FIGURE AC 27.MG 11-8
LIFTING HELICOPTER LOAD MEASUREMENT in addition to normal conditions CONDITION %RATED LOAD % VNE
ROTOR START VERTICAL LIFT 100 87 HOVER including spot turns sideward and rearward flight and control reversal.
100 87 CRUISE with load 100 100 87 100 100 90 87 90 CRUISE no load 100 90 CLIMB max. rate DECELERATIONS max. rate
GROUND IDLE
SHUTDOWN AC Page MG 11 - 23
AC 27-1B, Chg 1 2/12/03 FIGURE AC 27.MG 11-9. EXAMPLE OF TWIN TURBINE USAGE SPECTRUM Notes:
1. Altitude, temperature, center of gravity, and weight variations may be appropriate where justified by service data; otherwise the worst case must be assumed throughout.
2. This spectrum is an example only; all probable types of operation must be accounted for unless prohibited--see Section 3.
CONDITION % of time Nb per hour ON GROUND inc START UP 3.5 5 TAXIING 3.5 APPROACH 5 2 NORMAL 3.5 UNDER HEAVY SLOPE 0.75 FLARE 0.375 1 QUICK-STOP 0.375 1 Dur. 14 (s) SPOT-TURN 1 5 30°/S/NORM (STOP)/RIGHT 0.32 1.6 Yaw speed rep.
80.00% 30°
15.00% 45°
5.00% max Stop rep.
80.00% normal
20.00% max 30°/S/NORM (STOP)/LEFT 0.32 1.6 30°/S/MAX (STOP)/RIGHT 0.08 0.4 30°/S/MAX (STOP)/LEFT 0.08 0.4 45°/S/NORM (STOP)/RIGHT 0.06 0.3 45°/S/NORM (STOP)/LEFT 0.06 0.3 45°/S/MAX (STOP)/RIGHT 0.015 0.075 45°/S/MAX (STOP)/LEFT 0.015 0.075 MAX/NORM (STOP)/RIGHT 0.02 0.1 MAX/NORM(STOP)/LEFT 0.02 0.1 MAX/MAX (STOP)/RIGHT 0.005 0.025 MAX/MAX (STOP)/LEFT 0.005 0.025 Dur. 7.2 (s) LANDING 1.5 5 NORMAL 1.482 5.94 1/20 hours slope 8° 1/100 hours slope 10° ON SLOPE/8DEG/RIGHT 0.0043 0.0145 ON SLOPE/8DEG/LEFT 0.0043 0.0145 8DEG/NOSE-UP 0.0038 0.0125 8DEG/NOVE-DOWN 0.0043 0.0145 ON SLOPE/10DEG/NOSE-UP 0.0006 0.002 COMB.SLOPE 0.0006 0.002 Dur. 11 (s) AUTOROTATION 1 1 Speed rep.
5.00% 70Kts
20.00% 70Kts
30.00% 70Kts
25.00% 120Kts
15.00% 135Kts
5.00% VNE RPM rep.
10.00% Mini
50.00% Nomi
36.00% Maxi
4.00% Maxi.trans VERTICAL 0.05 0.05 40 KTS 0.2 0.2 70 KTS 0.3 0.3 120 KTS 0.25 0.25 135 KTS 0.15 0.15 VNE 0.05 0.05 Dur. 36 (s) TAKE OFF 1.5 5 Dur. 11 (s) NORMAL 0.8892 2.964 60.00% Normal
40.00% Quick 1/20 hours slope 8° 1/100 hours slope 10° QUICK 0.5928 1.976 ON SLOPE/8DEG/RIGHT 0.0043 0.0145 ON SLOPE/8DEG/LEFT 0.0043 0.0145 ON SLOPE/8DEG/NOSE-UP 0.0038 0.0125 ON SLOPE/8DEG/NOVE-DOWN 0.0043 0.0145 ON SLOPE/10DEG/NOSE-UP 0.0006 0.002 COMB.SLOPE 0.0006 0.002 DESCENT 1.5 2 PARTIAL POWER/STD/STD 0.96 1.28 Speed rep.
