2nd Sep 2010, 19:44
permalink Post: 191
Hydraulic failures
I had the pleasure of one trip as SLF on Concorde LHR - JFK (1978/9? grey cells depleting) which involved a return to LHR after dumping fuel due to hydraulic failure of two systems. No complaints from me, two take offs and landings for the price of one plus two hours of additional catering at LHR while the aircraft was fixed. Big run on asprins by the time we approached JFK!
However on the second departure the AC also suffered loss of hydraulic systems and I understood that it arrived at JFK on one system. After a storm delay at JFK I departed on AA listening to the ATC on the IFE with the Concorde following. Yet again the Concorde requested fuel dump and return due to hydraulic failures. The previous days I believe the Concorde had also experienced hydraulic failures and at one point BA cancelled some flights. AF were not experiencing the same problems and I read several years later that the problem was attributed to minute quantities of water being introduced into the system by a repenishing tanker being parked outside, wheras AF stored their tanker inside. The water then generated steam when the system ran with consequent seal failures.
Is the above cause correct, or was there more to the story?
Apart from all the normal Concorde observations, I also noticed that when trolling around over Bristol dumping fuel at a relatively high AoA the rear outboard surfaces, I was seated at the rear, vibrated at an alarming aplititude and frequency. Would this be caused by aerodynamic buffet or rapid auto pilot control inputs?
Thanks in anticipation.
However on the second departure the AC also suffered loss of hydraulic systems and I understood that it arrived at JFK on one system. After a storm delay at JFK I departed on AA listening to the ATC on the IFE with the Concorde following. Yet again the Concorde requested fuel dump and return due to hydraulic failures. The previous days I believe the Concorde had also experienced hydraulic failures and at one point BA cancelled some flights. AF were not experiencing the same problems and I read several years later that the problem was attributed to minute quantities of water being introduced into the system by a repenishing tanker being parked outside, wheras AF stored their tanker inside. The water then generated steam when the system ran with consequent seal failures.
Is the above cause correct, or was there more to the story?
Apart from all the normal Concorde observations, I also noticed that when trolling around over Bristol dumping fuel at a relatively high AoA the rear outboard surfaces, I was seated at the rear, vibrated at an alarming aplititude and frequency. Would this be caused by aerodynamic buffet or rapid auto pilot control inputs?
Thanks in anticipation.
2nd Sep 2010, 23:55
permalink Post: 192
Hi canuck slf, Your incident was not the hydraulic contamination one, I'll describe that one in a minute or so below.
As far as your adventure goes, in the early days of Concorde operation there was an on-going issue of hydraulic seal failures. This led to the sort of thing that you described, where a major seal failure would occur, resulting in the loss of a main system. The standby Yellow system would be switched in to replace the failed one, and depending on the nature of the initial failure, could leak out of the same failed seal. (There were a couple of 'common areas', they were the intake spill door jack, and the Powered Flying Control Units; failures here could result in a double system fail). Your incident was almost certainly due to one of these cases. In the early 1990's the original Neoprene hydraulic seals were replaced with a new Viton GLT seal; this material had far superior age shrinking characteristics to Neoprene, and more or less cured the problem overnight. Eventually all the seals in each aircraft were replaced, and apart from a very few isolated cases, dual system losses were eliminated forever. Air France suffered a similar proportion of failures, however as their flying hours were a fraction of BA's, the effects were not as immediately apparent.
