AIM

4/20/23

7

−

6

−

11

Potential Flight Hazards

4.

Motor boat sound on audio.

5.

Loss of all avionics in clouds.

6.

VLF navigation system inoperative most of the time.

7.

Erratic instrument readouts.

8.

Weak transmissions and poor receptivity of radios.

9.

“St. Elmo’s Fire” on windshield.

c.

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.

d.

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.

e.

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

environment.

f.

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.

g.

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 edges.

h.

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.

7

−

6

−

13. Light Amplification by Stimulated Emission of Radiation (Laser) Operations and

Reporting Illumination of Aircraft

a.

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.