cessna 172 landing light

[Heliian]

The battery is a storage unit and acts like an accumulator, I think that's what he meant by capacitor.

[CID]

strega, why are you beating the battery issue to death? You've sort of come full circle. A battery in fact is an excellent capacitor. It stores an electrical charge and it absorbs transients. niss is exactly right. Over-voltage protection is an entirely different issue. Believe it or not, batteries are capable of shunting high amplitude short period transients than over-voltage protection systems can.

In many larger aircraft where the battery is just on board to start the APU, complex transient protection systems are installed to perform the role of the missing battery.

In addition to the stabilizing effects, batteries are installed in airplanes so they have a convenient portable energy source to start the engines. Since they have to lug around that weight, it's placed in the most strategic place for the role of the aircraft.

I do see what strega is talking about somewhat. I've witnessed several instances of people continuous charging their batteries because they think it's a normal activity. They somehow miss the fact that if their battery keeps dying, the charging system may be the cause. So I somewhat disagree with the idea that the battery is the first thing to check. It's the charging system.

A simple voltmeter check to see if the voltage at the battery transitions from the quiescent state (12 or 24 volts) to the charging voltage (about 14 volts or about 28 volts depending on the aircraft model). Some aircraft prescribe higher charging voltages in cold whether. The twin otter for example prescribes 29 volts.

Once you've established proper charging voltage, then turn your attention to the battery.

Back to the original question, the landing light and taxi light have different roles. The taxi light (obviously) is supposed to illuminate the area in front of the airplane. The landing light is supposed to give you visibility to the tower. Both are typically the same power rating but the landing light needs to be more directional and intense in a focussed beam so that ATC will only see it if you're lined up and from far away.

The taxi light needs to have broader coverage so the lens is equipped with a diffuser that spreads the available light over a larger area and downwards. Yes, there is a "top" and "bottom" on a taxi light.

If your airplane has the same part number lamp in both positions, you have a crappy mechanic.

[CID]

Also, with respect to the need for an STC, Whelan has an STC in place for most small aircraft. FAA STCs for "small" aircraft are automatically accepted in Canada without review. Look in to STC SA02212AK. You can find the details on the FAA RGL site.

http://rgl.faa.gov/

[Strega]

A battery in fact is an excellent capacitor

Care to back that up?

[CID]

A battery in fact is an excellent capacitor

Care to back that up?

A capacitor stores an electrical charge and blocks DC current. So does a battery. Batteries tend to hold much greater charges of electrical energy than the average capacitor and they have a higher internal resistance than capacitors so there are some differences in behavior. Battery construction and the method in which they hold a charge is generally different although all the main components have parts corresponding to the main parts of a capacitor, namely negative and positive plates (many capacitors aren't polarized) some sort of dielectric insulation and sometimes an electrolytic chemical to enhance the storage abilities.

the design is optimized in batteries are optimized to store large amounts of energy, and capacitors are optimized to keep the internal resistance to a minimum. There are various design tweaks for each device depending on the intended role.

So yes, batteries are excellent capacitors. But maybe you want degrees of "excellence". A battery is a better capacitor than a cat is a better dog but but a capacitor is not a better battery than a screwdriver is a better chisel.

Short of directing you to a series of links on the internet which may or may not be authoritative to your liking, that's all I got. If you don't agree, so be it.

[Heliian]

If your airplane has the same part number lamp in both positions, you have a crappy mechanic.

Depends on the A/C. Some have the same light bulb, just pointed in different directions or have a diffuser covering the taxi bulb. Everything else you were saying was spot on though.

[Strega]

Cid,,

Ever wonder why there arent lead acid batteries in powersupply circuits? amplifiers? a lead acid cell or battery is a POOR capacitor.

A battery stores electrical energy chemically.... A capacitor stores electrical charge.

There is a big difference.

[CID]

strega, that's not entirely true. Electrical systems that require transient protection or temporary storage of electrical energy may use capacitors, batteries or some other transient protection. You state that you don't see power supplies with batteries but in reality, they are not the primary choice since capacitors are optimally designed as DC filters (as I mentioned before) and are less expensive. If you happen to have a battery in the supply circuit already, you tend to require less DC filtering at the lower frequencies.

