The Greatest Thing That You Have (Probably) Never Read: AC 00-6A (Cancelled)

Published: Tue 01 March 2022
Updated: Tue 01 October 2024

tags: diversions

"Aircraft icing is one of the major weather hazards to aviation. Icing is a cumulative hazard. It reduces aircraft efficiency by increasing weight, reducing lift, decreasing thrust, and increasing drag." 1

Summary

Prior information from the FAA on "Aviation Weather For Pilots and Flight Operations Personnel".

Discussion

Veteran pilots with FIKI ratings (Flight In Known Icing) may already be familiar with this, but the rest of us could benefit from reading it.

Alas, this was cancelled in 2016 (the next version calcelled in 2022 2, and the superseding version 3 is more current, but not as entertaining a read). It also features "instructive illustrations" to introduce each chapter, which are somewhere on the corney-questionable-objectionable spectrum.

The potential hazards of structural icing are noted: Drawing of an airplane with text: Effects of Icing are Cumulative, Lift Lessens, Drag Increases, Thrust Falls Off, Weight Increases, Stalling Speed Increases, Figure 89. Effects of Structural Icing

I am not so sure about the "Stalling Speed Increases" part. The speed at which the airplane may stall at may decrease due to the effects of ice (potentially lower lift at a given airspeed and angle of attack), and a higher airspeed may be required in icing to avoid stall is the way that I would explain it.

The potential hazards of pitot probe (important for airspeed indication) icing are noted (so THAT is what the inside of a pitot looks like): Schematic drawing of the internal passages of a pitot tube with ice obtructing, with text: FIGURE 96.
 Internal pitot tube icing. It renders airspeed indicator unreliable.

Text: In Closing. Icing is where you find it. 
As with turbulence, icing may be local in extent and transient in character. 
Forecasters can identify regions in which icing is possible. 
However, they cannot define the precise small pockets in which it occurs. 
You should plan your flight to avoid those areas where icing
probably will be heavier than your aircraft can
handle. And you must be prepared to avoid or to
escape the hazard when encountered en route.

Closing text reproduced to be searchable:

In Closing

Icing is where you find it. As with turbulence, icing may be local in extent and transient in character. Forecasters can identify regions in which icing is possible. However, they cannot define the precise small pockets in which it occurs. You should plan your flight to avoid those areas where icing probably will be heavier than your aircraft can handle. And you must be prepared to avoid or to escape the hazard when encountered en route.


  1. Anon.: Aviation Weather For Pilots and Flight Operations Personnel. AC 00-6A (Cancelled), FAA, issued April, 1975, cancelled 2016. faa.gov 

  2. Anon.: Aviation Weather. AC 00-6B, FAA, 2016. Cancelled 2022. faa.gov 

  3. Aviation Weather Handbook, FAA-H-8083-28 faa.gov 

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