97 airplane shall be found by the Administrator to perform adequately the functions for which it is to be used, shall function properly when installed, and shall be adequately labeled as to its identification, function, operational limitations, or any combination of these, whichever is applicable.”
Before Amendment 23-20 (which became effective September 1, 1977), § 23.1301 contained essentially the same requirement as CAR 3.652.
Amendment 23-20 deleted the words “essential to safe operation” and made the provisions of § 23.1301 applicable to “each item of installed equipment.”
We conclude from these rules that if a shoulder harness is not required equipment, it is not essential to the safe operation of the airplane; therefore, CAR 3.652 and § 23.1301, before Amendment 23-20, should not be used as a basis to prohibit shoulder harness installation by minor change. These rules should be applied to shoulder harness installations made by STC and Field Approval.
The mechanic making such installations should consult AC 43.13-2A, Chapter 9, for information on restraint systems, effective restraint angles, attachment methods, and other details of installation.
See AC 21-34, Shoulder Harness-Safety Installations, AC 21-25A, Approval of Modified Seats and Berths Initially Approved Under a Technical Standard Order, and AC 43.13- 2A, Acceptable Methods, Techniques, and Practices—Aircraft Alterations.
Aft-facing and side-facing seats For aft-facing seats, seat obliqueness should be limited to 15° unless additional occupant protection for side-facing seats is installed.
Part 23 permits side-facing seats, but it does not address the crashworthiness problems of these installations. We recommend that side-facing seat installations be discouraged. If such an installation is made, the following should be applied in addition to any applicable rules from the original certification basis:
a. A sideward facing seat is defined as one in which the plane of symmetry of the occupant makes more than an 18° angle with the vertical plane containing the airplane centerline when viewed from above.
b. Each occupant of a sideward facing seat should be protected from serious head injury when experiencing the inertia forces of § 23.561(b)(2) by either a safety belt and energy absorbing rest that will support the head and torso or by a safety belt and shoulder harness that will prevent the head from contacting any injurious object.
There should be adequate padding on any restraining bulkhead. Riding up of diagonal
98 shoulder straps on the neck, which could cause neck injury, and location of attachments and rigidity of the seat support that could cause twisting and compression of the spine should be considered. For a multiple side-facing seat, a passenger seated immediately forward of another passenger cannot be considered an energy absorbing rest (human cushion).
c. Sideward facing seat installations that do not comply with paragraph “b.” above should be placarded to prohibit occupancy during takeoff and landing. In any case, the side-facing seats still require one seat belt for each passenger to protect against inflight turbulence, and the berth should be considered an item of mass for emergency landing conditions of § 23.561.
d. Special conditions will be required for sideward facing seats that are to be occupied during takeoff and landing when the certification basis requires compliance with § 23.562, Emergency landing dynamic conditions.
Seat Removal for Parachute Operations This guidance is intended for engineering assistance in the field approval process, Type Certificate (TC) approval or Supplemental Type Certificate (STC) approval of sport parachute modifications to small airplanes. The Small Airplane Directorate has received National Transportation Safety Board (NTSB) recommendations regarding the safety record of small airplanes that have been modified for use in sport parachute operations.
Most of these modifications have been approved by FAA Form 337 Field Approvals without engineering assistance. These modifications should either be approved by the TC process, STC process or by a field approval with engineering assistance. Aircraft Certification Offices (ACO's) should not provide engineering assistance for sport parachute modifications that change the limitations of an airplane or affect primary structure, required systems and equipment, handling, crashworthiness or performance. They should be completed using an STC or TC.
The acceptability of sport parachute operations is given in operational regulations. 14 CFR part 91 allows the use of the cabin floor for sport parachute operations and requires the operations be conducted per 14 CFR part 105. Part 105 requires radio equipment for operations in controlled airspace, but there are no other equipment requirements other than the parachutes. Advisory Circular AC 105-2C, Sport Parachute Jumping, gives information on complying with the regulations and provides a list of airplanes that may be operated with one cabin door removed. The part 91 regulation means floor seating is acceptable only for sport parachute operations, but this does not mean that the crashworthiness of the airplane can be unacceptable or that an unsafe condition can be created by a modification.
99 The small airplane certification bases are mostly Civil Air Regulation (CAR) 3 or early part 23. The modifications include the following: seating capacity increases, seat and restraint removal and replacement belt installation, door removal for airplanes not listed in AC 105-2C, step and hand holds on airplane exteriors, gross weight increases and center of gravity (CG) changes.
