I've been discussing "chemtrails" with somebody who appears to be a vigorous believer in them. I've tried explaining, but to little avail. However, I've recently discovered that this person lives very close to an airbase. More interestingly, a little research has uncovered the fact that KC-135 Stratotankers are based there.

I was wondering if there was any standard procedure by which such aircraft dump untransferred fuel prior to landing, or if such dumps were relatively common for any other reason (emergency dumps, or something?). Given that so many of the "chemtrail" pictures are of aircraft dumping fuel, I was wondering if those petrol stations of the air routinely or regularly dump fuel - and help explain (even more than just the proximity of the air base) the inordinate amount of "chemtrails" this individual claims to see ("white aircraft, spraying" he's said).

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Good thought and possibly a factor. Although the frequency shouldn't be that great.

Emergency dumps would be the main activity that would produce fuel-related contrails. Every aircraft has a maximum landing weight. If something went wrong with the fuel transfer and the tanker were required to land almost immediately, then the only way to achieve that safe landing weight would be a fuel dump.

However those should be very infrequent. Having lived near airports and air fields, I'm sure the primary reason for the situation is instead this. The traffic around such locations can be pretty heavy, especially if there's a problem with, for instance, the weather elsewhere and the field is being used as an alternate landing site. Even without those circumstances traffic is heavy compared to places well away from the airport.

Either way, one winds up with a lot of planes in the air, many in holding patterns. Holding patterns stack up, eventually reaching altitudes where contrails are formed, given the right conditions of temperature and humidity. At those altitudes, planes look very small to the unaided eye.

Also if the weather is good enough (i.e., relatively cloud free), then there will be a blue sky with good illumination from the Sun. One last factor is most of the livery on an aircraft is on the sides. The bottom tends to be free of decoration and highly reflective. Even with planes that have paint on the bottom surfaces, when highly illuminated, small to the eye, and seen against a high-contrast dark blue background, these objects appear to be a shade of white. Here's an example with a B-52:



What's the end result? To the eye these tiny aircraft look as though they are white, especially when contrasted against a blue sky, and are emitting contrails which, due to conditions at those altitudes, bloom out into wide trails of water vapor/ice crystals.

So there you go, to the untrained, inexperienced eye, this looks highly suspicious. To the eye used to seeing planes flying at altitude in high contrast conditions, everything looks normal.

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As people spend more time indoors, the sky and the things in it become less familiar. Sad really.

While I'm no expert on tanker planes, I'd imagine that they only take off with the amount that is required by the mission and not necessarily topped off. Plus these things also have cargo decks. It's not just one big gas tank. Thus there are no rows of seats and no rows of passengers. Unless they are hauling cargo, the deck is full of air so the weight that would be passengers, baggage and all the furnishings that go with them on a civilian plane is made up of fuel. Thus they probably aren't much heavier than a loaded out passenger plane and probably wouldn't have to dump much if any fuel to get down to landing weight.

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Can you imagine what kind of trouble you would get into if you (John Q. Public) would get into if you went and sprayed hundreds of gallons of diesel fuel from your Cessna over a lake or ocean bay somewhere? Golly!

Regards, tbm

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My father was a KC-135 pilot. The KC-135 is capable of landing with a full fuel load. However the increased weight means a more difficult landing, something a pilot will want to avoid if they are making an emergency landind due to other problems with the aircraft.

My father made several emergency landings in the KC-135, but these were mostly due to a lack of fuel as a result of giving as much fuel as possible to striken fighter aircraft.

I've seen several pictures of KC-135's doctored to look as if they are streaming a chemical cloud from their wings.

Very rarely would KC-135s dump fuel prior to landing, as they were capable of landing with a full fuel load. More often would be aicraft such as C-130s, which would have the capability of dumping fuel if necessary before landing.

Regardless, fuel dumping among aircraft is exceedingly rare. It usually occurred about 1 out of 500 missions, if that.

Not to mention that a fuel dump would take place over an unpopulated area. If they had to land immediately, well, they'd dump wherever they had to - but only in exceedingly rare cases would they do that.

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Swissair Flight 111, an MD-11 which crashed crashed off th coast of Canada in 1998 was instructed to fly a circlular route off the coast to dump fuel prior to making a landing attempt. Even in that emergency situation, they did not attempt to dump fuel over populated areas.

Here is a link to some info on the flight


During the recent emergency landing of an Airbus in California, the plane circled for hours, partly because it was not capable of dumping fuel (according to CNN).

