331. § 27.773 PILOT COMPARTMENT VIEW.
a. Explanation. The section outlines requirements for pilot view in fairly general terms. Requirements are purposely less stringent than for transport category rotorcraft to allow for cockpit designs ranging from fully enclosed to open to the elements.
b. Procedures.
(1) The following procedures are one acceptable means of evaluating pilot compartment field of view considering only those objects in the pilot compartment and the windshield and its support structure in nonprecipitating conditions. The applicant's design is not required to meet these guidelines, and each design should be evaluated on its own merit. The area of visibility established in the following paragraphs will provide an acceptable level of visibility for a minimum crew of one pilot. In the event that a minimum crew of two, a pilot and copilot, is required, the second pilot should have an area of visibility equivalent to that provided for the pilot but on the opposite side. In this event, the pilot's area of visibility to the left as shown in Figure 331-1 needs only to comply to 60° left, and the copilot's area of visibility to the right needs only to comply to 60° right.
A single point established in accordance with the provisions of this paragraph constitutes the referenced eye position (i.e., a point midway between the two eyes) from which the central axis may be located. The referenced eye position is a reference datum point from which the aircrew station geometry is constructed. The referenced eye position should be located by means of ship's coordinates that contain station reference number, water line, and butt line for both pilot and copilot, if applicable, and comply with:
(A) The pilot's seat in a normal operating position from which all controls can be utilized to their full travel by an average subject, and which should provide for vertical adjustment of the seat of not less than 2.5 inches above and
2.5 inches below this initial vertical position.
(B) The seat back in its most upright position.
(C) The seat cushion depression being that caused by a subject weighing 170 to 200 pounds.
(D) The longitudinal axis of the rotorcraft to be that of "cruise attitudei (0.9VH or 0.9VNE Whichever is lower).
(E) The point established not beyond 1 inch to the right or left of the longitudinal centerline of the pilot's seat.
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АС 27-1A 7/30/97 All measurements made from the single point established in accordance with this paragraph.
(i) A dual lens camera, as photo recorder, should be used in measuring the angles specified in the paragraphs listed below. Other methods, including the use of a goniometer, are acceptable if they produce equivalent areas to those obtained with a dual lens camera. When not using a dual lens camera, compensation should be made for one half of the distance which exists between the eyes, or 1¼ inches. With the referenced eye position located as indicated in Paragraph 331b(1)(1), and utilizing binocular vision and azimuthal movement of the head and eyes about a radius, the center of which is 3 and 5/16 inches behind the referenced position (this point to be known as the central axis), the pilot should have the following minimum areas of vision measured from the appropriate eye position. (See Figure 331-1.)
(A) 20° forward and above the horizon between 0° and 100° left.
(B) 20° forward and below the horizon between 10° and 100° left.
(C) 20° forward and below the horizon at 10° left increasing to a point 30° forward and below the horizon at 10° right.
(D) 50° forward and below the horizon between 10° right and 135° right.
(E) 20° forward and above the horizon at 0° increasing to a point 40° above the horizon at 80° right and 100° right and then decreasing to a point 20° forward and above the horizon at 135° right.
Any vertical obstruction which falls within the minimum area of visibility outlined in 331b(1)(ii) should be governed by the following:
(A) Between 20° right and 20° left--no vertical obstruction.
(B) Between 20° right and 135° right -- no vertical obstruction greater than 2.5 inches in width.
(C) Between 20° left and 100° left -- no vertical obstruction greater than 2.5 inches in width.
(iv) Any horizontal obstruction which falls within the minimum area of visibility outlined in Paragraph 331b(1)(ii) should be governed by the following:
(A) The area 15° forward and above the horizon between 135° right and 40° left decreasing to a point 10° above the horizon at 100° left, and 15° forward 406 Par 331
and below the horizon between 135° right and 100° left should be free from horizontal obstructions.
