May 19, 201214 yr Kevin, if you care to re-read my post above, you'll read again that, on the same Airbus depending on the mode, an action on the stick will either : a- set directly the load factor or b- merely set the stabilator and of course, change angle of attack and load factor as a consequence (but this time, the load factor is not the controlled variable - or feedback - in the control loop). Granted, in both cases, one can argue that the controlled device is the same (ie the horizontal stabilizer) and that (fortunately) the final result is similar (ie : the plane goes where the pilot wants it to go) but, please understand my point that the control logic between stick action and plane reaction (ie the way the plane is piloted) is different. End of discussion ? Bruno You're missing the forest for the trees. The particular trees maybe of a different species, but it is still a forest. Actioning the stick whether in an Airbus or a Cessna is for the purpose of pitching the plane's nose up or down. Pitching the nose up or down is what you do to control the plane's angle of attack, and thusly, your airspeed. That's all I wanted my students to understand. Whether the movement of the tail surfaces is linearly connected to the actual movement of the stick mechanically or electronically intervened with to provide some kind of pitching rate to be measured in terms of angular movment or G-loading or marbles in a jar, is irrelevant to the point of understanding what a movement of pitch attitude does for the pilot...that is it results in a change of airspeed.
May 19, 201214 yr All you're bickering has just inspired a Eurika moment in me. Being honest, this lark about "Sidestick controls G-loads" really doesn't mean all that much to me in that it's implications don't seem that great, it's something that I get to spew up in my rating renewal and in the sim. All it means to me, is that the aircraft handles the same at low altitudes as it does in the cruise at high speeds, and there in lies the rub. "The aircraft handles the same at low altitudes as it does in the cruise at high speed" Read that sentence over and then get back to me on what you make of it, it's only occurred to me right now as to how serious the implications of this statement are, but I'll give yee some time to think it over before I give yee a little insight... Rónán. Rónán O Cadhain.
May 19, 201214 yr Eh, yeah pretty much a difference of semantics here and the same issue of pilot vs. engineer perspective. From a pilot's point of view the stick directly controls G-loading in normal law. From an engineer's point of view, there is no such thing as 'directly controlling G-load', the only thing you can control are your control surfaces, which will produce a pitch moment, which changes the angle of attack, which changes the G-loading. The pilot's point of view is better for understanding what happens when you pull on the stick, the engineer's point of view is a more accurate description of the physics that is happening. I am afraid I disagree with this. Especially when you state that :" From an engineer's point of view, there is no such thing as 'directly controlling G-load" because, in fact, that's exactly what the plane's systems are designed to do in normal mode. And, although I understand what you mean when you say that engineers and pilots have a different perspective, I don't think this is an issue here. Maybe (and I may be wrong on this) the word "control" only means for your that there is an interaction : an action on the stick will result in a position change in the elevator, which will in turn result in a change in G-loading. But for the engineers who designed the Airbus, just like for the pilots who fly it, this means that, in normal law, sidestick deflection and load factor imposed on the aircraft are directly proportional, regardless of airspeed. Once the sidestick is released, there is no extra load applied (ie only 1 g) and the plane remains trimmed on the same trajectory. As there is plenty of good information available on the net, may I suggest that you do a search on the subject with word groups such as "Airbus" Boeing" "trimmed for speed" etc. and you'll find very good info on the topic. Bruno PS : Just read Rónán's comment (written while I was laboring on this). Great to see his pilot perspective. Maybe I should have written : "are directly proportional, regardless of airspeed....and altitude". Looking forward to his next comments
May 19, 201214 yr "The aircraft handles the same at low altitudes as it does in the cruise at high speed" Read that sentence over and then get back to me on what you make of it, it's only occurred to me right now as to how serious the implications of this statement are, but I'll give yee some time to think it over before I give yee a little insight... Rónán Hmmm, I don't know Rónán, maybe : changes in speed or configuration (flaps, gear, etc.) will have no effect on the flight path? Bruno (trying to guess and sticking my neck out, but I found this on the net ). PS : Do I win a jumpseat tour as a contributor to this Eureka moment of yours? Hope EIN flys to and from Paris !
