QF Overfly query

[Tim E]

Just had two big ones overfly here..I am guessing (from melair.com) that the first was QF 093 on her way to Sydney-L.A.

 

She was flying a bit lower than some of the other flights (she seems to do this on occasions) ..got a good view with binocs..no obvious contrail as she was low but instead I saw a thin stream coming out of the left hand wing tip (not near any of the four engines) I saw this once before last year..(not a visual illusion)..anyone help with what was happening there? And any ideas why she so often seems to fly lower than other flights at similar time of day on same day? Thanks. Tim

 

 

[Guest aviatrix27]

Now Tim, you've gone and started a spirited discussion in my household. We agree that the thin stream you saw coming from one wing tip and not the other has something to do with a cross wind. The discussion got spirited when we tried to come up with a reason for whether it would be the windward or leeward side!

 

As for the plane seeming at least to be lower than others, I can't come up with a logical solution, except maybe the pilot's scared of heights :biggrin:

 

 

[Tim E]

LOL..or maybe he was checking if my washing was on the line! :) Yes for some reason that flight. Maybe I'll get a letter from Qantas next week asking why I havent mowed my lawns recently! LOL

 

Yes(I'm sure its that flight) often flies a bit lower than others around same time like UA 840 etc.

 

Is the main reason craft go up high to do with fuel consumption. I guess on shorter trips though a craft would expend a certain amount of fuel getting up high so assume there would be an optimal height on each trip e.f. Mel-Sydney or would that vary according to winds, clouds, air temp etc?

 

 

[Guest aviatrix27]

Airliners usually opt for the best altitude for best economy. Some even do so regardless of turbulence. Here's a sanitised version of what I heard one day while flying along:

 

ATC: Flight X, I have reports of light to moderate chop all levels from FL280 to FL400, choose level.

 

Flight X: Request FL340.

 

ATC: Flight X, did you not hear me? I said light to moderate all levels FL280 to FL400, are you sure you want FL340?

 

Flight X: Affirm, FL340.

 

ATC: Your call, cleared FL340.

 

If I had been on that flight, I would have wanted to strangle the pilot. Obviously, his calculations revealed FL340 was the best economy and he wasn't changing his mind for anything. Thankfully, most are not quite so rigid in their flight planning, I also regularly hear pilots requesting diversions due to weather and change of altitude due to turbulence.

 

Personally, I pick a level that's correct for the direction I'm flying (1500, 3500, 5500 east, 2500, 4500, 6500 west) and is the lowest option bearing in mind terrain, clouds and turbulence.

 

 

[Guest Glenn]

Perhaps it was fuel overflowing or just a vortice

 

 

[Tim E]

Yes both sound like good possibilities Glenn and Kaye..just reading up on vortices and contrails here and the differences. Most interesting and educational for me. The wind here seems a light northlery Kaye so if it was from that direction when she flew over, seems like the unprotected side of the craft. Thanks. Cheers Tim

 

 

[Uncle Chop Chop]

Wow what a question. I would have thought that it was because it was so full that it took a longer time to come to altitude.

 

 

[Guest Darren Masters]

I think it could be fuel overflow. Also, if there is high humidity you can get vortices-sometimes off one wing only.

 

 

[Coop]

Certainly nothing to do with cross-winds. Airliners fly straight through the air except when landing in cross-winds. To do anything else would chew up large amounts of extra fuel! I think fuel vapour venting is the most likely explanation. I'd be surprised if variations in humidity would be so sharp at that altitude as to give a vortex contrail from one wing and not the other. You could get this effect close to the ground where there might be significant variations in humidity over short distances (such as a wingspan) as a result of turbulence.

 

Coop

 

 

[Tim E]

The colour of the vapour or whatever it was did seem more of a browny dull colour and not the usual white of a contrail..if that helps.

 

 

[Tim E]

Was just thinking...if there were normal engine contrails as well as the wing tip trail, that would suggest some condensation occuring? But as there were no normal engine contrails at all and the aircraft was reasonably low, would that suggest there wouldn't be any other condensation and that the fuel theory might be the most likely in this case?

 

Am enjoying all the contributions and thoughts on this one. Oh, QF 093 flew over this morn, again reasonably lower than a Virgin Blue flight that was just ahead of it..normal contrails today and nothing from wing tip. Cheers Tim

 

 

[Guest Darren Masters]

Tim I really would say that it is fuel vapour in this case. I have seen it many times, often only out of one wing.

 

 

[Robbo]

Oh, QF 093 flew over this morn, again reasonably lower than a Virgin Blue flight that was just ahead of it

There will be a aircraft next week flying very very low around your area next week Tim......:rolleyes:

 

 

[Tim E]

Thanks Darren..yep it seems that to be the case. .Hey Robbo are you doing an Easter Egg drop up here next week? My chimney is blocked so I can arrange to either catch them or set up something soft so they arrive safe and sound! :biggrin:

 

Seriously, will you be overflying here or landing Benalla? What is most likely day?

 

 

[Robbo]

Not me Tim.... The RAAF are doing some Hawk training around Wangarratta and further to the North.

 

 

[Tim E]

Thats something to watch out for and to look forward to Robbo! Even better than the Easter eggs! Any ideas on which days?

 

 

[Robbo]

Not sure mate, I heard it from one of the RAAF boys the other day. Just check the daily notams for wang and see if anything pops up about low level military ops.