AC 27.1B, Chg 4 5/1/2014 PCDS personnel carrying device IGE in ground effect Systems IIDS integrated instrument display syst em ILS instrument landing system IMC instrument meteorological conditions PCF P IO PSA PSIG post crash fire pilot induced oscillation preliminary safety assessment pounds per square inch INS inertial navigation system gauge ISA international standard QPL qualified parts list atmosphere RFM rotorcraft flight manual ISIS integral spar inspection system ITT inter-turbine temperature RFMS rotorcraft flight manual supplement KCAS knots calibrated airspeed RGL Regulatory and Guidance KIAS knots indicated air speed Library KTAS k nots true airspeed LDP landing decision point RPM RTC A revolutions per minute Radi o Technical Commission LPV l ocalizer performance with Of Ae ronautics ver tical guidance LRU line replaceable unit LWC liquid water content MC maximum continuous MCP maximum continuous power MEL minimum equipment list MG miscellaneous guidance MGB main gearbox MGT measured gas temperature MGW maximum gross weight MMEL master minimum equipment list MSL mean sea level MVD median volume diameter NASA National Aeronautics and Space Administration NDI non-destructive inspection NM nautical mile NPRM notice of proposed rulemaking NTSB National Transportation Safety Board NVG night vision goggles NVIS night vision imaging systems OAT outside air temperature OEI one engine inoperative OGE out of ground effect RVR S AE SAR SAS SCAS SHP S/N SRM SSA STC STOL TBO TC TCDS TDP TIA TIR TOP TOT TSO TVP VBIM VFR VMC runway visual range Society of Automotive Engineers search and rescue stability augmentation system stability and control augmentation systems shaft horsepower stress vs. number of cycles structural repair manual system safety assessment supplemental type certificate short takeoff and landing time between overhaul type certificate type certificate data sheet takeoff decision point type inspection authorization type inspection report takeoff power turbine outlet temperature technical standard order true vapor pressure visual blade inspection method visual flight rules visual meteorological PBA pitch bias actuator conditions Page xxii
2/4/2016 VOR very high frequency omnidirectional range radio VSI vertical speed indicator V/STOL vertical/short takeoff and landing VTOL vertical takeoff and landing WAT weight, altitude, temperature HD HP VD VH VMO VNE VTOSS VX VY MMO NF NG NP NR CD CL CP CT AC 27-1B, Chg 7 Altitudes density altitude pressure altitude V speeds diving speed speed in level flight with maximum continuous power maximum operating limit speed never-exceed speed takeoff safety speed for Category A rotorcraft speed for best angle of climb speed for best rate of climb maximum operating mach number N speeds free turbine speed gas generator speed power turbine speed rotor speed Coefficients coefficient of drag coefficient of lift coefficient of power coefficient of thrust Page xxiii
CHAPTER 1. PART 21 FAR 21 - GENERAL
CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS (Amendment 21-50) AC 21.16. § 21.16 SPECIAL CONDITIONS.
a. The Process. Chapter 2, Section 1, Paragraph 8 of the Type Certificate Handbook, Order 8110.4A, provides detailed guidance on the special conditions process. However, much of that material has been outdated with the implementation of the Aircraft Certification Directorate Program. Rotorcraft special conditions are processed through the Rotorcraft Standards Staff, ASW-110. That office will ensure coordination with the affected agency and industry elements including the Assistant Chief Counsel. All comments will be considered and the disposition document ed by the Rotorcraft Directorate. ASW-100 will issue the special conditions.
b. Basis for Development.
(1) Special conditions are justified on the basis of the existing Part 27 being inadequate or inappropriate due to novel or unusual design features of the rotorcraft to be certificated.
(2) The phrase “novel or unusual” as used in § 21.16 is a very relative term. As used hereafter in applying § 21.16 to justify the issuance of special conditions, “novel or unusual” will be taken with respect to the state of technology envisaged by the applicable airworthiness standards of this subchapter. It must be recognized that in some areas which will vary from time to time, the state of the regulations may somewhat lag the state of the art in new design because of the rapidity in which the state of the art is advancing in civil aeronautical design and because of the time required to develop the experience base needed by the FAA/AUTHORITY to proceed with general rulemaking.
