STBYRUD
4th Nov 2011, 09:48
Hey chaps, since that time of the year is fast approaching I have a question regarding fan ice on the 737 (possibly that would apply to other types, too).
Last year I had an argument with the deicing handler who initially refused to deice the fuselage, wings and tail unless we would first perform fan blade deicing. Taxiing in with TAI we collected some ice on the fan blades - during the walkaround I made sure the fan was free to rotate, the cowl was free of ice. The ops frequency at this point was already overloaded, every flight was requesting fan blade deicing (and everyone sounded similarly surprised) - the waiting time estimate went up to three hours until a heater unit would be available. To cut a long story short we finally deiced, pushed back, performed an ice shedding run up and finally flew home. My outfit does not have any regulation covering fan ice in addition to the OM and I could not find anything else which would indicate that a clean fan is mandatory for startup. Obviously leaving the airplane out overnight in freezing rain or similar conditions would necessitate hot air deicing of the engines, especially if the cowl and spinner are affected, too - but what would be your call in this situation? LEOS and other service providers happily state in their promotional documents that "it is prohibited to start the engine when fan blade icing occurs" - is there any truth to this? On that day at least it seemed like someone wanted to cash in on the conditions and suggested putting the pilots under pressure...
Cheers!
Edit: Even found a picture taken that day:
http://img189.imageshack.us/img189/6996/fanblade.jpg (http://imageshack.us/photo/my-images/189/fanblade.jpg/)
Uploaded with ImageShack.us (http://imageshack.us)
FCOM: (Cold Weather Operations - External Inspection)
Engine inlets ............................................................ ...................... Check
Verify that the inlet cowling is free of snow and ice.
Verify that the fan is free to rotate.and
SP.16.3 - Deleted the requirement to verify that the fan blades are free of snow
and ice. The is a maintenance function and is accomplished on the first flight
of the day. The flight crew should still verify that the fan is free to rotate. Any
accumulation of ice and snow on the spinner and fan blades should be
removed using the ice shedding procedure during taxi-out and prior to setting
takeoff thrust.EASA SIN 2008-29
GUIDANCE MATERIAL
1. Intake and Fanblade Icing
a. During extended ground operations/taxiing prior to flight in conditions of moderate to
heavy freezing precipitation, it is possible for snow and slush to accumulate within the
engine intake ducting and/or on the rear surfaces of engine compressor/ fan blades.
Such accumulation(s) may not be visible to the crew, nor prevented by the use of
engine anti-icing, especially when engines are operated at or close to ground idle rpm.
Intake duct deposits and engine blade deposits may detach and be ingested by the
engine(s) during the subsequent application of high power settings for takeoff, with
consequential adverse effects on engine operation, and possible flameout.
Ice accumulation on the surfaces of engine compressor/fan blades may severely affect
the aerodynamic characteristics of the blade(s) and cause compressor stall, leading to
surging and engine malfunctioning and/or reduced thrust.
Several accidents have already occurred due to these phenomena.
Paragraph 2 gives detailed information on general de- / anti-icing precautions for
aeroplane operations on the ground.
b. Intake icing. This is, in part, caused by the design of engine intake / ducting on certain
aircraft, whereby accumulations of snow and/or slush can occur in the engine air
intake(s) during low power engine operations, such as taxiing after landing and also
prior to takeoff, in certain meteorological conditions. Relatively long/curved intake
ducts/tracts are particularly prone to this phenomenon.
This phenomenon is most likely in occur to susceptible aircraft during precipitation of
heavy snow or rain at temperatures close to 0°c before and after engine start. In such
cases, the use of engine anti ice system may be ineffective in preventing accumulations
forming in engine intakes.
It is also likely that such deposits may not be visible or apparent to pilots and ground
staff, particularly so in the case of high-mounted engines. Also, in some cases,
accumulation will not take place until after engine start. This situation may be masked
by the fact that the de/anti-icing treatment of the rest of the airframe is still effective,
with frozen deposits not yet forming on the treated areas.
