Perplexing failure mode of a C182 engine
Thread Starter
Perplexing failure mode of a C182 engine
Today I was flying our club's C182 towplane.
Although the alternator seemed to be charging OK, the battery voltage kept dropping off, until the engine wouldn't start. We tried using jumper cables; we could hear the battery contactor closing when the BAT switch was turned on and could hear the starter solenoid engaging upon turning the key, but the engine still wouldn't turn over.
We managed to keep the operation going by hand-propping a couple of times, but prior to the third-time, it was noticed that the prop would not turn backwards!
So we stopped flying. Any thoughts on what has happened? Jammed starter?
Although the alternator seemed to be charging OK, the battery voltage kept dropping off, until the engine wouldn't start. We tried using jumper cables; we could hear the battery contactor closing when the BAT switch was turned on and could hear the starter solenoid engaging upon turning the key, but the engine still wouldn't turn over.
We managed to keep the operation going by hand-propping a couple of times, but prior to the third-time, it was noticed that the prop would not turn backwards!
So we stopped flying. Any thoughts on what has happened? Jammed starter?
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The starter drive on the larger Continental engines is available in two variations. They are both similar in operation, but with unique characteristics. The older original design, if operating correctly, will allow the propeller to be gently turned backward. The newer design will not. Either is okay, if operating correctly, but both are a great risk to the engine on the whole if operated after they begin to fail.
In either case, failure is indicated to an alert pilot by prolonged slipping during the start. They all have a brief slip, as an aspect of normal operation, but if that slip continues more than a second or so, take the aircraft for maintenance at the next possible opportunity. The prolonged slipping is causing the steel clutch spring inside the starter adapter to dramatically overheat, and begin to weld itself to the shaft drum on which it operates. In extreme cases, and depending upon which type of starter motor is fitted, this could cause the engine to drive the starter motor at high speed for a period, which could cause a bizarre electrical problem.
Equally serious, is a starter motor which is too stiff (needs rebuild) or continues to be powered after the pilot releases the start [key]. This situation will equally cause an expensive failure of the drive. The UK CAA got it exactly right requiring an indicator to the pilot that the starter motor was running after release of the [key]. If this is the case, stop the engine, and seek maintenance.
The problem is in either case, eager pilot gets the engine running, and goes flying, forgetting that getting the engine running (including by hand propping) was abnormal. This goes on for many flights, and the failure worsens. Pilot information on this important topic is few and far between, but this is a very expensive failure mode of these engines, and pilots need to know.
The people at Canadian Aero Manufacturing are expert at these starter drives:
Canadian Aero Manufacturing
The ICA found here, is a worthwhile read for maintainers and pilots:
http://www.canadianaeromanufacturing...ringoldica.pdf
In either case, failure is indicated to an alert pilot by prolonged slipping during the start. They all have a brief slip, as an aspect of normal operation, but if that slip continues more than a second or so, take the aircraft for maintenance at the next possible opportunity. The prolonged slipping is causing the steel clutch spring inside the starter adapter to dramatically overheat, and begin to weld itself to the shaft drum on which it operates. In extreme cases, and depending upon which type of starter motor is fitted, this could cause the engine to drive the starter motor at high speed for a period, which could cause a bizarre electrical problem.
Equally serious, is a starter motor which is too stiff (needs rebuild) or continues to be powered after the pilot releases the start [key]. This situation will equally cause an expensive failure of the drive. The UK CAA got it exactly right requiring an indicator to the pilot that the starter motor was running after release of the [key]. If this is the case, stop the engine, and seek maintenance.
The problem is in either case, eager pilot gets the engine running, and goes flying, forgetting that getting the engine running (including by hand propping) was abnormal. This goes on for many flights, and the failure worsens. Pilot information on this important topic is few and far between, but this is a very expensive failure mode of these engines, and pilots need to know.
