Exhaust colours

[mossiepilot]

Just a daft question, why is the exhaust staining on a Lancaster pale gray/white when the stains on Spitfires and Hurricanes dark brown/black.

I was looking at some images of a model Lanc, I've got one in the stash and will be doing it soon, probably, and thinking that the modeller had been a little heavy with their exhaust staining, and I got to wondering why the engines exhaust gas of a Lancaster should produce light coloured staining and that of Hurries and Spits are darker.

The engines where the same, Rolls Royce Merlins, so why the difference in colour. Funny the questions you come up with when your minds wandering.

Tony.

[Alan 45]

I've noticed this , surly all exhaust markings should be a dark colour and only vary due to the lightness of the colour of the plane.

I'd just go with what you know and do it dark/black

Just a thought do you think it paint weathering from the heat of the exhaust.

[mossiepilot]

Don't know Alan, but all the photos of Lancs and kits i've seen built have the same light coloured staining, was just something I noticed and wondered why.

Tony.

[Guest]

Could it be that Spitfires and other fighters have a boost system which over fuels the engine? This would put out carbon rich exhaust and semi burned fuel.

Also, the fact that fighters are constantly altering engine speed to suit loading (diving and climbing) whereas bombers would be running at a constant engine speed and would therefore be running more efficiently.

Just a thought!

[stona]

The light colour is due to the lead content.

I have seen light staining on fighter aircraft too. I suspect that it would vary according to the engine settings, particularly the richness of the mixture.

As a by the way some late series Daimler Benz engines emitted so much black smoke when pushed to high boost combat settings that some allied pilots reported "black streamers" in combat/encounter reports!

A Czech Hurricane and helpful dog.



A PR Spitfire. I suspect that these flew with different settings to the fighters to maximise their range.



Typical Lancaster stains.







Cheers

Steve

[Guest]

Don't know if this will answer your question,but exhaust colour is effected by the fuel octane level and the mix of the fuel. Lower octane fuels as used by the Germans would rarely produce a light exhaust stain.While an engine that is run lean to reduce fuel consumption will tend to produce a lightgrey /white exhaust stain.One point about the Lancaster's exhaust stains the exhaust from the outboard exhausts largely flowed under the wing therefore you tend to see three exhaust stains per wing on the uppersurface not four.

Malcolm

I just seen Steve's beat me to it!

In Steve's photo of the Lancaster you can see the outboard exhaust stains are less noticably.A Lancaster crew,having a flight engineer,would more readily maintain a lean mix (light exhaust) to help maximise range.

[mossiepilot]

Cheers Terry, could be, I've been looking at other bombers, the Halifax which had Merlin XX's and the B-17 which had Pratt and Whitney radials, on youtube and they have dark stains. The only other aircraft I've noticed with light coloured exhaust staining is the P-38 lightning, where the exhaust is fed through a super charger, Could this be the reason do you think?

Tony.

[mossiepilot]

Cheers Steve and Malcolm, I was typing when your replies came up, so didn't see them til I'd posted.

T'was just an idle question but I sorta knew someone on here would have the answer.

Thanks again.

Tony.