(B) The area above and below the horizon which is between the minimum area of vision specified in Paragraphs 3316(1)(ii) and 331b(1) (iv)(A) is limited to one horizontal obstruction above and one below the horizon. These horizontal obstructions should not be greater than 4 inches in width. An overhead window which will provide twice as much additional visibility as that lost due to the obstruction should be located immediately above any obstruction above the horizon. This requirement is in addition to any area of visibility specified by Paragraph 331(b)(2) (ii) which may be included in the overhead window area.
(C) If the instrument panel obstructs any required area between 10° left and 10° right below 20° forward and below the horizon, a window which affords triple equivalent additional visibility should be located immediately below and between the angles of 20° left and 20° right above 65° below the horizon.
(v) For steep rejected takeoffs and steep approaches (such as to oil rigs or confined heliports), the visibility should be such that the pilot can see the touchdown pad and sufficient additional area to the side and forward to provide both an accurate approach to the touchdown point as well as a satisfactory degree of depth perception.
A 5-inch head movement by the pilot forward and/or sideward of the normal position is acceptable in determining compliance.
(2) Since glare and reflection often differ with the sun's inclination, consideration should be given to evaluating the cockpit at midday and in early morning or late afternoon. Windshields with embedded wire heating elements should be evaluated for distortion with the system both "ON" and "OFF." If night approval is requested, all lighting, both internal and external, should be evaluated in likely combinations and under expected flight conditions. Although a certain amount of equipment reflection (avionics control heads, etc.) in the windshield may be unavoidable, the pilot's normal field of view should be unobstructed. Windshield reflections often dictate large glareshields resulting in reduction of the optimum field of view. This problem is most apparent in IFR equipped aircraft (having larger instrument panels and avionic consoles) operating in VFR utility roles. Landing and taxi lights should be exercised throughout their adjustment range (if applicable) to check for reflections, particularly in chin windows. Anticollision and strobe lights should be evaluated to ensure that frequency interaction and reflections off the rotor do not result in distractions to the pilot. The effect of cabin lighting on the pilot compartment view should be assessed, particularly on EMS-configured aircraft where the in-flight use of cabin lights may be mandatory.
(3) Moderate rainfall is defined by the National Weather Service as an accumulation of between 0.01 and 0.03 inches in 3 minutes. Since the rule effectively permits open cockpits, a determination of what would unduly impair the pilots' view in Par 331 407
moderate rainfall is obviously very subjective. If it is established that rain removal systems are necessary, those systems may be evaluated on the ground with a hose, but they should also be assessed in flight under applicable conditions. Obscuration of side windows by rainfall should be addressed, particularly for confined area approaches. The need for windshield wash systems should be assessed if the aircraft will be used in an offshore salt-spray environment.
(4) If icing certification is requested, a means must be provided to ensure that a sufficiently large viewing area is kept clear of ice to permit safe operation. As a minimum, a clear area on the windshield should be available, although some configurations could require a clear view in other areas to provide an adequate level of safety in certain operations. Systems provided to ensure a clear view in icing conditions should be evaluated during icing flight tests.
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Par 331 40° 7/30/97
THIS AREA
LIMITED TO ONE
HORIZONTAL DESTRUCTION (NOT GREATER THAN 4 INCHES IN WIDTH) 20°
PILOT VIEW FOR ZERO REFERENCE
CREW OF TWO (CENTRAL AXIS)
PILOT VIEW FOR NO, HORIZONTAL OBSTRUCTIONS
CREW OF ONE BETWEEN DASH LINES 20°
THIS AREA LIMITED TO ONE HORIZONTAL OBSTRUCTION 40° (NOT GREATER THAN 4 INCHES IN WIDTH) (NOTE: PILOT IN COMMAND IS CONSIDERED
TO OCCUPY RIGHT-HAND SEAT 50° 100° 80° 60° 40° 20° 10° 0° 10° 20° 40° 60° 80° 100° 120° 135°
• VERTICAL OBSTRUCTIONS → - NOVERT. → VERTICAL OBSTRUCTIONS LIMITED TO 2.5 INCHES IN WIDTH OBSTRUCTIONS LIMITED TO 2.5 INCHES IN WIDTH FIGURE 331-1. COCKPIT VISIBILITY AC 27-1A
332. § 27.775 WINDSHIELDS AND WINDOWS.
