Guided Tour of UAL Maint. Ops Center (long)
Andy Stadler
Yesterday, I was lucky enough to be given a personally guided tour of United's
Maintenance Operations Center (MOC) at San Francisco. The MOC is the head-
quarters of UAL's worldwide maintenance operations. Other repair centers, of
varying sizes, exist around the world, but this is the center of it all. It
was one of those friend of wife of a co-worker deals, but the upshot was that
three of us were escorted through the entire complex for about two hours.
As we entered the frontmost, huge building, our guide informed us of some of
the numbers involved. There are three basic levels of service provided. Over-
night work is basic checkout, cleanup, and simple repairs. A moderate level
of service can be provided to repair major broken items, or to complete items
which periodic inspection, repair or replacement. Airliners don't get "annuals"
of the kind we are used to; They undergo FAA-approved cyclic repair on an
ongoing basis. Finally, the airplanes are brought approximately once every
four years for a major teardown and rebuild. The San Francisco MOC sees about
400 aircraft visits per year, and the engine shop will process about 800-900
engines in that period.
We started by walking through the repair shops. United repairs or maintains
almost all parts and subsystems locally. The only exceptions are proprietary
hardware which a manufacturer wishes to repair themselves, or an item which a
subcontractor can do more cheaply and better. I asked if that meant avionics
and the answer was no, actually it happens more at the other end. For example,
a local metal shop does a very good job with aluminum seat rails. The MOC
maintains a large store of flight-ready parts, so typically a broken part is
replaced immediately from stores, and the broken part is repaired in sequence
in the shop.
The shops complex is, in a word, amazing. For every single part you can think
of, there is a shop. Flight surfaces shop. Galley shop. Seats & Upholstery
shop. Life raft shop. Hydraulic systems shop. Brake shop. Instruments shop.
Avionics shop. There's even a Coffee Maker Shop. It just went on and on.
The ostensible purpose of our visit was to discuss data-processing opportuni-
ties, so we looked at the parts tracking system. For every part, there is a
tag which indicates flyable status, repair status, history, etc. Every single
part has a complete history log - hours flown on which airplanes, repairs made,
etc. United maintains a separate part number for every single piece of each
type of aircraft. For the entire fleet, there are 350,000 unique kinds of
parts. And this is for a Boeing + Douglas fleet only. No TriStars, no AirBus.
Each technician, by the way, is qualified on a part-by-part basis.
Next we stepped out into the "narrow-body bays". These are giant hangers where
the bulk of the work is done. Most of these are left over from prop days, and
you can see how some jets fit better than others. We saw one bay which was more
than big enough for the fuselage and wing, but the door was too low for the
vertical tail. United's solution was to build a special tractor rig which
elevates the nosewheel (lowering the tail), wheels the aircraft in, and then
levels it when the tail is inside the doorway. Each bay is designed for a
specific type of airframe. United builds its bays with permanent scaffoldings
which close around the airframe after it is parked, providing excellent access
to all surfaces. There are also a few bays which are unconfigured, using move-
able platforms to provide more flexibility for unscheduled work.
Every airplane which comes in has a set of required maintenance operations,
plus a list of squawks, and finally a painstaking inspection to turn up any
other problems. Once you have a pile of repair orders, how do you schedule
the work? Currently, it's done -manually-. A maintenance scheduler literally
shuffles the slips into an order which hopefully takes into account all
dependencies limits dead time.
Airplanes which come in for major teardown/rebuild used to take about 20-25
days to do, but as airframes age and more inspections are required, that time
is rapidly escalating - it's now 50-60 days for older models such as DC-8's,
727s, and older 737's and 747's. United is growing so rapidly that normal
purchasing is not really helping - the older airplanes keep flying. The MOC
used to handle repairs for a number of outside airlines, but they are so full
these days that it's a thing of the past. We learned that United is actively
seeking a site for a second MOC. The new Denver airport is a possibility, but
as United's Atlantic business grows, the east coast becomes more and more
enticing.
We next walked outside across the tarmac into the wide-body hangar. This
hangar is less structured - it's basically a huge building with rigging hanging
from the ceiling. How huge? Well, yesterday, the following were parked fully
inside: 747-200. DC-10. Two 727's. 747-SP. And there was room for another
DC-10 and at least two 737's. We got to climb aboard the 747-200, which was
in the final stages of a major rebuild. It was amazingly shiny (new paint)
and the interior was immaculate. I had sort of hoped it would be in a more
disassembled condition but it was still pretty neat. I did of course sit in
the cockpit and make vroom-vroom noises, but there were tags on many of the
controls - "don't touch this". We also got to poke around a bit into the
galley and cargo areas.
