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IDnl'1wtNo. 1'1\1\-2010-0375; IJircctorafc Identifier 2010-Nf\:I~nJ4-AJ); Anu'lldmcnt f\NI~-171

IUN 2120-AA64 Ainvorthinl'ss Oi"cctivcs; Bombardier, 1m:.Model CL-600-2B 19(Regional Jet Series J00 & 440) Airplane::;; Model CL-600-2C I0 (Regional .JetSerie5 700, 70I, & 702) Airplanl'-s~ Model CL-600-2D15 (Regional Jet Series 705) and Model CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), Department ofTranspoltatioll (DOT)" ACTrON: Final rule. SUf\:IMi\I{Y: We arc adopting a llCW airworthiness directive (AD) lbr lhe products listed abnve, This AD results from mandatory contillllilt airworthiness inrormation (r'vlCAI)



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### "ct "/" / "" onglllatc )y ,Ill avmttOIl aul"lOnty 0 'anot leI' country to I cnt! y tHl{ eoneet un llnsuh~ condition on an aviation prouu(,;1. The MeAl dcJribes the unsafe (';llndilion as: Following live reported cases ofbalance JaSher screw luilurc on similar ADCh; lair-driven gellcralorsJ!ram air turbines instalkd on othcr ain.:rali types, investigation by I-Iam-ilton Sundstrand ddemlined Ihal a specific baldl of the screws had a lm:iallographic non-conformilY that increased their susc<.:ptibility to brittle fracture. '" .•..•. Failure of LI balance washcr serew can rcsuh in loss of the relaled balance washer, with consequent turbine imbalance. Such imbalance ..:.ould potentially result in ADO slructural failure (including blade lllilurc), loss of ADG ch:ctric<ll power and structural dal1l<lgc to the aircr,,1i ,md. if 

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### [4910-1 DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 IDocket.;No. FAA-2010-0375; Directorate Identifier 2010-NM-014-AD; Amendme 

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### Ainvorthiness Directivesj Bombardier, Inc. Model CL-600-2B19 (Regional Jet Serie 100 &440) Airplanes; Model CL-600-2CIO Cfegional Jet Series 700, 701, &702) Airplanes; Model CL-600-2DI5 (Regional Jet Series 705) and Model CL-600-2D24 (Regional Jet Series 900) Airplanes AGENCY: Federal Aviation Administration (FAA), Department of,Transportation (DOT). ACTION: Final rule. SUMMARY: We are adopting anew airworthiness directive (AD) forthe products lis above. This AD results from mandatory 

### cODtinLng aiIVIorthiness information (MeAD originated byan aviation authority ofanother 

### Luntry toidentify and correct anunsafe condition on an aviation product. The MeAldescribes theunsafe condition as: Following five reported cases ofbalance washer screw failure on similar ADGs [air~driven generators]/ram air~rbines installed on other aircraft types, investigation by Hamilton Sundstrand determined that aspecific batch ofthe screws had ametallographic non-conformity that increased their susceptibility tobrittle fracture. 

## *** Failure ofabalance washer screw can result in loss oftherelated balance washer, with consequent turbine imbalance. Such imbalance could potentially result inADG structural failhre (including blade failure), loss ofADO electrical power and structural :damagetothe aircraft and, if

FAA Form 1360-14.1 (6-89) OFFICIAL FILE COPY