Accident Cause Factors
The 10 most frequent cause factors for
general aviation accidents that involve the
preflight preparation and/or planning.
2. Failure to obtain
and/or maintain flying speed.
3. Failure to
maintain direction control.
4. Improper level
5. Failure to see
and avoid objects or obstructions.
6. Mismanagement of
7. Improper inflight
decisions or planning.
8. Misjudgment of
distance and speed.
9. Selection of
operation of flight controls.
This list remains relatively stable and
points out the need for continued refresher training to
establish a higher level of flight proficiency for all
pilots. A part of the FAA's continuing effort to promote
increased aviation safety is the Aviation Safety
Program. For information on Aviation Safety Program
activities contact your nearest Flight Standards
Be alert at all times, especially
when the weather is good. Most pilots pay attention to
business when they are operating in full IFR weather
conditions, but strangely, air collisions almost
invariably have occurred under ideal weather conditions.
Unlimited visibility appears to encourage a sense of
security which is not at all justified. Considerable
information of value may be obtained by listening to
advisories being issued in the terminal area, even
though controller workload may prevent a pilot from
obtaining individual service.
d. Giving Way.
If you think another aircraft is too
close to you, give way instead of waiting for the other
pilot to respect the right-of-way to which you may be
entitled. It is a lot safer to pursue the right-of-way
angle after you have completed your flight.
7-5-2. VFR in
A high percentage of near
midair collisions occur below 8,000 feet AGL and within 30
miles of an airport. When operating VFR in these highly
congested areas, whether you intend to land at an airport
within the area or are just flying through, it is
recommended that extra vigilance be maintained and that
you monitor an appropriate control frequency. Normally the
appropriate frequency is an approach control frequency. By
such monitoring action you can "get the picture" of the
traffic in your area. When the approach controller has
radar, radar traffic advisories may be given to VFR pilots
AIM, Radar Traffic Information Service, Paragraph 4-1-14.
Obstructions To Flight
Many structures exist that could
significantly affect the safety of your flight when
operating below 500 feet AGL, and particularly below 200
feet AGL. While 14 CFR Part 91.119 allows flight below
500 AGL when over sparsely populated areas or open
water, such operations are very dangerous. At and below
200 feet AGL there are numerous power lines, antenna
towers, etc., that are not marked and lighted as
obstructions and; therefore, may not be seen in time to
avoid a collision. Notices to Airmen (NOTAM's) are
issued on those lighted structures experiencing
temporary light outages. However, some time may pass
before the FAA is notified of these outages, and the
NOTAM issued, thus pilot vigilance is imperative.
b. Antenna Towers.
Extreme caution should be
exercised when flying less than 2,000 feet AGL because
of numerous skeletal structures, such as radio and
television antenna towers, that exceed 1,000 feet AGL
with some extending higher than 2,000 feet AGL. Most
skeletal structures are supported by guy wires which are
very difficult to see in good weather and can be
invisible at dusk or during periods of reduced
visibility. These wires can extend about 1,500 feet
horizontally from a structure; therefore, all skeletal
structures should be avoided horizontally by at least
2,000 feet. Additionally, new towers may not be on your
current chart because the information was not received
prior to the printing of the chart.
c. Overhead Wires.
Overhead transmission and utility lines often span
approaches to runways, natural flyways such as lakes,
rivers, gorges, and canyons, and cross other landmarks
pilots frequently follow such as highways, railroad
tracks, etc. As with antenna towers, these high
voltage/power lines or the supporting structures of
these lines may not always be readily visible and the
wires may be virtually impossible to see under certain
conditions. In some locations, the supporting structures
of overhead transmission lines are equipped with unique
sequence flashing white strobe light systems to indicate
that there are wires between the structures. However,
many power lines do not require notice to the FAA and,
therefore, are not marked and/or lighted. Many of those
that do require notice do not exceed 200 feet AGL or
meet the Obstruction Standard of 14 CFR Part 77 and,
therefore, are not marked and/or lighted. All pilots are
cautioned to remain extremely vigilant for these power
lines or their supporting structures when following
natural flyways or during the approach and landing
phase. This is particularly important for seaplane
and/or float equipped aircraft when landing on, or
departing from, unfamiliar lakes or rivers.
other objects or structures that could adversely affect
your flight such as construction cranes near an airport,
newly constructed buildings, new towers, etc. Many of
these structures do not meet charting requirements or
may not yet be charted because of the charting cycle.
