AC 29.801. § 29.801 (Amendment 29-12) DITCHING.
a. Explanation.
(1) Ditching certification is accomplished only if requested by the applicant.
(2) Ditching may be defined as an emergency landing on the water, deliberately executed, with the intent of abandoning the rotorcraft as soon as practical. The rotorcraft is assumed to be intact prior to water entry with all controls and essential systems, except engines, functioning properly.
(3) The regulation requires demonstration of the flotation and trim requirements under “reasonably probable water conditions.” The FAA/AUTHORITY has determined that a sea state 4 is representative of reasonably probable water conditions to be encountered. Therefore, demons tration of compliance with the ditching requirements for at least sea state 4 water conditions is considered to satisfy the reasonably probable requirement.
(4) A sea state 4 is defined as a moderate sea with significant wave heights of 4 to 8 feet with a height-to-length ratio of:
(i) 1:12.5 for category A rotorcraft.
(ii) 1:10 for category B rotorcraft with category A engine isolation.
(iii) 1:8 for category B rotorcraft.
The source of the sea state definition is the World Meteorological Organization (WMO) Table (see Figure AC 29.801-1).
(5) Ditching certification encompasses four primary areas of concern: rotorcraft water entry, rotorcraft flotation and trim, occupant egress, and occupant survival.
(6) The rule requires that after ditching in reasonably probable water conditions, the flotation time and trim of the rotorcraft will allow the occupants to leave the rotorcraft and enter liferafts. This means that the roto rcraft should remain sufficiently upright and in adequate trim to permit safe and orderly evacuation of all personnel.
(7) For a rotorcraft to be certified for ditching, emergency exits must be provided with visible markings and must meet the requirements of §§ 29.807(d) and 29.811(a).
(8) The safety and ditching equipment requirements are addressed in §§ 29.1411, 29.1415, and 29.1561 and specified in the operating rules (parts 91, 121, 127, and 135). As used in § 29.1415, the te rm ditching equipment would more properly be described as occupant water survival equipment. Ditching equipment is required for extended overwater operations (more than 50 nautical miles from the nearest shoreline Page D - 89
AC 29-2C, Chg 4 5/1/2014 and more than 50 nautical miles from an offshore heliport structure). However, ditching certification should be accomplished with the maximum required quantity of ditching equipment regardless of possible operational use.
(9) Current practices allow wide latitude in the design of cabin interiors and consequently, the stowage provisions for safety and ditching equipment. Rotorcraft manufacturers may deliver aircraft with unfinished (green) interiors that are to be completed by the purchaser or modifier. These various “configurations” present problems for certifying the rotorcraft for ditching.
(i) In the past, “segmented” certification has been permitted to accommodate this practice. That is, the rotorcraft m anufacturer shows compliance with the flotation time, trim, and emergency exit requirements while the purchaser or modifier shows compliance with the equipment provisions and egress requirements with the completed interior. This procedure requires clos e cooperation and coordination between the manufacturer, purchaser or modifier, and the FAA/AUTHORITY.
(ii) The rotorcraft manufacturer may elect to establish a “token” interior for ditching certification. This interior may subsequently be modified by a supplemental type certificate or a field approval. Compli ance with the ditching requirements should be reviewed after any interior configuration and limitations changes where applicable.
(iii) The rotorcraft flight manual (RFM) and supplements (RFMS) deserve special attention if a “segmented” certification procedure is pursued.
b. Procedures. The following guidance criteria has been derived from past FAA/AUTHORITY certification policy and experience. Demonstration of compliance to other criteria may produce acceptable results if adequately justified by rational analysis.
Model tests of the appropriate ditching configuration may be conducted to demonstrate satisfactory water entry and flotation and trim characteristics where satisfactory correlation between model testing and flight testing has been established. Model tests and other data from rotorcraft of similar configurations may be used to satisfy the ditching requirements where appropriate.
(1) Water entry.