As far as far as the hydraulic contamination story goes, this happened in 1980 but involved one aircraft only, G-BOAG, but in it's original registration of G-BFKW. (having previously been on loan from British Aerospace, where it flew originally as a 'white tail' under this registration). The fragile nature of Concorde hydraulic fluid was not fully understood at this time, and as you say, a hydraulic drum dispenser had inadvertently been left exposed to the atmosphere, and had subsequently suffered water contamination, and this contaminated fluid had found it's way into G-BOAG. Now this hydraulic fluid, CHEVRON M2V has only two vices: One is that is extremely expensive, and the second is that it is highly susceptible to water contamination, EXTEMELY SO. If my memory serves me correctly, the maximum allowable level of water in the fluid is about 8ppm. (parts per million) and the fluid that was analysed after G-BOAG's problems was at about 30 ppm. The water deposits in the fluid gave the equivalent effect of 'rusting up' of critical hydraulic components. I was investigating an air intake control defect the previous day to the incident, but like everybody else had no idea that the real issue here was one of major systems contamination. We were all convinced that we had nailed the problem, only to find that the aircraft turned back on it's subsequent LHR-JFK sector with more serious problems, not only affecting the air intakes, but the artificial feel system also. It was now that we realised that there had to be a hydraulics problem here, and after fluid analysis, the awful truth was discovered. After this event, and the fragilities of M2V fluid were better understood, a strict regime of housekeeping was put in place in terms of fluid storage, and no such incidents with BA ever occurring again. The aircraft itself did not fly again for nine months, all components that were affected were removed from the aircraft and completely stripped and overhauled. Also all of the system hydraulic lines had to be completely purged, until there were no further traces of any contamination. After the aircraft was finally rectified, she successfully again returned to service with her new 'BA' registration of G-BOAG. However the following year, during a C Check, it was decided that due to spares shortages, and the closure of the LHR-BAH-SIN route, there just was not being enough work for seven aircraft, and therefore G-BOAG would be withdrawn from service. (In terms of spares, BA at the time for instance only had six sets of aircraft galleys, as aircraft went in for C checks the galley was 'robbed' to service the aircraft coming out of it's own C check). The aircraft was parked in a remote hangar, and was only visited when a component had to be 'robbed' for another Concorde, and the aircraft soon fell into disrepair, was filthy externally and became a really sad sight. Many people (not myself I might add) were adamant that G-BOAG would never fly again. However, in 1984 things had really started to improve for Concorde, with the charter business increasing and the LHR-JFK route in particular becoming a staggering success. It was decided that OAG would be returned to an airworthy condition. In 1985, with a fresh new interior, and with the new BA colour scheme, she was finally returned to service; and remained as one of the mainstays of the fleet right up to the end of Concorde services in October 2003. She now resides at the Boeing Museum of Flight in Seattle. (I have particularly fond memories of G-BOAG; in a previous post I mentioned flying through an electrical storm in late 1991 over Saudi Arabia, while returning from BKK-BAH to LHR. What I forgot to mention was the spectacle of DOZENS of fierce fires burning on the ground, towards our starboard horizon. These were Sadams oil fires, still burning in Kuwait. It made a sombre contrast to the amazing electrical spectacle right in front of us).
As far as low speed flying control activity was concerned, this was a combination of the fairly flexible outer wing sections, being buffeted by low speed turbulence (the wing tip tanks 5A & 7A also being empty), as well as some autostab inputs. This was perfectly normal, and part of the design our aircraft. However the development aircraft had even more flexible outer wing sections, which used to almost straighten up in high speed flight. However due to fatigue concerns, external lateral stiffeners were added to the underside of the wings during production of the airline aircraft. (these can be easily seen from underneath the wings, just outboard of the nacelles). Unfortunately these external stiffeners also resulted in over a one tonne fuel penalty to the production aircraft, due to increased weight, as well as higher drag in a critical part of the wing aerodynamic surface.
Dude
As far as your adventure goes, in the early days of Concorde operation there was an on-going issue of hydraulic seal failures. This led to the sort of thing that you described, where a major seal failure would occur, resulting in the loss of a main system. The standby Yellow system would be switched in to replace the failed one, and depending on the nature of the initial failure, could leak out of the same failed seal. (There were a couple of 'common areas', they were the intake spill door jack, and the Powered Flying Control Units; failures here could result in a double system fail). Your incident was almost certainly due to one of these cases. In the early 1990's the original Neoprene hydraulic seals were replaced with a new Viton GLT seal; this material had far superior age shrinking characteristics to Neoprene, and more or less cured the problem overnight. Eventually all the seals in each aircraft were replaced, and apart from a very few isolated cases, dual system losses were eliminated forever. Air France suffered a similar proportion of failures, however as their flying hours were a fraction of BA's, the effects were not as immediately apparent.
