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That Vapor Trail Jets Make..why Don't  
User currently offlineSEA nw DC10 From United States of America, joined Oct 1999, 491 posts, RR: 1
Posted (15 years 3 weeks 5 days 7 hours ago) and read 5345 times:

Ok folks this may be a dumb question.

When I see planes at cruising altitude making that white vapor trail in the sky, I use my binoculars somtimes, and can see that the trail is coming generally from the engines in that area. Now, I just flew on a DC-10, and during cruising, I looked out my window, and I was sitting behind the wing, I could see the back of the engine, but didn't see that trail the entire flight. I looked also on a 757 and 777, and didn't see it either during flight. Where's that dang trail, I wanna see it in flight. haha Thanks

24 replies: All unread, jump to last
 
User currently offlineBen2 From , joined Dec 1969, posts, RR:
Reply 1, posted (15 years 3 weeks 5 days 7 hours ago) and read 5161 times:

When you look at those trails with your binoculars do you ever notice that they are "delayed"? It takes a few seconds for that hot air to condense when it makes contact with the cold air. On the flights where you could see the back of the engine, the plane was most likely making a vapor trail, but when the jet is at Mach.78 that vapor trail gets left behind and you cant' see it. Hope this helps...

User currently offlineMIKEYYZ From Canada, joined Aug 2011, 0 posts, RR: 0
Reply 2, posted (15 years 3 weeks 5 days 5 hours ago) and read 5128 times:


You can see the vapour trail if you fly a 4 engined plane and look out the last door (easier to see the trail on quads than twins because of the outbord engine). Of course it depends on the conditions altitude, temp....
I once sat in the last row of a 777 flight and saw the trail when i look back towards the horiz stab.

MIKEYYZ


User currently offlineHagi From Finland, joined Jun 1999, 176 posts, RR: 0
Reply 3, posted (15 years 3 weeks 5 days 5 hours ago) and read 5116 times:

I did once see the vapour trail. The plane was a 757, and I was sitting maybe halfway back from the trailing edge. I looked back and the trail seemed to start at about the tail of the plane.

User currently offlineAC_A340 From Canada, joined Sep 1999, 2251 posts, RR: 1
Reply 4, posted (15 years 3 weeks 5 days 5 hours ago) and read 5105 times:

The best conditions for seeing them is mid winter, at a high altitude and sitting in the back of a plane. That the way the air condenses faster. Also I've noticed high bypass engines have the trail appear sooner. I think this happened because the bypass air doesn't get as hot as the air going through the combustion and therefore condenses quicker. Has anyone else noticed that?  

User currently offlineDustweek From Japan, joined Aug 1999, 77 posts, RR: 0
Reply 5, posted (15 years 3 weeks 5 days 5 hours ago) and read 5108 times:

Slightly unrelated, but...

On a flight from Fairbanks, Alaska to Barrow on the Arctic Ocean, I saw a fat dark line--parallel to our route--ahead of us on the flat snowy tundra.

As there are NO manmade objects in that area it was quite puzzling, until I realized it must be the shadow of our own vapor trail.



User currently offlineBruce From United States of America, joined May 1999, 5065 posts, RR: 15
Reply 6, posted (15 years 3 weeks 5 days 3 hours ago) and read 5088 times:

Can you see the trail from a smaller jet like 727 or DC9? Everyone seems to have seen it from a big one like a DC10 orr 777. I have been on a couple flights this year and didn't see it....but I do frequently see them from the ground.....white streak cutting across the clear crystal blue sky. I think they're easier to see when the sun is low in the sky, not high overhead. When I see one I often wonder where they're going to...


Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
User currently offlineLH423 From Canada, joined Jul 1999, 6501 posts, RR: 54
Reply 7, posted (15 years 3 weeks 5 days 1 hour ago) and read 5079 times:

I know that it takes a while for the vapour to appear, but last winter 1 Jan to be exact, I flew on Lufthansa, and as we were around 10,000 metres I could see the vapour trail forming right outside my window (51A, in the centre of the wing and the lest exit. I was surprised by this, because I live in Boston which it the motorway of the sky for all New York bound flights, so I often will try to identify planes way up, and will notice the vapour not starting until well aft the horizontal stabiliser. This has puzzled me, so maybe someone could answer this one: Why did the vapour trail form almost directly out of the engine, instead of nehind the aeroplane.

