cessna 172 landing light

[kiloindiapapa]

I have a 1963 Cessna 172D. It has a landing light and a taxi light. The landing light is burnt out. Questions....

1. What kind of light should I buy. LED? Brand?
2. Why is there a taxi light and a landing light on this plane. They both shine to the same spot (which I assume is wrong). What is the purpose of the taxi light and where should it point to?

Thanks

Paul

[niss]

http://www.aircraftspruce.ca/catalog/el ... glites.php

Pull the landing light out and cross reference the #. You can also go to NAPA and cross reference it to their housebrand light and save yourself some considerable $$ if it is a Private A/C.

[iflyforpie]

Most likely it will be a GE 4509. Yes, go to an auto parts store and save yourself a few bucks and days of shipping. Even for commercial ops you can use commonly sourced parts with the same part number--provided the failure of said part doesn't affect airworthiness....

CAR 571.07

(3) No certification referred to in subsection (1) is required in respect of a new part that bears markings identifying it as a part specified in the type design and that

(a) is a standard part;
(amended 2002/03/01; previous version)

(b) is a commercial part;
(amended 2002/03/01; previous version)

(c) is a part that was not originally designed and manufactured for aeronautical use but has been approved for use on the aeronautical product in the type design.
(amended 2009/12/01; previous version)

CAR 101.01

"commercial part", in respect of an aircraft, means a part
(amended 2002/03/01; no previous version)

(a) that is not specifically designed or produced for use as an aeroanutical product,

(b) that is made to a specification or catalogue description and marked under an identification scheme of the maker, and

(c) whose failure does not adversely affect the continued safe flight and take-off and landing of the aircraft; (pièce commerciale)

[Posthumane]

I don't think they landing and taxi light point to exactly the same spot, though it's pretty close. I think the taxi light points a tiny bit lower, or at least that's how it seems on my 172A. Also, I don't know if you have pull switches or rocker switches in your plane, but on mine it's a pull switch, with the first stop being "taxi light" and the second stop being "landing light". The taxi light stays on when you turn on the landing light, so you get the additional brightness of two lights on instead of one.

The landing light sucks up so much juice on my plane that if I'm doing continuous night circuits (low power and therefore not charging as well) the battery voltage drops over time and after about half an hour I end up with a dead radio and dim lights all around. So, when doing circuits I use the taxi light.

[Strega]

I don't think they landing and taxi light point to exactly the same spot, though it's pretty close. I think the taxi light points a tiny bit lower, or at least that's how it seems on my 172A. Also, I don't know if you have pull switches or rocker switches in your plane, but on mine it's a pull switch, with the first stop being "taxi light" and the second stop being "landing light". The taxi light stays on when you turn on the landing light, so you get the additional brightness of two lights on instead of one.

The landing light sucks up so much juice on my plane that if I'm doing continuous night circuits (low power and therefore not charging as well) the battery voltage drops over time and after about half an hour I end up with a dead radio and dim lights all around. So, when doing circuits I use the taxi light.

you must have a generator installed...... should be the 35 amp unit so it should be able to keep the battery charged with the landing light on.. you might want to have it looked at.

if I remember correctly the 4509 bulb is 100Watts,, ,so you should only be drawing about 7.5 amps when its turned on,, if you generator cant keep up with this load,, its time to take a looksie.

[Posthumane]

Hmm, I haven't checked its output. What RPM is the 35 amp rating at though? It's fine at cruise RPMs, but doing a low/no power approach causes the charge light to come on and the voltage to start dropping. It's fine for a while, but during continuous circuits it doesn't have time to make up for it during climbout and downwind so with each circuit the voltage drops more and more until it's below that required for the radio.

If the landing light draws 7.5 amps, the taxi light is probably the same (same bulb, I think?), plus a bit of power for the position and anti-collision lights, the radio, the transponder, the interior panel lighting, etc. So I imagine the actual draw with everything turned on is better than 20 amps.

[niss]

How's your battery?

[Strega]

Battery has nothing to do with it...

your battery is there to start the plane, excite the alternator/generator, and in the event of a failure of the charging system, allow you to keep some electrical capacity.