Applicants for type certification of a new design have the opportunity to mitigate the impact of not knowing the precise airworthiness standards to be applied for “novel or unusual design features” by consulting with the FAA/AUTHORITY early in their certification planning when such features are suspected or known by the applicant to exist. It should also be recognized that, because of the intentional objective nature of the airworthiness standards of this subchapter, many new design features which might be thought of as “novel or unusual” may already be adequately covered by existing regulations, thus obviating the need to issue special conditions.
(3) Before proposing special conditions, the certification staff should very thoroughly analyze the existing regulations and ensure they are inadequate or inappropriate in light of a new and novel design feature.
Page FAR 21 - 1
AC 21.31. § 21.31 TYPE DESIGN.
The regulatory basis for requiring data to define the design is contained in § 21.31.
This section is self-explanatory and broad enough in scope to give the certification staff access to sufficient data to determine compliance with Part 27.
AC 21.33. § 21.33 INSPECTION AND TESTS.
a. Applicant Responsibility. Section 21.33 requires the applicant to:
(1) Ensure the test rotorcraft conforms to the type design. This must be accomplished prior to presentation to the FAA/AUTHORITY for testing.
(2) Conduct all inspections and tests necessary to determine compliance with the airworthiness and noise requirements.
b. FAA/AUTHORITY Responsibility.
(1) The design evaluation engineers should ensure that the type design is adequate in their technical area and that the inspections and tests to be conducted are appropriate and sufficient to show compliance with Part 27.
(2) As changes to the rotorcraft are made during the test program, the flight test crew should ensure that the appropriate design evaluation engineer concurs with the change and the conformity inspection of the change has been conducted.
AC 21.35 § 21.35 (Amendment 21-59) FLIGHT TESTS.
a. Explanation.
(1) This section outlines the requirements of the applicant for aircraft type certification and should be used in conjunction with FAA Order 8110.4A, Section 5.
Section 21.35 requires, in part, that the applicant conduct sufficient flight tests to show compliance with the flight requirements throughout the proposed flight envelope. The results of the applicant’s flight test should be submitted to the FAA/AUTHORITY in report form for evaluation to determine what verification flight tests the FAA/AUTHORITY may elect to conduct. The report should conclude that in the applicant’s opinion the test aircraft complies with the applicable certification requirements. The FAA/AUTHORITY verification flight test should include, but not be limited to, the critical or marginal results contained in the applicant’s flight test report.
The FAA/AUTHORITY’s role in the certification effort is not envisioned to be one of conducting day-to-day routine flight tests with the applicant, but only to verify his results through limited sampling. In certain tests, such as high altitude testing at a remote mountain site, there is an advantage in conducting flight tests concurrently with the applicant. Additionally, the FAA/AUTHORITY can provide technic al flight test Page FAR 21 - 2
assistance to the applicant in certain cases. This can be done after a cursory review and a letter of authorization is issued to the flight test crew.
(2) Preflight Test Planning. After the applicant’s flight test report is reviewed, it should be determined what FAA/AUTHORITY engineering flight tests are necessary.
These tests are normally specified in the Type Inspection Authorization (TIA). At the same time the FAA/AUTHORITY must know and agree to the applicant’s proposed means of data acquisition, reduction, and expansion of the flight test data. The adequacy of the test instrumentation should be evaluated prior to official type certification tests (reference paragraph AC 21.39).
(3) Order of Testing. The Federal Aviation Regulations are so worded that the results of some flight tests have a definite bearing on the conduct of other tests. For this reason, and to minimize retesting, careful attention should be given to the order of testing. The exact order of testing will be determined only by considering the particular rotorcraft and test program involved. Tests which are particularly important in the early stages of the program are:
(i) Airspeed calibration: All tests involving airspeed depend upon the calibration.
(ii) Engine power available determination.
(iii) Engine cooling.
(4) Test Groupings.
(i) Weight and c.g.: In addition to the regulatory relationship of one test to another, efficient testing requires that consideration be given to the accomplishment of as many tests on a single flight as can be accommodated successfully.
(ii) Special Instrumentation. Similarly, consideration should be given to grouping of tests that involve special instrumentation. Examples of these are takeoff and landing tests which usually require group equipment to record horizontal distance, height, and time. Ground calibration of the airspeed indicating system can be accomplished at the same time. It is the applicant’s responsibility to provide the necessary instrumentation.
