Landing lights on or off during start for longevity in piston singles?

[Jump Complete]

I occasionally fly a C206 which has landing / taxi lights in the nose. They tned to not last very long.
Battery considerations aside, is it better to have them on for start and shut down? I heard an opinion that if they are off the filliment is more brittle and therefore more prone to failure during shut down.

[Check Airman]

Can't see any harm in turning them off for start and shutdown. Then again, I've never seen anyone have them on before startup!

[The Flying Pram]

That's a new one on me - I fail to see how a filament heated to well over a 1000 degrees C can be less brittle than one which is cold! Years of practical experience has shown me that an operational filament lamp will fail very easily if subjected to vibration or a sudden shock, but you have to be fairly determined to break the filament when it's off. Think of the start up shaking that typically afflicts any piston engined A/C!! Many years ago I had to rubber mount the headlight on a motorcycle of mine as the bulbs, and speedometer were failing with alarming regularity. There might be a case for switching it on once the engine's running, then turning the generator on so that the lamp is not subjected to the maximum voltage in one go.

[the dean]

jump...

i know this is a tech forum..

i'm not an engineer, but a pilot of many years...

we would ( instructing ) only allow lights with brakes off and off again with brakes on...( an in that i also mean holding on the taxiways or runway.)

there may be other times ( say facing opposing traffic if you are the one taxying ) when it may be desireable ( instead of blinding the other pilot ) to go to taxi light only for short period...we always use both lights ( taxi and land ) at the same time . this prevents a pilot having his / her head in the cockpit for too long trying to figure out which is which.

by the way ...one of our guys came up with the idea that rotating the light ( usually its the hot landing light that used to blow on us ) so that the filament was vertical not horizontal...gave us much longer life..

it was not in a 206...so do'nt know if the mounting gives you that option...but for what its worth....

gear up..

the dean.

[P.Pilcher]

If you have ever dropped a handlamp or knocked a lit table lamp off its table then you will know that a tungsten filament heated to well over 1000 deg.C is much, much more fragile than a cold one. Thus if you want to reduce your operating costs never have a landing/taxy light on when starting a piston engine because of the severe vibration generated as the engine first fires up.

I can remember years ago our engineers moaning about the poor life and high replacement cost of our landing/taxy sealed beam units on school A/C. Simple solution: visit the local autospares place: The equivalent car sealed beam units were a direct replacement, lasted for ages and cost a fraction of that of the approved aviation spare!

P.P.

[Speedbird48]

Lets go back to the basics.

Why do you want your landing.taxi lights on when starting??? or stopping?? The battery would probably be very grateful if you left the heavy loads off, such as landing.taxi lights.

The normal operations of lights has been beaten to death here many times, and now we have a new technique!!

It is a known fact that a warm filament will be more tollerant of vibration. Look at the life of the pulsing lights that are around these days and you will see that they last a lot longer than the plain old On/Off variety.

Speedbird 48.

[c100driver]

Cessna cowl lamps are well know to have a very short life, the only way to increase that is to modify (via a 337) to a better quality bulb. Usually automotive motorcycle bulb.

My Cessna has wing mounted landing/taxi lights and they lasted 5 years and 3 years. My Hanger mate used to blow GE 4509 and Q4509 bulbs every 10 hours; 7 years ago he changed to the automotive style via a CAA 337 approval. He has not change a single landing/taxi bulb since then!

[411A]

OMG, not this again.
Leave 'em OFF for starting, and use ONLY when the light is needed to actually see where one is going.
Good grief...something so simple, yet a few 'new' folks want to make it complicated.
And expensive.:rolleyes:

[GOLF_BRAVO_ZULU]

Don't the AAIB lads use blown bulbs as a clue to which were lit when an aircraft piled in? A blown bulb was a lit bulb.