Some structures do not require obstruction marking
and/or lighting and some may not be marked and lighted
even though the FAA recommended it.
Avoid Flight Beneath Unmanned Balloons
The majority of unmanned free balloons
currently being operated have, extending below them,
either a suspension device to which the payload or
instrument package is attached, or a trailing wire
antenna, or both. In many instances these balloon
subsystems may be invisible to the pilot until the
aircraft is close to the balloon, thereby creating a
potentially dangerous situation. Therefore, good
judgment on the part of the pilot dictates that aircraft
should remain well clear of all unmanned free balloons
and flight below them should be avoided at all times.
Pilots are urged to report any unmanned
free balloons sighted to the nearest FAA ground facility
with which communication is established. Such
information will assist FAA ATC facilities to identify
and flight follow unmanned free balloons operating in
Your first experience of flying over
mountainous terrain (particularly if most of your flight
time has been over the flatlands of the midwest) could
be a never-to-be-forgotten nightmare if proper
planning is not done and if you are not aware of the
potential hazards awaiting. Those familiar section lines
are not present in the mountains; those flat, level
fields for forced landings are practically nonexistent;
abrupt changes in wind direction and velocity occur;
severe updrafts and downdrafts are common, particularly
near or above abrupt changes of terrain such as cliffs
or rugged areas; even the clouds look different and can
build up with startling rapidity. Mountain flying need
not be hazardous if you follow the recommendations
b. File a Flight Plan.
Plan your route to avoid
topography which would prevent a safe forced landing.
The route should be over populated areas and well known
mountain passes. Sufficient altitude should be
maintained to permit gliding to a safe landing in the
event of engine failure.
Don't fly a light aircraft when the winds
aloft, at your proposed altitude, exceed 35 miles per
hour. Expect the winds to be of much greater velocity
over mountain passes than reported a few miles from
them. Approach mountain passes with as much altitude as
possible. Downdrafts of from 1,500 to 2,000 feet per
minute are not uncommon on the leeward side.
Don't fly near or above abrupt changes in
terrain. Severe turbulence can be expected, especially
in high wind conditions.
e. Understand Mountain
Obscuration. The term Mountain
Obscuration (MTOS) is used to describe a visibility
condition that is distinguished from IFR because
ceilings, by definition, are described as "above ground
level" (AGL). In mountainous terrain clouds can form at
altitudes significantly higher than the weather
reporting station and at the same time nearby
mountaintops may be obscured by low visibility. In these
areas the ground level can also vary greatly over a
small area. Beware if operating VFR-on-top. You could be
operating closer to the terrain than you think because
the tops of mountains are hidden in a cloud deck below.
MTOS areas are identified daily on The Aviation Weather
Center located at www.awc-kc.noaa.gov under Official
Forecast Products, AIRMET's (WA), IFR/Mountain
Some canyons run into a dead end. Don't
fly so far up a canyon that you get trapped. ALWAYS BE
ABLE TO MAKE A 180 DEGREE TURN!
VFR flight operations may be conducted at
night in mountainous terrain with the application of
sound judgment and common sense. Proper pre-flight
planning, giving ample consideration to winds and
weather, knowledge of the terrain and pilot experience
in mountain flying are prerequisites for safety of
flight. Continuous visual contact with the surface and
obstructions is a major concern and flight operations
under an overcast or in the vicinity of clouds should be
approached with extreme caution.