(5) Functional and Reliability Testing
(i) Section 21.35(b)(2) requires that the applicant determine that “there is reasonable assurance that the aircraft, its components, and its equipment are reliable and function properly.” Section 21.35(f)(1) requires a Function and Reliability (F&R) program of 300 hours for turbine engine powered aircraft incorporating engines of a type not previously used in a type certificated aircraft. Section 21.35(f)(2) requires a 150-hour F&R program for all other aircraft. The following reflects general practices that Page FAR 21 - 3
have been used during rotorcraft certification programs. FAA/AUTHORITY have supported proposals which gave F&R test time credit for certification testing in lieu of dedicated F&R testing. In establishing such credit, the following should be considered:
(A) The point in time in which the rotorcraft reaches substantial conformity with the approved type design.
(B) The extent and complexity of the new design.
(C) For a previously certified rotorcraft, the F&R program requirement should be commensurate with the modification or change in type design and may be zero.
(ii) Historically, for major rotorcraft type certification programs, flight time credit has been limited so as to require an irreducible minimum of 50 hours of dedicated F&R flight time. For rotorcraft programs that involved new engine installations (mature engine design) or drive train/rotor system changes on previously certified aircraft (TC amendments or STC’s), flight time credit has been liberal and often resulted in very little or no dedicated F&R testing.
b. Procedures.
(1) Type Certification Flight Tests.
(i) Prior to initiating official FAA/AUTHORITY flight tests, a conformity inspection of the test aircraft must be accomplished. This is needed to assure that the test aircraft is in the proper configuration or “conforms” to the engineering drawings and documents that have been submitted to FAA/AUTHORITY, evaluated, and approved. It is absolutely essential to know the configuration being tested in any engineering flight evaluation. Conformity inspection prior to TIA flight tests assures that testing will not be wasted because of configuration uncertainties.
(ii) FAA Order 8110.4A, paragraph 67, contains a requirement that the applicant must keep the FAA/AUTHORITY advised of any configuration changes to the aircraft. The manufacturing inspector should keep the FAA/AUTHORITY flight test pilot apprised of any change which may affect safety of the test aircraft or may influence test results.
(iii) Results of the conformity inspection and the engineering flight test program must be documented. This is normally done in the Type Inspection Report (TIR). Results may be documented in any acceptable engineering format. The report should be in sufficient detail to clearly show how compliance with each appropriate section of the rules was determined.
(iv) The flight test pilot must assure that the FAA/AUTHORITY manufacturing inspector and certification engineer are aware of all configuration Page FAR 21 - 4
changes found necessary as a result of FAA/AUTHORITY tests. The manufacturing inspector is responsible for assuring that all changes are incorporated into production drawings after the design data reflecting the change have been approved by the certification engineer.
(v) Additional flight test responsibilities, procedures, and requirements during the certification flight test process are contained in FAA Order 8110.4A, Section 5, Flight.
(2) Function and Reliability Tests.
(i) A comprehensive and systematic check of all aircraft components must be made to assure that they perform their intended function and are reliable.
(ii) F&R testing should be accomplished on an aircraft which conforms to the type design. Non-conformities must be documented and accepted. F&R testing should follow the type certification testing described in paragraph AC 21.35b(1) above to assure that significant changes resulting from type certification tests are incorporated on the aircraft prior to F&R tests.
(iii) All components of the rotorcraft should be periodically operated in sequences and combinations likely to occur in service. Ground inspections should be made at appropriate intervals to identify potential failure conditions; however, no special maintenance beyond that described in the aircraft maintenance manual should be allowed.
(iv) A complete record of defects and failures should be maintained along with required servicing of aircraft fluid levels. Results of this record should be consistent with inspection and servicing information provided in the aircraft maintenance manual.
(v) A certain portion of the F&R test program may focus on systems, operating conditions, or environments found particularly marginal during type certification tests.
(vi) A substantial portion of the flying should be on a single aircraft. The flying should be carried out to an intensive schedule on an aircraft that is very close to the final certification standard, operated and maintained as though it were in service. A range of representative ambient operating conditions and sites should be considered. It is acceptable for non-F&R flight testing conducted at various sites and in varying ambient conditions to be used to satisfy the F&R requirements for those conditions.
Page FAR 21 - 5
AC 21.39. § 21.39 (Amendment 21-59) FLIGHT TEST INSTRUMENT CALIBRATION AND CORRECTION REPORT.
a. Explanation. It is the applicant’s responsibility to provide instrumentation for all parameters needed to show compliance with the airworthiness regulations.
