AC 27-1B

Change 1-9

Advisory circular · Certification of Normal Category Rotorcraft

Approved
June 23, 2023
Last reviewed
June 29, 2023
Cancels
AC27-1B Change 8
Family
AC 27-1 · 10 versions
Revision
B, Change 9
14 CFR parts
27
Cited by
1 AD

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed October 23, 2026.

Show pages 1153–1164
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AC 27-1B, Chg 1 2/12/03 (MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES The following information is intended for guidance to assist the applicant in preparing an ICA.

For this sample, we will use a twidget, which is a sounder attached to an extendible cable assembly connected to a pivoting arm, which is mounted to the side of the fuselage structure at the right cabin door forward frame.

NOTE: The twidget manufacturer's ICA does not meet the requirements of Appendix A and cannot be referenced.

The following step-by-step procedure in this sample can be used to prepare an ICA for that appliance:

1. Determine the following:

a. What modifications to the rotorcraft will be required.

b. Determine what appliances will be replaced or added to the rotorcraft.

c. Determine which ATA chapters of the original rotorcraft manufacturer's maintenance manual will be affected by this TDC and which additional ATA chapters will be affected.

2. Review Appendix A, Part 27. Using the information derived in paragraph 1, determine which paragraphs are applicable and which are not applicable. As defined in Figure 2, provide the status of each requirement on the applicable paragraph. If the requirement is not applicable, place an NIA within the parentheses ( ). Address the remaining requirements in the ICA. A completed document for the twidget installation (see Figure 2) is included.

3. Prepare the ICA, which includes the applicable requirements specified in Appendix A to Part 27. This can be done by using the information provided in the Instructions for Continued Airworthiness Template. The regulatory requirements in the sample manual are in bold type.

Information to be copied is in normal type. Information in italics is for information only and should not be copied. See Instructions for Continued Airworthiness sample manual.

4. Ensure that the ICA includes the following:

a. A Cover Page, which will readily identify the publication as the applicant's ICA for that make and model rotorcraft.

b. A List of Effective Pages, which lists each page in the ICA and its revision number and revision date.

c. A Record of Revisions Page for listing the revisions which have been inserted in the ICA.

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(MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued)

5. Table of Contents is not required, but we recommend that it be included in the ICA.

6. Audit the proposed ICA to ensure the applicable requirements have been included. Edit the ICA document to ensure it does not contain incorrect terminology or incorrect references and determine it does contain correct spelling, proper grammar, and accurate information.

7. When referring to another publication, ensure the information in the referenced publication meets the requirements of Appendix A, Part 27. It is the responsibility of the applicant to obtain authorization to use the information contained in the referenced publication. Submit a copy of each publication referenced in the applicant's ICA.

8. Submit two complete copies of the proposed ICA in binders, a copy of the completed Figure 1 document, and a copy of any referenced publication to the FAA/AUTHORITY in sufficient time to allow for evaluation prior to the date acceptance is needed. The average turnaround time is 20 to 30 days depending on the workload at that time.

9. When FAA/AUTHORITY receives the applicant's proposed ICA, the applicant and the appropriate FAA/AUTHORITY are notified. FAA/AUTHORITY reviews and evaluates the ICA in the order they are received.

10. • If FAA/AUTHORITY finds the applicant's ICA does not meet the requirements, the review will be discontinued, and the applicant will be notified.

11. When the proposed ICA document, excluding the Airworthiness Limitations Section, is determined to be acceptable, the FAA/AUTHORITY will stamp, sign, and date the ICA. The applicant will be notified of the acceptance.

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AC 27-1B, Chg 1 2/12/03 (MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) Twidget Type Design Change Attachment 2

1. Use the list of appliances and modifications required for that Type Design Change (TDC) to determine which ATA chapters of the original rotorcraft manufacturer's maintenance manual the TDC will affect and which additional ATA chapters will be affected.

2. The following are component and systems that will be affected by the Twidget TDC:

a. Fuselage structure will be modified to mount twidget arm assembly.

b. Cabin door will be modified.

