AIM

8/15/19

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59

Meteorology

17.

Do regard as extremely hazardous any

thunderstorm with tops 35,000 feet or higher whether
the top is visually sighted or determined by radar.

18.

Do give a PIREP for the flight conditions.

19.

Do divert and wait out the thunderstorms on

the ground if unable to navigate around an area of
thunderstorms.

20.

Do contact Flight Service for assistance in

avoiding thunderstorms. Flight Service specialists
have NEXRAD mosaic radar imagery and NEXRAD
single site radar with unique features such as base and
composite reflectivity, echo tops, and VAD wind
profiles.

b.

If you cannot avoid penetrating a thunderstorm,

following are some Do’s before entering the storm:

1.

Tighten your safety belt, put on your shoulder

harness

 

(if installed), if and secure all loose objects.

2.

Plan and hold the course to take the aircraft

through the storm in a minimum time.

3.

To avoid the most critical icing, establish a

penetration altitude below the freezing level or above
the level of -15ºC.

4.

Verify that pitot heat is on and turn on

carburetor heat or jet engine anti-ice. Icing can be
rapid at any altitude and cause almost instantaneous
power failure and/or loss of airspeed indication.

5.

Establish power settings for turbulence

penetration airspeed recommended in the aircraft
manual.

6.

Turn up cockpit lights to highest intensity to

lessen temporary blindness from lightning.

7.

If using automatic pilot, disengage Altitude

Hold Mode and Speed Hold Mode. The automatic
altitude and speed controls will increase maneuvers
of the aircraft thus increasing structural stress.

8.

If using airborne radar, tilt the antenna up and

down occasionally. This will permit the detection of
other thunderstorm activity at altitudes other than the
one being flown.

c.

Following are some Do’s and Don’ts during

 

the

thunderstorm penetration:

1.

Do keep your eyes on your instruments.

Looking outside the cockpit can increase danger of
temporary blindness from lightning.

2.

Don’t change power settings; maintain

settings for the recommended turbulence penetration
airspeed.

3.

Do maintain constant attitude. Allow the

altitude and airspeed to fluctuate.

4.

Don’t turn back once you are in the

thunderstorm. A straight course through the storm
most likely will get the aircraft out of the hazards
most quickly. In addition, turning maneuvers increase
stress on the aircraft.