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We're not going anywhere in our airliner without fuel - lots of it. Until someone builds a practical electric aircraft, probably quite a few years down the road, we have to burn hydrocarbons to make this thing go.

So let's take a look at what we're burning and how we get it to the engines.

In the airlines we mostly burn what is called Jet A. It's essentially kerosene with various chemicals added to help prevent ice buildup, prevent corrosion and to keep it from gumming up the fuel system.

There are some other types of jet fuels, mostly used by the military:

Jet A-1 is very similar to Jet A but can handle colder temperatures.

Jet B is a naphtha based fuel used in very cold climates.

JP-4 was a mixture of kerosene and gasoline. The Air Force used this stuff for years. It had a very low flash point, meaning it was very explodey. Glad they don't use it any more.

JP-5 is used by the Navy. Has a relatively high flash point. This is very important because fire on a ship is your worst nightmare.

JP-7 was used by the SR-71. It had a very high flash point because of the very high temperatures encountered at Mach 3. No longer in use.

JP-8 This is what the Air Force switched to after getting rid of JP-4. This stuff is essentially the same as Jet A.

So what's it cost? It's a commodity and the price fluctuates from day to day and location to location. As of today the spot price was $2.80/gallon.

We purchase fuel by the gallon but what we really care about is how much it weighs. Jet A weighs roughly 6.7 pounds per gallon. That adds up quick. For every hour of flight in a 757 we'll need roughly 8000 pounds or a bit over 1000 gallons. If we're going a long way, by the time we add in fuel to get to an alternate plus reserves we might be carrying 50,000 pounds of fuel.

That's why we don't carry a bunch of extra gas around. We'd be heavier and have to burn even more fuel just to carry the extra fuel. We carry enough to get from Point A to Point B, and maybe Point C if the weather is bad at Point B - plus 45 minutes of reserve. That was a big adjustment after flying Air Force tankers that usually had enough gas to divert anywhere in the lower 48.

The fuel tanks are normally in the wings and the lower fuselage. For example, the 757 has a fairly simple fuel system with a single tank in each wing plus a center tank between the wings.

757 Fuel Tanks
Structurally it's better to keep the fuel in the wings as the weight is then distributed across the wings rather than concentrated in one spot. When we have fuel put on the plane we normally fill the wing tanks before we put any fuel in the center tank. In flight we do the reverse, burning the center tank down to empty before we burn the wing tanks.

Once the fuel gets to the engine it passes through a filter and then through a fuel-oil heat exchanger. The fuel keeps the engines oil cool and the oil warms up the fuel. The fuel then goes through an engine-driven fuel pump and into the fuel control unit (like your car's fuel injection).

Larger aircraft may have a few more fuel tanks. Let's look at an Airbus A300. Not the best picture I realize.

A300 Fuel System
The A300 has two fuel tanks in each wing, inner and outer. Like the 757, it has a center tank in the fuselage, but then it also has what's called a trim tank back in the tail. At altitude the fuel system will automatically pump fuel from the center tank back to the trim tank to give the plane an aft Center of Gravity (for better fuel economy). On descent the fuel will be pumped back to the center tank.

Most airliners are normally refueled from a central point. On a 757 there's a refueling panel on the underside of the right wing. A tanker truck will hook up there and put the specified fuel quantity in the desired tanks. During our pre-flight we make sure that the proper amount of fuel was pumped into the correct tanks. That's obviously not something we leave to chance. Otherwise you could end up like these guys:

Air Canada Flight 143 (Gimli Glider)

From the cockpit this is what we see. This shows a 757-200 with full tanks, 14,600 pounds in each wing plus 46,200 pounds in the center tank. It also shows the temperature of the fuel, which can become important on long flights at high altitude where the temperatures are very cold.

757 Fuel Indicators
75,000 pounds would let us fly a lot longer than I want to sit in the thing
We can also call up a digital readout of how much each engine has used once its been started. We can use this as a backup in case a fuel gauge malfunctions or to check for a leak. The computer will show us an estimated fuel quantity based on fuel at start minus fuel burned.

So let's take a look at the fuel control panel. Like everything else on the 757 it's pretty simple and almost pilot proof.

757 Fuel Controls
Each wing tank has two AC powered boost pumps. These provide fuel under positive pressure to the engines. The left wing tank normally supplies the left engine and the right tank supplies the right engine.

If we have fuel in the center tank, we turn its pumps on as well. The center tank pumps are called override pumps because they put out more pressure than the boost pumps. The center tank fuel will push its way to the "front of the line" and get burned before the wing tanks.

This way there is always positive fuel pressure. Once the center tank runs dry the pumps will shut off automatically but since the wing tanks are still pumping the engines (and pilots) stay happy.

Normally our fuel panel should look something like this. No lights illuminated means all is well. Mister Boeing likes a dark cockpit.

Fuel Panel Normal Configuration
Note that the "fuel config" light is out. That's a good thing. That light comes on when something in the fuel system isn't configured properly. For example one wing with a lot more fuel than the other.

The plane's computer, or FMS, also tries to keep us honest. When we program our route of flight into the computer we tell it how much fuel we want to get there with. In flight, if it thinks we're going to get there with less fuel than that it will "yell" at us with an INSUFFICIENT FUEL message.

The 757 fuel system is mostly "set it and forget it". Normally all we have to do is turn off the center tank pumps when the tank runs dry. The pumps will have actually shut themselves off automatically, we're really just repositioning the switch to keep them from cycling on and off (there might be a few gallons of fuel sloshing around the tank).

About the only action we may have to take is cross-feeding. Let's suppose one engine is burning a bit more fuel than the other. Over a long flight we'd end up with more fuel in one wing tank than the other. To fix this we can temporarily run both engines from the wing tank that has more fuel.

Cross-feeding is a very simple operation, but if you screw it up you can make matters worse by starving an engine of fuel (bad). The main thing to remember is:

ALWAYS TURN SOMETHING "ON" BEFORE YOU TURN SOMETHING "OFF".

