Zoom in: RAF flame suppressors

Zoom in: RAF flame suppressors

In preparation for my build of Tamiya’s 1/32 Mosquito FB Mk.VI I did a bit of reading on the flame suppressors.  It’s an optional part with a lot of interest and history.

The flame suppressor is an extra cowl placed over the exhaust to reduce aircraft detectability at night.  Unlike in a car engine, aero engines had a very short exhaust pipe, so it wasn’t uncommon for these high-performance engines to emit flames from the exhaust stacks.  The stacks themselves grew extremely hot, so any unburnt fuel in the exhaust could flash.

During the day, this wasn’t an issue.  The flames are ghostly and barely visible.  At night however they stood out against the darkness.  Not only was this flame visible to enemy aircraft, but  could also interfere with the pilot’s night vision.

The suppressor wasn’t intended to prevent the flames, but to cover them over and reduce the visibility issues.  In practice, they don’t appear to have been especially effective: they added weight, potentially further reduced performance as the exhausts couldn’t clear, and even glowed at night.

There is even reference to one RAF bomber type where the addition of the cowls made the aircraft dangerously overloaded.  This is from “The Dam Busters” which doesn’t specify the type, but a bit of cross-referencing suggest it was the Hampden bomber.

As modellers, the cowls are most interesting for the weathering opportunities they provide.  These patterns vary between aircraft, but on the Mosquito we see:

– A tight, dark sooty exhaust stain, Very narrow.

– Multi-layered heat effects on the cowl, from burned-away paint to what may or may not be rust.

– When removed, the bare metal contact patch often remains, as does the dark, narrow exhaust stain.  A broader, less prominent stain forms over the top.

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