Flight routings/747 over Liverpool/contrails

[mcdonnellluke]

Hello
My name is Luke and I live in Liverpool not that far from John Lennon Airport LPL. I have noticed on Tuesday Mornings for the last 2 weeks between 08.00 and 08.30 a 747 passing over on a south easterly heading at about 23,000 ft (below contrail altitude). This would make it a bit to high for MAN, but a bit to low for LHR etc. anyone any ideas of what flight this might be? A cargo 747 to EMA maybe? Also I get a lot of high level contrail traffic over my area including plenty of transatlantic and domestic traffic. I have seen the NCL-Milan BGO flight pass over at contrail altitude coming in from the northeast and then taking a sharp left turn southwards-would that be the standard routing for this service and would it be at contrail altitude by then? Also what are the lowest contrailing aircraft you have seen-I have seen a Ryanair 732 pulling a contrail enroute from BHX-DUB at FL180 one evening-this seems unusually low for contrail formation has anyone seen anything contrailing lower? Also what is the lowest altitude contrails usually start to form and has anyone seen a contrail start to form as an aircraft is climbing and reaches contrail atitude, or has seen it stop during the decent?
Luke

[Rainboe]

Luke- well done on your spotting!
The impression I have had over the years is that contrails seems to be a 30,000'+ phenomena. The vast majority of the time, aeroplanes don't seem to make contrails. I have frequently seen them 'switch on' suddenly- frequently they switch on and off as the aeroplane flies through slightly more moist air pockets. I haven't seen them on climbing or descending aeroplanes, but then we don't really see many other aeroplanes in those phases of flight. I've never been aware of contrails in those phases of flight, and I've never seen them more than 'a few' (very few) thousand feet below the levels I have flown at in civil jets.

[Groundloop]

Contrails can happen at lower altitudes. Look at films or pictures of mass formations of B-17s during WWII. Often they are trailing contrails and B-17s cruised at about 20,000.

[BOAC]

'Contrails' have been seen in arctic regions during ground running of engines - it is all to do with a thing called 'MINTRA level' (google?).

This is (was?) normally notified during military flight refuelling briefings etc to avoid leaving an open invitation to 'shoot me down'!

[magpienja]

Hi luke just as a matter of interest I used to live in liverpool as a kid 40 odd years ago and I was a keen airband listener then, although they were hard to come by in those days but the listening was much more fun in that the aircraft all use there reg numbers as a callsign and also gave position and ETA for there next waypoint, IE pole hill at 16 est wal 26 fl180, but I do remember a BEA (beeline) vanguard turboprop fl190 with a con trail only one I ever saw with a con trail, those were the days.

Nick in cheshire.