So let's say the right wing tank has more fuel than the left and we want to fix it.

1. Open the cross-feed valve (Turn something on)
2. Turn off the boost pumps in the left wing tank (the one with less fuel)

Now the right tank pumps are feeding both engines. They're quite powerful enough to do that as long as both of them are working. If they're not both working we've got other issues to deal with.

Fuel Cross-feed
Left pumps are off
Center pumps would probably be off at this point
Now we need to do something to remind ourselves that we're cross-feeding or we could just end up creating an imbalance the other way. Some guys take a checklist and stick it between the throttles. Anything to remind yourself that something out of the ordinary is going on and you need to keep an eye on it.

Once the fuel is balanced we:

1. Turn the left boost pumps on (Always turn something on first)
2. Close the cross-feed valve (Turn something off last)

Sounds pretty simple but at 5:00 AM at the end of a long shift there aren't a whole lot of extra brain cells to go around. At that point I'm down to "Mongo turn something on before Mongo turn something off".

OK, the 757 fuel panel is pretty simple. Let's take a look at something a little fancier like the Airbus A300. It's got a few more bells and whistles but it's also fairly automatic. If everything is working properly it takes care of itself.

A300 Fuel Panel
Now the cool thing that Airbus did is they gave us a couple extra screens in the cockpit where we could pull of detailed graphics of what each system was doing.

The Boeing philosophy, at least on the 757, seems to have been "You don't need to know that. Just turn it on and if a light comes on go to the checklist."

A300 Fuel Display
What this is showing us is each engine being fed by its outer wing tank and the center tank. The little circles with lines through them represent the fuel valves. The squares with lines through them represent fuel pumps. If the graphics look like something from a 1980s arcade game, well that's about how old this thing is. I sometimes felt like I should be feeding quarters into it.

The A300 fuel system worked pretty well most of the time. Occasionally one of the 1970s vintage mechanical relays would stick but it wasn't a big deal normally.

Want to see something really scary? Here's the 727 fuel panel.

727 Fuel Panel
Want to know how much total fuel you have? Do the the math. You have to add up the 3 tanks. Hey, at 4:00 AM math is hard.

I haven't talked about fuel dumping yet. Some planes are capable of dumping fuel in an emergency to lighten the load. The A300 didn't have fuel dump capability and neither does the 757-200. They don't need it. They have plenty of thrust on one engine and can be landed at their maximum weight if need be.

The 727 could dump fuel, and if you lost two engines you would be dumping gas in a hurry because it didn't fly very well on one engine.

727 Fuel Dump Panel
To dump fuel you'd open the dump valves and the nozzles. The boost pumps would push the fuel out the dump nozzles, which were on the wing tips. I forget how fast we could dump but it went pretty quick.

Now you might be wondering about the environment impact. At high altitude, it will dissipate in the air and unburned hydrocarbons are not as bad as burned hydrocarbons.

At low altitude, well what can I say. It's better for the planet than crashing a 727 into it.

So what can go wrong with the fuel system?

A leak of course. We'll know we have a leak when we see one tank noticeably lower or when our fuel usage noticeably exceeds what we expected to use. On long flights we make a point of checking actual fuel vs the flight plan at least once per hour. If we detect a leak we're going to land.

Losing a boost pump is no big deal. We've got two in each tank and one is sufficient. If you've learned anything by now it's that we like redundancy. Lose both? Still not a problem. We can cross-feed from the other wing and keep the engine happy.

Lose all the boost pumps? Yeah, could happen if we lost all the generators (the boost pumps run on AC). The engines should still be able to suction feed with the engine-driven fuel pumps. We may have to slow down or go down to keep the engines happy but they should keep running. That's one advantage to having the engines mounted on pods below the wing - gravity is helping get that fuel to the engine.

Another possible problem is a stuck valve. Not much of a problem on the 757 with its simplistic fuel system. On a bigger plane with more fuel tanks it's possible you could end up with "trapped fuel" - you've got fuel in a tank but you can't get at it because the valve won't open. Not something I'd want to learn halfway across the Pacific. That's why when flying KC-135s I always made sure all the tanks would feed prior to heading out over the water.

Fuel Economy

Of course we all want to save fuel these days. Fuel is a major expense for an airline. We try to fly at our most efficient speed and altitude. We try to fly the most direct route to where we're going. We don't carry as much extra fuel as we used to in order to save weight. We'll even taxi with just one engine running and start the other one just before takeoff.

So how energy efficient are jets anyway? Turns out they're not too bad if used properly. This will take a little math, so bear with me here.

Let's suppose you're going to take a 400 mile trip in your SUV that gets 15 mpg. If you're the only person in the vehicle you're getting 15 passenger-miles to the gallon.

OK, let's look at the 757. On a 400 mile flight it will burn 8000 pounds of fuel, at 6.75 pounds per gallon that's 1185 gallons. This works out to .3375 miles per gallon. Not very good. Obviously a lot worse even than your Ford Canyonero.

Ah, but we can cram 239 people into the 757 (and believe me they'll cram them in today). This gives us 80 passenger-miles to the gallon. So the guy driving 400 miles by himself in the SUV would actually do a lot better fuel wise by getting on a jet.

Of course I'm cheating a bit here. I'm giving the jet a full passenger load and only partly loading the car. But when did you last get on a jet that wasn't fully loaded? I'd wager sometime around 1983.

Now if our SUV driver has his wife and two kids with him, he's getting 60 (4 x 15) passenger-miles to the gallon so the jet still beats him.

Ah, but you're not one of those wasteful SUV drivers. You have a Prius. OK, let's say you get 40 highway mpg. If you're driving by yourself, the jet easily beats your 40 passenger-miles to the gallon. You'd have to at least take your spouse along to tie the jet and you'd need one more person to come out ahead.

Now I've ridden in a Prius (they use them as cabs up in Winnipeg). Not sure I'd want to spend 400 miles in the back seat of one. Of course, compared to the average airline seat today I'd say it's a wash.

