Archer III - Starting and Carb Ice Detector

MachFly

MachFly

En-Route
Joined
Oct 3, 2011
Messages
2,514
Display Name
Display name:
MachFly
Looks like I'll be doing quite a bit of flying in an Archer III for the next few month. Got two operational questions for you guys.

1. Do you use both mags when starting? About half of the info I'm finding on the topic says to use both, and the other half says to use just the left one.

2. It has something called "Carb Ice Detect." How and when do I use it? And I'm even more interested in how does it mechanically detect ice?


Thanks
 
MachFly said:
Looks like I'll be doing quite a bit of flying in an Archer III for the next few month. Got two operational questions for you guys.

1. Do you use both mags when starting? About half of the info I'm finding on the topic says to use both, and the other half says to use just the left one.

2. It has something called "Carb Ice Detect." How and when do I use it? And I'm even more interested in how does it mechanically detect ice?


Thanks
Click to expand...

Use both mags and leave the carb ice detector off since it always says there is carb ice.

The other annoying thing on the Archer III is the "Pitot Heat Off" light. On the Archer III I fly, everyone just leaves that warning light unplugged. Fortunately it is a push button light, so it stays in place while unplugged.
 
MachFly said:
Looks like I'll be doing quite a bit of flying in an Archer III for the next few month. Got two operational questions for you guys.

1. Do you use both mags when starting? About half of the info I'm finding on the topic says to use both, and the other half says to use just the left one.

2. It has something called "Carb Ice Detect." How and when do I use it? And I'm even more interested in how does it mechanically detect ice?


Thanks
Click to expand...

First question for you is: does the engine have two impulse mags or one? If it has two, start with both mags. If only one, start on the impulse mag only.

Why? The impulse mag retards (delays) the spark until the cylinders are at top dead center or a bit later. This delay only occurs at very low rpm like when you are cranking the engine. The result prevents the engine from firing before top dead center which could cause damage at the worst or cause the engine to "kick back" or stet to turn backwards. (engine won't run backwards, but you don't want this to happen). If you have only one impulse mag, and start with both on, the mag without the impulse coupler will fire first negating the benefit of the impulse mag.

I am not sure of your carb ice detect but it may be a light beam that illuminates the carb internally with a sensor. Ice will break the beam. But this is just a guess and I will leave it to others to explain.

-Skip
 
Depends if it has impulse couplings on both (if the base end of the mags looks the same they both do, if one is deeper than the other, start on the deeper one). The easiest way to do an ice detector I can think of is have an open electric circuit with two ends close to each other in the ice breeding zone. Breed enough ice, the circuit is closed, similar to a solid state bilge pump switch.
 
I don't know what types of mags they are, I will try to find out soon. Normally (when it comes out of the factory), are both of them impulse mags?

The thing is the plane is a rental and I don't rent it directly from the owner, so getting information ins't very easy.
 
Last edited:
clear_prop said:
leave the carb ice detector off since it always says there is carb ice.
Click to expand...

Can't you make it a bit less sensitive? The Archer I'm talking about has a sensitivity selector, I assumed that's what it was for.
 
MachFly said:
I don't know what types of mags they are, I will try to find out soon. Normally (when it comes out of the factory), are both of them impulse mags?

The thing is the plane is a rental and I don't rent it directly from the owner, so getting information ins't very easy.
Click to expand...

Mot planes come from the factory with one impulse and one non, or some have a "Shower of Sparks" system. You'll either have one or two. Like I said, look at the mount side of the mag, if there is one with more mag and one with a case looking spacer, you only have one.
 
MachFly said:
1. Do you use both mags when starting? About half of the info I'm finding on the topic says to use both, and the other half says to use just the left one.
Click to expand...
Does that Archer actually have separate mag and ignition switches? The later ones have the Cessna-style integrated switch which takes the problem out of your hands. But if it does have separate switches, then unless it has dual impulse couplers (most unusual), you do want to be on LEFT for start to prevent kickback and trashing the starter/ring gears. The maintenance folks for that plane can tell you for sure if it has the standard single (with which it left the factory) or aftermarket dual impulse couplers.
 
Ron Levy said:
Does that Archer actually have separate mag and ignition switches? The later ones have the Cessna-style integrated switch which takes the problem out of your hands. But if it does have separate switches, then unless it has dual impulse couplers (most unusual), you do want to be on LEFT for start to prevent kickback and trashing the starter/ring gears. The maintenance folks for that plane can tell you for sure if it has the standard single (with which it left the factory) or aftermarket dual impulse couplers.
Click to expand...

Yeah this one has separate switches.