Seating capacity increases can be acceptable if all persons are protected in emergency landing loads per § 23.561 (3.386), all persons are secured against sliding backwards in climbs to maintain an acceptable CG position, and any changes in allowable CG range and increased gross weight are found acceptable. The applicant should also supply data to show that emergency exits are not crowded in a ground evacuation with the increased seating capacity per § 23.807 (3.387). This test/analysis must be done with all occupants except one representing a pilot in a parachute, and all parachutists initially restrained in place by the replacement belts/restraints.
Removal of certified seats, seat belts and shoulder harnesses, if any, is allowable per part 91, § 91.207(a)(3)(ii). This does not remove the requirement to prevent an unsafe condition in an emergency landing or normal operations. The replacement belts/restraints should, therefore, meet the requirements for emergency landing upward, forward and sideward loads, per § 23.561 (3.386), and secure all persons against sliding backwards in climbs to maintain an acceptable CG position. Per § 23.785 (3.390), the attachment of the replacement belts/restraints to structure must have a factor of 1.33 times the emergency landing loads in § 23.561 (3.386). A simple belt that fastens across the lap of a person sitting on the cabin floor is not acceptable. This prevents movement only in the direction the person is facing. For instance, facing to the rear (as has been reported) prevents movement toward the tail in a climb, but it does not secure a person against uncontrolled movement toward the front in an emergency landing. The FAA and the United States Parachute Association (USPA) have tested a pair of adjustable belts attached to the parachute harness and found that they are more effective in providing restraint while the emergency-landing forces dissipate. We find it acceptable, therefore, for a parachutist to use adjustable belts instead of the seat belt. Acceptable restraint systems for floor seating of sport parachutists are given by the Civil Aeromedical Institute (CAMI) of the FAA in Report DOT/FAA/AM-98/11, Evaluation of Improved Restraint Systems for Sport Parachutists, dated March 1998. The dual-strap restraints (5D, 6D and 7D) provided the least flailing and bending of body segments and the least forward translation of the pelvis.
ACO's should require one of these restraint systems for any TC, STC or engineering assistance to a field approval. Limitations should be imposed to call out the three operational procedures on Page 21 of the CAMI Report.
The dual strap restraints have been tested with floor attachments. To date, there has not been any acceptable testing of a sidewall attachment. An applicant who wants to attach a restraint system to a sidewall will need to perform sled testing per an approved procedure to verify its suitability in the emergency landing loads.
100 An acceptable procedure for use of the dual-strap restraints (5D, 6D and 7D) is as follows:
a. Sit on the aircraft floor between two seat rails facing aft.
b. Attach two adjustable belts to your parachute harness per either the 5D, 6D or 7D configuration. You may loop the adjustable belt through your parachute harness webbing or you may attach a quick-release clip through the ring on your harness.
c. Attach the other end of each harness to the seat rail in the aircraft floor. Make the attachment to the floor rail on the same side as the attachment to your harness.
d. Adjust the belt as snugly as possible without causing discomfort.
Note: If possible, place a lap belt attached to the floor rails around your upper legs to prevent flailing during the emergency landing.
Door removal raises issues in Subpart B of 14 CFR part 23. Performance, stability, and control must be found acceptable with the door removed in flight. If the Airplane Flight Manual gives performance numbers such as takeoff and takeoff over a 50 foot obstacle, the applicant should verify that performance or issue a Flight Manual Supplement with the revised numbers. Of course, the applicant does not have to present any data or do any tests for airplanes that are listed in AC 105-2C.
Steps and handholds to be installed on the exterior of a small airplane should be shown to meet the structural strength and fatigue requirements in part 23 (CAR 3). Carriage of parachutists outside the aircraft must be shown to not be hazardous in a power loss failure in takeoff and climb flight phases.
Increases in gross weight and allowable CG range should be shown to comply with the requirements in part 23 (CAR 3) as would any other modification that affected these numbers.
Aircraft modified for sport parachute operation must include a placard or flight manual limitation that prohibits flight with doors or seats removed except in sport parachute operation.
Amendment 23-7 and Subsequent AC 23-28, when issued, will provide information and guidance applicable to the static strength substantiation of the attachment points for occupant restraint system installations, which have both a safety belt and shoulder harness.
101 Amendment 23-36 and Subsequent See guidance for § 23.562, Emergency landing dynamic conditions.
Part 23 did not envision more than two seats on the flight deck, although the part does not prohibit such an installation. The airworthiness standards do not contain adequate standards for an “observer” seat (occupied by an FAA Flight Standards inspector on commuter flights). Therefore, we would expect to apply special conditions to such an installation that would address occupant restraint, emergency egress, and appropriate placarding to prohibit use by a passenger under any circumstances. The special conditions should establish a level of safety equivalent to that established in the certification basis of the airplane, not only for the observer seat occupant but also the crewmember seated in front of the occupant.
