REG NASA-LLIS-3259-2011 Lessons Learned Design for Operability High Use Nut Plate Insert Design.pdf

1、Public Lessons Learned Entry: 3259 Lesson Info: Lesson Number: 3259 Submitting Organization: KSC Submitted by: Annette Pitt Subject: Design for Operability; High Use Nut Plate/ Insert Design Abstract: Line-replaceable units (LRUs) are removed, replaced, or inspected far more often than related parts

2、 on a standard aircraft. The fastener receptacles quickly become worn and are often difficult to access or replace. For reusable spacecraft, nut plates should be designed for frequent use. Nylon-style locking features such as Vespel should be avoided. Description of Driving Event: Due to the rigorou

3、s requirements involved in processing a manned reusable spacecraft, line-replaceable units (LRUs) are removed, replaced, or inspected far more often than related parts on a standard aircraft. The fastener receptacles quickly become worn and are often difficult to access or replace. The two primary f

4、ailures are galling and the wearing out of the secondary locking feature. It has been necessary to use Loctite on most of the window fasteners. In cases where a nut plate simply fails, it has been necessary to bond studs and to use an exterior bolt to secure the fastener. Lesson(s) Learned: For reus

5、able spacecraft, nut plates should be designed for frequent use. If a secondary locking feature is required, the locking feature should be placed on the bolt rather than on the insert or nut plate. Nylon-style locking features such as Vespel should be avoided because, on certain joints, the preload

6、may be unstable during flight loads and thermal cycles. Recommendation(s): For reusable spacecraft, nut plates should be designed for frequent use; and if a secondary locking feature is required, place the locking feature on the bolt rather than on the insert or nut plate. Nylon-style locking featur

7、es such as Vespel should be avoided. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directorate(s): Space Operations Additional Key Phrase(s): Mission Operations and Ground Support Systems. Mission Operations and Ground Support Systems.Ground processing an

8、d manifesting Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Project: Space Shuttle Program Approval Info: Approval Date: 2011-11-30 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-