(491Q-13-P] DEPARTMENT OF TRANSPORTATION

RlN 2120-AA64 Federal Aviation Administration

SUMMARY: We propose to adopt anew airworthiness directive (AD) for the product 

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ACTION: Notice ofproposed rulemaking (NPRM). (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), DOT. 100 & 440) Airplanes; Model CL-600-2CIO (Regional Jet Series 700, 701, & 702) Ainvorthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series Airplanes; Model CL-600-2D15 (Regiooal Jet Series 705) and Model CL-600-2D24 [Docket No. FAA-2010-*****; Directorate Identifier 201O-NM-014-AD) 14 CFR Part 39

listed above. This proposed AD results frommandatory continuing airworthiness 

### .~ information (MeAl) originated byan aviation authority ofanother country to identify OATE and correct anunsafe condition on an aviation product. The MeAl describes the unsafe ROUTlN'HYMIIQl condition as: Following five reported cases ofbalance washer screw failure on similar ADOs [aiHiriven generators]/ram airturbines installed on other aircraft types, investigation by Hamilton Sundstrand determined that a specific batch ofthe screws had ametallographic non~confonnity that increased their susceptibility tobrittle fracture. 

## *** Failure of abalance washer screw can result in loss ofthe related balance washer, with consequent turbine imbalance. Such imbalance could potentially result in ADG structural failure (including blade failure), loss ofADG electrical power and structural damage to the aircraft and, if deployment was activated by adual engine shutdown, could also result in loss ofbydraulic power for the flight controls [and consequent reduced .n



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mDEPARTMENT OF TRANSPORT AnON Fl'dend Aviatiun Administration 14 CFn. Part 39 

### 14910-13-P] lU"'<VItIIE"oO.,- lOOL'lISt.S">IlOI. ANE-171 ".,,,.,.s,'SI(: C. Alf:m

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AA-2010-*"'***; Directorate Identifier 20tO-NM-OI4·ADl RIN 21211-AA64 Airworthiness Directives; Bombardier, Inc. Model CL-600-2B 19(Regional Jet Series 

## A'N'I~~~"7't, 100 &440) Airplanes; Model CL-600-2CIO (Regional Jet Series 700, 701, & 702) Airplanes; Mode! CL-600-2DI5 (Regional Jet Series 705) and Model CL~600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration WAA). DOT. ACTION: Notice ufproposed mlemaking (NPRM). SUMMARY: We propose (0adopt anew airworthiness directive (AD) for theproducts listed above. This proposed AD resu.lLs from mandatory continuing air\\lorthiness information (MeAl) originated byan aviation authority of another country to identify and correct an unsafe condition all an aviation product The MeAl de!>cribesthe unsafe conditioll m;: Following five reported cases of balance washer screw failure on similar ADGs lair-driven generalors)/ram air turbines inslalled on other aircraft types. investigation byHamilton Sundstrand determined that a spcciHc_ balch

## orthe screws had aIllctallographic non-confonnily that increased their susce.plibility to brittle 1i'"',JclUre. 

### * * * Failure ora balance washer screw can result in loss ofthe related balance washer, with consequent turbine imbalance. Such imbalance could potentially result in ADG structural failure (including blade failure), loss ofADG electrical power and structural damage to the aircraft and, if deployment was activated by a dual engine shutdown, could also result in loss of hydraulic power forthe flight controls. .""''''''!»'",,"•• ANE-171 

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