That's my plan, to ask the maintenance guys. I won't see them for a few days, but I'll find out before I go up in it.
 
Henning said:
Mot planes come from the factory with one impulse and one non, or some have a "Shower of Sparks" system. You'll either have one or two. Like I said, look at the mount side of the mag, if there is one with more mag and one with a case looking spacer, you only have one.
Click to expand...

Okay got you.
I don't remember if I can see the mags without unscrewing the cowling, but I'll take a look at them. If they are different, is there a way for me to identify which one is left and right without following the cables?
 
MachFly said:
Okay got you.
I don't remember if I can see the mags without unscrewing the cowling, but I'll take a look at them. If they are different, is there a way for me to identify which one is left and right without following the cables?
Click to expand...

You can use an Ohm meter between the P lead and airframe. Open circuit (infinite resistance) is hot, closed circuit (small resistance) is grounded dead. Put the meter on the long back mag, hit the switch, and see what happens. If you get no difference, turn the engine a bit to open the points.
 
Henning said:
You can use an Ohm meter between the P lead and airframe. Open circuit (infinite resistance) is hot, closed circuit (small resistance) is grounded dead. Put the meter on the long back mag, hit the switch, and see what happens. If you get no difference, turn the engine a bit to open the points.
Click to expand...

Right, that will work.

The cowling is a bit of an inconvenience. It's one of those cowlings that you have to unscrew (not like on most archers). I'll first try to find out from the maintenance guys, if I can't, I'll do what you said.
 
Just pull the prop through. You should be able to tell if you hear one or two snaps from the impulse coupling(s). If you hear two use both to start. If you hear one then odds are that the impulse is on the left.
 
mondtster said:
Just pull the prop through. You should be able to tell if you hear one or two snaps from the impulse coupling(s). If you hear two use both to start. If you hear one then odds are that the impulse is on the left.
Click to expand...

I'll give a try, will see what happens.
I don't normally rotate the prop myself so I'm not too familiar with the sounds I'm supposed to hear. If I can clearly identify it I'll go by that.
 
mondtster said:
Just pull the prop through. You should be able to tell if you hear one or two snaps from the impulse coupling(s). If you hear two use both to start. If you hear one then odds are that the impulse is on the left.
Click to expand...

Unless the mags are timed correctly then they'll click at the same time...;)
 
Henning said:
Unless the mags are timed correctly then they'll click at the same time...;)
Click to expand...

I've seen very few that are timed that perfectly. Pull it through slow enough and you'll likely be able to distinguish two snaps from one.
 
MachFly said:
Can't you make it a bit less sensitive? The Archer I'm talking about has a sensitivity selector, I assumed that's what it was for.
Click to expand...

The one I fly has a sensitivity selector too, but it doesn't seem to do anything...
 
clear_prop said:
The one I fly has a sensitivity selector too, but it doesn't seem to do anything...
Click to expand...

Do you know if that's the same throughout the fleet?

I've flown it only once so far, and couldn't really tell you if mine works or not. Will check it out next time.
 
Assuming it has an O-360-A4M engine and it has not been modified it has one impulse mag on the left. Per the POH start on the left mag or risk a kickback and broken starter. An carb ice detector on a Lycoming is a waste of money since they only ice in extreme conditions. I had ice in an O-360 carb once. It was 32 degrees and raining. I noticed the egt started to decrease so I leaned a bit more. After the second releaning it started to lose RPM. Application of carburetor heat caused a great cacaphony of the engine going through the melted ice and it was fine. One other time I had ice in an O-320-H2AD on a Skyhawk while taxiing. Again conditions were right for carb ice. These two incidents were the only ones in thousands of hours behind carbureted Lycomings. Continentals are a whole different story. Charlie Melot Zephyr Engines
 
The idea that Lycomings can't get carb ice in extreme conditions is false. One need only go to the NTSB data base, type in carb ice and you will get numerous reports. These are just the ones that made it to the NTSB. There are even some that occurred during taxi.
My one encounter with carb ice in a Lycoming was hardly severe.
 
MachFly said:
Yeah this one has separate switches.

That's my plan, to ask the maintenance guys. I won't see them for a few days, but I'll find out before I go up in it.
Click to expand...
In the mean time, remember you can't hurt anything by starting on LEFT even if you have dual impulse couplers. OTOH, you can definitely hurt something starting on BOTH if you only have one on the left mag, and I've never heard of having one on the right but not the left on a Lycoming engine.
 
