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Instrument Procedures

Emergency Procedures (Part Three)

Filed Under: Emergency Procedures

Maintaining Aircraft Control

Once the crewmembers recognize the situation, they commit to controlling the aircraft by using and trusting flight instruments. Attempting to search outside the flight deck for visual confirmation can result in spatial disorientation and complete loss of control. The crew must rely on instruments and depend on crew coordination to facilitate that transition. The pilot or flight crew must abandon their efforts to establish visual references and fly the aircraft by their flight instruments.

The most important concern, along with maintaining aircraft control, is to initiate a climb immediately. An immediate climb provides a greater separation from natural and manmade obstacles, as well as improve radar reception of the aircraft by ATC. An immediate climb should be appropriate for the current conditions, environment, and known or perceived obstacles. Listed below are procedures that can assist in maintaining aircraft control after encountering IIMC with the most critical action being to immediately announce IIMC and begin a substantial climb while procedures are being performed. These procedures are performed nearly simultaneously:

  • Attitude—level wings on the attitude indicator.
  • Heading—maintain heading; turn only to avoid known obstacles.
  • Power—adjust power as necessary for desired climb rate.
  • Airspeed—adjust airspeed as necessary. Complete the IIMC recovery according to local and published regulations and policies.

In situations where the pilot encounters IIMC while conducting an instrument maneuver, the best remedy is immediate execution of the published missed approach.

The pilot must trust the flight instruments concerning the aircraft’s attitude regardless of intuition or visual interpretation. The vestibular sense (motion sensing by the inner ear) can confuse the pilot. Because of inertia, sensory areas of the inner ear cannot detect slight changes in aircraft attitude nor can they accurately sense attitude changes that occur at a uniform rate over time. Conversely, false sensations often push the pilot to believe that the attitude of the aircraft has changed when in fact it has not, resulting in spatial disorientation.

ATC Requirements During an In-Flight Emergency

ATC personnel can help pilots during in-flight emergency situations. Pilots should understand the services provided by ATC and the resources and options available. These services enable pilots to focus on aircraft control and help them make better decisions in a time of stress.

 

Provide Information

During emergency situations, pilots should provide as much information as possible to ATC. ATC uses the information to determine what kind of assistance it can provide with available assets and capabilities. Information requirements vary depending on the existing situation. ATC requires at a minimum, the following information for in-flight emergencies:

  • Aircraft identification and type
  • Nature of the emergency
  • Pilot’s desires

If time and the situation permits, the pilot should provide ATC with more information. Listed below is additional information that would help ATC in further assisting the pilot during an emergency situation.

  • Aircraft altitude
  • Point of departure and destination
  • Airspeed
  • Fuel remaining in time
  • Heading since last known position
  • Visible landmarks
  • Navigational aids (NAVAID) signals received
  • Time and place of last known position
  • Aircraft color
  • Pilot reported weather
  • Emergency equipment on board
  • Number of people on board
  • Pilot capability for IFR flight
  • Navigation equipment capability

When the pilot requests, or when deemed necessary, ATC can enlist services of available radar facilities and DF facilities operated by the FAA. ATC can also coordinate with other agencies, such as the U.S. Coast Guard (USCG) and other local authorities and request their emergency services.

Radar Assistance

Radar is an invaluable asset that can be used by pilots during emergencies. With radar, ATC can provide navigation assistance to aircraft and provide last-known location during catastrophic emergencies. If a VFR aircraft encounters or is about to encounter IMC weather conditions, the pilot can request radar vectors to VFR airports or VFR conditions. If the pilot determines that he or she is qualified and the aircraft is capable of conducting IFR flight, the pilot should file an IFR flight plan and request a clearance from ATC to the destination airport as appropriate. If the aircraft has already encountered IFR conditions, ATC can inform the pilot of appropriate terrain/obstacle clearance minimum altitude. If the aircraft is below appropriate terrain/obstacle clearance minimum altitude and sufficiently accurate position information has been received or radar identification is established, ATC can furnish a heading or radial on which to climb to reach appropriate terrain/ obstacle clearance minimum altitude.

Emergency Airports

ATC personnel consider how much remaining fuel in relation to the distance to the airport and weather conditions when recommending an emergency airport to aircraft requiring assistance. Depending on the nature of the emergency, certain weather phenomena may deserve weighted consideration. A pilot may elect to fly further to land at an airport with VFR conditions instead of closer airfield with IFR conditions. Other considerations are airport conditions, NAVAID status, aircraft type, pilot’s qualifications, and vectoring or homing capability to the emergency airport. In addition, ATC and pilots should determine which guidance can be used to fly to the emergency airport. The following options may be available:

  • Radar
  • DF
  • Following another aircraft
  • NAVAIDs
  • Pilotage by landmarks
  • Compass headings
 

Emergency Obstruction Video Map (EOVM)

The emergency obstruction video map (EOVM) is intended to facilitate advisory service in an emergency situation when appropriate terrain/obstacle clearance minimum altitude cannot be maintained. The EOVM, and the service provided, are used only under the following conditions:

  1. The pilot has declared an emergency.
  2. The controller has determined an emergency condition exists or is imminent because of the pilots inability to maintain an appropriate terrain/obstacle clearance minimum altitude.

Note: Appropriate terrain/obstacle clearance minimum altitudes may be defined as minimum IFR altitude (MIA), minimum en route altitude (MEA), minimum obstacle clearance altitude (MOCA), or minimum vectoring altitude (MVA).

When providing emergency vectoring service, the controller advises the pilot that any headings issued are emergency advisories intended only to direct the aircraft toward and over an area of lower terrain/obstacle elevation. Altitudes and obstructions depicted on the EOVM are actual altitudes and locations of the obstacle/terrain and contain no lateral or vertical buffers for obstruction clearance.

Responsibility

ATC, in communication with an aircraft in distress, should handle the emergency and coordinate and direct the activities of assisting facilities. ATC will not transfer this responsibility to another facility unless that facility can better handle the situation. When an ATC facility receives information about an aircraft in distress, they forward detailed data to the center in the area of the emergency. Centers serve as central points for collecting information, coordinating with search and rescue (SAR) and distributing information to appropriate agencies.

Although 121.5 megahertz and 243.0 megahertz are emergency frequencies, the pilot should keep the aircraft on the initial contact frequency. The pilot should change frequencies only when a valid reason exists. When necessary, and if weather and circumstances permit, ATC should recommend that aircraft maintain or increase altitude to improve communications, radar, or DF reception.

Escort

An escort aircraft, if available, should consider and evaluate an appropriate formation. Special consideration must be given if maneuvers take the aircraft through clouds. Aircraft should not execute an in-flight join up during emergency conditions unless both crews involved are familiar with and capable of formation flight and can communicate and have visual contact with each other.

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Emergency Procedures (Part Two)

Filed Under: Emergency Procedures

Aircraft System Malfunction

Preventing aircraft system malfunctions that might lead to an in-flight emergency begins with a thorough preflight inspection. In addition to items normally checked before visual flight rules (VFR) flight, pilots intending to fly instrument flight rules (IFR) should pay particular attention to antennas, static wicks, anti-icing/de-icing equipment, pitot tube, and static ports. During taxi, verify operation and accuracy of all flight instruments. The pilots must ensure that all systems are operational before departing into IFR conditions.

Generator Failure

Depending on aircraft being flown, a generator failure is indicated in different ways. Some aircraft use an ammeter that indicates the state of charge or discharge of the battery. A positive indication on the ammeter indicates a charge condition; a negative indication reveals a discharge condition. Other aircraft use a load meter to indicate the load being carried by the generator. If the generator fails, a zero load indication is shown on the load meter. Review the appropriate aircraft operator’s manual for information on the type of systems installed in the aircraft.

