Thunderstorms — Page 266, Lesson 241

I want to walk you through a section on thunderstorms, but this part of the book is actually about the instruments and equipment you use to handle them, not the storm itself. Let's start with a specific limitation of some older flight instruments. We're looking at paragraph 2.9.3.3, which deals with pitch referencing on attitude indicators. On some flight director presentations, the attitude indicator lacks a proper pitch reference. More importantly, the range of indication on these instruments is much less than the standard 85 degrees up and 85 degrees down. In some cases, the range is less than 30 degrees total. The critical problem is that on these earlier instruments, when the aircraft's pitch attitude exceeds that limit — say you're in a steep climb or dive — the instrument gives the pilot no indication that it has run out of range. It simply stops showing useful information. That means it gives you no guidance on how to recover from an attitude that is outside its normal range of indication. You're effectively blind to your pitch situation once you exceed that limit. Paragraph 2.9.3.4 drives home the practical point: because there is such a wide variety of instruments you might encounter across different aircraft, it is essential that pilots are fully aware of the limitations of the particular attitude indicator fitted in the aircraft they fly. You cannot assume every attitude indicator behaves the same way. Now we move to section 2.9.4, which covers magnetic compasses. The key fact here is that magnetic compasses are likely to be seriously affected by a lightning strike. If your aircraft is struck by lightning, you should not rely on the magnetic compass afterward. It must be checked as soon as possible to verify it is still serviceable. Next, section 2.10 introduces the use of weather radar. Paragraph 2.10.1 makes a very clear statement about its primary function: airborne weather radar is provided principally to enable pilots to AVOID thunderstorms. That is its main job. It can also be of assistance in penetrating areas of storm activity when avoidance has not been possible — but that is a secondary, fallback use. There is an important caution here: pilots should be aware that the displayed data can be unreliable when used for calculating safe vertical clearance for overflying active storm cells. In other words, do not trust the radar picture to tell you exactly how high you need to be to clear a storm safely from above. Finally, paragraph 2.10.2 says pilots should be familiar with the characteristics, operation, and limitations of the radar in their specific aircraft. Operators — that means the airline or company — must ensure their crews are given adequate instructions on the radar equipment fitted to their aircraft. This includes the operation of the antenna, the radar controls, and the adjustment of those controls for proper use.