SUBJECT:QUETIONS FOR THE CDL 57-54-03 TO CDL 57-54-10
INQUIRYTYPE: Other
REFERENCES:
/A/GUN-GUN-20-0076-01C
/B/Fire Resistance Zone
DESCRIPTION:
GUNfound the seals around the Krueger flaps of most airplanes damagedrecently. According to the CDL 57-54-03 to CDL 57-54-10, Onlythe seals and/or seal retainers around the inboard Krueger flapcavities (Krueger flaps #2 and #3) are allowed to be missing. Sealsthat extend partially over the outboard Krueger flap cavities may notbe missing. Any seal retainers that support the seals which extendpartially over the outboard Krueger flap cavity may not be missing,even if these seal retainers are located entirely in the inboardKrueger flap cavities.
DESIREDACTION:
Q1.Whyseals that are around or extend partially over the outboard Kruegerflap cavities can not be missing?
Q2.Ifthe seals around or extend partially over the outboard Krueger flapcavities are damaged but not missing, could the airplane continue toservice?
Q3.Ifthe seal bulb ( L/H P/N:114A1802-1 ) between inboard and outboardKrueger or the rub strip ( L/H P/N :114A1804-5) are missing, couldthe airplane continue to service?
RESPONSE:
Inresponse to the Ref /A/ message, Boeing provides the following:
1.Because they are near the engine and found to be in the fireresistance zone (see Ref /B/ for definition of the fire resistancezone). This is an aircraft type certification requirement 14 CFR25.867(a). In addition to providing aerodynamic seals for improvedperformance, these seals are also required to provide protection inthe event of an engine fire.
2.Usually, severely damaged seals must be replaced/installed to returnthe aircraft to service if it is deemed that the seal can not performit's fire retention function. However, in some instances theaircraft can be returned to service if the damage is minor. These instances will have to be reviewed on a case-by-case bases.
3.Seal bulb (L/H P/N: 114A1802-1) between inboard and outboard Kruegerand the rub strip (L/H P/N: 114A1804-5) must be replaced and/orinstalled to return the aircraft to service.