From: DUPREZ Nicolas [mailto:nicolas.duprez@easa.europa.eu] 
Sent: Wednesday, July 05, 2017 11:49 PM
To: Lu, Lu (FAA)
Subject: New Proposed AD (NPRM) FAA-2017-0473 for Boeing 737-100/-500 aeroplanes

Dear Lu,

I am the EASA Project Certification Manager in charge of the B737 fleet.
I was made aware of the publication of FAA NPRM 2017-0473.

Some experts of my teams have made comments that need clarification.
I would be glad if you could support us in providing the corresponding answers.
"
1.    The flutter is provoked after failure of hinges 4 and/or 6. The SB and AD focuses mainly in detection of wearing on these hinges. However, any other loose hinge would provoke overloading in the adjacent hinges and therefore the failure of hinge 4 or 6 could be provoked by any other loose hinge. It is suggested to extend the inspection and checks to all hinges.
2.    Has it been confirmed that sufficient access exists to adequately inspect and test all areas via the methods defined?
3.    Something is inconsistent in Para (g) of the AD: This refers to the actions for Group 1 aircraft, but the SB states that Group 1 have exceeded their LOV and gives no further advice.
4.    In Para (i) of the AD, why are there no repeat instruction for Group 2, Configuration 1 aircraft? Even if it is acknowledged that at page 38 of the SB (Group 2, Configuration 1), there is a repeat interval every 4500 FC, the Bearing plate replacement is not included.
"

With best regards,

Nicolas Duprez
Project Certification Manager Large Aeroplanes
Certification Directorate
European Aviation Safety Agency


Tel.: +49 221 89990 4359
Postal: Postfach 10 12 53, 50452 Cologne, Germany
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