Narrative:

The news and pictures thus far relating to the horizontal stabilizer assembly contain certain facts that should be considered in the investigation and the ongoing inspections: 1) the possible supplier of the jackscrew assembly is listed on a website which is titled 'broker and reseller index page.' on jan/xa/95 most of the assets were sold by its parent company. 2) the failure mode for a recirculating type ball screw could be a matter of the unit tightening up due to ball failure, or the screw or nuts or both coming apart because of materials or heat treatment. If this is the case, inspections checking for end play might not reveal a problem. By checking the drive motor amperage, the tightening up would be revealed. The shards of metal wrapped around the screw would seem to indicate that the drive motor worked very hard to create that condition. 3) the visual inspection for debris below the assembly should be reviewed because, in most instances, even a small amount of debris indicates failure is on the way. 4) one plane inspected after the crash apparently had an assembly that had not been lubricated, which would certainly call for a review of procedures. Most often, this type of assembly would be lubricated by the original manufacturer. It would seem that somehow, in the following assembly operations, the lubricant was removed. Callback conversation with reporter revealed the following information: the reporter is a third generation mechanical engineer, owner of his company, with a high number of years as a screw/nut assembly specialist and a contract manufacturer for large industrial corporations. With reference to his report, areas of concern by number, see below: 1) the reporter attached 13 pages of graphics to indicate the possible source of parts. There was an inferred allegation of low financial health within those corporations. This was submitted due to a newspaper report on problems with 'parts suppliers.' his personal experience indicated a problem in tracing the actual manufacturer of parts. His one dealing with a 'reputable' united states part maker traced the faulty parts through japan, taiwan and on to china, bearing maker unknown. His bearings had not been properly 'heat treated.' (outside layer of ball bearing peeled away. This affects directly the quality of the bearings in the circulating type ball screw assembly working on the jack screw.) 2 and 3) this deals with the crux of the matter, the type of inspections performed. The current inspection procedure is to test for 'end play' of the jack screw. Reporter takes exception to this procedure. If there are any metal fragments, even microscopic in size, the end play may be reduced due to a 'holding' anomaly on the jack screw itself by the 'tightened' ball assembly. Reporter takes extreme exception with the alleged remark by maintenance personnel that, '...a certain amount of debris is acceptable...' he maintains that any debris is a sign of metal deterioration. Reporter asserts that the best way to check for any impending problems is to test the amperage readouts during trim motor operation. If there is wear on any parts, the bearings or jack screw would impede the normal running of the ball assembly and increase the amperage required. Aircraft manufacturer should have basic motor amperage requirements for normal readings. 4) lubricant contamination by ball bearing flaking is not evident in all cases to the eye but would be more likely to be detected by the amperage test while actuating the motor. The transfer of basic tool and die making to overseas manufacturers is part of the cost control that has been run in the united states. It seems that the agencies monitoring the quality control of parts has to assume a wider view of the overall problem of who made the parts and the technique used by unknown parts makers that affect the overall quality of those parts. Reporter felt that the first noise heard was the release of ball bearings from the nut assembly.

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Original NASA ASRS Text

Title: A CONTRACT MANUFACTURER'S OPINION ON A POSSIBLE PROB WITH THE PROC BEING USED IN THE INSPECTIONS OF MD80 STABILIZER TRIM, JACK SCREW ASSEMBLY.

