Originally posted by BoeingBobby
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Originally posted by BoeingBobby View PostAnd Gabriel, More often than not in the 747 we take off with more fuel than we can land with. That is what fuel dump systems and overweight landings are for.
Did I say something that sounded like contrary to that?
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--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostI know, and it is not just in the 747. Virtually all planes bigger than a small GA one have a MTOW that is heavier than its MLW, even planes that do not have fuel dump systems (which is most of the single aisle airliners, and hence most of the commercial airplanes today). But they are all certified to land with more than the MLW, up to the MTOW (a special post-heavy-landing inspection may apply, though).
Did I say something that sounded like contrary to that?
This kind of sounded like you did not understand that, but I see you do.
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Originally posted by BoeingBobby View Post"On a more serious note, there are other instances where you may have too much fuel like a double engine failure in a 3 or 4 engines plane. This is more a weight than a fuel issue, but fuel is easier to dump than pax or cargo!"
This kind of sounded like you did not understand that, but I see you do.
§ 121.193 Airplanes: Turbine engine powered: En route limitations: Two engines inoperative.
(c) [...] No person may operate a turbine engine powered airplane along an intended route unless [...]:
(2) Its weight, according to the two-engine inoperative, en route, net flight path data in the Airplane Flight Manual, allows the airplane to fly from the point where the two engines are assumed to fail simultaneously to an airport [...], with the net flight path (considering the ambient temperatures anticipated along the track) clearing vertically by at least 2,000 feet all terrain and obstructions within five statute miles (4.34 nautical miles) on each side of the intended track [and] The net flight path has a positive slope at 1,500 feet above the airport where the landing is assumed to be made after the engines fail.
And this is considering the option of fuel dump (if available). So the scenario is that it is perfectly legal that you lose 2 engines and, while descending towards an airport, you start dumping fuel but even then you are able to hold the altitude with the other 1 or 2 engines at MCT when you go all the way down to 1501 ft above the diversion airport, and that is with the airplane in clean config and with the wings level. Gear down, flaps 1 or turn, and you may be unable to hold the altitude.
At that point, you may be wishing you were lighter (read: that you had not put so much fuel way beyond the required amount).
(to be fair, the net flight path has a margin of 0.3% to 0.5% gradient over the flight path gradient demonstrated in the test flights)
(to be fair II, the chances of that happening are extremely slim. How many times did 2 (but not all) engines fail?)
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostOk, let me clarify what I meant (and this addresses Evan's "uh oh")
§ 121.193 Airplanes: Turbine engine powered: En route limitations: Two engines inoperative.
Maybe it is here:
§25.473 Landing load conditions and assumptions.
(a) For the landing conditions specified in §25.479 to §25.485 the airplane is assumed to contact the ground—
(1) In the attitudes defined in §25.479 and §25.481;
(2) With a limit descent velocity of 10 fps at the design landing weight (the maximum weight for landing conditions at maximum descent velocity); and
(3) With a limit descent velocity of 6 fps at the design take-off weight (the maximum weight for landing conditions at a reduced descent velocity).
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Originally posted by Evan View PostI sort of recall you taking us on a Gabrielesque journey down the path of 'a transport category aircraft must always be able to land safely at MTOW'
Maybe it is here:
§25.473 Landing load conditions and assumptions.
(a) For the landing conditions specified in §25.479 to §25.485 the airplane is assumed to contact the ground—
(1) In the attitudes defined in §25.479 and §25.481;
(2) With a limit descent velocity of 10 fps at the design landing weight (the maximum weight for landing conditions at maximum descent velocity); and
(3) With a limit descent velocity of 6 fps at the design take-off weight (the maximum weight for landing conditions at a reduced descent velocity).
Anyway, this is completely OT and inconsequential. It was intended to be just a joke about BB's comment that you cannot have too much fuel except in a fire.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Happy hump day everyone. I've few questions - with the caveat again I'm an 'enthusiast' only not a pilot or expert of any sort hence what might be deemed 'stupid' questions...
First, how in an a/c like this is fuel status known - i.e. what is the 'fuel gauge' (a dial? a weight readout?). And how precise is the 'gauge' whatever its form? By analogy, I once owned a Ford Mustang 5.0. Despite being a gas gobbler, the gauge could go to "E" and I knew I had at least a good 50 miles left - and the needle would be very visibly 'below E' when it was really empty. And several other cars we owned were largely the same though the Mustang was the clear leader vis a vis untrue 'E'. Well my next car was a Jetta, being in city and wanting a better gas cost. Well not long after buying it, I was tootling around town and it the needle was on 'E' and I said to myself 'meh, I'll get gas tomorrow' as could easily be done on the Mustang. Well, when Germans say 'E' I learned they MEAN E....because not 10 minutes later whiles going thru an intersection it died on me - saved only by the sheer luck a gas station was on the corner and I coasted into the pump and filled up. So, are aircraft fuel 'gauges' more like my Mustang or the Jetta?
Second, and pardon my ignorance I just havent really 'grasped' it yet despite trying...when the captain (and others) say 'give me vectors for the runway (airport)' what is s/he meaning, I know what a vector is vis a vis math/geometry/medicine etc. but what info (number?) is being asked for and how does s/he use it? I ask because (and oh god I know this sounds idiotic) but doesn't the captain know where the airport is / have GPS etc.