Once a generator failure is detected, the pilot must reduce electrical load on the battery and land as soon as practical. Depending on electrical load and condition of the battery, sufficient power may be available for an hour or more of flight or for only a matter of minutes. The pilot must be familiar with systems requiring electricity to run and which continue to operate without power. In aircraft with multiple generators, care should be taken to reduce electrical load to avoid overloading the operating generator(s). The pilot can attempt to troubleshoot generator failure by following established procedures published in the appropriate aircraft operator’s manual. If the generator cannot be reset, inform ATC of an impending electrical failure.

Instrument Failure

System or instrument failure is usually identified by a warning indicator or an inconsistency between indications on the attitude indicator, supporting performance instruments, and instruments at the other pilot station, if so equipped. Aircraft control must be maintained while the pilot identifies the failed components and expedite cross-check including all flight instruments. The problem may be individual instrument failure or a system failure affecting several instruments.

One method of identification involves an immediate comparison of the attitude indicator with rate-of-turn indicator and vertical speed indicator (VSI). Along with providing pitch-and-bank information, this technique compares the static system with the pressure system and electrical system. Identify the failed components and use remaining functional instruments to maintain aircraft control. Attempt to restore inoperative components by checking the appropriate power source, changing to a backup or alternate system, and resetting the instrument if possible. Covering failed instruments may enhance the ability to maintain aircraft control and navigate the aircraft. ATC should be notified of the problem and, if necessary, declare an emergency before the situation deteriorates beyond the ability to recover.

 

Pitot/Static System Failure

A pitot or static system failure can also cause erratic and unreliable instrument indications. When a static system problem occurs, it affects the airspeed indicator, altimeter, and VSI. In the absence of an alternate static source in an unpressurized aircraft, the pilot could break the glass on the VSI because it is not required for instrument flight. Breaking the glass provides both the altimeter and airspeed indicator a source of static pressure, but pilots should be cautious because breaking the glass can cause additional instrument errors. Before considering, pilots should be familiar with their aircraft’s specific procedures for static problems.

Loss of Situational Awareness (SA)

SA is an overall assessment of environmental elements and how they affect flight. SA permits the pilot to make decisions ahead of time and allows evaluation of several different options. Conversely, a pilot who is missing important information about the flight is apt to make reactive decisions. Poor SA means that the pilot lacks vision regarding future events that can force him or her to make decisions quickly often with limited options. During an IFR flight, pilots operate at varying levels of SA. For example, a pilot may be en route to a destination with a high level of SA when ATC issues an unexpected standard terminal arrival route (STAR). Because the STAR is unexpected and the pilot is unfamiliar with the procedure, SA is reduced. However, after becoming familiar with the STAR and resuming normal navigation, the pilot returns to a higher level of SA.

Factors reducing SA include distractions, unusual or unexpected events, complacency, high workload, unfamiliar situations, and inoperative equipment. In some situations, a loss of SA may be beyond a pilot’s control. With an electrical system failure and associated loss of an attitude indication, a pilot may find the aircraft in an unusual attitude. In this situation, established procedures are used to regain SA and aircraft control. Pilots must be alert to loss of SA especially when hampered by a reactive mindset. To regain SA, reassess the situation and work toward understanding what the problem is. The pilot may need to seek additional information from other sources, such as navigation instruments, other crewmembers, or ATC.

 

Inadvertent Instrument Meteorological Condition (IIMC)

Some pilots have the misconception that inadvertent instrument meteorological condition (IIMC) does not apply to an IFR flight. The following examples could cause a pilot to inadvertently encounter IMC.

  1. The aircraft has entered visual meteorological conditions (VMC) during an instrument approach procedure (IAP) and while circling to land encounters IMC.
  2. During a non-precision IAP, the aircraft, in VMC, levels at the MDA just below the overcast. Suddenly, the aircraft re-enters the overcast because either the pilot was unable to correctly hold his or her altitude and climbed back into the overcast, or the overcast sloped downward ahead of the aircraft and, while maintaining the correct MDA, the aircraft re-entered the clouds.
  3. After inadvertently re-entering the clouds, the pilot maintains aircraft control, and then maneuvers to the published holding fix, while contacting ATC. If navigational guidance or pilot SA were lost, the pilot would then climb to the published MSA (see AIM paragraph 5-4-7c).

In order to survive an encounter with IIMC, a pilot must recognize and accept the seriousness of the situation. The pilot will need to immediately commit to the instruments and perform the proper recovery procedures.

Flight Literacy Recommends

Rod Machado's Instrument Pilot's Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).

Emergency Procedures (Part One)

Filed Under: Emergency Procedures

Emergencies

An emergency can be either a distress or urgency condition as defined in the pilot/controller glossary. Distress is defined as a condition of being threatened by serious and/or imminent danger and requiring immediate assistance. Urgency is defined as a condition of being concerned about safety and requiring timely but not immediate assistance; a potential distress condition.

Pilots do not hesitate to declare an emergency when faced with distress conditions, such as fire, mechanical failure, or structural damage. However, some are reluctant to report an urgency condition when encountering situations that may not be immediately perilous but are potentially catastrophic. An aircraft is in an urgency condition the moment that the pilot becomes doubtful about position, fuel endurance, weather, or any other condition that could adversely affect flight safety. The time for a pilot to request assistance is when an urgent situation may, or has just occurred, not after it has developed into a distress situation.

The pilot in command (PIC) is responsible for crew, passengers, and operation of the aircraft at all times. Title 14 of the Code of Federal Regulations (14 CFR) part 91, § 91.3 allows deviations from regulations during emergencies that allow the PIC to make the best decision to ensure safety of all personnel during these contingencies. Also, by declaring an emergency during flight, that aircraft becomes a priority to land safely. Pilots who become apprehensive for their safety for any reason should request assistance immediately. Assistance is available in the form of radio, radar, direction finding (DF) stations, and other aircraft.

Inadvertent Thunderstorm Encounter

A pilot should always avoid intentionally flying through a thunderstorm of any intensity; however, certain conditions may be present that could lead to an inadvertent thunderstorm encounter. For example, flying in areas where thunderstorms are embedded in large cloud masses may make thunderstorm avoidance difficult, even when the aircraft is equipped with thunderstorm detection equipment. Pilots must be prepared to deal with inadvertent thunderstorm penetration. At the very least, a thunderstorm encounter subjects the aircraft to turbulence that could be severe. The pilot, as well as the crew and any passengers, should tighten seat belts and shoulder harnesses and secure any loose items in the cabin or flight deck.

As with any emergency, the first order of business is to fly the aircraft. The pilot workload is high; therefore, increased concentration is necessary to maintain an instrument scan. Once in a thunderstorm, it is better to maintain a course straight through the thunderstorm rather than turning around. A straight course most likely gets the pilot out of the hazard in the least amount of time, and turning maneuvers only increase structural stress on the aircraft.

Reduce power to a setting that maintains a recommended turbulence penetration speed as described in the appropriate aircraft operator’s manual, and try to minimize additional power adjustments. Concentrate on keeping the aircraft in a level attitude while allowing airspeed and altitude to fluctuate. Similarly, if using autopilot, disengage altitude and speed hold modes because they only increase the aircraft’s maneuvering, which increases structural stress.

During a thunderstorm encounter, the potential for icing also exists. As soon as possible, if the aircraft is so equipped, turn on anti-icing/deicing equipment. Icing can be rapid at any altitude, and may lead to power failure and/or loss of airspeed indication. Lightning is also present in a thunderstorm and can temporarily blind the pilot. To reduce risk, turn up flight deck lights to the highest intensity, concentrate on flight instruments, and resist the urge to look outside.

 

Inadvertent Icing Encounter

Because icing is unpredictable, pilots may find themselves in icing conditions although they have done everything to avoid the condition. To stay alert to this possibility while operating in visible moisture, pilots should monitor the outside air temperature (OAT).

Anti-icing/de-icing equipment is critical to safety of the flight. If anti-icing/de-icing equipment is not used before sufficient ice has accumulated, it may not be able to remove all ice accumulation. Use of anti-icing/de-icing reduces power availability; therefore, pilots should be familiar with the aircraft operator’s manual for use of anti-icing/de-icing equipment.

