fuel quantity indication, and caution/warning parameters, as a minimum, presented by a common display driven by a common processor.
(4) Discussion. This design philosophy does not result in the traditional requirement for individual display independence for failure/malfunction considerations.
This loss of independence means that a single failure could result in loss of most, if not all, instrument displays on the integrated display system. Redundancy of the integrated display system is often proposed to compensate for this lack of independence.
However, redundancy alone may not meet the integrity requirements since they are derived from the level of criticality associated with the loss or malfunction of instrument/parameter displays for flight operations that are dependent on these indications.
(5) Certification Approach. A two step procedure should be used to determine the adequate safety level for this type of system. The first step is to determine the level of criticality associated with the total loss/malfunction of these functions/indications or loss/malfunction of the critical parts of the display. This can be achieved through the use of a functional hazard assessment (FHA). This criticality assessment must be a product of failure/malfunction of the indication system and the flight operation that would represent the worst case for loss of this information. The second step is to determine that the design integrity of the system is at least equal to the assessed criticality level determined in step one.
(6) Functional Hazard Assessment.
Summary The operational classifications to be considered when assessing the criticality are Cat A, Cat B, and IFR. The need for critical information varies with each of these different operational categories. An example would be the demand for OEI parameter information in the single engine Cat A operation. Another example is the loss of fuel quantity indication and fuel low level indication simultaneously in IFR flight conditions. The FHA should address not onl y loss of one type of indication, but combined loss of engine parameter indication, including total loss of display information, caution/warning, fuel quantity indication, and any other included display in combination with a particular flight operation. There are techniques to lessen the consequences of the failure/malfunction requirements for integrity, such as providing back-up displays for the information deemed critical for a particular operational consideration.
(7) . The loss of all integrated display information for certain types of flight operations may have the highest level of criticality associated with it. The same may be true for malfunctions that result in misleading indications. These failures/malfunctions must be addressed by the commensurate design integrity level.
Lesser levels of criticality must also be addressed by the appropriate design integrity levels.
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AC 29-2C, Chg 4 5/1/2014 AC 29.1305C. § 29.1305 (Amendment 29- 40) POWERPLANT INSTRUMENTS.
a. Explanation Procedures . Amendm ent 29-40 added section 29.1305(a)(6) to require an oil pressure indicator for each pressure-lubricated gearbox. Paragraphs (a)(6) through
(a)(25), prior to this amendment, have been redesignated as paragraphs (a)(7) through
(a)(26).
b. . I n addition to providing an oil pressure indicator for each pressure-lubricated gearbox, the guidance material of the previous AC 29.1305 paragraphs continues to apply.
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AC 29.1305D. § 29.1305 (AMENDMENT 29-59) POWERPLANT INSTRUMENTS.
a. Explanation. Amendment 29-59 revised § 29.1305 to include the use of technology such as a synthesized power indicator (SPI), and added § 29.1305(b)(4) to address One Engine Inoperative (OEI) Training Mode.
(1) Revised §§ 29.1305(a)(5), (a)(11), and (a)(12) to incorporate flexibility for the use of a synthesized power indicator (SPI).
(2) Added § 29.1305(b)(4) to provide a requirement for when an applicant requests approval for OEI Training Mode. OEI Training Mode is intended to simulate an engine failure, provide an annunciation of that simulation, and indicate the actual power being provided by the engines to the flight crew.
b. Procedures. The purpose of the SPI display is to reduce pilot workload by providing an indicator showing a single parameter that is closest to the applicable engine or transmission limit, versus monitoring individual engine parameters. The SPI display for reciprocating engines presents a normalized indication of the current engine manifold pressure and engine RPM. For turbine engines, the SPI display presents normalized indications of the engine power or torque, gas temperature, and engine compressor speed output. The normalized value is presented to the flight crew on the primary flight displays, along with a caption indicating the nearest engine limiting parameter (engine manifold pressure, RPM, torque, gas temperature indicator, engine compressor speed, as applicable) that is being used for the SPI display calculation.
The SPI display function is typically performed by the avionics suite using data provided by the engine FADEC.
