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 is:
(i) Up/forward = on/increase.
(ii) Down/aft = off/decrease.
(iii) 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:
(i) Cyclic.
Switch Direction Flight Control System /Autopilot Configuration Aircraft Response Forward/up basic trim nose down airspeed/groundspeed mode selected increased airspeed forward speed reference vertical speed mode selected (without airspeed mode engaged) increased rate of descent/decreased rate of climb hover mode selected increased ground-speed or forward acceleration reference Left basic trim left wing down heading mode selected slew heading reference left hover mode selected increased ground-speed or acceleration reference to left Page D - 77
(ii) Collective (assumes switch is mounted on top of grip).
Switch Direction Flight Control System /Autopilot Configuration Aircraft Response Forward control position hold down collective vertical speed mode selected increased rate of descent/decreased rate of climb hover mode selected decreased hover height reference Left control position hold increase left pedal hover mode selected slew heading reference left
(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.
AC 29.783. § 29.783 (Amendment 29-20) DOORS.
a. Explanation. This regulation requires at least one door for all closed cabin rotorcraft. Standards for all doors and airstair doors are included. To assure that the doors provide normal entry and egress without causing or contributing to hazardous conditions, even after a minor crash, the following requirements are imposed:
(1) Passenger doors may not be located with respect to any rotor to endanger persons using the doors as instructed.
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(2) Means are required for locking crew and external passenger doors to prevent their opening in flight due--
(i) To inadvertent operation; or
(ii) To mechanical failure.
(3) External doors are required to be openable from the inside or outside by simple and obvious means.
(4) Reasonable provisions to prevent jamming of external doors are required as specified and to assure that an “airstair door” is useable.
(5) The following visual indications of external doors being closed and locked are required:
(i) Direct visual inspection means by crewmembers of the locking mechanism of all external doors.
(ii) Visual means to signal to crewmembers “when normally used external doors are closed and fully locked.”
(6) For certain outward opening doors, an auxiliary safety latching device is required “to prevent the door from opening when the primary latching mechanism fails.”
Suitable operating procedures to prevent this device from being used during takeoff and landing are required if the door cannot be opened from outside the rotorcraft (reference § 29.783(c)) with the device in place.
(7) If the door is a sliding door and intended to be opened and closed in flight, the sliding mechanism should positively attach the door to the airframe (e.g., sliding hinge) to minimize the likelihood of the door departing the aircraft in flight. Appropriate flight limitations should also be established to minimize any hazard while operating the door.
b. Procedures.
(1) Passenger doors should be located as far as possible from the auxiliary rotors. The doors may be hinged and door open stops may be provided to separate entering and egressing passengers from the auxiliary rotor blades. If necessary for the design, “appropriate instructions” should be provided for all passenger doors concerning entering and leaving the rotorcraft and safe use of each door relative to all rotors.
These instructions should be obvious to a passenger using the door, contain large enough letters to be readily legible, and use letters or background colors associated with danger (i.e. orange or red).
(2) Means to prevent the opening of doors in flight.
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AC 29-2C, Chg 3 9/30/2008
(i) Means to prevent the opening of doors in flight due to inadvertent operation may be provided by recessing door handles to prevent their inadvertent operation by the normal movement of passengers about the cabin. If recessing the door handle is impractical, a cover may be provided which will prevent inadvertent operation of the handle, but the cover should be of such design that it does not obscure the door handle or its operating instructions. It must not unduly interfere with deliberate operation of the door handle by passenger or crew. Transparent or nonsolid covers, easily displaced by deliberate actions, have been used to prevent inadvertent door handle operation. Some rotorcraft designs meet this requirement by requiring that passengers wear their seat belts at all times during flight. This design requires that the “fasten seat belt” sign be on at all times the rotorcraft is in flight (for practical purposes, the “fasten seat belt” light is generally designed to be on when power is applied to the rotorcraft).