So it's not a case of looking for batteries in use in power supplies, its a matter of the degree of added capacitor filtering required if no battery exists.

With respect to "chemical" reactions, ALL flow of electricity is a chemical reaction by definition. If you mean that "chemicals" are exclusively the domain of batteries (not capacitors) might I remind you of the closest capacitor analog to a battery, the electrolytic capacitor. Boric acid or sodium borate in a water solution is commonly used. There are also many solvent based formulations used.

If you are instead referring to the differences between plate and electrolyte chemistry in live versus dead battery, and in comparison to capacitors, keep in mind that there are many types of batteries. In nickel cadmium batteries for example, the electrolyte is not consumed or transformed during charge and discharge. Only the plates are chemically altered. The electrolyte is merely an aid to the process. Much like the electrolyte in an electrolytic capacitor.

In lead acid batteries, the electrolyte is consumed and the plates are transformed but the resulting chemical activity results in the same fundamental state. Charging causes an abundance of electrons on one plate and a depletion on the other. Just like a capacitor.

One interesting thing to consider is that capacitors are often used in sensitive circuits to act as little reserves of electrical energy (like a battery) to prevent circuits from malfunctioning during momentary power loss. Many people experience that with their alarm clocks that don't have to be reset if power only goes off for a few seconds. Of course if you want protection for more than a few seconds, use a battery. They are energy reservoirs that are optimized for capacity.

It's the reciprocal to your "power supplies with batteries". A capacitor can act like a battery in some cases just like a battery can act like a capacitor.

[iflyforpie]

strega and cid


I would like to know how on earth you would check the health of a charging system when your only method of activating it is dead? Yeah, I suppose that if you really wanted to you could hand prop a 172 or plug in a later or more sophisticated aircraft, but I still stick with my story and deal with the battery first even if there is something very obviously wrong with the charging system. You are going to need a fresh battery anyways...

[avionicsdude]

A battery and a capacitor are the same in many ways but are also very different as well. Both store an electric charge, but the battery creates electrons through a chemical reaction and a Capacitor just store electrons. Capacitance of a Battery is probably the most important function of a battery and it also one of the most important/common checks an aircraft mechanic does.

A batteries main function is to start the aircraft and power the aircraft while the engine is not running. The Aircraft should not be consuming battery power while your engine is running as the aircraft should be running on the generator/alternator. Your generator should be able to power everything on your aircraft (and then some) while your engine is running. Every aircraft manufacturer has to do an Electric load analysis which basically can calculate how much power your aircraft consumes and it takes into account constant running systems ie Avionics, lights etc as well as occasional systems like flap motors etc. I would check your Generator as it is probably weak, or you might have to go with a more powerful one. Check the voltage regulator as well if your Gen checks out. I would rule out battery just because you are having most of your issues in flight (but unless I see it I cannot tell you for sure)

Strega is right for the most part about batteries except for his comment about a Lead acid cell being a poor Capacitor. Lead Acid batteries are probably one of the best batteries out there when it comes to Capacitance. They pretty much always hold their charge and have terrific voltage dampening properties. In comparison, a NiCad battery (the only other one really used in Civil Aviation) loses about 1% of its power daily.
It is a 4509 bulb. How often does it blow? I would get an Engineer (sorry AME for some people on this thread!!!!) to look at it and do some proper troubleshooting. Landing lights blow all the time and not necessarily from voltage issues....try wrapping a couple of layers of Fuji/Silicone tape (or electrical tape) around the rim of the bulb as vibrations cause them to fuse as well. Cessna actually has a gasket part number for the bulb!!!

[Strega]

Avionics dude..

Can you compare the discharge/charge rates (time based) of a lead acid battery and or a electrolytic capacitor?

Can you tell me what happens when you charge a capacitor constant current? Ok what about the lead acid battery?


PS Just throw the generator away and buy an alternator kit.. about eight hundred bucks as spruce... makes all these problems go away.