My whole point being, on a longer trip a jet is fairly efficient if you fill it up.

So what's the future?

I don't really know. The next generation of engines (geared turbofans) will be even more efficient. They're also currently testing bio-fuels in aircraft and they seem to burn them quite happily. Don't know if we could ever produce bio-fuel in sufficient quantities but that's a whole different argument.

Electrics? I suppose you could spin the fans with electric motors but I don't know if you could get enough energy density out of batteries to go 500 mph for 500 miles. I don't see this any time in the near future. Right now anything powered by electrics is in the ultra-light to light aircraft range.

I suspect we'll be flying around burning hydrocarbons for a few more years. At least we're not flying the smoke-belching gas-guzzling turbojets of yesteryear.

I had to get one of these in here somewhere.
You really don't want to see the fuel panel on this thing.

Originally posted to Major Kong on Sun May 26, 2013 at 05:04 AM PDT.

Also republished by Kossack Air Force, Aviation & Pilots, Central Ohio Kossacks, and Community Spotlight.

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Comment Preferences

  •  Interesting! (9+ / 0-)

    Thank you.  I've always wondered how pilots can keep all those gauges in a typical cockpit straight. Several years ago I flew in a float plane in Alaska - that was about as basic as you get.  It's also interesting how capable pilots are in a crunch - the glider incident, Sully Sullenberg, etc.  Skill and presence of mind in situations that would paralyze most of us.  

  •  My personal favorite: (5+ / 0-)

    Quis custodiet ipsos custodes?

    by Bisbonian on Sun May 26, 2013 at 06:35:44 AM PDT

    •  I must have gone through (10+ / 0-)

      2 or 3 different fuel panels in the KC-135.

      I recall the steam gauge panel, and then there at least two different digital fuel panels.

      There were 10 fuel tanks on the KC-135

      2 mains plus a reserve in each wing
      Forward Body
      Center Wing
      Aft Body
      Upper Body

      The air refueling pumps were in the forward and aft body tanks. You could drain fuel from all the other tanks into those two.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 08:59:05 AM PDT

      [ Parent ]

  •  Major Kong, found a little typo you might want to (6+ / 0-)

    correct to keep this otherwise perfect series spotless, for future reference:

    The 727 could dump fuel, and if you lost two engines you would be dumping gas in a (hurry?) because it didn't fly very well on one engine.

    Quis custodiet ipsos custodes?

    by Bisbonian on Sun May 26, 2013 at 06:38:22 AM PDT

  •  excellent article - and many more on the web (5+ / 0-)

    i have not read these articles before posted by Major Kong

    i clicked on the hot link for his name to get to his home page

    there are many articles he has written on airplanes

    i am sending this article to several friends along with the instructions to get the earlier articles

    note that one has to click on the "NEXT" link at the bottom because the articles cover more than the first page

    thanks again for all the work on this!

  •  making me nervous, dude. (7+ / 0-)
    "Mongo turn something on before Mongo turn something off".
    AAAaaaagggh!!!!!!!!!!!!!

    If I ran this circus, things would be DIFFERENT!

    by CwV on Sun May 26, 2013 at 07:06:35 AM PDT

  •  Thanks for the writeup, Major. (8+ / 0-)

    Although you're being a little disingenuous with that last B52 photo. Isn't it mostly the water pumped into the engines that causes those black clouds?

    (See, I was paying attention in your earlier B52 diaries :-P )

  •  Managing fuel can be critical sometimes (13+ / 0-)

    Th3e F-15 Eagle that went down in Libya did so in part because  of a problem with an external fuel tank. Fighter jets usually have the option of carrying extra fuel in external tanks under the wings. (You'll see them on C-130s too.) This lets them fly farther between aerial refueling hookups.

    In the Libya example, there were 2 F-15s on a mission to suppress action by Gaddafi's forces against the Libyan rebels. Both ships were carrying extra fuel in tanks under the wings, external tanks right up against the fuselage, and a load of bombs, also hung under the wings. The trick is to keep fuel and bomb loads balanced.

    The F-15 that went down had troubles early on - the fuel in the right external tank wasn't feeding at first; the pilot managed to get the fuel flowing, but slowly. This meant the right wing was becoming increasingly heavier than the left wing as fuel from the tank on the left side burned off. The F-15 is normally heavier on the right wing side as it is because there's a 20mm cannon in the right side of the fuselage.

    The trouble came when the two F-15s made an attack run, dropping bombs. The lead aircraft (callsign Bolar 34) dropped a bomb from the left wing, and then began turning to the right to stay clear of the path of the second F-15's attack run. Here's a quote from the review of what happened next:

    At 10:27 p.m., Bolar 34 launched a JDAM against the target. The JDAM came off a left wing station. That added to the Strike Eagle's weight imbalance, or "lateral asymmetry."

    The F-15E's gun is on the right; the tank-feed anomaly meant Bolar 34 still had extra fuel in the right side external tank; and four bombs remained under the right wing.

    After weapon release, Harney started a descending right turn with 100-degree bank and 330 knots (380 mph) airspeed at military power—full throttle without afterburner. About 90 degrees through the turn, the aircraft nose dropped unexpectedly. Harney released stick pressure to reduce aerodynamic forces, but the accident report stated that the fighter "departed controlled flight" and went into a left spin.

    Harney attempted the normal spin recovery procedures to no effect and at 10:28 told his flight lead that "two's in a spin" and radioed, "Mayday, Mayday, Mayday," the international air distress signal.

    With the spin accelerating as the Strike Eagle approached the recom­mended uncontrolled flight minimum altitude, Harney told Stark to bail out and initiated ejection at an observed altitude of 5,715 feet, the accident report said.

    The ejection seats worked properly as both parachutes inflated and the crew­men suffered only minor injuries on landing. The empty Strike Eagle crashed to the ground and was destroyed.

