ATA 56 Windows
1 - Eyebrow windows replacement not always neccessary. 737-ALL
2 - Eyebrow windows removal info. 737-ALL
3 - Cabin windows installation errors. 737-ALL UPDATED
4 - Dispatch with damaged windows #1, #2 and #3. 737-ALL
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1 -
Eyebrow windows
replacement not always neccessary.
737-ALL
It has been determined that a lot of eyebrow windows
have to be replaced nowadays. Replacement is necessary due to damage such as
delamination. Replacements of these eyebrow windows are expensive.
In the early 1950’s, when the aircraft manufacturer was developing their first commercial jet aircraft model 707, visual reference for the pilots was an important issue. Radra and ATC capabilities were still in early stages of development and also not very reliable. In order to maintain a sufficient and unobstructed view during turns and to allow usage of basic navigation equipment the aircraft manufacturer equipped their 707 with so called eyebrow windows. Over the years however, better radar systems, improved ATC procedures and new inboard pilot assisting systems, have made that the eyebrow windows were less and less used.
Starting with the 747, developed in the mid 1960’s, the aircraft manufacturer no longer designed eyebrow windows in the aircraft. There is one exception though, the 737, first designed mid 1960’s, shares the cockpit section structure with the 707 and therefore also has eyebrow windows. In order to save money on design costs, the aircraft manufacturer never removed the eyebrow windows from the 737 design.
Nowadays the aviation authorities and the airline flight crews confirm that the eyebrow windows are not used during flight and therefore no longer make a significant contribution to flight safety.
Suggestion for maintenance technicians:
Only replace an eyebrow window when the damage to the eyebrow window significantly affects the structural intergrity of the airplane or when the damage is out of amm limits.
Eyebrow windows which do not meet amm limits regarding delamination and subsequent visibility do not need replacement for that reason.
The amm states that delamination limits can be extended if the visual capacity is satisfactory. Visual capacity is no longer necessary, referring the history mentioned earlier in this story.
2 - Eyebrow windows
removal info. 737-ALL
Eyebrow windows can be removed and be replaced by plugs with SB 737-56-1017 for the Next Generation, the classic 737's have SB 737-56-1019 for this job. See pictures.
Removed and reinstalled plug.
Kit with the plugs.
3- Cabin windows installation errors.
737-ALL
Very often the 737 NG cabin windows
have moisture / condens in between the outer and middle window panes.
The aircraft manufacturer described this problem in FTD 737NG-FTD-56-02003. They
incorporated improved passenger window assemblies into production airplanes
beginning with line position 2000.
However, poor workmanship may also cause some problems, as we found some windows
installed with the seal completely bend out of position at the lower side. See
the pictures for more details. Also due to this installation errors, the outer
and middle pane are touching each other, which gives a strange view as pictured
below. It looks like some moisture or fungus, but its pure contact debris from
both panes.
Cabin window installation errors are very common and amm procedures must always
be followed very strict. 737NG ref amm 56-21-00.
Thanks to Patrick G. for his input.
You see that a deformed seal can have a very negative effect on the window assembly, it may even result in seperation or leakage of the window when all this moisture turns into ice during flight.
4 -
Dispatch with damaged
windows #1, #2 and #3.
737-ALL
Since AMM rev. Sep. 2010 for 737CL and 15.Oct. 2010 for NG it
is possible to dispatch the 737 with damaged outer pane on 1 and 2 and heated
glass Number 3 windows.
See added Note in the AMM inspection task of #1, 2 and 3.
More Details in the 737-FTD-56-09001 and 737NG-FTD-56-09001. Thanks to
IFixPlanes for his input.