuminated is a more refined, quantitative description of the Moon's appearance than is the phase. Considering the Moon as a circular disk, at New Moon the percent illuminated is 0; at First and Last Quarters it is 50%; and at Full Moon it is 100%. During the crescent phases the percent illuminated is between 0 and 50% and during gibbous phases it is between 50% and 100%.
      2. For practical purposes, phases of the Moon and the percent of the Moon illuminated are independent of the location on the Earth from where the Moon is observed. That is, all the phases occur at the same time regardless of the observer's position.
      3. For more detailed information, refer to the United States Naval Observatory site referenced below.
    4. Access to Astronomical Data for Determination of Moon Rise, Moon Set, and Percentage of Lunar Disk Illuminated
      1. Astronomical data for the determination of Moon rise and set and Moon phase may be obtained from the United States Naval Observatory using an interactive query available at:
      2. Click on “Data Services,” and then on “Complete Sun and Moon Data for One Day.”
      3. You can obtain the times of sunrise, sunset, moonrise, moonset, transits of the Sun and Moon, and the beginning and end of civil twilight, along with information on the Moon's phase by specifying the date and location in one of the two forms on this web page and clicking on the “Get data” button at the end of the form. Form “A” is used for cities or towns in the U.S. or its territories. Form “B” for all other locations. An example of the data available from this site is shown in TBL 10-2-2.
      4. Additionally, a yearly table may be constructed for a particular location by using the “Table of Sunrise/Sunset, Moonrise/Moonset, or Twilight Times for an Entire Year” selection.

        TBL 10-2-2
        Sample of Astronomical Data Available from the Naval Observatory

        The following information is provided for New Orleans, Orleans Parish, Louisiana
        (longitude W90.1, latitude N30.0)



        29 May 2007

        Central Daylight Time





        Begin civil twilight

        5:34 a.m.


        6:01 a.m.

        Sun transit

        12:58 p.m.


        7:55 p.m.

        End civil twilight

        8:22 p.m.






        5:10 p.m. on preceding day


        4:07 a.m.


        6:06 p.m.

        Moon transit

        11:26 p.m.


        4:41 a.m. on following day



        Phase of the Moon on 29 May: waxing gibbous with 95% of the Moon's visible disk illuminated.

        Full Moon on 31 May 2007 at 8:04 p.m. Central Daylight Time.

  3. Landing Zone Safety
    1. This information is provided for use by helicopter emergency medical services (HEMS) pilots, program managers, medical personnel, law enforcement, fire, and rescue personnel to further their understanding of the safety issues concerning Landing Zones (LZs). It is recommended that HEMS operators establish working relationships with the ground responder organizations they may come in contact with in their flight operations and share this information in order to establish a common frame of reference for LZ selection, operations, and safety.
    2. The information provided is largely based on the booklet, LZ - Preparing the Landing Zone, issued by National Emergency Medical Services Pilots Association (NEMSPA), and the guidance developed by the University of Tennessee Medical Center's LIFESTAR program, and is used with their permission. For additional information, go to
    3. Information concerning the estimation of wind velocity is based on the Beaufort Scale. See for more information.
    4. Selecting a Scene LZ
      1. If the situation requires the use of a helicopter, first check to see if there is an area large enough to land a helicopter safely.

        FIG 10-2-4
        Recommended Minimum Landing Zone Dimensions

        A graphic depicting the recommended minimum landing zone dimensions for small helicopters (60 ft. sides), medium helicopters (75 ft. sides), and large helicopters (120 ft. sides).
      2. For the purposes of FIG 10-2-4 the following are provided as examples of relative helicopter size:
        1. Small Helicopter: Bell 206/407, Eurocopter AS-350/355, BO-105, BK-117.
        2. Medium Helicopter: Bell UH-1 (Huey) and derivatives (Bell 212/412), Bell 222/230/430 Sikorsky S-76, Eurocopter SA-365.
        3. Large Helicopter: Boeing Chinook, Eurocopter Puma, Sikorsky H-60 series (Blackhawk), SK-92.
      3. The LZ should be level, firm and free of loose debris that could possibly blow up into the rotor system.
      4. The LZ should be clear of people, vehicles and obstructions such as trees, poles and wires. Remember that wires are difficult to see from the air. The LZ must also be free of stumps, brush, post and large rocks. See FIG 10-2-5.