       The whole story, with additional details and the story of the successful rescue of the 2 man crew is at the link above. While the maneuver the F-15 attempted was approved, no one had anticipated it would be carried out with the weight imbalance this crew ended up with. The verdict from the board that investigated the event had cold comfort for the pilot:
    The board said the pilot was not at fault, but added, "Evidence suggests that the [crew] was overconfident in the maneuvering capabilities of the F-15E.
    Hindsight is a wonderful thing - it you live long enough to practice it.

    "No special skill, no standard attitude, no technology, and no organization - no matter how valuable - can safely replace thought itself."

    by xaxnar on Sun May 26, 2013 at 08:50:11 AM PDT

    •  pity they didn't punch off the tanks and bombs. (0+ / 0-)

      if it were spinning, it's a risk but, it would let them
      get to a cleaner configuration.

      •  That was my thought, but... (3+ / 0-)
        Recommended by:
        eyesoars, BlackSheep1, sawgrass727

        I'd for sure try it in a simulator first - and at that the simulator probably isn't programmed for something that crazy.

        Plus, is it possible to release the kind of munitions load they were carrying without having acquired a target? I don't know. I suspect it's even harder to do while in a spin.

        The crew survived, so I can't second guess that outcome. Once they found themselves in a spin and approved procedures did not allow them to recover, the option they'd trained for in that kind of situation was to eject. Improvising is generally frowned upon by the Air Force - unless it works - and the stakes were a little too high to gamble. It was safer than trying to play test pilot in hostile air space, and that's what ejection seats are for.

        Plus, they didn't have the problem the crew of the Gimli Glider did: a plane load of passengers with zero options except for the crew to try what they successfully did.

        "No special skill, no standard attitude, no technology, and no organization - no matter how valuable - can safely replace thought itself."

        by xaxnar on Sun May 26, 2013 at 02:04:50 PM PDT

        [ Parent ]

        •  most fighters (0+ / 0-)

          have a bomb jettison capability.

          If something jumps you or a  missile comes up, you will need to get clean fast.

          Bombs should jettison pretty clean, they have a higher ballistic coefficient then a fighter,  now the external tanks may be harder to get rid of, they may have a lower ballistic coefficient and may come up and hit you.

          But if you can toss the bombs see if you clean up and if not maybe drop the nose and try and lose the tanks.

          it's hard in a flat spin to think up new procedures though

  •  Also, the car doesn't travel directly to the dest- (2+ / 0-)
    Recommended by:
    nailbender, Simplify

    ination, whereas a plane does.

    For example, on a square grid of roads, a car would travel 2 miles from one corner to another, whereas the diagonal would be only 1.4 miles.

    Also, a great circle from point A to point B would be fewer miles than any road network.

    •  Otoh, a plane has to rise and fall 6 miles. (2+ / 0-)
      Recommended by:
      Simplify, sawgrass727

      But that's relatively miniscule compared to the convoluted paths we take in our cars, not to mention the significant additional miles that cars rack up with their own elevation changes by virtue of going up and down hills and mountains to get from point a to point b.

      "Well, yeah, the Constitution is worth it if you succeed." - Nancy Pelosi // Question: "succeed" at what?

      by nailbender on Sun May 26, 2013 at 09:53:23 AM PDT

      [ Parent ]

      •  This raises another question: how much more fuel (1+ / 0-)
        Recommended by:
        Simplify

        does a plane to climb 1000 feet over, say 10 horizontal miles, versus level flight for 10 horizontal miles?

        (Or, put in your own numbers).  Surely, climbing takes more fuel than level flight.

        •  He probably factored that into his 400 mile trip. (0+ / 0-)

          I imagine the passenger miles/gallon changes a lot for longer trips for that reason.  

          "Well, yeah, the Constitution is worth it if you succeed." - Nancy Pelosi // Question: "succeed" at what?

          by nailbender on Sun May 26, 2013 at 10:54:29 AM PDT

          [ Parent ]

        •  It does (4+ / 0-)
          Recommended by:
          Simplify, Bob B, BlackSheep1, sawgrass727

          However we're much more efficient at higher altitudes.

          Generally speaking the longer the flight the more you save by climbing higher.

          In the old days I used a rule of thumb that I'd have to be at the higher altitude for at least 30 minutes to make it worth the climb.

          Today I just plug the numbers into the plane's FMS and it does the cost-benefit analysis for us.

          The 8000 pounds I used in my calculation took into account climb and descent fuel.

          When you descend you get back a lot of what you spent getting up to altitude because the engines are mostly at idle. For the last 100 miles or so we're practically gliding.

          If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

          by Major Kong on Sun May 26, 2013 at 11:08:36 AM PDT

          [ Parent ]

  •  Question: On a "typical" jet, how much fuel would (2+ / 0-)
    Recommended by:
    Simplify, foresterbob

    you need to fly, say, one pound of cargo (luggage, human fat, etc.) for 1000 miles?

    •  This will take a little math (8+ / 0-)

      Using the 757 as an example, because that's what I'm most familiar with.

      We normally carry around 40,000 pounds of freight. To go 1000 miles would take around 2 hours so call it 16,000 pounds of fuel.

      16,000/40 = 400 pounds of fuel (59 gallons) per 1000 pounds of freight

      That's just an approximation of course. A lot of the fuel burn is due to the weight of the aircraft itself.

      What we'd really like to know is how much extra gas we need to carry for each extra 1000 pounds of freight. I'm sure our flight planners have a formula for that but I don't know what it is.

      I don't know how that compares with trucking the freight but shipping it by rail would certainly be much more fuel efficient.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 09:26:55 AM PDT

      [ Parent ]

      •  Dunno if it would help... (0+ / 0-)

        but your L/D tells you how much extra thrust you have to use to carry the weight. E.g., if your airliner has an L/D of 15 at cruise, then it will require an extra 1000/15 = 67 lbs of thrust per thousand pounds of cargo.

        If you have an SFC (specific fuel consumption) value for your aircraft, you could maybe use those two together for a guesstimate.

