WIRE STRIKE

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WIRE STRIKE PREVENTION
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INTRODUCTION

• Types of hazards
• Wire design
• WSPS and ability to cut
• Army guidance
• Important avoidance factors
• Wire hazard recons
• Night limitations
• Safety center accidents
• Summary

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PURPOSE

• Discuss methods and procedures to be followed
  while conducting operations in the terrain flight
  envelope, to include mission planning, briefing,
  in-flight operations and post mission
  responsibilities

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OBJECTIVES

• Understand capabilities of WSPS
• Understand individual responsibilities to prevent
  wire strikes
• Know procedures for pre-mission planning
  briefings, in-flight coordination and post
  mission actions to prevent wire strikes

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OBJECTIVES

• Increase aircrew awareness of the potential for
  mishaps if proper procedures are not followed

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TYPES OF HAZARDS

• Physical
• Natural
• Birds, trees, etc.
• Manmade
• Towers, wires, buildings
• Weather
• Haze, fog, precipitation, low sun
• Human
• Poor physical condition
• Limited PERPHERAL vision
• Fatigue
• Attitude

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TYPES OF WIRES

• Tow missile wires
• Guy wires
• Fence lines
• COMMO wires strung through trees
• Power lines

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Wire System Design

• Voltage dictates the size of the wire.
• Size varies from 1/4 inch to over 2 inches.
• Large wires can carry 138,000 volts.
• Most common size is about 1 inch.
• Tensile strength is 18,000 lbs.

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Wire System DesignedTo Withstand

• Ice wind - designed to allow the wire to
  stretch due to ice, wind, and temperature.
• Wires can stretch from a few inches to six feet
  or more.

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Guy Wires

• Run horizontally from pole to pole or
• diagonally from the pole to the ground.
• Usually 3/4 to 1 inch in diameter (about the size
  of a nickel).
• Tensile strength of over 50,000 lbs.

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Power Lines In Local Flying Area

• Aluminum cable
• Being replaced
• Copper cables
• Range in size from .25 inches to 1 inch
• Many of the cables being replaced are going
  underground

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WSPS

• The system consists of nine cutters/deflectors
  located on the fuselage and landing gear/support.
  
• They are
• Upper cutter on the rear of the sliding fairing
• Pitot cutter/deflector on the front of the
  sliding fairing
• Windshield post wiper deflectors
• Door hinge deflector
• Step extension
• Step deflector
• Landing gear joint deflector
• Main landing gear cutter/deflector
• Tail landing gear deflector.

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ARMY GUIDANCE
ATM
STANDARDS

• Locate and accurately estimate the height of
  wires.
• Determine the best method to negotiate the wire
  obstacles.
• Safely negotiate the wire obstacle, minimizing
  the time unmasked.
• Correctly perform crew coordination actions.

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ATM DESCRIPTION

• TASK 2083 Negotiate wire obstacles.
• DESCRIPTION
• 1. Crew actions.
• a. The P will remain focused primarily outside
  the aircraft.
• b. The P and NCM will announce adequate warning
  to avoid hazards, wires, and
• poles or supporting structures. They also will
  announce when the aircraft is clear and
• when their attention is focused inside the
  aircraft.
• 2. Procedures.
• a. Announce when wires are seen. Confirm the
  location of wire obstacles with other
• crew members.
• b. Discuss the characteristics of wires and
  accurately estimate the amount of available
• clearance between them and the ground to
  determine the method of crossing. Locate
• guy wires and supporting poles.
• c. Announce the method of negotiating the wires
  and when the maneuver is initiated.
• Before crossing the wires, identify the highest
  wire. Cross near a pole to aid in visual
• perception and minimize the time that the
  aircraft is unmasked. When underflying
• wires, maintain a minimum clearance of hover
  height plus 30 feet and ground speed
• no greater than that of a brisk walk. Ensure
  lateral clearance from guy wires and
• poles.

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ATM NIGHT AND NVD CONSIDERATIONS

• Crew should not perform task unless location is
  checked during daylight.
• Wires are difficult to detect with NVG.