        FIG 10-2-5
        Landing Zone Hazards

        A graphic depicting landing zone hazards such as people, vehicles, trees, poles and wires, and stumps and brush.
      5. Keep spectators back at least 200 feet. Keep emergency vehicles 100 feet away and have fire equipment (if available) standing by. Ground personnel should wear eye protection, if available, during landing and takeoff operations. To avoid loose objects being blown around in the LZ, hats should be removed; if helmets are worn, chin straps must be securely fastened.
      6. Fire fighters (if available) should wet down the LZ if it is extremely dusty.
    5. Helping the Flightcrew Locate the Scene
      1. If the LZ coordinator has access to a GPS unit, the exact latitude and longitude of the LZ should be relayed to the HEMS pilot. If unable to contact the pilot directly, relay the information to the HEMS ground communications specialist for relaying to the pilot, so that they may locate your scene more efficiently. Recognize that the aircraft may approach from a direction different than the direct path from the takeoff point to the scene, as the pilot may have to detour around terrain, obstructions or weather en route.
      2. Especially in daylight hours, mountainous and densely populated areas can make sighting a scene from the air difficult. Often, the LZ coordinator on the ground will be asked if she or he can see or hear the helicopter.
      3. Flightcrews use a clock reference method for directing one another's attention to a certain direction from the aircraft. The nose of the aircraft is always 12 o'clock, the right side is 3 o'clock, etc. When the LZ coordinator sees the aircraft, he/she should use this method to assist the flightcrew by indicating the scene's clock reference position from the nose of the aircraft. For example, “Accident scene is located at your 2 o'clock position.” See FIG 10-2-6.

        FIG 10-2-6
        “Clock” System for Identifying Positions Relative to the Nose of the Aircraft

        A graphic depicting the
      4. When the helicopter approaches the scene, it will normally orbit at least one time as the flight crew observes the wind direction and obstacles that could interfere with the landing. This is often referred to as the “high reconnaissance” maneuver.
    6. Wind Direction and Touchdown Area
      1. Determine from which direction the wind is blowing. Helicopters normally land and takeoff into the wind.
      2. If contact can be established with the pilot, either directly or indirectly through the HEMS ground communications specialist, describe the wind in terms of the direction the wind is from and the speed.
      3. Common natural sources of wind direction information are smoke, dust, vegetation movement, water streaks and waves. Flags, pennants, streamers can also be used. When describing the direction, use the compass direction from which the wind is blowing (example: from the North-West).
      4. Wind speed can be measured by small hand-held measurement devices, or an observer's estimate can be used to provide velocity information. The wind value should be reported in knots (nautical miles per hour). If unable to numerically measure wind speed, use TBL 10-2-3 to estimate velocity. Also, report if the wind conditions are gusty, or if the wind direction or velocity is variable or has changed recently.
      5. If any obstacle(s) exist, ensure their description, position and approximate height are communicated to the pilot on the initial radio call.

        TBL 10-2-3
        Table of Common References for Estimating Wind Velocity

        Wind (Knots)

        Wind Classification

        Appearance of Wind Effects

        On the Water

        On Land

        Less than 1


        Sea surface smooth and mirror-like

        Calm, smoke rises vertically


        Light Air

        Scaly ripples, no foam crests

        Smoke drift indicates wind direction, wind vanes are still


        Light Breeze

        Small wavelets, crests glassy, no breaking

        Wind felt on face, leaves rustle, vanes begin to move


        Gentle Breeze

        Large wavelets, crests begin to break, scattered whitecaps

        Leaves and small twigs constantly moving, light flags extended


        Moderate Breeze

        Small waves 1-4 ft. becoming longer, numerous whitecaps

        Dust, leaves, and loose paper lifted, small tree branches move


        Fresh Breeze

        Moderate waves 4-8 ft. taking longer form, many whitecaps, some spray

        Small trees in leaf begin to sway


        Strong Breeze

        Larger waves 8-13 ft., whitecaps common, more spray

        Larger tree branches moving, whistling in wires


        Near Gale

        Sea heaps up, waves 13-20 ft., white foam streaks off breakers

        Whole trees moving, resistance felt walking against wind



        Moderately high (13-20 ft.) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks

        Whole trees in motion, resistance felt walking against wind


        Strong Gale

        High waves (20 ft.), sea begins to roll, dense streaks of foam, spray may reduce visibility

        Slight structural damage occurs, slate blows off roofs



        Very high waves (20-30 ft.) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility

        Seldom experienced on land, trees broken or uprooted, “considerable structural damage”


        Violent Storm

        Exceptionally high (30-45 ft.) waves, foam patches cover sea, visibility more reduced




        Air filled with foam, waves over 45 ft., sea completely white with driving spray, visibility greatly reduced



        Wind from the South-East, estimated speed 15 knots. Wind shifted from North-East about fifteen minutes ago, and is gusty.

