I hope there's no chance that any element of this software is installed on the ECUs of Airbus civil types . . 1. There is zero evidence that the fuel trim software being blamed for this accident resided in the ECU. Usually, fuel system management is handled at the aircraft system level, not at the engine level, so it would seem unlikely this function resided in the ECU. 2. Even if the fuel trim function resides in the ECU, the A400 uses an engine used by no other aircraft, civil or military. So it would seem extremely unlikely that other types of aircraft would be affected. |
"If the aircraft had been higher, the outcome may have been different." A statement that is applicable to practically every aircraft that has ever crashed. |
Thanks for that Wolf, I was recently discussing this A-400 incident with a current HH-60 pilot and he said the same thing- they were comforted to know that they could mash the levers forward and bypass the electronics/FADEC if need be- a mechanical bypass. Likely part of the legacy inherited from the original post-Vietnam battlefield helicopter requirements. A FADEC is exactly that: "Full Authority Digital Engine Control". Fuel to the engine is entirely metered/controlled by a digital computer. This function resides in an electronic box often called an ECU, which often has many other functions besides metering/controlling fuel flow. The pilot controls thrust by providing an electronic input to the ECU, which then varies the fuel flow to deliver the thrust demanded by the pilot. The T700 engine does not have a FADEC. It uses a hydromechanical fuel control system (HMU). The HMU uses many mechanical and analog inputs to meter/control the amount of fuel going into the engine. One of the inputs to the HMU is an electronic unit which provides much finer fuel control and also adds many protections and other features. The PCL can be used to lockout the electronic inputs to the HMU, but the PCL does NOT give the pilot control of engine fuel flow. It only gives the pilots the ability to eliminate the electronic inputs to the HMU. The PCL is NOT a "mechanical bypass" to give the pilot mechanical control of engine fuel flow. Keep in mind that helo engines are designed to maintain 100% RPM at all times. In a helo the pilot does not change thrust by changing RPM. He changes thrust by changing collective on the rotor system. So the pilot NEVER controls throttle/fuel flow to the engine. He can only control (via the collective) the load put into the engine/drive system and the HMU then controls fuel flow to maintain RPM. There is no link (either mechanical or electrical) between the pilot and the HMU for him to directly control engine fuel flow. |
Keep in mind that helo engines are designed to maintain 100% RPM at all times. In a helo the pilot does not change thrust by changing RPM. He changes thrust by changing collective on the rotor system However So the pilot NEVER controls throttle/fuel flow to the engine. I mention this just so that tryos do not get confused into thinking the helo world has always been like it is today. |
So the pilot NEVER controls throttle/fuel flow to the engine. Thread creep I know, but there really is too much aggression/sarcasm on the pages of contributions to this thread. Tragic as this accident was, I don't see why this particular fatal accident is worthy of any special consideration over other fatal aviation accidents discussed here on PPRuNe. Am I missing something here?? |
I cannot agree with that. With all for helicopters I flew in the 60s I had to control the RPM at around max by using a twist grip throttle in the end of the collective. As the years have gone by pilots have been assisted in this difficult task (initially) by suitable mechanical links that adjusted the throttle (roughly) as the collective was moved and latterly by FBW systems which of course free the pilot of the task. How many of the older types are still in operation I do not know, but I am sure there are some. |
Not always so on modern helos either. Many have a system where a collective input does directly modify the fuel flow in order to anticipate the inevitable small change in rotor RPM that will inevitably follow. |
Plus of course many helicopters such as the seaking still have a manual throttle option if the automated system is acting up where you do in fact control the fuel flow.
