Interim Recommendation IR19970104

Interim Recommendation issued to: Civil Aviation Safety Authority

Recommendation details
Output No: IR19970104
Date issued: 04 July 1997
Safety action status: Closed

SUBJECT:Emergency Medical Service (EMS) Installations in Australian Registered Aircraft


The helicopter had been dispatched to recover the occupants of an ultralight aircraft who were involved in an accident at Tartrus Station, Qld. The arrival and shutdown of the helicopter were normal. About 10 minutes later, in preparation for the return flight, the pilot returned to the helicopter and opened the valve of the oxygen cylinder fitted inside the cargo compartment. At this time, witnesses heard a loud bang and the pilot was thrown clear of the helicopter. Flames were then seen in the cargo compartment area and the helicopter was subsequently destroyed by fire. The pilot suffered blast damage to his left lung and ear drum, and bruising of his heart and ribs.

The oxygen system fitted to the helicopter was for medical evacuation purposes. It consisted of a size-"D" medical oxygen cylinder located and secured in the top front corner of the cargo compartment. A 1.5m long, 3/8 inch internal diameter, high-pressure flexible hose linked the pressure regulator on the cylinder to a remote pressure gauge in the cabin. The pressure gauge displayed cylinder pressure (up to 19,000 kPa) and the hose was marked "Enzed TP2". A low-pressure oxygen line also ran from the regulator to outlets in the cabin. Renewal of the oxygen supply was effected by replacing the used cylinder with a full cylinder. This operation had been carried out by the pilot prior to the last flight.

Examination of the recovered aircraft components by the Aeronautical and Marine Research Laboratory (AMRL) indicates that the polyester lined flexible hose assembly and its associated fittings were inappropriate for the application.

The investigation has revealed that when the pilot opened the valve the oxygen system high-pressure flexible hose failed at approximately the mid-point. The failure was most likely initiated by a foreign particle impacting the internal polyester lining of the hose and initiating combustion. The hose had been fitted to the helicopter approximately 5 weeks before the accident (see appendix 1, figures 1 and 2).


As a result of this occurrence, the following safety deficiencies were identified:

(i) Oxygen installations may be in operation in emergency medical service equipped aircraft with the potential for a similar occurrence.

(ii) Civil Aviation Safety Authority (CASA) staff indicate that, in Australian registered aircraft, emergency medical service equipment installations are not subject to any specific CASA requirements in regard to their design, installation and maintenance.

(iii) Although external role equipment is specified in the Aviation Safety Surveillance Program (ASSP) aircraft survey checklists, emergency medical service installations are not subject to regular, continuing airworthiness surveillance.

(iv) The investigation revealed that there were no emergency medical service operating procedures available to the flight crew in the aircraft flight manual or the company operations manual.

(v) There is a general lack of awareness within the aviation industry with regard to the installation and maintenance requirements of emergency medical service oxygen equipment.


Civil Aviation Order 108.26 specifies requirements for oxygen systems fitted to aircraft. Discussions with Civil Aviation Safety Authority staff indicate these requirements are intended for aircraft crew and passenger requirements and are not intended for emergency medical service installations.

The investigation examined a number of aspects relevant to this accident and other similar operations. These include:

(i) oxygen system design;

(ii) standards and certification of medical oxygen systems in aircraft;

(iii) the types of cylinders used in medical oxygen systems;

(iv) flight crew training in the handling of medical oxygen systems fitted to aircraft; and

(v) maintenance requirements for these systems.

In 1988, The United States National Transportation Safety Board (NTSB) conducted a safety study into "commercial emergency medical service helicopter operations" (report number NTSB/SS-88/01). The report specifically mentioned an oxygen systems installation to a Bell 206-L1 helicopter and detailed deficiencies in the installation. The installation to the Bell 206-L1 was similar to that fitted to VH-CKP. The report made several recommendations, of which two (A-88-6 and A-88-7) are relevant.

The Federal Aviation Administration (FAA) response to the safety recommendations was to issue Advisory Circulars (AC) 135-14A, "Emergency Medical Services/Helicopter (EMS/H)" and 135-15, "Emergency Medical Services/Airplane (EMS/A)". They also revised Advisory Circular (AC) 27-1, "Certification of Transport Category Rotorcraft", to include paragraph 786, "Emergency Medical Service Installation, Interior Arrangements, and Equipment" (see appendixes 2 and 3).

