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I know it’s not a Mooney but I do own one


RLCarter

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Went up 2 weeks ago in the Mooney for a late afternoon flight, was going to head over to the 3rd Coast (Gulf of Mexico) and as I turned East I noticed the back of my prop was shiny, back at the hangar I had 1 blade spitting grease. San Antonio Propeller picked it up last week and will deliver it tomorrow all freshened up, so the Mooney will be back in the air…Here’s the problem that is not a Mooney, went up last Saturday in my buddies 172 and everything was as normal as always, older 172 with a Conti 0-300D. Had flown around for over an hour doing some slow flight, 8’s on pylons and chandelles and a few lazy 8’s and headed back to do a few Touch-N-Goes, 10 miles out I did a practice emergency descent from 4500ft to1500ft, VSI was pegged at 2000fpm at 3000ft I advanced the throttle just to make sure and all was good, leveled off at 1500ft a flew back to the airport. Just before I entered the 45 for a left downwind I started my before landing check (not much on a 172), just before entering the downwind mid field I pulled the carb heat on, pretty much still at cruise power (it’s a 172), abeam the numbers power was reduced to 1700rpm, turn base I added some flaps, and turning final I added more flaps, approach was stable and smooth. At one point I added maybe 100rpm on final due to wind but pulled it back out 15 or so seconds later, landing wasn’t bad, but while cleaning up the flaps and carb heat I applied the throttle and the engine would not accept anything and died. I coasted to an old taxiway and tried to restart the engine but no joy, didn’t even try to fire, nothing, just cranked. I got out and pulled the drain for the Gascolator, which had fuel. I removed the keys and rotated the prop several full revolutions, engine was building compression and I could hear both impulse couplers release. I tried to start it again but the same thing, crank but not even a hint of wanting to start, after being towed back to the hangar I looked up in the cowl and verified that the Throttle, Mixture and Carb heat cables were still attached and working. By now 20 minutes had past since it died on roll out, tried starting again with the same results, I intentionally flooded it and tried one last time, nothing, so in the hangar it went. Monday I removed the cowls and looked around, A&P/AI looked around, started at the Gascolator, fuel line and the carb, nothing found but 100LL, pulled it out Tuesday morning and it fired right up (I really wish it hadn’t), I let it warm a bit and did a run-up, mag drop was 50 aside and carb heat had a 75rpm drop, taxied around, did several more run-ups and a full throttle static and everything was normal. There is no engine monitor, so no data to go back and check. The cowls are all back on and tomorrow I plan on a few high speed taxies and if those go well a few keep it ground effect hops (6000ft runway) and then fly several thousand feet above the airport and see how it goes. Several of the locals that hang around are leaning towards carb ice that just didn’t clear…looking for any suggestions from the masses, I hate throwing parts on things and hope it cures it, I’ve always wanted to find the problem and fix it, if you know what I mean

 

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I must be local...

Verify there is heat with the carb heat...

The test you did verified that air was being brought through the carb heat system... but does not verify that it is getting heated...

Missing a particular hose, may cause the problem... 

without an engine monitor... it would help to have a thermocouple that you can put in place...

It’s possible, the C172 doesn’t like that you fly a Mooney...   :)

PP thoughts only, not a mechanic...

Best regards,

-a-

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58 minutes ago, carusoam said:

Verify there is heat with the carb heat...

Missing a particular hose, may cause the problem... 

It’s possible, the C172 doesn’t like that you fly a Mooney...   :)

Getting heat, the 172G has 2 mufflers, carb heat is from the left side, cabin heat from the right

All scat hoses were replaced less than 50 hrs ago, all still in place and correct and secure

it's possible, but I fly the 172 more than the Mooney and I figured that's why the prop on the Mooney started spitting grease...lol

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It really sounds like ice in the carb...

Especially with the ‘fixed itself’ mode on the following day...

With the added detail of maintenance on the carb heat...  it sounds like something is blocking the hot air flow, or some of it...

Without a carb temp gauge...