The people at Canadian Aero Manufacturing are expert at these starter drives:
Canadian Aero Manufacturing
The ICA found here, is a worthwhile read for maintainers and pilots:
http://www.canadianaeromanufacturing...ringoldica.pdf
The first rule with Continental engines is don't fly the aircraft if the starter is not working properly. As STEP pointed out mechanical mayhem is a distinct possibility due to the stupid design of the starter
A fellow I know had a similar issue with his starter. He hand bombed it to get home. When he arrived the engine was making strange noises.
When the mechanic investigated he found the starter drive had disintegrated and bits of metal from the steel starter spring had gone through the engine. 
The damage was extensive including a ruined crank shaft and resulted in a 20 K repair bill.
A fellow I know had a similar issue with his starter. He hand bombed it to get home. When he arrived the engine was making strange noises.
When the mechanic investigated he found the starter drive had disintegrated and bits of metal from the steel starter spring had gone through the engine. The damage was extensive including a ruined crank shaft and resulted in a 20 K repair bill.
Thread Starter
Thanks ST and BPF,
The considered opinion here is that it is probably a charging problem, but in view of the warnings given above, we'll keep her in the hangar and let the mechanic fly to us.
I'll post again when we have an analysis.
I was wondering about that. What's wrong with the good old Bendix gear? Not sophisticated enough? Not enough room to mount a gear ring on the front of the engine?
The considered opinion here is that it is probably a charging problem, but in view of the warnings given above, we'll keep her in the hangar and let the mechanic fly to us.
I'll post again when we have an analysis.
due to the stupid design of the starter
I'll post again when we have an analysis.
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What's wrong with the good old Bendix gear?
Continental and Lycoming designs differ in philosophy in two major ways: Camshaft location (down rather than up) and starter arrangement (internal drive, rather than external). You would not want the huge engine case which would be required to house the ring gear inside at the back of the engine. The Continental engines were favoured for their comparatively sleek front case (with no ring gear) so cowls could be similarly sleek (like those of the C 310). The cost was the need for an internally driven rear case starter.
Continental did use a quasi bendix internal arrangement on the C-85, C-90, O-200, and O-300, with the "pull clutch". Generally, if set up correctly, these work very well, and last a long time with no maintenance. However, if they are set up wrong, they will clash gear teeth, and fill the engine with bits of hardened steel. But this pull clutch lacked the capacity for torque for the biggest engines.
The starter drive adapter is a cunning design, which has the desirable characteristic that in the case of a kick back during start, it may slip, or break the clutch spring, to save damaging something else in the engine which is much more costly. The starter adapter design has only two flaws: It is intolerant of poor maintenance and poor operating technique. The maintenance is well defined and understood by those people who should be doing it. The problem is on the operation side, the planes are not being presented for starter adapter maintenance when they need it.
So operation: Pilots of "key start" Continental powered aircraft. These include the later C-150s, C-180's and larger, and other non Cessna types. If, when you start the engine, there is slipping of the starter (you can hear it running, but the propeller is not turning crisply with it), abandon the start, and have the starter drive inspected and repaired as needed. Do not run the engine any more. Continental and Cessna probably did not think that they needed to say that an aircraft with an engine which cannot be started normally, is not airworthy - so don't fly it! They did not point out this rather self apparent fact, so I will.
Other than for a battery which is simply discharged, do not hand prop Continental powered aircraft when the electric starter will not work. The plane is not airworthy, don't fly it - sorry.
All key start Continentals rely on friction for the starter to work properly. This friction is best obtained within the intended design: A warm or preheated engine, so the oil is not like grease, and an adapter which conforms to the design (not worn out) so the friction is not being obtained with silly amounts of heat created by a slipping clutch spring - by a pilot slipping the clutch during a start until it finally overheats and grabs to start. So those are operational things that the pilot can do to greatly prolong the life of the starter adapter. Failure to do so will be very costly, and probably inconvenient (starters don't fail at home base, if they can fail when you're away!). If you the pilot have the slightest reason to think that after the engine started normally, the starter motor kept running (electrical anomaly) shut down, and ask for maintenance. The other thing to know as the pilot is that it is easy to overheat the starter motor by too much cranking, and this will potentially ruin the starter motor, and risk introducing the stiffness, which will then destroy the starter adapter inner workings. Though it is rarely spelled out, the C 310 I used to fly did - and it's about the same for all starter motors:
Crank for 30 seconds, rest for a minute, crank for 30 more seconds, rest for 5 minutes, crank for 30 more seconds, rest for 30 minutes. All of this is to allow the starter motor to cool.
