For the purposes of this chapter, the following definitions are applicable:

   AIRPORT: The Helena airport.

   AIRPORT BOARD OF ADJUSTMENT: The board consisting of five (5) members appointed by the Helena city commission and Lewis and Clark County commissioners as provided in section 1-718 and 11-2707, Revised Codes of Montana, 1947.

   AIRPORT ELEVATION: The established elevation of the highest point on the usable landing area.

   AIRPORT HAZARD: Any structure, tree or use of land which obstructs the air space required for, or is otherwise hazardous to, the flight of aircraft in landing or taking off at the airport.

   AIRPORT REFERENCE POINT: The point established as the approximate geographic center of the airport landing area and so designated.

   HEIGHT: For the purpose of determining the height limitations in all zones established by this chapter and shown on the Helena airport zoning map, the datum shall be mean sea level elevation unless otherwise specified.

   LANDING AREA: The area of the airport used for the landing, taking off, or taxiing of aircraft.

   NONCONFORMING USE: Any preexisting structure, tree, natural growth or use of land which is inconsistent with the provisions of this chapter or amendment thereto.

   NONPRECISION INSTRUMENT RUNWAY: A runway having or planned an instrument approach procedure utilizing area type navigation equipment for a straight in, nonprecision instrument approach.

   PRECISION INSTRUMENT RUNWAY: A runway equipped or to be equipped with a precision electronic navigation aid or landing aid or other air navigation facilities, suitable to permit the landing of aircraft by an instrument approach under restricted visibility conditions.

   RUNWAY: The paved surface of an airport landing strip.

   STRUCTURE: An object or structure constructed or installed by man, including, but not limited to, buildings, towers, smoke stacks, and overhead transmission lines.

   TREE: Any vegetation or other naturally growing object.

   UTILITY RUNWAY: A runway that is constructed for and intended to be used by propeller driven aircraft of twelve thousand five hundred (12,500) pounds maximum gross weight or less. (Ord. 2359, 5-20-1985)

There are hereby created and established certain zones which include all of the land lying within the precision instrument approach zones, utility approach zones, transition zones, horizontal zone and conical zone. Such areas and zones are shown on Helena airport zoning map consisting of one sheet prepared by the joint city-county airport board, a copy of which is made a part hereof by reference. The various zones are defined and described as follows:

   A.   Precision Instrument Approach Zone: A precision instrument approach zone is established at each end of the precision instrument runway for precision instrument landings and takeoffs. Each precision instrument approach zone shall have a width of one thousand feet (1,000') at a distance of two hundred feet (200') beyond each end of the runway, widening thereafter uniformly to a width of sixteen thousand feet (16,000') at a distance of fifty thousand two hundred feet (50,200') beyond each end of the runway, with its centerline being the continuation of the centerline of the runway.

   B.   Utility Approach Zone: A utility approach zone is established at each end of all utility runways for visual landings and takeoffs. Each utility approach zone shall have a width of two hundred fifty feet (250') at a distance of two hundred feet (200') beyond each end of the runway, widening thereafter uniformly to a width of one thousand two hundred fifty feet (1,250') at a distance of five thousand two hundred feet (5,200') beyond each end of the runway with its centerline being the continuation of the centerline of the runway.

   C.   Transition Zones: Transition zones are hereby established adjacent to each precision instrument and utility runway and approach zones as indicated on the zoning map. Transition zones symmetrically located on either side of runways have variable widths as shown on the zoning map. Transition zones extend outward from a line one hundred twenty five feet (125') on either side of the centerline of the utility runway, for the length of such runway plus two hundred feet (200') on each end, and five hundred feet (500') on either side of the centerline of the precision instrument runway, for the length of such runway plus two hundred feet (200') on each end, and are parallel and level with such runway centerlines. The transition zones along such runways slope upward and outward one foot (1') vertically for each seven feet (7') horizontally to the point where they intersect the surface of the horizontal zone. Further, transition zones are established adjacent to both precision instrument and utility approach zones for the entire length of the approach zones. These transition zones have variable widths, as shown on the zoning map. Such transition zones flare symmetrically with either side of the runway approach zones from the base of such zones and slope upward and outward at the rate of one foot (1') vertically for each seven feet (7') horizontally to the points where they intersect the surfaces of the horizontal and conical zones. Additionally, transition zones are established adjacent to the precision instrument approach zone where it projects through and beyond the limits of the conical zone, extending a distance of five thousand feet (5,000') measured horizontally from the edge of the precision instrument approach zones at right angles to the continuation of the centerline of the runway.

