500
B. Arizmendi et al.
can find an additional a procedure to extrapolate the icing envelopes to any cloud
length.
• Intermittent maximum icing: Icing envelopes that characterize severe short
encounters occurring when the aircraft flies through cumulus clouds. Cumulus
clouds extend vertically and commonly contain high liquid water content. Large
amounts of ice accreted on the surface of the aircraft are expected. The values
of the atmospheric parameters can be found in the regulations code which are
analogous to Figs. 15.20 and 15.21.
In addition, Appendix C presents aircraft operation stages that must be studied
from the icing effects point of view. To reduce the number of tests required while
ensuring the protection under all the envelopes, it is accepted the study of the most
critical conditions. The Appendix O includes SLD icing envelopes for droplets
larger than 40 μm in a similar manner as it was presented in Figs. 15.20 and 15.21.
The icing envelopes include freezing drizzle and freezing rain conditions, which are
found when an aircraft is flying through or below a stratiform cloud. The fulfilment
of the protection against SLD is critical since the SLD accretions have been claimed
the cause of aircraft crashes.
To attain certification to fly in icing conditins, an aircraft must be able to “safely
operate” in both maximum continuous and intermittent conditions and in freezing
rain and drizzle. The full description of the conditions is described in Sections
25.1419 and 25.1420. The “safe operation” should be ensured in all the phases of
flight, including take off, holding, descent, landing and go-around. This must be
assessed by in-flight or laboratory test of aircraft, parts or models exposed to the
critical ice envelopes presented in the Appendices C and O. In these tests, the ice
protection systems must be operated according to the operations flight manual and
ice detections systems or procedures must be available. Additionally, in the case of
SLD ice encounters, the aircraft must be able to safely exit them.
Snow and mixed icing conditions are included in a set of envelopes presented in
the appendix D to Part 33. Those are defined by the altitude of the encounter, the
total water content (TWC) in g/m 3 , and the ice crystal size median mass dimension
(MMD). Section 25.1093 states that the aircraft must be able to operate in all the
envelopes presented in Appendixes C, D, and O and in the presence of falling or
blowing snow. In addition, the aircraft design must ensure the avoidance of ice
accumulations that lead to faulty engine operation, loss of power or stall.
15.4.3.2 EASA Certification Specifications
The European Aviation Safety Agency (EASA) is accountant for all the European
civilian aviation safety. Among their missions is the aircraft certification for all
the state members and collaboration with other international agencies to promote
worldwide standards and achieve the highest safety level. The corresponding
certification department developed a set of regulations to ensure aircraft reliability
and safety when encountering icing conditions, which is described in section 25.
B. Arizmendi et al.
can find an additional a procedure to extrapolate the icing envelopes to any cloud
length.
• Intermittent maximum icing: Icing envelopes that characterize severe short
encounters occurring when the aircraft flies through cumulus clouds. Cumulus
clouds extend vertically and commonly contain high liquid water content. Large
amounts of ice accreted on the surface of the aircraft are expected. The values
of the atmospheric parameters can be found in the regulations code which are
analogous to Figs. 15.20 and 15.21.
In addition, Appendix C presents aircraft operation stages that must be studied
from the icing effects point of view. To reduce the number of tests required while
ensuring the protection under all the envelopes, it is accepted the study of the most
critical conditions. The Appendix O includes SLD icing envelopes for droplets
larger than 40 μm in a similar manner as it was presented in Figs. 15.20 and 15.21.
The icing envelopes include freezing drizzle and freezing rain conditions, which are
found when an aircraft is flying through or below a stratiform cloud. The fulfilment
of the protection against SLD is critical since the SLD accretions have been claimed
the cause of aircraft crashes.
To attain certification to fly in icing conditins, an aircraft must be able to “safely
operate” in both maximum continuous and intermittent conditions and in freezing
rain and drizzle. The full description of the conditions is described in Sections
25.1419 and 25.1420. The “safe operation” should be ensured in all the phases of
flight, including take off, holding, descent, landing and go-around. This must be
assessed by in-flight or laboratory test of aircraft, parts or models exposed to the
critical ice envelopes presented in the Appendices C and O. In these tests, the ice
protection systems must be operated according to the operations flight manual and
ice detections systems or procedures must be available. Additionally, in the case of
SLD ice encounters, the aircraft must be able to safely exit them.
Snow and mixed icing conditions are included in a set of envelopes presented in
the appendix D to Part 33. Those are defined by the altitude of the encounter, the
total water content (TWC) in g/m 3 , and the ice crystal size median mass dimension
(MMD). Section 25.1093 states that the aircraft must be able to operate in all the
envelopes presented in Appendixes C, D, and O and in the presence of falling or
blowing snow. In addition, the aircraft design must ensure the avoidance of ice
accumulations that lead to faulty engine operation, loss of power or stall.
15.4.3.2 EASA Certification Specifications
The European Aviation Safety Agency (EASA) is accountant for all the European
civilian aviation safety. Among their missions is the aircraft certification for all
the state members and collaboration with other international agencies to promote
worldwide standards and achieve the highest safety level. The corresponding
certification department developed a set of regulations to ensure aircraft reliability
and safety when encountering icing conditions, which is described in section 25.