On the maintenance side, the only really important thing for the maintainer to know that is not published in Continental maintenance instructions, is that overhauling the starter adapter, without also overhauling the starter motor is trouble. Installing some "geared" starter motors (which are Grrrr, PMA approved) can similarly create problems for the adapter. The starter motor must have the mechanical freedom to unwind a fraction of a turn after the engine starts. This allows the starter adapter clutch spring to unwind a little and release from the friction drum on the starter shaft. For newer design starter adapters, this is not so vital, but still a good idea. So a old gummed up stiff starter motor, or a gear reduced one which is stiff will ruin the older style starter adapters (the ones which you can turn the prop backwards with no resistance). The informal way of knowing how any starter motor will work with the older style starter adapters, is to turn the drive tang on the starter motor by thumb and finger - if you can turn it this way, you're probably okay. If too stiff, due to age/condition, or being geared inside, don't use it on the engine.
All that said, a well maintained system is entirely reliable, and a fine design. At least you can hand prop one if you run your battery flat (which I have done several times on carburetted 470s and 520s). If you run the battery flat trying to start a Lycoming, a hand prop start is probably impossible, as the Bendix remained engaged, and now prevents a hand start at all.
That's your Continental starter lesson for the day. For more information, I recommend the linked information from Canadian Aero Manufacturing. When it comes to the starter drives in the C-85 thorough O-300, they are similar but different. I won't drift this thread, but know that they require maintenance and proper operation as well.....
Thread Starter
ETOPS,
Here's our "gorilla", towing me back to the hangar! A very interesting character. He used to own a 182, now flies a 185 and part-owns a Stinson 108 (which I flew to Oshkosh in) and a Stinson Gullwing.
He told me he had hand-propped his 182 before, having tested that he could do it, prior to going on hunting trips to back-country strips, with the potential for being marooned. I have only hand-propped four-cylinder Lycomings and Gypsy Majors, so I was a bit dubious about him being able to do it, particularly with a three-bladed prop. However, he did it twice!
This morning when talking to him about ST's and BPF's advice, he did admit that he woke up feeling sore and had to think for a while, about what he did yesterday!
Step Turn,
Thanks for that very detailed write-up. I have flown 182s off and on since the 1970s and this is the first time I've ever heard any of this information about the starter. I am staggered that it is not more common knowledge. You've done the community a great service.
Here's our "gorilla", towing me back to the hangar! A very interesting character. He used to own a 182, now flies a 185 and part-owns a Stinson 108 (which I flew to Oshkosh in) and a Stinson Gullwing.
He told me he had hand-propped his 182 before, having tested that he could do it, prior to going on hunting trips to back-country strips, with the potential for being marooned. I have only hand-propped four-cylinder Lycomings and Gypsy Majors, so I was a bit dubious about him being able to do it, particularly with a three-bladed prop. However, he did it twice!
This morning when talking to him about ST's and BPF's advice, he did admit that he woke up feeling sore and had to think for a while, about what he did yesterday!
Step Turn,
Thanks for that very detailed write-up. I have flown 182s off and on since the 1970s and this is the first time I've ever heard any of this information about the starter. I am staggered that it is not more common knowledge. You've done the community a great service.
Last edited by India Four Two; 24th Oct 2016 at 15:56.
Thread Starter
All's well that ends well.
Our mechanic took off the starter and starter adapter. He confirmed that there was nothing wrong with the starter adapter, which is a big relief, although he did give his personal opinion about the design of the thing!
The starter motor had failed - possibly an internal short, since when the starter relay was energized, the voltage across the starter, dropped to 8 volts.
So thanks again for all the input. I'll be much more aware when starting TCM engines from now on.
The starter motor had failed - possibly an internal short, since when the starter relay was energized, the voltage across the starter, dropped to 8 volts.