[Big Pistons Forever]

As posthumane pointed out the old style generators fitted to 1967 and earlier C 172's (ie the ones with the 6 cylinder Continetal engine) will only put out a significant charging current above about 1700 RPM. Any operation below this and the battery will be taking most of the electrical load, so a weak battery will be a problem. Aircraft batteries are built to be a light as possible, therefore they are not very sturdy, so you can only realistically expect 2 to 3 years of life. The other problem is most of these aircraft still have original wiring. So in the case of the original poster the wiring is 47 yrs old. If the high draw heavy wires connecting the generator, starter, and main bus are original they probably have developed high resistance and so are wasting some of your power.

[iflyforpie]

Battery has nothing to do with it...

your battery is there to start the plane, excite the alternator/generator, and in the event of a failure of the charging system, allow you to keep some electrical capacity.

The battery has quite a bit to do with it actually. From experience, I've traced probably 90% of widespread electrical faults back to a battery, whether it be corroded connections, low electrolyte, or sulphur contamination from sitting without a charge for too long. These same batteries had enough juice to crank over the starter (which doesn't care too much about voltage) but would make radios go apeshit at lower RPMs when the generator kicks out (because radios are very sensitive to voltage).

Batteries are always the first thing you check...

[niss]

Haha! I was right!

[Posthumane]

The battery electrolyte levels are good, there is no corrosion, and the battery holds a charge well. When charged manually or after doing a regular flight with a cruise period there is no issue with it for a long period of time. Even doing circuits with just the taxi light on continuously I usually have no problems, it's just the combination of all lights on and low power for extended periods that causes issues, which isn't really unexpected in a generator equipped aircraft.

As to the OP's questions, it looks like both the landing and taxi lights use the same bulb - GE4509. Perhaps someone with the maintenance manual handy can confirm this. I have considered LED replacements but I'm not sure they're worth it for the price ($250-$350 per bulb). They would presumably last much longer (probably the life of the plane), which may or may not be a big deal depending on how often you use (and therefore replace) your lights currently. The teledyne LED replacements which are supposed to be sold at aircraft spruce soon look like the best option - they have a slightly higher beamwidth AND higher luminous intensity than a GE4509 (165k Cd vs 110k Cd). The Whelen and AeroLED units have a lower luminous intensity than the GE4509, but slightly higher beamwidth.

I noticed that some of the LED replacement bulbs come in a "landing light" and "taxi light" version. Presumably the taxi light is less focused (higher beamwidth) than the landing light so you get a wider illuminated area in front of the plane at a cost of lower luminous intensity. Does anyone have a spec of what the landing and taxi lights should consist of in general?

[Big Pistons Forever]

One reason to consider the LED bulb is the fact that the power consumption can be up to 80% less than a conventional filament bulb. This alone may make your power troubles go away. They are very expensive compared to the GE 4509 bulb, but they have a virtually unlimited life (MTBF over 10,000 hrs) so you will never need another one.

The difference in the two versions of LED bulbs concerns the bean width. Teh taxi lights have a much greater beam width. In your case though I would suggest you only need the landing light version and can leave the taxi light with a GE 4509.

One other thing. GE bulbs coem in 100 and 250 watt versions. The usual practice is to use the 250 watt for the landing light and the 100 for the taxi light. However the 100 watt bulb, while not great, is good enough for a landing light and of course draws less power.

[Strega]

Battery has nothing to do with it...

your battery is there to start the plane, excite the alternator/generator, and in the event of a failure of the charging system, allow you to keep some electrical capacity.

The battery has quite a bit to do with it actually. From experience, I've traced probably 90% of widespread electrical faults back to a battery, whether it be corroded connections, low electrolyte, or sulphur contamination from sitting without a charge for too long. These same batteries had enough juice to crank over the starter (which doesn't care too much about voltage) but would make radios go apeshit at lower RPMs when the generator kicks out (because radios are very sensitive to voltage).

Batteries are always the first thing you check...

so are you saying you should be operating off of the battery when flying a night?

I don't understand why people insist on changing their batteries whenever they die, and then need to be charged on the ground with a charger..
If the battery has the jam to start the plane cold.. its fine,, period,, end of story... if the same battery dies when flying,, your charging system needs help..

[Big Pistons Forever]

If you want to know the theory of how something works ask an engineer, if you want to know how to fix it, ask a maechanic.....

[Posthumane]

One reason to consider the LED bulb is the fact that the power consumption can be up to 80% less than a conventional filament bulb. This alone may make your power troubles go away. They are very expensive compared to the GE 4509 bulb, but they have a virtually unlimited life (MTBF over 10,000 hrs) so you will never need another one.