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Am I missing something here?? Notwithstanding the parallel discussion concerning helicopters, the only salient points we currently have about the A400M accident are: 1. The aircraft suffered a fatal accident. 2. Media reports hint at unofficial industry sources which allude to the loss of thrust from 3 or more engines at low level during the intial climb. 3. The reason for this rumoured loss of thrust has yet to be officially identified. 4. FDR and CVR analysis is ongoing. As for this specific thread, there has been a clear policy of dissuading every fruitcake and MSFS-geek from the level of wild speculation which so often contaminates the Rumours and News forum. But I think it's fairly safe to assume that no extraterrestrials were involved......:\ |
1. The aircraft suffered a fatal accident. 2. Media reports hint at unofficial industry sources which allude to the loss of thrust from 3 or more engines at low level during the intial climb. 3. The reason for this rumoured loss of thrust has yet to be officially identified. 4. FDR and CVR analysis is ongoing. 3. The reason for this rumoured loss of thrust has yet to be officially identified, but the same rumor sources claim it was due to a fuel tank trimming system unique to this specific aircraft and not previous installed on A400s. It is this last item that started the discussion on FADEC and ECUs, which are likely not involved in a fuel tank trimming system anyway. |
BEags, very well said. I stand by you on this one.
The vultures and armchair experts always turn up at such times.
Originally Posted by H Peacock
Tragic as this accident was, I don't see why this particular fatal accident is worthy of any special consideration over other fatal aviation accidents discussed here on PPRuNe. Am I missing something here??
Not "special consideration". The consideration we should give to all such incidents. Edit: sorry, HPeacock, I did not mean to imply that you are one of those that come here to speculate. I was addressing two issues in one post and failed to separate the two. |
Tank trimming?
What is the benefit of tank trimming, and how would this expand the maneuver envelope at takeoff versus any other normal mode of flight? Have read several of the articles, but drawing a big question mark on this one.
Resorting back to fixed wing aero, you'd like the Cg to be near CL as I recall- thus alleviating any control or flying qualities issues... It appears I need a class in how this functions as a benefit- other than doing exactly the above...which I'd assume in a production aircraft you'd thus be at a full or ideal load anyway, and not likely require shifting at takeoff? |
I've been wondering why an aircraft would need tactical manoeuvering immediately after take off, then thought about MANPAD etc, so presumably that's why.
What I don't understand is - when an aircraft this large manoeuvers, are they not likely to be positive g rather than negative? So I am at a loss to work out what fuel tank trimming actually means in this context. Does this cause trimming of thrust to assist the aerodynamics? Care to enlighten me anyone? |
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Fuel Trim
Unlike some Airbus types, the A400M does not feature "fuel tank trimming". There is no trim tank in the tail. Neither is fuel pumped laterally (except, if required, under manual pilot control to correct a fuel imbalance). The fuel's path from tank to engine is untroubled by any software. The Wikipedia and Aviation Week articles are a load of bull.
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Thanks - so it's "simply" a means of altering C of G. For some reason I thought it meant lateral trimming - which blew my mind.
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Brian, no, there is no fuel CG trimming on A400M: neither longitudinal nor lateral. Apologies if my previous post was unclear.
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Am I safe to ask: is there any news (good, preferrably) on the recovery of the survivors yet?
CG |
SyEng, have any A400M been flown with the additional Cargo Bay Tanks intended for the AAR role? Fuel from the CBTs will need to be pumped to the 'AAR gallery', although I cannot recall how the associated schedule is managed.
If 'AAR' software is enabled and the fuel system is 'expecting' to transfer fuel from CBTs which aren't actually fitted.......:confused: And no, I have absolutely no idea whether the AAR software has yet been included in any A400M. |
CG:
Both still recovering in hospital, the most seriously injured guy is, thankfully, out of intensive care. Beagle: No, the CBTs and the centreline HDU stuff is yet to be trialled. My understanding of the Tactical fuel management is that it schedules the fuel in such a way that it minimises stress/fatigue due to the more dynamic manoeuvring required for the tactical role, up to +3G. |
Good! Thanks for taking the trouble to respond. They are in my thoughts.
CG |
My understanding of the Tactical fuel management is that it schedules the fuel in such a way that it minimises stress/fatigue due to the more dynamic manoeuvring required for the tactical role, up to +3G. |
KenV
Yes, that is my understanding of the system. It is, in effect, an autonomous 'wing relieving' system specifically for the tactical role.
If you look at any of the A400M display videos out there, the penultimate manoeuvre before the 120 degree wing-over at the conclusion of the display is a 3G pull-up. |
Thanks, TT, that's what I thought.