        I would suspect that your most efficient flight profile would be closely approximated flying at your best L/D speed at full throttle. You start off climbing as rapidly as possible, and then slowly climbing for most of the flight as your fuel load burns off, followed by a gliding descent to your destination.

        The heavier you are at launch, the slower you'll be able to climb and the shorter your range will be.

        •  We call that a step climb (3+ / 0-)
          Recommended by:
          BlackSheep1, sawgrass727, eyesoars

          When I was in SAC, some of our war plans would have had us flying a very slow, constant climb as our fuel burned off to get maximum range out of the aircraft.

          It's not possible to do that in controlled airspace, but our flight plans sometimes have us climbing to a higher altitude after we've burned off some fuel.

          If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

          by Major Kong on Sun May 26, 2013 at 07:01:50 PM PDT

          [ Parent ]

          •  I've heard, but cannot claim to know... (0+ / 0-)

            that this is/was a fairly common profile for trans-Atlantic and trans-Pacific flights. Also stories about heavily loaded aircraft trying too hard to reach unattainable altitudes too early, sometimes resulting in (relatively spectacular) stalls around 30,000' in DC-10s or similar.

      •  Is this math approximately right? (0+ / 0-)

        Empty 757: about 130000 pounds (http://en.wikipedia.org/...).
        Our hypothetical cargo: 1000 pounds = about 1/130 of the total weight.
        So, the fuel to carry this extra 1000 pounds for 1000 miles is about:
        59 gallons / 130 = about 1/2 gallon

  •  I'm surprised that Jet A costs less than 87 octane (2+ / 0-)
    Recommended by:
    Simplify, foresterbob

    What is that due to? Lower sales tax? Cheaper refining costs?

    •  Much less refined (7+ / 0-)

      Jet fuel is mostly kerosene, which is closer to diesel fuel than anything.

      That figure I quoted was the wholesale price. You'd pay a lot more if you bought it at an FBO.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 10:20:58 AM PDT

      [ Parent ]

    •  The cost difference reflects Federal (5+ / 0-)

      and State taxes, but it also reflects the volumes being purchased.

      Unlike a driver who pulls into a station to buy 10 or twenty gallons of fuel, Jet A is purchased in the thousands or hundreds of thousands of gallons. This eliminates a couple of levels of middleman and drastically reduces the cost of transporting the fuel to the end user.

      Outside any major airport you will notice very large 'tank farms' which store enormous quantities of fuel, which is then piped directly into the airport, so that the airplane refueling trucks are able to pick up fuel without traveling more than a short distance.

      Here's my take on it - the revolution will not be blogged, it has to be slogged. - Deoliver47

      by OIL GUY on Sun May 26, 2013 at 10:45:50 AM PDT

      [ Parent ]

  •  jet travel is mass transit. (0+ / 0-)

    now if you want to be efficient, you take a train or  a boat.

    The ASM is another way to calculate it rather then P-M/Gal.

  •  Not so long ago I took an Emirates A340 (2+ / 0-)
    Recommended by:
    ybruti, foresterbob

    nonstop between Dubai and LAX, which was about 18 hours.  Just how much fuel does a bird like that carry, and how much more efficient is that aircraft than a 747SP, which used to be the jet to use on truly long-haul flights?  I wonder, too, how many tanks an A380 has and where they would all be located.  

    -7.13 / -6.97 "The people never give up their liberties but under some delusion." -- Edmund Burke

    by GulfExpat on Sun May 26, 2013 at 10:26:01 AM PDT

    •  Not Sure (4+ / 0-)

      The A380 may not have more fuel tanks, just bigger ones. There's a lot of room for fuel in that huge wing.

      I know the airlines don't really like the A340 because with 4 engines it's less efficient than the A330 and I'm not sure it carries that many more passengers. I flew on one from Paris to New York once and it seemed like a nice jet.

      I was able to find you an article about the A340 fuel system

      A340 Fuel System

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 11:04:19 AM PDT

      [ Parent ]

    •  18 hrs non-stop! (1+ / 0-)
      Recommended by:
      foresterbob

      I remember 13 from JFK to Riyadh. That was long enough.

      The spirit of liberty is the spirit which is not too sure that it is right. -- Judge Learned Hand, May 21, 1944

      by ybruti on Sun May 26, 2013 at 11:07:56 AM PDT

      [ Parent ]

    •  Strangely the A340 has the same wing as the A330. (1+ / 0-)
      Recommended by:
      Simplify

      The 330 wing is built with the interior parts for two additional engine pylons. The fuel systems are identical in the wings. However, the center wing tank is not completed in the A330-300 while the -200 has a functional center wing tank. The difference is in sealing the space to hold fuel, plumbing into the fuel system, and pumps. The maximum fuel for the -200 and A340 is 245,000# but only 172,000# for the -300. Yes, it is a huge tank.

      I seldom saw the center wing tank loaded with any fuel on the -200 but we almost never flew longer than 12 hours either. 172k# will come close to providing 12 hours of flight under most conditions in the A330. The other restriction that would limit loading fuel would be the much lower certificated maximum gross weight of the A330 with respect to the A340. We couldn't load much fuel in the center without running up against max weight which would in turn limit payload. The A340 also has a center main landing gear, just like the DC-10-30 and -40, to accommodate a higher max gross weight.

      Time makes more converts than reason. Thomas Paine, Common Sense

      by VTCC73 on Sun May 26, 2013 at 08:59:32 PM PDT

      [ Parent ]

  •  I was told at one time that the SR-71 fuel tanks (2+ / 0-)
    Recommended by:
    markdd, BlackSheep1

    ...leaked like sieves on the ground.  The seams had to be sufficiently loose at ambient temperature in order to absorb the amount of expansion that occurred at Mach 3.  The ground crew often ended their prep work covered in fuel.

    Good thing the fuel had a high flash point.

    "Ridicule is the only weapon which can be used against unintelligible propositions." - Thomas Jefferson

    by rfall on Sun May 26, 2013 at 10:50:05 AM PDT

    •  You're right (1+ / 0-)
      Recommended by:
      BlackSheep1

      They carried so little fuel on takeoff that one of the first things they had to do was refuel.