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Many airliners have no fuel dump capability and must fly around until they have burned off the fuel. The recent A320 nose gear incident being a good example.

I happen to live next to an air base. In fact, I've lived next to several, including ones containing KC-135s, B-52s, and C-130s.

Bottom line: Fuel dumping is an emergency measure ONLY. It's never used during normal operations. Even during an emergency, aircraft will burn off fuel in holding, unless deteriorating conditions (such as an onboard fire) require an immedate landing and the aircraft is above maximum safe gross weight for landing.

Furthermore, fuel dumping is restricted below 5,000 feet AGL. Is is to ensure that the fuel dissipates enough to prevent any surface source of ignitiant from creating a Die Hard like fire trail.

Having said all of that, I do know that KC-135 crews conducting MITO takeoffs fully-laden with fuel would occassionally have to dump below 5,000 feel AGL, and immediately after take-off due to an engine failure during take-off, because their three-engine service ceiling was lower than field elevation at their takeoff gross weight.

Bottom line - fuel is expensive, and military aircraft don't dump fuel unless it's absolutely necessary and critical for the immediate survival of the aircraft.

All woo-woo theories to the contrary are simply, well, nuts.

Just to clear up some misconceptions, the KC-135 has a max takeoff weight of about 322,000 lbs and a max landing weight of 200,000 pounds, so there are situations, most likely multiple engine failure after heavyweight takeoff where fuel may need to be dumped quickly, but otherwise fuel dumps are generally prohibited unless absolutely necessary, and then are restricted to designated areas, typically high altitude, over water, and require all sorts of environmental impact paperwork to be completed afterwards. So to answer the original question, other than critical emergencies, the main reason to dump gas would be a heavyweight takeoff where for some reason the receiver aircraft is unable to take on fuel and it is not possible/practical to have the tanker and crew fly around for hours and hours burning off fuel, and these situations are rare, as jt-3d said, tankers, and for that matter most large jet aircraft, normally takeoff with only the minimum fuel needed.

I would imagine a KC-135 crew that encounted a receiver problem (non-emergency to the KC-135) would simply decide to fly some high-level legs, rather than orbiting at a holding point.

Can you do non-touch and go transition (down to minimums, then go-around) at gross weights higher than max landing weight?

I do a lot of flying, and some of that is on commercial planes.

I usually sit near emergency exits (I teach emergency egress from commercial aircraft, so they like to put me where I would be of use).

I can't count the number of heavy takeoffs in which I've enjoyed watching a thick, opaque condensation trail form over the wing, 4 or 5 feet from my window. All it takes is a high angle of attack and a little humidity.

I've seen the same thing happen when letting down on approach -- the latest example was on Wednesday, on approach to ORD. For the record, I was NOT flying in a spy plane, ag sprayer or UFO.

Contrails come in a lot of different styles.

Welcome to the forum 135Guy and Critic-at-Arms. Your input is much appreciated.

There's a difference between a contrail and the vapor appearing in the low-pressure area immediately above and behind a wing.

A contrail is formed by the introduction of excess water vapor into a cold enough atmosphere to freeze the excess moisture into ice crystals.

The other phenomena is called a Prandtl-Glauert condensation cloud. It involves no addition of moisture, so once the low pressure is removed, as the airplane passes, the condensation very rapidly disappears. The condensation is caused by the fact that lowering the pressure also lowers the temperature, to the point where the dewpoint is reached and condensation occurs. When the low pressure returns to normal, so does the temp.

If you look at external photographs of this phenomena, you'll see that it only trails the wing by a few yards.

Prandtl-Glauert Condensation Clouds also occur when low-level aircraft are travelling beyond Mach 1. The shock wave is high pressure "peak" of the wave, but it's immediately followed by a low-pressure "trough" of the wave.

Read more, and see a really cool pic, here: http://fluidmech.net/tutorials/sonic...ert-clouds.htm

hi, another thought as to the way some contrails appear. The higher the aircraft the "thinner" the air. This and lots of other factors will allow the trail to appear closer or further away. So those pictures that claim a chemical vapor coming out of the wings is twisted. As air pressure decreases the trail may even start creeping up the fuselage and the leading edges of the wings. There are 3 generations of military, commercial, and corporate pilots in my family, I guess they are all trying to kill me!

Here's something I often see when I'm on a commercial jet:
When we are at cruising altitude and I am sitting on the side of the plane facing away from the Sun, I can look down and see the shadow of our own contrail on the clouds below.

Occasionally, when I am on planes that have their engines on the wings, I can twist around and look back and see the contrail starting to form back beyond the tail

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