When landing at a high altitude field,
the same indicated airspeed should be used as at low
elevation fields. Remember: that due to the less
dense air at altitude, this same indicated airspeed
actually results in higher true airspeed, a faster
landing speed, and more important, a longer landing
distance. During gusty wind conditions which often
prevail at high altitude fields, a power approach and
power landing is recommended. Additionally, due to the
faster groundspeed, your takeoff distance will increase
considerably over that required at low altitudes.
i. Effects of Density
Altitude. Performance figures
in the aircraft owner's handbook for length of takeoff
run, horsepower, rate of climb, etc., are generally
based on standard atmosphere conditions (59 degrees
Fahrenheit (15 degrees Celsius), pressure 29.92 inches
of mercury) at sea level. However, inexperienced pilots,
as well as experienced pilots, may run into trouble when
they encounter an altogether different set of
conditions. This is particularly true in hot weather and
at higher elevations. Aircraft operations at altitudes
above sea level and at higher than standard temperatures
are commonplace in mountainous areas. Such operations
quite often result in a drastic reduction of aircraft
performance capabilities because of the changing air
density. Density altitude is a measure of air density.
It is not to be confused with pressure altitude, true
altitude or absolute altitude. It is not to be used as a
height reference, but as a determining criteria in the
performance capability of an aircraft. Air density
decreases with altitude. As air density decreases,
density altitude increases. The further effects of high
temperature and high humidity are cumulative, resulting
in an increasing high density altitude condition. High
density altitude reduces all aircraft performance
parameters. To the pilot, this means that the normal
horsepower output is reduced, propeller efficiency is
reduced and a higher true airspeed is required to
sustain the aircraft throughout its operating
parameters. It means an increase in runway length
requirements for takeoff and landings, and decreased
rate of climb. An average small airplane, for example,
requiring 1,000 feet for takeoff at sea level under
standard atmospheric conditions will require a takeoff
run of approximately 2,000 feet at an operational
altitude of 5,000 feet.
A turbo-charged aircraft engine provides some slight
advantage in that it provides sea level horsepower up to
a specified altitude above sea level.
1. Density Altitude
Advisories. At airports with
elevations of 2,000 feet and higher, control towers
and FSS's will broadcast the advisory "Check Density
Altitude" when the temperature reaches a predetermined
level. These advisories will be broadcast on
appropriate tower frequencies or, where available,
ATIS. FSS's will broadcast these advisories as a part
of Local Airport Advisory, and on TWEB.
These advisories are provided by air
traffic facilities, as a reminder to pilots that high
temperatures and high field elevations will cause
significant changes in aircraft characteristics. The
pilot retains the responsibility to compute density
altitude, when appropriate, as a part of preflight
All FSS's will compute the current density altitude
j. Mountain Wave.
Many pilots go all their lives
without understanding what a mountain wave is. Quite a
few have lost their lives because of this lack of
understanding. One need not be a licensed meteorologist
to understand the mountain wave phenomenon.
Mountain waves occur when air is being
blown over a mountain range or even the ridge of a
sharp bluff area. As the air hits the upwind side of
the range, it starts to climb, thus creating what is
generally a smooth updraft which turns into a
turbulent downdraft as the air passes the crest of the
ridge. From this point, for many miles downwind, there
will be a series of downdrafts and updrafts. Satellite
photos of the Rockies have shown mountain waves
extending as far as 700 miles downwind of the range.
Along the east coast area, such photos of the
Appalachian chain have picked up the mountain wave
phenomenon over a hundred miles eastward. All it takes
to form a mountain wave is wind blowing across the
range at 15 knots or better at an intersection angle
of not less than 30 degrees.
Pilots from flatland areas should
understand a few things about mountain waves in order
to stay out of trouble. When approaching a mountain
range from the upwind side (generally the west), there
will usually be a smooth updraft; therefore, it is not
quite as dangerous an area as the lee of the range.
From the leeward side, it is always a good idea to add
an extra thousand feet or so of altitude because
downdrafts can exceed the climb capability of the
aircraft. Never expect an updraft when approaching a
mountain chain from the leeward. Always be prepared to
cope with a downdraft and turbulence.
When approaching a mountain ridge from
the downwind side, it is recommended that the ridge be
approached at approximately a 45 degree angle to the
horizontal direction of the ridge. This permits a
safer retreat from the ridge with less stress on the
aircraft should severe turbulence and downdraft be
experienced. If severe turbulence is encountered,
simultaneously reduce power and adjust pitch until
aircraft approaches maneuvering speed, then adjust
power and trim to maintain maneuvering speed and fly
away from the turbulent area.
