Bravo power surging and egt's/tit climbing

[toomany]

flew the bravo for an hour and a half this morning and about 1/2 hr into the flight i noticed the tit running away past 1650° then coming back down. i went through all of the egt's and they were doing the same thing - i enriched to keep tit around 1550-1600 but could notice a significant reduction in power. map stayed constant and didnt fluctuate. there were a few moments when the power reduction was coupled w a slight stumble or miss. i was in cruise at 29.5/2380 19.1gpm at 6000' the entire flight. once in the pattern i reduced power accordingly for landing amd didnt notice any surging - i might add that at the end of the flight, last 45 min. i was full rich, map 28.5 and 2850 rpm's. switching tanks made no difference, turning on boost pump made no difference, wagging the wings to dislodge and particulate or water made no difference. mag check pre flight was normal. aircraft has a surefly mag and had performed flawlessly since its install until now. my guess is it sometging in the fuel servo allowing air into the fuel but i can't explain why it would decrease in power then return to set power on occasion. when power would return to set power egt's/tit would could quickly into the high 1400's. any help is greatly appreciated.

 

 

Sent from my iPhone using Tapatalk

[aviatoreb]

That’s very concerning - perhaps grounds for having diverted immediately and sort it out on the ground.

[Boilermonkey]

I suggest looking at the fuel and turbo systems.   That should not happen and could be a symptom of either system.

[toomany]

its having fuel servo diaphragm inspected as well as turbo compensators. im thinking servo diaphragm may be the issue. turbo amd compensators were redone by tornado alley 400 hrs ago.


Sent from my iPhone using Tapatalk

[Steve Skinner]

Happened to me 

same same

faulty mag.

when 1 dropped I got exactly your experience.

It was an intermittent fault 

[toomany]

thank you Steve - I'll pull the bendix mag and have it bench tested.
Did you also get higher egt's and tit?


Sent from my iPhone using Tapatalk

[N201MKTurbo]

You should do an  inflight mag check when it does that. One mag it should run smooth with higher EGTs. The other mag the engine will intermittently quit. Then you should run it on the good mag and adjust your FF accordingly. And land as soon as practical.

BTW. almost certainly re-adjusting the points will fix it. No need to overhaul it.

[Steve Skinner]

45 minutes ago, toomany said:

thank you Steve - I'll pull the bendix mag and have it bench tested.
Did you also get higher egt's and tit?


Sent from my iPhone using Tapatalk

Yes increased tit and egt.

because of the high power I didn’t really notice rough running like you would with a mag check.

i didn’t think to do one at the time - more interested in keeping the engine in the safe range and getting home - 200 miles out in the sticks when it happened.

 

 

 

Happened to me 

same same

faulty mag.

when 1 dropped I got exactly your experience.

It was an intermittent fault 

[kortopates]

It could only be ignition or mixture. Got any engine monitor data?


Sent from my iPhone using Tapatalk

[Shadrach]

I hope it’s a mag as that is the easiest and least expensive solution. The symptoms fit nicely to an intermittent ignition issue. 
As @N201MKTurbosays it’s always prudent to do an inflight mag check when odd EGT symptoms occur. The only reason to avoid an inflight mag check is if you suspect the results will scare your  passengers.

If this was a fuel issue, I would expect some small fluctuations in MP.  Also, did the increase EGT/TIT excursions have an effect on CHT?

If this was fuel related I would expect an increase in CHT. If it’s ignition related, I would expect to see somewhat diminished CHTs.

[LANCECASPER]

19 hours ago, toomany said:

 flew the bravo for an hour and a half this morning and about 1/2 hr into the flight i noticed the tit running away past 1650° then coming back down. i went through all of the egt's and they were doing the same thing - i enriched to keep tit around 1550-1600 but could notice a significant reduction in power. map stayed constant and didnt fluctuate. there were a few moments when the power reduction was coupled w a slight stumble or miss. i was in cruise at 29.5/2380 19.1gpm at 6000' the entire flight. once in the pattern i reduced power accordingly for landing amd didnt notice any surging - i might add that at the end of the flight, last 45 min. i was full rich, map 28.5 and 2850 rpm's. 

From the Bravo POH:  Redline is 2575 RPM continuous on that engine. 
 


 
If it was an overspeed and you ran it continuously the last 45 minutes of your flight at 2850 RPM it will require a teardown inspection. 
https://www.lycoming.com/sites/default/files/attachments/SB369S%20Engine%20Inspection%20after%20Overspeed.pdf

 

Regardless if whether it was 2850 or not, you experienced an Emergency today. When the only engine in an airplane starts running rough - get it on the ground. It reminds me of a flight N. of Atlanta in 1999 with a friend of my who had been an aircraft mechanic for 40+years. We both felt the engine stumble a bit on my first Bravo. I looked at him and asked, "What do you think?" Without skipping a beat he said, "I think I see a runway." We landed at KPDK and spent the night and found out the next day that I had a bad mag. The moral of the story - find the nearest airport and figure it out on the ground.
 
 

[Shadrach]

11 hours ago, LANCECASPER said:

From the Bravo POH:  Redline is 2575 RPM continuous on that engine. 
 


 
If it was an overspeed and you ran it continuously the last 45 minutes of your flight at 2850 RPM it will require a teardown inspection. 
https://www.lycoming.com/sites/default/files/attachments/SB369S%20Engine%20Inspection%20after%20Overspeed.pdf

 

You experienced an Emergency today. It reminds me of a flight N. of Atlanta in 1999 with a friend of my who had been an aircraft mechanic for 40+years. We both felt the engine stumble a bit on my first Bravo. I looked at him and asked, "What do you think?" Without skipping a beat he said, "I think I see a runway." We landed at KPDK and spent the night and found out the next day that I had a bad mag. The moral of the story - find the nearest airport and figure it out on the ground.
 
