B737-Cold_Soak_Fuel_Frost

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B737-Cold_Soak_Fuel_Frost

 

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737.1
Cold Soaked Fuel Frost
Terry Sheehan
737NG Procedures Manager
Boeing Commercial Airplanes
May 2004
The Boeing Company 737.2
Background
• Cold Soak Fuel Frost (CSFF) continues to be a
concern for many 737NG operators
– High frequency of occurrence
– High recurring cost to detect and remove CSFF
– High frequency of occurrence at stations that
do not have deicing equipment
– Negative impact on the value of fuel tankering
The Boeing Company 737.3
Background
• System solutions are not viable
– Studies of many concepts in progress for four
years
– No viable business case for any technically
feasible concept
The Boeing Company 737.4
Background
• AFM requires use of all center tank fuel prior to
the use of main tank fuel
• AD 2002-19-52 and AD 2002-24-51 provide relief
from the AFM limitation to eliminate dry running
of center tank fuel pumps
– Unintentional benefit - reduced exposure to
CSFF
• Several operators have devised fuel usage
procedures based on the AD to prevent
exposure to CSFF
– AD procedures will be eliminated with
termination of the AD
The Boeing Company 737.5
Typiicall CSFF Formattiion
The Boeing Company 737.6
Regullattory Requiirementtss
• CSFF removal is an FAA regulatory requirement
(14 CFR 121.629(b))
– “No person may take off an aircraft when frost,
ice, or snow is adhering to the wings, control
surfaces, propellers, engine inlets, or other
critical surfaces of the aircraft…….Takeoffs
with frost under the wing in the area of the fuel
tanks may be authorized by the Administrator”
FAA
The Boeing Company 737.7
Regullattory Requiirementtss
• JAA/EASA also addresses cold soaked fuel frost
in JAR-OPS 1.345, Ice and Other Contaminants
– “A commander shall not commence take-off
unless the external surfaces are clear of any
deposit which might adversely affect the
performance and/or controllability of the
aeroplane except as permitted in the Aeroplane
Flight Manual”
JJAA
The Boeing Company 737.8
Wiing Aerodynamiicss wiitth CSFF
• Wind tunnel tests completed in December 2002
– CSFF was modeled with “grit” applied to
affected wing regions
• Flight demonstration completed in August 2003
with CSFF on upper wing surface
• Results
– For wing fuel load up to 83%, no degradation
in handling qualities (pitch, roll)
– Impact on aerodynamic performance not
significant
– No impact on certified performance
The Boeing Company 737.9
Propossed Operattiionall Proceduress
• Takeoff with light coatings of cold-soaked fuel
frost on upper wing surfaces is permissible,
provided the following are met:
– Frost on the upper surface is less than 1/16
inch (1.5 mm) in thickness
– The extent of the frost is similar on both wings
– The frost is on or between the black lines
defining the permissible cold-soaked fuel frost
area with no ice or frost on the leading edges
or control surfaces
– The outside air temperature is above freezing
– There is no precipitation or visible moisture
The Boeing Company 737.10
CSFF Permiissssiiblle Area
The Boeing Company 737.11
New Suppllementtary Proceduress
The Boeing Company 737.12
Deplloymentt off CSFF
• Boeing will incorporate CSFF permissible area in
production starting with Line Number 1538 in July
2004, as a standard feature
– Lines on wing upper surface
– Manual updates to support operations will
include Airplane Flight Manual, Airplane
Maintenance Manual, and Flight Crew
Operations Manual
• Retrofit will be available per Boeing Service
Bulletin 737-11-1125
The Boeing Company 737.13
Deplloymentt off CSFF
• Boeing will work with each affected operator and
the respective regulatory agency to obtain
regulatory approval and to implement procedures
– FAA customers will require exemption
– Boeing working with FAA Flight Standards
– Boeing will assist operators with their
exemption requests
– FAA working toward a rule change in the
longer term
– JAA/EASA rules do not explicitly require
exemption
– Boeing will work directly with operators