Evaluation of the offset static rope evacuation procedure: insights from a safe job analysis

The time from an incident to the start of pre-hospital care is considered an influential factor determining patient outcome [1‐4], particularly for severely injured or ill patients [1, 5‐7]. Human External Cargo (HEC) operations is a small part of the Norwegian Helicopter Emergency Medical Services (HEMS) mission profile, but patients which need an extraction with HEC often either have no other alternatives or more time-consuming methods are utilized, e.g. ground based rescues. With reference to this, Norwegian HEMS is focusing on the development of new rescue operation techniques so that, in some situations, patient treatment can be started earlier than is currently the case.

As of today, Norwegian HEMS only use static rope evacuation. In a static rope rescue operation, the HEMS technical crew member (HCM) acts as the rescuer and is transported, underslung, to the accident site by a fixed rope. The length of the rope used differs between 10 and 60 m and depends on the actual situation (terrain) [1, 8]. During the static rope rescue operation, the pilot cannot see what is underneath the helicopter and is assisted in this phase by the emergency physician, who verbally communicates vertical and horizontal guidance. The HCM communicates with the other crew members by both a wireless intercom and standardized hand signals. After the HCM gains ground contact, he or she can disconnect from the static rope. The helicopter then leaves the scene with the static rope underneath it and normally hovers not far from and in sight of the scene of the accident [7, 8]. The helicopter returns to the scene following communication with the HCM after necessary patient treatment and preparations have been carried out. When the helicopter arrives, the HCM reconnects himself and the patient to the static rope, so that both can be evacuated, underslung, to the rig site before further patient treatment can be provided. The patient is then taken to the hospital by either helicopter or ambulance. An additional safety measure, which has shown its safety relevance for static rope missions in complex terrain, is the so-called double attachment procedure [8]. This method ensures that the HCM and patient are attached to a safety barrier at all times of the operation due to a high risk severity on site.

By focusing on improvements, the Norwegian service has identified situations in which the helicopter crew is unable to establish contact with the patient through traditional HEC methods, either hoist- or static rope rescue operations. In most cases, the helicopter lands at the scene of the accident, but, in situations where the helicopter cannot land close to the scene due to either forest- or mountainous terrain, a HEC method can be used. In some circumstances, however, it is not possible to achieve contact with the patient, even with the use of either a hoist or static rope. This is in situations where the helicopter cannot be positioned vertical above the accident site due to the terrain, e.g. a vertical or overhanging mountain wall (Fig. 1). These missions are rare, approximately 1–2 missions annually according to the Norwegian Alpine Rescue Groups (September 2023). As of today, there isn`t a national system for registering these missions. Even though the patient numbers are low, the potential health benefit for these patients could be substantial. It is with reference to this that a so-called offset technique has been developed, where the helicopter is out of plumb from the scene but where one can still make contact with the scene of the accident by using an offset throw line.

There are some other existing methods to gain access to the patient in these circumstances, including HEC operations with the use of a telescopic pole, “super longline” by the rescue helicopter service or “very long line” evacuations with static rope, where the longest reported rope length has been 1000 m in Romsdalen, Norway (July 2019). One possible advantage of using very long-line evacuations is the reduction of downwash from the rotor on the accident site. This could avoid air-filling of a parachute if the patient is still attached to it. Our study focuses on the offset technique, as it is a low-cost method which is realistic to implement in the current Norwegian system. Offset technique is considered as an additional rescue method to existing procedures, e.g. rescue procedures conducted by the rescue helicopter service.

A Safe Job Analysis, often referred to as an SJA, is a simple, qualitative risk analysis methodology used to identify hazards associated with a task to be performed [9, 10]. The method can be used on a wide range of work tasks. In this study, conducted during the last week of May 2021, the people who performed the tasks were included in the analysis [9]. The implementation of the analysis was led by a risk analyst. After completion of the tasks the participants were debriefed using a semi-structured interview focusing on the risk driving momentums. The interview was recorded and analysed.

The SJA was carried out by dividing the work assignments that was executed into tasks and sub-tasks. Hazards and conditions that could lead to dangerous situations were identified for each task/sub-task (Table 1).

Our study focuses on analysing the offset static rope evacuation procedure. A technical rescue procedure has been developed to describe how a rescue operation using the offset technique should be carried out. The procedure is an adjusted variant of a similar technique used by rescue personnel in Yosemite National Park, USA [11]. Prior to the procedure, an internal company risk analysis was carried out and quality assured by the company’s Safety Action Group. We identified a need for a more systematic risk analysis of the offset rescue technique, bringing in more experience from crew members, in order to obtain better insight into the potential hazards of using the offset rescue technique. The output from the analysis is further used to evaluate the existing procedure for the offset technique, to see the extent to which different identified hazards are eliminated or considered, in the way the procedure is described.

