1、Lessons Learned Entry: 1996Lesson Info:a71 Lesson Number: 1996a71 Lesson Date: 2008-12-9a71 Submitting Organization: JPLa71 Submitted by: David Oberhettingera71 POC Name: Eric Slimko; Ronald T. Welcha71 POC Email: Eric.M.Slimkojpl.nasa.gova71 POC Phone: 818-354-5940 (Slimko); 818-354-7096 (Welch)Sub
2、ject: MSL Heatshield Handling Incident Abstract: In August 2008, the Mars Science Laboratory flight spare heatshield and fixture was dislodged from its tracks and fell 6-7 inches when being moved for a characterization test at a contractor facility. When ground handling flight hardware, even simple
3、operations can fail without adequate procedures and training. Perform a fixture validation move prior to the first time flight hardware is to be moved, involve the designated cognizant engineer, and always use a steering stick or T-bar to guide the casters or wheels.Description of Driving Event: The
4、 Mars Science Laboratory (MSL) flight spare heatshield was mishandled in August 2008 during ground handling following a characterization test at a contractor facility (Reference (1). The mishap occurred while technicians were manually rolling the vacuum-bagged heatshield, mounted on its Nose-Up Fixt
5、ure (NUF), out of the oven on two guided tracks. The tracks form a ramp from the oven entrance to the floor below. One of the two tracks has a guide slot that matches the grooves on the NUFs steel casters. As the heatshield mounted on its fixture rolled out of the oven, the two rear casters jumped t
6、he ramped tracks, resulting in a fall of 6 to 7 inches to the concrete floor (Figure 1). To determine the extent of damage to the heatshield from the fall-induced shock, the contractor performed visual inspection, a coin tap to identify any delaminations in the carbon composite material, and X-rays
7、to assess any deformation of the core. No defects were identified by these inspection techniques, and Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the disposition of this production process anomaly was to use the flight spare heatshield as-is. Fig
8、ure 1 is a color photo of the right half of a saucer-shaped object that is encased in a clear film and is resting on a wheeled frame. Two wheels (steel casters) are visible. The front caster rests on a slotted yellow track that is fastened to a concrete floor. The rear caster is dislodged from the t
9、rack and rests 4 to 6 inches to the left of the track on the concrete floor. The rear of the yellow track appears to terminate against a wall, such that the dislodged rear caster sits 4 to 6 inches in front of the wall. The front caster appears to be immobilized by a C-clamp attached to it.Figure 1.
10、 Arrow points to one of the two rear casters that each sat left of its track after the fall. This ground handling incident was attributed to the following factors: 1. An inadequate work procedure that did not provide moving instructions.2. Grooved track casters that had been rotated 180 degrees from
11、 the planned direction of travel when inserted into the track slot. Casters not set to the direction of linear travel causes a tendency for the casters to swivel during movement, and the momentary lateral direction during this swivel can direct the fixture off the tracks.3. Steering sticks, T-bars,
12、and jacks were not used to constrain and guide the casters on the tracks.Contributing causes were also identified: 1. The NUF is considered a tool, and Functional Failure Mode & Effect Analysis (FFMEA) is not typically performed on tools. 2. The hardware drawing did not list a steering stick and a T
13、-bar as accessories.3. There was no cognizant engineer providing oversight during the operation.4. Appropriate skills training was not up-to-date, and the curriculum to be used in learning plans was not clearly defined.5. The ground handling crew had no experience with the NUF tool, and it was the f
14、irst time it had been placed in the oven.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-References: (1) “Heatshield Structure #1 (Flight Spare) Handling Drop,“ JPL Problem/Failure Report No. 13366, August 27, 2008.Lesson(s) Learned: When ground hand
15、ling flight hardware, even simple operations can fail without adequate procedures and training.Recommendation(s): 1. Perform a tool validation move prior to the first time flight hardware or critical equipment mounted to a ground handling fixture is to be moved. The proper positioning of casters for
16、 the desired direction of linear movement is a special concern.2. Notify the designated cognizant engineer, as well as representatives of QA and System Safety, of all planned moves of flight hardware or critical equipment.3. Even when rails or tracks are used to constrain motion, always attach a ste
17、ering stick or T-bar to the casters or wheels to guide the movement of valuable equipment.Evidence of Recurrence Control Effectiveness: JPL has referenced this lesson learned as additional rationale and guidance supporting Paragraph 6.12.4 (“Engineering Practices: Protection and Security of Flight H
18、ardware“) in the Jet Propulsion Laboratory standard “Flight Project Practices, Rev. 7,“ JPL DocID 58032, September 30, 2008.Documents Related to Lesson: N/AMission Directorate(s): a71 Aeronautics Researcha71 Exploration Systemsa71 ScienceAdditional Key Phrase(s): a71 1.Advanced planning of safety sy
19、stemsa71 1.Product Assurancea71 1.Qualitya71 1.Flight Equipmenta71 1.Ground EquipmentProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 1.Ground Operationsa71 1.Hardwarea71 1.Industrial Operationsa71 1.Payloadsa71 1.Safety & Mission Assurancea71 1.S
20、pacecrafta71 1.Test Articlea71 1.Test Facilitya71 1.Training EquipmentAdditional Info: a71 Project: Mars Science LaboratoryApproval Info: a71 Approval Date: 2009-01-23a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