(i) Tests should be conducted to establish procedures and techniques to be used for water entry. These tests should include determination of optimum pitch attitude and forward velocity for ditching in a calm sea as well as entry procedures for the highest sea state to be demonstrated (e.g., the recommended part of the wave on which to land). Procedures for all engines operating, one engine inoperative, and all engines inoperative conditions should be established. However, only the procedures for the most critical condition (usually all engines inoperative) need to be verified by water entry tests.
Page D - 90
(ii) The ditching structural design consideration should be based on water impact with a rotor lift of not more than two-thirds of the maximum design weight acting through the center of gravity under the following conditions:
(A) For entry into a calm sea--
(1) The optimum pitch attitude as determined in 337(b)(1)(i) with consideration for pitch attitude variations that would reasonably be expected to occur in service;
(2) Forward speeds from zero up to the speed defining the knee of the height-velocity (HV) diagram;
(3) Vertical descent velocity of 5 feet per second; and
(4) Yaw attitudes up to 15°.
(B) For entry into the maximum demonstrated sea state--
(1) The optimum pitch attitude and entry procedure as established in
(b)(1)(i);
(2) The forward speed defined by the knee of the HV diagram reduced by the wind speed associated with each applicable sea state;
(3) Vertical descent velocity of 5 feet per second; and
(4) Yaw attitudes up to 15°.
(C) The float system attachment hardware should be shown to be structurally adequate to withstand water loads during water entry when both deflated and stowed and fully inflated (unless in-flight inflation is prohibited). Water entry conditions should correspond to those established in paragraphs b.(1)(ii)(A) and (B).
The appropriate vertical loads and drag loads determined from water entry conditions (or as limited by flight manual procedures) should be addressed. The effects of the vertical loads and the drag loads may be considered separately for the analysis.
(D) Probable damage due to water impact to the airframe or hull should be considered during the water entry evaluations (i.e., failure of windows, doors, skins, panels, etc.).
(E) The ditching maximum demonstrated sea state for water entry is the same or greater than the maximum demonstrated sea state for flotation and trim.
(2) Flotation Systems.
Page D - 91
AC 29-2C, Chg 4 5/1/2014
(i) Normally inflated. Fixed flotation systems intended for emergency ditching use only and not for amphibian or limited amphibian duty should be evaluated for:
(A) Structural integrity when subjected to:
(1) Air loads throughout the approved flight envelope with floats installed;
(2) Water loads during water entry; and
(3) Water loads after water entry at speeds likely to be experienced after water impact.
(B) Rotorcraft handling qualities throughout the approved flight envelope with floats installed.
(ii) Normally deflated. Emergen cy flotation systems which are normally stowed in a deflated condition and inflated either in flight or after water contact during an emergency ditching should be evaluated for:
(A) Inflation. The float activati on means may be either fully automatic or manual with a means to verify primary actuation system integrity prior to each flight. If manually inflated, the float activation switch should be on one of the primary flight controls and should be safeguarded against spontaneous or inadvertent actuation for all flight conditions.
(1) The inflation system design should minimize the probability of the floats not inflating properly or inflating asymmetrically. This may be accomplished by use of a single inflation agent container or multiple container system interconnected together. Redundant inflation activation systems will also normally be required. If the primary actuation system is electrical, a mechanical backup actuation system will usually provide the necessary reliability. A secondary electrical actuation system may also be acceptable if adequate electrical system independence and reliability can be documented.
(2) The inflation system should be safeguarded against spontaneous or inadvertent actuation for all flight conditions. It should be demonstrated that float inflation at any flight condition within the approved operating envelope will not result in a hazardous condition unless the safeguarding system is shown to be extremely reliable.
One safeguarding method that has been successfully used on previous certification programs is to provide a separate float system arming circuit which must be activated before inflation can be initiated.
(3) The maximum airspeeds for intentional in-flight actuation of the float system and for flight with the floats inflated should be established as limitations in the RFM unless in-flight actuation is prohibited by the RFM.
