54mm DMS J450DM & K535DM Case Winding Advisory

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54mm DMS J450DM & K535DM Case Winding Advisory

Postby CATO » Wed Nov 07, 2018 11:02 am

11/6/2018
54mm DMS™ J450DM & K535DM Case Winding Advisory



Dear AeroTech/RCS Dealers and Customers,

It has come to our attention that there may be an issue with some of the current production run of 54mm J450DM and K535W Disposable Motor System™ (DMS) single-use motors. AeroTech’s casing supplier apparently mixed some out-of-specification cases in with their latest shipment. It appears to only affect the 4-grain 54mm case, and it appears that about 35% of the cases have a winding angle significantly steeper (about 75 degrees) than the 55 degree specification. The steeper winding angle significantly reduces the strength of the case. This was not discovered during the receiving inspection, as a sample percentage of the cases are measured.

DM_WIND_ANGLE.jpg
DM_WIND_ANGLE.jpg (13.37 KiB) Viewed 1248 times


The motors and lot numbers that are affected are:

J450DM, lot number 092818 (22 produced)
K535W, lot numbers 092418 (13 produced) and 101718 (20 produced)

Two J450DMs failed at Midwest Power last weekend, the first failure resulted in separation of the case just forward of the nozzle, and the second failed just aft of the forward bulkhead. There were no K535W failures and a number of current production K535Ws were flown without incident.

We are advising our customers and dealers of this issue at our earliest opportunity, and asking them to check their stock and notify us (and the dealer’s customers) if there is a discrepancy. A quick check with a protractor can determine if the wind angle is correct on the case.

On our end, production is being directed to inspect 100% of all fiberglass cases upon receiving. The vendor has been advised of the issue, and directed to scrap all out-of-specification material to prevent this from happening in the future.

Your understanding and patience is appreciated, and we thank you for your continued support.

http://www.aerotech-rocketry.com/news.aspx?y=2018#n2179
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