Confined Area Approach
This procedure is used when landing almost anywhere off airport, but
especially when the area is fairly small.
The maneuver starts long before the approach. The pilot needs to come up
with a strategy of how best to get in, and then out, of the confined area.
One mneumonic is "SBATT" which stands for Suitability, Barriers,
Approach, Touchdown, Takeoff.
When determining Suitability, the pilot is examining many factors. Some
of these would be issues like "do I have permission", "is it legal",
"is the area big enough", "will the helicopter be a nuisance". If the
answer to any of these is "no", the pilot should consider another landing
Barriers refers to the identification of anything we don't want to fly
over or through. This could be physical objects such as mountains, tall
towers or buildings, wires, and also non-physical barriers such as noise
sensitive areas, areas with large number of people outdoors (athletic fields,
schools), or some kind of restricted or prohibited airspace. After finding
all the barriers, what is left over can be used for the approach and departure.
Approach means determining the best way in and out of a landing
area. There are almost always many ways to approach a landing, but some
ways may be better than others. New pilots often just set up the approach
to be into the wind, and leave it at that. But the wind is only one small
part of figuring out the approach. Factors that should be considered are
approach paths which are within reach of good emergency landing areas if
the engine should quit, the possibility of turbulence, the height of
obstacles which will have to be cleared on approach, and the annoyance factor
of the people on the ground. Although a downwind approach usually should be
avoided, by taking a crosswind the pilot may gain many other advantages.
Touchdown means selecting the touchdown spot. Usually we try to select an
area in the last 1/3 of the LZ because this makes our approach angle
shallower, and increases the chance of us making the landing zone if the
engine quits on short final. There are other factors which may make us
select a different touchdown area, though. For instance, the touchdown
spot needs to be one we can either perform a takeoff from, or which lets
us hover to a spot from which a takeoff can succeed.
Takeoff means plan the route of takeoff so that it is not downwind,
doesn't fly through or into any of the barriers we have identified,
and has good emergency landing areas available.
The High Recon
Keep in mind that all this planning is going on well before the pilot
starts the approach. Usually this is done from a high recon,
which is often done by overflying the LZ at 500 feet. As the pilot overflies
the spot, he goes through SBATT and comes up with a strategy.
Once the approach path is determined, the pilot can figure out his relation
to that approach path, and fly a standard traffic pattern which will align
final approach with the chosen approach path. Some pilots don't fly a traffic
pattern, they just sort of spiral into the approach, but I like to fly a
rectangular traffic pattern so that all the things that go on during approach
occur at their normal time. The largest difference is that I usually fly
a much tighter, slower traffic pattern than at an airport.
The Low Recon
There are several different ideas out there of what constitutes a low
recon. I have always been taught that the low recon occurs while on
approach, the idea being that as the pilot gets lower and slower he is
constantly re-evaluating his plans based on new information he gets.
I know some pilots who believe a low recon means overflying the LZ at
100-200 feet in order to spot details which are not visible from higher
altitude. While I like the idea of giving the area a closer look, flying
100-200 feet over houses, schools, and shopping centers doesn't seem like
such a good idea to me, from a community relations standpoint. I would use
this option if I was out in the boonies, or I had good reason to believe
that I needed a close look before setting up my approach.
My general rule is that the tighter the spot, or the less familiar I am
with the area, the slower I fly final. This gives me more time to see
and avoid surprises. Also, the steeper the approach angle, the slower I
fly, because I'm trying to avoid settling with power. The descent rate
required on approach is directly proportional to the speed and angle. To
keep a low descent rate (below 300 feet per minute before losing effective
translational lift), either the angle or the speed needs to be low.
Therefore a high angle requires a low speed.
Depending on the place we are landing, my descision to commit to a landing
is dependent on a few major factors: power available and obstacle clearance.
If I have lots of power so I can go straight up if I need to, I don't have
to commit to a landing because of obstacles. I can always just pull up on
collective and climb right out. It's pretty rare to have that much power,
though. Usually I need to have ETL (effective translational lift), and a
reasonable amount of obstacle clearance. As a rule of thumb, once I'm below
the tops of the obstacles, I'm committed to land. Like any rule of thumb,
it doesn't apply to all circumstances, but the point is to be thinking about
this on short final, and to have a plan of action if something goes
Confined area landings usually require the pilot to be alert to a few
things. The first is that extreme caution needs to be used with regard
to the tail rotor. Confined areas often have lots of bushes or other
obstacles which can destroy a tail rotor. Part of selecting the landing
area is to select the exact spot the pilot is going to place the tail
rotor. The main rotor will usually be above the smaller obstacles, and
in the event it does contact an obstacle, it's usually much more able
to stand up to the abuse than a tailrotor would be. If the helicopter
has to be hovered around inside the landing area, the pilot should be
devoting much of his attention to where the tailrotor is.
Usually a maximum performance takeoff will
be used to depart a confined area. It is important for the pilot to have
planned the departure route while doing the high recon, because often when
he is inside the confined area he can't see the surrounding area well enough
to plan a good departure. Generally the takeoff should be with a head or
cross wind, and the ground track should avoid the barriers identified on
the high recon. If the helicopter is unable to clear the obstacles, the
pilot should abort the takeoff early enough to allow him to land back on
the spot he just took off from.
paul at copters.com
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