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IMPORTANT FACTORS

• Be aware of your attitude toward terrain flight
• Physical conditioning and fatigue
• Check hazards map
• Brief other crewmember
• Use proper visual scanning techniques and
  interpret visual cues
• Birds roosting in midair
• Long linear openings in wooded area
• Poles
• Areas around buildings

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IMPORTANT FACTORS

• Know location of aircraft at all times.
• While in formation, stack up.
• Be aware of and recognize existing blind spots.
• When low, go slow.
• IPS, reinforce wire strike prevention.
• Crew coordination
• Dont take shortcuts or violate procedures.

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IMPORTANT FACTORS

• Supervision - chain of command must enforce that
  pilots adhere to established procedures.
• All aircraft in flight must know their position.
• Minimize contour flight.

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WIRE HAZARD RECONS

• Schedule recons without incorporating into
  another mission
• Flight Operations updates hazards maps

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• Airspeed and ground speed limitations
• Atmospheric conditions
• Object acquisition and identification
• Proficiency
• Humidity
• Obscurants

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• Associate wires with man-made features because
  they are difficult to see at night
• Long linear openings in a wooded area
• Poles
• Open areas near buildings
• NOE routes

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HISTORY OF WIRE STRIKES
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HISTORY OF WIRE STRIKES

• MEDEVAC aircraft responding to report of an
  urgent surgical patient did not have access to
  a hazard map of the area. Struck wires at
  approximately 50 to 55 feet. Aircraft was
  destroyed, and the three crewmembers were fatally
  injured.

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HISTORY OF WIRE STRIKES
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HISTORY OF WIRE STRIKES

• Continuation/RL Progression NVG training
  mission. Crew selected a different route than the
  one that had been reconned earlier in the day.
  Struck a cable at approximately 40 feet AGL and
  40 Kts. Main rotor blades contacted cable.
  Stabilator struck the riverbed, A/C settled into
  the river on its left side. Severe A/C damage,
  crew suffered minor injuries

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AH-64A 1 Mar 97 Night Ft. Hood, TX.

• During a night, unaided, multi-aircraft formation
  flight into obvious decreasing weather
  conditions, chalk 7 struck a set of high-tension
  wires twice at about 60 feet AGL. The first
  strike occurred going west as the pilot on the
  controls initiated a descent to a selected,
  immediate landing

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area to ensure safe separation from chalk 6. The
second wire strike occurred after the PC took
over the flight controls with the intent to land
the windscreen damaged aircraft. The second wire
strike occurred with the aircraft going generally
east, approximately 3/4 mile south of the initial
wire strike area. The tail rotor separated from
the airframe in the second wire strike and the
aircraft crashed out of control. The aircraft
sustained major damage and the two pilots
received minor injuries.
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AH-64D 2 Oct 99 Night Bowie, TX.

• While conducting NOE training mission, aircraft
  struck approximately 50 telephone wire. PC felt
  a tug on the aircraft and landed aircraft
  suspecting wire strike. Maintenance inspection
  revealed no damage.

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RE-CREATION OF WIRE STRIKE
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AH-64A 4 Dec 99 Night Bondsteel, Serbia

• During contour flight in mountainous terrain,
  Apache contacted triple strand power lines
  (approximately 3/4 inch aluminum wire) The
  aircrafts WSPS severed two strands of wire and
  the aircraft missed.

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RIGHT MOST POLE ON FINAL APPROACH PATH
AIRCRAFT LOCATION AFTER WIRE-STRIKE
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WIRES RUNNING LEFT TO RIGHT AT APPROXIMATELY 100
FT HIGH
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WIRE THAT WAS CUT
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WSPS THAT CUT WIRE
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AIRCRAFT
WIRE THAT WAS STRUCK (ALREADY REPLACED)
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LEFT MOST POLE ON APPROACH
AIRCRAFT
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RIGHT MOST POLE ON APPROACH
AIRCRAFT
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Final Thought

• No one is immune to accidents. Experience, rank
  and age DO NOT create an error free aviator.
  Only diligence and compliance with established
  procedures in mission planning and execution will
  reduce or eliminate wire strike mishaps.

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Summary

• Types of hazards
• Wire design
• WSPS and ability to cut
• Army guidance
• Important avoidance factors
• Wire hazard recons
• Night limitations
• Safety center accidents