   D.   Horizontal Zone: A horizontal zone is hereby established as the area within a perimeter established by swinging arcs of ten thousand feet (10,000') radius from a point two hundred feet (200') beyond the planned ends of the precision instrument runway on the continuation of the runway centerline and connecting the adjacent arcs by lines tangent to those arcs. The horizontal zone does not include the precision instrument and utility approach zones and the transition zones.

   E.   Conical Zone: A conical zone is hereby established as the area that commences at the periphery of the horizontal zone and extends outward there from a distance of four thousand feet (4,000'). The conical zone does not include the precision instrument approach zones and transition zones. (Ord. 2359, 5-20-1985)

   A.   Except as otherwise provided in this chapter, no structure or tree shall be erected, altered, allowed to grow, or maintained in any zone created by this chapter to a height in excess of the height limitation established for such zone. Such height limitations are established for each of the zones as follows:

      1.   Precision Instrument Approach Zone: One foot (1') in height for each fifty feet (50') in horizontal distance beginning at a point two hundred feet (200') from and at the centerline elevation of the planned end of the precision instrument runway and extending to a distance of ten thousand two hundred feet (10,200') from the end of the runway; thence one foot (1') in height for each forty feet (40') in horizontal distance to a point fifty thousand two hundred feet (50,200') from the planned end of the runway.

      2.   Utility Approach Zones: One foot (1') in height for each twenty feet (20') in horizontal distance beginning at a point two hundred feet (200') from and at the centerline elevation of the planned end of the utility runway and extending to a point five thousand two hundred feet (5,200') from the planned end of the runway.

      3.   Transition Zones: One foot (1') in height for each seven feet (7') in horizontal distance beginning at any point one hundred twenty five feet (125') normal to and at the elevation of the centerline of utility runways, extending two hundred feet (200') beyond each end thereof, and five hundred feet (500') normal to and at the elevation of the centerline of the precision instrument runway, extending two hundred feet (200') beyond each end thereof, extending to a height of one hundred fifty feet (150') above the airport elevation which is three thousand eight hundred seventy three feet (3,873') above mean sea level. In addition to the foregoing there are established height limits of one foot (1') vertical height for each seven feet (7') horizontal distance measured from the edges of all approach zones for the entire length of the approach zones and extending upward and outward to the points where they intersect the horizontal or conical surfaces. Further where the precision instrument approach zone projects through and beyond the conical zone, a height limit of one foot (1') for each seven feet (7') of horizontal distance shall be maintained beginning at the edge of the instrument approach zone measured normal to the centerline of the runway extended.

      4.   Horizontal Zone: One hundred fifty feet (150') above the airport elevation or a height of four thousand twenty three feet (4,023') above mean sea level.

      5.   Conical Zone: One foot (1') in height for each twenty feet (20') of horizontal distance beginning at the periphery of the horizontal zone, extending to a height of three hundred fifty feet (350') above the airport elevation.