Do whatever it takes to make sure the carb heat system is working as designed...

A carb temp gauge is an awesome device... most M+S carbs have a port to add the sensor...

Nothing like the feeling of pulling the carb heat control and waiting... wondering if it is working.... then wondering if the sound of water being ingested is really water, or the engine is in its last throws...

Look for really strange things like a Shop towel that was put in to keep dirt out... or loose hose clamps... or hoses going to the wrong place...

Around here the other day... somebody found their carb heat system was connected to the generator cooling duct...

Last year JP got his carb heat system terribly altered by an unknowing mechanic...
 

Something odd enough to kill the engine... usually leaves tracks.

MS experience has shown... don’t assume the system was put back together without checking the details yourself...

PP thoughts only...

Best regards,

-a-

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48 minutes ago, carusoam said:

It really sounds like ice in the carb...

Especially with the ‘fixed itself’ mode on the following day...

With the added detail of maintenance on the carb heat...  it sounds like something is blocking the hot air flow, or some of it...

Without a carb temp gauge...

Do whatever it takes to make sure the carb heat system is working as designed...

Nothing like the feeling of pulling the carb heat control and waiting... wondering if it is working.... then wondering if the sound of water being ingested is really water, or the engine is in its last throws...

Look for really strange things like a Shop towel that was put in to keep dirt out... or loose hose clamps... or hoses going to the wrong place...

Something odd enough to kill the engine... usually leaves tracks.

MS experience has shown... don’t assume the system was put back together without checking the details yourself...

Kinda leaning toward carb ice, even though carb heat had been applied before even entering the pattern. I've had carb ice several times in this aircraft, twice at cruise power right as I started to cross the bay headed to S. Padre Island just off the coast in the Gulf of Mexico. Every time in the past it was obvious as it ingested the ice, this time no notice. I have several hundred hours in this plane and has always shown a 75~100 rpm drop when carb heat is applied

There was moisture that morning and I had just gone from 4500 to 1500 ft to get below the clouds 5 minutes earlier . Another thing was an oddity a few months back, while doing my run-up I was getting a 50rpm rise when the carb heat was applied, I left the harb heat on for sometime and tried it several more times, same results RPM gain so the flight was scrubbed and the cowl was pulled but nothing was found and has been normal for the past 10 hrs or so, until this past Saturday 

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1 hour ago, RLCarter said:

Kinda leaning toward carb ice, even though carb heat had been applied before even entering the pattern. I've had carb ice several times in this aircraft, twice at cruise power right as I started to cross the bay headed to S. Padre Island just off the coast in the Gulf of Mexico. Every time in the past it was obvious as it ingested the ice, this time no notice. I have several hundred hours in this plane and has always shown a 75~100 rpm drop when carb heat is applied

There was moisture that morning and I had just gone from 4500 to 1500 ft to get below the clouds 5 minutes earlier . Another thing was an oddity a few months back, while doing my run-up I was getting a 50rpm rise when the carb heat was applied, I left the harb heat on for sometime and tried it several more times, same results RPM gain so the flight was scrubbed and the cowl was pulled but nothing was found and has been normal for the past 10 hrs or so, until this past Saturday 

Here is an interesting article that might apply to your situation concerning the RPM / manifold pressure rising when you apply carb heat.

https://aviation.stackexchange.com/questions/3313/why-does-manifold-pressure-increase-when-you-turn-on-carb-heat

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1 hour ago, Yetti said:

Plugs tell a story.  Saturday was cool enough to do the carb ice thing.  Does the Carb heat actually work?

Down here it was bumping 90°, the 172 has 2 doors in the airbox, pulling the carb heat "ON" closes the door between the air filter and carb and opens the door behind the carb allowing air from the heat muff to enter, as far as I can tell it works as designed. With the engine stone cold (right after start up) carb heat has no effect on RPM, with in a few minutes I get a 75~100 RPM drop as it should, so I'm going to say the carb heat is working.(?)