Use of Runway Half-way Signs at Unimproved Airports
When installed, runway
half-way signs provide the pilot with a reference point to
judge takeoff acceleration trends. Assuming that the
runway length is appropriate for takeoff (considering
runway condition and slope, elevation, aircraft weight,
wind, and temperature), typical takeoff acceleration
should allow the airplane to reach 70 percent of lift-off
airspeed by the midpoint of the runway. The "rule of
thumb" is that should airplane acceleration not allow the
airspeed to reach this value by the midpoint, the takeoff
should be aborted, as it may not be possible to liftoff in
the remaining runway.
Several points are
important when considering using this "rule of thumb":
Airspeed indicators in small airplanes
are not required to be evaluated at speeds below
stalling, and may not be usable at 70 percent of liftoff
This "rule of thumb" is based on a
uniform surface condition. Puddles, soft spots, areas of
tall and/or wet grass, loose gravel, etc., may impede
acceleration or even cause deceleration. Even if the
airplane achieves 70 percent of liftoff airspeed by the
midpoint, the condition of the remainder of the runway
may not allow further acceleration. The entire length of
the runway should be inspected prior to takeoff to
ensure a usable surface.
This "rule of thumb" applies only to
runway required for actual liftoff. In the event that
obstacles affect the takeoff climb path, appropriate
distance must be available after liftoff to accelerate
to best angle of climb speed and to clear the obstacles.
This will, in effect, require the airplane to accelerate
to a higher speed by midpoint, particularly if the
obstacles are close to the end of the runway. In
addition, this technique does not take into account the
effects of upslope or tailwinds on takeoff performance.
These factors will also require greater acceleration
than normal and, under some circumstances, prevent
Use of this "rule of thumb" does not
alleviate the pilot's responsibility to comply with
applicable Federal Aviation Regulations, the limitations
and performance data provided in the FAA approved
Airplane Flight Manual (AFM), or, in the absence of an
FAA approved AFM, other data provided by the aircraft
In addition to their use
during takeoff, runway half-way signs offer the pilot
increased awareness of his or her position along the
runway during landing operations.
Acquiring a seaplane class rating affords
access to many areas not available to landplane pilots.
Adding a seaplane class rating to your pilot certificate
can be relatively uncomplicated and inexpensive.
However, more effort is required to become a safe,
efficient, competent "bush" pilot. The natural hazards
of the backwoods have given way to modern man-made
hazards. Except for the far north, the available bodies
of water are no longer the exclusive domain of the
airman. Seaplane pilots must be vigilant for hazards
such as electric power lines, power, sail and rowboats,
rafts, mooring lines, water skiers, swimmers, etc.
Seaplane pilots must have a thorough
understanding of the right-of-way rules as they apply to
aircraft versus other vessels. Seaplane pilots are
expected to know and adhere to both the U.S. Coast
Guard's (USCG) Navigation Rules, International-Inland,
and 14 CFR Section 91.115, Right-of-Way Rules; Water
Operations. The navigation rules of the road are a set
of collision avoidance rules as they apply to aircraft
on the water. A seaplane is considered a vessel when on
the water for the purposes of these collision avoidance
rules. In general, a seaplane on the water shall keep
well clear of all vessels and avoid impeding their
navigation. The CFR requires, in part, that aircraft
operating on the water ". . . shall, insofar as
possible, keep clear of all vessels and avoid impeding
their navigation, and shall give way to any vessel or
other aircraft that is given the right-of-way . . . ."
This means that a seaplane should avoid boats and
commercial shipping when on the water. If on a collision
course, the seaplane should slow, stop, or maneuver to
the right, away from the bow of the oncoming vessel.
Also, while on the surface with an engine running, an
aircraft must give way to all nonpowered vessels. Since
a seaplane in the water may not be as maneuverable as
one in the air, the aircraft on the water has
right-of-way over one in the air, and one taking off has
right-of-way over one landing. A seaplane is exempt from
the USCG safety equipment requirements, including the
requirements for Personal Flotation Devices (PFD).
Requiring seaplanes on the water to comply with USCG
equipment requirements in addition to the FAA equipment
requirements would be an unnecessary burden on seaplane
owners and operators.