80.00% Partial power
20.00% VNE Side slip PP values rep.
60.00% 5°
30.00% 10°
8.00% 15°
2.00% 20° PARTIAL POWER/5 DEG/RIGHT 0.072 0.096 PARTIAL POWER/5 DEG/LEFT 0.072 0.096 PARTIAL POWER/10 DEG/RIGHT 0.036 0.048 PARTIAL POWER/10 DEG/LEFT 0.036 0.048 Side slip rep.
80.00% Without
20.00% with PARTIAL POWER/15 DEG/RIGHT 0.0096 0.0128 PARTIAL POWER/15 DEG/LEFT 0.0096 0.0128 Side slip VNE values rep.
90.00% 5°
10.00% 10° PARTIAL POWER/20 DEG/RIGHT 0.0024 0.0032 PARTIAL POWER/20 DEG/LEFT 0.0024 0.0032 VNE AT MCP/STD/STD 0.24 0.32 VNE AT MCP/5 DEG/RIGHT 0.027 0.036 VNE AT MCP/5 DEG/LEFT 0.027 0.036 VNE AT MCP/10 DEG/RIGHT 0.003 0.004 VNE AT MCP/10 DEG/LEFT 0.003 0.004 Page MG 11 - 24
FIGURE AC 27.MG 11-9. EXAMPLE OF TWIN TURBINE USAGE SPECTRUM (continued) CONDITION % of time Nb per hour CLIMB 3 4 MCP 75 KTS/STD/STD 1.8 2.4 Climb rep.
75.00% 75 Kts
25.00% Vertical Side slip values rep.
80.00% 05 10
18.00% 15 20
2.00% 25 30 MCP 75 KTS/05-10 DEG/RIGHT 0.18 0.24 MCP 75 KTS/05-10 DEG/LEFT 0.18 0.24 MCP 75 KTS/15-20 DEG/RIGHT 0.0405 0.054 MCP 75 KTS/15-20 DEG/LEFT 0.0405 0.054 MCP 75 KTS/25-30 DEG/RIGHT 0.0045 0.006 Side slip rep.
80.00% Without
20.00% with MCP 75 KTS/25-30 DEG/LEFT 0.0045 0.006 TOP/VERTICAL 0.75 1 Dur. 27 (s) LEVEL FLIGHT 56.5 80% MCP/STD/STD 12.4 Speed rep.
28.3% 80% MCP
36.3% 90% MCP
35.4% MCP Side slip rep.
80.00% Without
20.00% with 80% MCP/5 DEG/RIGHT 1.08 80% MCP/5 DEG/LEFT 1.08 80% MCP/10 DEG/RIGHT 0.54 80% MCP/10 DEG/LEFT 0.54 80% MCP/15 DEG/RIGHT 0.144 80% MCP/15 DEG/LEFT 0.144 Side slip typ rep.
