HELICOPTER EVACUATION OF THE INJURED PATIENT

Charles Shimanski

Executive Director, The American Alpine Club

In the past fifteen years, nothing has changed search and rescue (SAR) work more dramatically than the development and refinement of helicopters, and their increasing availability. The Army, local television stations, and private services often provide them for SAR work with a momentís notice. It is, therefore, essential that everyone involved in rescue operations have a thorough orientation to helicopter safety. As a search and reconnaissance platform coupled with rescue and extrication capabilities, the helicopter is unparalleled in its versatility for emergency and disaster response.

But helicopters can be extremely dangerous. With rotors turning at over 150 mph, the hazard to searchers is very real. Another danger in helicopter operations is crashesóin Colorado alone, there have been six in ten years. Helicopters are only as good as the pilots flying them and pilots are only as good as the machines that they are flying. The three major killers of helicopter pilots are wind, weather, and wires.

Despite these tragedies, helicopters are among the safest form of transportation; one has a far better chance of surviving a helicopter crash than a fixed-wing crash because the forward speed that helicopters have to maintain in order to avoid stall is less. What usually kills and injures people in crashes is not the impact with the ground (unless of course the craft is in a stall), but rather the forward momentum they have when they are landing. In addition, more helicopter fatalities result from fire in the aircraft after the crash than from trauma received in the crash itself.

Use of Helicopters

Fixed-wing aircraft are generally best suited for searching large open landóareas above the timberline, for exampleóthey are useful in spotting obvious clues such as ski tracks, tents, and downed aircraft. Helicopters are better for more specialized missions, to search areas more difficult to spot from fixed-wing aircraft, such as cliffs and gullies, for example. Helicopters make a lot of noise. This may help attract the victim of a search who, in turn, may attempt to attract the attention of those on board the helicopter. Helicopters can be used to transport searchers and/or equipment to remote search and rescue assignments, reducing time and energy spent by rescuers, and to help extricate victims by a number of methods, including hoists and slings. And perhaps most importantly, helicopters can be used to evacuate and transport injured victims to nearby hospitals.

Aero-Medical Helicopters

Today most search and rescue teams have access to local "aero-medical" helicopters. And since most rescue missions do occur within proximity of a large town or city, there is usually also access to a Class I trauma center. Flight nurses who are specially qualified in critical care and medicine generally accompany each aero-medical flight. A physician may be present on flights where the need is indicated, though this is uncommon. These ships can usually carry anywhere from two to four supine adult patients, depending on the type of craft and internal configuration.

Emergency medical equipment included on most such helicopters include electrocardiograph monitors, oxygen, defibrillator, suction apparatus, endotracheal intubation equipment, intravenous fluids, transport isolettes, and emergency drugs. These "air ambulance" services provide immediate response by an emergency medical team going to the patient via aircraft who can start intensive therapy at the site of the illness or injury. Once the patient is stabilized he/she is transported as rapidly as possible to the appropriate hospital. In effect, the emergency room is carried to the patient for immediate treatment and care.

Whenever an aero-medical helicopter responds to a mission, search and rescue team members should refrain from talking to the flight nurse or pilot. The only person who should discuss the patient with the flight nurse is the primary medical team member, who will give the flight nurse a full (and brief) update of the patientís condition, nature of injuries, and other important pertinent facts. The helipad director or person most familiar with helicopter operations should be the only person to speak with the pilot while the ship is on the ground.

SAR team members should be aware of how aero-medical helicopters are dispatched. In most cases, this will be via the local Sheriffís dispatch, although some SAR teams may be able to directly request these helicopters. In any event, these specially equipped helicopters should be put on stand-by before rescuers are on-scene, if the description of the rescue indicates that an aero-medical helicopter may be necessary. By doing so, the pilot and flight crew can familiarize themselves with the terrain and weather conditions before they are actually called on a "chopper go."

Helicopter Limitations

Opportunities for helicopter use during emergency operations must be weighed heavily against the risks involved. Search and rescue teams must be aware of the limitations of helicopters when calling for these expensive resources. Conditions such as altitude, weather and terrain will all affect the usefulness of helicopters in search and rescue operations. All aircraft are limited in their working altitude (called "service ceiling"), which can change based on the temperature and humidity.

Visibility Minimums

Smaller helicopters generally do not have "Instrument Flight Rules" (IFR) capability, and must fly under "Visual Flight Rules" (VFR). VFR for helicopters is different from VFR for fixed-wing aircraft due to the difference in the slowest possible speed of forward flight. Generally speaking, VFR for helicopters means flight conditions should be "clear of clouds and at an airspeed that enables the pilot to see and avoid collision."

