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
