That is the main reason I have had LED landing and taxi lights fitted, because I am fed up with them blowing in flight. It was getting to the point when it was a 50/50 chance that the landing light would come on.
I am hoping and expecting that the LED lamps will last longer than the airframe.
The average life of my bulbs are about 20 hrs. Changing them takes 5 mins, but I'm tired of changing them. I hope the price goes down soon.
There seems to be a battle between Whelan and Alpha Beam.
Alpha claims a much higher candle power, but Whelan claims that the Alpha ones dim after ten minutes use.
Could someone please tell me which they have and how happy they are with it?
Alpha claims a much higher candle power, but Whelan claims that the Alpha ones dim after ten minutes use.
The Whelen are old, first generation with a lot of lower power LEDs. The Alphabeams use the more modern Cree LEDs with custom lenses. They are vastly superior and from all LEDs I've seen at trade shows, they gave me by far the best impression in brightness and build quality.
The Whelen propaganda about the Alphabeams is nonsense. In their famous dim test, they run the Alphabeam "dry" on a table and show that after some time, they dim. This is because they contain a temperature sensor and reduce brightness in case they overheat. When installed in an airframe, they can dissipate heat through the fuselage and also get cooling airflow. I would not expect them to overheat. I once had them going for 20 minutes on the ground and did not notice any difference.
Many thanks.
I've just fitted a 'conspicuity light' to my a/c using a retro-fit wired halogen bulb - which on my Rotax powered LAA a/c, struggles a bit with the current production level at low (e.g landing phase) RPM. It was the most current-hungry circuit on the a/c - at nearly 5a (it's a 12v system), though during testing this actually proved to be OK.
Fortunately, the lamp fitting will also take an LED equivalent (which at around £16 is just cheaper than the halogen bulb costing £17), draws MUCH less current and is still bright enough for airborne conspicuity purposes.
Retrofit 'landing light' halogen lamp and bracket unit fitting - source link here: http://www.parts4aircraft.com/PBSCProduct.asp?ItmID=9383438
Substitution wired LED bulb source link (same package/fitting dimensions as the wired halogen bulb), here: http://www.autobulbsdirect.co.uk/h3-led-foglight-bulb-white-new.html
Re using the draw of the landing lights to check the charging system; turning on the pitot heat will give enough draw to ensure the alternator will pick up the load.
BPF - we may have wires crossed.
The issue with LED lamps in the TB20 taxi+landing light is that there are two indicator lights in the panel, which confirm the operation of these two lamps.
You can actually see the lights from the cockpit, anyway...
And the indicator lights are working from current sensing relays (example schematic - not sure which version of a TB this applies to). And the LED replacements draw a lot less current and fail to turn on the indicator lights. IMHO this creates an "illegal" situation unless the indicator lights are removed or placarded INOP. Today I have read something from somebody who claims to have spoken to somebody in the FAA who agrees with this view (which doesn't suprise me; no way can a duff indicator in the panel be lagel to fly with).
Peter
I see what you mean now. I can't imagine that a light to tell you your landing lights are on is a certification requirement, so it would seem to me you can just placard them INOP. However I admit I an not very conversant with the apparent rampant silliness in European regulations....
We've just invested in a ruck of Whelen Parmetheus LEDs for our fleet of PA28s and C152s (14 aircraft in total).
The standard 4509/4591 halogen lamps have a quoted life of 25 hours - this in reality equates to 25 flight hours not useage. A rough calculation showed an annual cost of over £5k in lamp replacement alone (includes buying, paperwork, fitting etc). Then if you factor in possible lack of earning when night flying and us pesky engineers have already gone home then the potential cost is immense.
Whelen quote thousands of hours of operation and give a 3 year warranty.
There are companies out there claiming that the LEDs need an EASA mod (at a cost....) but my CAA surveyor was content with the PMA/8130 trail, so it's just a log book entry to sign off installation. PMA parts are FAA approved and if they are being fitted to an FAA Type Certified aircraft then all is dandy. We fit a lot of PMA parts without EASA mods so why should a lamp be any different?
On my LAA machine we have AeroLeds lights (navs, strobes and landing light) - unfortunately not certified but excellent quality and very bright. Even with the 20A Rotax alternator, the load is tiny compared to the heritage lights.
With some cars that have 'bulb out' warning light systems you have to fit a resistor in the supply to confuse it into thinking all is normal when retrofitting LED lights.
With some cars that have 'bulb out' warning light systems you have to fit a resistor in the supply to confuse it into thinking all is normal when retrofitting LED lights.
That has been suggested but in this case the resistor would dissipate some tens of watts, which is a huge amount. Even if it was one of these
and bolted to a bulkhead it would get really hot. The thermal resistance of a 1.5mm ally hull skin is of the order of 1C/W.
The better solution for TB owners with those reed relays would be to run the wire through the relay coil not once but several times 
But that's not an approved mod, so it's back to the usual issues...
Incidentally I wonder why some people get through so many bulbs. I got through several very early on but have been on the same pair for narly 10 years, and ~1200 airborne hours. However I don't fly with the lights on, except when flying below 2000ft in the UK 
It has been suggested that the bulbs should be fitted with the filament vertical because it withstands airframe vibration better that way. No idea if that's true but it does sound vaguely plausible. Also even a 0.5V change in the alternator output will affect lamp life by several times - it is more than exponentially related to the voltage.
