JPI EDM900 question

[Airways]

I now have an EDM900. It’s brilliant ! However, it is so sensitive that during tkof roll MAP and RPM go in the red zone. Not by much; .3 inch and 20 rpm or so.

Are there other people with the same issue ? Do you disregard it or do you fiddle with the parameters during tkof roll ?  I intend to fiddle, but it takes too much of my attention at a critical time.

 

Opinions ?

[Skates97]

My RPM will do about the same. I don't mess with it during the roll, I just give the prop about a 1/2 turn back before taking the runway which usually puts my RPM at 2,690-2,700 on take off. With a regular tach on the far right side of the panel no way I'm noticing that 10-20 RPM but with the 900 flashing red right in front of me I take notice.

[gsxrpilot]

Mine is the same. I watch it, but don't change anything until pattern altitude and cleaned up.

[JimB]

35 minutes ago, gsxrpilot said:

Mine is the same. I watch it, but don't change anything until pattern altitude and cleaned up.

It is annoying but mine is also the same and I handle it the same as well. 20 RPM is .7% so I really don't worry about it. However, I will probably dial my governor back a bit this annual. I don't like things turning red on takeoff. After a while I will quit paying attention to it and that's when something will alert that I really should be aware of. 

[Airways]

OK thank you all.  And what concerns you more: RPM or MAP ?  In my case it's a TSIO360MB that redlines at 36/2700.

[gsxrpilot]

5 minutes ago, Airways said:

OK thank you all.  And what concerns you more: RPM or MAP ?  In my case it's a TSIO360MB that redlines at 36/2700.

RPM would probably concern me more. But it never gets into a range that would be concerning. I'm also flying a TSIO360MB or SB when I get it back.

I have my EDM900 on the left side of the panel and watch it religiously. Red numbers are never a cause for alarm because I was already watching them when they got there. It's just the way I fly my airplane. I'm more like the Flight Engineer. The autopilot is usually doing the flying and I'm working the radios and managing the engine.

[MBDiagMan]

The prop Governor needs adjustment.

[Airways]

2 hours ago, MBDiagMan said:

The prop Governor needs adjustment.

But does it ? The engine and prop are doing exactly the same as before, only the analog gauges never picked up on it.

[47U]

How accurate are your analog gauges?  Lycoming recommends that you calibrate your cockpit gauges once per year.  An idea probably initiated in their legal department. 

More relevant, analog gauges tend to smooth out the momentary spikes.  You just don’t see them.  With a digital instrument, one parameter momentarily out-of-tolerance will be flagged because of the multiple times-per-second refresh rate.

 

[kortopates]

prop governor should be adjusted to avoid any over speed. it is a redline limitation. That said occasional “brief” overspeed by 20 rpm isn’t a big deal but if it’s over redline the entire time that’s easily corrected.

With MAP on the other hand, it’s normal and expected to overboost with cold oil for up to 2 min as it warms up and will similarly under boost with hot oil. Your POH also spells this out. The controller has to set up with oil fully warmed up (170-175F) so that it hits redline at normal operating oil temp.


Sent from my iPhone using Tapatalk

[carusoam]

Let’s clear up the situation...

We are using a precise digital device to measure the crude mechanical world...

JPI is fantastic at measuring what is really happening...

Our limitations were written when the instruments were analog and didn’t record the exact oscillations that the mechanical system is showing...

So...

Take a look at what is really happening during the acceleration to take-off speed...  there will be a little bit of over-shoot with some oscillation as MP builds and Blade angle gets adjusted by the gov...

There is a lot going on... there always has been...

Now...

JPI alarms typically go off with any decimal point above the red line number it has in memory... 2700.1 

If it settles back to 2700.0 ... no reason to change...

For full power, you want full rpm...  our operating instruction don’t exactly take into account the acceleration of rotating parts that have mass... or the natural control over shoot that comes with it...

 

Next steps...

Take a moment to download some data... review what happened...

did it exceed the redline enough to alarm?

did it return to the redline, or below?

Does it continue to exceed after all of the accelerations have finished?

Download the data, post it to Savvy, click the share button, post the link here...   