Section 29.1305 establishes the required powerplant instruments and warning and caution annunciations that must be displayed within the view of the flying pilot. These have traditionally been independent instruments and are needed not only to measure the performance output of the engines, but they collectively allow the flying pilot to continuously monitor the condition and health of the engines.
The absence of continuously displayed engine manifold pressure and RPM for reciprocating engines or engine torque, gas temperature, and engine compressor speed parameters may affect the pilot’s ability to directly monitor the health and condition of each engine. In addition, the absence of individual gauges deprives the pilot of the ability to quickly assess trend or rate of change information and proximity to individual parameter limits, and to accurately compare engine-to-engine data. As a result, in addition to the requirements in §§ 29.1305 and 29.1549, the SPI display must also meet the requirements of § 29.1321.
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The applicant’s description and justification of the SPI display should address the following:
(1) The accuracy of the engine power and other engine indications to safely conduct Category B and, when applicable, Category A operations (power setting, NR control, piloting a given rating with precision).
(2) The flight crew must be able to assess how close the indicated parameter is relative to the limit, including the transitions from one limiting factor to another (engine manifold pressure to engine RPM or engine torque to gas temperature indicator to engine compressor speed), and the ability to quickly and accurately compare engine-toengine data when engine limiting factors are different (Engine 1 Torque, Engine 2 Gas Temperature Indicator). See §§ 29.1321 and 29.1549.
(3) Engine design features or characteristics that forewarn the crew prior to the parameter reaching the operating limit (the redline) should be evaluated.
(4) The SPI display must provide a timing countdown when operating with time limited power settings and as required by § 29.1305(a)(25).
(5) The minimum and maximum operating limits must be marked as required by § 29.1549.
(6) The SPI display should allow the pilot to identify indicator failures, engine failures, partial power loss conditions, and adverse trends, to meet the requirements in §§ 29.771(a), 29.1309, 29.1321, and 29.1549. The SPI design should also address all normal and abnormal operations including start/shutdown and OEI conditions per § 29.771(a).
(7) Since the SPI is a system comprised of instruments requirement by subchapter C of Title 14, its hazards are among those that must assessed under the requirements of § 29.1309. When conducting this assessment, to meet the requirements in § 29.1301, the applicant must take into account that the crew will operate the rotorcraft, monitoring the engine status and health, without continuously accessing the powerplant display page. In addition, the assessment should assume the SPI will remain the only engine instrument available in case of loss of one display.
For guidance on § 29.1305(b)(4) OEI training mode, see Miscellaneous Guidance 22 (MG 22).
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AC 29-2C, Chg 4 5/1/2014 AC 29.1307. § 29.1307 (Amendment 29-1 2) MISCELLANEOUS EQUIPMENT.
a. Explanation. Thi s rule provides a listing of several items of required miscellaneous equipment. Each item is self-explanatory, except for the one requiring a master switch arrangement for electrical circuits other than ignition. The purpose of a master switch arrangement is to allow rapid removal of all bus loads from sources of electrical power in an emergency situation. Requirements for radio communications are discussed more in AC 29.1431.
b. Procedures. When reviewing possible solutions to the master switch arrangement requirement, the following considerations should be included.
(1) Installation o f switches System separation. Since wiring from each electrical system will be brought in close proximity to each other, extra care should be taken to maintain some separation. As examples, common connectors, common grounds, and common wire routing should be avoided.
(2) . The single switch should be avoided since it introduces the possibility of a single failure turning off the entire electrical system. One solution that is commonly used provides a close grouping of the switches such that the pilot can easily reach all switches and turn them all off with one action. This solution requires a cockpit evaluation to ensure the installation will be suitable for different hand sizes. Another solution involves a gang bar that can be moved with a single motion to turn off all sources. This solution has been found to be acceptable in several instances.
Other solutions should be evaluated on their own merits, and the primary emphasis should be on maintaining some minimum system separation and conducting a cockpit evaluation by flight test personnel.
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AC 29.1309. § 29.1309 (Amendment 29-40) EQUIPMENT, SYSTEMS, AND INSTALLATIONS.
a. Explanation.
(1) Applicability. Section 29.1309 of the Title 14 CFR regulations is intended as a general requirement that is applicable to any equipment or system as installed, in addition to specific systems requirements, except as indicated below.