Unless they are under Federal
jurisdiction, navigable bodies of water are under the
jurisdiction of the state, or in a few cases, privately
owned. Unless they are specifically restricted, aircraft
have as much right to operate on these bodies of water
as other vessels. To avoid problems, check with Federal
or local officials in advance of operating on unfamiliar
waters. In addition to the agencies listed in TBL 7-5-1,
the nearest Flight Standards District Office can usually
offer some practical suggestions as well as regulatory
information. If you land on a restricted body of water
because of an inflight emergency, or in ignorance of the
restrictions you have violated, report as quickly as
practical to the nearest local official having
jurisdiction and explain your situation.
When operating a seaplane over or into
remote areas, appropriate attention should be given to
survival gear. Minimum kits are recommended for summer
and winter, and are required by law for flight into
sparsely settled areas of Canada and Alaska. Alaska
State Department of Transportation and Canadian Ministry
of Transport officials can provide specific information
on survival gear requirements. The kit should be
assembled in one container and be easily reachable and
The FAA recommends that each seaplane
owner or operator provide flotation gear for occupants
any time a seaplane operates on or near water. 14 CFR
Section 91.205(b)(12) requires approved flotation gear
for aircraft operated for hire over water and beyond
power-off gliding distance from shore. FAA-approved gear
differs from that required for navigable waterways under
USCG rules. FAA-approved life vests are inflatable
designs as compared to the USCG's noninflatable PFD's
that may consist of solid, bulky material. Such USCG
PFD's are impractical for seaplanes and other aircraft
because they may block passage through the relatively
narrow exits available to pilots and passengers. Life
vests approved under Technical Standard Order (TSO) C13E
contain fully inflatable compartments. The wearer
inflates the compartments (AFTER exiting the aircraft)
primarily by independent CO2 cartridges, with an oral
inflation tube as a backup. The flotation gear also
contains a water-activated, self-illuminating signal
light. The fact that pilots and passengers can easily
don and wear inflatable life vests (when not inflated)
provides maximum effectiveness and allows for
unrestricted movement. It is imperative that passengers
are briefed on the location and proper use of available
PFD's prior to leaving the dock.
Navigable Bodies of Water
Consult For Use of a Body of Water
U.S. Department of
Agriculture, Forest Service
Local forest ranger
USDA Forest Service
Local forest ranger
U.S. Department of
the Interior, National Park Service
Local park ranger
USDI, Bureau of
Local Bureau office
State government or
state forestry or park service
Local state aviation
office for further information
Canadian National and
restricted on an individual basis from province to
province and by different departments of the
Canadian government; consult Canadian Flight
Information Manual and/or Water Aerodrome Supplement
in an emergency
f. The FAA recommends that
seaplane owners and operators obtain Advisory Circular
(AC) 91-69, Seaplane Safety for 14 CFR Part 91
Operations, free from the U.S. Department of
Transportation, Subsequent Distribution Office,
SVC-121.23, Ardmore East Business Center, 3341 Q 75th
Avenue, Landover, MD 20785; fax: (301) 386-5394. The
USCG Navigation Rules International-Inland (COMDTINSTM
16672.2B) is available for a fee from the Government
Printing Office by facsimile request to (202) 512-2250,
and can be ordered using Mastercard or Visa.
Flight Operations in Volcanic Ash
Severe volcanic eruptions which send ash
into the upper atmosphere occur somewhere around the
world several times each year. Flying into a volcanic
ash cloud can be exceedingly dangerous. A B747-200 lost
all four engines after such an encounter and a B747-400
had the same nearly catastrophic experience.
Piston-powered aircraft are less likely to lose power
but severe damage is almost certain to ensue after an
encounter with a volcanic ash cloud which is only a few
Most important is to avoid any encounter
with volcanic ash. The ash plume may not be visible,
especially in instrument conditions or at night; and
even if visible, it is difficult to distinguish visually
between an ash cloud and an ordinary weather cloud.
Volcanic ash clouds are not displayed on airborne or ATC
radar. The pilot must rely on reports from air
traffic controllers and other pilots to determine the
location of the ash cloud and use that information to
remain well clear of the area. Every attempt should be
made to remain on the upwind side of the volcano.