C. Electrical power will be required for electrical motor.

d. Hydraulic power source will be required for deploying and storing twidget arm.

e. Twidget control assembly will be installed in the cabin.

f. Control will be mounted in cockpit for emergency release of the twidget..

g. An Instrument will be installed in instrument panel indicating twidget's position.

h. Iwidget recording equipment and monitor will be mounted in cabin.

i. Twidget antenna will be mounted on belly of fuselage.

j. . Cables and wiring will be routed through rotorcraft.

k. Two-way communication will be required between the pilot and twidget operator.

1. Twidget gearbox requires servicing to full mark on site gage every 50 hours.

m. Twidget arm assemblies and clutch requires lubrication every 100 hours.

n. Iwidget installation requires an inspection every 300 hours.

o. Twidget arm assembly requires an ultrasonic test every 600 hours.

p. Clutch has a wear tolerance of 1.56 mm.

q. Clutch is life-limited to be replaced every 1,000 hours time in service.

r. Twidget gearbox is required to be overhauled every 1,000 hours time in service.

s. Iwidget gearbox attach bolt torque is 75-ft lb. and twidget arm assembly torque is 110 in Ib.

t. Warning: Twidget should be retracted during takeoff, landing, and cruise above 85 knots.

u. Caution: Do not tow or taxi the rotorcraft with the twidget arm deployed.

v. Placards are required on the twidget unit and in the cockpit.

3. This example TDC will affect ATA-100 chapters: 4 Airworthiness Limitations, 5 Inspection, 6 Dimensions, 9 Towing and Taxiing, 10 Parking and Mooring, 11 Placards, 12 Servicing, 23 Communication, 24 Electrical, 25 Furnishings, 29 Hydraulic, 31 Indication and Recording, 52 Doors, and 53 Fuselage. A Chapter 1 Introduction is also needed.

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(MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) INFORMATION:

Attachment 4 includes a Figure 2 for Thomas Copter Mods TDC to affix a Twidget installation on Thomas Copter model T-97J helicopter.

Figure 2 is intended to assist in determining which requirements are applicable to this certification project. The document contains each requirement with a set of parentheses, the appropriate regulation, and the location of information in the applicant's ICA.

Information obtained from Attachment 4 can be used to determine which requirements are applicable. For requirements that are not applicable, place an NIA in the parentheses. All other requirements would be applicable to the certification project. Place a Y if the required information is included in ICA. Figure 2 has been completed for the sample Twidget TDC.

Applicant that uses and completes Figure 1 and indicates the location of that information in the applicant's proposed ICA will reduce the time required to evaluate the ICA.

It is important that the applicant include the project number or numbers associated with the ICA, the name of the appropriate FAA/AUTHORITY office, the name of the project engineer, the applicant's company name, the make and model of rotorcraft being modified, and the date.

The completed Figure 1 should be submitted to FAA/AUTHORITY with the applicant's ICA.

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AC 27-1B, Chg 1 2/12/03 (MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) APPENDIX A PART 27 REQUIREMENTS The following is a breakdown of Appendix A to FAR/JAR Part 27 and is intended to provide guidance to assist an applicant for a Type Design Change under a Type Certificate (TC), Supplemental Type Certificate (STC), or Field Approval (FA) requiring Instructions for Continued Airworthiness (ICA). The breakdown is intended to provide guidance to assist an applicant in understanding the ICA requirements of FAR/JAR § 27.1529. An applicant may use the guidance to prepare the ICA. Completion of this appendix will provide information needed for the evaluation and will reduce the time required for evaluation of the proposed ICA.

() Status of ICA: Y = Yes included; N/A = non-applicable. The Location Column lists the page number in the Applicant's ICA that contains the information.