(i) General. If a specific part 29 requirement exists which predefines systems safety aspects (e.g., redundancy level or criticality) for a specific type of equipment, system, or installation, then the specific part 29 requirement will take precedence (see section 29.1301b.(2) of this AC). This precedence does not preclude accomplishment of a system safety assessment, if necessary. For example, § 29.695 is a rule that predefines a required level of redundancy and an implied system reliability. However, a system safety assessment approach may still be required to show that the implied system reliability is met and to address assessment of the failure modes.
(ii) . Section 29.1309 does not apply to Subparts B, C, and D for aspects such as the performance, flight characteristics, structural loads Section 29, Subparts B, C, and D , and structural strength requirements. However, it does apply to any equipment and system on which compliance with the requirements of Subparts B, C, and D is based (e.g., Health Usage Monitoring System certified for maintenance credit and Stability Augmentation System).
(iii) Section 29, Subpart E.
(A) Section 29.1309 does not apply to the uninstalled type-certificated engine. However, it does apply to the equipment and systems associated with the engine installation (e.g., electrical power generation, engine displays, transducers, etc.)
on the rotorcraft (reference § 29.901).
(B) Section 29.1309 does not apply to the Rotor Drive Systems (reference § 29.917(b)).
(iv) Section 29, Subpart F.
(A) Section 29.1309 does not apply to stowed safety equipment such as life rafts, life preservers, and emergency floatation equipment. It also does not apply to safety belts, rotorcraft seats, and hand held fire extinguishers. However, it does apply to hazards to the rotorcraft, its occupants, and flight crew introduced by the installation or presence of this type of equipment or system (e.g., Electromagnetic-Interference considerations, fire hazards, and inadvertent deployment of emergency floatation equipment) approved as part of the type design.
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AC 29-2C, Chg 4 5/1/2014 (B) Section 29.1309 does not apply to the functional aspects of aircraft non-safety related equipment such as entertainment systems, hoists, Forward Looking Infrared systems (FLIR), or emergency medical equipment such as defibrillators, etc.
However, it does apply to hazards to the rotorcraft, its occupants, and flight crew introduced by the installation or presence of this type of equipment or system (e.g., Electromagnetic-Interference considerations, fire hazards, and failure of the electrical system fault protection scheme) approved as part of the type design.
(C) Section 29.1309 does not apply to the lighting characteristics (e.g., light intensity, color, and coverage) of the position lights, anti-collision lights, and riding lights. However, it does apply to hazards to the rotorcraft, its occupants, and flight crew introduced by the installation or presence of this type of equipment or system (e.g., Electromagnetic-Interference considerations, fire hazards, and pilot visibility impairment due to glare) approved as part of the type design.
(2) Background.
(i) This guidance is not intended to change the existing reliability requirements of the current §§ 29.1309(b) and (c). Neither is this guidance intended to impose an overly rigorous safety assessment process for those installations involving equipment or systems that are not considered to be complex or do not perform functions whose failure or malfunction result in higher level failure condition categories.
(ii) However, this section does provide guidance that describes a method of showing compliance that utilizes the latest system safety assessment techniques available in the aerospace industry. The safety assessment process described in this guidance can be easily adopted and applied with various degrees to equipment or systems, and installations ranging from simple systems that perform functions whose failure or malfunction have no safety impact, to the most critical and most complex systems.
b. Procedures.
(1) Definitions of Probability Classifications.
(i) FREQUENT. (This is the lower part of the range 10-5 or greater previously applied to the term “PROBABLE”.) Frequent events may be expected to occur often during the operational life of each rotorcraft that are based on a probability on the order of 10-3 or greater.
(ii) REASONABLY PROBABLE. (This is the upper part of the range 10 or greater previously applied to the term “PROBABLE”.) Reasonably probable even -5 -3 to 10 .
ts may be expected to occur several times during the operational life of each rotorcraft that are based on a probability on the order of between 10 -5 Page F - 14
(iii) REMOTE. (The term “REMOTE” is not related to the structural use of the term.) (This is the lower part of the range 10 -9 to 10-5 previously applied to the term “IMPROBABLE”.) Remote events are expected to occur a few times during the total operational life of a random single rotorcraft of a particular type, but may occur several times during the total operational life of a number of rotorcraft of a particular type, that are based on a probability on the order of between 10-5 to 10-7 .
