Advisory Circular (AC) No. 500-013 Issue 1

The purpose of this Advisory Circular (AC) is to summarize criteria for the certification of design and installation of systems for the carriage of bulk liquids in aircraft, including liquids classified as dangerous goods. Although mandatory terms such as "must" and "shall" are used in this AC, because the AC method of compliance is not in itself mandatory, these terms apply only to applicants who seek to demonstrate compliance by using the specific methods described in this AC.

1.2 Guidance Applicability

This document is applicable to all Transport Canada personnel, delegates and industry.

1.3 Description of Changes

This document, formerly AMA No. 500/12, is reissued as an AC. The reference documents and the content have been reviewed and updated.

1.4 Termination

This document does not have a terminating action. It will however, be reviewed periodically for suitability of content.

2.0 References

2.1 Reference Documents

It is intended that the following reference materials be used in conjunction with this document:

(a) Transportation of Dangerous Goods Act, 1992;

(b) Transportation of Dangerous Goods Regulations;

(d) Chapter 525 of the AWM - Transport Category Aeroplanes;

(e) Chapter 527 of the AWM - Normal Category Rotorcraft;

(f) Chapter 529 of the AWM - Transport Category Rotorcraft;

(g) Advisory Circular (AC) 500-005 - Fire Protection -Ignition Sources;

(h) AC 500-007 - Lightning Protection of Aeroplane Fuel Systems;

(i) AC 500-009 - Composite Aircraft Structure;

(j) AC 525-012 - Certification of Large Aeroplanes in the Restricted Category, Used for Special Purpose Operations;

(k) Federal Aviation Administration Advisory Circulars (FAA AC) 23-10 - Auxiliary Fuel Systems for Reciprocating and Turbine Powered Part 23 Airplanes;

(l) FAA AC 25-8 - Auxiliary Fuel Systems Installations;

(m) FAA AC 20-128A - Design Considerations for Minimizing Hazards Caused by Uncontained Turbine Engine and Auxiliary Power Unit Rotor Failure;

(n) International Civil Aviation Organization (ICAO) Annex 18 (Doc 9284) - Technical Instructions for the Safe Transport of Dangerous Goods by Air;

(o) U.S. Military Handbook (MIL-HDBK)-5J - Metallic Materials and Elements for Aerospace Vehicle Structures Handbook;

(p) U.S. MIL-HDBK-5087 - Bonding, Electrical, and Lightning Protection for Aerospace Systems;

(q) International Maritime Dangerous Goods Code (IMDG Code), published by the International Maritime Organization;

(r) Society of Automotive Engineers (SAE), Aerospace Recommended Practice (ARP) 1870 - Aerospace Systems Electrical Bonding and Grounding for Electromagnetic Compatibility and Safety; and

(s) SAE Aerospace Information Report (AIR) 5128 - Electrical Bonding of Aircraft Fuel System Plumbing Systems.

2.2 Cancelled Document

As of the effective date of this document, AMA No. 500/12 dated 7 April 2000 is cancelled.

3.0 Background

In the past, the design and installation of bulk liquids carriage systems were primarily approved as major modifications or through the supplemental type certificate process, using standards referenced in the basis of certification of the aircraft. In one specific case, for the modification of large aeroplanes for the fire-fighting role, AC 525-012 - Certification of Large Aeroplanes in the Restricted Category, Used for Special Purpose Operations provides guidelines for such approval. However, some bulk liquids carriage system designs and installations have generated confusion due to the lack of uniform standards. In addition, it was also unclear as to when the liquid container is to be classified as cargo or bulk liquid container. This AC summarises criteria to be used for the certification of design and installation of bulk liquids carriage systems. Guidance on the installation of auxiliary fuel systems can be found in FAA AC 23-10 and 25-8.

4.0 Definitions

The following definitions are applicable to this AC:

(a) Bulk Liquids - means a liquid is considered to be transported in bulk if it is loaded by filling a previously installed container, the design and installation of which has been shown to comply with applicable airworthiness standards.