VFR rules dictate that there must be a minimum of 1û2-mile visibility and a 500-foot ceiling (distance between ground and bottom of lowest clouds). For National Guard helicopters, the visibility for VFR, is increased to 1 mile. A pilot flying under VFR must have sight of the ground at all times. During night flying, VFR dictates that there must be a minimum 3-mile visibility.

Instrument Flight Rules (IFR) are those that apply to aircraft with special navigational instruments that give the pilot greater capability in otherwise difficult flying conditions. IFR allows for flying in conditions where electronics provide the pilot with information not available through the naked eye. Larger helicopters, such as most of those used in search and rescue operations, either have or are capable of instrument flight capability and can fly under instrument flight rules.

Weather Conditions

Turbulence can be a serious problem to a pilot. As a rule there is less turbulence in the morning, making this the best time for flights. In the afternoon the heating of the air by the sun increases turbulence. Cumulus clouds indicate turbulence and strong updrafts and downdrafts. Also, there are often downdrafts over the middle of a valley, and such currents may be dangerous at high elevations because of reduced engine power. Conversely, updrafts often exist over ridges or on the sunny side of ridges. The leeward side of ridges may have severe downdrafts.

Even if a helicopter is on its way to evacuate a victim, ground personnel should still be dispatched to the scene with the equipment necessary to transport the victim, in the event of a helicopter malfunction, changes in weather, or other unexpected complications. Never assume a helicopter en route will become a helicopter on scene.

Fuel

Each type of helicopter has a limited range due to a limited fuel supply, especially since they are generally based at some distance from the typical mountain search and rescue mission. In the case of extended search missions, a mobile fuel tanker might be considered at the heliport to refuel the helicopters. Otherwise, the helicopters will have to leave the scene to refuel, causing the loss of valuable time and resources.

Basic Helicopter Safety

Landing Zones (Helispots)

Contrary to popular belief, helicopters do not normally land "on a dime," but rather require or desire a sizable landing zone, particularly at higher elevation. Helicopters generally will not take off or land vertically. Rather, they need a landing zone (often called an "LZ," referred to throughout this article as a "helispot") that may be hundreds of feet long. The ideal helispot is a flat strip 100 feet wide and 300 feet long (roughly the size of a football field). Flat ridges and saddles may provide the best helispots in the field. Highways, streets or roads unobstructed by outlying trees are suitable as well, but in this case traffic and crowd control must be available by law enforcement authorities. A prime reason for the large landing area is that in case of engine failure (more common upon takeoff due to high engine stress) the helicopter needs extra room to land safely.

Two technical issues must be discussed which effect the performance of helicopters. "In Ground Effect" (IGE) is the effect on the performance of a helicopter by the return of the rotor wash from the ground. As the helicopterís main rotor turns, it creates a cushion of air beneath the hovering helicopter furnishing additional lift caused by the air that is compressed beneath the helicopter. Once the helicopter is above the ground by a distance equal to the diameter of the main rotor, IGE is usually reduced to nothing. Conversely, "Out of Ground Effect" (OGE) occurs when the rotor wash is not affected by the proximity to the ground. In OGE, a helicopter is power dependent when a hover is maintained. This can occur near the ground as well when the helicopter is hovering over tall grass, water, and certain types of rough terrain. If the pilot is instructed to try to land in these conditions, the helispot should be described as an "OGE Helispot." IGE explains why some helicopters can lift less payload by sling than they can on board.

Helispots should be defined in such a way that the helicopter can land and take off into the wind to increase lift. Only as a last resort, a "hover hole" helispot can be chosen. This is a landing zone where, due to size restrictions, the pilot must slow to a hover above the landing area and then descend to the ground. When taking off, the pilot must use all available engine power, which leaves no room for error. The dangers are obvious; therefore, "hover holes" should be avoided at all costs.

Since the typical helicopter will kick up rotor wash in excess of 100 mph on takeoffs and landings (significantly more on Chinooks), the helispot should be free of lightweight objects that will blow away. Tall grass and shrubs should be avoided to prevent possible damage to the sensitive tail rotor. Tree stumps should be less than one foot high. A snowfield can make a good helispot, but markers such as backpacks must be place near the helispot to give the pilot some sense of depth perception.

