Every time I've seen Merlins start from cold they have the lazy flame effect from priming.

Some times depending on the lighting conditions you wont see too much of this effect, the camera though does see it very well.

I'm fortunate to be a member of FOD (Duxford) so I practically lived there a few years ago and saw a lot of aircraft in preparation for shows and being started for testing etc etc, Merlins especially as there are so many of them at Duxford :)

Perfect find fireflyerz, thanks for posting. Must have had the mixture bang on in this run up, lots of blue and more blue. A brief flash of orange/yellow flame on initial start - just like in the 1st Oleg video.

A red flame from a single stack at one stage I noticed.

I was so glad when they turned the lights off. No illumination of the side panels at all really - maybe very slight at one point but just immediately around the stacks. Best video yet.

Cheers

The flame color is a product of the temperature (that whole quantum-mechanics stuff). For these engines one of the biggest factors is the mixture.

A leaner mixture will result in higher temperature (and higher power) - which results in flames on the blue side.

A richer mixture will result in lower temperature - so the flames go to the orange/red side.

In my experience with Cessnas, you would start the engine at full rich fuel mixture. I would think most engines would be started at full rich, and leaned afterward.

In a new engine, this would probably result in yellow flames on startup. Once the engine is leaned, it would go toward blue.

The only thing about these videos is they are showing old aircraft with old engines. I would suspect that the conditions of individual engines (even different cylinders on the same engine) and the fuel systems probably play into why some videos show a variety of colors.

I would hope that different flame colors are modeled (blue - orange/red), depending on the engine conditions.

Nice, I love the how you can see the effect of the prop torque effects on the aircraft when throttled up too fast.

The only things I have to say echo what people have said before; the smoke in the startup video disperses too quickly and the exhaust flames should not light up the side of the aircraft in the second video.

smoke disperses differently depending on what it consists of, relative atmosphere, humidity, temperature and the like - and so does the color pf the flame vary depending on the fuel, the mixture of fuel/air, the last time the engine was fired and the way it was shut down, etc...

so many variables that to deduce whether a single video render depicts the effect accurately or not is ludicrous -

ever see a stack fire? that is why at airshows you always have a guy or two with fire extinguishers standing by any warbird that is about to have its engine started.

the color and strength of the flame can be from practically invisible - to a massive yellow flame and fire. The smoke volume and color can be just as variable.

should Oleg try to cover the entire range of this effect? Of course not - the resources are better used elsewhere. Should there be some variation between night and day, cold engine vs refuel rearm restart? Probably

Will everyone be pleased with whatever these effects end up as? No

This is just another example of a developer trying to add small details that bring life and character to a simulation and having it blown out of proportion utterly by a few professional smoke and flame specialists ad alta

:grin: True!

I don't think we need to search for anymore exhaust flames. That video has it all in one.

Oleg asked for opinions, he got opinions; I think there was a fair amount of worthwhile input in the pages of this thread, some of which I'm sure Oleg found useful. He can sort the wheat from the chaff.

Did it ultimately overshoot the mark? Yes.

Was it nonetheless a good discussion? Yes.

I know I've learned a lot! Expect more of the same next week :)

Cheers, Spinner

a littel more red a littel orange less yellow. but it looks good dude get that track bug sorted and get it to the stors asap DO LIKE