The concern sheetOCR
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Airworthiness FAA Concern Sheet Date: September 28,2007 HACS for Bleed Air Cable separation Werner Koch Title Aviation Safety Engr OrganizationASW- 150 DepartmentAIR Address Southwest Region Headquarters City State ZIPFort Worth, TX,76193-150 Telephone Number 817-222 5133 E-mailWerner.g.koch@FAA.GOV Make, Model, Series, Serial No.:
SA226 and SA227, all models: M7 Aerospace LP (formerly Fairchild Aircraft Corporation) Reason for Airworthiness Concern:
See the FAA Description of Airworthiness Concern below FAA Description of Airworthiness Concern (Who, What, Where, When, How? Attachments: RA and appropriate data) Due to insufficient clearance between the bleed air line and electrical cables the bleed air line forward of the right wing battery box may be chafing against the four gauge wiring from the battery. If left undetected and uncorrected this chafing could eventually chafe through the asbestos sleeve surrounding the starter wires. The arcing of the exposed wires can burn a hole in the bleed air line and also arc a hole in a nearby hydraulic line. Hydraulic fluid leaking from the damaged line can then be ignited by the arcing or by the hot gases resulting in a fire in the engine nacelle compartment.
Service bulletins (S/B) were prepared and revised in 1984 to address this issue for the SA226 and SA227 aircraft (except the SA227 CC/ DC models). They provided instructions on how to rework and reroute elements to insure a minimum of ½ in. clearance between the bleed air line and the battery cables in the affected area. The rework was not FAA mandated at that time.
In June 2007 SA226TC N160WA, S/N TC399 sustained a fire in the right hand nacelle/wing area. In reviewing the damage prior to making the repair it was determined that the bleed air tube chafed/burned through the asbestos sleeve surrounding the starter wires. The wires then arced a hole in the bleed air tube. Hot bleed air melted the insulation from the starter wires allowing the wires to short and are a hole in a nearby hydraulic line. Hydraulic fluid leaking from the damaged line apparently was ignited by the hot gases or electrical arcing, resulting in a fire in the engine nacelle compartment.
In addition, review of Service Difficulty Reports for the past 30 years identified 4 additional reported incidents of bleed air tube chaffing through the asbestos sleeve surrounding the starter wires. Two of these were on the SA226 series and 2 were on the SA227 series aircraft. No evidence of a fire or other catastrophic failure was noted.
M7 has prepared S/Bs to conduct a periodic visual inspection of all SA226 and SA227 aircraft to assess the proper clearance between the bleed air and the starter cables. In the event that insufficient clearance is evident the S/Bs require modification/rework in accordance with the previous 1984 SBs to obtain the ½ inch clearance. FAA action to mandate the inspections and noted rework if necessary is being recommended.
Note: The S/Bs for rework of the SA227 A/C are Fairchild Aircraft Corp No. SB24-001revised May 17, 1983 and SB24-002 revised February 15, 1984. The S/Bs for rework of the SA226 A/C are S. B. 24-001 revised September 16, 1975, SB24-020 revised February 15, 1984, and SB24-019 Revised May 17, 1983.
Doanget for Information (D Attachments: *SDR(s)| | *A/IDS *SL(s) _ *SAIB *FAASR/*NTSBSR *AD *AMOC_ *RA Notification: FAA X*, AOPA X, *EAA X, Type Club , *TC Holder X, Other:
Response Requested _: Emergency (10 days) Alert (30 days) Information (90 days) (Space Bar Adds "X" to Check Boxes) This Airworthiness Concern Sheet (ACS) is intended as a means for FAA Aviation Safety Engineers to coordinate airworthiness concerns with aircraft owner/operators through associations and type clubs. At this time, the FAA has not made a determination on what type of corrective action (if any) should be taken. The resolution of this airworthiness concern could involve an AD action or an SAIB, or the FAA could determine that no action is needed at this time. The FAA's final determination will depend in part on the information received in response to this ACS.