Guys, I am trying to keep the build simple!!! now you want me to do shock cones in the exhaust!
What about this for an idea?
I received the lighting system in the mail today and immediately set about testing if the idea that I had with it works. I think it has been successful but I still have a fair way to go before I am happy with it.
Here is the system that I got. It is a Turnigy Simulated LED system from Hobby King. It is designed for RC aircraft and as such is being modified to fit the Concorde. I am keen to avoid making the model `toy like' so I am devising this system without any external switches or any other indication that I have just thrown a few LEDs around the model. I am also aiming to have the model look totally stock when the lights are turned off. The lighting system has provision for flashing lights, nav lights, strobes etc depending on how each LED is hooked up to the controller. I will be just hooking up four LEDs to act as `reheat' (one for each exhaust) and possibly two white LED for each side of the fuselage under the cockpit as most photos of the aircraft in the takeoff pose show those lit.
I have already removed the battery connector in this photo hence the bare wires.

Here is an LED drilled into one of the exhausts compared to a stock exhaust on the right. Notice how apart from the clear LED, there is pretty well no change to the shape of the part.

It fits into the limited space inside the nacelle quite nicely. My plan will be to be able to pull out an exhaust pipe to allow access to a switch and to allow the batteries to be pulled out and changed. I have used 3 x 1.5 Volt AAA batteries at this stage, with the system allowing a maximum of 6 Volts. The challenge will be to see how long the batteries will power the system for vs how bright they are. Lots of tinkering left!

Here is the idea. Bear in mind that I will be changing the Red LED to an Amber one (the kit only comes with White, Red and green) But at this stage at least my concept is well on the way to working I have packed the exhaust with clear plastic to diffuse the light.

