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Shudder / vibe lasts about 1 second

Bart

Well Known Member
For the second time in 6 months I've had a short duration (less than a second) shudder/vibration seemly from the prop or engine. Nothing comes up (flatline) on the egt or cht strips. There is no RPM change. Both times we were straight and level. Both times was about 5-10 mins after takeoff. Total time on plane about 200. It won't replicate with changes in RPM. MP. Or fuel flow, altitude or AS. Any thoughts?
 
Bart-

If you have a way to download your EMS to a data sheet capturing that time period you might get an indication of what is taking place.

Good Luck,
 
I can download the data. I'll take a look at it later tonight. The power setting was roughly 23 inches and 2200 both times.
 
Bart,

Send me a copy of the engine monitor file. davidbrown 'at' advancedpilot.com

There are a couple of things I can think of that will cause this, and even some rare bizarre things.

Can you also tell me the following;
Stage of flight i.e. just after TOC ?
Plugs: Brand, when were they gapped last.
Mags: Are the Mags or EI's
Fuel: What type are you using
EMS data log time interval
If you can, pin point the exact time these events occur in the data.

I will see what I can see?. :)
 
Well it looks like I had record turned off. So no data to show. With that said there we no anomalies that I caught in the cross check. No change in RPM no change in CHT / EGT. I'm recording now. I hate to chalk it up to a fouled plug but not sure I have much else to go on.
 
It could be many things, getting the data would be good for beginning a diagnosis. Generally, a single plug would work or not work, but not typically a transient misfire, so that is (probably) why David asked for the situation to better narrow the possibilities.
 
Yep, I get that. I've got the EFIS set to record now. Seems weird to have two seconds of events spread out over 6 months but the shudder/vibe is enough to get your attention. The first time it happened I thought I had a bird go through the prop.
 
Bart,

Data lacking, can you please answer my questions as accurately as possible. I may still have some suggestions for you, but I do not want to send you on a goose chase either.
 
Most likely a small slug of water. Fuel injection right? Water will pass right through the system, but of course results in a short series of misfires. Nothing will show up on the EIS record.
 
David


Can you also tell me the following;
Stage of flight i.e. just after TOC ?
- 5-10 mins after takeoff
Plugs: Brand, when were they gapped last
- champion plugs
- annual in oct
- has happened on both sides of annual
- gapped, cleaned at annual

Mags: Are the Mags or EI's
- mags
Fuel: What type are you using
- 100LL
EMS data log time interval
If you can, pin point the exact time these events occur in the data.
Set up now unfortunately not during the last flight
 
Champion

It was stated earlier in this thread that plugs do not generally cause transient problems. Just one data point but I have experienced this exact intermittent symptom with a Champion plug. Mine only broke down under load at cruise power.
 
Light bulb moment. We had a 40 degree temp change this week. I had just refueled. There is a really good chance I sent a slug of moisture through the system. Dang. The previous event may have had a similar temp change as well. The boost pump was off both times.
 
same issue for me

I had the same issue.
First time right after annual ( 400 her with valve cover inspection)

It was just after take off in climb ( maybe 100ft above ground)
Same sensation. less than a second, a sound that look like it was coming from under or in front of the cockpit. Same reflex ( did i hit a bird ? have i lost a wheel?) but no sign of anything.

second time in cruse, level leaning and just arriving at peak, same sound ( low frequency but this time like if the engine miss a beat)

I have a lycoming io-540 by aerosport
one plasma III ignition and one slick mag 6351
i think that my plug are champion but must check
they were clean, and gap and also test with the arcraft tool supply spark plug tester and cleaner and was all ok
My plasma ignition plug are br8es NGK and were gap at 0.032
I am always using 100ll, never found water in tank or gascolator ( check before each flight. I take my fuel at the flight college and the fill a 5000 gal tank twice a week so probably always fresh fuel.

My plane is always in a heated hangar


After the second event, i did a lean of peak mag check.
when i test the mag only , i had to put the mixture a little more rich ( and i think it was normal because less effective than the electronic ignition. Even than, all EGT went higher. On the electronic ignition side, almost no change and very smooth.

My plan, i will send the mag for service as it is near 500 her but don'T think it's the cause because even on the electronic ignition only, i can only really feel a tiny difference if the mag fail. Nothing like the sound i heard.
Is it the electronic ignition?. I will change all my high tension lead, and i ordered the denso plug.

Any Idea.
My EMS is at one second. Nothing noticeable.

Lan Vinh Do
 
Bart, thanks for the reply, Can I assume that you were at TOC after the 5-10minutes and maybe also leaned back to your cruise setting, typically LOP but not necessarily.