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Carbed Conti's can be real ice makers due to the placement of the carb versus Lycomings as you know.  Everything you described points to carb ice.  Sometimes it gives you a warning, sometimes not.  I've had both.  In the no notice situation, the engine stopped after full power had been applied for at least 15 seconds on a touch and go.  Took forever for the ice to clear even when it was 80+ degrees.  Engine simply would not restart until a lot of ice had cleared even with the carb heat on.

William

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Carb Ice seems to be where most (MS and locals) are pointing and I agree. The thing I'm having trouble with is the carb was dry (no sweating) and was hot to the touch after 20 minutes, and still no joy. A local said he had a Cessna 180 do the same thing twice in one day and he attributed the no starting due to water being ingested and shorting out (fouling) the plugs.... Just trying to cover all my bets before going up :D

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The added information... flying below the clouds...  this is where RH is very high...

Proving the carb heat system to be working properly...  demonstrates there is still room for improvement...

 

The dangers of scud running...

  • the pilot is stuck between the ground and the clouds...
  • close to the clouds, the RH is high... close to the ground... can have trees...
  • On warm days, the amount of moisture in the air is even higher than cold days at the same RH...
  • The Venturi design of the carb can drop the temp of the air below freezing...
  • evaporating fuel aids the temp drop...
  • max power can still generate carb ice... even in an M20C...
  • if flying near gross weight limit, near max power may be needed to maintain altitude...
  • carb ice starts to block the airflow into the carb limiting power...
  • limited power causes the plane to descend...
  • adding carb heat often constrains the airflow, along with the heated air being less dense...
  • the engine ingesting the melted ice, messes with the thermodynamics of the combustion...
  • power gets robbed by generating steam... this lasts until the moisture clears...
  • Also consider what happens with the mixture /fuel ratio as air gets limited...
  • when the ice and water finally clear everything returns to normal...
  • max power, pilot climbs back into the high RH zone and the cycle begins again...
  • Too much carb heat... not enough power is available to maintain some altitudes at MGW...

 

Sooo... some engines are know as ice makers....   Mooneys are not typically one of those...

The best modern defense against carb ice is to have a carb temp probe...

the pilot gets to add just the right amount of carb heat to avoid ice... maximizing power available... while eliminating ice...

Be familiar with using partial carb heat without a carb temp sensor... this is a set-up for major ice blockage... once the carb gets blocked enough...the engine can’t generate enough heat to clear the carb... engine stops running and won’t restart...

Even though its not a Mooney, and RLC wasn’t scud running... the probability of carb ice was quite high...

It takes the engine producing max heat, and the carb heat system fully on to reliably stay out of the icing range.

Forward looking solution... get carb temp gauge.   It will let you know the carb heat system is working as expected, while you are flying...

 

PP thoughts only, not a thermodynamicist, just a fuzzy memory of flying with three people to SnF... fully loaded, planned to fly 50miles beneath clouds to get to clearer weather...

Best regards,

-a-

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44 minutes ago, carusoam said:

The added information... flying below the clouds...  this is where RH is very high...

-a-

It's south freaking texas where the RH is always high.    Opening day of deer season is usually done in shorts and a t shirt.

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Did a high speed taxi with no issues, taxied back and stayed maybe 5ft agl with no issues so they say the 3rd time is a charm, took off and climbed at Vto 500ft then Vy to 1000 ft, flew a fairly tight pattern, all was good. well except for a Citation that called a 5 mile final, after I called base and final, wasnt sure if it was going to die after landing so I landed really really long to give him room. I wish I could say for certain what caused last saturdays hiccup but I cant, will fill with fuel and go fly around saturday or monday and see what happens, for now I'm guessing a bad case of Carb Ice

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7 hours ago, Yetti said:

It's south freaking texas where the RH is always high.    Opening day of deer season is usually done in shorts and a t shirt.

Shorts and a T-shirt is so we can run the AC unit in the deer blind on low

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It sounds like you hadn’t used the carburetor heat during the practice emergency descent and that would add to my suspicions that it was carb ice. I have a 150 hp Lycoming in mine and anytime we power back below about 2000 rpm, the carb heat is on.