Page D - 92
(4) The inflation time from actuation to neutral buoyancy should be short enough to prevent the rotorcraft from becoming more than partially submerged assuming actuation upon water contact.
(5) A means should be provided for checking the pressure of the gas storage cylinders prior to takeoff. A table of acceptable gas cylinder pressure variation with ambient temperature and altitude (if applicable) should be provided.
(6) A means should be provided to minimize the possibility of overinflation of the float bags under any reasonably probable actuation conditions.
(7) The ability of the floats to inflate without puncture when subjected to actual water pressures should be substantiated. A full-scale rotorcraft immersion demonstration in a calm body of water is one acceptable method of substantiation.
Other methods of substantiation may be acceptable depending upon the particular design of the flotation system.
(B) Structural Integrity. The flotation bags should be evaluated for loads resulting from:
(1) Airloads during inflation and fully inflated for the most critical flight conditions and water loads with fully inflated floats during water impact for the water entry conditions established under paragraph b.(1)(ii) for rotorcraft desiring float deployment before water entry; or
(2) Water loads during inflation after water entry.
(C) Handling Qualities. Rotorcra ft handling qualities should be verified to comply with the applicable regulations throughout the approved operating envelopes for:
(1) the deflated and stowed condition;
(2) the fully inflated condition; and
(3) the in-flight inflation condition.
(3) Flotation and Trim. The flotati on and trim characteristics should be investigated for a range of a sea states from zero to the maximum selected by the applicant and should be satisfactory in waves having height/length ratios of 1:12.5 for Category A rotorcraft, 1:10 for Category B rotorcraft with Category A engine isolation, and 1:8 for Category B rotorcraft. Model tests in a wave basin on a number of different rotorcraft types have indicated that an improvement in sea keeping, response of the rotorcraft to waves, performance of approximately one sea state can consistently be achieved by fitting float scoops. If the bas ic flotation system (without scoops) has Page D - 93
AC 29-2C, Chg 4 5/1/2014 demonstrated compliance with the minimum flotation and trim requirements, credit for float scoops to achieve stability in more severe water conditions may be allowed.
However, the effect of scoops on improved sea keeping must be demonstrated during model testing.
(i) Flotation and trim characteristics should be demonstrated to be satisfactory to at least sea state 4 conditions.
(ii) Flotation tests should be investigated at the most critical rotorcraft loading condition.
(iii) Flotation time and trim requirements should be evaluated with a simulated, ruptured deflation of the most critical float compartment. Flotation characteristics should be satisfactory in this degraded mode to at least sea state 2 conditions.
(iv) A sea anchor or similar device should not be used when demonstrating compliance with the flotation and trim requirements but may be used to assist in the deployment of liferafts. If the basic flot ation system has demonstrated compliance with the minimum flotation and trim requirements, credit for a sea anchor or similar device to achieve stability in more severe water conditions (sea state, etc.) may be allowed if the device can be automatically, remotely, or easily deployed by the minimum flightcrew.
(v) Probable rotorcraft door and window open or closed configurations and probable damage to the airframe or hull (i.e., failure of doors, windows, skin, etc.)
should be considered when demonstrating compliance with the flotation and trim requirements.
(4) Float System Reliability. Reliab ility should be considered in the basic design to assure approximately equal inflation of the floats to preclude excessive yaw, roll, or pitch in flight or in the water.
(i) Maintenance procedures should not degrade the flotation system (e.g., introducing contaminants which could affect normal operation, etc.).
(ii) The flotation system design should preclude inadvertent damage due to normal personnel traffic flow and excessive wear and tear. Protection covers should be evaluated for function and reliability.
(iii) Float design should provide a means to minimize the likelihood of damage or tear propagation between compartments. Single compartment float designs should be avoided.
(iv) Where practical, design of the flotation system should consider the likely effects of an uncontrolled water entry and locate system components away from the major effects of structural deformity.
