I’d like to add a new choice of terms to our ever evolving
aviation lexicon. When an aircraft reaches the end of its life and it’s being
parted out, we’re not removing the parts- we’re harvesting the parts from the legacy asset.
A word that has managed to survive the trendy, revisionist
makeovers is ‘cannibalize’, as in cannibalizing aircraft parts. Used
interchangeably is the equally, potentially offensive word, ‘robbed’ aircraft
parts. My, oh my, I’m wont to retreat to a safe place and curl into a fetal
position at the use of such utterances. We certainly need kinder-gentler
expressions! But guess what? They’re here to stay. Get over it.
So…what are we talking about? A likely scenario:
An aircraft is at the gate for the first flight of the day
and passengers are loading. By the way, at any given airline, the bank of first
flights is closely monitored in real time by many different organizations, and
the percentage of flights making it out of the chocks on time is a key
performance metric; this, since any delay or cancellation is going to have a
cascading effect on the subsequent flights of the day. For the first flight of
the day, the flight crew has to perform lengthier aircraft systems checks, and during
these checks our air crew observes a fail during a bite test
(Built-In-Test-Equipment). The air crew consults its MEL (Minimum Equipment
List) and confirms the failure can’t be deferred; it must be fixed. The aircrew
calls its Maintenance Operations Control center (MOC), who dispatches
technicians to the aircraft. The techs note that the Fault Isolation Manual
(FIM) requires the replacement of an LRU (Line Replaceable Unit). The problem
is there is zero stock; and the parts-pooling partners are similarly zero
stock; drats! These savvy technicians know however, that an identical aircraft
is parked on the ramp awaiting lengthy repairs due to a bird strike. The techs
call MOC for authorization to take the part off the idle asset, and use it on
the now-waiting aircraft full of passengers. Twenty minute later the techs are
on the flight deck signing off the offending write-up with the aircrew, and
minutes later the tug spews its first puff of smoke as the aircraft backs out
of the gate. In many an airline’s GMM or GPM (General Maintenance Manual or
General Procedures Manual; in the USAF the equivalent is Air Force Instruction
21-101, Aircraft and Equipment Maintenance Management), this procedure is
referred to as cannibalizing or robbing the part. To be sure, there are
probably, other more kinder-and-gentler titles of the procedure, but these are
the prevalent ones.
In the USAF, the same action is also called cannibalizing,
and only certain Maintenance Management persons are certified to authorize such
an action on the scene. I had this certification. Without doubt, cannibalizing
or robbing must always be an option of last resort; all efforts must be
expended to locate the part first from normal supply channels. It is no
surprise then, that cannibalization rates in the airlines or military are a
closely monitored metric since it reflects on the effectiveness of the
inventory control system. Higher cannibalization rates tend to be accepted
through clenched teeth for parts that are out of production. Higher rates may
also be the natural consequence of operators who deliberately choose to be under-spared
for certain assets to conserve cash.
Up to this point, the process to rob that part sounds easy…but it’s not. Consider the following:
- Before the part is robbed (yes I switched to
using this other term, from cannibalizing, since it’s easier to type), you must establish that the aircraft being
robbed from has no existing write-ups against the system you intend to rob the
part from. This is routinely accomplished by exam of the aircraft log book or
equivalent electronic listing. In many cases you’re looking for the associated
ATA chapter system. The idea here is that if the ATA system you intend to rob
the part from has no write-ups, you can reasonably conclude the part remains in
airworthy serviceable as installed.
- The logbook entries in both the aircraft
involved must be made precisely and
in accordance with the written procedures.
- In many cases, the part was initially ordered
against the original aircraft with the write-up before the discovery of
zero-inventory was confirmed. Since the part has now been robbed to fill the
need, procedures must include that the part-order be amended to show that the
aircraft robbed-from is now in need of it.
- Many procedures I’ve seen require that as soon
as the part is removed from the robbed-from aircraft, a tag must be affixed.
Often it is this tag that facilitates the corrections to inventory orders
- There are two special cases for close attention
when considering robbing a part:
o Is it a part that has scheduled overhaul or
other maintenance requirements? If so, the airline’s tracking system must be
amended to show the current installed-position of the part.
o Is the part an LLP, Life Limited Part? My
experience is that these parts are rarely robbed since nearly all require
extensive disassembly in order to facilitate the removal and installation.
Nonetheless, it remains a possibility and must be carefully considered for
remaining time or cycles and to be tracked as concerns its current installed
How about swapping?
Swapping exists for one reason: To facilitate the
troubleshooting process. For example, an aircraft has a write-up, but
experience has shown that several LRUs (Line Replaceable Units) are equally
capable of causing the fault. Any experienced technician will tell you that
there has never been written a perfect Troubleshooting Logic Tree or FIM. Swapping
parts that are the same part number to see if the fault is eliminated, or follows
to the other swapped position, is really a great troubleshooting tool to
confirm the source of the fault. This also helps reduce those pesky
No-Fault-Found (NFF) charges. There are two scenarios for swapping:
1. Swapping in the same aircraft tail number:
Due to redundant aircraft systems, it is
not unusual to find the same part number LRU installed for a Right or Left
system, or in some cases a left, center, and right system, or system 1, 2, 3,
or colored systems. It’s been my experience that technicians often perform this
type of troubleshooting without the necessity of informing anyone or filling
out any tags or other documentation. The conscientious technician always will
return the parts to their original positions once the troubleshooting process
has concluded. In some cases the airline may have a hard rule that any such
activity is strictly documented in accordance with their manuals, and for good
2. Swapping between aircraft of different tail
In some cases, this is the preferred or only
option for swapping during troubleshooting. In this circumstance there are
usually strict controls on documenting the actions taken.
If you know of any kinder-gentler, mood-ameliorating terms
in use to describe these actions don’t hesitate to post a comment.
Over ‘n out
Roy “Royboy” Resto