In missions requiring the offset technique, the HCM can establish a connection to the patient by using an offset throw line. One part of the offset throw line is connected to the HCM’s harness, while the other part is thrown by the HCM and caught either by personnel at the accident site or in cooperation with volunteer rescue climbers. The offset throw line is equipped with a weak link, as shown in Fig. 2. The weak link is essentially a link designed to ensure that an emergency release breaking point is included in the chain. The weak link is attached to the HCM`s harness and breaks at a load of 70 kg in case of an unintentional entanglement of the throw line [12].

With the help of the offset throw line, the climber can, in coordination with the helicopter’s descent, drag the HCM to the accident site; see Fig. 3.

The HCM can also gain access to the accident scene without a climber. In such situations, the offset throw line will be thrown to the patient or to a nearby person, who can drag the rescuer to the scene. In the latter situation, the personnel at the scene must understand the rescue operation and there must have been telephone contact with the on-site personnel.

Unlike most traditional static rope evacuations, in offset rescue operations, the HCM cannot disconnect from the static rope during the preparation of the patient. If a disconnection occurs, no physical contact can be made between the helicopter and the HCM, as the helicopter must be out of plumb from the scene, due to the particular conditions of the terrain. Patients requiring offset technique can often be in complex terrain where there might be a need for the double attachment procedure.

As the helicopter is out of plumb, the HCM and patient can either be evacuated from the scene with a controlled pendulum, or the climber can steer the rescuer and the patient out of the scene using a short tag line controlled with a free-running Munter hitch, as shown in Fig. 4.

The hand signal “free of obstacles” is given by the HCM when the short tag line is free from the scene. The HCM and patient can then be evacuated, underslung, by the helicopter to the rig site, where further treatment can be provided by the emergency physician if necessary. The final step of the rescue operation will remain the same as for all other rescue operations carried out by HEMS.

Voluntary consent was obtained from all crew members before proceeding with data collection from all the potentially involved participants in the study. The study was approved by the Norwegian air ambulance data collection officer, in accordance with the rules from the Norwegian Social Science Data Services.

An overview of the outputs from the SJA is given in Table 1. In the SJA, we systematically review the offset rescue technique by dividing the work into tasks and reviewing each task, to assess the hazards associated with it. In Table 1, the offset rescue operation is split into the following five sub-tasks:

These sub-tasks are the same tasks highlighted in the procedure for the offset technique.

The results from the SJA are based on feedback from five pilots, four HCMs and five emergency physicians. The crew member composition includes highly experienced to less experienced crew members. The dialogue with the different crew members was organized by the authors, consisting of a professor in risk management together with a subject-matter expert HCM and an emergency physician.

Before the dialogue with the different crew members on potential hazards for the different steps of the offset technique, we organized some training sessions related to static rope evacuation. A full training session included (1) a traditional static rope rescue operation with a 30-m and a 60-m rope, (2) an offset rescue technique with a 30-m and a 60-m rope, and (3) an offset rescue technique in really steep terrain, using a 60-m rope. All the training scenarios with the use of the offset technique were conducted in complex terrain, requiring the double attachment procedure [8]. All training missions were conducted in accordance with approved procedures, limitations and risk analysis for static rope rescue missions.

Some crew members did all five training runs, but some only participated in some of the runs. All the crew members that gave input to the SJA participated in at least one of the offset training runs.

In the risk analysis, we focus only on potential hazards associated with the offset rescue technique. Attention is not given to the risks of the different hazards identified. The reason for this must be seen in relation to the aim of our study, whose focus is on the procedure for the offset rescue technique and an evaluation of the same. We then need to gain insight into the extent to which different identified hazards are eliminated or considered, in the way the procedure is described. The classification and categorizations of risks for the identified hazards are then not relevant, given the main aim of our study.

It can be pointed out that hazards which are solely of theoretical interest are omitted from the analysis. This is to avoid making changes to the existing procedure to avoid hazards that are solely of theoretical interest. All the results are shown in Table 1. The main findings from the analysis are given below and categorized for each task of the offset rescue operation.

In the reconnaissance phase, a choice is made as to how the rescue operation should be executed. When deciding upon evacuation by the use of a static rope, one must decide on the length of the rope to be used—one which provides the pilot with good visual references—and, further, on the type of evacuation procedure to be used—the traditional one or the offset technique. Based on the SJA, the choice of rope length has been identified as being more critical when using the offset technique than when using the traditional underlying rescue operation. Two main arguments for this were identified. In an offset rescue operation, a too short rope may contribute to the HCM not reaching the scene. This may happen as the rescuer cannot make ground contact given the helicopter’s offset location. There may also be situations where the length of the rope is sufficient in itself but where the HCM still cannot get to the scene, as dragging him/her to the scene proves too heavy for the climber. To make the work for the climber less heavy, the flight height must be reduced, which is not necessarily possible due to the terrain. This was identified as a problem in one of the training runs.