      “that our civil rights have no dependence on our religious opinions, any more than our opinions in physics or geometry.” Thomas Jefferson

      by markdd on Sun May 26, 2013 at 04:48:00 PM PDT

      [ Parent ]

      •  Yup... (3+ / 0-)
        Recommended by:
        markdd, BlackSheep1, sawgrass727

        The flight manual for the SR-71 was declassified some years back. They usually hit a tanker soon after takeoff, and fueling was non-trivial for several reasons. First, the SR wants to go fast, while the tankers (particularly the older-engined KC-135s) did not. So they usually had to refuel with afterburner lit on one engine. Secondly, the fuel fraction of the plane was fairly high, and it went from quite empty to quite full, so a lot of attention had to be paid to throttle and position.

        IIRC, Vne was 450 KIAS -- it could not go supersonic anywhere near the ground. Usually after topping off at the tanker, it would go through the 'dipsy doodle' around 27-28,000 MSL and do a constant IAS airspeed climb up past 80,000'. Mach limit was I think 3.44 from airframe heating.

        •  I think was also SOP (1+ / 0-)
          Recommended by:
          BlackSheep1

          to turn off the Encoding Altimeter as they passed thru 60,000'. so no one would know how high they were, just that they were there.

          “that our civil rights have no dependence on our religious opinions, any more than our opinions in physics or geometry.” Thomas Jefferson

          by markdd on Sun May 26, 2013 at 06:45:38 PM PDT

          [ Parent ]

          •  ... (4+ / 0-)
            Recommended by:
            Nebraskablue, rfall, markdd, Mathazar

            I can't find the details on mode-C, but controlled airspace ends at 60,000'. I don't know how high mode-C is capable of reporting, but I certainly wouldn't trust its accuracy above 50k'.

            There were stories, I don't know how accurate, of pilots calling up an unwary center controller:

            T644: "Tango 644, 100 miles west of Las Vegas, requesting FL 600"

            Center: "Buddy, if you can get to 60,000', you can have it!"

            T644: "Roger. Descending to FL 600."

            ----

            Then again, there was an incident  20-25 years ago where there was substantial wave activity over Maryland, and some gliders got a wave box open. The conversation with some jets out of Patuxent Naval Air Station reportedly went something like:

            Center: "Tango XYZ, be aware there is glider activity in your area".

            TXYZ: "What does that have to do with us? We're up here at 18,000'!"

            TXYZ: "The gliders are above you, sir."

            •  I've heard tales of pilots (1+ / 0-)
              Recommended by:
              eyesoars

              radioing ATC for ground radar speed checks.  After several 'weekend warriors' get their speeds checked, some SR-71 driver requests a check which clears the chatter with a speed check well over Mach 1.

              “that our civil rights have no dependence on our religious opinions, any more than our opinions in physics or geometry.” Thomas Jefferson

              by markdd on Sun May 26, 2013 at 11:47:08 PM PDT

              [ Parent ]

  •  The older planes certainly were more (3+ / 0-)
    Recommended by:
    Simplify, foresterbob, sawgrass727

    complex, that would explain why the third seater was in there.

    How is the fuel consumption on larger propeller planes?

    Has it improved like the jet engine fuel consumption? Like a Q400 vs a HS748.

    •  On short hauls (5+ / 0-)

      Turboprops are very efficient. That's about all I know.

      I suspect the newer ones are more efficient than the older ones, if for no other reason than better propellers.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 10:57:23 AM PDT

      [ Parent ]

    •  Fairly efficient... (1+ / 0-)
      Recommended by:
      Major Kong

      They have improved pretty much alongside turbofans. The major figure-of-merit for both is the compression ratio (like that of automobiles), the Brayton cycle for jets, the Otto cycle for gasoline or diesel engines.

      Large, modern turbines run around a 40:1 compression ratio (compared to 8:1 or so for a gasoline engine). It's somewhat lower for turboprops, if only because their turbines are smaller (nobody makes big turboprop airliners).

      There are two reasons that airliners want to fly as high as possible: one, turbines are very inefficient off-design-speed (half throttle may take 80% of full-throttle fuel flow), so best efficiency is found at full throttle; two, the most efficient airspeed to fly is called 'best glide' and is relatively close to stall speed. That's quite fast at high altitudes where the air is very thin, and full throttle consumes relatively little fuel. Up that high, turbofans are more efficient than turboprops.

      Down low, turboprops are much more efficient -- the big propellors grab a lot more air and convert energy from the turbine into thrust much more efficiently.

  •  Thank You - N/T (0+ / 0-)

    "Upward, not Northward" - Flatland, by EA Abbott

    by linkage on Sun May 26, 2013 at 12:16:23 PM PDT

  •  Transpolar flights (2+ / 0-)
    Recommended by:
    BlackSheep1, sawgrass727

    I was curious how much fuel savings transpolar lights would see, but what I came across, is how much additional radiation the passengers and crew would be exposed to.

    http://www.motherjones.com/...

    My question would be whether crew cabins, especially for military bombers, have any additional shielding for radiation. Otherwise, I expect that crews would be limited to some 10 or so flights per year.

    •  Not that I know of (4+ / 0-)

      The electronics on the B-52 were shielded against electromagnetic pulse.

      I don't know of any extra shielding for the crew. I often worried about all the microwaves from the various jammers and radars we had on that thing.