PS from my memory the old delco generator should make its rated output at 1750 RPM of the generator... again from memory the gear ratio to the generator on the O-200 is 1-2.035 so 2 to 1 so anything about 875 engine rpm you should be making full rated output of your generator. (35A if that is what is installed) Easy to check this if you know someone that has a hall effect current clamp.

[Big Pistons Forever]

I have never seen a generator equiped 0200 make "full rated output" at 875 RPM. It takes a least 1100 RPM to extinguish the gen fail light, and that is only with a light load. Substantially more RPM will be required if you have all the lights on. It is the ability of the alternator to generate significant charging rates at low RPM, that prompted the universal move from generators to alternators. If your generator system is working properly you often will still have to manage the load during extended low RPM operations with a high electrical load or the battery will eventually be depleted.

[CID]

Hi avionicsdude, I agree with much of what you say. However, your statement regarding capacitors storing electrons versus batteries "creating" them isn't quite correct. In either device, free electrons from the various componentsmove from one plate to the other through an external circuit.

And yes iflyforpie, you can't troubleshoot the electrical system without starting the airplane but I assumed that was a given. Once you get it started by ground power or by charging/changing the battery, the simplest and most important thing to do is check the charging voltage. Of course you don't want to forget checking the electrolyte levels in the battery before you charge it.

[CID]

Strega, your question about the differences between capacitors and batteries in constant current charge is intriguing but I don't understand your reasoning for that specific question.

The answer basically is that they are very similar during constant current charging. The voltage of the device will rise as a function of time until the operational limitations are exceeded, then they will be damaged.

The specific damage depends on the construction of the device. In the case of the lead acid battery, it will eventually "gas" hydrogen and oxygen and the plates will swell until they short out and it might explode. An electrolytic capacitor would short, overheat and explode.

Of course, although batteries can be charged using the constant current method during servicing, aircraft electrical systems tend to use the constant voltage method which can result in a very large charging current with a dead battery but is overall safer.

On larger aircraft where the battery is only used for starting the APU, (for example) the battery is charged using a specific purpose battery charger that optimizes the charging current to minimize plate warping and other types of damage associated with charge rates.

[kiloindiapapa]

Is there a problem with using the 250 W version of the 4509 as apposed to the 100W?

[hangarline]

Is there a problem with using the 250 W version of the 4509 as apposed to the 100W?

Yes there is. The wiring diagram will specify the correct wattage bulb to use. It is dependent on the fuse/circuit breaker rating and the landing/taxi light switch part number. Cessna basically has some cheesy switches that will fail over time (hence the 5 year replacement schedule now), so don't hasten the process with the incorrect bulb replacement. This thread has taken on a life of it's own, but if you go back to the original question, it was asking what the correct replacement bulb part number is. The answer to that can be found in the aircraft maintenance manual which should be your first choice of reference.

[Ping Wu]

I bought a Whelen Parmetheus Parmetheus PAR36 LED light for US$210 at the Air Venture this year. It is a drop in replacement for the standard landing light and it is STC'd. I am using it on my C150 and it is working great. There's a 2 year warranty on it. It's just amazing!

They have 2 versions, the landing light and the taxi light. The taxi light has wider beam but doesn't go as far. The landing light goes a farther away but not as wide.

http://www.whelen.com/_AVIATION/index.php

[kiloindiapapa]

My plane has an upgraded panel from avionics research with new circuit breakers if that makes a diference. Ill just get the 100 watt 4509. The teledyne Alpha beam or other LED would be nice, just way too much when I can just use a $8.00 replacement 4509.

Thanks or all the help.

[Dr. Mcillicuddy]

The old question, How many half ass engineers does it take to change a lite bulb Looks like at least ten options.

[Posthumane]

Ping Wu - can you give a brief review of the light? how is the subjective brightness compared to a regular incandescent 4509 bulb?

Edit: I just looked in my maintenance manual, and apparently the stock generator in the early 172's was a 20-amp unit. The 35-amp generator was an option. I'll have to check which one I have, but if it's the 20 amp unit then it's certainly not surprising that the battery isn't charging when in landing configuration. Even at full power the generator would be hard pressed to keep up with 2x100W landing/taxi lights, position lights, beacon, radio, xponder, etc.