MachFly said:
I don't remember if I can see the mags without unscrewing the cowling, but I'll take a look at them. If they are different, is there a way for me to identify which one is left and right without following the cables?
Click to expand...
What's different is the collar between the base of the mag and the gearbox case with the impulse coupler gear installed.
 
Ron Levy said:
What's different is the collar between the base of the mag and the gearbox case with the impulse coupler gear installed.
Click to expand...

Don't remember from the top of my head. When I head out there I should be able to find everything out, and talk to the mechanics.
 
Ron Levy said:
In the mean time, remember you can't hurt anything by starting on LEFT even if you have dual impulse couplers. OTOH, you can definitely hurt something starting on BOTH if you only have one on the left mag, and I've never heard of having one on the right but not the left on a Lycoming engine.
Click to expand...

I'll keep that in mind.
 
charlie said:
Assuming it has an O-360-A4M engine and it has not been modified it has one impulse mag on the left. Per the POH start on the left mag or risk a kickback and broken starter. An carb ice detector on a Lycoming is a waste of money since they only ice in extreme conditions. I had ice in an O-360 carb once. It was 32 degrees and raining. I noticed the egt started to decrease so I leaned a bit more. After the second releaning it started to lose RPM. Application of carburetor heat caused a great cacaphony of the engine going through the melted ice and it was fine. One other time I had ice in an O-320-H2AD on a Skyhawk while taxiing. Again conditions were right for carb ice. These two incidents were the only ones in thousands of hours behind carbureted Lycomings. Continentals are a whole different story. Charlie Melot Zephyr Engines
Click to expand...

When you flew with the carb ice detector, when did you have it on? Is it something you turn on on takeoff and turn off when you land?
 
MachFly said:
When you flew with the carb ice detector, when did you have it on? Is it something you turn on on takeoff and turn off when you land?
Click to expand...

What is it anyway, just an Ohm meter set to trip a light?
 
Henning said:
What is it anyway, just an Ohm meter set to trip a light?
Click to expand...
\IIRC I just left it on all the time. In a 182 I used to fly it was necessary to turn the sensitivity way down becasue that installation makes ice to some level any time conditions are even close. I am not sire how it works. I thought the probe had an optical sensor? It screws into the side of the carburetor just above the venturi. Flew a couple of Lycomings with them and don;t recall any activity from them.

BTW on the mag subject it would be highly unlikely any Archers have an impulse on the right mag. Adding an impulse mag changes the model designation of the engine so it would require paperwork to do that then more paperwork to install the different model engine in the airplane.

Charlie Melot
 
Henning said:
What is it anyway, just an Ohm meter set to trip a light?
Click to expand...

That's what I'm trying to figure out. The POH just says that the thing exists, and that's it. I don't have access to a maintenance manual.
 
charlie said:
\IIRC I just left it on all the time. In a 182 I used to fly it was necessary to turn the sensitivity way down becasue that installation makes ice to some level any time conditions are even close. I am not sire how it works. I thought the probe had an optical sensor? It screws into the side of the carburetor just above the venturi. Flew a couple of Lycomings with them and don;t recall any activity from them.

BTW on the mag subject it would be highly unlikely any Archers have an impulse on the right mag. Adding an impulse mag changes the model designation of the engine so it would require paperwork to do that then more paperwork to install the different model engine in the airplane.

Charlie Melot
Click to expand...

When you flew with it, did you keep it on all the time?
 
mondtster said:
Just pull the prop through. You should be able to tell if you hear one or two snaps from the impulse coupling(s). If you hear two use both to start. If you hear one then odds are that the impulse is on the left.
Click to expand...

Not the best advice. Just a sniff of gasoline fumes, a bad P-lead, and someone gets injured or dead.

Dan
 
MachFly said:
Do you know if that's the same throughout the fleet?

I've flown it only once so far, and couldn't really tell you if mine works or not. Will check it out next time.
Click to expand...

I've only have time in the one Archer III so I can't compare it to anything, sorry.
 
The Archer III that I rent has the carb ice detection plac'd as INOP. I'm told, though I cannot confirm, that it didn't actually break, but was so sensitive that it was deemed useless and the owner just had it disabled permanently.
 
I started the Archer III I rented on the left mag, alternator off because that's what the POH said. Good enough for me.
 
Found out today that it has one impulse mag, the left one. Will be starting it from the left mag. Thanks for the help.
 
So did we ever figure out proper use protocol for the carb ice detector and what the sensitivity numbers mean? The POH doesn't say much other than it has one... and Google hasn't been too helpful. I hate the idea of flying with a piece of equipment with which its operation I am unfamiliar with or don't / can't use
 
You must log in or register to reply here.
Back
Top