(b) Dangerous Goods - means a product, substance or organism included by its nature or by the regulations in any of the classes listed in the Schedule to the Transportation of Dangerous Goods Act.

(c) Extreme Environment - means those conditions that are not encountered during the routine operating life of the materials used in bulk liquids carriage systems. Examples are conditions that may be imposed by component failure or crash environments.

5.0 Carriage of Dangerous Goods

In addition to the criteria set out in this AC, bulk liquids carriage systems designed for the transportation of liquids classified as dangerous goods must comply with the requirements of the Transportation of Dangerous Goods Regulations.

Note:

The Transportation of Dangerous Goods Regulations requires that dangerous goods be transported in accordance with the International Civil Aviation Organization (ICAO) Technical Instructions for the Safe Transport of Dangerous Goods by Air except for certain situations. The ICAO Technical Instructions specify packaging requirements for individual dangerous goods with quantity limits when these dangerous goods are transported as packaged cargo. Application for a Permit for Equivalent Level of Safety to the Transport Dangerous Goods Directorate is required for the transportation of dangerous goods when these packaging instructions are not followed or the quantity limits are exceeded. Other issues dealing with dangerous goods should also be referred to the Transport Dangerous Goods Directorate.

6.0 Component Material

6.1 Material Properties

Materials used in the bulk liquids carriage system must have the following properties:

(a) Properties Under Normal Environment

(i) Materials used in the bulk liquids carriage system must be compatible with the bulk liquid and its vapour; i.e. they must not react with, deteriorate, harden, soften, shrink, expand, dissolve, etc. under short term or prolonged exposure to the bulk liquid and its vapour.

(ii) Materials used must be ozone resistant since high concentrations of ozone may be encountered by aircraft at cruise altitudes.

(iii) Materials used must be corrosion resistant or suitably protected from corrosion.

(iv)Materials and components used must perform their intended function throughout the approved aircraft operating envelope.

(b) Properties Under Extreme Environment

The high temperature strength and fire resistance properties of materials used in the bulk liquids carriage system must be considered for those components that may be subjected to sources of heat or fire due to crash conditions or the failure of some other components nearby. Materials used must be self-extinguishing and must not release toxic gas under fire conditions.

6.2 Material Allowables

Material allowables used in the design of bulk liquids carriage system must meet the following:

(a) For metallic structures, the design allowables contained in MIL-HDBK-5J, Metallic Materials and Elements for Aerospace Vehicle Structures Handbook, are acceptable.

(b) Applicants who wish to submit compliance documentation for structures made from composite materials should refer to AC 500-009 Composite Aircraft Structure for guidance.

7.0 Container Design

7.1 Containers for Dangerous Goods

Bulk liquids containers to be used for the transportation of Dangerous Goods must meet the portable tank requirements of section 12.2 to 12.4 inclusively, of the Supplement to the ICAO, Annex 18 except as follows:

The ICAO Technical Instructions refer to section 13.1.4.1 of the International Maritime Dangerous Goods Code (IMDG Code) for strength requirement of the container and their fastenings. In addition to the IMDG Code strength requirements, bulk liquids containers must be designed to withstand all ground and flight design loads, including emergency landing loads and cabin pressurisation.

7.2 Other Containers

Other bulk liquids container designs must take into consideration the following:

(a) Structural Considerations

(i) Containers must be designed to withstand pressure load due to liquid head, vapour pressure and partial pressure of air and other gases in the tank above the liquid space in conjunction with all ground and flight design loads, including emergency landing loads, cabin pressurization and dynamic loads due to liquid sloshing.

(ii) When considering liquid pressure or inertia loads due to liquid in the container, the most critical liquid density must be used.

(iii) Container internal pressure developed during malfunction of the pressure filling system, if applicable, must be considered in the evaluation of the container and its support structures.

(iv) Container design should isolate the container from airframe induced structural loads and deformations.