It is recommended that pilots
encountering an ash cloud should immediately reduce
thrust to idle (altitude permitting), and reverse course
in order to escape from the cloud. Ash clouds may extend
for hundreds of miles and pilots should not attempt to
fly through or climb out of the cloud. In addition, the
following procedures are recommended:
Disengage the autothrottle if engaged.
This will prevent the autothrottle from increasing
Turn on continuous ignition;
Turn on all accessory airbleeds
including all air conditioning packs, nacelles, and
wing anti-ice. This will provide an additional engine
stall margin by reducing engine pressure.
The following has been reported by
flightcrews who have experienced encounters with
volcanic dust clouds:
Smoke or dust appearing in the cockpit.
An acrid odor similar to electrical
Multiple engine malfunctions, such as
compressor stalls, increasing EGT, torching from
tailpipe, and flameouts.
At night, St. Elmo's fire or other
static discharges accompanied by a bright orange glow
in the engine inlets.
A fire warning in the forward cargo
It may become necessary to shut down and
then restart engines to prevent exceeding EGT limits.
Volcanic ash may block the pitot system and result in
unreliable airspeed indications.
If you see a volcanic eruption and have
not been previously notified of it, you may have been
the first person to observe it. In this case,
immediately contact ATC and alert them to the existence
of the eruption. If possible, use the Volcanic Activity
Reporting form (VAR) depicted in Appendix 2 of this
manual. Items 1 through 8 of the VAR should be
transmitted immediately. The information requested in
items 9 through 16 should be passed after landing. If a
VAR form is not immediately available, relay enough
information to identify the position and nature of the
volcanic activity. Do not become unnecessarily alarmed
if there is merely steam or very low-level eruptions of
When landing at airports where volcanic
ash has been deposited on the runway, be aware that even
a thin layer of dry ash can be detrimental to braking
action. Wet ash on the runway may also reduce
effectiveness of braking. It is recommended that reverse
thrust be limited to minimum practical to reduce the
possibility of reduced visibility and engine ingestion
of airborne ash.
When departing from airports where
volcanic ash has been deposited, it is recommended that
pilots avoid operating in visible airborne ash. Allow
ash to settle before initiating takeoff roll. It is also
recommended that flap extension be delayed until
initiating the before takeoff checklist and that a
rolling takeoff be executed to avoid blowing ash back
into the air.
Emergency Airborne Inspection of Other Aircraft
Providing airborne assistance to another
aircraft may involve flying in very close proximity to
that aircraft. Most pilots receive little, if any,
formal training or instruction in this type of flying
activity. Close proximity flying without sufficient time
to plan (i.e., in an emergency situation), coupled with
the stress involved in a perceived emergency can be
The pilot in the best position to assess
the situation should take the responsibility of
coordinating the airborne intercept and inspection, and
take into account the unique flight characteristics and
differences of the category(s) of aircraft involved.
Some of the safety considerations are:
Area, direction and speed of the
Aerodynamic effects (i.e., rotorcraft
Minimum safe separation distances;
Communications requirements, lost
communications procedures, coordination with ATC;
Suitability of diverting the distressed
aircraft to the nearest safe airport; and
Emergency actions to terminate the
Close proximity, inflight inspection of
another aircraft is uniquely hazardous. The
pilot-in-command of the aircraft experiencing the
problem/emergency must not relinquish control of the
situation and/or jeopardize the safety of their
aircraft. The maneuver must be accomplished with minimum
risk to both aircraft.
Precipitation static is caused by
aircraft in flight coming in contact with uncharged
particles. These particles can be rain, snow, fog,
sleet, hail, volcanic ash, dust; any solid or liquid
particles. When the aircraft strikes these neutral
particles the positive element of the particle is
reflected away from the aircraft and the negative
particle adheres to the skin of the aircraft. In a very
short period of time a substantial negative charge will
develop on the skin of the aircraft. If the aircraft is
not equipped with static dischargers, or has an
ineffective static discharger system, when a sufficient
negative voltage level is reached, the aircraft may go
into "CORONA." That is, it will discharge the static
electricity from the extremities of the aircraft, such
as the wing tips, horizontal stabilizer, vertical
stabilizer, antenna, propeller tips, etc. This discharge
of static electricity is what you will hear in your
headphones and is what we call P-static.
