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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


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


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



(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


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


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.