(v) Impact damage scenarios not considered as extremely improbable must be considered in establishing the adequacy of the design.

(b) Vibration

(i) unstiffened wetted surfaces supporting liquid pressure loads must be designed to account for the effect of excitation of these wetted surfaces by either avoiding resonance or by isolation of the container from the source of vibration.

(ii) Containers must be vibration tested according to AWM 523.965(b), 525.965(b), 527.965(d), 529.965(d) or equivalent.

Each container must have an expansion space to allow for thermal expansion of the liquid being carried. It must be impossible to fill the expansion space with the aircraft in normal ground attitude.

(d) Venting

Provision must be made to vent liquid container overboard in case of over pressure. The vent must be located in the expansion space of the container and the overboard exit must be designed and located to prevent fluid from re-entering the airframe, engine intake or the aircraft heating and ventilation system.

The vent system must be designed to:

(i) Allow rapid relief of excessive differences in pressure between the interior and exterior of the container;

(ii) preclude a negative pressure which would drain liquid overboard in flight; and

(iii) avoid being blocked by frozen condensation.

8.0 System Installation

8.1 Structural Considerations

Installation of bulk liquids carriage system must not compromise the structural integrity of the aircraft. The installation must meet the requirements of the basis of certification of the particular aircraft.

(a) Bulk liquids container restraint system (attachment hardware and support structure) must be designed to withstand all ground and flight design loads, including emergency landing loads.

(b) The allowable floor, bulkhead and local shell limit loads must not be exceeded as a result of system installation and use.

(c) Since hard attachment points restrict relative motion and result in high concentrated loads on the container and airframe, attachment point loads must be evenly distributed and crash load failure points between the container and the airframe must be provided to minimize the potential of container rupture in the event of accidental overload.

(d) A fitting factor of at least 1.15 must be applied to container support fittings and attachments.

(e) All probable combinations of liquid distribution including liquid migration due to container not filled to full capacity or liquid in multiple containers, must be accounted for when:

(i) Defining container structural loads.

(ii) Considering aircraft weight and balance and center of gravity limits.

8.2 Design and Location

The design and location of bulk liquids carriage systems require special consideration:

(a) Bulk liquids carriage systems must be designed so that filling and emptying of the container can be done without spillage of liquid or release of fumes within the aircraft.

(b) Container location must be evaluated from the standpoint of protection provided against uncontained engine and auxiliary power unit rotor or rotor blade failures to ensure that the aircraft safety level has not been degraded by the installation of the bulk liquids carriage system. FAA AC 20-128A Design Considerations for Minimizing Hazards Caused by Uncontained Turbine Engine and Auxiliary Power Unit Rotor Failure could be used as guidance material.

(c) Bulk liquids carriage systems designed for the transportation of flammable or dangerous goods must be isolated from personnel compartments by a fume proof enclosure that is resistant to the liquid being carried and its vapour.

(d) When bulk liquids carriage systems are installed in cargo or baggage compartments, all materials used must meet the flammability requirements of cargo and baggage compartment liners.

8.3 Venting and Drainage for Spaces Adjacent to Container Surfaces

Ventilation and drainage must be provided for spaces between the bulk liquids container and the fume proof enclosure specified in section 8.2(c) above to avoid fume accumulation due to minor leakage. The vent system must be designed to account for pressure changes due to altitude change including emergency descent.

8.4 Ignition Prevention

When designed for the transportation of flammable liquids, the following must be considered to minimize hazards due to ignition of the liquids or their fumes:

(a) Electrical Bonding and Grounding

To dissipate the accumulated static electric charges due to sloshing and liquid flow during filling of the container and to prevent arcing between components due to lightning currents, all conductive components of the bulk liquids carriage system must be electrically bonded and grounded to the aircraft structures.