    7. Night LZs
      1. There are several ways to light a night LZ:
        1. Mark the touchdown area with five lights or road flares, one in each corner and one indicating the direction of the wind. See FIG 10-2-7.

          FIG 10-2-7
          Recommended Lighting for Landing Zone Operations at Night

          A graphic depicting the recommended lighting for landing zone operations at night marking the touchdown area with five lights or road flares; one in each corner and one indicating the direction of the wind.


          Road flares are an intense source of ignition and may be unsuitable or dangerous in certain conditions. In any case, they must be closely managed and firefighting equipment should be present when used. Other light sources are preferred, if available.

        2. If chemical light sticks may be used, care should be taken to assure they are adequately secured against being dislodged by the helicopter's rotor wash.
        3. Another method of marking a LZ uses four emergency vehicles with their low beam headlights aimed toward the intended landing area.
        4. A third method for marking a LZ uses two vehicles. Have the vehicles direct their headlight beams into the wind, crossing at the center of the LZ. (If fire/rescue personnel are available, the reflective stripes on their bunker gear will assist the pilot greatly.)
      2. At night, spotlights, flood lights and hand lights used to define the LZ are not to be pointed at the helicopter. However, they are helpful when pointed toward utility poles, trees or other hazards to the landing aircraft. White lights such as spotlights, flashbulbs and hi-beam headlights ruin the pilot's night vision and temporarily blind him. Red lights, however, are very helpful in finding accident locations and do not affect the pilot's night vision as significantly.
      3. As in Day LZ operations, ensure radio contact is accomplished between ground and air, if possible.
    8. Ground Guide
      1. When the helicopter is in sight, one person should assist the LZ Coordinator by guiding the helicopter into a safe landing area. In selecting an LZ Coordinator, recognize that medical personnel usually are very busy with the patient at this time. It is recommended that the LZ Coordinator be someone other than a medical responder, if possible. Eye protection should be worn. The ground guide should stand with his/her back to the wind and his/her arms raised over his/her head (flashlights in each hand for night operations.)
      2. The pilot will confirm the LZ sighting by radio. If possible, once the pilot has identified the LZ, the ground guide should move out of the LZ.
      3. As the helicopter turns into the wind and begins a descent, the LZ coordinator should provide assistance by means of radio contact, or utilize the “unsafe signal” to wave off the helicopter if the LZ is not safe (see FIG 10-2-8). The LZ Coordinator should be far enough from the touchdown area that he/she can still maintain visual contact with the pilot.
    9. Assisting the Crew
      1. After the helicopter has landed, do not approach the helicopter. The crew will approach you.
      2. Be prepared to assist the crew by providing security for the helicopter. If asked to provide security, allow no one but the crew to approach the aircraft.
      3. Once the patient is prepared and ready to load, allow the crew to open the doors to the helicopter and guide the loading of the patient.
      4. When approaching or departing the helicopter, always be aware of the tail rotor and always follow the directions of the crew. Working around a running helicopter can be potentially dangerous. The environment is very noisy and, with exhaust gases and rotor wash, often windy. In scene operations, the surface may be uneven, soft, or slippery which can lead to tripping. Be very careful of your footing in this environment.
      5. The tail rotor poses a special threat to working around a running helicopter. The tail rotor turns many times faster than the main rotor, and is often invisible even at idle engine power. Avoid walking towards the tail of a helicopter beyond the end of the cabin, unless specifically directed by the crew.


        Helicopters typically have doors on the sides of the cabin, but many use aft mounted “clamshell” type doors for loading and unloading patients on litters or stretchers. When using these doors, it is important to avoid moving any further aft than necessary to operate the doors and load/unload the patient. Again, always comply with the crew's instructions.

    10. General Rules
      1. When working around helicopters, always approach and depart from the front, never from the rear. Approaching from the rear can increase your risk of being struck by the tail rotor, which, when at operating engine speed, is nearly invisible.
      2. To prevent injury or damage from the main rotor, never raise anything over your head.
      3. If the helicopter landed on a slope, approach and depart from the down slope side only.
      4. When the helicopter is loaded and ready for take off, keep the departure path free of vehicles and spectators. In an emergency, this area is needed to execute a landing.
    11. Hazardous Chemicals and Gases
      1. Responding to accidents involving hazardous materials requires special handling by fire/rescue units on the ground. Equally important are the preparations and considerations for helicopter operations in these areas.
      2. Hazardous materials of concern are those which are toxic, poisonous, flammable, explosive, irritating, or radioactive in nature. Helicopter ambulance crews normally don't carry protective suits or breathing apparatuses to protect them from hazardous materials.
      3. The helicopter ambulance crew must be told of hazardous materials on the scene in order to avoid the contamination of the crew. Patients/victims contaminated by hazardous materials may require special precautions in packaging before loading on the aircraft for the medical crew's protection, or may be transported by other means.
      4. Hazardous chemicals and gases may be fatal to the unprotected person if inhaled or absorbed through the skin.
      5. Upon initial radio contact, the helicopter crew must be made aware of any hazardous gases in the area. Never assume that the crew has already been informed. If the aircraft were to fly through the hazardous gases, the crew could be poisoned and/or the engines could develop mechanical problems.
      6. Poisonous or irritating gases may cling to a victim's clothing and go unnoticed until the patient is loaded and the doors of the helicopter are closed. To avoid possible compromise of the crew, all of these patients must be decontaminated prior to loading.
    12. Hand Signals
      1. If unable to make radio contact with the HEMS pilot, use the following signals:

        FIG 10-2-8
        Recommended Landing Zone Ground Signals

        A graphic depicting the recommended landing zone ground signals to use when unable to make radio contact with the HEMS pilot.
    13. Emergency Situations
      1. In the event of a helicopter accident in the vicinity of the LZ, consider the following:
        1. Emergency Exits:
          1. Doors and emergency exits are typically prominently marked. If possible, operators should familiarize ground responders with the door system on their helicopter in preparation for an emergency event.
          2. In the event of an accident during the LZ operation, be cautious of hazards such as sharp and jagged metal, plastic windows, glass, any rotating components, such as the rotors, and fire sources, such as the fuel tank(s) and the engine.
        2. Fire Suppression:
          Helicopters used in HEMS operations are usually powered by turboshaft engines, which use jet fuel. Civil HEMS aircraft typically carry between 50 and 250 gallons of fuel, depending upon the size of the helicopter, and planned flight duration, and the fuel remaining after flying to the scene. Use water to control heat and use foam over fuel to keep vapors from ignition sources.
  4. Emergency Medical Service (EMS) Multiple Helicopter Operations
    1. Background. EMS helicopter operators often overlap other EMS operator areas. Standardized procedures can enhance the safety of operating multiple helicopters to landing zones (LZs) and to hospital heliports. Communication is the key to successful operations and in maintaining organization between helicopters, ground units and communication centers. EMS helicopter operators which operate in the same areas should establish joint operating procedures and provide them to related agencies.
    2. Recommended Procedures.
      1. Landing Zone Operations. The first helicopter to arrive on-scene should establish communications with the ground unit at least 10 NMs from the LZ to receive a LZ briefing and to provide ground control the number of helicopters that can be expected. An attempt should be made to contact other helicopters on 123.025 to pass on to them pertinent LZ information and the ground unit's frequency. Subsequent helicopters arriving on scene should establish communications on 123.025 at least 10 NMs from the LZ. After establishing contact on 123.025, they should contact the ground unit for additional information. All helicopters should monitor 123.025 at all times.
        1. If the landing zone is not established by the ground unit when the first helicopter arrives, then the first helicopter should establish altitude and orbit location requirements for the other arriving helicopters. Recommended altitude separation between helicopters is 500 feet (weather and airspace permitting). Helicopters can orbit on cardinal headings from the scene coordinates. (See FIG 10-2-9.)
        2. Upon landing in the LZ, the first helicopter should update the other helicopters on the LZ conditions, i.e., space, hazards and terrain.
        3. Before initiating any helicopter movement to leave the LZ, all operators should attempt to contact other helicopters on 123.025, and state their position and route of flight intentions for departing the LZ.
      2. Hospital Operations. Because many hospitals require landing permission and have established procedures (frequencies to monitor, primary and secondary routes for approaches and departures, and orbiting areas if the heliport is occupied) pilots should always receive a briefing from the appropriate facility (communication center, flight following, etc.) before proceeding to the hospital.
        1. In the event of multiple helicopters coming into the hospital heliport, the helicopter nearest to the heliport should contact other inbound helicopters on 123.025 and establish intentions. Follow the guidelines established in the LZ operations.
        2. To facilitate approach times, the pilot-in-command of the helicopter occupying the hospital heliport should advise any other operators whether the patient will be off loaded with the rotor blades turning or stopped, and the approximate time to do so.
        3. Before making any helicopter movement to leave the hospital heliport, all operators should attempt to contact other helicopters on 123.025 and state their position and route of flight intentions for departing the heliport.

          FIG 10-2-9
          EMS Multiple Helicopter LZ/Heliport Operation

          A graphic depicting EMS multiple helicopter LZ/heliport operation.


          If the LZ/hospital heliport weather conditions or airspace altitude restrictions prohibit the recommended vertical separation, 1 NM separations should be kept between helicopter orbit areas.