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Hey....

Tell us about the practice e-descent...

Altitude range?

Throttle out?

Carb heat on?

Mixture out or in?

preemptive power bursts?


This could be a source of ice as well... as the engine is producing very little heat to combat the carb ice, even on max carb heat settings...

Does the C172 O-300 manuals give any guidance on avoiding carb ice during E-descents...?

Going way back... my primary training... e-descents were interrupted with some bursts of power to make sure the carb wasn’t planning surprises for us...

 

PP thoughts only, not a CFI...

Best regards,

-a-

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33 minutes ago, BKlott said:

It sounds like you hadn’t used the carburetor heat during the practice emergency descent and that would add to my suspicions that it was carb ice. I have a 150 hp Lycoming in mine and anytime we power back below about 2000 rpm, the carb heat is on.

Carb heat was on during the emergency descent, in fact I have a habit of advancing the throttle mommentarly during ANY low power setting because of the icing issues with Conti's

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8 minutes ago, carusoam said:

Hey....

Tell us about the practice e-descent...

Altitude range?

Throttle out?

Carb heat on?

Mixture out or in?


This could be a source of ice as well... as the engine is producing very little heat to combat the carb ice, even on max carb heat settings...

Does the C172 O-300 manuals give any guidance on avoiding carb ice during E-descents...?

 

PP thoughts only, not a CFI...

Best regards,

-a-

Emergency Descents are new to me and are now part of the Private Pilot training. As you know older POH's weren't much better than a "Thank You" card for buying their aircraft (well maybe a little more detailed). The 172 checklist (highly modified from the POH, by the CFI/DPE that use to lease it) for the procedure is "Carb Heat ON, Power to Idle, Airspeed 100 mph and Full Flaps (40°), you are headed down hill quickly (VSI was pegged at 2000 fpm). I was at 4500 ft when I started the maneuver, "cleared the throttle" going through 3000 and leveled off at 1500, its a fun maneuver but I still like Slips better :D. Very little in the POH about carb heat other than you should see an RPM drop when applied, but no mention to how much of a drop. I generally see a 100 rpm drop on the run-up (1700 rpm) and a little less at higher RPM's. I've had carb ice in cruise 3 times, twice in this plane and once in a Cessna 150 (both Conti powered)

 

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  • 3 months later...

UPDATE:

have fown roughly 10hrs since the initial problem with no issues what so ever, that is untill yesterday. Flew around for 45 minutes or so went back and was doing a few touch-n-goes, 3rd or 4th it stumbled very briefly but went full RPM so I went around the patch again. On the next landing had the same issue, elected to taxi back to the hangar. Stumbled anytime the throttle was advanced, got back to the hangar and did a mag check, LH no drop, RH was completely dead, switched back to LH to keep it running and tried again, this time I went ahead a let it die and then tried to restart.......nothing.... Acted just like it did 3 months ago. New mags, hardware and harness on its way

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Stumble when throttle gets advanced....

If you had a carb... your accelerator pump would be suspect...   :)

You have FI... so... what handles the function of the accelerator pump?

All engines need to be able to supply a bit of extra fuel when pushing the throttle in...

What part of the FI system does that?

I could guess... Somewhere is a vacuum sensor on the fuel controller... find the tube that fell off, or is leaking... or got clogged...

PP thoughts only, not a mechanic, not trying to make a quiz, I’m equally stumped... :)

Best regards,

-a-

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Just now, carusoam said:

Stumble when throttle gets advanced....

If you had a carb... your accelerator pump would be suspect...   :)

You have FI... so... what handles the function of the accelerator pump?

All engines need to be able to supply a bit of extra fuel when pushing the throttle in...

What part of the FI system does that?

PP thoughts only, not a mechanic, not trying to make a quiz, I’m equally stumped...

Best regards,

-a-

Spider? Flow divider? I'm guessing too, I still have a carburetor . . . .

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