Looking at the 747-SP got us talking about aircraft procurement. United got
its fleet of 8 -SP's from Pan Am, one of which had originally come from another
airline and is a one-of-a-kind, which means that they have two fleets - a fleet
of seven and a fleet of one. Remember that each fleet means a separate set of
maintainance procedures, a seperate set of parts lists, etc, etc.... An inter-
esting note is that United was -very- unhappy with the SP's in general, as
delivered, and spent quite a bit of time on each one getting it up to their
fleet standards. In general, they set fairly high standards for flying
condition of their aircraft. This causes some problems when new aircraft are
delivered. For tax purposes, United takes delivery of its Boeing jets in
Vancouver BC, flies them down to SFO, and (if all goes as corporate HQ would
like it to) immediately puts them into service. In reality, however, United
literally returns many of the new aircraft after the 3 hour "test flight". I
was surprised that you could find things in a simple three hour flight that
Boeing's QA couldn't find in it's postmanufacture phase, but in fact they do.
Another (long) walk took us to the engine shop. First we entered the engine
test building. There are two test cells, each with universal rigs for all of
the different engines United flies with. Every engine is tested here before
it leaves the MOC. The actual cells are heavily insulated, and unmanned when
an engine is running. The engine tests are operated by an HP minicomputer,
which has saved a tremendous amount of money because it used to take 30 minutes
to run the engine manually through all of its tests, and the computer can do it
in less than 10 - this saves quite a bit of fuel.
Next to the test cells is a power cogeneration plant. All of the electrical
and steam needs, plus extra power sold back to PG&E, is generated by a turbine
equivalent to a single DC-10 engine. The plant runs on natural gas OR jet
fuel - convenient given its on-airport home.
Finally we entered the engine shop, where engines are torn down, repaired and
rebuilt. Fairly major work is done locally, including re-machining of parts,
blade disk balancing, etc. The engine building includes a complete, large-
scale machine shop capable of just about anything. Taken together with the
smaller machine shops scattered around the MOC, they represent the largest job
shop in the Bay Area, and the average job size is... one.
We took a quick look at the parts retrieval system - one of those wonderfully
baroque systems with pneumatic tubes and little robotic carts driving all over
the complex. We asked about turnaround times. For a real rush, a part can
conceivably be in a mechanic's hand in ten minutes from his/her request. Other
priority levels are 30 minutes, 1 hour, or 1 day.
Finally we entered the central maintenance scheduling center. From here, all
United repairs worldwide are coordinated. The system is tied in with the air-
craft scheduling system (although that's done elsewhere) so that airplanes can
be re-routed based on repair needs. There are 12 smaller maintenance centers
worldwide, but all the work they do, and decisions of where to send each plane
for which repairs, all come out of a single room at SFO. We also saw the
"crisis center", a room reserved for major "events".
Well that was about it. Anyone who lives in the bay area has driven past the
giant "United Airlines" building just north of the airport. But you have to
go inside, and walk around, to really realize just how huge the complex is. If
you were to walk around the perimeter of the building, you would have traversed
about two miles - zigzagging around, I think we certainly did. No wonder we
saw bikes and trikes everywhere. I came away pretty amazed at the scale of
what they do. And do, and do, and do... 24 hours a day.
--Andy sta...@apple.com
Geoff Miller
In article <56...@apple.Apple.COM> sta...@Apple.COM (Andy Stadler) writes:
>Yesterday, I was lucky enough to be given a personally guided tour of United's
>Maintenance Operations Center (MOC) at San Francisco.
Thanks for taking the time to write a fascinating article, Andy!
>For the entire fleet, there are 350,000 unique kinds of parts. And this
>is for a Boeing + Douglas fleet only. No TriStars, no AirBus.
Actually, unless they were disposed of very recently, United does have some
TriStars (-500s); they were obtained from Pan Am.
------
>Airplanes which come in for major teardown/rebuild used to take about 20-25
>days to do, but as airframes age and more inspections are required, that time
>is rapidly escalating - it's now 50-60 days for older models such as DC-8's,
>727s, and older 737's and 747's.
I believe the only DC-8s United still has are the stretched Super 60s, which
were reengined with CFM-56s (like the USAF's KC-135Rs) and otherwise upgraded
to Super 70 standard. Did they happen to mention how much longer they plan to
keep them around?
------
>An interesting note is that United was -very- unhappy with the SP's in
general, as delivered, and spent quite a bit of time on each one getting
it up to their fleet standards.
Was this in terms of maintenance, or the way they were configured?
Geoff
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Geoff Miller + + + + + + + + Sun Microsystems
geo...@purplehaze.Corp.Sun.COM + + + + + + + + Menlo Park, California
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Andy Stadler
(Geoff Miller) writes:
>
>Actually, unless they were disposed of very recently, United does have some
>TriStars (-500s); they were obtained from Pan Am.
>
specifically saw bays configured for specific Boeing and Douglas aircraft, and
we talked about specific models quite a bit, and Tristars were never mentioned.