Compared to the traditional static rope evacuation, it is the arrival at the scene that is different when using the offset rescue technique. During the traditional static rope evacuation, the HEMS crew can arrive at the scene directly. When using the offset technique, you need help from a person at the scene to establish this contact. This can be done with help from volunteer rescue climbers, a person close to the patient or the patient him/herself. In this step of the offset technique, several hazards may occur, as shown in Table 1. Most hazards will just lead to more time being spent before reaching the scene and thereby more time spent before evacuation of the patient can start. But, without the offset technique, one could not gain access to the patient from the helicopter.

From Table 1, we see that there are some situations that may arise during offset operations that affect the safety of the crew members. First, one safety issue which might occur is if the HCM does not complete a final check of his/her personal protection equipment, i.e., harness, attachment to static rope or offset throw line. This hazard is very unlikely to occur, due to the established checklists, safety barriers and routines before a rescue mission is executed. Second, there is a risk of the helicopter being positioned too close to the terrain, which might pose a serious hazard for the whole helicopter crew. During a rescue mission in cooperation with climbers, rappel ropes might also pose an additional hazard for the helicopter. Third, there is a risk of the offset throw line accidentally becoming entangled with a fixed object at the accident site. The weak link on the throw line is designed as a safety barrier if this should occur.

In the offset technique, the helicopter and the HCM may lose contact with the scene. This will happen if the rescuer disconnects from the helicopter during the offset operation. This should not be done, as is clearly described and specified in the procedure for the offset technique. This aspect should also be highlighted in the briefing between the crew members before an offset rescue operation starts.

In addition to this, by using the offset technique, one will sometimes end up in a situation where the HCM is connected to both the helicopter and to the scene at the same time, due to complex terrain and use of the double attachment procedure. Critical situations may then arise if the helicopter is not able to maintain a steady hover. This might also be a hazard in a traditional static rope evacuation when using the double attachment procedure. Should this emergency occur, the helicopter has the possibility to disconnect the rope from the helicopter, hence allowing for a fly away. Disconnecting the rope from the helicopter represents a serious hazard for the HCM hanging at the end of the rope and is only to be used in an emergency as a last option.

Using the offset technique, the HCM and patient can leave the scene autonomously using a controlled pendulum. If using the short tag line when leaving the scene, there is a need for a climber to control the free-running Munter hitch.

In cooperation with climbers, it is important that the climbers are thoroughly briefed on the offset technique in advance. In one of the training runs, where a controlled pendulum was not possible due to obstacles in the evacuation axis, a situation was identified where the climber did not follow the offset procedure: he/she did not control the Munter hitch on the short tag line when the HCM was leaving the scene, allowing for a pendulum. There can be several reasons why one does not follow the procedure. One reason could be that the climber was not thoroughly briefed in advance. Another reason is that the extent of the job task itself is complex, which contributes to difficulties in following the procedure as intended. A third reason is that one does not fully understand what was conveyed in the briefing. The procedure in itself is not difficult, but we discover that it can be fruitful to explain during the briefing not only what to do but why things should be done as described in the procedure. A fourth and probably most likely reason is that most climbers are not used to operating in a helicopter rescue environment. This has been observed in several similar situations and might have affected the overall stress level of the climber, allowing for an adverse event to happen.

During the risk analysis workshop, it was highlighted that the use of the short tag line is of special importance if obstacles are present when leaving the scene and in the evacuation axis (e.g., a canyon/gully), underslung, by the helicopter to the rig site. Without the use of the short tag line, there will be a risk of a strong pendulum movement when the HCM and the patient leave the scene, which may have an impact on the safety of both the rescuer and the patient, due to the terrain.

After leaving the scene and evacuation, underslung, by the helicopter to the rig site, one needs to retrieve the climber(s). This can be done by using the offset technique or by the climbers themselves. What happens after having flown out of the scene with a patient will not have an impact on the offset procedure. All hazards that may occur during a possible retrieval of the climber(s) will be taken care of by conditions that are covered in the sub-task ‘Leaving the scene and evacuation, underslung, by the helicopter to the rig site’.

Based on this study, we consider that the procedure for the offset rescue technique is safe and appropriate, but that there is a need for some adjustments. In this paper, we highlight the importance of clarifying ‘why’ for some of the aspects in the procedure, and not only focusing on what to do. Experiences with training on the offset technique, in addition to interviews with several crew members, show that information on ‘why’ may lead to better communication between the crew members and between the crew members and the climber(s) during their briefing on what to do before offset evacuation. Potential hazards may then be avoided. We also recommend that the HCM has access to two throw lines and regularly trains on the manual skills of throwing the offset line. The present work has contributed to changes in the existing procedure for implementing the offset rescue technique.