Page D - 94
(v) Visual identification of the helicopter following a ditching (and possible capsize) is made easier by the choice of material for the construction of the floats that has high visual conspicuity properties.
(5) Occupant Egress and Survival. The ability of the occupants to deploy liferafts, egress the rotorcraft, and board the liferafts should be evaluated. For configurations which are considered to have critical occupant egress capabilities due to liferaft locations and ditching emergency exit locations and floats proximity, an actual demonstration of egress may be required. W hen a demonstration is required, it may be conducted on a full-scale rotorcraft actually immersed in a calm body of water or using any other rig or ground test facility shown to be representative. The demonstration should show that floats do not impede a satisfactory evacuation. Service experience has shown that it is possible for occupants to have escaped from the cabin but have not been able to board a liferaft and have had difficulties finding handholds to stay afloat and together. Where practical, handholds or lifelines should be provided. The normal attitude of the rotorcraft and the possibility of a capsize should be considered when locating the handholds or lifelines.
(6) Rotorcraft Flight Manual. The RFM is an important element in the approval cycle of the rotorcraft for ditching. The mate rial related to ditching may be presented in the form of a supplement or a revision to the basic manual. This material should include:
(i) The information pertinent to the limitations applicable to the ditching approval should include the range of sea state conditions that has been demonstrated for water entry and flotation stability. If t he ditching approval is obtained in a segmented fashion (i.e., one applicant performing the aircraft equipment installation and operations portion and another designing and substantiating the liferaft or lifevest and ditching safety equipment installations and deployment facilities), the RFM limitations should state “Not Approved for Ditching” until all segments are completed. The requirements for a complete ditching approval not yet completed should be identified in the “Limitations” section.
(ii) Procedures and limitations for flotation device inflation.
(iii) Recommended rotorcraft water entry attitude, speed, and wave position.
(iv) Procedures for use of emergency ditching equipment.
(v) Ditching egress and raft entry procedures.
(vi) Information stating the flotation system has been certificated for Ditching (as opposed to Emergency Flotation) to facilitate compliance with operational requirements.
Page D - 95
AC 29-2C, Chg 4 5/1/2014
SEA STATE CODE (WORLD METEOROLOGICAL ORGANIZATION) Sea State Significant Wave Height Wind Speed Code Description of Sea Meters Feet Knots 0 Calm (Glassy) 0 0 0-3 1 Calm (Rippled) 0 to 0.1 0 to 1/3 4-6 2 Smooth (Wavelets) 0.1 to 0.5 1/3 to 1 2/3 7-10 3 Slight 0.5 to 1.25 1 2/3 to 4 11-16 4 Moderate 1.25 to 2.5 4 to 8 17-21 5 Rough 2.5 to 4 8 to 13 22-29 6 Very Rough 4 to 6 13 to 20 28-47 7 High 6 to 9 20 to 30 48-55 8 Very High 9 to 14 30 to 45 56-63 9 Phenomenal Over 14 Over 45 64-118 Notes: (1) The Significant Wave Height is defined as the average value of the height (vertical distance between trough and crest) of the largest one-third of the waves present.
(2) Maximum Wave Height is usually taken to be 1.6 x Significant Wave Height; e.g., Significant Wave Height or 6 meters gives Maximum Wave Height of 9.6 meters.
(3) Winds speeds were obtained from Appendix R of the “American Practical Navigator” by Nathaniel Bowditch, LL.D.; Published by the U.S. Naval Oceanographic Office, 1966.