The term 'trimming', much as the term 'strong banking', is probably the result of poor translation by the original source. Good to hear that the 2 survivors are doing well. |
Just to be clear:
Whether MSN23 was fitted with such a system (software/hardware) is immaterial - a first-flight schedule would not be checking/testing any such capability, that would either be in subsequent flights, or - more likely - subject to specific functionality testing onboard one of the 3 development aircraft prior to being cleared for series production embodiment. |
Yes, that is my understanding of the system. It is, in effect, an autonomous 'wing relieving' system specifically for the tactical role. If you look at any of the A400M display videos out there, the penultimate manoeuvre before the 120 degree wing-over at the conclusion of the display is a 3G pull-up. |
Wrong Tree, Barking
In common with most large aircraft, by design the A400M fuel system keeps as much fuel as far outboard as possible all the time for wing bending moment relief. As fuel is used from the feed tanks, they are topped up from the centre and transfer tanks in that order. (There is a slight modification to this in a tactical fuel loading mode which I won't describe here - but that's not important right now.)
The aircraft fuel system does not take orders from the engine ECUs. If there is a parameter labelled "trim" or "fuel trim" in the ECU data, it relates to engine fuel control, not the aircraft fuel system. |
Ah, yes, KenV. Let's see, now. You're in Texas and you clearly think the Boeing product has the better answer over the European thing. Hmmm. Help me out here. :cool:
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Whether MSN23 was fitted with such a system (software/hardware) is immaterial - a first-flight schedule would not be checking/testing any such capability, that would either be in subsequent flights, or - more likely - subject to specific functionality testing onboard one of the 3 development aircraft prior to being cleared for series production embodiment. |
Ah, yes, KenV. Let's see, now. You're in Texas and you clearly think the Boeing product has the better answer over the European thing. Douglas is well known for their conservative design philosophy. Some say that philosophy is "better". Clearly in the market place it is NOT "better", because except for the C-17 the entire Douglas production line no longer exists. And the C-17 line will cease to exist in a few weeks. Is that "better"? Probably not. Certainly not for the folks in Long Beach, California. |
In common with most large aircraft, by design the A400M fuel system keeps as much fuel as far outboard as possible all the time for wing bending moment relief. As fuel is used from the feed tanks, they are topped up from the centre and transfer tanks in that order. (There is a slight modification to this in a tactical fuel loading mode which I won't describe here - but that's not important right now.) |
I was writing tongue-in-cheek, KenV. Sorry, maybe a subject close to your heart.
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Sorry, missed the tongue-in-cheek. My bad.
But in my defense, this is not the first time where I asked a question about an Airbus product and others assumed I was knocking Airbus. Douglas had a long and proud history and having lost to Boeing, I'm very familiar with the notion that "different" is not necessarily "better". (or for that matter, worse.) But having experienced the Boeing vs Douglas difference first hand, I like to understand the Boeing vs Airbus difference. |
I get that, Ken. :ok:
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Any reports if data was retrieved from the flight recorders? Seems there were early reports of technical issues extracting the data and the boxes went from Spain, to France and then perhaps to the US manufacturer.
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Airbus CEO Says A400M Black Box Data Recovered
From the Wall Street Journal:
Airbus CEO Says A400M Black Box Data Recovered By Robert Wall May 27, 2015 12:26 p.m. ET Airbus Group Chief Executive Tom Enders said data from the black boxes on the A400M military transport plane that crashed this month in Spain has been extracted, though Spanish authorities have not yet shared the crucial information. “So far we have not had access to the data” though it has been available for more than a week, Mr. Enders told shareholders in Amsterdam. Extracting the information wasn’t simple and in one case involved sending the box to its manufacturer, L-3 Communications, in the U.S., Mr. Enders said. The May 9 crash, the first of an A400M, killed four of six Airbus employees on the plane. The other two were critically injured, though Mr. Enders said on Wednesday their condition was improving. Airbus last week alerted operators that the plane requires one-time checks of the so-called electronic control units on each of the four engines before the next flight. The electronic box helps translate pilot commands into instructions on how the engine should operate. Airbus also instructed operators to perform additional checks in case of later engine problems. Airbus said it found the issue, seen as a flaw in the system’s software, during its own analysis of what may have caused the crash. Mr. Enders said Airbus wants access to the black box data, which stores conversations in the cockpit and, more critically, a large number of system parameters, to validate whether its hypothesis about the crash is accurate. The U.K., Germany, Turkey and Malaysia grounded their transport planes after the crash, although France continued using the aircraft. Spanish authorities also told Airbus to stop flying newly built planes for the time being. Mr. Enders said the data from the black boxes is crucial to determining exactly what caused the accident, take corrective action and gain clearance for the planes to start flying again more widely. Mr. Enders said the crash would have an impact on the program, which was already behind schedule. He said he’s optimistic the accident “will not have a very detrimental impact on the aircraft deliveries and the cost situation in 2015. The A400M program is several billion dollars over cost after repeated delays during its development. The program is unprofitable over the 174 aircraft already ordered, with pressure on Airbus to win additional deals to make money with the aircraft. Airbus in January made management changes to the program and since then ”the situation is markedly improved,” Mr. Enders said. |
Marwan Lahoud (Airbus strategy director) is quoted in tomorrow's edition of the german newspaper Handelsblatt.
