posted 07-25-2001 10:17 AM            

quote:

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Both photos are of the same plane just a few seconds apart. The photos were taken on July 5 at approx. 9:00AM in Diamond Springs, CA. the plane approached from the South heading North. It sprayed for approx. 30 seconds, 10 seconds before I took the photo and about 20 seconds after. The trail that it left for that 30 seconds eventually turned into a high cirrus cloud that persisted for several hours. The relative humidity for sacramento at 300mb on July 5 was approx. 67%. Notice the white spray coming from the wings between the engines and the cabin."

"I'm sending you the uncropped picture of the Megasprayer I sent you. I thought it might be helpful in determining altitude. I believe it is a Boeing 757 series 200 with an overall length of 155ft. 3in. The print is 4by6 inches and as you recall was shot with 1000 mm lens."

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posted 07-25-2001 12:59 PM            

But given the lack of hard data regarding the aircraft's altitude and azimuth relative to the photographer, it's extremely difficult to differentiate between the 110-feet-long 737-700 and the 242-feet-long 777-300.

I have looked at the underside of the wings of the aircraft photograph; despite me seeing the engine and engine supports clearly, I do not see any evidence of longitudinal strakes beneath the wings. With the 757, 767, and 777 models, these strakes are quite large, and they (or the shadows cast by them) should be visible in the photograph. They are not.

Another possibility is that the aircraft in question is an Airbus Industrie A320-class (-318, -319, -320, -321 variants) or the larger Airbus A300- / A310-class (twin-aisle variants) however, they, too, are fitted with longitudinal strakes under the wing surfaces; moreover, their engine nacelles seem to be placed further forward on the wings thatn the aircraft in the photograph.

So what can it be? Well, if it's not an Airbus or a Boeing aircraft, that doesn't leave anything I can think of (Lockheed and McDonnell Douglas aircraft to not fit the configuration at all). So obviously the aircraft must be one of those mentioned above.

But, as I said earlier, given the lack of atlitude/azimuth data and the inherent graininess of the photograph, there is no way I can think of to identify the aircraft even to the manufacturer level, say nothing of the particular model.

Regards,

posted 09-01-2001 04:51 AM            

The most recent arguement to have been made is that the the perspective of the witness has caused the illusion of four seperate trails to appear as one. However, in these photographs, this is not the case. And yet both examples depict this anomalous prismatic effect. This rare effect leads me to believe that we are witnessing the same causitive factor in both examples.

The same effect can be observed in 'sun-dogs' and 'sun-rings' that occur during heavy spraying.

posted 09-01-2001 10:55 AM            

it definately is a boeing 757 producing classic aerodynamic contrails. this is exactly what they look like when you see them up close. as a matter of fact, this could be a text book picture demonstrating these type of contrails. you see this alot during a climb when the wings are producing a ton of lift. as a matter of fact, the 757 is really good at this as their wings produce a hell of alot of lift. they actually have different seperation criteria because of the wake turbulance that they produce.

duncan mentioned that he couldnt see the flap fairings. this is because of he resolution of the pic. they are there.