(1) For those data which are necessary to show compliance with the regulations, a permanent record should be established. A permanent record is acceptable in either graphical or photographic form, and in some instances a manual recording may be satisfactory.
(2) Regardless of the record form, the accuracy of the record must be established by reference to a laboratory standard traceable to the National Bureau of Standards.
(3) If multiplexing is used, the time base must be synchronized to a reference point from which the magnitude of each parameter can unquestionably be determined.
Also, the sampling rate should be sufficiently frequent to ensure that the maximums, minimums, and trends of magnitude of the parameter are recorded with respect to time.
b. Procedures. Prior to conducting flight tests, the FAA/AUTHORITY flight test team should review the applicant’s flight test instrumentation, calibration, and correction report.
(1) The frequency of recalibration varies with the consistency of the instrumentation under consideration. For example, cyclic and collective position is sometimes calibrated immediately before and after a flight where these parameters are used to provide critical flight data. Six months is a typical interval for recording/signal conditioning and nonstrain gage sensors, while 1 year is typical for strain gaged components. Also, environmental effects such as vibration, humidity, temperature, etc., should be considered when determining whether recalibration is necessary.
(2) The highest and lowest magnitude of the parameter being recorded should be considered when establishing the scale for instrumentation. Ideally, the highest magnitude throughout the flight would fall on the maximum indicating point of the recording.
Page FAR 21 - 6
CHAPTER 2. PART 27
AIRWORTHINESS STANDARDS
NORMAL CATEGORY ROTORCRAFT
SUBPART A - GENERAL
AC 27.1. § 27.1 APPLICABILITY.
a. Explanation. This section prescribes the rotorcraft categories eligible for certification under this Part. There is no minimum weight limit for certification under Part 29; however, Part 27 is applicable to rotorcraft with maximum weights of 6,000 pounds or less.
(1) Without Engine Isolation. For single-engine rotorcraft and multiengine rotorcraft without engine isolation, the height-velocity (HV) diagram is conducted with sudden failure of all engines, and the takeoff maneuver must pass through the clear area of the diagram to the 50-foot point with all engines operating.
(2) With Engine Isolation. Part 27 multiengine rotorcraft may be certificated with engine isolation features (reference paragraph AC 27 MG 3). These rotorcraft are not required to meet the Part 29, Category A, performance requirements, and continued flight after an engine failure is not assured since under some conditions failure of the remaining engine may occur after a limited time. The takeoff is conducted with all engines operating, while the height-velocity diagram is determined with the most critical engine inoperative. If complete Part 29, Category A, design features and performance are achieved, the Category A performance may be included in the FAA/AUTHORITY-approved portion of the Rotorcraft Flight Manual although this performance is not required by the regulations.
b. Procedures. None.
AC 27.1A. § 27.1 (Amendment 27-33) APPLICABILITY.
a. Explanation. Amendment 33 formally introduced the requirements for certification of a Part 27 rotorcraft to Category A design and performance standards.
These standards are found in Appendix C of Part 27. The establishment of Category A design and performance for multiengine Part 27 rotorcraft is still voluntary. If so requested, the corresponding AC 29-2C material applies.
b. Procedures. None Page A - 1
AC 27.1B § 27.1 (Amendment 27-37) APPLICABILITY.
a. Explanation. Amendment 27-37 increases the normal category rotorcraft maximum gross weight limit from 6,000 to 7,000 pounds and introduces new airworthiness requirements. The gross weight increase was intended to compensate for past regulatory actions that, in effect, cumulatively increased the gross weight of normal category rotorcraft. The amendment also adds an explicit nine- passenger seat limitation. The new airworthiness requirements were intended to increase the level of safety to support a potential increase in the number of passenger seats associated with the increase in maximum gross weight limit.
b. Procedures. None AC 27.2 § 27.2 (Amendment 27-28) SPECIAL RETROACTIVE REQUIREMENTS.
a. Explanation.
(1) Amendment 27-28 requires a combined shoulder harness and safety belt (also called a torso restraint system) at each occupant’s seat for all rotorcraft manufactured after September 16, 1992.