Crash de l?A400M*: Airbus reconnaît des problèmes de qualité dans l?assemblage and Crash A400M: "Un sérieux problème de qualité dans l'assemblage final" - RTBF Economie Les boîtes noires le confirment. Il n'y pas de défaut structurel, mais nous avons un sérieux problème de qualité dans l'assemblage final. Nous avons pris connaissance pour la première fois hier (mercredi) des résultats, ils confirment nos analyses internes |
Anyone have an idea what was the issue with the data recorders ? Given the crash circumstances it would seems that they should have been recovered in a fairly decent shape and these must be state of the art. I'm a little puzzled by this.
As for the crash being down to quality control in assembly... wow ! That would quite unbelievable given the context. I just can't imagine Airbus having such a huge issue in QA - muss be more to the story. |
I know some of you here knew the crew, I am not trying to attribute blame, just mentioning what is in the public domain.
LES ECHOS, saying the crash could have been human error. Rough translation here: The control software of the engines has been poorly installed just prior to the flight of the aircraft. A400M, airplane cursed ? The track of a human error at Airbus is confirmed in the fatal accident of May 9 last year in Seville, said of corroborating sources. Specifically, it would seem that the control software of the power of the four motors - turboprop - has been downloaded incorrectly during the phase of so-called "pre-flight ", i.e. the phase which separates the output of the device of the assembly line for its first flight. " IS sure to 99 % ", says a source close to the folder. On 9 May last, the A400M MSN23 - that is to say, the 23e series - crashed some time after taking off for its first flight. Three of the four engines have suddenly lost power. The accident has cost the lives of four of the six persons on board. The appliance was the third to be delivered to Turkey. The black boxes have been found but the specialized unit of the Spanish Ministry of Defense in charge of the investigation has made no comment since. 5 Billion of additional costs if the track to a procedural error is confirmed, the design of engines, very complex, is therefore not in issue. " They are the consequence, not the cause of the crash ", is it estimated to source close. Manufactured by EPI, a consortium consisting of the British Rolls-Royce , the French Snecma (Safran group), the Spanish ITP and the German MTU, the engines are at the origin of the previous setbacks of the program who have already cost 5 billion of extra cost to Airbus. Marwan Lahoud, the responsible for the strategy and marketing of Airbus Group, goes in this direction. " Black boxes the confirm. There is no structural defect. But we have a serious problem of quality in the final assembly ", he says in an interview to " Handelsblatt " to be issued on Friday. Last May 19, Airbus had recommended to its clients to regularly inspect the ECU, the engine electronic control unit, before the flight and perform additional checks after a possible replacement of engine or the ECU. But without establishing a link with the crash. At this point, Germany, Great Britain, Turkey and Malaysia have suspended the flights of their A400M. France, she, the continues but only for the operational emergencies. In total, 174 A400M have been ordered by eight countries. Twelve only are in service. Independently of the crash, the program suffers from new delays. The dropping of paratroopers had major problems, and in-flight refueling of helicopters will not see the day, according to the DGA. All these problems have forced Airbus a go a load of EUR 551 million in its accounts 2014 ( " Echoes " of 2 March). |
Rolling20, it looks like you've become a victim of Google Translate.
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