The International Cessna^® 170 Association

I have an early SN# 170B with piano hinge switches. The switch for the landing light is only an on/off switch. When the switch is in the on position both lamps in the wing come on. Is this the normal operation and I need to change it to get a taxi light position on a new switch or is there something wrong with my particular piano switch? I would love to be able to work the bulbs independently.

The piano switches operate a common toggle behind them. You might install a two-position toggle to accomodate dual positions. (see the AN3027 series switches at http://www.aircraftspruce.com/catalog/e ... itches.php )

You might also enable one of the unused piano keys by installing a switch behind it, if you have any unused spares.

Thanks George !

I currently have one unused switch so will use that for now.

Update to all

As much as some may be reluctant to admitt, Ol George is a wise man in this regaard. I have made the switch and am very pleased.
I have shared with George, My son is also taking lessons right now so the increase in time in the traffic pattern promted my first question in this thread.
Hence the change. I was up Thursday night shooting some touch and goes and found the 60w was plenty for taxi and the 4509, when needed, was great for landings. It would be safe to say we have 20+ hours on the 60w and has not burned out. I would have replaced the normal one by now forsure. Both my son and I will pop on the taxi right after our 10 mile call, in bound. I have been up in another plane when my son was up in ours and I can pick out the 60w taxi at a good distance away during the day time which serves our purpose anyway.

I'll keep you updated as time goes, or until George comes up with something "NEW" ......

I have an old piano key switch panel up in my hangar. I'll check it to see what kind of switch it has.Iseem to remember it as being a 1P2T

gahorn wrote:The piano switches operate a common toggle behind them. You might install a two-position toggle to accomodate dual positions. (see the AN3027 series switches at http://www.aircraftspruce.com/catalog/e ... itches.php )

I like this idea George. The switches back there are already double throw switches. Cessna restricted one throw with a "j" shaped piece of aluminum. (Switch limit clip, p/n 041889, fig. 39-19) One could remove the clip and install a DPDT switch (AN 3037-1 or MS 35059-21). Attach the landing and taxi light wires to the top two lugs and run a jumper from the lug with the taxi light wire to the bottom lug on the same side. When you push the piano switch down you'll get both lights and when you flip the switch up past center you'll get the taxi light.

If one is short of switches for stuff like pitot heat or strobe lights and doesn't want to add ugly switches to the panel you could follow the above method--either with a DPDT or SPDT switch depending on what you need. For example, you probably never need pitot heat and strobes at the same time. Pitot heat could be set to go on with the switch in the up position and strobes in the down position. One could also have nav. and strobe lights in one position and just nav lights in the other position (for taxiing).

gahorn wrote: I have a surprise solution for all my critics here which I'll soon reveal in the coming weeks.

George I thought your solution was going to be along the lines of Neal Wright's of the 120-140 association. He has an informative article on this subject: http://www.cessna120-140.org/forum/viewtopic.php?t=2137 Here's one of his ideas:

I have Neal's article and it's a really nice piece of work. He makes an error or two (he refers in a couple of instances to lamps which are actually 28 volt not 14,..... but who among us is perfect?)
......Overall a great article!
His suggestion of adding a computer cooling fan to cool the Q-Lamps is not something I would endorse, and I'm not fond of the idea of drilling ventilation holes in the plastic lens either. But his article is very informative and addresses the issues quite well.

I'm working on another article/solution I hope to have ready soon.

DPDT (Double-Pole, Double-Throw) switches are a good solution to this problem with the early piano switches. As n2582d points out, there are six terminals on the back side of the switch... two sets of three. The center terminal of either group of three would be wired "hot" and an upper or lower terminal of the group would feed the switched power to the (taxi) lamp. If a short jumper were connected across to the the other (upper/lower) terminal of the group-of-three..... then the switch would send power to the (taxi) lamp in either the UP or the DOWN position, but would be OFF in the center position.
The parallel group-of-three would have HOT power to the center terminal, and only ONE of the upper/lower terminals carrying the power to the second (land) lamp. In this fashion, with the switch in the CENTER position both lamps would be extinguished, and with the switch in one of the UP or DOWN positions only a Taxi lamp would light, and with the switch in the opposite position, BOTH taxi & land lamps would illuminate. (I suggest that the switch in the DOWN position should be for Taxi (ground operation is DOWN) and with the switch in the UP position the LANDing lights (both) should illuminate (as in UP for Flight).

On most of the piano key swirch panels I've seen, all of the installed switches were double throw and those using a single throw only were equipped with a limiting clip. To change a switch or remove a limiting clip is a bearcat of a job. If you need to change a switch from single throw operation to double throw, the easiest way is to get up in there and straighten out the limiting clip so that the toggle san move either way.
If anyone needs one, I'm putting a piano switch set up for sale on the Trade Mart.

My "48" had all dpdt switches. I wired landing - up [both] and taxi - down. This way I don't blind someone when taxing.