Project Number(s) ST01998RC-R ACO/FSDO: Rotorcraft ACO Project Engineer: Data Mastermine Applicant: Thomas Copter Mods Make: Thomas Copter Model: T97-J Date June 18, 1998 Requirement Regulation Location (NIA) ICA for each engine A27.1(b) N/A (NIA) ICA for each rotor A27.1(b) N/A (Y) ICA for each appliance required by this chapter A27.1(b) * All (Y) Any required information relating to the interface of the A27.1(b) See (Y) appliances, (N/A) engines and (N/A) rotors with the rotorcraft. NOTE 1 (Y ) If ICA are not supplied by the manufacturer of an A27.1 * All (NA) appliance, (NA) engine or (NIA) rotor installed in the rotorcraft, the ICA for the rotorcraft must include (Y ) the information essential to the continued airworthiness of the rotorcraft.

(Y ) A program showing how changes to the applicant's ICA will be A27.1(c) ATA O distributed.

(NIA) A program showing how changes to the ICA of the A27.1(c) N/A manufacture of the engine(s), rotor(s) and appliances installed in the rotorcraft will be distributed, if referenced in applicant's ICA (Y ) ICA that must be in a form of a manual or manuals as A27.2(a) * All appropriate for the quantity of data.

(Y ) A format of the manual or manuals which must provide for a A27.2(b) * All practical arrangement.

(Y) Content prepared in the English language. A27.3 * A11 Figure 2 REVISION: (DATE) Revision 4 Page 5 Page Apdx A - 66

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( MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) Requirement Regulation Location (Y ) Introduction information that includes (Y ) an explanation of A27.3(a)(1) ATA O the rotorcraft's features and (Y) data to the extent necessary for maintenance and preventive maintenance.

(Y ) A description of the (IN/A) rotorcraft and its systems and A27.3(a) (2) ATA 25 installations, (N/A) engines and its systems and installations, (NA) rotors and its systems and installations, (Y ) appliances and its systems and installations.

(Y) Basic control and operating information describing (Y A27.3(a) (3) ATA 25 ) how the rotorcraft components and systems are controlled and (Y ) how the rotorcraft components and systems are operated including (Y) any special procedure and limitations.

(Y ) Servicing information that covers details regarding (Y A27.3(a) (4) ATA 12 ) servicing points, (NA) capacities of tanks, (Y ) capacities of reservoirs, (Y ) types of fluids to be used, (Y ) pressures applicable to the various systems.

(Y ) Location of access panels for (Y ) inspection and (Y A27.3 (a) (4) See ) servicing. NOTE 2 (Y) Servicing information that covers details regarding (Y A27.3(a) (4) ATA 12 ) locations of lubrication points, (Y ) the lubricant to be used.

(Y) Equipment required for servicing. A27.3(a) (4) ATA 12 (Y ) Tow instructions and limitations. A27.3(a) (4) ATA 9 (Y) Mooring information A27.3(a)(4) ATA 10 (NA) Jacking information A27.3(a) (4) N/A (NA) Leveling information A27.3(a) (4) NA (Y ) Scheduling information for each part of the (Y ) rotorcraft A27.3(b)(1) See that, provides the recommended periods at which they should (Y) NOTE 3 cleaned, (Y) inspected, (Y ) adjusted, (Y ) tested, lubricated and (Y) the work recommended at these periods.

(NA) Scheduling information for the (NA) rotorcraft's engine(s) A27.3(b)(1) N/A that provides the recommended periods at which they should be (IN/A) cleaned, (IN/A) inspected, (IN/A) adjusted, (N/A) tested, (N/A) lubricated and (N/A) the work recommended at these periods.

NOTE: This information may be in the FAA/AUTHORITY accepted engine ICA.

Figure 2 (continued) REVISION: (DATE) Revision 4 Page 6 Page Apdx A - 67

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AC 27-1B, Chg 1 2/12/03 (MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) Requirement Regulation Location (NA) Scheduling information for the (N/A) rotorcraft's auxiliary A27.3(b)(1) N/A power unit(s) (APU) that provides the recommended periods at which they should be (NA) cleaned, (N/A) inspected, (N/A) adjusted, (N/A) tested, (N/A) lubricated and (N/A) the work recommended at these periods.

(N/A) Scheduling information for the (N/A) rotorcraft's rotor(s) that A27.3(b)(1) N/A provides the recommended periods at which they should be (N/A) cleaned, (N/A) inspected, (N/A) adjusted, (N/A) tested, (NA) lubricated and (IN/A) the work recommended at these periods.