Perhaps UAL acquired them in the deal and never flew them.
>I believe the only DC-8s United still has are the stretched Super 60s, which
>were reengined with CFM-56s (like the USAF's KC-135Rs) and otherwise upgraded
>to Super 70 standard. Did they happen to mention how much longer they plan to
>keep them around?
Nope.
>>An interesting note is that United was -very- unhappy with the SP's in
>general, as delivered, and spent quite a bit of time on each one getting
>it up to their fleet standards.
>
>Was this in terms of maintenance, or the way they were configured?
Definitely it was the maintenance. I can't remember the numbers but our guide
actually mentioned the number of open "squawks" on these airplanes, as
delivered, and it was something like an order of magnitude greater than what
UAL allows....
By the way, there was a bit of interesting history on the SP's. The 8 SP's
which UAL currently flys were originally ordered by UAL, but for various reasons
they were instead delivered to two other airlines. But because they were
ordered by UAL, they were built to UAL specifications. Specifically, they were
the only -SP's with interior corrosion protection. Now, later in their lives,
they are back in UAL livery, and they are supposedly the only -SP's flying
which do NOT have significant corrosion problems.
Andy
Ed Wischmeyer
44571
geo...@purplehaze.Corp.Sun.COM (Geoff Miller) sez...
>I believe the only DC-8s United still has are the stretched Super 60s,
>which were reengined with CFM-56s (like the USAF's KC-135Rs) and otherwise
>upgraded to Super 70 standard. Did they happen to mention how much longer
>they plan to keep them around?
My information is that those DC-8s will be gone this fall, more or less.
Ed Wischmeyer
Kerry Kurasaki
I've flown on quite a few Super DC-8's in the past couple of years and
have done a fair amount of 'cockpit flying' before pushback.
The original plan was for all of the planes to be gone by now. Due to
delivery problems (I guess Boeing can't build them fast enough) that
plan slipped a year. Then Desert Storm came and took some other planes
out of action so they still needed the capacity.
From what the crews told me, most of the planes have already been sold
to foreign airlines, and are on leaseback until United's planes get
delivered. Same conclusion: this fall more or less.
Kerry
Karl Swartz
> Yesterday, I was lucky enough to be given a personally guided tour of United's
> quarters of UAL's worldwide maintenance operations.
I enjoyed Andy's article about two months ago, and had some technical
info to fill in a few blanks, but with research time and lots of other
work going on, I'm just now getting around to posting it. Lots and
lots of little bitty technical details, but far from time-critical.
Hopefully some will find it useful.
In article <55...@jethro.Corp.Sun.COM> geo...@purplehaze.Corp.Sun.COM (Geoff Miller) writes:
> Actually, unless they were disposed of very recently, United does
> have some TriStars (-500s); they were obtained from Pan Am.
In article <1991Sep3.2...@PA.dec.com> y...@wsl.dec.com (Michael Yip (Lt Cmdr - Chief Test Pilot)) writes:
> United did operate a small number of L-1011-500s. It was right after UA
> bought Pan Am's Pacific routes that they used the L1011's on the SF0-NRT
> route as well as some regional routes (NRT-TPE) within the Far East. The
> L1011-500s were included in the same deal/transaction.
United acquired 3 TriStar-500s along with at 11 747SPs in the
February, 1986 acquisition of Pan Am's trans-Pacific routes. These
aircraft were never re-registered from their Pan Am numbers (though
they were quickly repainted) and were used on flights 809 (SFO-OSA)
and 810 (return) and wherever this pair went beyond Osaka, which
varied with the day of the week. Though not scheduled to operate
the LAX-SFO section of this flight they usually did, their only use
in US domestic service to my knowledge.
They were certainly gone by the end of 1989, and probably quite a bit
sooner than that. I'd guess they were replaced when the five former
American 747s arrived in late 1987. Construction number 193Y-1210,
properly a Lockheed L-1011-385-3, operated in United colors as N514PA
and may again be flying former Pan Am routes, now in Delta colors as
N762DA. I don't know the identity of the other two United TriStars
but I suspect they are also operating with Delta logos today.
In article <56...@apple.Apple.COM> sta...@Apple.COM (Andy Stadler) writes:
> Looking at the 747-SP got us talking about aircraft procurement.
> United got its fleet of 8 -SP's from Pan Am, one of which had
> originally come from another airline and is a one-of-a-kind, which
> means that they have two fleets ...
