Fan Blade Icing / Deicing on the 737

[Vaneev]

CFM Flight Operations Newsletter №3 Fall 2010

One of the most frequently asked questions from flight crews
is, “How much ice accumulation on the spinner and fan blades
is acceptable before deicing is required prior to dispatch?”
Unfortunately, due to various environmental conditions,
airport operations, airline policies and procedures, etc., there
is no single recommendation that encompasses all situations.
Typically, operators task the ground maintenance crews with
engine deicing as required. During preflight, the flight crew
verifies that the engine cowl and inlet are free of contaminants
and that the fan rotates freely.
 Figures 1, 2, and 3 show various spinner/fan blade ice
conditions that can be encountered during operations in
icing conditions.
 Figures 1 and 2 show that ice has accumulated only on the
spinner cone and that no ice is visible on the fan blades,
booster splitter or booster inlet guide vanes. In these
situations, even if a thin layer of ice/snow were present on
the fan blades, performing the ground ice shed procedure
per the FCOM (Flight Crew Operating Manual) would be
sufficient.
 Figure 3 shows the spinner completely ice-covered and ice
accumulated on the fan blade leading edge and pressure
surface, with the heaviest concentration at the root and
decreasing towards the fan blade tip. This phenomenon is
due to centrifugal forces preventing ice build-up near the
tip. In this case, as well as situations where ice accumulation
is visible on the booster splitter and inlet guide vanes, it is
advisable to discuss the situation with maintenance prior to
dispatch, particularly if moderate to severe icing conditions
are forecast for taxi and takeoff. If deicing the engine prior
to push back or delaying the flight is not an option, then
perform the FCOM ice shed procedure as soon as possible
during taxi-out.
Important: The information, opinions and recommendations presented in this article are those of the engine manufacturer. The
policies, documents and operating procedures specified by the airplane manufacturers and your airline take precedence.

All Document: http://aviacom.ucoz.ru/CFM_Flight_Op..._Fall_2010.pdf