VOLCANIC ASH

Question 1

How can Volcanic Ash be distinguished from normal clouds?

Answer 1

Volcanic Ash is generally brown and hazy in appearance?

Question 2

How far way from a volcano should we plan to be?

Answer 2

120 nm on the upwind side

Question 3

What is a VAA?

Answer 3

A “Volcanic Ash Advisory” issued by the responsible Volcanic Ash Advisory Center

Question 4

What are the 4 alert levels for Volcanic Ash?

Answer 4

1 GREEN: Non eruptive stage
2 YELLOW: Potential activity increased
3 ORANGE: Ash below 25'000 ft
4 RED: Large eruption expected or confirmed. Ash likely 
            above 25'000 ft

Question 5

Is Volcanic Ash visible on a Weather Radar?

Answer 5

No

Question 6

What are some of the indicators of Volcanic Ash?

Answer 6

S:t Elmos Fire
Windshields severely pitted
Bright glow around engine inlets
Smokey or Acrid smells
Haze/dust appearing on the flight deck
Fluctuating engine or airspeed indications
Engine stalls
Increasing EGT

Question 7

What is the procedure when experiencing Volcanic Ash?

Answer 7

• Exit area, most likely a 180 degree turn
• Retard thrust to idle power to lower EGT and improve
  stall margins
• Put Engine- and Wing Anti-ice ON to increase bleed extraction and further improve stall margins
• Do “Volcanic Ash Un-annunciated Checklist”
• File a PIREP
• Submit a VAR (Volcanic Ash Report) upon landing
• Set the re-circulation fans to off

Question 8

What are some of the hazards associated with Volcanic Ash?

Answer 8

• Engine malfunctions. Stall leading to high EGT
• Blockage of Static and Pitot tubes. Unreliable airspeed
  might occur
• Contamination of cabin air. Oxygen use may be
  required
• Erosion of external components
• Windscreens can be damaged. Divert to airport with
  autoland

Question 9

What happens to the ash as it goes through the core of the engine?

Answer 9

Ash particles melt at 1’100 deg C. Engine temp is around 1’400 deg C so ash melts in the hot section and attaches to the HP turbine blades.

Question 10

Why is reducing thrust a good idea in Volcanic Ash situations?

Answer 10

1. Lowers EGT and improves the stall margin
2. Lowers the core temperature to try to avoid the ash
   particles melting