60.00% 5°
30.00% 10°
8.00% 15°
2.00% 20° 80% MCP/20 DEG/RIGHT 0.036 80% MCP/20 DEG/LEFT 0.036 90% MCP/STD/STD 16.3 90% MCP/5 DEG/RIGHT 1.26 90% MCP/5 DEG/LEFT 1.26 90% MCP/10 DEG/RIGHT 0.63 90% MCP/10 DEG/LEFT 0.63 90% MCP/15 DEG/RIGHT 0.21 90% MCP/15 DEG/LEFT 0.21 MCP/STD/STD 17 MCP/5 DEG/RIGHT 0.9 MCP/5 DEG/LEFT 0.9 MCP/10 DEG/RIGHT 0.45 MCP/10 DEG/LEFT 0.45 MCP/15 DEG/RIGHT 0.15 MCP/15 DEG/LEFT 0.15 PULL-UP 0.22 1.1 PULL-UP/VNE 0.01 0.05 PULL-UP/LEVEL FLIGHT 80%MCP 0.1 0.5 PULL-UP/LEVEL FLIGHT 90%MCP 0.1 0.5 PULL-UP/AUTOROTATION 0.01 0.05 Dur. 7.2 (s) HOVERING 10 10 HOVERING/IGE 9 9 HOVERING/OGE 1 1 Dur. 36 (s) TRANSITION 4.52 19.6 TRANSITION/CLIMB TO VMAX 0.292 5 TRANSITION/90%MCP TO V.DESC(ISO-V) 0.292 5 TRANSITION/LEVEL.F TO AUTO.(65 KTS) 0.292 0.5 TRANSITION/FORW.F AFTER REAR.F 0.06 0.1 TRANSITION/HOVERING TO FWD FLIGHT 3 5 Dur. 22 (s) TRANSITION/PITCH INCREASE(65 KTS) 0.292 2 TRANSITION/PITCH DECREASE(65 KTS) 0.292 2 Dur. 3.6 (s) AC Page MG 11 - 25
AC 27-1B, FIGUR TURNS TURNS/60% MCP/ Chg 1 2/12/03 E AC 27.MG 11-9. EXAMPLE OF TWIN TURBINE USAGE SPECTRUM (continued) CONDITION % of time Nb per hour 8 30 NZ 1.2G/RIGHT 0.2667 1 Speed rep. Nz rep TURNS/60% MCP/NZ 1.2G/LEFT 0.2667 1 10.00% 60% MCP 10 >1.2g TURNS/60% MCP/NZ 1.4G/RIGHT 0.0989 0.3709 30.00% 80% MCP 20 1.2g TURNS/60% MCP/NZ 1.4G/LEFT 0.0989 0.3709 35.00% 90% MCP TURNS/60% MCP/NZ 1.6G/RIGHT 0.0330 0.1237 25.00% MCP TURNS/60% MCP/NZ 1.6G/LEFT 0.0330 0.1237 TURNS/60% MCP/NZ 1.8G/RIGHT 0.0013 0.005 Nb per hour TURNS/60% MCP/NZ 1.8G/LEFT 0.0013 0.005 20 1.2g 1.4/1.6g rep.
TURNS/60% MCP/V.LIM +0.1G/RIGHT 0.00013 0.0005 7.4175 1.4g 75.00% 1.4g TURNS/60% MCP/V.LIM +0.1G/LEFT 0.00013 0.0005 2.4725 1.6g 25.00% 1.6g TURNS/80% MCP/NZ 1.2G/RIGHT 0.8 3 0.1 1.8g TURNS/80% MCP/NZ 1.2G/LEFT 0.8 3 0.01 V.lim+0.1G TURNS/80% MCP/NZ 1.4G/RIGHT 0.2967 1.1126 TURNS/80% MCP/NZ 1.4G/LEFT 0.2967 1.1126 TURNS/80% MCP/NZ 1.6G/RIGHT 0.0989 0.3709 TURNS/80% MCP/NZ 1.6G/LEFT 0.0989 0.3709 TURNS/80% MCP/NZ 1.8G/RIGHT 0.004 0.015 TURNS/80% MCP/NZ 1.8G/LEFT 0.004 0.015 TURNS/80% MCP/V.LIM +0.1G/RIGHT 0.0004 0.0015 TURNS/80% MCP/V.LIM +0.1G/LEFT 0.0004 0.0015 TURNS/90% MCP/NZ 1.2G/RIGHT 0.9333 3.5 TURNS/90% MCP/NZ 1.2G/LEFT 0.9333 3.5 TURNS/90% MCP/NZ 1.4G/RIGHT 0.3461 1.298 TURNS/90% MCP/NZ 1.4G/LEFT 0.3461 1.298 TURNS/90% MCP/NZ 1.6G/RIGHT 0.1154 0.4327 TURNS/90% MCP/NZ 1.6G/LEFT 0.1154 0.4327 TURNS/90% MCP/NZ 1.8G/RIGHT 0.0046 0.0175 TURNS/90% MCP/NZ 1.8G/LEFT 0.0046 0.0175 TURNS/90% MCP/V.LIM +0.1G/RIGHT 0.0004 0.00175 TURNS/90% MCP/V.LIM +0.1G/LEFT 0.0004 0.00175 TURNS/MCP/NZ 1.2G/RIGHT 0.6667 2.5 TURNS/MCP/NZ 1.2G/LEFT 0.6667 2.5 TURNS/MCP/NZ 1.4G/RIGHT 0.2473 0.9272 TURNS/MCP/NZ 1.4G/LEFT 0.2473 0.9272 TURNS/MCP/NZ 1.6G/RIGHT 0.0824 0.3091 TURNS/MCP/NZ 1.6G/LEFT 0.0824 0.3091 TURNS/MCP/NZ 1.8G/RIGHT 0.0033 0.0125 TURNS/MCP/NZ 1.8G/LEFT 0.0033 0.0125 TURNS/MCP/V.LIM +0.1G/RIGHT 0.0003 0.0013 TURNS/MCP/V.LIM +0.1G/LEFT 0.0003 0.0013 Dur. 9.6 (s) SPECIAL TURNS 0.76 2.025 TURNS/VNE(30DEG)/*/RIGHT 0.0038 0.01 TURNS/VNE(30DEG)/*/LEFT 0.0038 0.01 TURNS/VNE IN AUTO.(30DEG)/*/RIGHT 0.00094 0.0025 TURNS/VNE IN AUTO.(30DEG)/*/LEFT 0.00094 0.0025 TRANSITION/TURN IN TRANSITION/*/RIGHT 0.3753 1 TRANSITION/TURN IN TRANSITION/*/LEFT 0.3753 1 Dur. 14 (s) Page MG 11 - 26
FIGURE AC 27.MG 11-9. EXAMPLE OF TWIN TURBINE USAGE SPECTRUM (continued) CONDITION % of time Nb per hour LATERAL FLIGHT 2 8 Dur. 9 (s) 5 KTS/*/RIGHT 0.095 0.38 Lat.Back rep. Speed rep.
5 KTS/*/LEFT 0.095 0.38 95.00% Lateral 10.00% 5 kts 10 KTS/*/RIGHT 0.095 0.38 5.00% Backward 10.00% 10 kts 10 KTS/*/LEFT 0.095 0.38 10.00% 15 kts 15 KTS/*/RIGHT 0.095 0.38 40.00% 17 kts 15 KTS/*/LEFT 0.095 0.38 10.00% 19 kts 17 KTS/*/RIGHT 0.38 1.52 5.00% 21 kts 17 KTS/*/LEFT 0.38 1.52 5.00% 25 kts 19 KTS/*/RIGHT 0.095 0.38 5.00% 35 kts 19 KTS/*/LEFT 0.095 0.38 5.00% max 21 KTS/*/RIGHT 0.0475 0.19 21 KTS/*/LEFT 0.0475 0.19 25 KTS/*/RIGHT 0.0475 0.19 25 KTS/*/LEFT 0.0475 0.19 35 KTS/*/RIGHT 0.0475 0.19 35 KTS/*/LEFT 0.0475 0.19 VMAX/*/RIGHT 0.0475 0.19 CONDITION % of time Nb per hour VMAX/*/LEFT 0.0475 0.19 VMAX/*/REARWARD 0.1 0.4 100 AC Page MG 11 - 27
AC 27-1B, Chg 1 2/12/03
INTENTIONALLY
LEFT
BLANK
Page MG 11 - 28
CHAPTER 3
AIRWORTHINESS STANDARDS
NORMAL CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG)
AC 27 MG 12. § 27.865 (Amendment 27-36) EXTERNAL LOADS.
This AC MG paragraph material is now contained in AC 27.865B, in Subpart D.
Page MG 12 - 1
AC 27-1B, Chg 1 2/12/03 Page MG 12 - 2
CHAPTER 3
AIRWORTHINESS STANDARDS
NORMAL CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG)
AC 27 MG 13. SYSTEMS CERTIFICATION CONSIDERATIONS.
a. Supporting Systems.
(1) Purpose. The purpose of this AC paragraph is to provide guidance on how to show compliance to Part 27 regulations as they apply to supporting systems for other systems that provide required functions. The systems that require support from supporting systems are defined as dependent systems in the following guidance.