(iv) EXTREMELY REMOTE -9 -5 -7 to 10 .
(v) EX
TREMELY IMPROBABLE -9 or less is assigned to this classification.
(2) Definitions of Failure Condition Classifications
NO EFFECT MINOR . (T he term “REMOTE” is not related to the structural use of the term.) (This is the upper part of the range 10 to 10 previously applied to the term “IMPROBABLE”.) Extremely remote events are not expected to occur during the total operational life of a random single rotorcraft of a particular type, but may occur a few times during the total operational life of all rotorcraft of a particular type, that are based on a probability on the order of between 10 -9 . ( Remains the same for both the three or the five classifications.) Extremely improbable events are so unlikely that they need not be considered to ever occur, unless engineering judgment would require their consideration. A probability on the order of 10 Note: The five probability terms defined in paragraph b.(1) above are intended to relate to an identified failure condition resulting from or contributed to by the improper operation or loss of a function or functions. These terms do not define the reliability of specific components or systems.
. Failure Conditions may be classified according to the severity of their effects into one of the following categories (reference Figure AC 29.1309-2).
(i) . Failure Conditions that would have no effect on safety; for example, Failure Conditions that would not affect the operational capability of the rotorcraft or increase crew workload, however, could result in an inconvenience to the occupants, excluding the flight crew.
(ii) . Failure conditions which would not significantly reduce rotorcraft safety, and which would involve crew actions that are well within their capabilities.
Minor failure conditions may include, for example, a slight reduction in safety margins or functional capabilities, a slight increase in crew workload, such as, routine flight plan changes, or some physical discomfort to occupants.
(iii) MAJOR. Failure conditions which would reduce the capability of the rotorcraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be, for example, a significant reduction in safety margins or functional capabilities, a significant increase in crew work load or in conditions impairing crew efficiency, physical distress to occupants, possibly including injuries, or physical discomfort to the flight crew.
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AC 29-2C, Chg 4 5/1/2014
(iv) HAZARDOUS or SEVERE-MAJOR. Failure conditions which would reduce the capability of the rotorcraft or the ability of the crew to cope with adverse operating conditions to the extent that there would be:
(A) A large reduction in safety margins or functional capabilities;
(B) Physical distress or excessive workload such that the flight crew’s ability is impaired to where they could not be relied on to perform their tasks accurately or completely; or, (C) Possible serious or fatal injury to a passenger or a cabin crew member, excluding the flight crew.
Note: Hazardous or Severe-Major failure conditions can include events that are manageable by the crew by use of proper procedures which, if not implemented correctly or in a timely manner, may result in a Catastrophic Event.
(v) CATASTROPHIC. Failure Conditions which would result in multiple fatalities to occupants, fatalities or incapacitation to the flight crew, or result in loss of rotorcraft.
(3) Safety Objective.
(i) The objective of § 29.1309 is to ensure an acceptable safety level for equipment and systems as installed on the rotorcraft. A logical and acceptable inverse relationship must exist between the Average Probability per Flight Hour and the severity of Failure Condition effects, as shown in Figure AC 29.1309-1, such that:
(A) Failure Conditions with No Effect on safety may be more frequent than Reasonably Probable.
(B) Minor Failure Conditions may be Reasonably Probable.
(C) Major Failure Conditions must be no more frequent than Remote.
(D) Hazardous or Severe-Major Failure Conditions must be no more frequent than Extremely Remote.
(E) Catastrophic Failure Conditions must be Extremely Improbable.
(ii) The safety objectives associated with Failure Conditions are described in Figure AC 29.1309-2, and appear in Figure AC 29.1309-1, below.
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Probability of Failure Condition Probable Remote Extremely Remote Extremely Improbable Unacceptable Acceptable Minor Major Hazardous Catastrophic Severity of Failure Condition Elfects 5/1/2014 AC 29-2C, Chg 4 FIGURE AC 29.1309-1 Relationship between Probability and Severity of Failure Condition Effects
(iii) The safety objectives associated with Catastrophic Failure Conditions, may be satisfied by demonstrating that:
(A) No single failure will result in a Catastrophic Failure Condition; and (B) Each Catastrophic Failure Condition is Extremely Improbable.