Overall, the JPI will light up like a Christmas tree right when you would like it to be the most calm...

If they ever come up with version two... they will use some of their computing magic to get better control over what is a real alarm vs. a not so real alarm...

The fuel level sensor guy has spent plenty of time controlling the data his sensors send out....  fuel sloshes... no need to alert the pilot...

See if that helps understand what you are seeing... if it is a real overshoot... get the systems adjusted... if it is micro and temporary... complain to JPI while asking for version two...   

Easy enough when it’s just me in the plane... but the Christmas tree affect can be pretty disturbing to other people...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[ArtVandelay]

Let’s clear up the situation...

We are using a precise digital device to measure the crude mechanical world...

JPI is fantastic at measuring what is really happening...

Our limitations were written when the instruments were analog and didn’t record the exact oscillations that the mechanical system is showing...

So...

Take a look at what is really happening during the acceleration to take-off speed...  there will be a little bit of over-shoot with some oscillation as MP builds and Blade angle gets adjusted by the gov...

There is a lot going on... there always has been...

Now...

JPI alarms typically go off with any decimal point above the red line number it has in memory... 2700.1 

If it settles back to 2700.0 ... no reason to change...

For full power, you want full rpm...  our operating instruction don’t exactly take into account the acceleration of rotating parts that have mass... or the natural control over shoot that comes with it...

 

Next steps...

Take a moment to download some data... review what happened...

did it exceed the redline enough to alarm?

did it return to the redline, or below?

Does it continue to exceed after all of the accelerations have finished?

Download the data, post it to Savvy, click the share button, post the link here...   

 

Overall, the JPI will light up like a Christmas tree right when you would like it to be the most calm...

If they ever come up with version two... they will use some of their computing magic to get better control over what is a real alarm vs. a not so real alarm...

The fuel level sensor guy has spent plenty of time controlling the data his sensors send out....  fuel sloshes... no need to alert the pilot...

See if that helps understand what you are seeing... if it is a real overshoot... get the systems adjusted... if it is micro and temporary... complain to JPI while asking for version two...   

Easy enough when it’s just me in the plane... but the Christmas tree affect can be pretty disturbing to other people...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

FAA dictates what alarm levels should be, you can have lower prealarms in some cases (like CHTs), but you can’t change them, remember it’s certified by FAA. So unless FAA changes its mind, no changes to its behavior will be made.

[carusoam]

On 3/3/2021 at 3:02 AM, ArtVandelay said:

FAA dictates what alarm levels should be, you can have lower prealarms in some cases (like CHTs), but you can’t change them, remember it’s certified by FAA. So unless FAA changes its mind, no changes to its behavior will be made.

Tom,

That’s the point of my paragraph...

The FAA has set hard lines...

JPI clearly followed exactly what the FAA said to do...

Back in the day, our needles wobbled and everyone accepted the fact that needles wobble...

Nobody bothered to discuss that our mechanical controls over things like MP and RPM are not exact during changes... they can overshoot, undershoot, and can be decreasing sinusoids...

Today we have an instrument that is sensitive enough to detect and alarm when the needle wobbles 0.1 rpm over the redline... and only stays there for a micro second...

That isn’t protecting us or our equipment for any real reason...

Tuning down our engines so the JPI doesn’t alarm wouldn’t be a proper response either...

See the video where the Mooney plows into a berm because the engine wasn’t producing full power...

Sure... set the alarms in accordance with the actual redline... set the engine to control at the redline...

It is the other variable... being discussed...   the small momentary overspeed or over pressures that come with gross power changes... they exist, we just didn’t look so close...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Airways]

3 hours ago, carusoam said:

the Christmas tree affect can be pretty disturbing to other people...

Pretty much the essence of the situation 

[Airways]

It is clear to me that this is a common event for most people with an EDM900.  @carusoam your explanation pretty much coincides with what I was thinking.  It is a good idea to already have a look at the engine data.  I just changed the recording interval to 1 sec, so I’ll make some additional flights first.

[Airways]

4 hours ago, kortopates said:

With MAP on the other hand, it’s normal and expected to overboost with cold oil for up to 2 min as it warms up and will similarly under boost with hot oil. Your POH also spells this out.