(2) The design features of the restraint system are mainly contained in this section rather than having to refer to other sections within Part 27 except for a general reference to the differing strength standards between earlier static strength only standards and the static and dynamic strength standards of Amendment 27-25.
(3) Combined safety belt and harness strength standards system follows:
(i) Those rotorcraft type designs certificated to static strength standards alone prior to Amendment 27-25, such as 4 g’s forward may use belt and harness systems, characterized as 1,500 pounds strength systems, provided they comply with those standards. TSO C22f and earlier restraint systems have such ratings. A combined belt and harness with a 1,500 pounds rating, which comply with the Part 27 standards for the rotorcraft type design, but are not necessarily TSO approved, may be approved as a part of the type design. Such design information for a non-TSO’d item would be included in a note on the aircraft type certificate data sheet (TCDS) or specification sheet by part number as “required equipment.” TSO C114-approved torso restraint systems, characterized as 3,000 pounds strength system, may be used provided the design features comply with this section, but no special information on the TCDS is necessary.
(ii) Those rotorcraft type designs certified to dynamic test requirements of Amendment 27-25 should use torso restraint systems approved under TSO C114 or approved under equivalent standards such as those contained in Part 27.
(4) Load Distribution and Design Requirements. Although not stated in § 27.2, a 60 percent and 40 percent load distribution between the safety belt and harness, Page A - 2
respectively, is required in § 27.785(g). The safety belt should withstand 100 percent if the safety belt is capable of being used alone. Also, the safety belt or harness attachments to the seat or structure should include the 1.33 factor described in § 27.785(f)(2) of Amendment 27-21 for those rotorcraft with that certification criteria or should include the 1.15 factor as described in § 27.625 (and predecessor Part 6) standards for those rotorcraft with the earlier certification criteria. A factor is used whether test or analysis methods are used for static substantiation of the seating systems. Refer to paragraph AC 27.785c(i) (§ 27.785).
(5) The companion operating rule change of Amendment 91-220, amended § 91.205 (Amendment 91-223), affecting the aircraft equipment requirements.
Operating rule § 91.107(a) already requires use of the harness whenever the aircraft seat is so equipped.
b. Procedures.
(1) A TSO-approved combined safety belt and harness or torso restraint system may be used provided the installation requirements in § 27.2 are satisfied. A combined belt and harness (not necessarily TSO approved) may be approved as a part of the rotorcraft type design and so noted on the aircraft specification or TCDS.
(2) Structural analysis or static test may be used. For those rotorcraft designs that are subject to the dynamic test standards of § 27.562, the torso restraint system is required to be qualified for the particular use or installation in each rotorcraft type design. A dynamic test may be required for alternate restraint systems as well as the originally approved system. TSO C114 approval does not constitute approval for installation of a restraint system in a rotorcraft design subject to dynamic test.
(i) Paragraph 27.562 of this AC concerns in part the dynamic test standards of Amendment 27-25.
(ii) AC 23-4 dated June 20, 1986, concerns static test procedures for small airplane seats and restraint systems. (Certain small airplanes manufactured after December 12, 1986, should have harnesses for each seat also.) A test proposal for rotorcraft installations may adopt procedures appropriate to the particular installation.
The 60/40 percent distribution is sufficiently achieved when the blocks in Figure 4 of AC 23-4 are used.
(iii) The static design side load for the harness installation may be proven by test or analysis using the load distribution previously noted. For “older” designs, the side load of § 27.561(b)(3)(iii) is 2.0g, and for later designs (Amendment 27 -25 and later), it is 8.0g.
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AC 27.2A § 27.2 (Amendment 27-37) SPECIAL RETROACTIVE REQUIREMENTS.
a. Explanation. Amendment 27-37 specifies that for any change in type design to a rotorcraft that increases the passenger-seat capacity to a number greater than seven (and limited to a maximum of nine) the rotorcraft must meet all the applicable paragraphs of this Part in effect on October 18, 1999, regardless of the original certification basis. Additionally, the amendment allows for an increase in maximum gross weight from 6,000 pounds up to 7,000 pounds for previously certified rotorcraft provided there is no increase in the maximum passenger-seat capacity beyond that for which the rotorcraft was certificated on October 18, 1999. If a passenger-seat capacity increase is requested in addition to an increase in gross weight above 6,000 pounds, then, once again, all applicable paragraphs of this Part in effect on October 18, 1999, must be met.
b. Procedures. None.
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