Explain these 747 condensation patterns?
Thread Starter
Join Date: Jul 2000
Location: Smogsville
Posts: 1,424
Likes: 0
Received 0 Likes
on
0 Posts
Explain these 747 condensation patterns?
On this pic you can see several distinct patterns created by the A/C.
One around the nose
Trailing edge of the left wing
Plus faint ones around engines 3 and 4.
Anyone seen anything like it before?
JetPhotos.Net Photo » N703CK (CN: 21939) Saudia - Saudi Arabian Airlines (Kalitta Air) Boeing 747-212B(SF) by gerard isaacson
One around the nose
Trailing edge of the left wing
Plus faint ones around engines 3 and 4.
Anyone seen anything like it before?
JetPhotos.Net Photo » N703CK (CN: 21939) Saudia - Saudi Arabian Airlines (Kalitta Air) Boeing 747-212B(SF) by gerard isaacson
Join Date: Apr 2000
Location: UK
Posts: 786
Likes: 0
Received 0 Likes
on
0 Posts
The nose/engines ones looks like early on-set of a sonic shock wave - but I would imagine that under reasonably normal atmospheric conditions the aircraft would have to be doing about M0.85 is for these to start to form. Not sure what Vmo in the 742 is but I would have thought this to be rare - although low air pressure may aid the formation of these effects.
See this for an image of the later development of a wave.
See this for an image of the later development of a wave.
Join Date: Nov 2008
Location: UK
Age: 64
Posts: 69
Likes: 0
Received 0 Likes
on
0 Posts
Forget; I would tend to agree with you there, a clever picture.
Mmo on the 'classic' is 0.92 and I understand the airflow begins to go 'supersonic' over the 'hump' first at a little over 0.92 (sorry I cant find a published figure but believe it is around 0.95) What sort of wave that would create would be interesting to see.
I have been up to 0.94 on a test flight (to function the overspeed warning, before you all start jumping) and cannot say I noticed much different apart from the increased airflow noise.
Rgds
CL747
Mmo on the 'classic' is 0.92 and I understand the airflow begins to go 'supersonic' over the 'hump' first at a little over 0.92 (sorry I cant find a published figure but believe it is around 0.95) What sort of wave that would create would be interesting to see.
I have been up to 0.94 on a test flight (to function the overspeed warning, before you all start jumping) and cannot say I noticed much different apart from the increased airflow noise.
Rgds
CL747
Well I really believe that this kind of discussion is more suited for the spotters forum.
I would query the photo details before even touching the question.
With that kind of clarity it probably is below 10k and thus the speed no greater than 250kts
I would query the photo details before even touching the question.
With that kind of clarity it probably is below 10k and thus the speed no greater than 250kts
Join Date: Jan 2008
Location: Jerudong/
Posts: 52
Likes: 0
Received 0 Likes
on
0 Posts
I will have a light-hearted go at this. No idea what caused the 'ring', but I would guess that the apparent side lobes around no.4 engine are vortices generated above the wing by the use of the speedbrakes. Similarly, the line of condense behind the port wing is the remix of flow which has been displaced further aft by the boards. The a/c is descending and is probably no higher than 5,000ft (going by the lens used). I am not a spotter so I could be wrong! Looks like a low morning sun which would suggest a heading of south-east.
Join Date: Jul 2006
Location: USA
Age: 41
Posts: 111
Likes: 0
Received 0 Likes
on
0 Posts
Could almost guarantee a/c is below 10kft, since the recognition lights are on.
Zoom in, you'll see it clearly.
Also if you zoom in around the FO wing forward part, right infront engines 3 & 4 you'll see a blue 'cut line' maybe?
Zoom in, you'll see it clearly.
Also if you zoom in around the FO wing forward part, right infront engines 3 & 4 you'll see a blue 'cut line' maybe?