The weight of a parachute is included in the 215-pound occupant weight if a parachute is required. The weight remains at 215 pounds when a parachute is not required.
23.787 Baggage and cargo compartments Original Issue and Subsequent Questions have been raised regarding § 23.787(c), which requires an ultimate inertia forward force of 4.5g for the protection of passengers from any cargo compartment. This regulation is related to Civil Air Regulations, which envisioned a crew compartment forward, a passenger compartment in the middle, followed by a bulkhead and a small cargo/baggage compartment aft. In this concept, the 4.5g was considered adequate based on NASA data that showed g forces become less as distance from the nose increases in a typical crash. Our review of all cargo configurations has led to the conclusion that under § 23.561(b) and (e), the restraining devices should meet the 9g requirements. The up and side load inertia forces are not considered to be applicable in this case where the crew would not be subject to injury from upward or sideward cargo movement.
To modify a passenger plane to an all-cargo configuration, the following items should be considered:
a. The cargo compartment should meet the requirements of § 23.787. Special attention should be given to cargo loading placards and the cargo restraint system.
b. The cargo restraint system, including tie downs and the supporting structure to which they are attached, should be substantiated to the emergency landing ultimate inertia forces in § 23.561(b)(2).
c. The floor loading should be re-substantiated to ensure the floor structure is not overloaded.
d. Emergency egress from an emergency exit or the entrance door should be verified accessible for the crew.
e. A supplement to the Airplane Flight Manual (AFM) weight and balance section that shows the various permissible cargo loading arrangements and cargo restraints should be furnished.
Guidance on Carriage of Hazardous Cargo for Operators of part 23 Certificated Aircraft There are no 14 CFR part 23 airworthiness standards that directly address the design of an aircraft to allow for the carriage of hazardous cargo and passengers simultaneously. We cannot, therefore, provide guidance on the issuance of Amended Type Certificates (ATC’s) or Supplemental Type Certificates (STC’s) specific to this kind of operation.
103 However, for the carriage of cargo and baggage in general, 14 CFR part 23 does provide certification requirements for baggage and cargo compartments. Specifically, § 23.787 “Baggage and cargo compartments,” which focuses on the design requirements of the baggage or cargo compartment and its integration with the airframe.
§ 23.855 “Cargo and baggage compartment fire protection” focuses on the shielding, insulation, and flammability requirements of cargo or baggage containers. In addition, this regulation adds additional requirements and tests on cargo and baggage compartments for use in commuter category aircraft.
Title 49, § 175.85, states that hazardous materials may be carried in a main deck cargo compartment of a passenger aircraft provided the compartment meets all certification requirements for a Class B aircraft cargo compartment as defined in 14 CFR part 25, § 25.857.
The certification requirements for Class B cargo compartments exceed the requirements identified in §§ 23.787 and 23.855. Normally, a Class B cargo compartment is not a certification requirement for a part 23 certificated airplane. However, a cargo compartment may be certificated, using either an ATC or STC process possibly involving special conditions, if it meets the appropriate airworthiness design standards for a Class B aircraft cargo compartment. Any ATC/STC effort must be coordinated with the responsible Aircraft Certification Office (ACO).
Once approved, a Class B cargo container installation in a part 23 certificated aircraft does not necessarily entitle the operator to carry hazardous cargo. The operator must also demonstrate compliance with the appropriate operational rules and requirements of 14 CFR part 135 and Title 49 governing the carriage of hazardous cargo. For additional information on part 135 requirements, we recommend the operator contact their local Flight Standards District Office (FSDO).
Amendment 23-14 and Subsequent See AC 23-2, Flammability Tests.
Amendment 23-36 and Subsequent The rigid moveable/removable cargo restraint bulkhead attached to seat rails and to points along the cabin sidewalls and roof is considered a structure per § 23.787(c). Prior to this amendment, the loads to design this structure were not defined, but the loads for a cargo restraint system and tie downs in a cargo compartment had to withstand an ultimate inertia force of 4.5g. Even though not defined, some certification programs applied a 4.5g ultimate load factor to design a rigid moveable/removable cargo restraint bulkhead in the
104 cabin. The rationale was to bring the sum of occupant protection to a 9g forward load. In this amendment, the ultimate forward load factor for any cargo restraint system and tie downs has been increased to 9g. In this case, the structure can be designed to no load since the occupant protection of 9g has been met by the cargo restraint system and tie downs.
