Heavy Prop Over Scotland

[NorthernChappie]

4 prop over central Scotland around 16.00 utc today heading west. High enough to leave chemtrails (;)) but nothing showing on playback on FR24. Any ideas?

[Bigears]

USMC C130 flew overhead Glasgow towards Dublin at FL220 at that time- very noisy for a Herc.
First time I've seen a prop chemtrailing - must be a cost reduction thing :-)

[mikeygd]

nothing showing on playback on FR24. Any ideas?
If you haven't discovered https://www.adsbexchange.com/ then I recommend it for anything that doesn't show up on FR24 (ie. military) It's doesn't do playback though (unless I'm doing it wrong). This screenshot was a result of querying their database based on Bigears's reply. Really is shocking that they've resorted to chemtrailing from Herc's. ;)

1590

[El Bunto]

First time I've seen a prop chemtrailing FlyBE's Dashs and Loganair's 2000s seem to be able to hit trailling conditions occasionally. It makes me look every time, seems odd to see something moving slowish-ly and making a brrrr noise but pulling trails. I haven't yet seen an ATR doing so but they seem to top-out around FL170 which may not be sufficient.

[NorthernChappie]

Ta. There was an AN26 over us yesterday on a similar track and I just wondered if it was something like an AN12.

[DaveReidUK]

FlyBE's Dashs and Loganair's 2000s seem to be able to hit trailling conditions occasionally. It makes me look every time, seems odd to see something moving slowish-ly and making a brrrr noise but pulling trails. I haven't yet seen an ATR doing so but they seem to top-out around FL170 which may not be sufficient.

There was a lot of work done during WWII to try, not entirely successfully, to model the conditions under which USAAF daytime B-17 raids on Germany would be particularly vulnerable when conditions resulted in them creating contrails.

http://www.worldwarphotos.info/wp-content/gallery/usa/aircrafts/b-17/384th_Bomb_Group_B-17_Bombers_Leaving_Contrails_in_Sky_on_Mission.jpg

It's still an inexact science.

[KelvinD]

I was recently reading a book on Mosquitoes during WW2.
On some bombing missions, the navigator would kneel on his seat, looking aft and issue instructions to the pilot to alter altitude until they found a suitable level where the contrails would stop,

[MATELO]

http://contrailscience.com/skitch/Spanish_Air_Force_Hercules_contrail-20120930-102153.jpg

[Piltdown Man]

I think we will find that the gaps in the trails are due to the air being chopped up by the propellers. The pattern from jet aircraft is distinctly different.

PM

[BobbyHowie]

There has been an Atlas around Prestwick for a few days. Certainly noisier than a C130.
Maybe nipped up north for a jaunt?

[Richard Taylor]

I always thought AN12s started contrailing immediately after rotation :O

[El Bunto]

Coincidentally I just had a Loganair 2000 go overhead in crisp blue winter sky at FL270 without a trail followed by a Stobart ATR at FL210 with trails from both the engines and the wingtips!

[Dave Clarke Fife]

Calculating contrail levels was done in the good old days by The Met Office. They used to include a flight level called MINTRA or minimum trail altitude. This was primarily for the use of military pilots. Flying just below MINTRA would ensure that your position was not given away by contrails. The trail level can be calculated manually using a tephigram. The ascent curve for the current conditions is plotted until it reaches the line marked 'Mintra'. The level where the two lines cross is the 'exhaust trail' level. This used to be examined in the old style ATPL exams

A bit more background info:

'' To aid the forecasting of condensation trails emitted (or not) from high-flying aircraft, a line marking the critical temperatures (altitude dependent), above which trails are not possible, is marked on a tephigram (q.v.). The values are approximately -24degC at 1000 hPa (i.e. roughly sea-level), -39degC at 250 hPa (34000ft / 10.4 km) and about -45degC at 130 hPa (50000feet/15km). Using the MINTRA line (as it has come to be called - based on experiments by JK Bannon during World War II with the piston-engined Spitfire), a forecaster will mark two further lines on a tephigram: MINTRA minus 11degC (A) and MINTRA minus 14degC (B). If the ambient temperature (from the tephigram air temperature plot) lies between (A) and (B), then short, non-persistent trails are possible. If colder than (B), then long, persistent trails should be expected. However, some note should be paid to the relative humidity - high values will tip the balance to trailing (or longer/persistent trails.), even with air temperatures warmer than (A); ultra-low rh% will reduce the risk of condensation trails - the design of engines will have an effect as well. In broad terms, warm Tropical Maritime airmasses with a high but cold tropopause will result in a good deal of trailing, whilst cold, polar air-masses with a low, relatively warm tropopause will seldom give rise to significant aircraft trails.''

[N707ZS]

We had an M400 Cotam 2060 over Teesside but at about 18.55 sn 0010 heading South.

[El Bunto]

The trail level can be calculated manually using a tephigram.

That was all utterly new to me, thank you. I feel edumacted now.

[B Fraser]

Thank you Mr Fife. I was taught how to do that and was told that the Spit was a PR Mk19. Leaving a trail was not good for the success of the mission.

[DaveReidUK]

Thank you Mr Fife. I was taught how to do that and was told that the Spit was a PR Mk19. Leaving a trail was not good for the success of the mission.

What I want to know is how the RAF and USAAF mission planners got the Germans to tell them the air temperatures over Berlin ?

[El Bunto]

What I want to know is how the RAF and USAAF mission planners got the Germans to tell them the air temperatures over Berlin ?By about 1943 Bomber Command were updating the met obs & forecasts in real-time based on information relayed from nominated aircraft in the bomber streams and transmitting the revised data back to the same streams by HF.

I remember this being mentioned in 'The Other Battle' and from memory it was Main Force, not just Pathfinders, that modified their approaches based on the revised data. Sort of like an early, analogue, machine-learning algorithm...

[AtomKraft]

The U-2 has a rear view mirror on a long stick. It's there to check if the thing is laying a contrail or not.

Rest assured, that if it were possible, by planning alone, to ensure a 'negative contrail situation', it would be done.

The presence of the mirror shows that it just cannot be reliably predicted whether or not a contrail will form.

All that matters for the U-2 driver, is that he can see if he's pulling one, and do something about it if it's giving his game away.

[munster]

Chemtrail spraying by turbo prop is preferred in Scotland.
The wild haggis are particularly affected by the neurotoxins, so the finer distribution caused by the propellers is better for the wildlife.

[El Bunto]

The U-2 has a rear view mirror on a long stick. It's there to check if the thing is laying a contrail or not.

Whereas the B-2, being the complete opposite of the Skunk Works philosophy, apparently employs a rearwards-facing LIDAR that scans for formation of a contrail. Seems like a perfect homing target...

http://www.ebay.co.uk/itm/PILOT-ALERT-SYSTEM-TEAM-MEMBER-COFFEE-MUG-OPHIR-GRUMMAN-BOEING-B-2-/261619287306