The concept of water causing this is plausible but I doubt it. You could check your drains and gascolator but it is a remote chance.

Even using 100LL avgas you will get vapour lock in a low wing aeroplane. Typically this happens climbing through about 6-7000'. The reasons are heat from the engine heating the fuel pump, high angle of the pump relative to the fuel pickup point, reducing ambient pressure on the tank, and even more so if the RVP of the fuel is at the higher end of the spec. And refiners love to get rid of Butane where they can ;).

So in the absence of data showing otherwise, here is my recommendation for all Lycoming systems;
1. Line up, boost pump on, mixture rich and roll.
2. Climb at a sensible airspeed, not Vx or Vy, in the -10 that is 120KIAS through to TOC using a Target EGT method as described by APS.
3. Level out?..DO NOTHING?.as John Deakin would say, an airline pilots favourite thing!
4. Once the plane has accelerated and the CHT's start falling close cowl flaps if fitted (yes I know RV's don't normally have them). then do nothing some more.
5. After a few minutes of doing nothing you will get fidgety, having dealt with ATC, checked your flight plan etc, now set the cruise up by setting say 2400/2436/2372/2490 RPM Yes whatever is a smooth setting for your plane, then do a Big Mixture Pull, and leave it there.
6. Once the CHT's have rolled off a fair bit sneak up to peak FROM THE LEAN SIDE, and find the first one to peak, then roll back leaner and set that to the appropriate amount LOP. Be that 10/25/40/60 or 80 LOP.
7. Another 10 minutes down range turn off the boost pump.
8. Continue the flight until just before TOD do a AMG check for 10-15 seconds on each mag (leave mixture alone) and only touch RPM (reduce to say 2000) on descent, and then throttle only to stay out of the yellow arc, until at the hanger door, shut down with mixture to ICO. Flight over.

Little shudders could also come from a small wire fragment in your connector to the EMS, if you short both tach wires or p-lead posts together?.you get an alarming state :eek: But it is hard to detect without graphing the data log and zooming in. Yes I have seen this before and it was VERY hard to find.

There are others, but with new gear and hopefully well set up, it is unlikely.

Follow the above and report back, and if there is another stutter send me the data file. In fact send me your data after the next flight or two anyway.

Cheers.
 
Lan Vinh Do,

Your mag check LOP sounds normal. With the EI, you will find that the advanced spark timing is allowing you to operate further LOP, which is not really a problem except that you may be less efficient doing that. I can't be sure as it depends how LOP you were.

When you go from one ignition source to the other you need to go back to both for a while to let the EGT's all fall back to normal. Then you can see if they all rise again on the other.

As for plugs, the gaps on the auto plugs?.I do not know for sure but some find a little less is better, but do not take my word for it. On your massive electrode aviation plugs 0.016-0.018" and also if Champion, chef the resistance is under 3000 ohms and if beyond or approaching 5000 ohms, bin them.

It is quite possible you have had vapour lock issues as well.
 
thank you

Thank you David.

Really possible.
If i remember, first time it was after a run up at the end of the annual, without the cowling, took 30 min to put the cowling back and did a flight test after.

second time it was a second flight of the day after 1hre on the ground.

Lan Vinh Do
 
Thanks David, I was in cruise. 23 inches and 2200 RPM. I was leaned but not LOP. More like 50 ROP. The boost pump was off. It was a short flight after refueling although I did extend the flight about 20 mins troubleshooting. No reoccurrence in anything I tried. I now have the EFIS set to record so I'll pass that data if a repeat is in my future. Thanks for your insights.
 
Thanks David, I was in cruise. 23 inches and 2200 RPM. I was leaned but not LOP. More like 50 ROP. The boost pump was off. It was a short flight after refueling although I did extend the flight about 20 mins troubleshooting. No reoccurrence in anything I tried. I now have the EFIS set to record so I'll pass that data if a repeat is in my future. Thanks for your insights.

Bart - do you remember what the fuel flow was for those settings when you had the problem (also engine hp if it isn't listed already)?

One possibility is hysteresis in the mixture control. For example, if you are on the edge of being too lean, and the last mixture movement was towards the lean side, the mixture lever arm could move or rattle towards the lean side of the cable hysteresis travel. I always finish leaning with a tiny move towards the rich side to eliminate that possibility. Just something to think about. The more cumulative bends in the cable, the more hysteresis is available.
 
my recollection is about 12 gallons and 67% hp.