Application of recent technology is one of the predominant causes of more dependent/supporting systems relationships. More systems are employing technology that is dependent on supporting systems such as electrical, hydraulic, and/or other power sources or signal inputs. Certification of systems that are dependent on supporting systems to provide required functionality must consider the issues associated with this interdependent relationship.
(2) Definitions.
(i) Integrity. The term “integrity” for the purpose of this AC paragraph includes the hardware quality requirements, including reliability (availability); as well as the software level requirements, as defined in RTCA/DO-178B.
(ii) Criticality. The term “criticality” refers to the five levels of criticality addressed in this document in paragraph AC 27.1309.d.(2)(ii)(B).
(iii) Supporting System(s). The term “supporting system(s)” as used in this paragraph means any system(s) that provides an input to another “dependent” system, such that these dependent system(s) cannot function correctly without that input being present/correct.
(iv) Dependent System(s). The term “dependent system(s)” as used in this paragraph means any system/s that receives an input from another system or sensor.
(3) Related Documents.
Page MG 13 - 1
AC 27-1B, Chg 1 2/12/03
(i) Federal Aviation Regulations (FARs) Paragraphs 27.1301, 27.1309,
27.1351, and 27.1435.
(ii) Standards - Latest revision of RTCA/DO178 and RTCA/DO 160; Parts of SAE documents ARP4754 and ARP4761.
(4) History: Applications of recent technology for systems have, in many cases, resulted in systems that are dependent on one or more supporting system(s) for inputs such as power or signal sources of any type. This relationship creates concerns for recognition that the criticality of the supporting system may be higher because of its role of supporting a dependent system of high criticality. The example of Liquid Crystal Displays (LCD) for engine instruments, in particular, has caused concern about the integrity of the supporting electrical power system. Past designs for engine instruments did not require electrical power for operation, but present designs with LCDs do require electrical power. Additionally, engine instruments of those older helicopter designs were driven from a mixture of sources such as independent wet line, pneumatic, and electrical drive (Tach Generator) inputs, and thus had independent failure modes from the sensor/power input aspect(s). This means that the integrity of the electrical power supplied to the dependent system must be commensurate with the level of integrity as required for the highest criticality engine instrument application(s). This also stimulates the concern that the electrical power system can become a common point for failure of all engine instruments simultaneously, as well as anything else powered by the electrical system. For this example, these considerations represent an increase of integrity requirements for the electrical power system over previous designs of electrical systems for VFR helicopters. In the past, these electrical systems did not support required functions of higher criticality and were allowed to be simple in design with low design integrity and susceptible to single point faults. Application of recent technologies for systems resulting in dependent systems that require supporting systems must address the concerns for higher integrity and single point faults.
(5) Discussion: Integrity of supporting systems must be sufficient to support the required integrity of their associated dependent systems. The relationship of supporting systems to dependent systems is similar to an analogy of them being links in a chain, where the weakest link must be able to support the required integrity level that is consistent with the associated criticality category assessment. This principle is not new, but there may not be recognition that systems previously accepted at low integrity levels may not be acceptable because of their new role as supporting system(s). New emphasis must be applied to determine acceptability of previous designs that have become supporting systems through application of new technology or changes of system architecture. This is particularly true for derivative designs, or changes to existing design by either supplemental type certificate (STC) or field approval, where new technology system applications, or system architecture changes have been applied, that created a dependent/supporting system relationship. The main concerns are for systems such as electronic displays that are installed and supported by nonupgraded systems, such as single source and/or low reliability power generation and distribution systems. However the concerns related to supporting syst ems are not Page MG 13 - 2
limited to displays for dependent systems, since control systems could also be affected.
Integrity for fault considerations must be addressed for supporting systems in relation to dependent systems when the dependent system’s provided functions are assessed at criticality levels of Major, Hazardous/Severe-Major, or Catastrophic. These integrity and fault considerations must address not only a particular dependent system, but also the accumulative effect on other systems that the same supporting system’s malfunction may affect. This may, in turn, affect the aircraft level functional hazard assessment (FHA) as the supporting system could act as a common point for simultaneous failures of more than one system. Additionally, the design of the su pporting systems should preclude single point failures/faults for systems that support dependent systems functions assessed to have a criticality of Catastrophic.