 

I read 2850 as a typo.  Unless he rolled into a split S and pointed it straight down, the fine pitch stops are going to keep any excursions over red line to a minimum. 

[LANCECASPER]

5 minutes ago, Shadrach said:

I read 2850 as a typo.  Unless he rolled into split S and pointed it straight down, the fine pitch stops are going to keep any excursions over red line to a minimum. 

I have a habit of taking people at their word .. lol

[LANCECASPER]

4 hours ago, toomany said:

thank you Steve - I'll pull the bendix mag and have it bench tested.
Did you also get higher egt's and tit?


Sent from my iPhone using Tapatalk

You won't find a Bendix mag on this engine. Your remaining mag should be a Slick 6300 series. How many hours on your right mag?

[toomany]

rpm's were at 2350 not 2850 - that was a typo. The factory mag will be gone over today - the mag may very well be the issue and it sounds more and more like that is the case. plugs were pulled yesterday and there was abnormal amounts of carbon at the 12o'clock position which coincides with no fire there. I didnt consider a mag check while airborne - i'm sure that would have proven worthwhile. ill post here what we find out on the mag. thanks to all for the input.


Sent from my iPhone using Tapatalk

[aviatoreb]

Is it all cylinders?  How's your spark plugs?  Bad spark by a tired or otherwise bad spark plug can cause EGT to rise and roughness.

[LANCECASPER]

1 hour ago, toomany said:

rpm's were at 2350 not 2850 - that was a typo. The factory mag will be gone over today - the mag may very well be the issue and it sounds more and more like that is the case. plugs were pulled yesterday and there was abnormal amounts of carbon at the 12o'clock position which coincides with no fire there. I didnt consider a mag check while airborne - i'm sure that would have proven worthwhile. ill post here what we find out on the mag. thanks to all for the input.
 

Although you do have to find the cause of what happened yesterday, the first question I would be asking myself today is, If the engine was running rough and I was getting surging in power, why didn't I land? 

When you get some time read over this accident from 2021 where a pilot keeps on flying even though he has an engine problem:

 

[toomany]

thank you Lance, i really appreciate that - the engine wasnt running rough and i could tell by the consistencies in egt's/cht's as well as oil pressure/fuel pressure that the engine's internal health was fine. if there were outliers i would have considered putting it down. also, if i was over heavily wooded terrain or a densely populated area i would have elected to divert. However, when i initially observed the abnormalities in temps i was over densely wooded mountainous terrain w LIFR below me. The last thing i wanted to do was shoot an approach to mins under these conditions knowing that if it was fuel related a power setting change could severely alter the engine performance. i elected to try for pittsburgh and eastern ohio where i would have long runways and good coverage - once there, the situation was not getting worse and i had plenty of flat open fields beneath me and vfr. my destination was a mere 14 min past youngstown and i kept altitude until i knew i could make the field. given the set of circumstances i dont think i would have changed anything. thanks again for your input.


Sent from my iPhone using Tapatalk

[FoxMike]

I have had a problem like this and found replacing the TIT probe solved the problem.  The TIT probe works harder then the EGT probes so wears out faster.

[Shadrach]

7 hours ago, FoxMike said:

I have had a problem like this and found replacing the TIT probe solved the problem.  The TIT probe works harder then the EGT probes so wears out faster.

How would a faulty probe cause the engine to surge? Oscillation in the TIT reading sure.  Oscillation in power?  Not so much.

[LANCECASPER]

Sidepoint: TIT probes are a regular replacement item with the Bravo. If the previous owner has flown it too hot the TIT probe burns up fast (within a couple hundred hours). Then your TIT reads too low, so now you are running it too hot also, which leads to cylinder and exhaust failures. The best few hundred dollars to spend after purchase is on a new TIT probe so you have a baseline. 

[kortopates]

it’s very common that i have to advise a new Bravo owner that they need to replace their TIT probe. TIT probes last on average 500-1000 hrs before they will begin to under indicate temp since they suffer from tip erosion. The continuous hot exhaust gases literally burn off the tip over time. Not problem with EGT probes because they only get exposed to a puff of exhaust when the exhaust valve opens unlike the TIT. The problem though is the owner may never know they’re operating outside of normal TIT guidance wrongly thinking their TIT is very low, but TIT is more commonly 50-100F above your EGTs.


Sent from my iPhone using Tapatalk

[Shadrach]

I think the recommendation to ensure he’s getting a good TIT reading is valuable. However, his original post stated that all EGTs were rising and falling with TIT. Surely not ever probe in the exhaust decided to fail at the exact same time and in the exact way. It seems clear that there is something going on with the combustion event. New probes are not going to change that.

[toomany]

fixed the issue on the bravo - it turns out the surefly mag we installed last year failed. sent unit back to the mfr and was told a red wire broke loose on the circuit board. I was disappointed to learn that the mag was faulty after only approx 200 hrs of use. I will say that surefly had great customer svc and was very thorough on troubleshooting. I had to order and pay for a new mag replacement and send in the one of the mooney. if a fault was determined through bench testing i would keep the new mag and surefly would issue a refund check - which is exactly what happened. havent gotten the refund chwck yet but im sure its on its way.
as an aside - if anyone is looking for a very thorough ia in the east/mid west, chris at kpov in eastern ohio is fantastic and very reasonable. i would highly recommend him. also very familiar w mooney's.


Sent from my iPhone using Tapatalk

[wombat]

I'm glad you found the problem and got it fixed and nothing was damaged and nobody hurt!