External Lighting Systems
 

Hello,

I am a post-grad researcher at Cambridge University and we are looking at reducing maintenence time in emergency aircraft. We are trying to find out whether present, incandescent lighting systems are adequate and the question is this:

- Do current lighting systems present maintenence delays or danger due to failure during operation?

We will also look at the cost implications of using LEDs instead of current lighting. Any thoughts or comments would be most welcome. You can e-mail me at [email protected] if you need to.

Thanks again!

Jonathan Biddle

No, fairly simple to change a tube or it's ballast.:)

Changing a light bulb on a small airplane may be easy, but changing a tail light bulb on a 747 may require shutting down the APU, as well as finding a cherrypicker or other lift to get there in the first place.

Nav lights fail often enough that many airplanes have 2 separate bulbs in each position for redundancy. I believe LEDs, if they meet the visibility and color requirements, would be ideal for this application.

Spanners

EXTERNAL INCANDESCENT lighting systems - tube or ballast????

But seriously I agree with intruder. Nav lights which are mandatory items and therefore probably most likely to cause a maintenance delay (along with anti-collision lights) would be ideally suited for LEDs.

I seem to remember reading a recent article about this in AVIONICS Magazine. Now that LEDs are available in most colours they are more likely available for more applications.

They would clearly be more reliable. For instance I have noticed how we rarely have to replace the switchlights in the B777 flightdeck (which make use of LEDs) compared to the incandescent switchlights in the B747 flightdeck.

Regards

Max

Very interesting- thanks for the feedback guys!

In general conversations with maintenence staff, bulb replacement is not a 'problem' per se; perhaps because it is part of the maintenance schedule. Any thoughts on that? Are bulbs changed routinely?

Also, is the problem worse in helicopters, due to greater vibration?

Many thanks!

:) Jonathan Biddle

AFAIK, light bulbs are only changed when they fail -- not on any schedule. Nav and taxi lights fail often enough anyhow, so routine replacement would be excessive, I think. Also, changing bulbs may not be "a problem" in most cases, but it does represent work that must be done, equipment that must be hired, and parts that must be ordered and stocked. All of those represent money spent (though the maintainers benefit via job security).

High-vibration areas do tend to induce early failure. The tail nav light on the A-6 Intruder was mounted on the rudder. It failed MUCH more often than the wing nav lights. I suspect the vibration on helicopters would cause earlier failure as well.

Great stuff.

It sounds like the maintenence companies are not the people to be approching for advice, as it is in their interests to change bulbs!

Do you, as pilots, have any decision- making power, or as a 'specifier' of components? Or do you just get what you are given?

Thanks once more!

Jonathan Biddle

I read somewhere (flight?) that a lot of the lighting on the A340-600 is LED. I could be worth a call to airbus.

Concerning your question about helicopter external lighting:

From memory, helicopter nav lights, in general, fail faster than the light fixed wing I'm familiar with. Some mechanics will tell you some models are worse than others, but a quick study done at a previous employer didn't show any significant variation amongst the models we dealt with.

Not that I know anything about the topic really, just a comment:
There is at least one aircraft out there that uses high intensity discharge landing lights...you know the metal halide/mercury/xenon discharge combo zero time strike/restrike ones. These obviously have a much greater life span, and output than 'normal' bulbs. They are also far more efficient on a lumen/watt basis than normal incandescent bulbs.

One such aftermarket system for GA aircraft is called the "Boom Beam." There may be others.

Roughly how long would it take to change a bulb for different aircraft; for example a 747 wingtip compared to an accesible helicopter light?

Just thinking about time and economic costs involved.

Jonathan Biddle