lenochs%drcoa1.decnet@drcvax.af.mil (DRCOA1: :LENOCHS) (04/04/91)
From: "DRCOA1::LENOCHS" <lenochs%drcoa1.decnet@drcvax.af.mil>
Subject: Maintenance analysis
(This may or may not be germain to SCI.MILITARY but I'm sending it on
to you anyway. Use or reject at your discretion - LME)
[Fine by me. How does the phrase go - "Amateurs discuss strategy,
armchair generals discuss tactics, professionals discuss logistics?" --CDR]
Some time back (shortly after the start of the air campaign, I
believe), a question was asked about aircraft maintenance calculations.
At least I think so; if not, this is just some rather arcane
information for those readers who are mathematically inclined. :-)
These are the standard USAF calculations used by the Deputy Commander
for Maintenance and staff. Uses include identifying weak spots in the
maintenance organization, manpower planning, upchannel reporting
(everybody has performance standards and the USAF is no exception), and
pointing fingers when the wing commander asks why he has no planes to
fly!
Needless to say, these figures get a *lot* of attention at base level,
since the headquarters staff uses these numbers to figure out how many
planes they will (might) have available at any given time, which in
turn affects which targets get hit and in what order. Too many planes
broken for too long draws the headquarters staff's attention (and the
wing commander definitely doesn't want *that* kind of attention).
Fictitious example: if the F-15Es stay broken too long, then precision
tactical ground attack will have to be shifted to another platform.
This will force all kinds of changes in mission tasking for other
units. Tanker support will change if the strike becomes a Navy
mission, MIGCAP positioning might change, etc. Also, some other
missions might be cancelled because they were follow-on attacks (A-10s
can't go after the troops if the AAA the F-15s were supposed to take
out are still active).
Of course, these numbers and rates are also used to justify maintenance
commanders' promotions (which also makes them quite visible at base
level) and as part of the scoring for the Daedaelian (sp?) Award, given
to the outstanding maintenance units AF-wide.
In the long run, collection of this data fleet-wide gives the planners
and manufacturers reliablity information for future decisions. When
put together with maintenance action data, a fairly good picture of
fleet reliability and spares requirements comes into focus.
During Desert Shield and Desert Storm, only the F-16s home-based in
Spain (deployed to Turkey) and the F-117s had on-line maintenance
information of this type. The rest of the data was lost (sigh).
Anyway...........
First, some definitions:
FMC Fully Mission Capable (100% good to go)
PMC Partially Mission Capable (can perform some of the missions
the system is capable of but not all. Example: the F-15E has
both air-to-ground and air-to-air capability. If the LANTIRN
ground targeting system goes down, that aircraft is PMC)
PMCM Partially Mission Capable for Maintenance (too much higher
priority maintenance is backed up)
PMCS Partially Mission Capable for Supply (have the resources to
fix the plane, but can't get a spare)
PMCB Partially Mission Capable for Both (I have too much work to
do, but it doesn't matter because I can't get a spare anyway)
NMC Not Mission Capable (dead in the water)
NMCM Not Mission Capable for Maintenance (too much work to do)
NMCS Not Mission Capable for Supply (can't get a spare)
NMCB Not Mission Capable for Both (I have too much work to do, but
it doesn't matter because I can't get a spare anyway)
TOTAL DEVIATIONS = MAINT NON-DELIVERY + SUPPLY NON-DELIVERY + GROUND
ABORTS + CANCELLATIONS (OPERATIONAL, WEATHER,
SYMPATHY, OTHER)
explanations: MAINT NON-DELIVERY: maintenance didn't get the plane
ready in time
SUPPLY NON-DELIVERY: supply didn't get the spare to
maintenance in time for them to get the plane ready
as scheduled
GROUND ABORT: aircraft broke after engine start but
before take off
OPERATIONAL CANCELLATION: somebody else already
destroyed the target so why bother :-) , or a higher
priority mission is assigned
WEATHER CANCELLATION: take a guess!
SYMPATHY CANCELLATION: flight leader broke, so
wingman is cancelled
OTHER CANCELLATION: any thing else
TOTAL ADDS = SPARES + OPERATIONAL ADDS + OTHER ADDS
Spares are aircraft swaped in to fill a spot left by
an aborted aircraft. Operational adds are aircraft
added to the frag (planes got fixed early, so why
not use them). Other adds can be things like having
a headquarters type wanting to get in his flying
time for the month, or an observer aircraft.
NET DEVIATIONS = TOTAL ADDS to schedule - TOTAL DEVIATIONS from
schedule
POSSESSED HOURS = FMC HOURS + NMC HOURS + PMC HOURS
FMC HOURS = POSSESSED HOURS - (PMC HOURS + NMC HOURS)
% FMC HOURS = FMC HOURS / POSSESSED HOURS
NMC HOURS = NMCM HOURS + NMCS HOURS + NMCB HOURS
% NMC HOURS = NMC HOURS / POSSESSED HOURS
TNMCS HOURS = NMCS HOURS + NMCB HOURS (total NMCS hours)
% TNMCS HOURS = TNMCS HOURS / POSSESSED HOURS
% NMCM HOURS = NMCM HOURS / POSSESSED HOURS
% NMCS HOURS = NMCS HOURS / POSSESSED HOURS
% NMCB HOURS = NMCB HOURS / POSSESSED HOURS
PMC HOURS = PMCM HOURS + PMCS HOURS + PMCB HOURS
% PMC HOURS = PMC HOURS / POSSESSED HOURS
TPMCS HOURS = PMCS HOURS + PMCB HOURS (total PMCS hours)
% TPMCS HOURS = TPMCS HOURS / POSSESSED HOURS
% PMCM HOURS = PMCM HOURS / POSSESSED HOURS
% PMCS HOURS = PMCS HOURS / POSSESSED HOURS
% PMCB HOURS = PMCB HOURS / POSSESSED HOURS
MC HOURS = FMC HOURS + PMC HOURS
% MC HOURS = MC HOURS / POSSESSED HOURS
The percentages are also called 'rates', i.e., % FMC HOURS is also
called the FMC RATE, etc.
BTW, these are the actual formuale currently used by the F-16, F-15E
and F-117 automated data systems.
Hope you didn't fall asleep during all this!
--
Loyd M. Enochs (ex-USAF) - Dynamics Research Corporation - Andover, MA
Computer Systems Analyst - Smart Data System (F-117 Maintenance and
Operations computer system)