Before entering visible moisture with temperatures at five degrees above freezing or cooler, activate appropriate anti-icing/de-icing equipment in anticipation of ice accumulation; early ice detection is critical. Detecting ice may be particularly difficult during night flight. The pilot may need to use a flashlight to check for ice accumulation on the wings, fuselage, landing gear, and horizontal stabilizer. At the first indication of ice accumulation, the pilot must act to circumvent icing conditions. Options for action once ice has begun to accumulate on the aircraft are the following:

  • Move to an altitude with significantly colder temperatures.
  • Move to an altitude with temperatures above freezing.
  • Fly to an area clear of visible moisture.
  • Change the heading, and fly to an area of known non-icing conditions.

If these options are not available, consider an immediate landing at the nearest suitable airport. Anti-icing/de-icing equipment does not allow aircraft to operate in icing conditions indefinitely; it only provides more time to evade icing conditions. If icing is encountered, an aircraft controllability check should be considered in the landing configuration. Give careful consideration to configuration changes that might produce unanticipated aircraft flight dynamics.

Precipitation Static

Precipitation static occurs when accumulated static electricity discharges from extremities of the aircraft. This discharge has the potential to create problems with the aircraft’s instruments. These problems range from serious, such as complete loss of VHF communications and erroneous magnetic compass readings, to the annoyance of high-pitched audio squealing.

Precipitation static is caused when an aircraft encounters airborne particles during flight (rain or snow) and develops a negative charge. It can also result from atmospheric electric fields in thunderstorm clouds. When a significant negative voltage level is reached, the aircraft discharges it, creating electrical disturbances. To reduce problems associated with precipitation static, the pilot ensures that the aircraft’s static wicks are maintained and accounted for. All broken or missing static wicks should be replaced before an instrument flight.

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Rod Machado's Instrument Pilot's Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).

Helicopter Instrument Procedures (Part Five)

Filed Under: Helicopter Instrument Procedures

Approach to a PinS

The note associated with these procedures is: “PROCEED VFR FROM (NAMED MAP) OR CONDUCT THE SPECIFIED MISSED APPROACH.” They may be developed as a special or public procedure where the MAP is located more than 2 SM from the landing site, the turn from the final approach to the visual segment is greater than 30 degrees, or the VFR segment from the MAP to the landing site has obstructions that require pilot actions to avoid them. Figure 7-13 is an example of a public PinS approach that allows the pilot to fly to one of four heliports after reaching the MAP.

Figure 7-13. COPTER RNAV (GPS) 250° at New York/La Guardia Airport.
Figure 7-13. COPTER RNAV (GPS) 250° at New York/La Guardia Airport.

For Part 135 operations, pilots may not begin the instrument approach unless the latest weather report indicates that the weather conditions are at or above the authorized IFR or VFR minimums as required by the class of airspace, operating rule and/or OpSpecs, whichever is higher. Visual contact with the landing site is not required; however, prior to the MAP, for either Part 91 or 135 operators, the pilot must determine if the flight visibility meets the basic VFR minimums required by the class of airspace, operating rule and/or OpSpecs (whichever is higher). The visibility is limited to no lower than that published in the procedure until canceling IFR. If VFR minimums do not exist, then the published MAP must be executed. The pilot must contact air traffic control (ATC) upon reaching the MAP, or as soon as practical after that, and advise whether executing the missed approach or canceling IFR and proceeding VFR.

To proceed VFR in uncontrolled airspace, Part 135 operators must observe minimum regulatory VFR conditions, but under some conditions, such as provided for in 14 CFR 135.613 for HAA operators, specific weather minimums are required when near the MAP and the heliport of intended landing. These minimums apply regardless of whether the approach is located on the plains of Oklahoma or in the Colorado mountains. However, for heliports located farther than 3 NM from the heliport, Part135 HAA operators are held to an even higher standard and the minimums and lighting conditions contained in Figure 7-15 apply to the entire route. Mountainous terrain at night with low light conditions requires a ceiling of 1,000 feet and either 3 SM or 5 SM visibility depending on whether it has been determined as part of the operator’s local flying area.

Figure 7-15. Point-in-space (PinS) approach examples for Part 91 and Part 135 operations.
Figure 7-15. Point-in-space (PinS) approach examples for Part 91 and Part 135 operations.

In Class B, C, D, and E surface area airspace, a SVFR clearance may be obtained if SVFR minimums exist. On your flight plan, give ATC a heads up about your intentions by entering the following in the remarks section: “Request SVFR clearance after the MAP.”

Approach to a Specific VFR Heliport

The note associated with these procedures is: “PROCEED VISUALLY FROM (NAMED MAP) OR CONDUCT THE SPECIFIED MISSED APPROACH.” Due to their unique characteristics, these approaches require training. They are developed for hospitals, oil rigs, private heliports, etc. As Specials, they require Flight Standards approval by a Letter of Authorization (LOA) for Part 91 operators or by OpSpecs for Part 135 operators. For public procedures, the heliport associated with these procedures must be located within 2 SM of the MAP, the visual segment between the MAP and the heliport evaluated for obstacle hazards, and the heliport must meet the appropriate VFR heliport recommendations of AC 150/5390-2, Heliport Design.

The PinS optimum location is 0.65 NM from the heliport. This provides an adequate distance to decelerate and land from an approach speed of 70 KIAS. Certain airframes may be certified to fly at reduced VMINI or below VMINI speeds as a result of flight control design or adherence to AC 29-2, Certification of Transport Category Rotorcraft. In these cases, an approach procedure stating the minimum certified airspeed or flight below VMINI should be annotated on the approach procedure. The distance also permits optimal blending of obstacle clearance criteria with noninstrument heliport approach areas.

 

The visibility minimum is based on the distance from the MAP to the heliport, among other factors (e.g., height above the heliport elevation when at the MAP MDA). The pilot is required to acquire and maintain visual contact with the heliport final approach and takeoff (FATO) area at or prior to the MAP. Obstacle or terrain avoidance from the MAP to the heliport is the responsibility of the pilot. Pilots need to level off when reaching the MDA, which may occur before arriving at the MAP, until reaching the visual approach angle on the approach path to clear the obstacles. If the required weather minimums do not exist, then the published MAP must be executed at the MAP because IFR obstruction clearance areas are not applied to the visual segment of the approach and a missed approach segment protection is not provided between the MAP and the heliport. As soon as practicable after reaching the MAP, the pilot advises ATC whether cancelling IFR and proceeding visually or executing the missed approach.

Inadvertent IMC

Whether it is a corporate or HAA operation, helicopter pilots sometimes operate in challenging weather conditions. An encounter with weather that does not permit continued flight under VFR might occur when conditions do not allow for the visual determination of a usable horizon (e.g., fog, snow showers, or night operations over unlit surfaces such as water). Flight in conditions of limited visual contrast should be avoided since this can result in a loss of horizontal or surface reference, and obstacles such as wires become perceptually invisible. To prevent spatial disorientation, loss of control (LOC) or CFIT, pilots should slow the helicopter to a speed that provides a controlled deceleration in the distance equal to the forward visibility. The pilot should look for terrain that provides sufficient contrast to either continue the flight or to make a precautionary landing. If spatial disorientation occurs and a climb into IMC is not feasible due to fuel state, icing conditions, equipment, etc., make every effort to land the helicopter with a slight forward descent to prevent any sideward or rearward motion.

All helicopter pilots should receive training on avoidance and recovery from inadvertent IMC with emphasis on avoidance. An unplanned transition from VMC to IMC flight is an emergency that involves a different set of pilot actions. It requires the use of different navigation and operational procedures, interaction with ATC, and crewmember resource management (CRM). Consideration should be given to the local flying area’s terrain, airspace, air traffic facilities, weather (including seasonal affects such as icing and thunderstorms), and available airfield/heliport approaches.