Hi Bart,

I have been following your thread since we talked last week and nothing jumped out at me that has not been mentioned here. Your last post is different from the performance of my 10. Although I have read a few post from others with FF near 11 or 12 I have never been able to lean that low. I am normally at cruise power say 24/23 burning around 14 with cylinder temps around 380 and EGT in the low 1200's.

Pat
 
Hi Bart,

I have been following your thread since we talked last week and nothing jumped out at me that has not been mentioned here. Your last post is different from the performance of my 10. Although I have read a few post from others with FF near 11 or 12 I have never been able to lean that low. I am normally at cruise power say 24/23 burning around 14 with cylinder temps around 380 and EGT in the low 1200's.

Pat

OT, but.....

Pat,

Does your RV-10 have an electronic ignition?

Most of the folks that I'm aware of that are running leaner than you have EI and are running LOP.

I'm getting about the same as you at the moment during my Phase I, but I'm not going to run LOP for awhile due to having a new engine.

bob
 
This may sound kinda silly but I thought I would mention it so the topic is thorough. Try checking your nose wheel break out force. On our -10 we finally discovered after quite a bit of troubleshooting that if it falls much below the recommended 26lbs, it could possibly cause the fairing to shimmy ever so slightly in the relative wind.
 
Good point Bob, I am stock IO540 with mags.

Pat

I too have stock Slick mags and routinely run fuel flows of less than 10 gal/hr around 21" MP (or wide open throttle up high) and 2200 -2300 RPM. Lean of peak, of course. I did exchange some injectors to better match up the cylinders.
 
I too have stock Slick mags and routinely run fuel flows of less than 10 gal/hr around 21" MP (or wide open throttle up high) and 2200 -2300 RPM. Lean of peak, of course. I did exchange some injectors to better match up the cylinders.

My IO-540 has 2 Bendix 1200 series mags, AFP injectors matched to 0.1 gph. At Denver elevations and above, I routinely run WOT, 23-2400 rpm on 10.5 gph.

Jim Berry
RV-10
 
back to vibration

This is most likely not your problem, but:

I would get a "different" sound after attitude changes, power changes, etc. A low frequency vibration. It would only go away after a many seconds, not a few. I finally tracked it down to the inlet air ramp being a little too long (too forward). It contacted not only the flexible baffle, but could, with a tiny shifting of the cowl, contact the edge of the aluminum backing plate that held the rivets that held the flexible baffle. That apparently caused the inlet ramp to vibrate, and maybe the whole cowling too? Anyway, took a 16th of an inch off the inlet ramp, with a file; the problem went away.
 
Hi Pat
Regular mags. 50 degrees ROP with similar temps. 12 gph. Could the flowscan counting be making the difference?
 
Maybe, I will be up there this weekend so if I can help give me a call. We can also get a few of the other 10 owners on the field to give us their thoughts. If your going to the chapter event Saturday night I'm sure we can find a few opinions.

If the engine was running lean the temps would be high so I am pretty sure that's not it. Just different from my engine. I am also under 100 hours and don't lean as aggressively as others might.

Pat
 
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David,

I enjoyed talking with you yesterday on face time and although Johns issue may be different the feedback you provided was appreciated. I will check out the training event in Ada Ok in March and see if I can fly my 10 up there.

Pat

Bart,

Send me a copy of the engine monitor file. davidbrown 'at' advancedpilot.com

There are a couple of things I can think of that will cause this, and even some rare bizarre things.

Can you also tell me the following;
Stage of flight i.e. just after TOC ?
Plugs: Brand, when were they gapped last.
Mags: Are the Mags or EI's
Fuel: What type are you using
EMS data log time interval
If you can, pin point the exact time these events occur in the data.

I will see what I can see?. :)
 
Gentleman,

I am writing this post to correct a few myths and misunderstandings about running in engines, fuel flow and EI's.

First of all, the little bit of advance that makes LOP ops better is in the order of a couple of degrees, however this is only good when LOP, for you ROP guys it is actually less of a good thing especially when running around 50dF ROP.

Fuel flow will vary depending on altitude, but for typical cruise altitudes of around 7500-9500' when running appropriately LOP, will be 11.0-10.5GPH. This is regardless of the type of ignition you are running.

As for breaking in the engine, you want to do this with low peak pressures and high mean effective pressures. This means the break in happens over a wider pass of the piston/cylinder, without the high peak.

Given that we can generate the same torque and BMEP by varying the peak pressure and theta PP, which combination is going to give us better mean effective pressures and lowest peak pressures? Which method is going to give us lower CHT's? Which method is going to give us cleaner rings and cylinders?