FIGURE AC 29.801-1 Page D - 96
AC 29.803. § 29.803 (Amendment 29-3) EMERGENCY EVACUATION.
a. Explanation. The regulation specifies that “means for rapid evacuation in a crash landing” be provided considering the landing gear extended or retracted, and “considering the possibility of fire.” Any external exits, whether normal entrance doors or service doors, can be considered as emergency exits if the requirements of §§ 29.805 through 29.815 are met. “Limited amphibian rotorcraft” emergency exits are required to be designed for probable maximum local water pressure (or shown to have nonhazardous failure characteristics) and to have a specified number of exits above the water level. Limited amphibian rotorcraft are approved under the provisions of §§ 29.519 and 29.755(b). Sections 29.801 and 29.807(d) refer to similar standards that pertain to “rotorcraft ditching configurations.”
b. Procedures. Exits, arrangement, markings, access, and aisle widths as specified in § 29.805 through 29.815 are to be provided. Recent rotorcraft designs have been approved under the “ditching” standards of § 29.801. Previous “limited amphibian rotorcraft” were designed to the same standards.
AC 29.803A. § 29.803 (Amendment 29-30) EMERGENCY EVACUATION.
a. Explanation.
(1) Amendment 29-30 removed § 29.803(c) which concerned limited amphibians, now obsolete with adoption of § 29.801 ditching standards, and added § 29.803(d) for evacuation criteria of certain rotorcraft designs. Part 29, Appendix D evacuation procedures was adopted concurrently. In addition, newly adopted § 29.803(e) allows use of analysis and tests for compliance with the standard.
(2) This amendment adds explicit demonstration requirements even for certain smaller but “dense” interior arrangements as stated in § 29.803(d)(2).
(3) The 90-second duration for an evacuation demonstration through all exits on one side of the rotorcraft is a primary addition to the standard.
b. Procedures. All of the policy material pertaining to this section remains in effect with the following additions:
(1) For rotorcraft with a seating capacity of more than 44 passengers, conduct an emergency evacuation in accordance with the provisions of Part 29, Appendix D.
(2) For certain smaller rotorcraft with a van or limousine-type “dense” interior as defined in § 29.803(d)(2), conduct an emergency evacuation in accordance with the provisions of Part 29, Appendix D. The rotorcraft should meet all three requirements before a demonstration is specifically required.
Page D - 97
(3) Part 29, Appendix D contains procedures. Safety equipment for alleviating “ground” injuries is contained in paragraph (c) of the Appendix.
(4) A combination of analysis and tests may be used in lieu of test only. A combination of tests and analysis is particularly intended to evaluate emergency evacuations from rotorcraft from 10 to 44 passengers with van or limousine-type interiors. Test other than full -scale evacuation tests may be used in conjunction with analyses to evaluate specific design features such as folding seat backs which affect only one or two passengers. That is, sections of an interior may be used to evaluate a feature and its effects on prompt evacuation of the rotorcraft.
AC 29.805. § 29.805 (Amendment 29-3) FLIGHTCREW EMERGENCY EXITS.
a. Explanation. Flightcrew emergency exits are required when passenger exits are not convenient. The placement of litters, cargo, or bulkheads may prevent passenger exits from being convenient to the flightcrew. Flightcrew exits, if required, are to be of sufficient size and located on both sides of the rotorcraft (or one top hatch) to “allow rapid evacuation of the flightcrew.” A test or tests are required.
b. Procedures. Flightcrew emergency exits, if required, may consist of one overhead hatch or two side exits (one on either side). The size is not explicitly defined except that it be “of sufficient size . . . to allow rapid evacuation of the flightcrew.” The ability for “rapid evacuation” should be demonstrated by test. For side exits located immediately adjacent to the crew seat and exceeding Type IV exits (§ 29.807) in size, the test demonstration can be accomplished by normal use and evaluation of the exits by the FAA/AUTHORITY crew during Type Inspection Authorization (TIA) testing. For any overhead exit or side of fuselage exits not meeting Type IV dimensions, a special demonstration test should be accomplished. This demonstration should show that
2.5 percentile to 97.5 percentile men could egress rapidly through the crew exit(s), i.e., men 5 feet 4 inches to 6 feet 5 inchesto 6 feet in height and up to 225 pounds in weight, based on the Civil Aeromedical Institute’s (CAMI) 1998 Aeromedical Certification Statistical Handbook. If an overhead hatch type exit is utilized, on conventional rotorcraft designs, hazards associated with the proximity of rotor blades should be considered.