Join Date: Aug 2007
Location: East England
Posts: 173
Likes: 0
Received 0 Likes
on
0 Posts
Wheres No2 Air con Pack Ram Air Inlet, appears to be missing!! Its an SF so would have been born with all 3, unlike an F.....Also IF one pack had been deleted then would have been no 1 or 2 pack......strange, possibly photo shop job? ....
Also aren't the indications behind no 3 and 4 engine the upper wing surface shock wave being shown. The one for the left wing being hidden from the camera angle?
Also aren't the indications behind no 3 and 4 engine the upper wing surface shock wave being shown. The one for the left wing being hidden from the camera angle?
Join Date: Jul 2002
Location: Close to space
Posts: 419
Likes: 0
Received 0 Likes
on
0 Posts
Not sure what engines this beast has but with Q engines, and I believe the 7R4G2, above about 25000' if you let the N1 drop below 60% air 'sipilage' out of the front of the engine. Now this photo looks like it shows an aircraft flying lower than 25000'. However if it was going much faster than a normal descent the same might happen, I dunno.
The one on the back of the wing I think is common to see, but you often see a sheet of condensation, perhaps for some reason we only see the outline on this photo.
The one on the nose? I dunno.
The one on the back of the wing I think is common to see, but you often see a sheet of condensation, perhaps for some reason we only see the outline on this photo.
The one on the nose? I dunno.
Join Date: Nov 2008
Location: UK
Age: 64
Posts: 69
Likes: 0
Received 0 Likes
on
0 Posts
Interesting theories, but.....
......sorry Guys and Girls I still believe that it is a clever picture and the "lines' in the sky are much higher than the 747, and as suggested by forget in post 3 have been made by high altitude fighters. Fair play to the photographer 
Look like Q engines to me.
Rgds
CL747
Look like Q engines to me.
Rgds
CL747
Join Date: Nov 2007
Location: Seoul
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
Not sure, but could the ring in front of the nose have something to due humidity and dew point? Something akin to a lenticular cloud (en.wikipedia.org/wiki/Lenticular). Just an idea, perhaps stupid!
TME
TME
Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
Join Date: Jan 2005
Location: Hampshire, UK
Posts: 4,011
Likes: 0
Received 0 Likes
on
0 Posts
It's either a photoshop hoax or contrails from other aeroplanes (military aerobatics most likely). I have never seen or heard of such contrails being formed. They are nothing to do with that 747.
Join Date: Jul 2002
Location: Close to space
Posts: 419
Likes: 0
Received 0 Likes
on
0 Posts
Just tried to contact the photographer to get him to come to pprune to talk about his photo, but for some reason the message is failing to send....someone else care to try? Would be interesting to hear about the conditions in the day etc etc from the guy that snapped this photo.
Join Date: Aug 2007
Location: Just west of the North Sea
Age: 69
Posts: 48
Likes: 0
Received 0 Likes
on
0 Posts
With 30 years imaging experience and a lifelong interest in aviation, in my estimation that pic is the result of some pretty bad photoshopping. Given five minutes tomorrow I could probably replicate the effects in that pic rather easily.
Firstly, the 'shock wave' is completely non-symmetrical. (i.e. shaky hand on airbrush tool via mouse/graphic pen). Secondly, it starts about one or two metres back from the nose of the 747. It is also disproportionately wide relative to the aircraft.
Those with a better grounding in physics than I might know better, but surely this would require a ridiculously high speed or some sort of very humid/dense atmosphere,
My money's on 110% fake.
Firstly, the 'shock wave' is completely non-symmetrical. (i.e. shaky hand on airbrush tool via mouse/graphic pen). Secondly, it starts about one or two metres back from the nose of the 747. It is also disproportionately wide relative to the aircraft.
Those with a better grounding in physics than I might know better, but surely this would require a ridiculously high speed or some sort of very humid/dense atmosphere,
My money's on 110% fake.
Join Date: Jul 2008
Location: Sydney
Age: 36
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
The photo can't be real, if that's a shockwave, the condensation should not protrude forwards from the wave but backwards only as the air pressure decreases rearwards. That has to be a cirrus cloud.