      Probably best for me not to think about it.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 05:08:44 PM PDT

      [ Parent ]

  •  Just read the Gimli Glider wiki link... (4+ / 0-)

    and there are a few quite disturbing paragraphs in there -

    As they communicated their intentions to controllers in Winnipeg and tried to restart the left engine, the cockpit warning system sounded again with the "all engines out" sound, a long "bong" that no one in the cockpit could recall having heard before and that was not covered in flight simulator training. Flying with all engines out was something that was never expected to occur and had therefore never been covered in training.
    The 767 was one of the first airliners to include an Electronic Flight Instrument System (EFIS), which operated on the electricity generated by the aircraft's jet engines. With both engines stopped, the system went dead, leaving only a few basic battery-powered emergency flight instruments. While these provided basic but sufficient information with which to land the aircraft, a vertical speed indicator – that would indicate the rate at which the aircraft was descending and therefore how long it could glide unpowered – was not among them.
    In line with their planned diversion to Winnipeg, the pilots were already descending through 35,000 feet (11,000 m) when the second engine shut down. They immediately searched their emergency checklist for the section on flying the aircraft with both engines out, only to find that no such section existed.
    Impressive flying on the part of the crew that they were able to land without any fatalities...
    •  Like Al Haynes' DC-10/UAL-232 (2+ / 0-)
      Recommended by:
      sawgrass727, PeterHug

      They had a lot of luck, both good and bad. The bad they got on their own, as they didn't independently check their fuel conversion constants. Both crews managed to find a need for sections of the flight manual that did not exist. Pearson and Sully were much luckier in that everyone survived the landings (maybe also lucky that both were experienced glider pilots and used to dead-stick landings).

      Fortunately for both, airliners have pretty decent glide ratios, even at 200 knots.

    •  There was a made-for-TV movie about it (3+ / 0-)
      Recommended by:
      BlackSheep1, sawgrass727, PeterHug

      Of course they had to change it from Canadians to Americans because I guess it always has to be about us.

      They seem to think American audiences can't relate to anybody from another country.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Sun May 26, 2013 at 05:06:50 PM PDT

      [ Parent ]

      •  Air Emergency / Mayday TV show... (1+ / 0-)
        Recommended by:
        PeterHug

        ...had a very good episode on the Gimli glider, and they kept it Canadian (they better have, since Mayday's put out by a Canadian TV studio).

        Those pilots were lucky sods indeed, considering they landed the thing at an airport that had been converted into a drag strip...and it was packed with people.  The only thing that kept the plane from a catastrophic collision with the crowd was the collapse of its nose wheel - that quickly brought the plane to a halt.

  •  Another great diary (6+ / 0-)

    My first job after HS in 1964 was working for Douglas Aircraft in Long Beach. I had to climb into the wing fuel tanks of DC-8's. There I would snake my way around all the baffles to the very tip. Once there I would start to work my way back with my bottle of Acetone and my sealant gun, cleaning and sealing the tanks as I went. It wasn't a job for someone with claustrophobia. Sometimes a person wouldn't turn up for break or the end of the shift. We'd have to send someone in to drag them out. That Acetone could knock you out if you weren't careful.

  •  Thanks Kong (1+ / 0-)
    Recommended by:
    sawgrass727

    Years ago I rode L-1011's from Portland to Seoul.  Afterwards I learned the L-1011's didn't have the "official" range to fly from Portland to Seoul with an FAA mandated 10% fuel surplus (around 1 hr extra fuel).  So they filed flight plans Portland to Tokyo, and if they were doing OK on fuel, they revise the plan in flight  and 'divert' to Seoul since they only needed .1 hr fuel reserve then.

    “that our civil rights have no dependence on our religious opinions, any more than our opinions in physics or geometry.” Thomas Jefferson

    by markdd on Sun May 26, 2013 at 04:53:42 PM PDT

    •  That is called a short release. (2+ / 0-)
      Recommended by:
      KenBee, markdd

      It takes advantage of the rules for how the international fuel reserve, the 10% you speak of, is calculated. I suspect 80-90% of my oceanic flying was done using a short release. I only came up short at our re-release point a few times and was always able to take advantage of other fuel planning rules to prevent having to land short of my scheduled destination. That's nearly 20 years of over water flying without having to divert solely for not meeting re-release criteria.

      The mechanism is a bit different than what you mention. The flight is flight planned and has a flight plan with air traffic control to the scheduled destination. However, the company dispatcher and the captain agree that if they get to a certain enroute position with less than a specific amount of fuel that the flight will divert to the short release destination. The dispatcher and captain must remain aware of both destination conditions to ensure a safe operation. But if they get to the short release point with the required fuel, as amended by the dispatcher for actual flight specifics, nothing happens except they flight continues as expected.

      The number one reason for this exercise is to limit the amount of fuel the flight needs for takeoff. A short released flight always required several thousand pounds less fuel than one straight released. This procedure keeps the company from carrying extra unnecessary fuel. Carrying extra fuel is not efficient. The saying is that it costs fuel to carry fuel. The figure for the 747-400 was 50% of whatever you started with would be burned before landing. So generally we thought long and hard before asking for that extra 5-10, 000#. There might be a discussion about justification but I never saw it denied if either the dispatcher or the captain insisted. The flip side is that diverting because you don't have enough fuel is very, very expensive. Not only do you burn much more fuel but the flying time increases (crew and airframe costs increase) and the schedule disruption to passengers and follow on flights is devastatingly costly.

      Time makes more converts than reason. Thomas Paine, Common Sense

      by VTCC73 on Sun May 26, 2013 at 09:26:12 PM PDT

      [ Parent ]

      •  Only hd to divert to Tokyo once (1+ / 0-)
        Recommended by:
        Major Kong

        Weather guessers missed winds aloft by about 200 knots....

        “that our civil rights have no dependence on our religious opinions, any more than our opinions in physics or geometry.” Thomas Jefferson

        by markdd on Sun May 26, 2013 at 11:42:31 PM PDT

        [ Parent ]

  •  Too bad the AF didn't make those nuclear planes... (0+ / 0-)

    They were experimenting with in the '50s! Think of all the gas we'd save!!

    It has to start somewhere. It has to start sometime. What better place than here, what better time than now? - Guerilla Radio, Rage Against The Machine.

    by Fordmandalay on Sun May 26, 2013 at 05:46:09 PM PDT

    •  Wasn't there a plan (0+ / 0-)

      to launch one of these things and fly it around over the USSR to directly irradiate the place?

