Fixed-Wing Air Ambulance Conversions

Proposed Solution:

The PAL Aerospace engineers proposed applying for an exemption to the applicable regulation. The suggested new design would use the original baggage area for medical equipment and consumables, using a 9G cargo net that the medical team could open and refasten behind them. Net mesh sizing would restrain the size of the articles stowed and allow trained crew members to monitor for smoke in case of a fire.

Airworthiness Liaison:

Airworthiness authorities worldwide are understandably concerned about issuing exemptions to safety regulations. In this case, Transport Canada needed assurance that there was a legitimate need, that it was in the public interest, and that the proposed modification would maintain aviation safety. Months of comprehensive negotiation, documentation, and liaison followed between PAL Aerospace engineers and Transport Canada, with the final agreed mitigating factors in support of an exemption including:

• Design of a custom 9G stowage net meeting FAR25 flammability requirements
• Calculate stowage net mesh size to effectively restrain all stowed supplies
• Changes to the cargo loading manual, flight manual supplements, and supplemental cabin loading documentation
• Implement primary and secondary fire detection methods for the stowage area and show firefighting efficacy from outside the net
• Devise training for flight attendants and medical personnel for opening and closing the cargo net, smoke detection, and firefighting
• A system of ensuring the overhead lockers are used for stowing small or slender items that would pass through the cargo net mesh
• Development of an STC Maintenance manual supplement
• Restriction of the aircraft to fixed-wing air ambulance MEDEVAC operations only

Transport Canada issued the exemption to FAR25.787 18 months later, just before the fixed-wing medical transport modification STC approval.

Points to Note:

• Modifications conflicting with safety legislation will require comprehensive analysis and study to prepare a justification for the issue of an exemption by the airworthiness authority. Anticipate expending considerable resources and time, and consider if an alternate means of operation might obviate the need for an exemption application.

• If the modification is unavoidable, work with your engineering contractor and airworthiness authority to understand the cost and expected duration of the exemption process. What are the chances of the exemption not being issued, and what is your alternate solution?

• As shown in the case study above, the mitigation of the safety concerns involved maintenance, operations, the medical team, and engineering while imposing operational restrictions on aircraft use. It required a close and respectful partnership between the client team, engineering contractor, and airworthiness authority, with good and frequent communication so all parties understand the implications of the proposed modifications.

• Finally, choose an engineering contractor with the in-house expertise to manage the complexity of such a modification for a fixed-wing aircraft. Stitching together multiple organizations is possible, but it makes project management more difficult, increases cost, and can introduce interface risks, reducing the accountability and responsiveness of each entity.
  

  ---

Engineered Solution:

The client proposed a multirole self-contained intensive care unit (ICU) manufactured by Aerolite to optimize patient care. The unit is mounted close to the fuselage wall but allows lateral deployment to support simultaneous medical intervention from both sides of the patient. However, the ICU’s footprint geometry was incompatible with the host aircraft’s underfloor structure. To use this product, PAL Aerospace engineers needed to design, substantiate, and install a system of underfloor bridges and an auxiliary framework suitable for reacting forces back to the existing structure. The engineering team reviewed the OEM’s test plans and reports for the ICU module before submitting the modification for airworthiness approval and effecting the fixed-wing medical transport’s structural modifications.

Key Observations:

• Before choosing your modification contractor, quiz them on past modifications where they resolved key ergonomic issues for their client. An experienced team will have encountered and solved many client operational concerns while understanding leading medical equipment and suitable medevac aircraft.

• Challenge a multi-disciplinary client and engineering team to identify sub-optimal layouts and designs early in the planning stage to prevent costly rework or the acceptance of inferior solutions on operating aircraft.

• Carry out a formal commissioning process with a medical team enacting several medical scenarios, including loading, flight, and unloading, to ensure the design and placement of equipment work as expected

Engineering Solutions:

The Epishuttle is designed and tested as a road ambulance transport device. To achieve STC approval for the diverse aircraft types, PAL Aerospace was required to substantiate compliance with aviation requirements.

Much of the required substantiation revolved around the Epishuttle’s design and construction. While the product had undergone testing in an accredited laboratory, this was focused on road ambulance transport, requiring a gap analysis to highlight areas needing additional testing for aeronautical use.

The analysis by PAL Aerospace confirmed the system met patient retention requirements under crash loads, had been evaluated for structural integrity under decompression and emergency landings, and met vibration requirement tests. However, further testing of Epishuttle’s flammability compliance and electromagnetic interference (EMI) was needed. EMI testing ensures a system can operate properly without interfering with other aircraft systems.

Additionally, an important issue arose regarding the Epishuttle’s design. Once a patient is inside the pod, they cannot exit unaided. Yet aviation regulations stipulate that all passengers and crew members must be able to evacuate the aircraft within 90 seconds using half of the available emergency exits. This test demands that evacuation procedures are efficient and that aircraft designs facilitate quick and safe egress in emergencies.

To demonstrate compliance with evacuation regulations, PAL Aerospace developed a flight manual supplement that designated one medical attendant as essential crew when traveling with a patient. That attendant could remove the Epishuttle’s protective hardcover if an emergency evacuation is required. In a worst-case scenario, the attendant would also evacuate the patient. Regulatory compliance was demonstrated by carrying out a full-scale emergency evacuation demonstration.

Finally, the safe installation of the Epishuttle into each aircraft was demonstrated by finite element analysis and test.

Important Considerations:

• Compliance substantiation of a medevac conversion is not limited to aircraft installation and cabin safety but covers individual product design and construction.

• Despite medical equipment being designed and tested to stringent standards, airworthiness regulations demand comprehensive compliance substantiation. These may include retesting or additional compliance demonstrations, as shown by the emergency evacuation requirement for the Epishuttle.

• Early client liaison with their chosen engineering contractor over desired medical installations will quickly identify regulatory testing and substantiation pathways and assist device selection decisions.