The consequences of unrecognised intake icing will only become evident during high
power engine running (i.e. during takeoff), when it can be too late to take precautionary
actions.
c. Ice accumulation on the rear face of engine compressor / fan blades. This phenomenon
is most likely to occur in susceptible engines during precipitation of heavy snow or rain
precipitation at temperatures close to 0°c before and after engine start. In such cases,
the use of engine anti-ice system may be ineffective in preventing accumulations
forming on the rear faces of blades.
4 of 12
It is also likely that such deposits may not be visible or apparent to pilots and ground
staff, particularly so in the case of high-mounted engines. Also, in some cases,
accumulation will not take place until after engine start (rotating parts striking supercooled
droplets).
Note: Compressor/fan blade icing may have occurred during the previous approach/taxi
in. In this case, such accumulations may be detected during a subsequent pre-flight
inspection (PFI). The potential for re-occurrence during any subsequent operation of
engine(s) must be recognised and precautionary measures taken.
Alternatively, accumulations may occur after engine-start on previously inspected and
“clean” blades. Such occurrences will therefore not be detected during PFI, nor during
normal idle/low power running of engines during ground manoeuvring.
In such cases, it is vital that the potential for blade icing is fully understood by
responsible staff and appropriate countermeasures are employed, as recommended by
the aircraft manufacturer.
The consequences of unrecognised blade icing will only become evident during high
power engine running (i.e. during takeoff), when it can be too late to take precautionary
actions.
d. Recommendation. In the first instance, manufacturers’ recommendations, where given,
should be followed.
In cases where guidance is not provided, operators should liaise with manufacturers
and other qualified entities to obtain advice in order to develop suitable procedures.
It is recommended that operators take appropriate action to recognise and address
these phenomena in their Operations Manuals and to give suitable advice, guidance
and training to pilots and ground staff. Good coordination between Operations and
Maintenance is essential, in particular with regard to maintenance inspections (in
conjunction with the maintenance programme and manufacturer’s recommendations).
Although these phenomena are known to affect certain turbine powered aircraft, it
should be borne in mind that certain piston-engine powered aircraft could be susceptible
to these phenomena, too.
Last year I had an argument with the deicing handler who initially refused to deice the fuselage, wings and tail unless we would first perform fan blade deicing. Taxiing in with TAI we collected some ice on the fan blades - during the walkaround I made sure the fan was free to rotate, the cowl was free of ice. The ops frequency at this point was already overloaded, every flight was requesting fan blade deicing (and everyone sounded similarly surprised) - the waiting time estimate went up to three hours until a heater unit would be available. To cut a long story short we finally deiced, pushed back, performed an ice shedding run up and finally flew home. My outfit does not have any regulation covering fan ice in addition to the OM and I could not find anything else which would indicate that a clean fan is mandatory for startup. Obviously leaving the airplane out overnight in freezing rain or similar conditions would necessitate hot air deicing of the engines, especially if the cowl and spinner are affected, too - but what would be your call in this situation? LEOS and other service providers happily state in their promotional documents that "it is prohibited to start the engine when fan blade icing occurs" - is there any truth to this? On that day at least it seemed like someone wanted to cash in on the conditions and suggested putting the pilots under pressure...
Cheers!
Edit: Even found a picture taken that day:
http://img189.imageshack.us/img189/6996/fanblade.jpg (http://imageshack.us/photo/my-images/189/fanblade.jpg/)
Uploaded with ImageShack.us (http://imageshack.us)
FCOM: (Cold Weather Operations - External Inspection)
Engine inlets ............................................................ ...................... Check
Verify that the inlet cowling is free of snow and ice.
Verify that the fan is free to rotate.and
SP.16.3 - Deleted the requirement to verify that the fan blades are free of snow
and ice. The is a maintenance function and is accomplished on the first flight
of the day. The flight crew should still verify that the fan is free to rotate. Any
accumulation of ice and snow on the spinner and fan blades should be
removed using the ice shedding procedure during taxi-out and prior to setting
takeoff thrust.EASA SIN 2008-29
GUIDANCE MATERIAL
1. Intake and Fanblade Icing
a. During extended ground operations/taxiing prior to flight in conditions of moderate to
heavy freezing precipitation, it is possible for snow and slush to accumulate within the
engine intake ducting and/or on the rear surfaces of engine compressor/ fan blades.