(Y ) Scheduling information for the (Y ) rotorcraft's accessories A27.3(b)(1) See that provides the recommended periods at which they should be (Y ) NOTE 3 cleaned, (Y) inspected, (Y ) adjusted, (Y ) tested, (Y ) lubricated and (Y) the work recommended at these periods.

(Y) Scheduling information for the (Y ) rotorcraft's instruments A27.3(b)(1) See that provides the recommended periods at which they should be (Y ) NOTE 3 cleaned, (Y ) inspected, (Y ) adjusted, (Y ) tested, (Y ) lubricated and (Y) the work recommended at these periods.

(Y ) Scheduling information for the (Y ) rotorcraft's equipment A27.3(b)(1) See that provides the recommended periods at which they should be (Y NOTE 3 ) cleaned, (Y) inspected, (Y) adjusted, (Y ) tested, (X) lubricated and (Y) the work recommended at these periods.

(1) The degree of inspection for each part of the (NA) rotorcraft A27.3(b)(1) ATA 5 and its (N/A) engine(s), (N/A) auxiliary power unit, (INVA) rotor(s), (Y ) accessories, (Y ) Instruments and (Y ) equipment.

(Y) The applicable wear tolerances A27.3(b)(1) ATA 25 The applicant may refer to an (NA)accessory, (NA) instrument, or A27.3(b)(1) N/A (NA) equipment manufacturer as the source of this information if the applicant shows (NIA) that the item has an exceptionally high degree of complexity requiring specialized maintenance techniques, test equipment, or expertise.

(1) The recommended overhaul periods and necessary cross A27.3(b)(1) ATA 5 references to the Airworthiness Limitation Section.

Figure 2 (continued) REVISION: (DATE) Revision 4 Page 7 Page Apdx A - 68

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(MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) Requirement Regulation Location (Y) An inspection program that includes (Y ) the frequency and ( 427.3(b)(1) ATA 5

1) extent of the inspection necessary to provide for the continued airworthiness of the rotorcraft.

(Y) Troubleshooting information describing (Y ) problem A27.3(b)(2) See malfunctions, (Y) how to recognize those malfunctions and (Y NOTE 4 ) the remedial action for those malfunctions.

(N/A) Information describing the order and method of A27.3(b)(3) N/A (NA) removing and (NA) replacing engine(s) with any necessary precautions to be taken.

(NA) Information describing the order and method of A27.3(b)(3) N/A (NA) removing and (NA) replacing rotor(s) with any necessary precautions to be taken.

(Y) Information describing the order and method of (Y A27.3(b)(3) ATA 25 ) removing and (Y ) replacing parts with any necessary precautions to be taken.

(Y) Other general procedural instructions including (NA) storage A27.3(b)(4) ATA 8 limitations and procedures for (NIA) testing system during ground running, (N/A) making symmetry checks, (Y ) weighing and determining the center of gravity, (IN/A) lifting, (IN/A) shoring.

(NA) Diagrams of structural access plates and information needed A27.3(c) N/A to gain access for inspections when access plates are not provided.

(NA) Details for the application of special inspection techniques A27.3(d) N/A including radiographic and ultrasonic testing where such process are specified.

(NA) Information needed to apply protective treatment to structure A27.3(e) N/A after inspection.

(Y) All data relative to structural fasteners such as (Y A27.3(Đ) ATA25 ) identification, (Y) discarded recommendations, and (X) torque values.

(Y) A list of special tools needed A27.3(g) NOTE 5 (Y) The Instructions for Continued Airworthiness must contain a A27.4 ATA 4 section, titled Airworthiness Limitations that is (X) segregated and (Y ) clearly distinguishable from the rest of the document. NOTE: The Airworthiness Limitations Section in the applicant's ICA will be evaluated by the appropriate FAA/AUTHORITY.