(iv) Failure conditions may be classified according to the severity of their effects to the rotorcraft, occupants, or flight crew as identified in the following Figure AC 29.1309-2.
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AC 29-2C, Chg 4 5/1/2014 Table for Failure Condition Categories and Probability Definitions Effect on rotorcraft No effect on operational capabilities or safety Slight reduction in functional capabilities or safety margins Significant reduction in functional capabilities or safety margin Large reduction in functional capabilities or safety margins (Note 4) Loss of rotorcraft Effect on occupants excluding flight crew Inconvenience Physical discomfort Physical distress, possibly including injuries Serious or fatal injury to a passenger or a cabin crew member (NOTE 2) Multiple Fatalities Effect on flight crew No effect on flight crew Slight increase in work load which involve crew actions well within crew capabilities such as routine flight plan changes Physical discomfort or a significant increase in workload or in conditions impairing crew efficiency Physical distress or excessive workload impairs ability to perform tasks accurately or completely Fatalities or incapacitation DO-178C Software Level (Note 3)
E D C B A Failure Condition Category No Effect Minor Major Hazardous or Severe-Major Catastrophic Qualitative Probability Frequent Reasonably Probable Remote Extremely Remote Extremely Improbable Quantitative Probability :
No probability requirement ≤10-3 (Note 1) ≤10-5 ≤10-7 ≤10-9 Note 1: A numerical probability range is provided here as reference. The applicant is not required to perform a quantitative analysis, or substantiate by such an analysis, that this numerical criterion has been met for Minor Failure Conditions.
Note 2: This is true if it can be shown that the given failure condition can be contained to a fatal injury of one occupant only.
Note 3: This is not intended to imply that the identified software levels are assigned a probability value, but instead, shows a correlation to the Failure Condition Category.
Note 4: Hazardous or Severe-Major failure conditions can include events that are manageable by the crew by use of proper procedures which, if not implemented correctly or in a timely manner, may result in a Catastrophic event.
FIGURE AC 29.1309-2 Failure Condition Categories and Probability Definitions
(v) The following Figure AC 29.1309-3 provides conversion between the current application of the five failure condition categories as defined in Figure AC 29.1309-2 and the three failure condition categories contained in the present rules.
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Present Rule Qualitative Probability Classification -------- Probable -------- ----------Improbable--------- Extremely Improbable Quantitative Probability Classification >10-5 <10-5 <10-9 Present Rule Failure Condition Category – AC 29 2C & DO-178A Non-essential Essential Critical Current Application of Failure Condition Category No Effect Minor Major Hazardous or Severe - Major Catastrophic FIGURE AC 29.1309-3: Failure Condition Conversion
(4) Safety Assessment Process Overview.
(i) When showing compliance with § 29.1309, the considerations covered in this guidance should be addressed in a methodical and systematic manner, which ensures that the process and its findings are visible, and readily assimilated. This section of the AC (Safety Assessment Process Overview) is provided primarily for the use of applicants who are not familiar with the various methods and procedures generally used in the industry to conduct safety assessments. This guide and Figures AC 29.1309-4 and AC 29.1309-5 are not intended to be certification checklists, and they do not include all the information provided in this guidance. This guide is one method but not the only method for showing compliance. The safety assessmen t process is a structured method of general applicability for showing compliance with the regulation.
Other methodologies may be used to show compliance, but the safety assessment process is the only structured process that is defined and these defined objectives would be the logical criteria applied to any other means of showing compliance. More detailed guidance can be found in SAE Document ARP 4761 on how to perform a safety assessment. SAE Document ARP 4754A, invoked by AC 20-174, includes additional guidance on how the safety assessment process relates to the system development process.
(ii) The safety assessment process contains several parts that may be necessary as a whole or part depending on the criticality or complexity of the system under consideration. The rigor of assessment and analysis performed is also dependent on the system criticality or complexity. At the extremes, some systems may be simple enough such that the entire safety assessment can be performed by observation and compliance shown by a simple statement. Complex and higher criticality systems may require application of all the safety assessment elements to show compliance. Many states of varying complexity exist between these extremes that Page F - 19