a. Explanation. The use of nonsplintering safety glass is specified when glass is used in windshields and windows to protect crew and passengers in the event that window fracturing occurs.
b. Procedures. Use nonsplintering safety glass in windshield or window applications which contain glass rather than plastic acrylics, polycarbonates, epoxys, etc. The glass selected should meet a specification such as MIL-G-25871, and if new vendors are selected by an airtrame manufacturer, test data should be obtained from the vendor to demonstrate the safety glass provided meets an acceptable specification and provides adequate nonsplintering capability.
332A. § 27.775 (Amendment 27-27) WINDSHIELDS AND WINDOWS.
a. Explanation. Amendment 27-27 changed § 27.775 to allow the use of materials other than nonsplintering safety glass; i.e., plastics are allowed. Additionally, whatever material is used should not break into dangerous fragments upon impact.
b. Procedures. The procedures contained in Paragraph 332 apply equally to glass or plastics.
333. § 27.777 COCKPIT CONTROLS.
a. Explanation. This section defines the general cockpit control requirements.
Cockpit control location and arrangement with respect to the pilot's seat must be designed to accommodate pilots from 5'2" to 6'0" in height.
b. Procedures.
(1) The applicant should have a cockpit design report which documents the anthropometric suitability of the cockpit. Subsequent cockpit evaluations of control movement and location should be conducted with adjustable seats and/or controls positioned in a flight position for the subject pilot. Essential controls should be evaluated with the shoulder harness locked in the retracted position. Evaluation pilots should be aware of their individual anthropometric measurements and temper their assessments based on this information. Ideally, a new design should include evaluations by a range of different sized subject pilots. Control considerations for a second pilot position are the same as for the pilot station. Paragraph 330 discusses current philosophy concerning duplication of controls.
(2) As background, the following are examples of cockpit control issues which should be avoided:
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(i) Collective control blocking the lateral movement of a pilot's leg, which in turn restricts the left lateral cyclic displacement.
Seat or seat cushion impeding the aft cyclic movement.
(Ш) Inadequate space for large feet equipped with large flight boots.
(iv) Control/seat relationship which requires unusual pilot contortions at extreme control displacements.
(v) Control/seat relationship or control system geometry which will not permit adequate mechanical advantage with unboosted controls or in a boost OFF situation.
(vi) Addition of control panels or equipment to instrument panels or consoles which restrict full control throw.
(vii) Brake pedal geometry which results in inadvertent brake application upon displacement of the directional controls.
(vili) Controls for accessories or equipment which require a two-handed operation.
(ix) Emergency external cargo release controls which cannot be activated without releasing the primary flight controls.
(x) Essential controls which cannot be actuated during emergency conditions with the shoulder harness locked.
(xi) Throttle controls which can be inadvertently moved through idle to the cutoff position.
(xil) Switches, buttons, or other controls which can be inadvertently activated during routine cockpit activity including cockpit entry.
(xili) Failure to account for operation with the pilot wearing bulky winter clothing.
(xiv) Aft cyclic movement limited by the pilot's body with a fore and aft adjustable seat in the full forward position.
334. § 27.779 (Amendment 27-21) MOTION AND EFFECT OF COCKPIT CONTROLS.
a. Explanation. The section standardizes motion and effect of cockpit controls.
While this paragraph specifically addresses primary flight controls, engine power Par 333 411
controls, and landing gear controls, it applies to all cockpit controls not addressed in other paragraphs.
b. Procedures.
