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On 2 Aug 2002 08:54:16 -0700, Dan_Thomas_nospam@yahoo.com (Dan Thomas)
wrote:

>Weve had much shorter life wioth cowling-mounted bulbs than with
>wing-mounted units. The vibration of the cowling shakes the daylights
>out of the filament. A lot of this has to do with sagging engine
>mounts (in 172s) that drops the engine enough to make it rub on the
>cowling bumber at the front.
> Some folks have had better life by modifying the light holder to
>mount the bulb with the filament vertical rather than horizontal; it
>withstands vibration better this way. We use GEs quartz lamps (12V,
>H7604) and get many times more life. Weve had the ordinary bulbs fail
>in as little as 4 hours, but these quartz units last a couple hundred
>at least. We use the lights a lot, having them on in the circuit. In
>flight training, thats a lot of hours.
>
> Dan

Ive not seen anybody mention suppy voltage. It is my understanding
that a rough and ready estimate of bulb life is double for 10% less
volts and half for 10% increased volts. On this basis a close check of
the alternator/regulator might be useful.


David

Piper Warrior G-BHJO
Scotland, UK

E-mail (Remove Space after pilot): pilot 2002@lochaber-physio.co.uk

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