Such accumulation(s) may not be visible to the crew, nor prevented by the use of
engine anti-icing, especially when engines are operated at or close to ground idle rpm.
Intake duct deposits and engine blade deposits may detach and be ingested by the
engine(s) during the subsequent application of high power settings for takeoff, with
consequential adverse effects on engine operation, and possible flameout.
Ice accumulation on the surfaces of engine compressor/fan blades may severely affect
the aerodynamic characteristics of the blade(s) and cause compressor stall, leading to
surging and engine malfunctioning and/or reduced thrust.
Several accidents have already occurred due to these phenomena.
Paragraph 2 gives detailed information on general de- / anti-icing precautions for
aeroplane operations on the ground.
b. Intake icing. This is, in part, caused by the design of engine intake / ducting on certain
aircraft, whereby accumulations of snow and/or slush can occur in the engine air
intake(s) during low power engine operations, such as taxiing after landing and also
prior to takeoff, in certain meteorological conditions. Relatively long/curved intake
ducts/tracts are particularly prone to this phenomenon.
This phenomenon is most likely in occur to susceptible aircraft during precipitation of
heavy snow or rain at temperatures close to 0°c before and after engine start. In such
cases, the use of engine anti ice system may be ineffective in preventing accumulations
forming in engine intakes.
It is also likely that such deposits may not be visible or apparent to pilots and ground
staff, particularly so in the case of high-mounted engines. Also, in some cases,
accumulation will not take place until after engine start. This situation may be masked
by the fact that the de/anti-icing treatment of the rest of the airframe is still effective,
with frozen deposits not yet forming on the treated areas.
The consequences of unrecognised intake icing will only become evident during high
power engine running (i.e. during takeoff), when it can be too late to take precautionary
actions.
c. Ice accumulation on the rear face of engine compressor / fan blades. This phenomenon
is most likely to occur in susceptible engines during precipitation of heavy snow or rain
precipitation at temperatures close to 0°c before and after engine start. In such cases,
the use of engine anti-ice system may be ineffective in preventing accumulations
forming on the rear faces of blades.
4 of 12
It is also likely that such deposits may not be visible or apparent to pilots and ground
staff, particularly so in the case of high-mounted engines. Also, in some cases,
accumulation will not take place until after engine start (rotating parts striking supercooled
droplets).
Note: Compressor/fan blade icing may have occurred during the previous approach/taxi
in. In this case, such accumulations may be detected during a subsequent pre-flight
inspection (PFI). The potential for re-occurrence during any subsequent operation of
engine(s) must be recognised and precautionary measures taken.
Alternatively, accumulations may occur after engine-start on previously inspected and
“clean” blades. Such occurrences will therefore not be detected during PFI, nor during
normal idle/low power running of engines during ground manoeuvring.
In such cases, it is vital that the potential for blade icing is fully understood by
responsible staff and appropriate countermeasures are employed, as recommended by
the aircraft manufacturer.
The consequences of unrecognised blade icing will only become evident during high
power engine running (i.e. during takeoff), when it can be too late to take precautionary
actions.
d. Recommendation. In the first instance, manufacturers’ recommendations, where given,
should be followed.
In cases where guidance is not provided, operators should liaise with manufacturers
and other qualified entities to obtain advice in order to develop suitable procedures.
It is recommended that operators take appropriate action to recognise and address
these phenomena in their Operations Manuals and to give suitable advice, guidance
and training to pilots and ground staff. Good coordination between Operations and
Maintenance is essential, in particular with regard to maintenance inspections (in
conjunction with the maintenance programme and manufacturer’s recommendations).
Although these phenomena are known to affect certain turbine powered aircraft, it
should be borne in mind that certain piston-engine powered aircraft could be susceptible
to these phenomena, too.