(1) The cyclic should be mechanized such that movement of the control results in a corresponding sense of aircraft motion in the same axis. While a certain amount of coupling may be present following a pure control input in a given axis, that coupling should not be objectionable to the pilot. Collective pitch control should be mechanized such that an upward movement of the collective results in a corresponding relative motion of the aircraft in the vertical plane. Again, coupling should not be objectionable.
Care should be taken to insure that the primary pilot's perception of collective motion is in the vertical plane. The objective is to clearly differentiate collective motion from that associated with an airplane throttle. The rule is self-explanatory on the subject of engine power controls. A distinction is made between normal landing gear controls and emergency controls. Emergency controls may operate in a sense which might not correspond to the direction of resultant gear motion.
(2) The recommended operating convention and "switchology" for miscellaneous controls are:
Up/forward = on/increase (ії) Down/aft = off/decrease
(il) Variable rotary controls should move clockwise from the OFF position, through an increasing range, to the full ON position. For some variable intensity controls such as instrument lighting, the desired minimum setting may not be completely off. Pushbuttons not giving an obvious indication of mechanical position should be configured such that the flightcrew has a clear indication of switch actuation under both day and night (if applicable) conditions. Failure of the indication should be shown to be free of hazards.
(3) Slew or "beep" switches associated with flight control system applications warrant special attention. The recommended conventions for control-mounted single, or multifunction, two or four-way "beep" switches are:
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(i) Cyclic Flight Control System Switch Direction /Autopilot Configuration Aircraft Response forward/up basic trim nose down airspeed/groundspeed increased airspeed mode selected forward speed reference vertical speed mode increased rate of selected (without descent/decreased airspeed mode engaged) rate of climb hover mode selected increased groundspeed or forward acceleration reference left basic trim left wing down heading mode selected slow heading reference left hover mode selected increased groundspeed or acceleration reference to left (¡i) Collective (assumes switch is mounted on top of grip).
Flight Control System Switch Direction /Autopilot Configuration Aircraft Response forward control position hold down collective vertical speed mode increased rate of selected descent/decreased rate of climb hover mode selected decreased hover height reference left control position hold increase left pedal hover mode selected slow heading reference left Par 334 413
AC 27-1A 7130/97
(iii) Opinions are divided concerning the preferred convention for forward and rearward motion of slew switches mounted atop the collective grip. Part of the reason appears to stem from the fact that such a switch is never used in a purely control position trim capacity. The switch has normally remained nonfunctional until a vertical autopilot mode is selected. At that point, the switch is viewed by one pilot/engineer contingent as either an autopilot reference slew function or a power increase/decrease switch which should follow the "forward equals increase" convention.
The other group views the switch as a form of control position trim and finds the "forward equals down collective" convention to be more consistent with the sensing used for the cyclic beep switches. An obvious solution is to mount collective/vertical axis switches in a vertical orientation on the grip. Barring that alternative, viable arguments can be made for either philosophy. The recommended convention was selected following a survey of manufacturers and test pilots.
335. § 27.783 DOORS.
a. Explanation.
(1) Closed cabins must have at least one external door that is adequate and easily accessible for all of the occupants. The standard envisaged a door intended for normal use and for an emergency exit for all passengers. The passenger compartment, itself, should not be partitioned.
(2) Passenger doors should not be located near main or tail rotors such that persons using the door or doors would be endangered while entering or leaving the aircraft. The discs of engines or other propulsion system devices were not included in this standard. Procedures or instructions may be used to support compliance.
Section 27.1565 concerns tail rotor markings.
(3) Cabin doors of normal category rotorcraft should inherently comply with the exit standards in § 27.807(b) concerning the size of the unobstructed opening, accessibility, location, method of opening, arrangement, probable jamming due to fuselage deformation, and possibly markings inside and outside. The standards for the features and characteristics of exits should be applied to cabin doors unless an "exit" is also installed in the same side of the fuselage. The marking standards of § 27.1557(d) for exits should be applied to doors unless the door is readily identified and its opening features are simple and obvious. It is not necessary to use red and white colors, provided the door instructions and markings are conspicuous.