Narrative: THE NEWS AND PICTURES THUS FAR RELATING TO THE HORIZONTAL STABILIZER ASSEMBLY CONTAIN CERTAIN FACTS THAT SHOULD BE CONSIDERED IN THE INVESTIGATION AND THE ONGOING INSPECTIONS: 1) THE POSSIBLE SUPPLIER OF THE JACKSCREW ASSEMBLY IS LISTED ON A WEBSITE WHICH IS TITLED 'BROKER AND RESELLER INDEX PAGE.' ON JAN/XA/95 MOST OF THE ASSETS WERE SOLD BY ITS PARENT COMPANY. 2) THE FAILURE MODE FOR A RECIRCULATING TYPE BALL SCREW COULD BE A MATTER OF THE UNIT TIGHTENING UP DUE TO BALL FAILURE, OR THE SCREW OR NUTS OR BOTH COMING APART BECAUSE OF MATERIALS OR HEAT TREATMENT. IF THIS IS THE CASE, INSPECTIONS CHECKING FOR END PLAY MIGHT NOT REVEAL A PROB. BY CHECKING THE DRIVE MOTOR AMPERAGE, THE TIGHTENING UP WOULD BE REVEALED. THE SHARDS OF METAL WRAPPED AROUND THE SCREW WOULD SEEM TO INDICATE THAT THE DRIVE MOTOR WORKED VERY HARD TO CREATE THAT CONDITION. 3) THE VISUAL INSPECTION FOR DEBRIS BELOW THE ASSEMBLY SHOULD BE REVIEWED BECAUSE, IN MOST INSTANCES, EVEN A SMALL AMOUNT OF DEBRIS INDICATES FAILURE IS ON THE WAY. 4) ONE PLANE INSPECTED AFTER THE CRASH APPARENTLY HAD AN ASSEMBLY THAT HAD NOT BEEN LUBRICATED, WHICH WOULD CERTAINLY CALL FOR A REVIEW OF PROCS. MOST OFTEN, THIS TYPE OF ASSEMBLY WOULD BE LUBRICATED BY THE ORIGINAL MANUFACTURER. IT WOULD SEEM THAT SOMEHOW, IN THE FOLLOWING ASSEMBLY OPERATIONS, THE LUBRICANT WAS REMOVED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS A THIRD GENERATION MECHANICAL ENGINEER, OWNER OF HIS COMPANY, WITH A HIGH NUMBER OF YEARS AS A SCREW/NUT ASSEMBLY SPECIALIST AND A CONTRACT MANUFACTURER FOR LARGE INDUSTRIAL CORPORATIONS. WITH REFERENCE TO HIS RPT, AREAS OF CONCERN BY NUMBER, SEE BELOW: 1) THE RPTR ATTACHED 13 PAGES OF GRAPHICS TO INDICATE THE POSSIBLE SOURCE OF PARTS. THERE WAS AN INFERRED ALLEGATION OF LOW FINANCIAL HEALTH WITHIN THOSE CORPORATIONS. THIS WAS SUBMITTED DUE TO A NEWSPAPER RPT ON PROBS WITH 'PARTS SUPPLIERS.' HIS PERSONAL EXPERIENCE INDICATED A PROB IN TRACING THE ACTUAL MANUFACTURER OF PARTS. HIS ONE DEALING WITH A 'REPUTABLE' UNITED STATES PART MAKER TRACED THE FAULTY PARTS THROUGH JAPAN, TAIWAN AND ON TO CHINA, BEARING MAKER UNKNOWN. HIS BEARINGS HAD NOT BEEN PROPERLY 'HEAT TREATED.' (OUTSIDE LAYER OF BALL BEARING PEELED AWAY. THIS AFFECTS DIRECTLY THE QUALITY OF THE BEARINGS IN THE CIRCULATING TYPE BALL SCREW ASSEMBLY WORKING ON THE JACK SCREW.) 2 AND 3) THIS DEALS WITH THE CRUX OF THE MATTER, THE TYPE OF INSPECTIONS PERFORMED. THE CURRENT INSPECTION PROC IS TO TEST FOR 'END PLAY' OF THE JACK SCREW. RPTR TAKES EXCEPTION TO THIS PROC. IF THERE ARE ANY METAL FRAGMENTS, EVEN MICROSCOPIC IN SIZE, THE END PLAY MAY BE REDUCED DUE TO A 'HOLDING' ANOMALY ON THE JACK SCREW ITSELF BY THE 'TIGHTENED' BALL ASSEMBLY. RPTR TAKES EXTREME EXCEPTION WITH THE ALLEGED REMARK BY MAINT PERSONNEL THAT, '...A CERTAIN AMOUNT OF DEBRIS IS ACCEPTABLE...' HE MAINTAINS THAT ANY DEBRIS IS A SIGN OF METAL DETERIORATION. RPTR ASSERTS THAT THE BEST WAY TO CHECK FOR ANY IMPENDING PROBS IS TO TEST THE AMPERAGE READOUTS DURING TRIM MOTOR OP. IF THERE IS WEAR ON ANY PARTS, THE BEARINGS OR JACK SCREW WOULD IMPEDE THE NORMAL RUNNING OF THE BALL ASSEMBLY AND INCREASE THE AMPERAGE REQUIRED. ACFT MANUFACTURER SHOULD HAVE BASIC MOTOR AMPERAGE REQUIREMENTS FOR NORMAL READINGS. 4) LUBRICANT CONTAMINATION BY BALL BEARING FLAKING IS NOT EVIDENT IN ALL CASES TO THE EYE BUT WOULD BE MORE LIKELY TO BE DETECTED BY THE AMPERAGE TEST WHILE ACTUATING THE MOTOR. THE TRANSFER OF BASIC TOOL AND DIE MAKING TO OVERSEAS MANUFACTURERS IS PART OF THE COST CTL THAT HAS BEEN RUN IN THE UNITED STATES. IT SEEMS THAT THE AGENCIES MONITORING THE QUALITY CTL OF PARTS HAS TO ASSUME A WIDER VIEW OF THE OVERALL PROB OF WHO MADE THE PARTS AND THE TECHNIQUE USED BY UNKNOWN PARTS MAKERS THAT AFFECT THE OVERALL QUALITY OF THOSE PARTS. RPTR FELT THAT THE FIRST NOISE HEARD WAS THE RELEASE OF BALL BEARINGS FROM THE NUT ASSEMBLY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.