If this structure separates the occupant compartment from the cargo compartment, only § 23.787(c) applies. Section 23.787(b) is applicable if cargo is carried aft of the occupants in the same occupant compartment. The ultimate load factor in § 23.561 has been increased to 18g by Amendment 23-36.
23.791 Passenger information signs No policy available as of June 30, 2001.
23.803 Emergency evacuation Amendment 23-34 and Subsequent See AC 20-118A, Emergency Evacuation Demonstration, for information on how to conduct an emergency evacuation demonstration of a commuter category airplane.
If there is a project for a litter installation for non-ambulatory passengers, then the airplane should be evaluated for compliance with the applicable egress requirements for those passengers who can exit the airplane under their own power per § 23.803. This evaluation can be a simple engineering judgment if it is clear the litter installation will not prevent the safe egress of all non-litter passengers within the allotted time. If there is doubt, a new demonstration should be run that evaluates the ability of non-litter passengers to exit the airplane with special attention to the litter installation and possible obstructions to safe exit.
Amendment 23-46 and Subsequent This amendment adds a requirement for emergency lighting per § 23.812 to be the only lighting used in an emergency evacuation demonstration when certification of emergency exits is done per § 23.807(d)(4). AC 20-118A is still applicable with the exception of paragraph 5a(3)(vi).
23.805 Flight crew emergency exits Amendment 23-46 and Subsequent Section 23.805 requires two crew compartment exits or a singular hatch if the passenger exits are not convenient and readily accessible to the crew, while § 23.807(a)(3) requires a single crew compartment exit if there is a door that is likely to block the crew's access to the passenger exits. If a crew compartment exit is necessary under § 23.807(a)(3), the more stringent requirements of § 23.805 are also applicable. In other cases, the crew compartment exits may be required by § 23.805 independent of § 23.807(a)(3). Crew compartment exits that comply with the requirements of § 23.805 would also comply with § 23.807(a)(3) without further showing.
Amendment 23-49 and Subsequent Crew compartment exits that comply with the requirements of § 23.805 would provide an equivalent level of safety to § 23.787(c). According to the preamble to Amendment 23- 49, which added § 23.787(c), “this requirement would provide increased assurance that flight crews of all cargo airplanes will have ready access to an emergency exit.”
23.807 Emergency exits Original Issue and Subsequent “Seating Capacity” as used in this regulation is defined as the number of occupants, both crew and passengers, for which the airplane is certificated. Consequently, removal of installed seats is not justification for removal of certificated emergency exits.
The regulation requires a clear and unobstructed opening. An exemption per 14 CFR part 11 to § 23.807(b) is acceptable for a seatback that protrudes into the opening if it can be easily pushed forward to clear the exit without requiring an action to unlock/unlatch the seat. If a seatback clears the exit when upright but not when reclined, it is acceptable to placard the seat to be upright during takeoff and landing.
Emergency exits should be located to allow escape without crowding in any probable crash attitude. The inverted position is considered probable for both tail wheel and tricycle gear airplanes. This applies to airplanes with doors, forward sliding canopies, rearward sliding canopies and jettisonable canopies. If escape in an inverted attitude is not obvious or is questionable, then compliance should be demonstrated.
It is not acceptable for certification purposes, except for acrobatic airplanes (§ 23.807(b)(5)), to rely on an emergency procedure requiring canopy jettisoning before an accident occurs. Regarding the acrobatic category, if the canopy is not jettisonable, it should be shown that the canopy can be opened far enough in flight between VSO and VD to enable the occupants to safely exit the airplane. If jettisonable, it should be shown that the canopy trajectory will not cause injury to the occupants while separating from the airplane between VSO and VD. Also, if the canopy is jettisonable, it should be demonstrated that the airplane can be safely flown without the canopy, or that an inadvertent jettisoning is shown to be improbable.
Regarding doors between the pilot’s compartment and the passenger compartment that are likely to block the pilot’s egress in a minor crash landing, there should be an exit in the pilot’s compartment. This does not apply to curtains suspended from a rod at the top and made of flexible material without slats on any side.
Doors or folding doors with rigid-frangible materials may jam in a minor crash.
Acceptance of frangible doors can be shown by the evacuation procedure in paragraph
23.807(a) below or by the conditions for acceptance of rigid doors in paragraph
23.807(b) below. Rigid doors are only acceptable by placarding the doors to be latched in the open position for takeoff and landing, providing the conditions in paragraph
23.807(b) below are in compliance.