RPM at Run up.

[mikesalman]

Hi folks, I purchased a 1968 Mooney M20F and the POH says run up at 1700 RPM's. Now that was fine until I purchased a check list from Sporty's Pilot shop for a Mooney M20F in order to preserve the original POH that came with N21NA. That one says 1900 RPM and today, I saw one on E-Bay that also said 1900 RPM. Since I have always been known to be overly cautious you can just imagine what I go through at the beginning of every flight. 1700,1900,1700,1900 who do I believe? The POH was written 45 years ago and the engine is a 580 hour 6 year old, Should I go with 1900 or 1700. Please help I am new to all this and I am also a new pilot with 135 hours TT and 16 Hours in my Mooney. Any advice would be greatly appreciated.

Thanks in advance

Mike Salman

[MARZ]

I use 1700 - do the mags and then go to 2000 to cycle the prop.

[mikesalman]

I use 1700 - do the mags and then go to 2000 to cycle the prop.

Thanks, any special reason to go to 2000 to cycle the prop instead of 1700 ?

[Oscar Avalle]

I just use 1900 cycle mags and prop. 

[BigTex]

For me 1700 RPM was not high enough to cause my prop to cycle. So I do my mag check at 1700 and prop at 1900.

[MARZ]

Thanks, any special reason to go to 2000 to cycle the prop instead of 1700 ?

 

For me 1700 RPM was not high enough to cause my prop to cycle. So I do my mag check at 1700 and prop at 1900.

 

 

 

 

What Gary said.....!! 'cept I round it up 100

[Bob_Belville]

Obviously: 1800. 

[PilotDerek]

I use 1900 for both mag and prop

[yvesg]

My POH (65C model) says 1800

Yves

[NotarPilot]

I remember reading an article by John Deakin (Pelican Perch #63) saying it doesn't really matter to have the RPM be exactly what the POH says for purposes of doing a mag check. Just get the RPM stable at an RPM between 1700-1900 RPM and cycle the mags. That makes sense to me, I doubt you'll get much of a different result between RPMs as long as they're stable when you perform the test.

However, if you listen to Mike Busch, during a mag check you should be looking for a rise in EGT as well as your mag drop. He says the RPM drop alone is a bit of an archaic test. During my run-up I now watch to make sure all my EGTs rise when I cycle the mags. Of course you need a proper engine monitor to do this. I bought an Insight G3 last year and I really like it. As far as the run-up and engine philosophy are concerned, I guess it depends on who and what you choose to believe. I guess it's a lot like religion.

[PTK]

I concur with NotarPilot. If you have an engine monitor (if you don't you should consider it) watch EGTs to be sure all rise and none fall.

[N601RX]

I use 1800 and see a 60 rpm drop on each mag.

[jnisley]

1700 for both.

[jlunseth]

 

I remember reading an article by John Deakin (Pelican Perch #63) saying it doesn't really matter to have the RPM be exactly what the POH says for purposes of doing a mag check. Just get the RPM stable at an RPM between 1700-1900 RPM and cycle the mags. That makes sense to me, I doubt you'll get much of a different result between RPMs as long as they're stable when you perform the test.

However, if you listen to Mike Busch, during a mag check you should be looking for a rise in EGT as well as your mag drop. Hesays the RPM drop is a bit of an archaic test. During my run-up I now watch to make sure all my EGTs rise when I cycle the mags. Of course you need a proper engine monitor to do this. I bought an Insight G3 last year and I really like it. As far as the run-up and engine philosophy are concerned, I guess it depends on who and what you choose to believe. I guess it's a lot like religion.

The RPM drop is a bit of an archaic test until the day comes that the engine dies on one mag., or the drop is 200. I do the EGT rise test also, with my JPI, but I like the basic test, it makes sure the mags are working.

[N601RX]

What mag drops are most people seeing?

[Mooneymite]

My POH is prerty clear. Barring any exciting new scientific information, that's what I do.

Has anyone seen the video on "shock-cleaning" a fouled plug? Apparently the technique has been around for a long time, but it was news to me.

-

[Bennett]

My POH (1983 M20J) reads: "1900-2000 RPM" for the mag check. I use 2000 RPM as shown on the JPI 830, check for EGT rise as mags are switched, check for RPM drop, and proper Vacuum (I also

turn on the auxiliary electric vacuum pump at this time to make sure it will work at high RPMs), and then cycle the prop (three times if cold - twice if already warm). Since I switched to

fine wire plugs on the bottom cylinders I have not had any oil fouling from idling.

[fantom]

You guys aren't doing the run up LOP?