[displaced gangster]

C185/206/210's are well recognised as capable work horses.
These A/C are particulary popular in ISA+20 conditions due to the shade from the wing,strong field performance & good ground ventilation from the large windows.However the Continental IO-520 is hard to start when it is hot due to vaporisation in the injector lines.

If an attempt to start a hot IO-520 was made with any extra load on the battery than is necessary and this noted by your boss, you would most likely be rostered for remedial training.:cool:

[Agaricus bisporus]

Why, in the name of heaven, would you want to have landing lights on for starting? Or is this a misprint?
Anti col lights for starting, taxi lights for taxiing and landing lights for t/o, low level ops and landing. Perfectly simple. Forward facing white lights are only used when in motion.

I cannot imagine what use could be found for them on start-up


puzzled...

[Jump Complete]

Perhaps my initial post was not clear enough. I was not advocating doing this and I am well aware of normal lights on / off procedures. Also I am well aware of the problems of extra loading during start. It was in conversation with an aircraft engineer who was talking about how much better the life was when they were wing-mounted. He opinioned keeping lights on for shut down may improve the life. (Actually no mention of start, I simply put that in because that is presumably going to cause the same problem; then again perhaps not, maybe it is when the filliments are still hot, but not on, that it is most vunerable.) I wouldn't consider making every start with lights on, especially in a work horse with frequent start up and shut down cycles. My reason for the post was to gather opinions on the technialities of the best way to improve the bulb life. As a professional pilot I try to take critiscism constructively but I wasn't expected to be flamed on airmanship issues over this!
P.S. On the subject of non-aviation parts being often better and a lot cheaper (lets leave the legality issues alone here) I know of one ex Islander operator who when he needed to replace the bushes in the electric flap motor, found that the replacement bushes for a high quality food mixer where identical at a fraction of the cost!

[Agaricus bisporus]

Jump, I think most people (self included) assume that when you ask a question like that it is relating to something you actually do. It certainly reads like that. Apologies if I misunderstood.

Tungsten is a very hard element indeed and filaments are strong and rigid when cold, but are close to their physical limits when hot. Shake a table lamp and watch the filament. When it is on it will swing around like wet spaghetti. Too much of that and it can snap. break open a bulb and handle the filament, it is stiff and hard - not going to break easily.

Interesting point about filament vertical vs. horizontal, but you'd need a detailed vibration analysis of that part of the structure to see if there was a big difference between the planes, and which most disturbed the filament. A big harmonic may well be the culprit, but finding it would probably be the research of years. Empitical advice from an engineer may well be the better bet.

There seems a great deal of practical sense in using reliable, effective automotive halogen units (or genny brushes), but your insurers will be thrilled at the get-out you provided in the event of a big claim.

[Short_Circuit]

The “Boeing Maintenance Manuals” all state that the filament must be horizontal when fitted.

When in the horizontal position vibration & shock is pronominally in the vertical plane ie landing & turb.

The lamp filament being horizontal will bow up & down across the entire length of the filament and

the both attach points share the load. A vertical filament will concentrate the load at the upper or lower

attach point (one or the other not both sharing the load) where the entire force is felt. A warm filament

is not as brittle as a cold one, therefore less likely to break from shock & vibration. Some lamps have focusing

ridges internal to the front glass to aim, concentrate or scatter beams as designed for their positional use.

They are critical in installation orientation.

S_cct

[chainsaw]

GOLF BRAVO ZULU................

Don't the AAIB lads use blown bulbs as a clue to which were lit when an aircraft piled in? A blown bulb was a lit bulb.

Not strictly correct.

The various factors to be taken into account in analyzing aircraft light bulbs are listed below; each is discussed in some detail with appropriate illustrations on subsequent
pages:
1. type and manufacturer of bulb;
2. orientation of the bulb relative to the flight path at impact;
3. applied voltage during the accident sequence;
4. nature and severity of impact;
5. degree of aging.

See: http://www.tc.gc.ca/tdc/publication/pdf/6255e.pdf