(ii) Means to prevent inadvertent door opening in flight due to “mechanical failure” is most efficiently provided by multiple door latches and multiple load path door locking mechanisms so that the door will remain locked after a single failure. Care should be taken in the design of multiple load path latches and mechanisms to assure independence of all failures and to consider the effort of deflections after failures (if a failure allows deflections into the airstream sufficient to increase aerodynamic loads, the increase in loads should be accounted for; if a failure allows significant movement of latching components, the deflections should be accurately accounted for to assure that disengagement of nonfailed latches does not occur).
(3) The means to open normally used external doors is required to be simple (such as a rotating handle) and to be accessible from the inside or the outside. To prevent the inadvertent use of emergency exits (separate from normal entry doors) for routine entry and exit with the resulting “wear and tear,” the normally used doors for entry and exits should be equipped with operating handles and instructions distinctly different from those of the emergency exits. Obviously, the above does not apply to normally used exits which are also the primary (or only) emergency exits.
(4) Reasonable provisions to prevent jamming of external doors include the following:
(i) Design features of doors which are insensitive to large fuselage deflections for door operation.
(ii) Provision of clearance between door and door frame latching devices sufficient to allow some relative deflection between the door and door frame and still allow door operation. The relative deflections may be determined by static test or by an analysis approved by the FAA/AUTHORITY.
(iii) Sliding doors are frequently used in transport rotorcraft for versatility and utility reasons. If sliding doors are used, one of the following features of design may be required to assure that the requirements of § 29.783(d) are met:
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(A) The sliding door(s) must be provided with jettison features which allow release of the door(s) from the tracks (to preclude jamming). The emergency release is generally separate and distinct from the normal door handle.
(B) Separate emergency exits of appropriate size and number may be installed in the sliding door(s).
(C) Separate emergency exits of appropriate size and number may be installed in addition to the sliding door(s).
(iv) Whether or not the sliding door is qualified as an emergency exit, it must meet the remaining door design standards.
(5) Direct visual inspection means by crewmembers of the locking mechanism of external doors may provide for visual observation of the door frame and the latching components for engagement or for visual observation of “flag” areas of the locking mechanism. If “flag” areas are used (such as tabs or shoulders which protrude into the crewmember’s line of sight when the latches are engaged (locked)), care should be taken to assure that the tab is permanently affixed (or an integral part) to the locking mechanism; and it should not give erroneous readings to the crewmembers under any foreseeable operation or failure of the latching mechanism. “Visual means to signal” to crewmembers “when normally used external doors are closed and fully locked” may be provided by annunciator panel lights or equivalent means. The visual indicating system may consist of an indicator for each individual door, or a system connecting all doors in series. If the latter system is used, it need not necessarily show which door is not fully locked. It is not necessary that more than one crewmember be able to ascertain by a visual signal that all external doors normally used by the crew in supplying the rotorcraft, or in loading and unloading passengers and cargo, are fully closed and locked. The visual signal should be located so that it may easily be seen by the appropriate crewmember from his station.
(6) For § 29.783(f), the auxiliary safety latching device to “prevent the door from opening when the primary latching mechanism fails” can be provided by the same multiple load path features which meet the § 29.783(c) requirement for prevention of door opening in flight after a “mechanical failure.” If a completely separate “auxiliary safety latching device” is used, it should allow the door to be opened from the inside, or outside, when in place. If the device must be removed to allow use of the door, “suitable operating procedures” (i.e., placards and RFM instructions) will be required for removal of the device during takeoff and landing.
(7) Additional standards for “airstair doors” were added by Amendment 29-20.
(i) An analysis or test may be used to prove compliance with deformation standards in § 29.783(g)(1).
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AC 29-2C, Chg 3 9/30/2008
(ii) A sketch, drawing, or demonstration may be used to prove the door is useable for the conditions described in § 29.783(g)(2).
AC 29.783A. § 29.783 (Amendment 29-31) DOORS.
a. Explanation.
(1) Amendment 29-30 extends the requirements of § 29.783 to:
- include each external door, not just passenger doors; and,
- require provision of door location and/or door operation procedures to protect persons from danger from propellers, engine intakes, and engine exhausts. (Protection from rotors are already included in the standard.)