If the answer to the above was Rich of Peak run in, I would thoroughly endorse it. However the answer is actually the opposite. So you are far better to run in your engine LOP. Sure at takeoff full rich, but at 1500-2000' a big mixture pull and run in at high HP LOP. The choices are 75% or more power, either full rich or 80dF LOP. Take your pick.

Of course you need to have good F/A ratios in order to do this, and there is no problem doing this on your second flight to determine if you have a good gami spread. If you do not get it fixed and continue flying the phase 1.

This notion that
but I'm not going to run LOP for awhile due to having a new engine.
?. is complete nonsense and at odds with the science and data. It is however consistent with popular belief!

I frequently remined myself during discussions such as these that it's often true that no amount of data can replace the comforts of a closely held superstition.

Below is a photo I post regularly, this would be a perfect break in setup, so long as the air was smooth, or adjust accordingly by going a fraction higher.
80LOP_zps6e22f7f3.jpg
 
My new factory engine with unbalanced injectors runs fine at 30-40F LOP. I doubt any new factory engine will run smooth at 80F LOP for break-in as you mentioned above.
 
Confucius say: Do not tell man something impossible when he already doing it! :D

Wayne your doubts are well founded?.only some of the time.

In my case with a factory Lycoming you would be forgiven for making that satement, it was a shocker, so bad we could not even do a GAMI lean test and had to do some guesses to start with just to get anything near peak EGT.

Yet a year or so later while flight testing another RV10 with a stock factory IO540?..0.2GPH spread and would run happily 80dF LOP at 2000'. I was stunned! An RV7 owner with an Aerosport Power engine down here gets 0.0 spread, it is that good. I suspect that AP did a great job on the dyne before shipping, or they just got lucky.

Wayne, your new engine runs fine 30-40dF LOP, but at what MP and RPM? This varies with power(Altitude). If you can do that at 10'000 feet that suggests a good spread, and chances are at 1000' as shown above you can also run down to 100dF LOP.

30-40dF LOP at 10,000' is vastly different to 1,000'.
 
16,500', DA= 18,370', 16.1" mp, 2430 rpm, 7.9 gph, IAS= 105 kts, TAS= 136 kts, 16 nmpg with a 14 kt headwind, +6 degrees pitch, 225F cowl exit temp(hottest ever), CHT= 307-331F, OAT= 32F, gross weight, near aft cg limit. That is the highest that we have been and it ran smooth 30-40 LOP. Mine does not want to run smooth beyond 40-50F down low. We lose a lot of speed running LOP, so can't imagine wanting to run any leaner. We are very happy with the engine and plane.
 
Wayne, I see your problems.

We lose a lot of speed running LOP

I bet you do!! And this is the problem, lack of education and understanding. A bit like Kevin Horton the other day and the old 50dF LOP SOP thing.

you had a DA of 18000' and at 40LOP it was almost stopped! 10dF LOP and no more. In fact 75dF ROP up there would be better.
so can't imagine wanting to run any leaner.
No doubt at all!

Tell me this, what is your procedure for leaning and setting the LOP cruise setting, and I might be able to help you out.

Mine does not want to run smooth beyond 40-50F down low.
And this is significant, also. I suspect a problem here that can be corrected.

How many hours on the engine?
What plugs do you use?
How long since they were gapped?
How many hours on them?

Can you send me a EMS data file?
 
As for breaking in the engine, you want to do this with low peak pressures and high mean effective pressures. This means the break in happens over a wider pass of the piston/cylinder, without the high peak.

Can you quantify this statement? Cylinder pressure plots or a data table? In numbers, can you show us the difference in pressures (peak and mean) between the two operating schemes?

So you are far better to run in your engine LOP. Sure at takeoff full rich, but at 1500-2000' a big mixture pull and run in at high HP LOP. The choices are 75% or more power, either full rich or 80dF LOP. Take your pick.

You better hope your audience fully understands that at full power, there is a very good chance it is going to detonate in the mixture region between 50 ROP and 50 LOP, and that region may extend quite a lot further with increased compression ratio or advanced ignition. Want to see the chart again?

You're asking the pilot of a brand new, unfamiliar airplane to make a rapid mixture pull to a point close to cutoff, probably with untuned injectors, while close to the ground. Failure to do the Big Pull in a rapid manner (i.e. slowly easing up to peak from the rich side) risks engine damage. Isn't that asking a bit much?

I frequently remined myself during discussions such as these that it's often true that no amount of data can replace the comforts of a closely held superstition.

Take a risk...show us the data anyway.
 
Wayne, I see your problems.



