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(blade flex, aircraft movement).
2.See National Fire Protection Association (NFPA)
Document 407, Standard for Aircraft Fuel
Servicing" for specifics regarding non−HRR (routine
refueling operations).
ENR 6.2−8 AIP
15 MAR 07 United States of America
Nineteenth Edition Federal Aviation Administration
2. Helicopter Night VFR Operations
2.1Effect of Lighting on Seeing Conditions in
Night VFR Helicopter Operations
NOTE−
This guidance was developed to support safe night VFR
helicopter emergency medical services (HEMS)
operations. The principles of lighting and seeing
conditions are useful in any night VFR operation.
While ceiling and visibility significantly affect safety
in night VFR operations, lighting conditions also
have a profound effect on safety. Even in conditions
in which visibility and ceiling are determined to be
visual meteorological conditions, the ability to
discern unlighted or low contrast objects and terrain
at night may be compromised. The ability to discern
these objects and terrain is the seeing condition, and
is related to the amount of natural and man made
lighting available, and the contrast, reflectivity, and
texture of surface terrain and obstruction features. In
order to conduct operations safely, seeing conditions
must be accounted for in the planning and execution
of night VFR operations.
Night VFR seeing conditions can be described by
identifying high lighting conditions" and low
lighting conditions."
2.1.1High lighting conditions exist when one of
twosets of conditions are present:
2.1.1.1The sky cover is less than broken (less than
5/8 cloud cover), the time is between the local Moon
rise and Moon set, and the lunar disk is at least
50%illuminated; or
2.1.1.2The aircraft is operated over surface lighting
which, at least, provides for the lighting of prominent
obstacles, the identification of terrain features
(shorelines, valleys, hills, mountains, slopes) and a
horizontal reference by which the pilot may control
the helicopter. For example, this surface lighting may
be the result of:
a)Extensive cultural lighting (man−made, such as
a built−up area of a city),
b)Significant reflected cultural lighting (such as
the illumination caused by the reflection of a major
metropolitan area’s lighting reflecting off a cloud
ceiling), or
c)Limited cultural lighting combined with a high
level of natural reflectivity of celestial illumination,
such as that provided by a surface covered by snow or
a desert surface.
2.1.2Low lighting conditions are those that do not
meet the high lighting conditions requirements.
2.1.3Some areas may be considered a high lighting
environment only in specific circumstances. For
example, some surfaces, such as a forest with limited
cultural lighting, normally have little reflectivity,
requiring dependence on significant moonlight to
achieve a high lighting condition. However, when
that same forest is covered with snow, its reflectivity
may support a high lighting condition based only on
starlight. Similarly, a desolate area, with little cultural
lighting, such as a desert, may have such inherent
natural reflectivity that it may be considered a high
lighting conditions area regardless of season,
provided the cloud cover does not prevent starlight
from being reflected from the surface. Other surfaces,
such as areas of open water, may never have enough
reflectivity or cultural lighting to ever be characterized
as a high lighting area.
2.1.4Through the accumulation of night flying
experience in a particular area, the operator will
develop the ability to determine, prior to departure,
which areas can be considered supporting high or low
lighting conditions. Without that operational experience,
low lighting considerations should be applied
by operators for both pre−flight planning and
operations until high lighting conditions are observed
or determined to be regularly available.
2.2Astronomical Definitions and Background
Information for Night Operations
2.2.1Definitions
2.2.1.1Horizon.Wherever one is located on or near
the Earth’s surface, the Earth is perceived as
essentially flat and, therefore, as a plane. If there are
no visual obstructions, the apparent intersection of
the sky with the Earth’s (plane) surface is the horizon,
which appears as a circle centered at the observer. For
rise/set computations, the observer’s eye is considered
to be on the surface of the Earth, so that the
　
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