[kiloindiapapa]

Finally got my 4509. A buddy had to pick it up for me out of town. No one I stopped at had it in stock. I guess they are only a 25 hour life. Maybe the LED is the way to really go.

[Ping Wu]

Ping Wu - can you give a brief review of the light? how is the subjective brightness compared to a regular incandescent 4509 bulb?

Edit: I just looked in my maintenance manual, and apparently the stock generator in the early 172's was a 20-amp unit. The 35-amp generator was an option. I'll have to check which one I have, but if it's the 20 amp unit then it's certainly not surprising that the battery isn't charging when in landing configuration. Even at full power the generator would be hard pressed to keep up with 2x100W landing/taxi lights, position lights, beacon, radio, xponder, etc.

Sorry for the late reply.

Check out the following link...

http://www.avweb.com/avwebflash/exclusi ... 313-1.html

Also, Aviation Consumer did a review on LED lighting and it was published in the Oct 2010 edition.


LED Landing Lights: Worth the Expense

These products have multiplied and improved since we last examined them.Top picks are AeroLED’s SunSpot and Whelan Parmetheus.

By Paul Bertorelli

http://www.aviationconsumer.com/issues/ ... 057-1.html

In case you haven’t noticed, the compact fluorescent bulb—once the darling of the green energy set—is dead meat. It’s soon to be displaced by cheaper, brighter and more efficient light emitting diode technology. The same has happened in automotive lighting and many new light sport aircraft have LED nav and landing lights. Legacy certified aircraft would probably have more LED technology too, if the FAA hadn’t worked so hard to chill the market by raising expensive certification

Pictures hardly do justice to the difference between the Q4509, left, and Whelan’s taxi light, right. The 4509 is brighter and has longer reach, but its narrow beam misses the fringes. Tle LED is a cooler blue, with fewer harsh shadows and a wider,more balanced beam.
hoops.

Nonetheless, a few hardy companies have created LED products—landing and taxi lights and nav lights—for the aftermarket. The market has actually expanded slightly since we last examined these products a year-and-a-half ago. Moreover, we expect to see more products for the certified market during the next couple of years, mirroring the emerging trend in all segments of the lighting market.

For this report, we tried seven LED products, all but one being pitched as landing or taxi lights. Our impression is that companies have improved the performance of LEDs to the extent that they’re no longer just curiosities. However, they remain expensive—as much as

20 times more than an incandescent bulb intended for the same application. However, even at those prices, a LED landing light might make sense for some owners.

LED Tech

Recent breakthroughs in LED manufacturing have brought prices down, improved efficiency and output and also increased the range of colors the lamps can output. Unfortunately, the industry standard GE 4509 PAR 36 that the vast majority of airplanes have as landing lights is neither the most reliable nor best bulb going. (PAR refers to parabolic aluminized reflector and the 36 is actually the lamp diameter expressed in increments of 1/8 inch, thus the PAR 36 is 4.5 inches in

All LEDs have rear-mounted heat sinks to protect the diodes from overheating. The trick is make them shallow enough so that a replacement lamp is no deeper than the 4509 it replaces. Whelen managed this in the Parmethus, above. All but one of the LEDs are polarized, but Teledyne’s Alphabeam, mi ddle photo, is not. AeroLEDs SunSpot, lower, sports five leads, allowing installation as a flasher or wig-wag.
diameter.)

Five of the lights we tried were PAR 36 equivalents, more or less. It’s more or less because although the diameters are the same as the 4509, the depth may not be, due to the LED heat sink on the back that keeps the diodes from frying. This is a sensitive point that Whelan’s Jeff Argersinger says must be explained and it’s the reason that brightness measurements alone don’t tell the full story about LEDs.

One characteristic of LEDs is that they can be driven harder to produce more light and some designs do exactly that. To keep the LEDs from burning up, a larger, more efficient—that may mean deeper—heat sink is used on the back of the lamp.