   B.   Nothing in this chapter shall be construed as prohibiting the growth, construction or maintenance of any tree or structure to a height up to fifty feet (50') above the surface of the land. (Ord. 2359, 5-20-1985)

Notwithstanding any other provision of this chapter, no use may be made of land within any zone established by this chapter in such manner as to create electrical interference with radio communication between the airport and aircraft, make it difficult for operators or aircraft to distinguish between airport lights and others, result in glare in the eyes of operators of aircraft using the airport, impair visibility in the vicinity of the airport or otherwise endanger the landing, taking off, maneuvering, or operating of aircraft. (Ord. 2359, 5-20-1985)

   A.   The regulations prescribed by this chapter shall not be construed to require the removal, lowering, or other change or alteration of any structure or tree not conforming to the regulations as of February 5, 1973, or otherwise interfere with the continuance of any use which was nonconforming as of such date. Nothing herein contained shall require any change in the construction or alteration of which was begun prior to February 5, 1973, and was diligently prosecuted, except as hereinafter provided in regard to hazard marking and lighting.

   B.   Notwithstanding the preceding provision of this section, the owner of any nonconforming structure or tree shall permit the installation, operation, and maintenance thereon of such markers and lights as shall be deemed necessary by the joint city-county airport board to indicate, to the operators of aircraft in the vicinity of the airport, the presence of such airport hazards. Such markers and lights shall be installed, operated and maintained at the expense of the joint city- county airport board.

   C.   Whenever a nonconforming structure or tree has been abandoned, or has been torn down, physically deteriorated, decayed, damaged or otherwise destroyed, to an extent of more than fifty percent (50%) of its replacement cost at the time of such occurrence, such structure or tree shall not be reconstructed, repaired or replaced in a manner exceeding any applicable height limitation or otherwise deviating from the provisions of this chapter, and no permit allowing the same shall be issued hereunder without the prior granting of a variance. (Ord. 2359, 5-20-1985)

   A.   Except as otherwise specifically provided in this section, no material change shall be made in the use of land and no structure or tree shall be erected, altered, planted or otherwise established in any zone created under, by or pursuant to this chapter unless a permit therefor has been first applied for and granted. Each application for a permit shall indicate the purpose for which the permit is desired, with sufficient particularity to permit a determination of whether the resulting use, structure or tree will conform to the requirements of this chapter. If such determination is in the affirmative, the permit shall be granted.

   B.   In the area lying within the limits of the horizontal zone and the conical zone, no permit shall be required for any tree or structure less than seventy five feet (75') high, except when, because of terrain, land contour or topographic features, such tree or structure would extend above the height limitation prescribed for such zone.

   C.   In the areas lying within the limits of the precision instrument and utility approach zones but at a horizontal distance of not less than four thousand two hundred feet (4,200') from each end of the runways, no permit shall be required for any tree or structure less than seventy five feet (75') high, except when such tree or structure would extend above the height limitations prescribed for such instrument or noninstrument approach zone.

   D.   In the areas lying within the limits of the transition zones beyond the perimeter of the horizontal zone, no permit shall be required for any tree or structure less than seventy five feet (75') high, except when, because of terrain, land contour or topographic features, such tree or structure would extend above the height limitations prescribed for such transition zones.

   E.   Nothing contained in any of the foregoing provisions shall be construed as permitting any construction, alteration or growth of any structure or tree in excess of any of the height limitations established by section 11-35-3 of this chapter, subject to the exception contained therein.

   F.   No permit shall be granted that would allow the establishment or creation of an airport hazard or permit a nonconforming use, structure, or tree to be made or become higher, or become a greater hazard to air navigation, than it was on February 5, 1973, or than it is when the application for a permit is made. No permit shall be granted that would allow the establishment or creation of any use or structure which does not comply with Montana state air pollution standards. Except as indicated, all applications for such a permit shall be granted. (Ord. 2359, 5-20-1985)

Any person desiring to erect or increase the height of any structure, or to permit the growth of any tree, or to use his property, in a manner not in accordance with the provisions of this chapter, may apply to the airport board of adjustment for a variance from such provisions. Such a variance shall be granted where it is duly found that a literal application or enforcement of the regulations would result in practical difficulty or unnecessary hardship and that the relief granted would not be contrary to the public interest but will do substantial justice and be in accordance with the spirit of this chapter. (Ord. 2359, 5-20-1985)