As far as far as the hydraulic contamination story goes, this happened in 1980 but involved one aircraft only, G-BOAG, but in it's original registration of G-BFKW. (having previously been on loan from British Aerospace, where it flew originally as a 'white tail' under this registration). The fragile nature of Concorde hydraulic fluid was not fully understood at this time, and as you say, a hydraulic drum dispenser had inadvertently been left exposed to the atmosphere, and had subsequently suffered water contamination, and this contaminated fluid had found it's way into G-BOAG. Now this hydraulic fluid, CHEVRON M2V has only two vices: One is that is extremely expensive, and the second is that it is highly susceptible to water contamination, EXTEMELY SO. If my memory serves me correctly, the maximum allowable level of water in the fluid is about 8ppm. (parts per million) and the fluid that was analysed after G-BOAG's problems was at about 30 ppm. The water deposits in the fluid gave the equivalent effect of 'rusting up' of critical hydraulic components. I was investigating an air intake control defect the previous day to the incident, but like everybody else had no idea that the real issue here was one of major systems contamination. We were all convinced that we had nailed the problem, only to find that the aircraft turned back on it's subsequent LHR-JFK sector with more serious problems, not only affecting the air intakes, but the artificial feel system also. It was now that we realised that there had to be a hydraulics problem here, and after fluid analysis, the awful truth was discovered. After this event, and the fragilities of M2V fluid were better understood, a strict regime of housekeeping was put in place in terms of fluid storage, and no such incidents with BA ever occurring again. The aircraft itself did not fly again for nine months, all components that were affected were removed from the aircraft and completely stripped and overhauled. Also all of the system hydraulic lines had to be completely purged, until there were no further traces of any contamination. After the aircraft was finally rectified, she successfully again returned to service with her new 'BA' registration of G-BOAG. However the following year, during a C Check, it was decided that due to spares shortages, and the closure of the LHR-BAH-SIN route, there just was not being enough work for seven aircraft, and therefore G-BOAG would be withdrawn from service. (In terms of spares, BA at the time for instance only had six sets of aircraft galleys, as aircraft went in for C checks the galley was 'robbed' to service the aircraft coming out of it's own C check). The aircraft was parked in a remote hangar, and was only visited when a component had to be 'robbed' for another Concorde, and the aircraft soon fell into disrepair, was filthy externally and became a really sad sight. Many people (not myself I might add) were adamant that G-BOAG would never fly again. However, in 1984 things had really started to improve for Concorde, with the charter business increasing and the LHR-JFK route in particular becoming a staggering success. It was decided that OAG would be returned to an airworthy condition. In 1985, with a fresh new interior, and with the new BA colour scheme, she was finally returned to service; and remained as one of the mainstays of the fleet right up to the end of Concorde services in October 2003. She now resides at the Boeing Museum of Flight in Seattle. (I have particularly fond memories of G-BOAG; in a previous post I mentioned flying through an electrical storm in late 1991 over Saudi Arabia, while returning from BKK-BAH to LHR. What I forgot to mention was the spectacle of DOZENS of fierce fires burning on the ground, towards our starboard horizon. These were Sadams oil fires, still burning in Kuwait. It made a sombre contrast to the amazing electrical spectacle right in front of us).
As far as low speed flying control activity was concerned, this was a combination of the fairly flexible outer wing sections, being buffeted by low speed turbulence (the wing tip tanks 5A & 7A also being empty), as well as some autostab inputs. This was perfectly normal, and part of the design our aircraft. However the development aircraft had even more flexible outer wing sections, which used to almost straighten up in high speed flight. However due to fatigue concerns, external lateral stiffeners were added to the underside of the wings during production of the airline aircraft. (these can be easily seen from underneath the wings, just outboard of the nacelles). Unfortunately these external stiffeners also resulted in over a one tonne fuel penalty to the production aircraft, due to increased weight, as well as higher drag in a critical part of the wing aerodynamic surface.
Dude
Last edited by M2dude; 3rd Sep 2010 at 00:07 .