That means it may or may not fit the same mount that housed the original 4509. The selection of lamps we tested were all of varying depths and all but two were deeper than a 4509. The exceptions—Whelan’s 12 LED Parmetheus product, which is actually ½ inch shallower than a 4509 and the AeroLED SunSpot. The Laminar Flow vproduct, depending on how it’s mounted, might also be shallower than a 4509.

In our estimation, the LED lamps in this group are likely to fit most applications, especially if the space behind the existing conventional lamps is open and unobstructed by the mount hardware.

Before buying any of these products, we would advise asking the manufacturer about what specific applications have been directly tested and, if there’s any

doubt that yours is among them, ask about return policies. We doubt if any companies would refuse returns on lamps that don’t fit.
Approvals

This is a sticky point for LED re- placements, although it shouldn’t be. The FARs are utterly open-ended about lighting requirements for light aircraft. Here’s the entire spiel from FAR 23.1383: Each taxi and landing light must be designed and installed so that: (a) No dangerous glare is visible to the pilots. (b) The pilot is not seriously affected by halation. (c) It provides enough light for night operations. (d) It does not cause a fire hazard in any configuration. (Halation is the undesirable spreading of the light beam.)

Seems simple enough, but all the LED manufacturers told us that various regional FAA Aircraft Certification Offices have nonetheless dreamed up additional testing requirements and at least one has both refused to provide an approval path while also declining to provide suggestions for a test program that would yield such a path.

Moreover, landing light bulbs are not TSO’d—although strobes are—and it’s not

clear that a PMA of any kind is required to replace a bulb. Whelan is, nonetheless, planning an STC approval process for its Parmetheus bulb.

AeroLED told us some of its products have been installed under Form 337 approval but also noted that some FSDOs have refused to approve this. For its Alphabeam, Teledyne is pursuing a PMA, even though the 4509 it replaces doesn’t have one.

Frankly, since there’s no clear guidance prohibiting it, we would be inclined to simply install the bulb as though it were a 4509 and let the cards fall where they may. Here’s a summary of the products we examined.

Teledyne Alphabeam

Teledyne’s Light and Display Products specializes in advanced LED lighting systems for various industries. It got into the landing light game the same way other companies have launched aviation products—someone on staff was a pilot and saw an opportunity.

Teledyne engineer George Panagotacos is a pilot and operator of an aircraft maintenance shop with his brother and saw a way to leverage the company’s expertise in LEDs into the aviation business. The divisions launch product is the Alphabeam, a highly engineered direct, drop-in replacement for the GE 4509.

Panagotacos told us that the Alphabeam’s light pattern is almost identical to the 4509 but more symmetrical and slightly broader. We see this as a good thing, because at 6 degrees of width horizontally, the 4509 is considered somewhat over- focused—it’s like looking at the dark world through a toilet paper tube. The Alphabeam—and other LEDs—address that, at the slight expense of not having the distance punch.


A principle challenge in designing effective LED landing lights is focusing the light output and balancing beam width against distance focus. The Alphabeam does this through technology called total internal reflection, or TIR. This method surrounds each LED emitter with a sophisticated reflector system that aims emissions from four-LED groups into a cogent whole.

Temperature control is also a critical issue with LEDs and relates directly to light output. The Alphabeam has a robust heat sink, making it ¼ inch deeper than a typical 4509. (4509s actually vary a little, depending on manufacturer.) The device has a peak draw of 45 watts at any voltage between about 10 and 40, but typically runs at about 35 watts.

As its temperature rises, the bulb’s thermal protection circuitry folds the power output back to protect the LED junctions, although it’s unclear if this make a visible difference in light output. Teledyne says the projected lifetime of the lamp is a minimum of 5000 hours. (During our tests, the Alphabeam’s heat sink got too hot to handle, as did most of the lamps.)

It’s non-polarized, so you can’t fry it by incorrect polarity. Retail price of the Alphabeam through Aircraft Spruce is $325 and it should be available later this year.

Whelan Parmetheus

Whelan has been in the aircraft lighting game since 1952 and its rotating beacons are all but the industry standard. Whelan has a rapidly expanding line of LED products and not just in aviation.

