No aircraft engine manufacturer or authorized rebuilder is allowed to use any glass beads.
An AEC tech bulletin (one I could not copy as a PDF here!):
Title: Dangers of contamination from Glass Bead Material
Technical portions are approved by Airmotive Engineering Corp.
T.N. No.: 09-2
Page: 1 of 2
Issued: 2-10-10
Revision: 0
1.0 PURPOSE: To help prevent engine failures
2.0 SCOPE: To alert technicians and mechanics about the perils related to glass beads
3.0 APPLICATION: Maintenance of aircraft piston engines.
4.0 REFERENCE: Engine Manufacturer’s overhaul manuals and service bulletins, service
instructions and service letters (Continuing Airworthiness Instructions) should always be
consulted as the principal authority for any engine overhaul and maintenance information.
5.0 DISCUSSION: One of the methods used by technicians and mechanics to clean component parts
is to shot blast using glass beads. This procedure has some benefits over other cleaning
procedures, but all of the benefits pale in comparison to the devastation that glass beads cause
when they are introduced in any manner into the inner workings of an aircraft piston engine. Even
one glass bead can cause significant damage before it breaks up into glass dust. If it is trapped in a
bearing it does its damage and then can re-circulate to do some more.
Many shops keep glass bead blast media and only use it to clean external parts. Others believe
that proper cleaning will eliminate the hazard. There are two axioms that should be posted in
every engine shop:
1. If glass beads are any where in any quantity in an aircraft repair facility, they will end up
in aircraft engines!
2. The only thing that loosens up and moves glass bead media from the nooks and crannies
of aircraft engines and into areas where they cause the most harm is hot engine oil!
Most engine overhaulers or repairers have experienced problems related to glass beads. However,
many were never aware of the root cause for their problems, and either gave up on the search for a
cause or attributed the cause to something else. This is because glass beads will defy cleaning
efforts and are difficult to identify after the damage is done. Airmotive Engineering Corp. and
Engine Components, Inc. have experienced the problems caused by glass bead blast media many
times over the years. Because of these experiences (i.e. warranty claims), our technicians have
developed highly effective evaluation techniques, and it is rare that positive evidence of glass
beads cannot be found.
T.N. No. 09-2
Revision 0
Dangers of contamination from Glass Bead Material
Page 2 of 2
The photograph below shows glass beads that were solvent washed from behind piston rings of
cylinders sent back to ECi for warranty consideration. The pistons, rings, cylinder bores, and
bearings were severely damaged and unserviceable.
Photo 1: Glass Beads in Engine Oil and Solvent
6.0 Conclusion: It is of utmost importance that glass beads not be used in any manner to clean piston
engine parts. Even one glass bead can cause significant damage, and failure to comply with this
instruction will result in denial of a warranty cl
Re: continentalmotors.aero/xPublications/xService%20Bulletins/ECi%20Archives/09-2/
I rest my case that unless one can almost surgically clean, even an intake, from 100% of all glass beads, other media is preferred.