Training should emphasize the identification of circumstances conducive to inadvertent IMC and a strategy to abandon continued VFR flight in deteriorating conditions. This strategy should include a minimum altitude/airspeed combination that provides for an off airport/heliport landing, diverting to better conditions, or initiating an emergency transition to IFR. Pilots should be able to readily identify the minimum initial altitude and course in order to avoid CFIT. Current IFR en route and approach charts for the route of flight are essential. A GPS navigation receiver with a moving map provides exceptional situational awareness for terrain and obstacle avoidance.

Training for an emergency transition to IFR should include full and partial panel instrument flight, unusual attitude recovery, ATC communications, and instrument approaches. If an ILS is available and the helicopter is equipped, an ILS approach should be made. Otherwise, if the helicopter is equipped with an IFR approach-capable GPS receiver with a current database, a GPS approach should be made. If neither, an ILS or GPS procedure is available use another instrument approach.

Upon entering inadvertent IMC, priority must be given to control of the helicopter. Keep it simple and take one action at a time.

  • Control. First use the wings on the attitude indicator to level the helicopter. Maintain heading and increase to climb power. Establish climb airspeed at the best angle of climb but no slower than VMINI.
  • Climb. Climb straight ahead until your crosscheck is established. Then make a turn only to avoid terrain or objects. If an altitude has not been previously established with ATC to climb to for inadvertent IMC, then you should climb to an altitude that is at least 1,000 feet above the highest known object and that allows for contacting ATC.
  • Communicate. Attempt to contact ATC as soon as the helicopter is stabilized in the climb and headed away from danger. If the appropriate frequency is not known, you should attempt to contact ATC on either very high frequency (VHF) 121.5 or ultra high frequency (UHF) 243.0. Initial information provided to ATC should be your approximate location, that inadvertent IMC has been encountered and an emergency climb has been made, your altitude, amount of flight time remaining (fuel state), and number of persons on board. You should then request a vector to either VFR weather conditions or to the nearest suitable airport/heliport that conditions will support a successful approach. If unable to contact ATC and a transponder code has not been previously established with ATC for inadvertent IMC, change the transponder code to 7700.

A radio altimeter is a necessity for alerting the pilot when inadvertently going below the minimum altitude. Barometric altimeters are subject to inaccuracies that become important in helicopter IFR operations, especially in cold temperatures.

IFR Heliports

AC 150/5390-2, Heliport Design, provides recommendations for heliport design to support non-precision, approach with vertical guidance (APV), and precision approaches to a heliport. When a heliport does not meet the criteria of AC 150/5390-2, FAA Order 8260.42, United States Standard for Helicopter Area Navigation (RNAV), requires that an instrument approach be published as a Special procedure with annotations that special aircrew qualifications are required to fly the procedure. Currently, there are no operational civil IFR heliports in the U.S., although the U.S. military has some non-precision and precision approach procedures to IFR heliports.

Flight Literacy Recommends

Rod Machado's Instrument Pilot's Handbook -Flight Literacy recommends Rod Machado's products because he takes what is normally dry and tedious and transforms it with his characteristic humor, helping to keep you engaged and to retain the information longer. (see all of Rod Machado's Products).

Helicopter Instrument Procedures (Part Four)

Filed Under: Helicopter Instrument Procedures

Copter Only Approaches to An Airport or Heliport

Pilots flying Copter SIAPs, other than GPS, may use the published minima with no reductions in visibility allowed. The maximum airspeed is 90 KIAS on any segment of the approach or missed approach. Figure 7-10 illustrates the COPTER ILS or LOC RWY 13 approach at NewYork/La Guardia (LGA) airport.

Figure 7-10. The COPTER ILS or LOC RWY 13 approach at New York/La Guardia (LGA) airport.
Figure 7-10. The COPTER ILS or LOC RWY 13 approach at New York/La Guardia (LGA) airport.

Copter ILS approaches to Category (CAT) I facilities with DAs no lower than a 200-foot HAT provide an advantage over a conventional ILS of shorter final segments and lower minimums (based on the 20:1 missed approach surface). There are also Copter approaches with minimums as low as 100-foot HAT and 1⁄4 SM visibility. Approaches with a HAT below 200 feet are annotated with the note: “Special Aircrew & Aircraft Certification Required” since the FAA must approve the helicopter and its avionics, and the flight crew must have the required experience, training, and checking.

The ground facilities (approach lighting, signal in space, hold lines, maintenance, etc.) and air traffic infrastructure for CAT II ILS approaches are required to support these procedures. The helicopter must be equipped with an AP, FD, or head up guidance system, alternate static source (or heated static source), and radio altimeter. The pilot must have at least a private pilot helicopter certificate, an instrument helicopter rating, and a type rating if the helicopter requires a type rating. Pilot experience requires the following flight times: 250 pilot in command (PIC), 100 helicopter PIC, 50 night PIC, 75 hours of actual or simulated instrument flight time, including at least 25 hours of actual or simulated instrument flight time in a helicopter or a helicopter flight simulator, and the appropriate recent experience, training and check. For Copter CAT II ILS operations below 200 feet HAT, approach deviations are limited to 1⁄4 scale of the localizer or glide slope needle. Deviations beyond that require an immediate missed approach unless the pilot has at least one of the visual references in sight and otherwise meets the requirements of 14 CFR Part 91.175(c). The reward for this effort is the ability to fly Copter ILS approaches with minima that are sometimes below the airplane CAT II minima. The procedure to apply for this certification is available from your local Flight Standards District Office (FSDO).

Copter GPS Approaches to an Airport or Heliport

Pilots flying Copter GPS or WAAS SIAPs must limit the speed to 90 KIAS on the initial and intermediate segment of the approach and to no more than 70 KIAS on the final and missed approach segments. If annotated, holding may also be limited to 90 KIAS to contain the helicopter within the small airspace provided for helicopter holding patterns.

During testing for helicopter holding, the optimum airspeed and leg length combination was determined to be 90 KIAS with a 3 NM outbound leg length. Consideration was given to the wind drift on the dead reckoning entry leg at slower speeds, the turn radius at faster airspeeds, and the ability of the helicopter in strong wind conditions to intercept the inbound course prior to the holding fix. The published minimums are to be used with no visibility reductions allowed. Figure 7-11 is an example of a Copter GPS PinS approach that allows the helicopter to fly VFR from the MAP to the heliport.

Figure 7-11. COPTER RNAV (GPS) 291° at Indianapolis Downtown Heliport.
Figure 7-11. COPTER RNAV (GPS) 291° at Indianapolis Downtown Heliport.

The final and missed approach protected airspace providing obstacle and terrain avoidance is based on 70 KIAS, with a maximum 10-knot tailwind component. It is absolutely essential that pilots adhere to the 70 KIAS limitation in procedures that include an immediate climbing and turning missed approach. Exceeding the airspeed restriction increases the turning radius significantly and can cause the helicopter to leave the missed approach protected airspace. This may result in controlled flight into terrain (CFIT) or obstacles.

If a helicopter has a VMINI greater than 70 knots, then it is not capable of conducting this type of approach. Similarly, if the autopilot in “go-around” mode climbs at a VYI greater than 70 knots, then that mode cannot be used. It is the responsibility of the pilot to determine compliance with missed approach climb gradient requirements when operating at speeds other than VY or VYI. Missed approaches that specify an “IMMEDIATE CLIMBING TURN” have no provision for a straight ahead climbing segment before turning. A straight segment results in exceeding the protected airspace limits.

 

Protected obstacle clearance areas and surfaces for the missed approach are established on the assumption that the missed approach is initiated at the DA point and for non-precision approaches no lower than the MDA at the MAP (normally at the threshold of the approach end of the runway). The pilot must begin the missed approach at those points. Flying beyond either point before beginning the missed approach results in flying below the protected obstacle clearance surface (OCS) and can result in a collision with an obstacle.

The missed approach segment U.S. Standard for Terminal Instrument Procedures (TERPS) criteria for all Copter approaches take advantage of the helicopter’s climb capabilities at slow airspeeds, resulting in high climb gradients. [Figure 7-12] The OCS used to evaluate the missed approach is a 20:1 inclined plane. This surface is twice as steep for the helicopter as the OCS used to evaluate the airplane missed approach segment. The helicopter climb gradient is, therefore, required to be double that of the airplane’s required missed approach climb gradient.