So thanks again for all the input. I'll be much more aware when starting TCM engines from now on.
Recently had a problem with a GTISO 520 engine starter. The starter motor internally broken, LAME hadn't seen that before. Ended up replacing not only the starter but also the starter adapter. COST $AUD 9,000 on exchange, but cheaper than a bulk strip.
As a side note the LAME, to get us home, hand propped this 435HP engine. I thought he was mad until he explained as a geared engine a small turn equated to a large turn internally.
Even after 40 years flying you learn something new every time you fly.
As a side note the LAME, to get us home, hand propped this 435HP engine. I thought he was mad until he explained as a geared engine a small turn equated to a large turn internally.
Even after 40 years flying you learn something new every time you fly.
Thanks - and could you include a picture of your tame Gorilla - the one you have trained to prop a six cylinder Conti
Low compression. I've hand swung one several times. No problem.
Thread Starter
Slight thread drift
When hand-propping the 182, we tried using single magnetos.
I noticed, for the first time ever, that the positions on the ignition switch are not labelled OFF - L - R - BOTH - START as would be logical, but OFF - R - L - BOTH - START.
Why is that?
I noticed, for the first time ever, that the positions on the ignition switch are not labelled OFF - L - R - BOTH - START as would be logical, but OFF - R - L - BOTH - START.
Why is that?
It lets you start on the left mag (impulse) before going to BOTH. On many aircraft, when using the key as opposed to hand swinging, the START position disengages the right mag, re-engaging it as it returns to both.
A lot of pilots don't know that, or why.
A lot of pilots don't know that, or why.
Last edited by Flyingmac; 27th Oct 2016 at 08:06.
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Some engines with two magnetos are configured with one impulse, and the other not. At the very slow starting RPM, the spark from a regular mag can be weak, so the impulse coupling gives it a little extra umph. The spark timing is also retarded during the start so that the spark hits the fuel/ail near top dead center, rather than 20 something degrees beforehand. If the spark ignites the fuel/air 20 something before TDC, it really sets you up for a kickback, which can be damaging to the starter system.
Some engines have two impulse mags, but if not, you'd rather that the non impulse mag not fire "early" and completely defeat the desirable retard effect of the impulse mag during a start. Once RPM picks up, this feature automatically disengages. Key start switches are (should be) wired to accommodate this.
It is unfortunate that topics of this secondary nature get glossed over, if mentioned at all, during ground school, and during flying. Instructors themselves probably have not come to understand these system details, and students don't know to ask. Thus the value in new pilots, and particularly owners, actually seeking out this knowledge about the aircraft they fly.
Coffee and sticky buns at the maintenance hangar can open doors of great wisdom to pilots....
Some engines have two impulse mags, but if not, you'd rather that the non impulse mag not fire "early" and completely defeat the desirable retard effect of the impulse mag during a start. Once RPM picks up, this feature automatically disengages. Key start switches are (should be) wired to accommodate this.
It is unfortunate that topics of this secondary nature get glossed over, if mentioned at all, during ground school, and during flying. Instructors themselves probably have not come to understand these system details, and students don't know to ask. Thus the value in new pilots, and particularly owners, actually seeking out this knowledge about the aircraft they fly.
Coffee and sticky buns at the maintenance hangar can open doors of great wisdom to pilots....
Thread Starter
I know about impulse mags, although it is surprisingly difficult to find out which mag on a particular type has the impulse coupling.
My question was more about the order of mag selection. Given that the key turns clockwise, I had always assumed, without looking, that the order was OFF - L - R - BOTH. However I now know that it is OFF - R - L - BOTH. This seems illogical.
My question was more about the order of mag selection. Given that the key turns clockwise, I had always assumed, without looking, that the order was OFF - L - R - BOTH. However I now know that it is OFF - R - L - BOTH. This seems illogical.
And something I flew (Robin? Firefly? Can't remember!) was set up with a separate starter button, so you set mags to L, started, then turned mags to Both. Same reason
India Four Two. Read posts 14 and 16 again. The logic is there.