I bet you do!! And this is the problem, lack of education and understanding. A bit like Kevin Horton the other day and the old 50dF LOP SOP thing.Thank you.

you had a DA of 18000' and at 40LOP it was almost stopped! 10dF LOP and no more. In fact 75dF ROP up there would be better.I agree.

No doubt at all!

Tell me this, what is your procedure for leaning and setting the LOP cruise setting, and I might be able to help you out.We lean from 663', flowing 25.6 gph, to our usual cruise altitude of 12,500' at a takeoff EGT of 1250F, 2700 RPM. Once at cruise, RPM to 2200-2450, WOT, pull mixture to get me close noting normal FF of 9.5-10.5 gph(yes, I am always below 75%), then slowly lean using GRT to 30-40F LOP. Typically cruise at 150-158 KTAS.

And this is significant, also. I suspect a problem here that can be corrected.

How many hours on the engine? 125 since Dec 1, 2011 thanks to our great economy.
What plugs do you use?massive on top and fine wire on bottom
How long since they were gapped? 25
How many hours on them? 125 on massive/25 on fine wire

Can you send me a EMS data file?No

Yes, I need to get fuel injectors balanced. Changing to six fine wires gave me another 10F LOP before getting rough.
 
Dan,

Take a risk and show you the data. Sure when you sign a NDA which covers a whole load of things, and you get involved with a certification project that clearly shows everything you could want to know and more, why not!

Simpler option would be pony up with the cash and do the next course in Ada OK and George will show you real live data of the sort you want to see. I have seen plenty of it and quite a lot lately. But that is not for public consumption.

Having said that I can pull some info from the course which are straight from the dyno hard data, or even some of John Deakins old articles.

But let me answer a question or two for you. You asked;
Quote:
Originally Posted by RV10inOz View Post
As for breaking in the engine, you want to do this with low peak pressures and high mean effective pressures. This means the break in happens over a wider pass of the piston/cylinder, without the high peak.
Can you quantify this statement? Cylinder pressure plots or a data table? In numbers, can you show us the difference in pressures (peak and mean) between the two operating schemes?

And took only a small snippet of the message, so let me answer your question with the benefit of my statement displayed for all the others reading silently on the sideline. I will highlight the salient points.
David Brown said..
As for breaking in the engine, you want to do this with low peak pressures and high mean effective pressures. This means the break in happens over a wider pass of the piston/cylinder, without the high peak.

Given that we can generate the same torque and BMEP by varying the peak pressure and theta PP, which combination is going to give us better mean effective pressures and lowest peak pressures? Which method is going to give us lower CHT's? Which method is going to give us cleaner rings and cylinders?

If the answer to the above was Rich of Peak run in, I would thoroughly endorse it. However the answer is actually the opposite. So you are far better to run in your engine LOP. Sure at takeoff full rich, but at 1500-2000' a big mixture pull and run in at high HP LOP. The choices are 75% or more power, either full rich or 80dF LOP. Take your pick.


If you want to see this data for yourself, on the Friday night, this very demonstration is shown between 15min and 17min on the dyno video run. I can't upload that video here, so let me lift the figures for you.

The first Data block I have noted is at peak or just lean of peak, in an attempt to keep the HP the same rather than the reduced power and obviously even lower PSI's. The second is full rich.
1. MP=31" RPM=2400 BMEP 133.9 BHP=219 ICP's ranged 600-620PSI
2. MP=31" RPM=2395 BMEP 136.6 BHP=223 ICP's ranged 750-780PSI



You better hope your audience fully understands that at full power, there is a very good chance it is going to detonate in the mixture region between 50 ROP and 50 LOP, and that region may extend quite a lot further with increased compression ratio or advanced ignition. Want to see the chart again?
Well I think you are misleading the audience, but lets look at those graphs, and no thanks I have a copy. They show a data point at precisely where we teach detonation is most likely to occur. Right around 35-50dF ROP and they draw a line from one data point to another and give you a misleading idea that the detonation is still going on 40-50dF LOP. And that is simply not true.

By the way the Lycoming data comes from a source that is far behind in my opinion the FAA test centre or the GAMI one, they do not use the currently accepted detonation algorithms and that graph you refer to only shows frequency (Hz) of events. It does nothing for intensity and this is the key point. George has demonstrated this on his test stand to the FAA, and it is like asking yourself, in a hail storm which deposits hail on your car, or better still if you are a car salesman with a yard full of cars. And it deposits 1000 hail stones weighing 0.2grams each on your yard. The other choice is 10 hail stones at 20grams each. Which one is going to give your insurance company the shivers? So intensity matters. Frequency not so much.