Correct.  And the POH even talks about whole inches, not even tenths.

[ArtVandelay]

Tom,

That’s the point of my paragraph...

The FAA has set hard lines...

JPI clearly followed exactly what the FAA said to do...

But you implied that the next version (2) will fix it and my point is that’s not in JPIs control. I don’t think they can average or otherwise smooth readings to not report high readings.

[Ragsf15e]

16 hours ago, ArtVandelay said:

But you implied that the next version (2) will fix it and my point is that’s not in JPIs control. I don’t think they can average or otherwise smooth readings to not report high readings.

Well smooth is one thing, adjusting them down or not alarming definitely something different.  I agree jpi can’t set different limits, but there are several indications on the JPIs that benefit from “smoothing.”  Some are software, some are “snubbers”.  If this jpi install is new, he’s probably got latest software.  The only snubbers I’ve heard of are for fuel pressure and manifold pressure.  Is there anything to smooth rpm?  I haven’t heard of anything.

[carusoam]

Let’s ask the FAA to re write their rules to cover all the things that happen in reality...with exactness...

If you have watched the FAA, they write rules with broad strokes... intentionally.  As does the FDA... and other governing bodies...

The only difference we are talking about... the mechanical gauges don’t have an alarm or recording mechanism...

The needle blips past the redline while you are not looking at it... it settles out in seconds...

I trust nobody is adjusting the engine performance to match blips on the instruments...

I also trust my mechanic is trained in the art of instruments and how they work...

It would be cool if we had a JPI guy around here... we can ask @Jeev his thoughts on JPI alarms during T/O accelerations...

Best regards,

-a-

[MBDiagMan]

On 3/2/2021 at 11:09 PM, Airways said:

But does it ? The engine and prop are doing exactly the same as before, only the analog gauges never picked up on it.

.... because the analog gauges lacked the accuracy and resolution to detect it.

[Airways]

17 hours ago, MBDiagMan said:

.... because the analog gauges lacked the accuracy and resolution to detect it.

Yes, exactly.  So engine -and propwise nothing has changed.

[Jeev]

On 3/3/2021 at 9:15 PM, carusoam said:

 

It would be cool if we had a JPI guy around here... we can ask @Jeev his thoughts on JPI alarms during T/O accelerations...

Best regards,

-a-

You all have covered just about everything.  JPI is required to set the alarm limits a the exact # that is listed in the POH and has no flexibility to change this.  This is a common occurrence and even more so in the big Conti's in regards to fuel flow.  Many people have their max fuel flow set to 10% of rated HP to keep things cool, this sets off a red alarm at full rich full power.  I have tried to get this resolved for a few customers but its a no go.  A small annoyance for the convince and pin point accuracy of these engine monitors.

[StevenL757]

On 3/4/2021 at 7:26 AM, MBDiagMan said:

.... because the analog gauges lacked the accuracy and resolution to detect it.

@Airways,

My 900 did the same as yours, only not quite as much of a deviation as you described.  My EDM930 does it also.  Normal - not problematic.

Steve

[jlunseth]

On 3/2/2021 at 11:09 PM, Airways said:

But does it ? The engine and prop are doing exactly the same as before, only the analog gauges never picked up on it.

Yup.

Same here. I have the 930. I will get small RPM overruns. The old analog gauges never saw them.  My MP will vary also, but the 231 is different, the pilot is in charge of the throttle always. I set it more or less at 36” on takeoff, but that is not firewall, firewall would be well over  40”. The ram air affect will raise it a little when the aircraft moves down the runway. I will screw the RPMs down a little when there is time. Its not the governor, same governor as before. I had my A&P chase it for awhile, but the changes were so tiny it was really not possible to get rid of the extra 20 RPMs that show up on occasion.

[0TreeLemur]

While this thread considers JPI EDM limits, I have a related question.   Recently we upgraded to the Hartzell Top Prop on our C.  It has no rpm limitations when installed on an O-360.  Anybody ever send their JPI back in to get limits changed?   I still get the red numbers in the old "no-continuous ops" rpm range.   I'd rather not see them since they no longer apply.   Not a big deal, but if I had time to ship it back to JPI I might.