LH423



« On ne voit bien qu'avec le cœur. L'essentiel est invisible pour les yeux » Antoine de Saint-Exupéry
User currently offlineWilliam From United States of America, joined Jun 1999, 1317 posts, RR: 0
Reply 8, posted (15 years 3 weeks 5 days ago) and read 5076 times:

Depending on what side you sit on,if you look on the ground or on the clouds you can see the shadow of the contrail. I wonder if the people on the ground even notice when the shadow passes over them.

User currently offlineAC_A340 From Canada, joined Sep 1999, 2251 posts, RR: 1
Reply 9, posted (15 years 3 weeks 5 days ago) and read 5070 times:

Ita ppeared sooner because it was winter so it was colder. Because it was colder, it condenses faster, thats why you noticed it quickly.

User currently offlineJim From United States of America, joined Jul 1999, 455 posts, RR: 1
Reply 10, posted (15 years 3 weeks 4 days 23 hours ago) and read 5073 times:

Not entirely related, but, once I was sitting in the middle of the wing on a 737-200, heading Southeast-ish into the early morning sun. I noticed a thin shadow running from the fuselage all the way out to the wing tip. It moved maybe one inch back and forth for the whole time I watched it, maybe 20 minutes. It looked like the shadow of a rope, snaking back and forth.

My question to all you junior physicists out there: Was this the shadow of the center of pressure along the wing MAC? I feel it was the shadow of a disurbance in the airflow, and that theory is the only thing I can think of.

Let me know what you think, Okay?

jim


User currently offlineBruce From United States of America, joined May 1999, 5065 posts, RR: 15
Reply 11, posted (15 years 3 weeks 4 days ago) and read 5049 times:

I have seen some real bright ones (from the ground) and I don't live in a cold climate. Keep in mind that even if it is warm on the ground it is very cold at 35,000 feet. Remember Payne Stewart's plane? Flying from MCO to South Dakota it was definitely not winter and experts said that the cabin temperature could have been as low as -70f. !!!! The Air Force jet saw ice on the windows!

When I lived in Tallahassee, Florida, I would sometimes see half a dozen trails or more streaking across the sky on a clear day! It was amazing. That area is right in the path of jets going to MCO, TPA, MIA, even JAX from places in the midwest so there was lots of traffic. Over here at GPT, I see trails coming from MSY and ones going from southeast to northwest, which I can figure would be a TPA - DFW, or MIA-DEN. Boy, do I have too much time on my hands!!  



Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
User currently offlineDC-10 From , joined Dec 1969, posts, RR:
Reply 12, posted (15 years 3 weeks 4 days ago) and read 5050 times:

The trail is behind the plane not right behind the engine...It forms wants the exhaust stream has slowed and cooled and that doesn't happen right outside of the engine. I've seen it twice on flights i've been on. I was in the very back of a United DC-8 and saw it when i looked back and I saw it when i looked back on a Virgin A340....check it out next time




User currently offlineJaemz From , joined Dec 1969, posts, RR:
Reply 13, posted (15 years 3 weeks 3 days 21 hours ago) and read 5039 times:

i always notice the trail at the edge of the wings behind the tiny winglets of A300s i fly on. not behind the engines.

User currently offlineMontenegro From Italy, joined May 1999, 545 posts, RR: 1
Reply 14, posted (15 years 3 weeks 3 days 18 hours ago) and read 5044 times:

Another dumb question related to the topic, why the military jet's do not have the condensed line behind??


Thanks


User currently offlineTriStar From Belgium, joined Oct 1999, 848 posts, RR: 1
Reply 15, posted (15 years 3 weeks 3 days 18 hours ago) and read 5047 times:

Adding my two cents, I can say I saw a vapor trail coming from a small business jet at BRU yesterday, shortly after take-off. It was there all along, and *right* behind the aircraft.