Your statement above is somewhat accurate in that detonation occurs in the renege from 50ROP to 50LOP, but it is no more accurate than a statement like 200ROP to 100LOP. A truer statement might be something like 75ROP and 10ROP.

So back to the claim that doing a BMP while running in your engine will be running the engine where "there is a very good chance it is going to detonate in the mixture region between 50 ROP and 50 LOP", and how on earth in a few seconds you are going to heat up the oil, heat up the CHT's create 30"MP and 2400 long enough for even one detonation event to take place? I fail to see how that is even remotely possible. For the audience out there, running a conforming engine on conforming 100LL and doing a BMP, even with CHT's over 400dF we have never seen detonation happen and even with purposely driven high oil, air, CHT and the ability to run 33" or more we have not seen this with a BMP.

OK next one,
You're asking the pilot of a brand new, unfamiliar airplane to make a rapid mixture pull to a point close to cutoff, probably with untuned injectors, while close to the ground. Failure to do the Big Pull in a rapid manner (i.e. slowly easing up to peak from the rich side) risks engine damage. Isn't that asking a bit much?
A You're asking the pilot of a brand new, unfamiliar airplane to make a rapid mixture pull to a point close to cutoff No, I am giving the pilot the option, who is at least familiar enough to have already made his first or second flight, the confidence to make a smooth mixture pull through to a deceleration, (easy to feel), and park the engine somewhere safe for a minute, while he determines if he does have good enough fuel / air ratio's. If he does not he will soon know and shove the mixture back in and continue on full rich. At no time is the mixture anywhere near idle cutoff, and I can be sure that if he got that far it would not be for long.
B probably with untuned injectors Probably so, the only way they would have been tuned is if they were done by Aerosport or Riverina or someone on their engine test cell, but it is possible to have decent enough F/A ratio's out of the box sometimes. Maybe this would be a good time to sort that out?
C while close to the ground For the purposes of doing aero's or stalls on your second flight 1500-2000' I would surely call that close to the ground. But to manipulate the mixture knob? Surely you are kidding me. If you or they are that scared they may not have fastened it right to the FCU, do it 2000' above the field.
D Failure to do the Big Pull in a rapid manner (i.e. slowly easing up to peak from the rich side) risks engine damage. I think if you had done any of this even doing it slowly on either the FAA's or GAMI's test cell you would not be so scared and willing to believe the BS Lycoming have printed. Even doing it slowly over 30 seconds is not going to hurt anything. The problem is by doing it slowly is not anything to do with engine harm, it is that you will not feel the deceleration at all when going safely into LOP territory. So the BMP is not any use if it is a SMP.
E Isn't that asking a bit much? No not at all. I suggest you email the editor of the AOPA's Australian magazine http://www.aopa.com.au/magazine and ask her about her first BMP done overwater at 1500' and see how she responds. So all the smarter tougher and more macho test pilots should be able to cope.

Take a Risk Dan??go see the data for yourself. http://www.advancedpilot.com/store.html If you don't learn anything at all, Deakin will write you a cheque.
 
We lean from 663', flowing 25.6 gph, to our usual cruise altitude of 12,500' at a takeoff EGT of 1250F, 2700 RPM. Once at cruise, RPM to 2200-2450, WOT, pull mixture to get me close noting normal FF of 9.5-10.5 gph(yes, I am always below 75%), then slowly lean using GRT to 30-40F LOP. Typically cruise at 150-158 KTAS.

How many hours on the engine? 125 since Dec 1, 2011 thanks to our great economy.
What plugs do you use?massive on top and fine wire on bottom
How long since they were gapped? 25
How many hours on them? 125 on massive/25 on fine wire

Can you send me a EMS data file?No

I will try to deal with each part separately. Your takeoff fuel flow and EGT are spot on, and the use of Target EGT is excellent, that is great, and you are pretty close to best power or slightly richer doing that once you get above say 9000', so the climb rate is maximised and everything is great.

The RPM selection is fine but where I am sure the problem kicks in is best answered by reading my post to Kevin Horton http://www.vansairforce.com/community/showpost.php?p=832950&postcount=23 in that you are going a long way LOP, and if you are doing what you think is 30-40dF LOP at that altitude, and you are running smooth, I would say your GAMI spread is pretty darned good. For better BSFC I would encourage about 10dF LOP at that height and you will get more like 160TAS than low 150's. But I am impressed your F/A ratio's are so good untuned.