Bonding jumpers must be installed so that the resistance of each connection does not exceed 0.003 ohms. The current carrying capacity, impedance and inductance of the bonding jumper is of particular concern when lightning strike is considered, owing to the high current, rapid current rise time and potential high frequencies involved. If two or more components are grounded to the aircraft structure in series, both ends of the ground circuit must be grounded to ensure that loss of an intermediate ground connection will not leave any component isolated from the ground. Refer to MIL-B-5087, SAE ARP 1870 and SAE AIR 5128 for additional bonding guidelines and installation methods.

Means must be provided to dissipate accumulated electric charges and to divert electrical current from composite or non-metallic components to minimize the hazards resulting from static electricity or lightning.

Where the transfer of flammable liquids between the bulk liquids carriage system and ground equipment is intended, procedures for grounding and bonding of the system to ground equipment must be provided and detailed in the "Operating Manual".

(b) Lightning Vulnerability

Bulk liquids carriage system installations must take into consideration the direct strike and indirect effects of lightning. Refer to AC 500-007 Lightning Protection of Aeroplane Fuel Systems for guidance.

Surfaces, which may become hot during normal operation or failure condition, must be suitably protected if flammable liquids or their vapours may come into contact with these surfaces. Refer to AC 500-005 Fire Protection - Ignition Sources for guidance.

8.5 Emergency Exit Access

Installation of the bulk liquids carriage system must not affect access of emergency exits.

8.6 Dynamic Stability

Any short period oscillation of the aircraft with the bulk liquids carriage system installed must be heavily damped. Compliance with the requirements of AWM 523.181(a), 525.181(a) or 529.181 as appropriate to the aircraft category must be shown with the liquid container filled to the most adverse condition.

9.0 Other Requirements

9.1 Limitations

(a) Weight and Loading Limitations

The maximum allowable amount of liquid that can be carried in each container must be specified. Loading limitations may be required to maintain weight/c.g. within limits.

(b) Operating Limitations

The manoeuvreing limitations must be specified.

Cargo and floor loading restrictions may be required as a result of the bulk liquids carriage system installation.

9.2 Filling and Emptying Procedure

Filling and emptying procedures must be developed and included in the operating instructions. The procedures should include all safety requirements to minimize the possibility of spills and hazards associated with ignition of flammable liquids and their vapours, if applicable.

9.3 Aircraft Flight Manual

Each operating limitation resulting from the installation of bulk liquids carriage system on an aircraft and any additional information necessary for safe operation must be developed and included in a Flight Manual Supplement.

For the carriage of liquids classified as dangerous goods, the Flight Manual Supplement must restrict the operation of the aircraft to essential crew only with no passenger permitted.

For the carriage of flammable liquids, the Flight Manual Supplement must prohibit smoking on board the aircraft.

9.4 Placards

(a) Placards located in the cargo compartment, on the aircraft exterior or adjacent to the bulk liquids carriage installation may be required to inform or caution the ground crew of certain aspects of the installation. Information may include:

(i) Cargo compartment loading restrictions or limits; and

(ii) identification of drain access doors, masts, etc.

(b) A placard with a minimum of the following information must be attached to the bulk liquids carriage container:

(i) Manufacturer and date of manufacture;

(ii) original hydrostatic test date;

(iii) test pressure;

(iv) date and test pressure of most recent periodic test; and

(v) the types of liquid the container is designed to carry.

(c) For the carriage of dangerous goods, safety marks as required by the Transportation of Dangerous Goods Regulations must be displayed on the container.

9.5 Inspection Provisions

Adequate means must be provided to allow close examination of the bulk liquids carriage system when required.

9.6 Instructions for Continuing Airworthiness

Instructions for Continued Airworthiness must be developed for the aircraft with the bulk liquids carriage system installed.

10.0 Headquarters contact

For more information please contact:

Policy Standards Coordinator (AARDH/P)
Phone: (613) 990-3923
Facsimile: (613) 996-9178
E-mail: AARDH-P@tc.gc.ca

Original signed by Maher Khouzam

Maher Khouzam
Chief, Regulatory Standards
Aircraft Certification Branch

Language selection

WxT Language switcher