By the way, it was a very clear and sunny day, yesterday. I never thought I'd see anything coming from the aircraft taking off - other than exhaust gases, in the worst case. ;-)

This small jet *was* in fact the *only* aircraft that had a vapor trail that I saw, during those couple of hours that I was there.

Since I don't have any explanation, I may just have added to the confusion... Sorry about that. ;-)

TriStar


User currently offlineNight Hawk From Australia, joined Jul 1999, 273 posts, RR: 0
Reply 16, posted (15 years 3 weeks 3 days 11 hours ago) and read 5039 times:

Hi There

I believe what you are seeing there is the wingtip vortices produced by the winglets. Can someone correct me if Im wrong please :-)

Regards

Greg


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 17, posted (15 years 3 weeks 3 days 8 hours ago) and read 5028 times:

I'm surprised nobody has figured this one out yet!

Has anyone seen a high flying jet from the ground leaving no vapour trail? What is another name for vapour trail? With reference to the rainbow sightings, what is essential for a rainbow to be seen?

The answer is: water vapour. A "vapour" trail is formed by condensate on particulate matter from the engines. Clouds form when the moisture in the air has something upon which to condense, OR if the moisture in the air is cooled enough (dewpoint) to produce condensation (clouds). Exhaust from an engine is similar to the idea of "cloud seeding" - when aircraft dispense that iodide mixture to precipitate the moisture in the air, usually to accelerate rainfall and preclude the occurence of violent thunderstorms (if memory serves me correctly).

Normally the higher altitudes are quite dry, but in the advance of a warm front, moisture occurs in varying degrees at those altitudes. When I asked earlier about planes leaving no condensation trails, there are times when they leaves a short trail that sublimates almost immediately - a sign that there is some moisture in the air; sometimes the trail lasts for an hour - a sign that there is a lot of moisture in the air.

So like the appearance of high cirrus cloud advents the approach of bad weather, so might the appearance of long standing condensation trails.

Waddya'all think about that?!

Note of interest: While in the arctic, it was a common occurence to see the turboprops landing with a stream of "smoke" coming from their exhausts. Our company got calls on more than one occasion suggesting an airplane was on fire! It was just so cold and damp that a condensation trail occured.

Note of interest #2: about 6 months ago, I was returning from Hamburg to Toronto at FL390, when out of the corner of my eye, I saw a condensation trail above us, but quite high, and moving a lot faster than our M0.80! Sure enough, BA1 checked in with Gander OCA as we watched this "speck" (we could not see the actual plane at the head of the trail) continue its trek at FL585/M2.0. A week later, in virtually the same spot, the same occurence, but just the radio call - no contrail. After talking with other pilots who have done the route many more times than I, this was a rare sighting.

Great question, by the way.


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 18, posted (15 years 3 weeks 3 days 8 hours ago) and read 5024 times:

I'm surprised nobody has figured this one out yet!

Has anyone seen a high flying jet from the ground leaving no vapour trail? What is another name for vapour trail? With reference to the rainbow sightings, what is essential for a rainbow to be seen?

The answer is: water vapour. A "vapour" trail is formed by condensate on particulate matter from the engines. Clouds form when the moisture in the air has something upon which to condense, OR if the moisture in the air is cooled enough (dewpoint) to produce condensation (clouds). Exhaust from an engine is similar to the idea of "cloud seeding" - when aircraft dispense that iodide mixture to precipitate the moisture in the air, usually to accelerate rainfall and preclude the occurence of violent thunderstorms (if memory serves me correctly).

Normally the higher altitudes are quite dry, but in the advance of a warm front, moisture occurs in varying degrees at those altitudes. When I asked earlier about planes leaving no condensation trails, there are times when they leaves a short trail that sublimates almost immediately - a sign that there is some moisture in the air; sometimes the trail lasts for an hour - a sign that there is a lot of moisture in the air.

So like the appearance of high cirrus cloud advents the approach of bad weather, so might the appearance of long standing condensation trails.

Waddya'all think about that?!