Figure 7-12. Obstacle clearance surface (OCS).
Figure 7-12. Obstacle clearance surface (OCS). [click image to enlarge]
A minimum climb gradient of at least 400 ft/NM is required unless a higher gradient is published on the approach chart (e.g., a helicopter with a ground speed of 70 knots is required to climb at a rate of 467 fpm (467 fpm = 70 KIAS × 400 feet per NM/60 seconds)). The advantage of using the 20:1 OCS for the helicopter missed approach segment instead of the 40:1 OCS used for the airplane is that obstacles that penetrate the 40:1 missed approach segment may not have to be considered. The result is the DA/MDA may be lower for helicopters than for other aircraft. The minimum required climb gradient of 400 ft/ NM for the helicopter in a missed approach provides 96 feet of required obstacle clearance (ROC) for each NM of flightpath.

Helicopter Approaches to VFR Heliports

Helicopter approaches to VFR heliports are normally developed either as public procedures to a PinS that may serve more than one heliport or as a special procedure to a specific VFR heliport that requires pilot training due to its unique characteristics. These approaches can be developed using very high frequency omni-directional range (VOR) or automatic direction finder (ADF), but area navigation (RNAV) using GPS is the most common system used today. RNAV using the WAAS offers the most advantages because it can provide lower approach minimums, narrower route widths to support a network of approaches, and may allow the heliport to be used as an alternate. A majority of the special procedures to a specific VFR heliport are developed in support of HAA operators and have a “Proceed Visually” segment between the MAP and the heliport. Public procedures are developed as a PinS approach with a “Proceed VFR” segment between the MAP and the landing area. These PinS “Proceed VFR” procedures specify a course and distance from the MAP to the available heliports in the area.

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Helicopter Instrument Procedures (Part Three)

Filed Under: Helicopter Instrument Procedures

Helicopter VFR Minimums

Helicopters have the same VFR minimums as airplanes with two exceptions. In Class G airspace or under a special visual flight rule (SVFR) clearance, helicopters have no minimum visibility requirement but must remain clear of clouds and operate at a speed that is slow enough to give the pilot an adequate opportunity to see other aircraft or an obstruction in time to avoid a collision. Helicopters are also authorized (14 CFR Part 91, appendix D, § 3) to obtain SVFR clearances at airports with the designation NO SVFR on the sectional chart or in the Chart Supplement (CS). Figure 7-7 shows the visibility and cloud clearance requirements for VFR and SVFR. However, lower minimums associated with Class G airspace and SVFR do not take the place of the VFR minimum requirements of either Part 135 regulations or respective OpSpecs.

Figure 7-7. Helicopter VFR minimums.
Figure 7-7. Helicopter VFR minimums.

Knowledge of all VFR minimums is required in order to determine if a PinS approach can be conducted or if a SVFR clearance is required to continue past the (MAP). These approaches and procedures are discussed in detail later.

Helicopter IFR Takeoff Minimums

14 CFR Part 91 imposes no takeoff minimums on the helicopter pilot. However, Rotorcraft Flight Manuals may require the helicopter to attain at least Vmini before entering IMC. For most helicopters, this requires a distance of approximately 1⁄2 mile and an altitude of 100 feet. If departing with a steeper climb gradient, some helicopters may require additional altitude to accelerate to VMINI. To maximize safety, always consider using the Part 135 operator standard takeoff visibility minimum of 1⁄2 statute mile (SM) or the charted departure minima, whichever is higher. A charted departure that provides protection from obstacles has either a higher visibility requirement, climb gradient, and/or departure path. Part 135 operators are required to adhere to the takeoff minimums prescribed in the instrument approach procedures (IAPs) for the airport.

Helicopter IFR Alternates

The pilot must file for an alternate if weather reports and forecasts at the proposed destination do not meet certain minimums. These minimums differ for Part 91 and Part 135 operators.

Part 91 Operators

Part 91 operators are not required to file an alternate if, at the estimated time of arrival (ETA) and for 1 hour after, the ceiling is at least 1,000 feet above the airport elevation or 400 feet above the lowest applicable approach minima, whichever is higher, and the visibility is at least 2 SM. If an alternate is required, an airport can be used if the ceiling is at least 200 feet above the minimum for the approach to be flown and visibility is at least 1 SM, but never less than the minimum required for the approach to be flown. If no instrument approach procedure has been published for the alternate airport, the ceiling and visibility minima are those allowing descent from the MEA, approach, and landing under basic VFR.

 

Part 135 Operators

Part 135 operators are not required to file an alternate if, for at least one hour before and one hour after the ETA, the ceiling is at least 1,500 feet above the lowest circling approach minimum descent altitude (MDA). If a circling instrument approach is not authorized for the airport, the ceiling must be at least 1,500 feet above the lowest published minimum or 2,000 feet above the airport elevation, whichever is higher. For the IAP to be used at the destination airport, the forecasted visibility for that airport must be at least 3 SM or 2 SM more than the lowest applicable visibility minimums, whichever is greater.

Alternate landing minimums for flights conducted under 14 CFR Part 135 are described in the OpSpecs for that operation. All helicopters operated under IFR must carry enough fuel to fly to the intended destination, fly from that airport to the filed alternate, if required, and continue for 30 minutes at normal cruising speed.

Helicopter Instrument Approaches

Many new helicopter IAPs have been developed to take advantage of advances in both avionics and helicopter technology.

Figure 7-8. Part 97 excerpt.
Figure 7-8. Part 97 excerpt.

Standard Instrument Approach Procedures to an Airport

Helicopters flying standard instrument approach procedures (SIAP) must adhere to the MDA or decision altitude for Category A airplanes and may apply the 14 CFR Part 97.3 (d-1) rule to reduce the airplane Category A visibility by half but in no case less than 1⁄4 SM or 1,200 RVR. [Figure 7-8] The approach can be initiated at any speed up to the highest approach category authorized; however, the speed on the final approach segment must be reduced to the Category A speed of less than 90 KIAS before the MAP in order to apply the visibility reduction. A constant airspeed is recommended on the final approach segment to comply with the stabilized approach concept since a decelerating approach may make early detection of wind shear on the approach path more difficult. [Figure 7-9]

Figure 7-9. Helicopter use of standard instrument approach procedures.
Figure 7-9. Helicopter use of standard instrument approach procedures.

When visibility minimums must be increased for inoperative components or visual aids, use the Inoperative Components and Visual Aids Table (provided in the front cover of the U.S. Terminal Procedures) to derive the Category A minima before applying any visibility reduction. The published visibility may be increased above the standard visibility minima due to penetrations of the 20:1 and 34:1 final approach obstacle identification surfaces (OIS). The minimum visibility required for 34:1 penetrations is 3⁄4 SM and for 20:1 penetrations 1 SM, which is discussed in the Improvement Plans category of this section. When there are penetrations of the final approach OIS, a visibility credit for approach lighting systems is not allowed for either airplane or helicopter procedures that would result in values less than the appropriate 3⁄4 SM or 1 SM visibility requirement. The 14 CFR Part 97.3 visibility reduction rule does not apply, and you must take precautions to avoid any obstacles in the visual segment. Procedures with penetrations of the final approach OIS are annotated at the next amendment with “Visibility Reduction by Helicopters NA.”

Until all the affected SIAPs have been annotated, an understanding of how the standard visibilities are established is the best aid in determining if penetrations of the final approach OIS exists. Some of the variables in determining visibilities are: decision altitude (DA)/MDA height above touchdown (HAT), height above airport (HAA), distance of the facility to the MAP (or the runway threshold for non- precision approaches), and approach lighting configurations.