(6) Certification Approach. There are three basic parts to the supporting systems concerns addressed herein and they are the inclusion of supporting systems in the integrity determination process, the design considerations for supporting systems relating to more than one system, and single point faults for the supporting systems themselves.
(i) A two-step procedure should be used to determine the adequate integrity level for supporting systems. The first step is to determine the level of criticality associated with loss/malfunction of all or any combination of the dependent system’s functions and all combinations of other dependent system’s functions that require support from the same supporting system. This can be achieved through the use of an FHA and associated FTA's. The criticality category level determined from this assessment must be a product of failure/malfunction possibilities for all of the involved dependent/supporting systems combinations and the worst case operational consideration for the function(s) provided by the dependent systems. The second step is to determine whether the supporting system’s design integrity is sufficient to address the determined criticality category. The design integrity should address failures/malfunctions results of the dependent system(s), any combination of failures/malfunctions due to effects on more than one dependent system, and single point failures of the supporting system itself.
(ii) Analyses may be used to meet the criteria outlined in the second step above, for systems that support one or more dependent system functions whose loss or malfunction is assessed to be Hazardous/Severe-Major orCatastrophic. Analyses, such as a fault tree analysis, in combination with a common cause analysis to validate assumptions regarding the independence of faults, should be performed to show compliance. Testing may be required to validate the analysis, if the system is complex or dynamic in nature.
NOTE: Showing high reliability for a single thread system is not sufficient to meet the requirements for a Catastrophic failure condition category, thus reliability cannot be used to substitute for the preclusion of single point failures/faults.
Page MG 13 - 3
AC 27-1B, Chg 1 2/12/03
(7) Summary: Supporting systems should be considered an integral part of the dependent system(s) that provides the required functions, for the purpose of addressing design integrity requirements.
b. Complex System Integration
(1) Explanation. Complex integrated systems addressed by this paragraph are those systems that provide more than one function from a single electronic device or from more than one inter-related electronic devices/components. The inter-relationship is based on common aspect(s) of providing the functions. The definition of complexity as it applies to integrated systems, is a design condition that exhibits the characteristic of possible combinations of simultaneous failures/faults, as opposed to simple systems where there exists only failures/faults that can be considered individually. Integration that results in providing several functions from one design source inherently increases complexity, thus the two describing terms of “complex” and “integrated” are not independent from one another. Computers have become more powerful with recent increases in technology. Also, related sensors and servomechanisms have greatly improved. This has created an atmosphere from which complex integrated systems have spawned. Integrated systems can have the effects of reduced weight, economic advantages, and system enhancements. However, with these advantages there are some concerns that must be addressed, as this concept inherently creates problems with showing compliance to system independence requirements.
(2) Procedure.
(i) Integrated Systems typically compromise the concept of independence for failures/malfunctions and system/function separation. Using this as a given, the approach for showing compliance for systems that have a requirement for independence is to provide elevated system integrity to make up for the loss of independence. The requirements for independence are both direct and inferred. The direct requirements are defined by requirements for system separation and for specific systems. The inferred requirements for independence are those that inherently have independence by their method of implementation until integration of dissimilar functions by recent technology. They are inferred since past methods of implementation provided independence and therefore no direct requirement was defined.
(ii) The elevated integrity typically consists of high software levels and high system reliability that addresses the failure condition categories determined by a Functional Hazard Assessment (FHA). This approach basically states that the independence for failures and function separation is absent, but the probability is small for loss or malfunction, and the software level will match the threat level identified by the FHA. Provided the integrity is a reality, this approach works pretty well for the loss and malfunction aspects. However, system separation requirements may not be satisfied as easily, as they are mostly concerned with common mode failures from external sources.
Some common mode concerns are temperature, fire, water, EMI, and physical mechanical threats.
Page MG 13 - 4