(2) Amendment 29-31 adds a new paragraph (h) to § 29.783 which requires for doors used for ditching egress to have a means to secure the “ditching exits” in an open position and remain securely open in the appropriate Sea State used for compliance with § 29.801, paragraph AC 29.801.
b. Procedures. The procedures of paragraph AC 29.783 continue to apply to § 29.783 (and Amendment 29-31) with the following additions:
(1) Occupants of the rotorcraft and servicing personnel are now required to be protected from 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/or operating procedures to include protection from propellers (if equipped) and engine inlets and exhausts, as well as from rotors.
(2) These new standards 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 or use door latching and operating procedures to protect those persons. Operating procedures for the door, including readily visible markings, should be provided to minimize injury to personnel when practical component locations or component design features, alone, do not assure possible freedom from injury.
(3) For § 29.783(h), a means such as a cable, chain, pin, or mechanical linkage should be provided to secure doors used as ditching exits in the open position. The means should be shown to be effective under rotorcraft attitudes and dynamic conditions common to ditching. The sea states for ditching approval in accordance with § 29.801 are found in paragraph AC 29.801. Demonstrations under actual ditching conditions are not mandated for substantiation purposes, but the substantiation methodology should be reliable, i.e., an analytical or test method demonstrated to be reliable and used in previous structural substantiation programs.
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AC 29.785. § 29.785 SEATS, SAFETY BELTS, AND HARNESSES.
a. Explanation.
(1) This section requires that seats, belts, harnesses, and adjacent parts of the rotorcraft be substantiated for the structural loads resulting from the inertia forces of § 29.561 as well as normal flight and ground inertia forces on a 170-pound occupant.
The inertia forces of § 29.561 are ultimate loads and must be multiplied by a factor of
1.33 in determining the “strength of attachment” of each seat to structure and each belt or harness to structure. The seat, belt, etc., are required to sustain applied loads and to protect the occupant from serious injury. The pilot seats must also sustain the effects of the pilot forces of § 29.397.
(2) In addition, the “occupant must be protected from head injury” by the seat belt and one of the following:
(i) A harness to prevent the head from contacting an injurious object.
(ii) Elimination of injurious object within striking distance of the head.
(iii) A cushioned rest as specified.
(3) Handholds are required to steady occupants using the aisle in moderately rough air.
(4) Projecting objects which would injure occupants “in normal flight must be padded.”
b. Procedures.
(1) Each seat with its belts and harnesses are to be substantiated for the flight, ground, and emergency landing loads of § 29.561 by structural test or stress analysis.
Section 29.785(b) states that “each seat must be approved.” Certification approval can be gained by Technical Standard Order (TSO) approval or by accomplishing sufficient structural substantiation to gain FAA/AUTHORITY approval of the seat and its belt(s) as part of the Type Design of the rotorcraft. TSO No. C-39 concerns standards for aircraft seats, including rotorcraft seats. If TSO No. C-39 is used as an approval basis for a specific rotorcraft seat, the seat should be checked to assure it has been substantiated for the vertical (up and down) and side loads imposed by installation in the aircraft. For example, TSO No. C-39 (and NAS 809) specifies an ultimate down load of 4.0g which is in agreement with the 4.0g emergency landing load factor of § 29.561, but it may be less than the design maneuver load factor (which can be as high as 3.5g limit or 5.25g ultimate).
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(i) The 1.33 factor is specified for substantiation of attachments of each seat to the structure and each safety belt or harness to the seat or structure for § 29.561 loads, whether analysis or test is used.
(ii) If static testing of seats, belts, and harnesses is used, the body block of NAS 809 may be used. The corners of the NAS 809 body block may be radiused and padded if it is found that the small radii cause premature, unrealistic crippling of thin wall tubing or other structure used in the seat.
(iii) The substantiation of the pilot seats is required to include pilot forces of § 29.397 in conjunction with normal flight and ground loads. For example, the pilot foot force (195 pounds ultimate) must be reacted by the seat.