 

The standard visibility requirement, without any credit for lights, is 1 SM for non-precision approaches and 3⁄4 SM for precision approaches. This is based on a Category A airplane 250–320 feet HAT/HAA; for non-precision approaches a distance of 10,000 feet or less from the facility to the MAP (or runway threshold). For precision approaches, credit for any approach light configuration; for non-precision approaches (with a 250 HAT) configured with a Medium Intensity Approach Lighting System (MALSR), Simplified Short Approach Lighting System (SSALR), or Approach Lighting System With Sequenced Flashing Lights (ALSF)-1 normally results in a published visibility of 1⁄2 SM.

Consequently, if an ILS is configured with approach lights or a non-precision approach is configured with MALSR, SSALR, or ALSF-1 lighting configurations and the procedure has a published visibility of 3⁄4 SM or greater, a penetration of the final approach OIS may exist. Also, pilots are unable to determine whether there are penetrations of the final approach OIS if a non-precision procedure does not have approach lights or is configured with ODALS, MALS, or SSALS/SALS lighting since the minimum published visibility is 3⁄4 SM or greater.

As a rule of thumb, approaches with published visibilities of 3⁄4 SM or more should be regarded as having final approach OIS penetrations and care must be taken to avoid any obstacles in the visual segment.

Approaches with published visibilities of 1⁄2 SM or less are free of OIS penetrations and the visibility reduction in Part 97.3 is authorized.

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Helicopter Instrument Procedures (Part Two)

Filed Under: Helicopter Instrument Procedures

Helicopter Flight Manual Limitations

Helicopters are certificated for IFR operations with either one or two pilots. Certain equipment is required to be installed and functional for two-pilot operations and additional equipment is required for single-pilot operation.

In addition, the Helicopter Flight Manual (HFM) defines systems and functions that are required to be in operation or engaged for IFR flight in either the single or two-pilot configurations. Often, in a two-pilot operation, this level of augmentation is less than the full capability of the installed systems. Likewise, a single-pilot operation may require a higher level of augmentation.

The HFM also identifies other specific limitations associated with IFR flight. Typically, these limitations include, but are not limited to:

  • Minimum equipment required for IFR flight (in some cases, for both single-pilot and two-pilot operations)
  • VMINI (minimum speed—IFR) [Figure 7-2]
  • VNEI (never exceed speed—IFR)
  • Maximum approach angle
  • Weight and center of gravity (CG) limits
  • Helicopter configuration limitations (such as door positions and external loads)
  • Helicopter system limitations (generators, inverters, etc.)
  • System testing requirements (many avionics and AFCS, AP, and FD systems incorporate a self-test feature)
  • Pilot action requirements (for example, the pilot must have hands and feet on the controls during certain operations, such as an instrument approach below certain altitudes)

Figure 7-2. VMINI limitations, maximum IFR approach angles and G/A mode speeds for selected IFR certified helicopters.
Figure 7-2. VMINI limitations, maximum IFR approach angles and G/A mode speeds for selected IFR certified helicopters. [click image to enlarge]
Final approach angles/descent gradient for public approach procedures can be as high as 7.5 degrees/795 ft/NM. At 70 knots indicated airspeed (KIAS) (no wind), this equates to a descent rate of 925 fpm. With a 10-knot tailwind, the descent rate increases to 1,056 fpm. “Copter” Point-in-space (PinS) approach procedures are restricted to helicopters with a maximum VMINI of 70 KIAS and an IFR approach angle that enables them to meet the final approach angle/descent gradient. Pilots of helicopters with a VMINI of 70 KIAS may have inadequate control margins to fly an approach that is designed with the maximum allowable angle/descent gradient or minimum allowable deceleration distance from the missed approach point (MAP) to the heliport. The “Copter” PinS final approach segment is limited to 70 KIAS since turn containment and the deceleration distance from the MAP to the heliport may not be adequate at faster speeds. For some helicopters, engaging the autopilot may increase the VMINI to a speed greater than 70 KIAS, or in the “go around” (G/A) mode, require a speed faster than 70 KIAS. [Figure 7-2] It may be possible for these helicopters to be flown manually on the approach or on the missed approach in a mode other than the G/A mode.

Since slower IFR approach speeds enable the helicopter to fly steeper approaches and reduces the distance from the heliport that is required to decelerate the helicopter, you may want to operate your helicopter at speeds slower than its established VMINI. The provision to apply for a determination of equivalent safety for instrument flight below VMINI and the minimum helicopter requirements are specified in Advisory Circulars (AC) 27-1, Certification of Normal Category Rotorcraft and AC 29-2, Certification of Transport Category Rotorcraft. Application guidance is available from the Rotorcraft Directorate Standards Staff, ASW-110, 2601 Meacham Blvd., Fort Worth, Texas, 761374298, (817) 222-5111.

 

Performance data may not be available in the HFM for speeds other than the best rate of climb speed. To meet missed approach climb gradients, pilots may use observed performance for similar weight, altitude, temperature, and speed conditions to determine equivalent performance. When missed approaches utilizing a climbing turn are flown with an autopilot, set the heading bug on the missed approach heading, and then at the MAP, engage the indicated airspeed mode, followed immediately by applying climb power and selecting the heading mode. This is important since the autopilot roll rate and maximum bank angle in the Heading Select mode are significantly more robust than in the NAV mode. Figure 7-3 represents the bank angle and roll limits of the S76 used by the FAA for flight testing. It has a roll rate in the Heading Select mode of 5 degrees per second with only 1 degree per second in the NAV mode. The bank angle in the Heading Select mode is 20 degrees, with only 17 degrees in the NAV Change Over mode. Furthermore, if the Airspeed Hold mode is not selected on some autopilots when commencing the missed approach, the helicopter accelerates in level flight until the best rate of climb is attained, and only then will a climb begin.

Figure 7-3. Autopilot bank angle and roll rate limits for the S-76 used by the William J. Hughes Technical Center for Flight Tests.
Figure 7-3. Autopilot bank angle and roll rate limits for the S-76
used by the William J. Hughes Technical Center for Flight Tests.

WAAS localizer performance (LP) lateral-only PinS testing conducted in 2005 by the FAA at the William J. Hughes Technical Center in New Jersey for helicopter PinS also captured the flight tracks for turning missed approaches. [Figure 7-4] The large flight tracks that resulted during the turning missed approach were attributed in part to operating the autopilot in the NAV mode and exceeding the 70 KIAS limit.

Figure 7-4. Flight tests at the William J. Hughes Technical Center point out the importance of airspeed control and using the correct technique to make a turning missed approach.
Figure 7-4. Flight tests at the William J. Hughes Technical Center point out the importance of airspeed control and using the correct technique to make a turning missed approach.

Operations Specifications

A flight operated under 14 CFR Part 135 has minimums and procedures more restrictive than a flight operated under 14 CFR Part 91. These Part 135 requirements are detailed in their operations specifications (OpSpecs). Helicopter Air Ambulance (HAA) operators have even more restrictive OpSpecs. Shown in Figure 7-5 is an excerpt from an OpSpecs detailing the minimums for precision approaches. The inlay in Figure 7-5 shows the minimums for the ILS Runway 3R approach at Detroit Metro Airport. With all lighting operative, the minimums for helicopter Part 91 operations are a 200-foot ceiling, and 1,200-feet runway visual range (RVR) – one-half airplane Category A visibility but no less than 1⁄4 SM/1,200 RVR. However, as shown in the OpSpecs, the minimum visibility this Part 135 operator must adhere to is 1,600 RVR. Pilots operating under 14 CFR Part 91 are encouraged to develop their own personal OpSpecs based on their own equipment, training, and experience.

Figure 7-5. Operations Specifications.
Figure 7-5. Operations Specifications. [click image to enlarge]

Minimum Equipment List (MEL)

A helicopter operating under 14 CFR Part 135 with certain installed equipment inoperative is prohibited from taking off unless the operation is authorized in the approved MEL. The MEL provides for some equipment to be inoperative if certain conditions are met. [Figure 7-6] In many cases, a helicopter configured for single-pilot IFR may depart IFR with certain equipment inoperative provided a crew of two pilots is used. Under 14 CFR Part 91, a pilot may defer certain items without an MEL if those items are not required by the type certificate, CFRs, or airworthiness directives (ADs), and the flight can be performed safely without them. If the item is disabled, removed, or marked inoperative, a logbook entry is made.

