Military Evacuation Aircraft

In this step you will learn about the ability to transport sick or wounded personnel by land, air or sea by armed forces worldwide explained by German Airforce Hauptmann Stefan Hautz, Zentrum fuer Luft und Raumfahrtmedizin der Luftwaffe, Bundeswehr and Oliver Thomaschewski, Director A/C components – OEM & Customized Solutions, Lufthansa Technik. Both are highly acknowledged experts and will be able to give you unique insights into the world of military transfer solutions. Such transfer capability is clearly necessary in case of armed conflicts, but also when troops are deployed abroad for missions or training. Moreover, disaster relief and accidents are also typical scenarios involving the transfer of civilians on armed forces aircraft.

The NATO Standard For Aeromedical Evacuation

• NATO members agreed on standards; the so called STANAG (Standardization Agreement).
• STANAG 3204 also provides guideline criteria for clinical selection. The patient criticality is defined in three stages: priority, urgent and routine. Another criterion is the level of dependency, in four stages between intensive care and assistance for walking patients.

The aeromedical standard also lays out types of transfer:

1. Forward Aeromedical Evacuation (FwdAE) are transfers from point of injury to first medical facility as quickly as possible; a typical mission for light utility helicopter.
2. Tactical (intra-theatre) Aeromedical Evacuation (TacAE), are transfers of short or medium distance from medical facility to another within the operation zone; a typical mission for medium or heavy utility helicopter or short take-off and landing (STOL) aircraft. The ability to land on unpaved runways can be important.
3. Strategic (inter-theatre) Aeromedical Evacuation (StratAE), are transfers of a long distance between operation zone and domestic base; a typical mission for military versions of large aeroplanes.

How to perform forward, tactical and strategic aeromedical evacuation can differ greatly and depends highly on the situation, with versatile factors such as patient condition, number of patients, medical units, available air transport vehicles, capacity and equipment, risk of the mission, and so on. It could be anything from a stretcher with an equipment bridge strapped on the floor for life support measures to a patient transport unit (PTU) for intensive care treatment.

Therefore, armed forces in NATO need suitable aircraft with different readiness levels respectively – i.e. notice to move (NTM) times.

Military Evacuation Considerations

• Why is the number of patients in an evacuation aircraft limited? The answer is a compromise of technical and operational considerations, which we’ll look at below.
• Interoperability is also a precondition for allied forces, especially when there are mass casualties, and standardised interfaces are needed for equipment.

Oxygen

This is needed at every patient position. The total amount of oxygen within the cabin is very high. Unfortunately oxygen stowage carries a risk, as the failure of an oxygen cylinder might cause complications up to the total loss of the aircraft.

Within a patient transport unit (PTU), certain safety features are necessary to reduce the risk of oxygen within the unit to an acceptable level. Some areas within the fuselage are riskier than others; for example, there are zones where blast fragments might penetrate the fuselage. The aircraft is designed to withstand such a scenario, but in case of a oxygen cylinder hit, this might result in a complete loss.

Thus the full length of the aircraft cannot be used for oxygen stowage. Since the length of low pressure oxygen lines is limited, a central oxygen supply system is also not a simple solution.

Electrical Power

A further limiting factor is the electrical power provided by the aircraft. An intensive care patient on a PTU requires at least 500W. The total power available for the cabin is relative low and would not allow much more consumption. The conversion of the aircraft power to typical supply voltages of the medical equipment, as well as the electric safety, is managed by the PTU converter.

There are also requirements for lighting, alarm indications, treatment sizes, crash and vibration levels.

Patient Onboarding

A more operational consideration is the patient loading and unloading process. Due to the limited number of doors and space available, the loading and unloading process can take some time.

The number of patients that might be accepted by a receiving hospital at the destination can also be a limiting factor.

Not all doors of the aircraft can be reached easily by a high loader (trucks similar to catering trucks) or directly by a rear cargo ramp door. Doors positioned directly behind the wings, for example, have a high risk of damage if a high loader is manoeuvred to this position.

Loading via stairs is not preferred due to the weight and incline. Inside the aircraft it must be possible to turn 90° from the door areas into the aisle.

A schematic layout of a German military aeromedical evacuation aircraft

Looking at the layout above, you may notice that patient positions are available on both sides. This is not only for symmetry but also critical from a medical perspective, with patient bed arranged according to pattern of injury.

Disinfection

• A further important topic is decontamination. Routine as well as authority-ordered disinfections may be necessary for infective transfers.
• As many agents are very aggressive and corrosive, disinfection is a critical procedure within an aircraft and the agents have to be approved for use in the aeromedical evacuation aircraft type.