May 20, 201214 yr I am afraid I disagree with this. Especially when you state that :" From an engineer's point of view, there is no such thing as 'directly controlling G-load" because, in fact, that's exactly what the plane's systems are designed to do in normal mode. And, although I understand what you mean when you say that engineers and pilots have a different perspective, I don't think this is an issue here. Maybe (and I may be wrong on this) the word "control" only means for your that there is an interaction : an action on the stick will result in a position change in the elevator, which will in turn result in a change in G-loading. But for the engineers who designed the Airbus, just like for the pilots who fly it, this means that, in normal law, sidestick deflection and load factor imposed on the aircraft are directly proportional, regardless of airspeed. Once the sidestick is released, there is no extra load applied (ie only 1 g) and the plane remains trimmed on the same trajectory. As there is plenty of good information available on the net, may I suggest that you do a search on the subject with word groups such as "Airbus" Boeing" "trimmed for speed" etc. and you'll find very good info on the topic. Bruno PS : Just read Rónán's comment (written while I was laboring on this). Great to see his pilot perspective. Maybe I should have written : "are directly proportional, regardless of airspeed....and altitude". Looking forward to his next comments I've spent quite some time thinking about how to respond and I've come to the conclusion that we're getting bogged down in hair splitting and arguing over semantics, like what we mean when we say something is 'directly controlled'. Also I'm probably being overly pedantic :). One small clarification before I leave this part of the debate alone. You said: "But for the engineers who designed the Airbus, just like for the pilots who fly it, this means that, in normal law, sidestick deflection and load factor imposed on the aircraft are directly proportional, regardless of airspeed." As an engineer I can't just assume that SS deflection and load are directly proportional, that is only true after I design a control system that ensures they are. To design such a system requires me to understand that I can only change the load factor by changing the angle of attack, which I can only (practically) change by changing the elevator deflection. I will grant that once I have designed such a system I can hand wave it and say SS deflection and load are directly proportional, as long as I realise that this is only true because of my clever system making it so, and not because there exists some kind of linkage between the SS and the load factor. As for Rónán's question I'm going to have to go with Bruno's answer, unless it's got to do with having less feel for the effects of low density? John-Alan Pascoe
May 20, 201214 yr Commercial Member All you're bickering has just inspired a Eurika moment in me. Being honest, this lark about "Sidestick controls G-loads" really doesn't mean all that much to me in that it's implications don't seem that great, it's something that I get to spew up in my rating renewal and in the sim. All it means to me, is that the aircraft handles the same at low altitudes as it does in the cruise at high speeds, and there in lies the rub. "The aircraft handles the same at low altitudes as it does in the cruise at high speed" Read that sentence over and then get back to me on what you make of it, it's only occurred to me right now as to how serious the implications of this statement are, but I'll give yee some time to think it over before I give yee a little insight... Rónán. The only issue I see is you can never get a true feel of how the aircraft handles at high altitude unless you get dumped in alternate law. And how many A3xx drivers have a chance to fly in alternate & direct law outside of there brief time in the sim, even then it is normally a landing in direct law and nothing to do with the cruise phase. Rob Prest
May 20, 201214 yr ".. I've come to the conclusion that we're getting bogged down in hair splitting and arguing over semantics.." I think the next topic might be, "How many angels can dance on the end of a pitot tube?" PS Without blocking it, of course..
May 20, 201214 yr ".. I've come to the conclusion that we're getting bogged down in hair splitting and arguing over semantics.." I think the next topic might be, "How many angels can dance on the end of a pitot tube?" PS Without blocking it, of course.. Sixty nine.
May 21, 201214 yr To add more weight to the argument that the PF of AF447 thought he was overspeeding - a report on an AF 340 'zoom' climbing from FL350 to FL380 (5700ft/min climb at one point, sounding familiar?) without the PF realising after the autopilot disconnected due to an overspeed warning and the PF pulling back on the stick: http://www.bea.aero/docspa/2011/f-zu110722/pdf/f-zu110722.pdf Also adds weight to the lack of (or bad) pilot training at AF.
May 22, 201214 yr The only issue I see is you can never get a true feel of how the aircraft handles at high altitude unless you get dumped in alternate law. And how many A3xx drivers have a chance to fly in alternate & direct law outside of there brief time in the sim, even then it is normally a landing in direct law and nothing to do with the cruise phase. Bingo, one of the key things that is embedded into us is that, in most cases, the aircraft will handle the same throughout most sections of the flight. Raises interesting questions don't you think. Rónán. Again, sorry for the delay, places, oceans ect... Rónán O Cadhain.
May 22, 201214 yr Rónán. Again, sorry for the delay, places, oceans ect... No need to apologise, I'd love to have that reason why! OT but do you come in and out of EGKK at all Ró? No EIN A330s come out of here, but I see a fair few A320s.
May 22, 201214 yr No need to apologise, I'd love to have that reason why! OT but do you come in and out of EGKK at all Ró? No EIN A330s come out of here, but I see a fair few A320s. On occasion, I try to avoid the London TMA like the plague, though I have been assigned to the London route's for part of the Olympics, we're putting a couple of 330's onto the routes, along with bumping our 320's up to 321's. Joy of joy's.... Not sure yet if it'll be LHR or LGW yet though, but either way I'm not in the slightest impressed with the set-up. I need to get me some seniority... Also bear in mind we have a base at LGW, so they do some of the rotations to DUB AFAIK.... Rónán. Rónán O Cadhain.
May 22, 201214 yr On occasion, I try to avoid the London TMA like the plague, though I have been assigned to the London route's for part of the Olympics, we're putting a couple of 330's onto the routes, along with bumping our 320's up to 321's. Joy of joy's.... Not sure yet if it'll be LHR or LGW yet though, but either way I'm not in the slightest impressed with the set-up. I need to get me some seniority... Also bear in mind we have a base at LGW, so they do some of the rotations to DUB AFAIK.... Rónán. Well next time you come into LGW on 26L, keep an eye out (if you get the chance of course!) for a group of office buildings just on the western side of the M23 - pretty easy to spot because they're the last bit still surrounded by fields and are a mix of an old large period house with 2 storey modern glass on the side. The glass bits have a big '5' and '6' on them facing you as you come over. I work in number 5! http://maps.google.co.uk/maps?hl=en&ll=51.154523,-0.13745&spn=0.001206,0.002749&t=h&z=19
May 22, 201214 yr Well next time you come into LGW on 26L, keep an eye out (if you get the chance of course!) for a group of office buildings just on the western side of the M23 - pretty easy to spot because they're the last bit still surrounded by fields and are a mix of an old large period house with 2 storey modern glass on the side. The glass bits have a big '5' and '6' on them facing you as you come over. I work in number 5! http://maps.google.c...002749&t=h&z=19 Will do, If the F/O is flying I'll flash the nose gear at you, deal? Rónán. Rónán O Cadhain.
May 22, 201214 yr Will do, If the F/O is flying I'll flash the nose gear at you, deal? Rónán. If you're serious, then hell yes! Let me know nearer the time and I'll make sure I watch your flight on flightradar24.com and be ready and waiting
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