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AC 27-1B, Chg 1 2/12/03 (MANUAL IDENTIFICATION) ATTACHMENT 4

TYPE DESIGN CHANGE

ICA RECOMMENDED PROCEDURES (Continued) Requirement Regulation Location (NA) The Airworthiness Limitations Section must set forth each A27.4 N/A mandatory replacement time, structural inspection procedure approved under § 27.571.

(Y ) If the Instructions for Continued Airworthiness consist of A27.4 ATA 4 multiple documents, the Airworthiness Limitations Section required by this paragraph must include in the principal manual.

(Y ) The Airworthiness Limitations Section must contain a legible A27.4 ATA4 statement in a prominent location indicating that the Airworthiness Limitations Section is FAA/AUTHORITY-approved and specifies required maintenance and/or inspections. The exact, required wording of this statement is found in the FAR/JAR.

Figure 2 (continued) NOTE: The Airworthiness Limitations Section (ALS) is evaluated and approved by FAA/AUTHORITY.

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(MANUAL IDENTIFICATION)

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AC 27 APPENDIX B. AIRWORTHINESS GUIDANCE FOR ROTORCRAFT INSTRUMENT FLIGHT.

a. Explanation.

(1) Requirements for instrument flight rules (IFR) have been incorporated into Appendix B to part 27, Amendment 19. Various information from previous interim standards, procedures, test techniques, and acceptable means of compliance for rotorcraft IFR flight is included in the following sections.

(2) Amendment 27-44 made a change to paragraph V. Static Lateral Directional Stability, concurrent with the change to § 27.177, to allow for a small range of sideslip angles (2-3 degrees) for which sideslip angles need not increase steadily with control deflection. The previous rule language stating that directional control position must increase in approximate constant proportion with sideslip angle has been replaced. The intent of this change is that an increase in directional control position must produce an increase in sideslip angle linearly. At greater sideslip angles appropriate to the type rotorcraft, increase in directional control position need not produce a linear increase in sideslip angle but should not become neutral or negative. The change in paragraph VIl revised the current requirement to clearly state the requirements to be met in the event of a stability augmentation system (SAS) failure.

b. Procedures.

(1) General.

(i) The certificated instrument flight envelope may be more restrictive than the visual flight rules (VFR) envelope in terms of weight, CG, speed, altitude, or rate of climb and descent. The approved envelope should be operationally practical and not impose constraints with which the crew has difficulty complying. The IFR altitude envelope should extend to at least 10,000 feet to be operationally practical in the National Airways System.

(ii) Controllability requirements are to be met from 0.9 VMINI to 1.1 VNEI. Stability requirements must be met where specified. Stability devices are to be designed to allow safe flight following failures.

The evaluating pilot should assure that all equipment and devices installed for FR, including reasonable failures of that equipment, do not compromise the VFR approval for that rotorcraft. For example, stability system failures can cause loss of swashplate or tail rotor control travel when failed in a hardover condition. If the device remains in the hardover position after the stability system is turned off, control capability can be compromised. Cyclic controllability tests at high speed and at the limiting rearward flight condition, or tail rotor tests in sideward flight at high altitude, may reveal a lower control capability and a more restrictive envelope. Revision to the envelope approved for VFR conditions may be required when stability equipment is installed. In addition, controllability testing should be accomplished with the control rigging set at the most adverse production tolerance for the test condition (e.g., minimum forward swashplate for high speed testing).

(2) Trim. Compliance with the FR trim requirement may be met by use of a magnetic brake with a recentering button, an electrically driven trim system activated by a "beeper" type control, or other means, so long as the system does not introduce any objectionable discontinuities in the force gradient or otherwise result in objectionable flight characteristics. Trim release devices should be free of objectionable stick jump. Electrically driven trim systems should have a smooth change in force with a rate compatible with the normal rotorcraft maneuvers. Only the cyclic trim control must exhibit positive self-centering characteristics. Collective and directional controls are not required to incorporate positive self-centering characteristics. Movement of the trim controls should produce a similar effect on the rotorcraft in a plane parallel to that of the control motion. The control system free play and breakout force must be evaluated to assure a close and direct correlation between control input (force and deflection) ' Paragraph VII was effective 9/17/2009 as part of the new and changed guidance material for the Performance and Handling Qualities final rule (Amdt. 27-44, 73 FR 11000, Feb. 29, 2008).