(4) If the door is used as a "ditching exit," the threshold of the door/exit must be above the waterline of the rotorcraft while in calm water (§ 27.807(d)). Note that "ditching approval" under § 27.801 is an optional standard.
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(5) If a lock is used as an optional feature, the lock must not engage inadvertently or, as a result of mechanical failure, prevent possible opening of the door from inside or outside the cabin.
b. Procedures.
(1) The layout of the most dense or critical (from evacuation aspect) interior arrangement should be reviewed as soon as possible in the certification program. Each passenger shall have easy access to each passenger door/exit. The crewmembers may have separate emergency exits or doors on each side of the aircraft separate from the passenger door if desired by the applicant. A mockup may be used to make an early assessment of the interior critical areas for door accessibility, operation of the door, door markings, and other features critical to compliance. A comprehensive interior compliance inspection may be accomplished later in the program to confirm or correct conclusions derived from a review of layout or mockup data.
(2) Mockup interiors used in the preliminary evaluation may not have all padding, liners, compartments; i.e., it may not be a fully equipped interior arrangement.
(3) The door should have clearance with the fuselage door frame to allow reasonable deflection without jamming, or the door may be designed to minimize jamming. So called "rip hinges" may be employed as well. Rip hinges may also serve as the primary emergency release for the door.
(4) If a door has an emergency release system for the door that is separate from a "normal open and close" system, certain standards of § 27.807(b) and (c) should apply.
(5) As good practice, internal and external markings are recommended for each door as tollows:
Indicate when the door is closed and fully locked.
(її) Indicate the means of opening.
(ili) Contrasting colors should be used in markings. Red and white are acceptable but not required. For exit markings, see § 27.1557(d).
(6) Crew and passengers should be protected from the main and tail rotors (discs) as prescribed in § 27.807(b). Two avenues of compliance are noted here.
A layout of the aircraft may be used to evaluate compliance with § 27.783(b). The main rotor should have sufficient clearance to allow a typical person to stand upright, outside, near the door or doors. The auxiliary rotor should be located as far as practicable from any passenger doors. Appropriate instructions for entering or Par 335 415
leaving the rotorcraft may be furnished in the flight manual, placards, or equivalent to further reduce possible hazards. Tail rotor marking standards are referenced in Paragraph 751 of this advisory circular.
(ii) If necessary, a door and engine or rotor system interlock system may be employed to prevent opening of the door with the rotors operating. Other systems may be used. In case of emergency, the system must allow opening of the door (exit) from inside or outside the rotorcraft.
335A. § 27.783 (Amendment 27-26) DOORS.
a. Explanation.
(1) Each closed cabin should have at least one door. A door on the opposite side of the cabin may be used to also comply with the exit requirement of § 27.807.
(2) Amendment 27-26 extends the requirements of § 27.783 to:
- include each external door, not just passenger doors; and,
- require provisions of door location and procedures to protect persons from danger from propellers, engine intakes, and engine exhausts.
b. Procedures. All of the policy material pertaining to this section remains in effect. In addition:
(1) Occupants of the rotorcraft and servicing personnel should be protected from possible injury when using any external door to enter or egress the rotorcraft and when loading cargo or servicing the rotorcraft. Consideration should be given to door location and operating procedures to include protection from propellers (if equipped) and engine inlets and exhausts, as well as from rotors.
(2) These new requirements clarify that engine exhausts, engine inlets, and propellers, as well as rotors, are potentially hazardous and should be located or designed to protect rotorcraft occupants and ground personnel.
(3) Door operating procedures, including readily visible markings, should be provided to minimize possible injury to personnel when practical component locations or component design features, alone, do not assure freedom from possible injury.
336. § 27.785 (Amendment 27-21) SEATS, BERTHS, SAFETY BELTS, AND HARNESSES.
a. Explanation.
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