Anyway RIP to those lost. Though seemingly the captains fault here for fuel (mis)mismanagement, and failure to declare emergency/notify ATC etc., nonetheless reading the communication b/w him and ATC and 'hearing' (such as it is) the very very quick change from 'anxious inquiries' to 'frantic despair' is really wrenching...I can almost sense in 'his voice' (again written not heard) the very quick realization that he winged it, and it didnt work out this time, and he'd really really effed up bigtime and was in a world of trouble. That's not in any way to lessen his responsibility or be 'soft' on him, it's just saying I sense that realization and its wrenching nature when I read it.
Anyway thanks for all these great comments the information as always is terribly helpful to us non-experts/pilots.
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Originally posted by obmot View PostHappy hump day everyone. I've few questions - with the caveat again I'm an 'enthusiast' only not a pilot or expert of any sort hence what might be deemed 'stupid' questions...
First, how in an a/c like this is fuel status known - i.e. what is the 'fuel gauge' (a dial? a weight readout?). And how precise is the 'gauge' whatever its form? By analogy, I once owned a Ford Mustang 5.0. Despite being a gas gobbler, the gauge could go to "E" and I knew I had at least a good 50 miles left - and the needle would be very visibly 'below E' when it was really empty. And several other cars we owned were largely the same though the Mustang was the clear leader vis a vis untrue 'E'. Well my next car was a Jetta, being in city and wanting a better gas cost. Well not long after buying it, I was tootling around town and it the needle was on 'E' and I said to myself 'meh, I'll get gas tomorrow' as could easily be done on the Mustang. Well, when Germans say 'E' I learned they MEAN E....because not 10 minutes later whiles going thru an intersection it died on me - saved only by the sheer luck a gas station was on the corner and I coasted into the pump and filled up. So, are aircraft fuel 'gauges' more like my Mustang or the Jetta?
Second, and pardon my ignorance I just havent really 'grasped' it yet despite trying...when the captain (and others) say 'give me vectors for the runway (airport)' what is s/he meaning, I know what a vector is vis a vis math/geometry/medicine etc. but what info (number?) is being asked for and how does s/he use it? I ask because (and oh god I know this sounds idiotic) but doesn't the captain know where the airport is / have GPS etc.
Anyway RIP to those lost. Though seemingly the captains fault here for fuel (mis)mismanagement, and failure to declare emergency/notify ATC etc., nonetheless reading the communication b/w him and ATC and 'hearing' (such as it is) the very very quick change from 'anxious inquiries' to 'frantic despair' is really wrenching...I can almost sense in 'his voice' (again written not heard) the very quick realization that he winged it, and it didnt work out this time, and he'd really really effed up bigtime and was in a world of trouble. That's not in any way to lessen his responsibility or be 'soft' on him, it's just saying I sense that realization and its wrenching nature when I read it.
Anyway thanks for all these great comments the information as always is terribly helpful to us non-experts/pilots.
ANother example: the A320 that caused the LAMIA flight to go into a holding pattern apparently had a bad fuel reading. The crew took it seriously, declared emergency and landed ASAP. Turned out they had no fuel leak, just a bad reading. But that's how it's done.
Vectors are just instructions from ATC guiding you (vectoring you) along the appraoch, ex: "turn left heading 350, maintain 2,000 feet", as opposed to using internal navigation. The vectors on the ATC recording here didn't seem righ to me, but in any case, when she heard the altitude, without power, she must have known they were done for.
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Originally posted by Evan View PostI uh-ohed BoeingBobby for this one...
Can't a fully fueled 747 at MTOW always land safely at a reduced vertical speed?
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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From today's AIAA newsletter:
Bolivian Defense Minister: Owners Of Crashed Jet Left Trail Of Unpaid Debts.
The AP (12/5) reports that Bolivian Defense Minister Reymi Ferreira said Monday that LaMia airlines – owners of the jet involved in last week’s crash – refused to pay hangar fees, which “forced Bolivia’s air force to seize two planes and briefly jail one of the company’s” executives. The AP reports that the airline has been suspended due to its involvement in last week’s crash and its “trail of unpaid bills.” The AP adds that, according to Ferreira, the “aviation officials who signed off on” the LaMia jet’s “irregular flight plan would be prosecuted.”
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Originally posted by BoeingBobby View PostHowever, It come with a very expensive overweight landing inspection. Unless you were to have an AIRFRAME fire, it is not advisable.
Not arguing against fuel dumping, just wondering what the actual economics are.
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Originally posted by Evan View PostOut of curiousity, how expensive is that inspection? I figure if you get off the runway at 875,000lb MTOW and need to dump 222,500lbs to get to MLW, you are dumping $45,000-60,000 of fuel (depending on the price of fuel), not to mention the fuel you are burning off while doing it. I'm assuming the a/c will be out of service anyway for the reason that caused you to return (i.e. an engine swap. etc.). And of course, I'm assuming that the overweight landing didn't itself cause any expensive repairs.
Not arguing against fuel dumping, just wondering what the actual economics are.
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