      •  See my post about Project Pluto below (0+ / 0-)

        Its double posted because I got an error message from the site the first time I tried to post it, but somehow it did post, and.... aw you know.

        It has to start somewhere. It has to start sometime. What better place than here, what better time than now? - Guerilla Radio, Rage Against The Machine.

        by Fordmandalay on Sun May 26, 2013 at 08:55:14 PM PDT

        [ Parent ]

    •  BTW, check out 'Project Pluto'... (2+ / 0-)
      Recommended by:
      sawgrass727, eyesoars

      This is one of my favorite insane ideas from the Atom Age - a giant nuclear powered cruise missile, armed with 26 nuclear warheads. It was planned to have it cruise around the USSR at about 1000 feet at Mach 3, lobbing warheads at targets - plus it's sonic shockwave at that speed and altitude doing huge damage, along with spewing out highly radioactive exhaust from its nuclear engine.

      http://blog.seattlepi.com/...

      It has to start somewhere. It has to start sometime. What better place than here, what better time than now? - Guerilla Radio, Rage Against The Machine.

      by Fordmandalay on Sun May 26, 2013 at 05:53:03 PM PDT

      [ Parent ]

    •  Plus, check out 'Project Pluto' (1+ / 0-)
      Recommended by:
      Major Kong

      One of my favorite insane Atom Age ideas, it was a giant nuclear powered cruise missile that was planned to carry 26 warheads. It was supposed to cruise around the USSR at 1000 feet doing Mach 3, lobbing bombs at targets - plus doing incredible damage with its sonic shockwave at that altitude, and spewing extremely radioactive exhaust everywhere it went. GENIUS!!!

      http://blog.seattlepi.com/...

      It has to start somewhere. It has to start sometime. What better place than here, what better time than now? - Guerilla Radio, Rage Against The Machine.

      by Fordmandalay on Sun May 26, 2013 at 05:57:01 PM PDT

      [ Parent ]

  •  Great diary! (1+ / 0-)
    Recommended by:
    sawgrass727

    Great and simple explanations of what could be confusing information.

    For about 6 years, I lived near Chicago O'hare.

    Every now and then, when outside playing ball or something, we'd get a shower of Jet-A as a plane dumped fuel coming into O'hare. The smell was the dead give-away. I always took it as a sign that a just departed flight had to get back on the ground in a hurry.

    By the way, NASCAR has just converted from carbs to fuel injection.
    The fuel tank is just a single unit but it has 3 pumps in it.
    In each back corner is a boost pump filling a plenum. The plenum supplies the motor off the main pump.

    It took forever for some teams to realize they had to use larger capacity boost pumps than the main pump! They kept pumping the plenum dry!

    Enagaged activism wins elections. 100 million words on liberal/progressive websites gets beat by one new GOP voter casting their vote.

    by Nebraska68847Dem on Sun May 26, 2013 at 06:45:02 PM PDT

    •  Took 'em long enough (0+ / 0-)

      My 57 Desoto has a carburetor.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Mon May 27, 2013 at 10:20:46 AM PDT

      [ Parent ]

      •  eh... (0+ / 0-)

        The series isn't a "state of the art" like F1.
        NASCAR features racing competition.

        Many fans chide NASCAR as elitists but disregard the competition, lap by lap.

        I understand and appreciate the differences in all the series... The NASCAR carbs were fine. They served the purpose well, and were probably more reliable than most street fuel injection units available.

        Like all series, the cars have become aero designs. Too much "stick" and not enough power to make them unstable.

        I cannot wait until one of the major series reduces the tire width.

        Enagaged activism wins elections. 100 million words on liberal/progressive websites gets beat by one new GOP voter casting their vote.

        by Nebraska68847Dem on Mon May 27, 2013 at 11:44:19 AM PDT

        [ Parent ]

  •  Thanks for that. (0+ / 0-)

    These are always done very well, and a nice break.

    One question though (while we're on the subject of fuel systems)-

    How plausible is it, that TWA flight 800 simply exploded due to electrical issues in the fuel tanks?

    I'm not one for tin foil hats or any of the like, however I never found the explanation to be entirely reasonable, as this was very robust and proven design across many platforms.

    We're all suspected terrorists.

    by Boberto on Sun May 26, 2013 at 11:24:25 PM PDT

    •  Pretty plausible (1+ / 0-)
      Recommended by:
      Simplify

      I know of at least 2 KC-135s and a B-52 that exploded due to electrical issues in fuel tanks. The B-52 crew survived because the cockpit separated from the plane at the bulkhead.

      Usually it was due to leaving a fuel pump running in an empty tank. The fuel cools the pump so once the tank was empty the pump would get hot.

      As to the alternative theories. I would say a missile is the least likely. They were at 16,000 feet, which would put them above the range of most MANPADs. The wreckage, after if was pieced back together, did not look consistent with what a missile does to an aircraft.

      We're dealing with probabilities here, and the most probable explanation is the fuel tank.

      If the pilot's good, see, I mean if he's reeeally sharp, he can barrel that baby in so low... oh you oughta see it sometime. It's a sight. A big plane like a '52... varrrooom! Its jet exhaust... frying chickens in the barnyard!

      by Major Kong on Mon May 27, 2013 at 06:33:23 AM PDT

      [ Parent ]

  •  Longest glide by a commercial airliner (0+ / 0-)

    Saw this on 'Air crash investigation'
    http://deicinginnovations.com/...
    Although the pilots made things worse by continuing to transfer fuel from the good tank to the leaky one instead of considering why one tank was using fuel so rapidly.

    you don't believe in evolution, you understand it. you believe in the FSM.

    by Mathazar on Mon May 27, 2013 at 12:54:06 AM PDT

    •  Wow! (1+ / 0-)
      Recommended by:
      RiveroftheWest

      I've never heard about that incident before.

      Fortunately, airliners do have pretty decent glide ratios. And risk/fuel management is usually good enough that they just don't run out of fuel.

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