It has its own version of TIR in a new product called the Parmetheus which, like the Alphabeam, is intended as a direct 4509 replacement. It’s available in both landing light version with a 10-degree beam and a spreader taxi version with a 40-degree beam.

What’s most noticeable about this lamp is its size—it’s only 1.75 inches deep, so it’s more compact than the 4509 it replaces. That means it ought to fit any mount, with no interference. Whelan projects a 10,000-hour operating life for the Parmetheus and it carries a three-year warranty, meaning it’s essentially a lifetime bulb. It’s available from Spruce in 14- or 28-volt versions for $239 to $268.

AeroLEDs


When we last examined LEDs, we complained about an over wide beam width that spread the light too much to make out distant detail. So AeroLEDs sent us a new product, with a narrower beam and it reports it will soon introduce new products that are brighter still.

The product we tried—the 16-LED SunSpot—is intended as a combination landing/taxi/recognition light, which qualifies it as the most feature packed of all the products. (At $469.50 from Spruce, it ought to be.)

Where the other lamps have two or three leads, the SunSpot sports five. It can be configured as a landing light, a single flashing recognition light or, if used with another SunSpot, a wig-wag setup. At 1.25 inches deep, it’s the shallowest of the lamps we tried and ought to fit about any mount.
Other Options

Of the three other products we tried, only one is intended as a 4509 replacement. That’s the 12-LED lamp from Laminar Flow Systems. We don’t have a price on this yet, but it also includes a flashing function and, uniquely, a cooling fan to force air through the heat sink.

Also from Spruce is a $529 product called the Electronic Landing Light, a German-made unit intended for the experimental or LSA market. At 3 inches in diameter, it’s too small for the 4509 mount but might be useful elsewhere. It has a blinding, attention-getting red flasher that will leave you seeing spots.

Last, we took a look at a new LED wingtip taxi light package from Malibu Aerospace. This is a developmental product intended solely for Piper’s PA-46 line. It’s priced at about $1700.
Field Trials


The graphic on page 13 shows how we set up our test range. While brightness is not the final arbiter of LED effectiveness, it’s not irrelevant, either. And bluntly, measured against a Q4509, the LEDs hardly hold a candle , so to speak. But the 4509’s brighter beam is also hot yellow and narrowly focused, so it misses illuminating things you’d want to see—perhaps a deer darting across the runway or the protruding tail of an airplane.

LEDs are typically in the 6500 Kelvin range—much bluer—than the 2500 Kelvin of incandescent bulbs. This produces an effect closer to daylight and although objects may not stand out more, they’re easier to resolve, in our view. Viewed from the business end, they stand out better in sunlight as a recognition light and especially conspicuous when flashing.

Moreover, the 4509’s sharp-edged spotlight misses things outside its illumination cone, making it a terrible taxi light. All the LEDs we tried had a broader beam and illuminated things the 4509 missed at a slight expense of distance illumination.

Ranked in brightness, the Laminar Flow led the group, with the Whelan Products and AeroLEDs in the middle and the Alphabeam and Electronic Landing Light trailing. But perceived brightness, well, that’s a different story. You can see a barely noticeable difference between the brightest and dimmest bulbs, but we can’t honestly say it’s much of a distinction. The diminutive Electronic Landing Light appears hobbled by its small size and, in any case, it’s suitable only for experimental aircraft.

Conclusion

We like these products and even though they’re expensive, we think they deliver value through their longevity, flexible beam width and favorable color temperature. Because they’re so much more expensive than conventional incandescents, we think the right way to look at them is as always-on recognition systems that double as landing lights, not the reverse. Even if you fly only in daylight, these products deliver benefits. If you fly under 50 hours a year, justifying the expense might be a reach.

Our top price-is-no-object pick is the AeroLED SunSpot, since it’s bright and includes a flasher. If we’re going to have LEDs, we want the flasher option. The Laminar Flow is a good pick, too, but it isn’t in production yet. The best value option without a flasher? Hands down, it’s Whelan’s Parmetheus. It’s a good performer at a reasonable price and its small size means it will fit any mount.