AC 29.805A. § 29.805 (Amendment 29-30) FLIGHTCREW EMERGENCY EXITS.
a. Explanation. Amendment 29- 30 adds a new paragraph § 29.805(c) which requires that water or flotation devices not obstruct the flight crew emergency exits after a ditching. Test, demonstration, or analysis is required for substantiation.
b. Procedures.
Page D - 98
(1) The tests, demonstrations, or analysis required by § 29.805(c) for flight crew exits is analogous to those of § 29.807(d)(3) except the crew exit threshold may be slightly below the water line but should not obstruct use of the exit.
(2) Tests in water (tanks or large bodies of water) or demonstrations in the laboratory may be used for compliance if the deflections of flotation devices relative to the exits are accurately or conservatively achieved.
(3) Obstructions should be identified, should be minor, and should not interfere with exit removal or opening, or with crew egress.
AC 29.807. § 29.807 (Amendment 29-12) PASSENGER EMERGENCY EXITS.
a. Explanation. The normal passenger exits (type and number in each side of fuselage) are specified as follows:
(1) For overland operations.
Passenger Emergency exits (rectangular with corner radii of width/3) Seating for each side of the fuselage Capacity Floor level Step-up -29” Max.
Type I Type II Type III Type IV 24” X 48” 20” X 44” 20” X 36” 19” X 26” 1 through 10 11 through 19 20 through 39 40 through 59 1 1 1 or 1 2 1 1 60 through 79 1 1 or 2
(2) For overwater operations (related to ditching an optional standard).
Passenger Emergency exits (rectangular with corner radii of width/3) Seating for each side of the fuselage Capacity Threshold Above Waterline Type III Type IV 20” X 36” 19” X 26” w/step- up - 29” MAX 1 through 9 1 10 through 35 1* Each Additional or Partial Unit of 35 1* *The passenger seat-to-exit ratio may be increased by using larger exits if proven by analyses or tests.
Page D - 99
(3) For crash rollover conditions. Sufficient top, bottom, or ends of fuselage exits are to be provided for evacuation unless the probability of the rotorcraft coming to rest on its side in a crash landing is extremely remote.
(4) Ramp exits to replace Type I or II exits are permitted.
(5) Each emergency exit must be functionally tested.
b. Procedures.
(1) The number and size of overland and overwater operation exits will be as specified. The use of oversize exits is allowed if the threshold is flat and of the specified width.
(2) The top, bottom, or end fuselage exits should be provided unless features of design are provided which prevent the rotorcraft from coming to rest on its side in a crash landing, and unless sufficient fail-safe and fatigue tests and analyses are conducted of the landing gear and support structure to show it is unlikely that the rotorcraft will come to rest on its side as a result of a single structural failure. An analysis is generally necessary to prove compliance with § 29.807(c).
(3) Ramp exits may be used in place of one Type I or one Type II exit if the required Type I or Type II exit is impractical, and if the § 29.813 exit access requirements are met by the ramp exits.
(4) Each emergency exit is to be opened from the inside and the outside as a functional test. Interior panels and seats should be installed for the exit functional tests to check for interferences and other effects. Section 29.813 pertains to access to the exits.
AC 29.807A. § 29.807 (Amendment 29-30) EMERGENCY EXITS.
a. Explanation. Amendment 29- 30 added § 29.807(d)(3) which requires proof that all ditching configuration exits will be free of interference from emergency flotation devices, whether stowed or deployed (inflated). The threshold for each of these “ditching” exits should be above the water line in calm water.
b. Procedures.
(1) Test, demonstration, compliance inspection, or analysis is required to show freedom from interference from stowed and deployed emergency flotation devices. In the event an analysis is insufficient or a given design is questionable, a demonstration may be required. Such a demonstration would consist of an accurate, full -size replica (or true representation) of the rotorcraft and the flotation devices while stowed and after their deployment.
Page D - 100