### 14 CFR ParI 39

DEPARTMENT OF TRANSPORTATION Federal AviatioD 

### Administration



# 05l.J~ [Docket No. FAA-2010-*****; Directorate Identifier 201O-NM-041-AD] 14910-I3-P]

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### R1N 2120-AA64 Airworthiness Directives; Bombardier, Inc. Model BD-700-1AIO and BD-700-lAII Airplanes AGENCY: Federal Aviation Admimstration (FAA), DOT. ACTION: Notice ofproposed rulemaking (NPRM).
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### SUMMARY: We propose to adopt anew airworthiness directive (AD) for the product listed above. This proposed AD results from mandatory continuing airworthiness information (MeAl) originated byan aviation authority ofanother country to identify RCl<.!J"TNG :;;VMBOL 

### and correct anunsafe condition on an aviation product. The MeAl describes the unsafe "mAl..SlSl~ 

### condition as: Following fivereported cases ofbalance washer screw failure on similar RATs [ram air turbines]/air driven generators installed on other aircraft types, an investigation 

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## * determined that aspecific batch ofthe screws had ametallographic non-conformity that increased their susceptibility to brittle fracture. 

## *** Failure ofabalance washer screw can result in loss ofthe related balance washer, with consequent turbine imbalance. Such imbalance could potentially result inRAT structural failure (including blade failure), loss ofRAT electrical power and structural damage to the aircraft and, if deployment was activated by adual engine shutdown, could also result in loss ofhydraulic power for the flight controls [and consequent reduced ability ofthe flightcrew to maintain the safe flight and landing ofthe airplane]. ROlJTTNG SYMBOL
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## *DEPARTMENT OF TRANSPORTATION Federal A,"ialioll AdminiSlr:Hion
14 CIi'J{ 1):\I·t 39 1491O-13-PI

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",;1)11'"<; s,'>"~,,- LGB-i\EG [Docket No. FAA-2010-*****; Dircdllralc Identifier 20IOvNM-041-AI>]

Aim"OI·thillc.~~ Directives; Bombardier, Inc. Model BD~700-1A 10 [Jnd 13D-700-11\11 Airplanes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice ofproposed wlemaking. (NPRM). SUMMARY: Wepropose to adopt anew airworthiness directive (AU) fortheproducts lisled above. This proposed AD results from Itmndalory continuing airworthiness information (MeAl) originated byan aviation authority of another counlry to identify ami correct an unsafe condition on ,maviation product. The MeAl describes the uns~d'c condition as: Following live repOlted cases ofbalance washer screw failure llil simililr RATs lram air lurbincsJ/air driven generators installtld on olher uin.:.rilft types, I1ninvcsrigalioll '" '" '"determined that a specific batch o('l.he screw:; had [l. lIlctallographic non~c{)nforl11ity lhat increased their susceptibility to brittle fracture, 

### * * * Failure of {1 b~lance washer screw can rcsult in loss ofthc related balance washer, with consequcnt turbine imbalance. Such imbalance could potenlially result in RAT structural failure (including blade failure). loss of RAT electrical power and structural damage to the ain:.raftl.lnu, if deployment was activated by adunl enginc shutdown, could also rcsult in loss ofhydraulic power for the nighl controls [and conscquel1\ reduced ability of lhe flightcrew to mailltain lhe sale nighl and landing oCthe airpluncl· '~11,"-"''';

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