Note of interest: While in the arctic, it was a common occurence to see the turboprops landing with a stream of "smoke" coming from their exhausts. Our company got calls on more than one occasion suggesting an airplane was on fire! It was just so cold and damp that a condensation trail occured.

Note of interest #2: about 6 months ago, I was returning from Hamburg to Toronto at FL390, when out of the corner of my eye, I saw a condensation trail above us, but quite high, and moving a lot faster than our M0.80! Sure enough, BA1 checked in with Gander OCA as we watched this "speck" (we could not see the actual plane at the head of the trail) continue its trek at FL585/M2.0. A week later, in virtually the same spot, the same occurence, but just the radio call - no contrail. After talking with other pilots who have done the route many more times than I, this was a rare sighting.

Great question, by the way.

Best Regards,

Buff


User currently offlineBruce From United States of America, joined May 1999, 5065 posts, RR: 15
Reply 19, posted (15 years 3 weeks 3 days 8 hours ago) and read 5027 times:

I have also seen wingtip vortices while flying - coming off the wing of a 737 and a 757. Its a combination of hot humid weather, low altitude (landing), slower than cruise speed. Its condensation that is being blown off the wing. On the other hand the vapor trails from behind the jet in cruise is from the engine exhaust condensing. 2 different things.


Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
User currently offlineATA757 From United States of America, joined Apr 2011, 0 posts, RR: 0
Reply 20, posted (15 years 3 weeks 3 days 7 hours ago) and read 5024 times:

I have never seen a vapor trail aboard an aircraft, but I always grab my binoculars and go outside to see if I can see what kind of plane it is. One day I was outside and I saw a 747 fly over with 4 well-identified streams, shortly after that I saw a Southwest 737(with the red belly) without vapot trails.

ATA757


User currently offlineSpence From United States of America, joined Aug 1999, 95 posts, RR: 0
Reply 21, posted (15 years 3 weeks 3 days 2 hours ago) and read 5018 times:

I've seen BAe ATP's leave contrails at 6000 feet on a cold winter day.

Also, if you have seen WW2 footage, B-17's at 20,000 feet leave contrails.


User currently offlineKaplano1 From , joined Dec 1969, posts, RR:
Reply 22, posted (15 years 3 weeks 3 days 1 hour ago) and read 5019 times:

The correct name for the vapour trail when you see a jet at cruise altitude is called a CONTRAIL. They are the white lines you see being left behind an aircraft when the warm air from the engines condenses with the cold air at the high altitude or something along those lines.

When an aircraft is landing or taking off you often see vortex or vortices forming on the wings, winglets, etc. Have a look next time you are on final approach or if you are watching and aircraft land and you will see the vortex.

The concorde also makes great vortex off the wings as it takes off.

Please correct me if I am wrong because I am just a aviation enthusiest and don't know all the technical/scientific terms regarding contrail or vortex.

I just think they look great. Here in Sydney, Australia we get SQ285/286 over flying the Sydney VOR enroute from Auckland to Singapore/ Singapore to Auckland. Also if you live west of Sydney you would see alot of aircraft over flying the KAT NDB (Katoomba NDB), etc.

Regards,
Steven


User currently offlineBruce From United States of America, joined May 1999, 5065 posts, RR: 15
Reply 23, posted (15 years 3 weeks 2 days 9 hours ago) and read 5014 times:

I think you're right, Kaplano1.

In addition to the vortices coming off wingtips & winglets they can also come off of the edges of the flaps when they are fully extended in landing configuration. Thats what i saw on a CO757. And the vortex was visible all the way until the plane was "over the numbers" right before touchdown!



Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
User currently offlineTriStar From Belgium, joined Oct 1999, 848 posts, RR: 1
Reply 24, posted (15 years 3 weeks 2 days 9 hours ago) and read 5014 times:

Since you guys obviously know more about this, I'd like to elaborate on the "vapor trail" I mentioned earlier. This one was very clearly coming from the *center* of the aircraft, and it was there right after take-off. No wingtips involved, no flaps involved.
This was a small businessjet with two engines mounted to the fuselage - comparable to the Canadair RJ, let's say.

So what did I see if it wasn't vortex, and it sure wasn't contrail?

TriStar


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