John

The H7604 lamp works well and is inexpensive. It's 100 hours, 50 watts, and is only slightly less bright than the 4509 (100000 vs 110000cp). It does have less horizontal spread than the 4509, so it can be annoying when used as a taxi light, but it's good for anticollision.

Another lamp life-extending idea I've seen is to put a 0.1 ohm resistor in series with the landing light. It will drop about 0.75V, greatly extending lamp life, at the cost of an almost imperceptible loss of brightness. Be sure to use a properly heatsinked power resistor!

Candlepower is a misleading method of determining relative brightness because it's directly related to the "beam" or focus of the reflector and lens. Wattage is not linear, so it's not necessarily true that a 50Watt lamp is half of a 100Watt lamp. One must compare the beam width, wattage, voltage, to draw a comparison. Just FYI. See the pdf GE catalog I uploaded and one can see the relationships.
Halogen does not always guarantee brighter light either, as the catalog will demonstrate, plus it operates considerably hotter and can prematurely blacken the reflector, so may result in a disappointment as well, but generally Halogen bulbs will last longer between ultimate burn-out (even if it doesn't produce full brilliance the entire lifetime.)

gahorn wrote:Here's another solution to short taxi-lamp life (if you're primarily interested in using it in the traffic pattern and getting longer lamp life): The original G.E. 4509 lamps have a 25-hour service life. This is because they are operating at the peak of their design output, at 100 watts and 110,000 candlepower, and focuses that beam very tightly which increases it's heat.

If you are using your TAXI position for anticollision purposes, you might consider swapping that 4509 lamp to a 4461 which is rated at 300 hours service life. This will be just as useful as an anticollision/recognition light but will spread the beam wider (30 horiz. X 25 vert. making it more useful as a taxi lamp in my opinion.) It will not make as bright a "spot" because it is a 60 watt lamp, (for comparison, standard auto headlamps are only 55 watts) but it will reduce the electrical load on your system. It will be every bit as useful in the traffic pattern and enroute for recognition. (And it is usually cheaper, typically $10-$12.)

George,
An FAA inspector from our local FSDO gave a Wings seminar this morning on pilot/operator maintenance actions. I asked him about using a tractor headlight (I couldn't remember the lamp number) in place of the taxi lamp, and his opinion was that it would require a field approval (I believe he said because it's not a TSO part), but given the datum that it has 60% of the wattage, current and power consumption of the original part, he would have no problem giving that approval. I think I'll take him up on that, and I'll report back on how it goes.

Thanks for this suggestion! I've already got more hours on my 4461 lamp than any 4509 or equivalent that I've used so far.

I was talking with a mechanic at work this week about how often I have to write up "runway turnoff lights inop" in the maintenance logbook. This guy's been around a while. He said in the old days they would wrap electrical tape around the circumference of bulbs with electrical tape before mounting them. According to him this would provide some shock absorption which extended the life of the bulb. Now, he lamented, they have to follow the maintenance manual to the letter so he can't do this anymore.

I thought this would be a great experiment for George with his super-modified 170 . Wrap the bulbs in the left wing with tape or maybe some thin adhesive-backed window or door insulation. Make sure and use something that can take the heat of the hot bulbs. Leave the bulbs on the right side alone. See if, over a period of years, you actually burn out less bulbs in the left wing.

jrenwick wrote:...An FAA inspector from our local FSDO gave a Wings seminar this morning on pilot/operator maintenance actions. I asked him about using a tractor headlight (I couldn't remember the lamp number) in place of the taxi lamp, and his opinion was that it would require a field approval (I believe he said because it's not a TSO part), but given the datum that it has 60% of the wattage, current and power consumption of the original part, he would have no problem giving that approval. I think I'll take him up on that, and I'll report back on how it goes.

Thanks for this suggestion! I've already got more hours on my 4461 lamp than any 4509 or equivalent that I've used so far.

The GE-4509 lamps which are specified for the location ...also are not TSO'd...so that is not a valid argument. In fact, Cessna specifies many lamps on the airplane which are nothing but automotive lamps. On top of that, there is no required brilliance or light-output for taxi or landing lamps (such as there is for anti-collision lighting) so there is no violation there either. There has been many years of discussions by folks who wish to frighten others into using nothing but GE 4509 lamps etc etc., but the fact is TunSol, Wagner, etc etc are every bit as "airworthy" as GE. Further...if you look at your parts manual, you'll find that your cockpt lamps are ...(are you ready for this?).... Mazda. And that brand no longer is made, so the substitute is GE-67s...or Wagner, or ??? (whatever brand)....common automotive.
Further, FAA has already acquiesced on similar issues, such as common switches, circuit-breakers, fuses, diodes, resistors, etc etc., having come to the same conclusion as the rest of common-sense-thinkers of the world....they are of equal quality if they are standard parts from reputable mfr's.

I would not recommend putting vinyl electrical tape around the circumference of landing/taxi lamps because they generate quite a bit of heat and that tape and it's adhesive will not withstand it. I would consider that somewhat hazardous.