Figure 7-6. Example of a Minimum Equipment List (MEL).
Figure 7-6. Example of a Minimum Equipment List (MEL).
 

Pilot Proficiency

Helicopters of the same make and model may have variations in installed avionics that change the required equipment or the level of augmentation for a particular operation. The complexity of modern AFCS, AP, and FD systems requires a high degree of understanding to safely and efficiently control the helicopter in IFR operations. Formal training in the use of these systems is highly recommended for all pilots.

During flight operations, you must be aware of the mode of operation of the augmentation system and the control logic and functions employed. [Figure 7-2]

Figure 7-2. VMINI limitations, maximum IFR approach angles and G/A mode speeds for selected IFR certified helicopters.
Figure 7-2. VMINI limitations, maximum IFR approach angles and G/A mode speeds for selected IFR certified helicopters. [click image to enlarge]

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Helicopter Instrument Procedures (Part One)

Filed Under: Helicopter Instrument Procedures

Helicopter Instrument Flight Rule (IFR) Certification

It is very important that pilots be familiar with the IFR requirements for their particular helicopter. Within the same make, model, and series of helicopter, variations in the installed avionics may change the required equipment or the level of augmentation for a particular operation. The Automatic Flight Control System/Autopilot/Flight Director (AFCS/AP/FD) equipment installed in IFR helicopters can be very complex. For some helicopters, the AFCS/AP/ FD complexity requires formal training in order for the pilot(s) to obtain and maintain a high level of knowledge of system operation, limitations, failure indications, and reversionary modes. For a helicopter to be certified to conduct operations in instrument meteorological conditions (IMC), it must meet the design and installation requirements of Title 14 Code of Federal Regulations (14 CFR) Part 27, Appendix B (Normal Category) and Part 29, Appendix B (Transport Category), which is in addition to the visual flight rule (VFR) requirements.

These requirements are broken down into the following categories: flight and navigation equipment, miscellaneous requirements, stability, helicopter flight manual limitations, operations specifications, and minimum equipment list (MEL).

Flight and Navigation Equipment

The basic installed flight and navigation equipment for helicopter IFR operations is listed under 14 CFR Part 29, § 29.1303, with amendments and additions in Appendix B of 14 CFR Parts 27 and 29 under which they are certified. The list includes:

  • Clock
  • Airspeed indicator
  • Sensitive altimeter (A “sensitive” altimeter relates to the instrument’s displayed change in altitude over its range. For “Copter” Category (CAT) II operations, the scale must be in 20-foot intervals.) adjustable for barometric pressure.
  • Magnetic direction indicator
  • Free-air temperature indicator
  • Rate-of-climb (vertical speed) indicator
  • Magnetic gyroscopic direction indicator
  • Stand-by bank and pitch (attitude) indicator
  • Non-tumbling gyroscopic bank and pitch (attitude) indicator • Speed warning device (if required by 14 CFR Part 29)

Miscellaneous Requirements

  • Overvoltage disconnect
  • Instrument power source indicator
  • Adequate ice protection of IFR systems
  • Alternate static source (single-pilot configuration)
  • Thunderstorm lights (transport category helicopters)
 

Stabilization and Automatic Flight Control System (AFCS)

Helicopter manufacturers normally use a combination of a stabilization and/or AFCS in order to meet the IFR stability requirements of 14 CFR Parts 27 and 29. These systems include:

  • Aerodynamic surfaces, which impart some stability or control capability that generally is not found in the basic VFR configuration.
  • Trim systems provide a cyclic centering effect. These systems typically involve a magnetic brake/spring device and may be controlled by a four-way switch on the cyclic. This system requires “hands on” flying of the helicopter.
  • Stability Augmentation Systems (SAS) provide short-term rate damping control inputs to increase helicopter stability. Like trim systems, SAS requires “hands-on” flying.
  • Attitude Retention Systems (ATT) return the helicopter to a selected attitude after a disturbance. Changes in attitude can be accomplished usually through a four- way “beep” switch or by actuating a “force trim” switch on the cyclic, which sets the desired attitude manually. Attitude retention may be a SAS function or may be the basic “hands off” autopilot function.
  • Autopilot Systems (APs) provide for “hands off” flight along specified lateral and vertical paths. The functional modes may include heading, altitude, vertical speed, navigation tracking, and approach. APs typically have a control panel for mode selection and indication of mode status. APs may or may not be installed with an associated FD. APs typically control the helicopter about the roll and pitch axes (cyclic control) but may also include yaw axis (pedal control) and collective control servos.
  • Flight Directors (FDs) provide visual guidance to the pilot to fly selected lateral and vertical modes of operation. The visual guidance is typically provided by a “single cue,” commonly known as a “vee bar,” which provides the indicated attitude to fly and is superimposed on the attitude indicator. Other FDs may use a “two cue” presentation known as a “cross pointer system.” These two presentations only provide attitude information. A third system, known as a “three cue” system, provides information to position the collective as well as attitude (roll and pitch) cues. The collective control cue system identifies and cues the pilot what collective control inputs to use when path errors are produced or when airspeed errors exceed preset values. The three-cue system pitch command provides the required cues to control airspeed when flying an approach with vertical guidance at speeds slower than the best-rate-of-climb (BROC) speed. The pilot manipulates the helicopter’s controls to satisfy these commands, yielding the desired flightpath or may couple the autopilot to the FD to fly along the desired flightpath. Typically, FD mode control and indication are shared with the autopilot. Pilots must be aware of the mode of operation of the augmentation systems and the control logic and functions in use. For example, on an instrument landing system (ILS) approach and using the three-cue mode (lateral, vertical, and collective cues), the FD collective cue responds to glideslope deviation, while the horizontal bar cue of the “crosspointer” responds to airspeed deviations. However, the same system when operated in the two-cue mode on an ILS, the FD horizontal bar cue responds to glideslope deviations. The need to be aware of the FD mode of operation is particularly significant when operating using two pilots.

Pilots should have an established set of procedures and responsibilities for the control of FD/AP modes for the various phases of flight. Not only does a full understanding of the system modes provide for a higher degree of accuracy in control of the helicopter, it is the basis for crew identification of a faulty system.

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Airborne Navigation Databases (Part Five)

Filed Under: Airborne Navigation Databases

Naming Conventions

Obvious differences exist between the names of procedures shown on charts and those that appear on the displays of many RNAV systems. Most of these differences can be accounted for simply by the way the avionics manufacturers elect to display the information to the pilot. It is the avionics manufacturer that creates the interface between the pilot and the database. For example, the VOR 12R approach in San Jose, California, might be displayed several different ways depending on how the manufacturer designs the pilot interface. Some systems display procedure names exactly as they are charted, but many do not.

The naming of multiple approaches of the same type to the same runway is also changing. Multiple approaches with the same guidance will be annotated with an alphabetical suffix beginning at the end of the alphabet and working backwards for subsequent procedures (e.g., ILS Z RWY 28, ILS Y RWY 28, etc.). The existing annotations, such as ILS 2 RWY 28 or Silver ILS RWY 28, will be phased out and replaced with the new designation.

NAVAIDs are also subject to naming discrepancies as well. This problem is complicated by the fact that multiple NAVAIDs can be designated with the same identifier. VOR XYZ may occur several times in a provider’s database, so the avionics manufacturer must design a way to identify these fixes by a more specific means than the three-letter identifier. Selection of geographic region is used in most instances to narrow the pilot’s selection of NAVAIDs with like identifiers.

Non-directional beacons (NDBs) and locator outer markers (LOMs) can be displayed differently than they are charted. When the first airborne navigation databases were being implemented, NDBs were included in the database as waypoints instead of NAVAIDs. This necessitated the use of five character identifiers for NDBs. Eventually, the NDBs were coded into the database as NAVAIDs, but many of the RNAV systems in use today continue to use the fivecharacter identifier. These systems display the characters “NB” after the charted NDB identifier. Therefore, NDB ABC would be displayed as “ABCNB.”