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AC 27-1B, Chg 7 2/4/2016 and rotorcraft response (pitch, roll, yaw, and heave (vertical motion)), and to permit small, precise changes in flight path. If trim control is provided in a SAS, the control should be of such design and so installed that any failure will not create a hazardous condition. If an inadvertent out-of-trim condition can be developed, its effect on the rotorcraft should be investigated. There should be investigation of these failures or malfunctions as outlined in paragraph b.(7), Stability Augmentation Systems, below. Controls for this trim function should be installed such that the controls should operate in the plane and with the sense of motion of the rotorcraft. Each control means should have the direction of motion plainly marked thereon or adjacent to the control.

(3) Static Longitudinal Stability.

(i) Positive static longitudinal stability is a key IFR requirement, which assures a selfcorrecting airspeed response and allows a pilot to recognize any substantial change in speed. The phrase "substantial speed change" as used in Appendix B to part 27, paragraph IV., is normally considered to mean at least a 10 knot departure from trim speed. Such a change in airspeed must be accompanied by a stick force clearly perceptible to the pilot (i.e., a discernable and quantifiable force gradient). Very shallow force gradients can be approved for systems with low deadband and low friction.

Systems with significant friction and deadband require much steeper force gradients to be acceptable.

The longitudinal force gradient can be determined by either of two methods. The most commonly used method (applicable only to irreversible control systems) measures the cyclic forces with the rotorcraft on the ground and the rotor stopped (with hydraulic and electric power units if required). The force applied to the cyclic stick and the cyclic stick displacement is measured and a plot of stick force verses displacement in each longitudinal direction is obtained. Following the ground test, the longitudinal static stability tests are conducted in the air as described in section 27.175 of this AC. The cyclic displacement measurements gathered during flight test are then assigned force values from the ground mechanical characteristics test and the force values are cross plotted with the corresponding airspeeds to produce a plot of cyclic force verses airspeed. The trim system should be on during the test and the aircraft trimmed at the trim speed. After each end point, the cyclic should be allowed to slowly return to the trim position.

When all the force is released from the cyclic stick and the airspeed has stabilized, note the airspeed.

For single pilot approval only, the airspeed must return to within 10 percent or 10 knots, whichever is less, of the trim speed. An alternate method of determining the longitudinal stick force stability is to measure the force on the cyclic stick in flight using a hand held force gage or other force measuring instrumentation. The in-flight technique is the same as the first method. Testing should be accomplished at a minimum of two altitudes. One altitude should be low enough to assure limiting power is attained.

Another should be at or near the maximum approved altitude. Reasonable interpolation is allowed. If no marginal areas are apparent, interpolation over a 10,000 foot altitude range is considered reasonable.

(il) Tests for static longitudinal stability during approach should include the steepest approach gradient for which approval is requested. Static stability tests may be simulated by initially establishing a trimmed rate of descent for maximum approach gradient assuming zero wind conditions. Actual approach tests at the maximum approved gradient should be conducted to evaluate tracking and maneuverability, including the capability to correct downward to a glide path when approaching in a slight (10 knot) tailwind condition.

(iii) Rotorcraft that are approved for a minimum crew of two pilots for IFR operation are relieved from demonstrating stick force stability in climb, slow cruise, and descent. It is expected that these rotorcraft do comply with the VFR certification requirements of § 27.175.

(4) Static Lateral Directional Stability.

(i) Tests for directional stability usually require instrumentation for lateral cyclic position, pedal position, and sideslip angle. Testing for compliance with the specific directional requirement is relatively simple; however, the pilot should look for significant longitudinal trim changes, and short period dynamic modes, which might occur only during sideslip conditions. Side force characteristics are indicated by the variation of bank angle with sideslip during steady heading sideslips. The number of ball widths of deflection is also indicative of the side force cue available to the pilot. A correlation between sideslip Page Apdx B - 2