[Marauder]

My 75F manual says to use 2000 rpm. So obviously this has changed for some reason or another over the years. Your F And mine both used the same prop engine config when new. So it would be interesting to know why it changed. As for run-up, I use a combination of rpm drop (using the rpm drop feature on the EI tach) and watch for bars dropping on the engine monitor.

[Super Dave]

One of Bob Kromer's articles mentioned the change in run up RPM over the years, but he didn't know the reason either.

[Earl]

 

The RPM drop is a bit of an archaic test until the day comes that the engine dies on one mag., or the drop is 200. I do the EGT rise test also, with my JPI, but I like the basic test, it makes sure the mags are working.

Here's how I was instructed to do my mag test with my EDM-730.  I lean while taxiing and do my run up leaned.  When I switch mags I look for a ~50 degF increase in EGT temps on all cylinders.  No 50 degF rise tells me I have a bad mag.  And of course if it is dead altogether wouldn't the engine die when you are on the bad mag?  I hope I don't have this wrong but I was told this was a more reliable test for a bad mag and also can identify bag plugs or blocked injectors and on which cylinder.  Was given this instruction from the MSC that put in the 730.  What am I missing?

 

This is what Mike Busch recommends and is probably where the poster got the term archaic.

 

"To begin with, most POHs instruct you to note the RPM drop when you switch from both mags to just one, and give some maximum acceptable drop. This archaic method makes little sense for aircraft that are equipped with a digital engine monitor (as most are these days), because EGT rise is a far better indicator of proper ignition performance than RPM drop. You should focus primarily on the engine monitor, not the tachometer, when performing the mag check. What you should be looking for is all EGT bars rising and none falling when you switch from both mags to one mag. The EGT rise will typically be 50 to 100 degrees F, but the exact amount of rise is not critical, and it's perfectly normal for the rise to be a bit different for odd- and even-numbered cylinders. You should also be looking for smooth engine operation and stable EGT values when operating on each magneto individually. A falling or erratic EGT bar or rough engine constitutes a "bad mag check" and warrants troubleshooting the ignition system before flying."

[N201MKTurbo]

I just close my eyes and switch the mags. If the engine starts missing or shaking on one mag, I need to fix something.

[Marauder]

The RPM drop is a bit of an archaic test until the day comes that the engine dies on one mag., or the drop is 200. I do the EGT rise test also, with my JPI, but I like the basic test, it makes sure the mags are working. Here's how I was instructed to do my mag test with my EDM-730. I lean while taxiing and do my run up leaned. When I switch mags I look for a ~50 degF increase in EGT temps on all cylinders. No 50 degF rise tells me I have a bad mag. And of course if it is dead altogether wouldn't the engine die when you are on the bad mag? I hope I don't have this wrong but I was told this was a more reliable test for a bad mag and also can identify bag plugs or blocked injectors and on which cylinder. Was given this instruction from the MSC that put in the 730. What am I missing? This is what Mike Busch recommends and is probably where the poster got the term archaic. "To begin with, most POHs instruct you to note the RPM drop when you switch from both mags to just one, and give some maximum acceptable drop. This archaic method makes little sense for aircraft that are equipped with a digital engine monitor (as most are these days), because EGT rise is a far better indicator of proper ignition performance than RPM drop. You should focus primarily on the engine monitor, not the tachometer, when performing the mag check. What you should be looking for is all EGT bars rising and none falling when you switch from both mags to one mag. The EGT rise will typically be 50 to 100 degrees F, but the exact amount of rise is not critical, and it's perfectly normal for the rise to be a bit different for odd- and even-numbered cylinders. You should also be looking for smooth engine operation and stable EGT values when operating on each magneto individually. A falling or erratic EGT bar or rough engine constitutes a "bad mag check" and warrants troubleshooting the ignition system before flying."

I was an early adopter of engine analyzers and what Mike B says is correct. A fouled plug is pretty obvious, you would immediately see the EGT drop and by knowing which cylinder and mag you are checking you can pull that plug if you can't burn it clean by leaning. An engine analyzer also can point out a lot of others like pre-ignition and detonation in flight. I also use mine to check whether the mixture is working correctly as well. Pulling it back during the run up with both mags on, I am looking for a uniform EGT increase as well. In your example above, the amount of rise is not as important as whether they all rise and rise in a similar fashion for both mags.

[AmigOne]

On my 68 C, 1700 RPM for both mag (90 rpm drop) and propeller cycle. Slight rise and stable EGTs values.

[Lood]

1700 rpm for both and since it doesn't that cold over here, I never cycle the prop more than once. Most pilots cycle 3 times, however, but what really makes me shudder are the guys that let the rpm drop until the engine almost die before pushing in the rpm control. I have new mags on my new engine, so the drop is just over 50 rpm and at this stage, there's no difference in drop between the mags.