(2) The following criteria have been found satisfactory for preventing occupant head injuries:
(i) If a harness is used, it should support the shoulders without applying hazardous loads to the side or front of the neck. It should be easily donned and a single point release with the seat belt is preferred. If separate release is provided, it must be simple, compatible with the seat belt release, and near the seat belt release. The harness should be tested in conjunction with the seat belt using a “body block” similar to that of NAS 809 if possible. If the harness is tested separately from the belt, it should be tested to 50 percent of the forward crash loads for the entire occupant weight of 170 pounds, unless that percentage distribution is found to be unrealistic by a rational analysis.
(ii) Elimination of injurious objects within striking distance of the head and other vital parts can be accomplished by removal of objects with sharp edges or rigid surfaces from within striking distance of vital parts of the occupant. Dimensions and weights for typical occupants are available in U.S. Army USAAULABS Reports 70-22 (August 1969) and 66-39 (June 1966) and NACA Report TN 2991 (August 1953).
Because of the range of occupant head striking distance, a combination of “elimination of injurious objects” and “cushioned rests” may be required for some interior configurations.
(iii) An acceptable cushioned rest can be provided by use of a 1-inch thickness of foamed polyvinyl chloride (PVC), or equivalent energy absorbing material.
The density of material should be in the 5 to 10 pounds per cubic foot density range.
PVC foam has the property of absorbing energy efficiently with negligible rebond effects. PVC foam recovers slowly to the original configuration after deformation. If PVC foam is used, however, care must be taken in its application relative to its flammability characteristics (reference § 29.853).
(3) Handholds for the occupants are generally provided by seat backs adjacent to the aisle. If the seat backs fold, the amount of support provided by the seat backs before they fold must be evaluated in a furnished interior or mock up. To provide Page D - 84
adequate support, the seat back may use an easily disengaged latch or adequate friction in the hinge mechanism to obtain adequate support. Handholds along the aisle are, of course, not needed for rotorcraft with no aisles or where seat belts must be fastened during flight.
(4) Projecting objects which could injure occupants in normal flight should be padded. The amount of padding required depends on the location, size, and minimum radius of the projecting object. In general, this requirement will mean that sharp edges must be padded with one-half inch of PVC foam or equivalent (5 to 10 lbs. density), while objects with radii in excess of 1 inch may meet the requirements of § 29.785(e) with a lesser amount of energy absorbing padding, if it can be contacted only by persons “moving about in the rotorcraft in normal flight.”
AC 29.785A. § 29.785 (Amendment 29-29) SEATS, BERTHS, BELTS, SAFETY BELTS, AND HARNESSES.
a. Explanation. Amendment 29- 29 makes the following changes to § 29.785:
(1) The title of § 29.785 now includes berths (which would include litters).
(2) Section 29.785(a) has been revised to include reference to the new § 29.562, “Emergency Landing Dynamic Conditions.”
(3) Section 29.785(b) has been revised to include a reference to the new § 29.562(c)(5) head injury criteria and to describe a torso restraint system that is contained in TSO-C114.
(4) Section 29.785(f) has been revised to change the percentage of load distribution for safety belt and harness combination to 60-40.
(5) A new § 29.785(i) has been added which provides a list of “seating device system” components.
(6) A new § 29.785(j) provides for deformations of the seat energy absorption device system installed to meet the requirements of § 29.562 but requires that the system “remain intact and not interfere with rapid evacuation of the rotorcraft.” Further “structural” performance standards are contained in §§ 29.562(c)(1) and (2).
(7) A new § 29.785(k) provides static strength and restraint requirements for litters and berths. Litters may be oriented laterally as well as longitudinally in the rotorcraft. Dynamic tests of litters are not required. For longitudinally oriented litters, features should be provided to protect the occupant from the increased loads in § 29.561(b) of Amendment 29-29.
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AC 29-2C, Chg 1 2/12/03
b. Procedures. The procedures of paragraph AC 29.785 still apply to static substantiation of the seats, berths, safety belts, and harness. In addition:
(1) Compliance with § 29.562 (except litters are not included) and § 29.561(b) is required.
(2) Section 29.562 includes a specific pass fail criteria, which includes head injury criteria.
(3) Shoulder harnesses need only be substantiated for 40 percent of total occupant load rather than the former 60 percent adopted by Amendment 29-24.