In addition, the FAA requires additional operating and inspection requirements for air ambulance operators, above that normally imposed upon commercial operators.

Output text

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority:

(i) conduct an audit of all emergency medical service oxygen-equipped aircraft to determine the equipment standards in Australian registered aircraft;

(ii) issue design standards for emergency medical service oxygen equipment installations;

(iii) issue maintenance requirements for emergency medical service oxygen equipment;

(iv) provide surveillance requirements for emergency medical service oxygen equipment in the Aviation Safety Surveillance Program;

(v) ensure flight crew are provided with appropriate instuctions in the use of emergency medical service oxygen equipment in aircraft flight manuals or company operations manuals; and

(vi) provide educational material to the aviation industry on the installation, operation and maintenance requirements of emergency medical service oxygen systems.

Initial response
Date issued: 06 August 1998
Response from: Civil Aviation Safety Authority
Action status: Closed - Accepted
Response text:

I refer to BASI Interim Recommendation, IR970104, in relation to the Bell Helicopter accident at Tartrus Station, Queensland on 2 May 1997. This incident has clearly revealed some deficiencies in current CASA procedures regarding medical oxygen systems used in aircraft. These deficiencies require correction.

Issue design and maintenance standards for EMS 02 equipment installations (Recommendations ii and iii)

Role equipment such as that installed in EMS aircraft is installed on the basis of "No Hazard, No Interference." There are at present two Australian standards which relate to aircraft oxygen systems:

CAO 20.4, Provision and Use of Oxygen and Protective Breathing Equipment,

CAO 108.26, Systems Specifications - Oxygen Systems

Neither of these standards are directly applicable to EMS 02 systems, addressing instead supplemental oxygen for high altitude flight. However, Federal Aviation Administration AC 27-1, Certification of Normal Category Rotorcraft contains a section on EMS 02 systems. Unfortunately, this US AC has no legal standing under Australian law.

Thus, while much information is available, it is not clearly presented, is fragmented, and in some cases is out of date. I therefore intend to expedite the issue of a CAAP providing integrated design guidelines for this type of installation. This CAAP, expected to be issued by September 1998, will cover the design, installation and maintenance of Emergency Medical Services Oxygen Systems.

Provide surveillance requirements for EMS 02 equipment in ASSP. (Recommendation iv)

The ASSP program does not at present specifically address surveillance of aircraft internal role equipment, such as medical oxygen systems. This deficiency will be addressed, and the ASSP amended as necessary to include this type of equipment.

Conduct an audit of all emergency medical service 02 equipped aircraft to determine the equipment standards in Australian registered aircraft. (Recommendation i)

Because there is at present no readily available standard against which to audit existing EMS 02 installations, and because very few CASA (or industry) people have the knowledge or experience of oxygen systems necessary to conduct such an audit, I do not believe that an audit is appropriate at this stage.

Issue of the CAAP and clarification of ASSP requirements are expected to have a beneficial effect, resulting in improvements and upgrading of existing systems. However, should routine surveillance reveal widespread problems or raise further concerns, additional action will be taken to overcome the problems.

Provide educational material to the aviation industry on the installation, operation and maintenance of EMS 02 systems. (Recommendation vi)

CASA is planning to conduct an educational seminar in the latter part of this year involving CASA staff and industry personal, including designers, operators and other interested parties. Your assistance in conducting this seminar would be much appreciated, including a presentation on this incident and the BASI finding. The CAAP will also assist in this regard.

Ensure that flight crew are provided with appropriate instructions in the use of EMS 02 equipment in Aircraft Flight Manuals or Company Operations Manuals. (Recommendation v)

EMS systems are normally installed in aircraft as modifications, under the auspices of CAR 35. An important part of any such modification is the provision of the necessary amendments or supplement to the aircraft flight manual. The CAR 35 authorised person who approves the modification should be ensure that such data are available and included in the modification package. This requirement will be reinforced in the CAAP.

Last update 01 April 2011