If such action is deemed advisable to effectuate the purpose of this chapter and be reasonable in the circumstances, any permit or variance granted may be so conditioned as to require the owner of the structure or tree in question to install, operate, and maintain thereon such markers and lights as may be necessary to indicate to operators of aircraft the presence of an airport hazard. (Ord. 2359, 5-20-1985)

The director of building and safety is hereby designated and charged with the duty of administering and enforcing the provisions of this chapter. The duties of the director of building and safety shall include that of hearing and deciding all permits under the applicable section, but the director of building and safety shall not have or exercise any of the powers or duties delegated to the airport board of adjustment. (Ord. 2359, 5-20-1985)

   A.   There is hereby created, under sections 67-6-206 and 76-2-321 through 76-2-328, Montana Code Annotated, an airport board of adjustment which shall possess and exercise the following powers:

      1.   To hear and decide appeals from any order, requirement, decision, or determination made by the joint city-county airport board in the enforcement of this chapter.

      2.   To hear and decide special exceptions to the provisions of this chapter upon which said airport board of adjustment under such provisions may be required to pass.

      3.   To hear and decide specific variances.

   B.   The airport board of adjustment shall consist of five (5) members, three (3) members appointed by the Lewis and Clark County commission and two (2) members appointed by the Helena city commission. Each member shall serve for a term of three (3) years and until a successor is duly appointed and qualified. Members may only be removed by the appointing authority for cause upon written charges after a public hearing. No member of the airport board of adjustment shall be a member of the joint city-county airport board.

   C.   The airport board of adjustment shall adopt rules for its governance and procedure consistent with the provisions of this chapter. Meetings of the airport board of adjustment shall be held at the call of the chairperson and at such other times as the airport board of adjustment may determine. The chairperson may administer oaths and compel the attendance of witnesses. All members of the airport board of adjustment shall be present at variance hearings. All hearings of the airport board of adjustment shall be public. The airport board of adjustment shall keep minutes of its proceedings showing the vote of each member upon each question and shall keep records of its examinations and other official actions, all of which shall immediately be filed in the office of the board and shall be a public record.

   D.   The airport board of adjustment shall make written findings of fact and conclusions of law, giving the facts upon which it acted and its legal conclusions from such facts, in reversing, affirming, or modifying any order, requirement, decision or determination which comes before it under the provisions of this chapter.

   E.   The concurring vote of four (4) members of the airport board of adjustment shall be necessary to reverse any order, requirement, decision or determination of the joint city- county airport board, or to decide in favor of the applicant on any matter upon which it is required to pass under this chapter, or to grant any variance from the provisions or requirements of this chapter. (Ord. 2359, 5-20-1985)

   A.   Any person aggrieved, or any taxpayer affected, by any decision of the joint city-county airport board made in the administration of this chapter, may appeal to the airport board of adjustment.

   B.   All appeals hereunder must be taken within a reasonable time, as provided by the rules of the airport board of adjustment, by filing with said board a notice of appeal specifying the grounds thereof. The airport board of adjustment shall, within a reasonable time, hear said appeal. The board shall give public notice of each such hearing, provide due notice to the parties in interest, and decide the same within a reasonable time. Upon the hearing, any party may appear personally or by agent or attorney.

   C.   The airport board of adjustment may modify, reverse or affirm, in whole or in part, the order, requirement, decision or determination appealed from and may make such order, requirement decision, or determination as may be appropriate under the circumstances. (Ord. 2359, 5-20-1985)

Any person aggrieved, or any taxpayer affected, by any decision of the airport board of adjustment, may appeal to the district court as provided in section 67-6-206 and 76-2-327, Montana Code Annotated. (Ord. 2359, 5-20-1985)

Where an area or location is subject to more than one height limitation under this chapter, or where there exists a conflict between any of the regulations or limitations prescribed by this chapter any other regulations applicable to the same area, whether the conflict be with respect to the height of structures or trees, the use of land, or any other matter, the more stringent or restrictive limitation or requirement shall govern. (Ord. 2359, 5-20-1985)