A review of pilot reports often shows
different symptoms with each problem that is
encountered. The following list of problems is a summary
of many pilot reports from many different aircraft. Each
problem was caused by P-static:
Complete loss of VHF communications.
Erroneous magnetic compass readings (30
percent in error).
High pitched squeal on audio.
Motor boat sound on audio.
Loss of all avionics in clouds.
VLF navigation system inoperative most
of the time.
Erratic instrument readouts.
Weak transmissions and poor receptivity
"St. Elmo's Fire" on windshield.
Each of these symptoms is caused by one
general problem on the airframe. This problem is the
inability of the accumulated charge to flow easily to
the wing tips and tail of the airframe, and properly
discharge to the airstream.
Static dischargers work on the principal
of creating a relatively easy path for discharging
negative charges that develop on the aircraft by using a
discharger with fine metal points, carbon coated rods,
or carbon wicks rather than wait until a large charge is
developed and discharged off the trailing edges of the
aircraft that will interfere with avionics equipment.
This process offers approximately 50 decibels (dB)
static noise reduction which is adequate in most cases
to be below the threshold of noise that would cause
interference in avionics equipment.
It is important to remember that
precipitation static problems can only be corrected with
the proper number of quality static dischargers,
properly installed on a properly bonded aircraft.
P-static is indeed a problem in the all weather
operation of the aircraft, but there are effective ways
to combat it. All possible methods of reducing the
effects of P-static should be considered so as to
provide the best possible performance in the flight
A wide variety of discharger designs is
available on the commercial market. The inclusion of
well-designed dischargers may be expected to improve
airframe noise in P-static conditions by as much as 50
dB. Essentially, the discharger provides a path by which
accumulated charge may leave the airframe quietly. This
is generally accomplished by providing a group of tiny
corona points to permit onset of corona-current flow at
a low aircraft potential. Additionally, aerodynamic
design of dischargers to permit corona to occur at the
lowest possible atmospheric pressure also lowers the
corona threshold. In addition to permitting a
low-potential discharge, the discharger will minimize
the radiation of radio frequency (RF) energy which
accompanies the corona discharge, in order to minimize
effects of RF components at communications and
navigation frequencies on avionics performance. These
effects are reduced through resistive attachment of the
corona point(s) to the airframe, preserving direct
current connection but attenuating the higher-frequency
components of the discharge.
Each manufacturer of static dischargers
offers information concerning appropriate discharger
location on specific airframes. Such locations emphasize
the trailing outboard surfaces of wings and horizontal
tail surfaces, plus the tip of the vertical stabilizer,
where charge tends to accumulate on the airframe.
Sufficient dischargers must be provided to allow for
current-carrying capacity which will maintain airframe
potential below the corona threshold of the trailing
In order to achieve full performance of
avionic equipment, the static discharge system will
require periodic maintenance. A pilot knowledgeable of
P-static causes and effects is an important element in
assuring optimum performance by early recognition of
these types of problems.
Light Amplification by Stimulated Emission of Radiation
Lasers have many applications. Of concern
to users of the National Airspace System are those laser
events that may affect pilots, e.g., outdoor laser light
shows or demonstrations for entertainment and
advertisements at special events and theme parks.
Generally, the beams from these events appear as bright
blue-green in color; however, they may be red, yellow,
or white. However, some laser systems produce light
which is invisible to the human eye.
Currently, there are no FAA regulations
that specifically address the above-mentioned laser
activities. However, FAA regulations prohibit the
disruption of aviation activity by any person on the
ground or in the air. The FAA and the Food and Drug
Administration (the Federal agency that has the
responsibility to enforce compliance with Federal
requirements for laser systems and laser light show
products) are working together to ensure that operators
of these devices do not pose a hazard to aircraft
Pilots should be aware that illumination
from these laser operations are able to create temporary
vision impairment miles from the actual location. In
addition, these operations can produce permanent eye
damage. Pilots should make themselves aware of where
these activities are being conducted and avoid these
areas if possible.
When these activities become known to the
FAA, Notices to Airmen (NOTAM's) are issued to inform
the aviation community of the events. Pilots should
consult NOTAM's or the Special Notices section of the
Airport/Facility Directory for information regarding