(4) AC 29.562 provides guidance for evaluating the functioning of a seating energy absorption device system under dynamic test conditions. Stroking is associated with the vertical-horizontal impact case and is recognized in the static strength substantiation.
(5) Berths or litters installed within 15° or less of the rotorcraft longitudinal axis (oriented longitudinally) shall use a combination of restraint devices, such as are required to be equipped with a padded end-board, cloth diaphragm, or equivalent means to withstand and distribute the occupant loads resulting from § 29.561(b) requirements. Other berths or litters may be equipped with straps or safety belts to withstand the forward reaction of § 29.561(b) as well as other loads, including flight loads.
(i) Berths/litters may be substantiated by static load tests, analysis, or a combination thereof and need not be substantiated to the 1.33 fitting factor of seat installations.
(ii) The berth/litter occupant’s head, neck, and spine should be protected from (landing) impact forward loads by appropriate design means; e.g.,
• non-longitudinal orientation of the berth/litter; or
• “feet forward” orientation; or
• distribution of an appropriate percentage of forward loads on the shoulders (not solely to the head and spine).
(iii) Recommendations for litter occupants:
• If the occupant’s head is oriented forward, a shoulder harness should be provided, in conjunction with body and leg straps that prevents the occupant’s head from falling off the litter. A padded end board, diaphragm, etc., may be used, provided head and spinal loads are alleviated or prevented.
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If the occupant’s feet are oriented forward, the padded end board may also be used in combination with the body and leg straps or other such restraints.
Multiple or combinations of devices should be used to distribute the occupant loads as well as protect the occupant from possible neck and spine compression.
AC 29.785B § 29.785 (Amendment 29-42) SEATS, BERTHS, LITTERS, SAFETY BELTS, AND HARNESSES.
a. Explanation. Amendment 29-42 revised the title of the rule to now include litters to distinguish from berths. Additi onally, § 29.785(k) was revised to require that the 1.33 fitting factor of § 29.625(d) must be applied to the emergency landing loads of § 29.561(b)(3) for the substantiation of attachments of each berth and litter to the structure.
b. Procedures. All of the advisory material pertaining to this section remains in effect with the following additions:
(1) A fitting factor of 1.33 must be applied to the emergency landing loads of § 29.561(b) when evaluating the berth or litter attachment and the occupant restraint system to the structure.
(2) The 1.33 factor is required whether analysis or test is used.
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AC 29-2C, Chg 4 5/1/2014 AC 29.787. § 29.787 (Amendment 29-12) CARGO AND BAGGAGE COMPARTMENTS.
a. Explanation.
(1) This section requires that cargo and baggage compartments be designed for normal flight and ground loads and for a 4g ultimate forward load condition.
Maximum placarded weights and critical distributions are to be considered.
(2) Means to prevent cargo shifting and contact between any cargo lamp bulb and cargo is to be provided.
b. Procedures. Structure tests or anal yses may be used for substantiation for the design loads.
(1) Nets or straps may be used to prevent cargo shifting. The nets or straps are required to be substantiated for the structural loads. They need a means for adjustment to assure proper restraint for different sizes and shapes of cargo.
(2) Cargo lamp bulbs need to be guarded, recessed, or placed in upper inside corners to prevent contact with cargo.
AC 29.787A. § 29.787 (Amendment 29-31) CARGO AND BAGGAGE COMPARTMENTS.
a. Explanation. Amendment 29-31 adds two subparagraphs to § 29.787 (c) which clarify that cargo and baggage compartments should be designed to protect occupants from injury by the compartment contents during emergency landings. This may be done by location or by retention provisions. The new paragraphs also add a requirement that the compartment contents should not cause injury when subjected to the loads of § 29.561.
b. Procedures. The procedures of paragraph AC 29.787 are still applicable. In addition to the forward load, the cargo and baggage compartments should be designed to withstand loads in other directions as specified in § 29.561. Also, the compartment may be shown to provide protection of occupants by location; i.e., cargo and baggage compartments may be shown to be located in a position where loose contents will not endanger occupants in an emergency landing. If the compartment is located above or behind the occupied area, § 29.561(c) still applies. If a compartment is in the occupied area, § 29.561(b) may apply.
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