The difference in the two versions of LED bulbs concerns the bean width. The taxi lights have a much greater beam width. In your case though I would suggest you only need the landing light version and can leave the taxi light with a GE 4509.

One other thing. GE bulbs coem in 100 and 250 watt versions. The usual practice is to use the 250 watt for the landing light and the 100 for the taxi light. However the 100 watt bulb, while not great, is good enough for a landing light and of course draws less power.

The lower power consumption is exactly why I was considering the LED bulbs. The teledyne 165k Cd bulb draws only about 30W or power, so just under 3A on a 14V system. The light output is slightly greater than the 100W incandescent. I believe in the 172s (at least the older ones like mine), both bulbs 100W. I think they are also the same bulb on the 172, so they do not have a greater beam width as I would expect they would, but I imagine that most systems do have that difference between them.

I think in the older 172s having the taxi light replaced with an LED bulb would be more beneficial as that is the one you can leave on all the time. You can't have the landing light on by itself since they are on the same switch (stop 1 = taxi light, stop 2 = both lights).

BTW, while LEDs do have a very long MTBF, they can fail pretty quickly when subjected to excess heat. Proper bulb design incorporating lots of heat sinking is essential.

[Strega]

If you want to know the theory of how something works ask an engineer, if you want to know how to fix it, ask a maechanic.....

here we go again.....

[Heliian]

Generally, the Taxi light will be a more diffused, point more on the ramp and be of lower power, the Landing light will be higher power, pointed more forward and be more focused. You'll notice that some GE bulbs have a clear lens and some have a reflector/diffuser lens. My experience with LED and HID lights have been hit or miss. If you're going to pony up the dough for either, make sure you have a good warranty.

As for the battery, I've spent a lot of time trying to convince pilots/owners that their battery plays a key role in the electrical system. A/C batteries are not made poorly, nor are they light. They need maintenance on a regular basis too. Regular lead acid and sealed RG batteries need to be kept at room temperature and can be destroyed by cold weather. Sitting idle will slowly discharge your battery and if you're not flying at least once a week to charge it, it should be put on a trickle or topping charger. If your battery draws a high load and won't charge fully, you'll be overworking your alt/gen. In any case, electrical systems need to be kept in good order to prolong the life of your alt/gen, battery and wiring. As said in above posts, radios/avionics are adversely affected by low or high voltage.

Mechanics work on cars, AME's work on aircraft.

[Strega]

your battery is there to start the plane, excite the alternator/generator, and in the event of a failure of the charging system, allow you to keep some electrical capacity.

Can someone here tell me what other role the battery has on an aircraft?

[SeptRepair]

Battery location can sometimes be strategically engineered to be installed in certain areas for weight and balance issues. So my answer is Ballast.

[Strega]

Battery location can sometimes be strategically engineered to be installed in certain areas for weight and balance issues. So my answer is Ballast.

Interesting remark,,

But Ive yet to see an airplane without an electrical system have a battery installed as ballast....

[niss]

Acting as a capacitor to provide stable power if there are any issues with the alternator or voltage regulator.

[corroded_camshaft]

Do you need an STC or any other paperwork to replace a filament bulb with an LED/HE one? Is this something that could fall under elementary maintenance? I assume even the landing light falls under the definition of a light bulb?

(17) removal and replacement of fuses, light bulbs and reflectors;
(amended 2004/03/01; previous version)

[Big Pistons Forever]

Do you need an STC or any other paperwork to replace a filament bulb with an LED/HE one? Is this something that could fall under elementary maintenance? I assume even the landing light falls under the definition of a light bulb?

(17) removal and replacement of fuses, light bulbs and reflectors;
(amended 2004/03/01; previous version)

LED: No STC if no modifications to the bulb holding ring is required (Since LED's require a heat sink on the back of the bulb some may be too deep to fit in the existing bulb holder). However at least one of the current offerings is dimensionally identical to the 4509 bulb

HID: Yes STC required due to the requirement to install a remotely mounted power pack.

[Strega]

Acting as a capacitor to provide stable power if there are any issues with the alternator or voltage regulator.

Every wondered why there is an overvoltage protection circuit?

Just so you know, a lead acid battery is a poor capacitor.