Night operations are becoming more common with the availability of instrument flight rules. Since night landings and takeoffs are significantly more dangerous. SAR team leaders must consider the risks versus benefits of performing such operations. If this is absolutely necessary, the pilot must be advised of optimal flight paths to avoid hazards such as trees, peaks, ridges, and especially, power lines. At night, the helispot may be marked by rescuerís headlamp held on and aimed steady, without wavering. If the helispot is near the Incidence Command Post, two vehicles with headlights on, located 40 yards downwind and at opposing 45-degree angles to the proposed helispot, may illuminate the helispot. The helicopter will then approach between the two vehicles and will land near the intersection of the lights, roughly 40 yards upwind from the vehicles. These vehicles should have low beams on to avoid blinding the pilot or flooding the instrument panel with light. In the event that the pilot cannot locate the proposed helispot, due to other surface lights in the area, emergency vehicle lights can be illuminated. As the helicopter approaches, all lights should be out except those used to illuminate hazards and the touchdown pad. All strobes and rotating beacons must be shut off as well; such lights can cause the pilot to experience vertigo and affect his/her perception of the horizon.

Landings and Takeoffs

Landings and takeoffs are generally made easier in the presence of a light, steady breeze (such as 10 knots or 12 mph) than in still air. But pilots may choose not to take off or land in a wind greater than 45 knots (approximately 50 mph) or with a gust spread of over 20 knots (23 mph).

When landing, a pilot will often make a high level pass over the heliport for observation of obstacles and wind indicators and then will come in on a "final approach" (a.k.a. "final"). Despite the tendency to watch during this approach, all personnel not in the helispot should look away to avoid injury by flying debris kicked up by the rotor wash, especially from Chinooks. Ground personnel must hold down any loose gear.

During final approach, only one ground person should be in the helispot. This person is referred to as the "parking tender." With the helicopter some distance away, the touchdown point is indicated by the parking tender standing upwind with his/her back to the wind and his/her arms facing toward the desired landing spot. During landings on snow, no rescuers should be in the landing zone at any time. There is always the chance that the helicopterís weight will cause it to settle in the snow, which could be dangerous to rescuers in the helispot.

Hand Signals

If the pilot is to be given hand signals by the rescuer, the pilot must be told where this person is and what he/she is wearing. The rescuer must be familiar with the standard hand signals or should stay away. This is no time to use arbitrary signals that could be misinterpreted by the pilot. For example, guide a helicopter pilot to a landing zone by waving your arms back and forth and the pilot will avoid you like the plague. Such waving is the universal "wave-off" signal that tells the pilot not to land! In a recent SAR mission, field team members who were expecting a helicopter ride back to the Incident Command Post were left in the field because they used the "wave-off" to catch the pilotís attention. The pilot did see them and interpreted this as a signal to leave the areas, and he did so. The resultóa long walk out for the field team. The problem with the "wave-offí signal is that it is the instinctive reaction to alert a helicopter of your location. Be careful not to use it unless you are using it appropriately.

When a helicopter is landing at a helispot, it may be necessary to have a SAR member acting as a helispot parking tender, guiding the pilot to the helispot with hand signals. These hand signals are as follows. First, as the helicopter makes its high level pass and as it begins its final approach, the helispot parking tender stands at the end of the heliport with his/her back to the wind. The arms are extended towards the landing area, which means, "Land here facing me, my back is toward the wind." Then as the helicopter approaches the helispot, the parking tender extends his or her arms outward with clenched fists, which means, "Hold your hover." As the helicopterís skids or wheels touch the ground, the parking tender should hold his or her arms extended outward at a 45-degree angle to the ground with the thumbs pointing downward. This says to the pilot "Hold your helicopter on the ground." Then, if the helicopter is to come to a full rotor stop, the parking tender crosses the neck with the right palm facing down (a.k.a. "kill it"). This means "shut down your engine(s)."

If the parking tender is confident that the pilot is on final approach to the desired heliport, there may be no reason to continue to stand in the middle of the heliport and get blasted by the rotor wash. The parking tender may wish to alert the pilot that he/she will move away from the heliport as it approaches.

Rest assured that the pilot might often choose to ignore a rescuer giving hand signals. It is not because the pilot is not familiar with them. Rather, a cautious pilot may be uncertain as to whether or not the rescuer is indeed familiar with the signals, and may not trust the rescuer. After all, pilots are not mind readers, and they have every right to trust themselves more than a stranger. Furthermore, the pilot may be more aware of weather conditions, such as wind gusts and visible terrain and may choose his or her own angle of approach. Nevertheless, a simple understanding of these signals is valuable and should be known by every search and rescue person who may work around helicopters.

Wilderness Medicine Letter, Volume 17, Number 3, Summer 2000