Spark plugs sound good??the economy, well I have been doing my best to inject cash into it of recent times. :)
 
I will try to deal with each part separately. Your takeoff fuel flow and EGT are spot on, and the use of Target EGT is excellent, that is great, and you are pretty close to best power or slightly richer doing that once you get above say 9000', so the climb rate is maximised and everything is great.

The RPM selection is fine but where I am sure the problem kicks in is best answered by reading my post to Kevin Horton http://www.vansairforce.com/community/showpost.php?p=832950&postcount=23 in that you are going a long way LOP, and if you are doing what you think is 30-40dF LOP at that altitude, and you are running smooth, I would say your GAMI spread is pretty darned good. For better BSFC I would encourage about 10dF LOP at that height and you will get more like 160TAS than low 150's. But I am impressed your F/A ratio's are so good untuned.

Spark plugs sound good??the economy, well I have been doing my best to inject cash into it of recent times. :)

GAMI spread, balance injectors and running a little richer is on my to do list. Thank you for your advice.
 
GAMI spread, balance injectors and running a little richer is on my to do list. Thank you for your advice.

Hi Wayne, I suspect your injectors may well be fine as they are, you could be one of the lucky ones. If it is 0.5 or better, happy days!

Let me know how you go.

Best regards
 
The first Data block I have noted is at peak or just lean of peak, in an attempt to keep the HP the same rather than the reduced power and obviously even lower PSI's. The second is full rich.
1. MP=31" RPM=2400 BMEP 133.9 BHP=219 ICP's ranged 600-620PSI
2. MP=31" RPM=2395 BMEP 136.6 BHP=223 ICP's ranged 750-780PSI

Now we're getting somewhere. The subject is break-in (post 33, paragraph 4), meaning the goal is to generate ring pressure. When quantified, we see there is no significant difference between knob twiddling on climb out and just leaving the knobs alone and flying the new airplane...except for the much-maligned ICP, the source of combustion ring pressure.

I think if you had done any of this even doing it slowly on either the FAA's or GAMI's test cell you would not be so scared and willing to believe the BS Lycoming have printed.

You the same guy who detonated your 540 and blamed it on a too-short mixture cable?

http://www.vansairforce.com/community/showpost.php?p=549239&postcount=15

I suggest you email the editor of the AOPA's Australian magazine and ask her about her first BMP done overwater at 1500' and see how she responds. So all the smarter tougher and more macho test pilots should be able to cope.

Ahh...even girls do it. Good argument.

I'm going to stick with suggesting that rusty pilots flying their new RV's just leave the knobs alone, fly the airplane, and stay eyes out until well clear of the airport area. LOP is good; learn it in cruise first, and progress to more advanced management later, after sorting out the airplane.

The stats say early test flights are the deadly ones. Let's not make it more complicated.
 
Dan,

You are getting somewhere but missed the point.
Now we're getting somewhere. The subject is break-in (post 33, paragraph 4), meaning the goal is to generate ring pressure. When quantified, we see there is no significant difference between knob twiddling on climb out and just leaving the knobs alone and flying the new airplane...except for the much-maligned ICP, the source of combustion ring pressure.

During break in you want less of the peak and more of a broad area under the curve to give you better break in. The graph below is generated from real data and plotted nicely for classroom use. Take a look at which has a lower peak ICP but a broader and wider range of average pressure. So tell me which is better Dan, a higher MEAN effective pressure or, higher peak pressure? Higher CHT or lower CHT? Cleaner or dirtier combustion chamber and oil? One operation as all the good things and less of the bad. (NB: 80dF LOP would be better, this graphic is produced to show the traditional thinking 50LOP/50ROP comparison. It applies here full rich Vs even 50dF LOP.)
Burntime_zps26258da6.png


As I said before, either do it full rich or 80dF LOP.

You the same guy who detonated your 540 and blamed it on a too-short mixture cable?
Glad you remember that, that incident/s happened with very high inlet temps, and rapidly rising CHT on a few (not all) cylinders and only started with a takeoff with already hot cylinders. Looked all the world like either preignition (i.e. maybe a cracked ceramic) but it was not, or the very mild edge of light detonation. Even to the point we wondered if there was fuel contamination. The data at the time looked like it. As you rightly remembered we found the flex in the bracket from engine thrust and too short a cable was the cause.

I subsequently looked into this with George Braly and we concluded it was not detonation in the true sense as defined by the FAA. It may well have been close and enough to register on the Lycoming test method, but I doubt it. But the CHT rise per second looked almost like it. So today, I would write that post differently.