Other systems refer to NDB NAVAIDs using either the NDB’s charted name if it is five or fewer letters, or the one to three character identifier. PENDY NDB located in North Carolina, for instance, is displayed on some systems as“PENDY,”while other systems might only display the NDBs identifier “ACZ.” [Figure 6-31]

Figure 6-31. Manufacturer’s naming conventions.
Figure 6-31. Manufacturer’s naming conventions.

Using the VOR/DME Runway 34 approach at Eugene Mahlon Sweet Airport (KEUG) in Eugene, Oregon, as another example, which is named V34, may be displayed differently by another avionics platform. For example, a GPS produced by one manufacturer might display the approach as VOR 34, whereas another might refer to the approach as VOR/DME 34, and an FMS produced by another manufacturer may refer to it as VOR34. These differences can cause visual inconsistencies between chart and GPS displays, as well as confusion with approach clearances and other ATC instructions for pilots unfamiliar with specific manufacturer’s naming conventions.

For detailed operational guidance, refer to Advisory Circular (AC) 90-100, U.S. Terminal and En Route Area Navigation (RNAV) Operations; AC 90-101, Approval Guidance for Required Navigation Performance (RNP) Procedures with Authorization Required (AR); AC 90-105, Approval guidance for RNP Operations and Barometic Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace; and AC 90-107, Guidance for Localizer Performance with Vertical Guidance and Localizer Performance without Vertical Guidance Approach Operations in the U.S. National Airspace System.

 

Issues Related To Magnetic Variation

Magnetic variations for locations coded into airborne navigation databases can be acquired in several ways. In many cases they are supplied by government agencies in the epoch year variation format. Theoretically, this value is determined by government sources and published for public use every five years. Providers of airborne navigation databases do not use annual drift values; instead the database uses the epoch year variation until it is updated by the appropriate source provider. In the United States, this is the National Oceanic and Atmospheric Administration (NOAA). In some cases the variation for a given location is a value that has been calculated by the avionics system. These dynamic magnetic variation values can be different than those used for locations during aeronautical charting and must not be used for conventional NAVAIDs or airports.

Discrepancies can occur for many reasons. Even when the variation values from the database are used, the resulting calculated course might be different from the course depicted on the charts. Using the magnetic variation for the region instead of the actual station declination can result in differences between charted and calculated courses and incorrect ground track. Station declination is only updated when a NAVAID is site checked by the governing authority that controls it, so it is often different than the current magnetic variation for that location. Using an onboard means of determining variation usually entails coding some sort of earth model into the avionics memory. Since magnetic variation for a given location changes predictably over time, this model may only be correct for one time in the lifecycle of the avionics. This means that if the intended lifecycle of a GPS unit were 20 years, the point at which the variation model might be correct would be when the GPS unit was 10 years old. The discrepancy would be greatest when the unit was new, and again near the end of its life span.

Another issue that can cause slight differences between charted course values and those in the database occurs when a terminal procedure is coded using magnetic variation of record. When approaches or other procedures are designed, the designers use specific rules to apply variation to a given procedure. Some controlling government agencies may elect to use the epoch year variation of an airport to define entire procedures at that airport. This may result in course discrepancies between the charted value and the value calculated using the actual variations from the database.

Issues Related To Revision Cycle

Pilots should be aware that the length of the airborne navigation database revision cycle could cause discrepancies between aeronautical charts and information derived from the database. One important difference between aeronautical charts and databases is the length of cutoff time. Cutoff refers to the length of time between the last day that changes can be made in the revision, and the date the information becomes effective. Aeronautical charts typically have a cutoff date of 10 days prior to the effective date of the charts.

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Airborne Navigation Databases (Part Four)

Filed Under: Airborne Navigation Databases

Operational Limitations of Airborne Navigation Databases

Understanding the capabilities and limitations of the navigation systems installed in an aircraft is one of the pilot’s biggest concerns for IFR flight. Considering the vast number of RNAV systems and pilot interfaces available today, it is critical that pilots and flight crews be familiar with the manufacturer’s operating manual for each RNAV system they operate and achieve and retain proficiency operating those systems in the IFR environment.

Most professional and general aviation pilots are familiar with the possible human factors issues related to flightdeck automation. It is particularly important to consider those issues when using airborne navigation databases. Although modern avionics can provide precise guidance throughout all phases of flight, including complex departures and arrivals, not all systems have the same capabilities.

RNAV equipment installed in some aircraft is limited to direct route point-to-point navigation. Therefore, it is very important for pilots to familiarize themselves with the capabilities of their systems through review of the manufacturer documentation. Most modern RNAV systems are contained within an integrated avionics system that receives input from several different navigation and aircraft system sensors. These integrated systems provide so much information that pilots may sometimes fail to recognize errors in navigation caused by database discrepancies or misuse. Pilots must constantly ensure that the data they enter into their avionics is accurate and current. Once the transition to RNAV is made during a flight, pilots and flight crews must always be capable and ready to revert to conventional means of navigation if problems arise.

Closed Indefinitely Airports

Some U.S. airports have been closed for up to several years, with little or no chance that they will ever reopen; yet their “indefinite” closure status – as opposed to permanent or UFN closure, or abandonment – causes them to continue to appear on both VFR and IFR charts and in airborne navigation databases; and their instrument approach procedures, if any, continue to be included – and still appear to be valid – in the paper and electronic versions of the United States Terminal Procedures Publication (TPP) charts. Airpark South, 2K2, at Ozark, Missouri, is a case in point.

Even though this airport has been closed going on two years and, due to industrial and residential development surrounding it, likely will never be reopened, the airport is nonetheless still charted in a way that could easily lead a pilot to believe that it is still open and operating. Even the current U.S. Low Altitude En route chart displays a blue symbol for this airport, indicating that it still has a Department of Defense (DOD) approved instrument approach procedure available for use.

Aircrews need to use caution when selecting an airport in a cautionary or emergency situation, especially if the airport was not previously analyzed suitable for diversion during preflight. Aircrews could assume, based on charts and their FMS database, the airport is suitable and perhaps the only available diversionary or emergency option. The airport however, could be closed and hazardous even for emergency use. In these situations, Air Traffic Control may be queried for the airport’s status.

 

Storage Limitations

As the data in a worldwide database grows, the required data storage space increases. Over the years that panel- mounted GPS and FMSs have developed, the size of the commercially available airborne navigation databases has grown exponentially.

Some manufacturer’s systems have kept up with this growth and some have not. Many of the limitations of older RNAV systems are a direct result of limited data storage capacity. For this reason, avionics manufacturers must make decisions regarding which types of procedures will be included with their system. For instance, older GPS units rarely include all of the waypoints that are coded into master databases. Even some modern FMS equipment, which typically have much larger storage capacity, do not include all of the data that is available from the database producers. The manufacturers often choose not to include certain types of data that they think is of low importance to the usability of the unit. For example, manufacturers of FMS used in large airplanes may elect not to include airports where the longest runway is less than 3,000 feet or to include all the procedures for an airport.

Manufacturers of RNAV equipment can reduce the size of the data storage required in their avionics by limiting the geographic area the database covers. Like paper charts, the amount of data that needs to be carried with the aircraft is directly related to the size of the coverage area. Depending on the data storage that is available, this means that the larger the required coverage area, the less detailed the database can be.

Again, due to the wide range of possible storage capacities, and the number of different manufacturers and product lines, the manufacturer’s documentation is the pilot’s best source of information regarding limitations caused by storage capacity of RNAV avionics.

Charting/Database Inconsistencies

It is important for pilots to remember that many inconsistencies may exist between aeronautical charts and airborne navigation databases. Since there are so many sources of information included in the production of these materials, and the data is manipulated by several different organizations before it is eventually displayed on RNAV equipment, the possibility is high that there will be noticeable differences between the charts and the databases. Because of this, pilots must be familiar with the capabilities of the database and have updated aeronautical charts while flying to ensure the proper course is being flown.

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