Concorde Maintenance & Servicing
Concorde had to have the following checks:
ENGINE MAINTENANCE & CHECKS
The Olympus 593-610 engine was a tough, hard-working aircraft engine, yet it was so highly tuned as to squeeze every last ounce of efficiency from it.
It was unique. There was nothing to compare it.
In service its reliability was good-very good: the checks were varied to monitor the engine health, to intercept a problem before it arose and for preventive maintenance.
Maintenence Checks were broken down into five headings:
SOAP, MCD, EGT, oil consumption and borescope.
SOAP – SPECTROGRAPIC OIL ANALYSIS PROGRAMME
Every 50 flying hours oil samples were taken from each engine, at Heathrow, within 2 hours of shut-down and before replenishment. Simples were dispatched on a daily to a company at Fairoaks in Surrey for the same-day laboratory analysis. Initially, the samples were scanned for traces of iron, magnesium and silicon, the units of measurements being parts per million (ppm). Should any of these elements exceed its alert level by a particular amount, then the Magnetic Chip Detectors (MCD) were analysed and considered in conjunction with the spectro results before the engine could continue in service. Whatever an alert was met, a recurring requirement was raised directing a spectro and MCD check at every return to base. Thus critical decisions on engine serviceability used both sets of evidence.
MCD – MAGNECTIC CHIP DETECTORS
The Olympus has three magnetic Chip Detectors and a specialist group to analyse them. The three MCD’s were strategically placed within the engine as follows:
In the left-hand gearbox scavenge filter trapping debris from the thrust bearings (2 and 3) and the left-hand gearbox.
In the right-hand gearbox scavenge filter trapping debris within the right-hand gearbox.
In the main external return-flow pipe. This one designed ‘Master MCD’; it attracted debris from the total system.
Every service checks – 175 flying hours – all three MCDs were removed for deposit analysis. ‘Big lumps’ went under the microscope; a rolled flaky appearance was indicative of a bearing problem, while more granular particle suggested gear of shaft frottage. But it’s the sludge that was most fascinating. To put it another way, reading message was in the ring around the rim.
The sludge sample was bombarded with X-rays. Each chemical element in the amalgam would emit a different radiation. Using a computer, programmed with radiation signature of elements used in engine metals, the analyst would be presented with readout of the detailed composition of the sludge. Moving on a step further, knowing exactly what each engine alloy was made of, and introducing graphics, the sample’s footprint could be compared with known footprints: eg No.1 bearing housing was made from an iron-based alloy, MSRR 6544 – in addition to its base material it had 25% carbon, 14% chrome, 1% manganese, 1% nickel and 0.8% silicon. Having matched the footprint, one could point fairly precisely to the assemble under suspicion.
It was well known that a newly installed engine would generate a relatively high level of debris as shafts, gears and bearings bedded-in and grease, used in engine build, washed down-grease raises the silicon content.
Nevertheless, the checks remained. An engine must demonstrate three consecutive good checks before removed from the ‘alert’ file.
EXHAUST GAS TEMPERATURE (EGT)
The combustion chamber, even in its latest incarnation, still took a battering from the high energy gas flow. Deterioration, before becoming damaged would still upset temperature patterns, and to catch a trend before it became a problem had huge benefits.
In 1986 Rolls-Royce devised an EGT trend analysis program to be loaded into a programmable Sharp 1248 hand-held calculator. This became a routine part of the flight engineer’s in-flight tasks. Using real-time data, even the smallest divergence of EGT was apparent; recording and plotting created the trend. Its ‘raison d’ etre’, a raising trend was indicative of a problem within the combustion chamber/turbine area-cooling holes unzipping, vaporizer cracking, hot streaking – 20C up would result to base. A dynamically increasing trend would require a shut-down judgment. A minor reducing trend would result from compressor deterioration (nicks, scratches, erosion etc). Cruise EGT, incidentally would be about 650c
At each station, oil uplift and flight time were assessed to produce a consumption rate; once again recorded and plotted so the trends were immediately apparent.
The medical people call it an endoscope. It’s the same minaturised viewing technology. Engines are designed with inspection points in key areas, blanked-off in service, but readily available for either routine internal inspections or ‘alert level’ extras when SOAP, MCD or EGT require.
AIRFRAME & SYSTEMS MAINTENANCE
(before each flight)
Routine operations and inspections every 24 hours according to checklists
Routine operations and inspections every 210 flight hours according to checklists. In addition to operations specific to this type of check, Check A also includes the maintenance operations covered in daily and weekly checks.
Routine operations and inspections carried out every 420 flight hours according to checklists.
Routine operations and inspections carried out every 1,680 flight hours according to checklists.
Routine operations and inspections carried out every 6,000 flight hours according to checklists.
Check D or major overhaul, sometimes called the ‘M’ check
Routine operations and inspections carried out every 12,000 flight hours according to checklists. This is an extensive maintenance operation which required the total dismantling of the aircraft. Inspections are carried out on the airframe and a large number of parts were systematically replaced. The plane was grounded for nearly one year. The technical monitoring of the engines were carried out on the French airframes by the Air France Industrial Logistics Branch, using instructions from the engine manufacturers Rolls Royce and Snecma.