Ouch!!
Ahh...even girls do it. Good argument.
Proves the point, but she is a pretty sharp operator I guess, so how about an old retired airline guy, took him flying today, got him to do a BMP, never done one before, and exactly like Kreisha Ballantyne he landed bang on target at the appropriate number of degrees LOP. I mean bang on with huh accuracy, and so did Kreisha and everyone else I have asked to do it. Close your eyes and pull back, under two seconds, eyes open.

And here you are complaining about eyes down in the cockpit. Please, the BMP means NO FIDDLING, and maximum eyes outside. In a busy terminal area this is what we teach, no fiddling just a BMP and park the engine in a safe place. Works for turbo or NA guys. Zero downsides. Maximum SA.

I'm going to stick with suggesting that rusty pilots flying their new RV's just leave the knobs alone, fly the airplane, and stay eyes out until well clear of the airport area. LOP is good; learn it in cruise first, and progress to more advanced management later, after sorting out the airplane.

Stick with what you like, but I am going to challenge you that RUSTY pilots should not be test flying their new RV's. I am on the board of the SAAA (Australian EAA) and was a founding participant in http://www.rvflightsafety.org ( I even named it :) ) and one of the biggest things we push is recency and experience for test flying any new plane. We are having a big push here at the moment with CASA over transition training in a formalised sense, and I know this is one of the issues in the USA as well, and Van himself is very strong on these matters.

If the pilot is incapable of doing a BMP on his second or third flight which will be longer duration typically, then fine, leave it full rich as that is where it belongs, unless you are comfortable with a simple BMP to a high power LOP breaking. It is a non event. Clearly you have not done any. I have done many.

and progress to more advanced management later, after sorting out the airplane.
I have to agree 100% :) On your first flight there are priorities, but for the majority who have done a good job, the first flight should uncover nothing of any significant nature, and the second or third flight there is far more capacity for a two second BMP while you move onto other things. If the first flight yields major issues, fuel or oil leaks etc, then back on the deck, fix it and then you basically have another first flight again. I firmly believe if the first flight did not prove the plane was capable of a 4 hour flight next, then the next flight after rectification is a first flight repeated.

The stats say early test flights are the deadly ones. Let's not make it more complicated.

Agree again. I have sat down and poured through 10 years of NTSB accident reports and 10 years of ATSB reports, looking at those stats. Plus the special focus on ABE that the FAA and ATSB have done. Even provided some corrections to ATSB. So I agree 100%.

So tell me on the second or third flight what achieves the most eyes down and complication?
A: flying around and constantly worry about the high CHT's. (Eyes down a lot, and that is what happens) Refer all the threads on VAF as statistical data.
B: flying to 1500-2000' levelling off, accelerating and cooling the engine and doing a BMP that requires absolutely no eyes down, (most folk need to close their eyes the first couple of times-perhaps in transition training) and then parking the engine safely and not worrying about CHT's as much. Then sitting in the lounge at home later looking at data.

You might prefer A, but I prefer B.

You do not have to agree with me, the readers can make up their own mind, but when you rock up to Ada in March, print this out and go ask Deakin or Atkinson during a lunch break what they think is the better way to go for engine breakin and safety of eyes outside. I would love to hear their comments.

Anyway, enjoy your RV8, and thanks for all the good posts on airflow under cowls and all that good stuff!
thumbs.gif
 
Same experience

I witness the same shudder for approximate one second a couple of weeks ago.
Aircraft type RV-10 with 550 hours on the engine. After flying the aircraft for 45 minutes to our destination the aircraft sat on the ground for approximate one hour. The shudder occurred on climb out passing through 3000 feet AGL, approximate 6 minutes after take off.
We have a light speed electronic ignition running the top plugs W27EMR-C, magneto operating the bottom plugs Champion REM 38 E.
At the time fuel boost pump was off, mixture full rich. OAT was approximate 27c quite warm.
I tried to download the engine data, from the Advance AF-2500 EMS, had an issue with my laptop not having a serial port. I have ordered a USB to Serial converter hopping this will allow me to download the EMS data.

David once I download the data would you mind taking a look please?

Mike
Western Australia
 
In the context of desired ring pressure, tell me why.

I'll add some more to this question - I have heard about pressure being needed during break-in to "seat the rings" better. Exactly what forces does the cylinder pressure apply to the rings? I can see the pressure forcing the rings towards the crankshaft within the piston grooves, but I do not see anything forcing the rings radially outward. If anything, the pressure in the cylinder will "find" the outer diameters of the rings through the oil film and apply radial force inward on the rings. There will, of course, be some pressure which finds its way over the top and behind the rings, but that is a more tortuous path than through the oil film on the OD of the rings. ??
 
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