There are actually 11 747SPs operating in United colors, all acquired
from Pan Am as part of the same acquisition that landed the trio of
TriStars. Ten were built for Pan Am, while the 11th was originally
built for Braniff. There are in fact three variations -- the first
six (747SP-21s N140UA thru N145UA) have a 696,000 lb MGTOW while the
remaining four 747SP-21s (N146UA thru N149UA) and the ex-Braniff -27
(N150UA) were upgraded within the past several years to a 702,000 lb
MGTOW. These were separately grouped even at the same MGTOW, so they
probably have other differences, perhaps structural ones that make it
impossible to upgrade the older aircraft. The ex-Braniff plane has a
unique galley configuration and four fewer seats in the first class
cabin, in addition to the higher weight.
In article <56...@apple.Apple.COM> sta...@Apple.COM (Andy Stadler) writes:
> By the way, there was a bit of interesting history on the SP's. The 8 SP's
> which UAL currently flys were originally ordered by UAL, but for various reasons
> they were instead delivered to two other airlines. But because they were
> ordered by UAL, they were built to UAL specifications. Specifically, they were
> the only -SP's with interior corrosion protection.
I don't know about interior corrosion protection, but I doubt that
these planes were ordered by UA or even built to UA specs. Pan Am
was the launch customer for the 747SP, not United, and the first one
is now part of the ex-Pan Am United fleet (N140UA). The other nine
were built over a span of four years, with the last delivered years
before United had its first route out of North America. There would
not have been any reason for United to order the planes at that time.
A few other noteworthy points about the United 747SP fleet is that it
is the largest fleet of them (11 of the 45 built) and includes the
holder of the world record for the fastest flight around the world
(N146UA, aka Friendship One).
In article <56...@apple.Apple.COM> sta...@Apple.COM (Andy Stadler) writes:
> An interesting note is that United was -very- unhappy with the SP's
> in general, as delivered, and spent quite a bit of time on each one
> getting it up to their fleet standards.
It seems like United has gotten a lot of high-maintenance turkeys from
other airlines in their quest for big planes, unlike their fleet of
smaller aircraft which is a remarkably homogenous group that, with the
exception of 25 ex-Frontier 737s (minus 1 WO) and one recently retired
DC-8-71, was all bought new.
The five oldest 747s in United's current fleet, N153UA thru N157UA,
were originally built for American (747-123), and are known amongst
employees as "The Lemon Sisters" for their high incidence of failures
in-service as compared to the 747-122s (which United bought new). I
can't say I've noticed any difference the two times I've been on one,
except that they're the only "three-holers" United has left -- they
only have three windows on each side of the upper deck. (While these
aircraft were built for American, they came to United via indirect
routes. Four of them previously wore the registration of Cargolux,
a cargo carrier from Luxumbourg.)
The 747-238Bs being acquired from QANTAS (ex-QANTAS aircraft; United
is actually leasing them from several leasing companies rather than
purchasing them) apparently have a miserable galley configuration,
with service to the first and business class cabins requiring a long
schlep of supplies from the near-middle of the aircraft. This will
presumably be fixed when time permits, but right now United is in a
hurry to get these planes flying on their new London routes.
Incompatible galleys (specifically, no dumbwaiters to service the
upper cabin) were the stated reason why United never operated the pair
of 747s acquired from Pan Am along with the London routes (N724PA and
N727PA, both 747-212Bs built for Singapore Airlines). Instead, they
were stored at OAK for a month until the deal for the ex-QANTAS planes
was put together, at which time they went to Potomac Capital (one of
the leasing companies) who in turn leased them ... back to Pan Am!
(At the time, rumors circulated that United considered the planes
unsafe due to excessive corrosion.)
Speaking of Pan Am, the only 747s built for United which are no longer
flying for United are five 747-122s (three holers) currently flying
for Pan Am after modification with a side cargo door. Despite the new
paint they still wear United registration numbers.
The seven ex-QANTAS planes apparently suffer another affliction which
they share with N150UA (the single 747SP-27 built for Braniff) -- they
have roaches! Interestingly, one flight attendant spoke in a sad
voice of the poor, orphan Braniff plane, hardly the disdain apparent
for The Lemon Sisters.
For the record, here's a summary of United's current 747 fleet:
10 747SP-21 N140UA-N149UA ex-Pan Am
1 747SP-27 N150UA ex-Pan Am (built for Braniff)
5 747-123 N153UA-N157UA ex-American (The Lemon Sisters)
13 747-122 N4714U-N4735U bought new
2 747-222B N151UA-N152UA bought new for JFK-NRT
5 747-238B N158UA-N165UA ex-QANTAS (2 more in 91/92)
8 747-422 N171UA-N178UA bought new
---
44
Two more 747-422s were due this month and perhaps are already in
service. Five more remain on the current order, with another thirty
(plus thirty options) coming from a second order.
--
Karl Swartz |INet k...@ditka.chicago.com
1-415/854-3409 |UUCP uunet!decwrl!ditka!kls
|Snail 2144 Sand Hill Rd., Menlo Park CA 94025
"The more people I meet the more I like my dog."