Do I have a rpm restriction or not?

[Glen Davis]

I have a placard to avoid continuous operation between 1500 and 1950 rpm w mp below 15”. I know this is due to harmonic vibrations that can cause damage, however book says with McCauley prop only. I have a Hartzel.  Is there any restriction with the Hartzel? Thanks. 

[jaylw314]

If you have the 2-blade Hartzell, nope.  Not sure of the 3-bladed prop

Edited August 1, 2021 by jaylw314

[PT20J]

The authoritative source to find this sort of information is the TCDS.

The restriction only applies to the McCauley.

If you have the placard, perhaps someone changed the prop and didn't remove it. The yellow arc should be removed from the tachometer, also.

Skip

[carusoam]

+1 on finding when the prop got swapped… there may be an STC that defines all of the changes that go with it…

This is where the placards and tach artwork gets adjusted…

The prop log would be a good place to start…

Don’t fear the small changes… they aren’t nearly as expensive as swapping a prop….  

Best regards,

-a-

[EricJ]

The rpm restrictions are in the Limitations section of the POH.  While the placard only applies to the McCauley, the tach is required to be marked with the yellow caution range from 1600-1950.    I have the Hartzell Top Prop, installed via STC, which also supposedly has no yellow arc limitations, but it still feels weird at those rpms so I try to minimize time spent there.

 

 

 

[PT20J]

39 minutes ago, EricJ said:

The rpm restrictions are in the Limitations section of the POH.  While the placard only applies to the McCauley, the tach is required to be marked with the yellow caution range from 1600-1950.    I have the Hartzell Top Prop, installed via STC, which also supposedly has no yellow arc limitations, but it still feels weird at those rpms so I try to minimize time spent there.

 

 

 

There is an interesting discrepancy between the POH/AFM and the TCDS. The former lists one limitation (1500 - 1950 RPM) for the tachometer. However, the TCDS lists three propellers — two McCauleys and one Hartzell. The Hartzell does not require tachometer marking, and each McCauley has a different yellow band range. I’m not sure which FAA-approved document takes precedence. 

Didn’t the Top Prop STC come with an AFMS including revised limitations?

Skip

[carusoam]

My TopProp and 310HP STC revised the RPM operations from 2500rpm max to 2700rpm max…

Initially, they were two separate STCs that caused confusion during the buying process….

That got simplified with a single STC by the time I was finishing the purchase…

 

Since the engine / prop combination is what is getting tested for the STC…

old ranges for a different engine/prop combination are not expected to be correct…

Make sure the right prop, is on the right engine, and has the proper tach markings for that combination…. 
 

Harmonic vibrations are the bad guys… they are hidden amongst all the vibes you can feel…. Apparently we don’t feel the harmonics…  most likely because they are shadowed by the regular vibrations… our butt sensors aren’t fine enough to tell the difference…

 

If we dampened only the baseline vibrations and left the harmonics…. I bet you would easily feel them!

PP thoughts only not a mechanical engineer…

Best regards,

-a-

[Guest]

Depending on which model of propeller is installed on which model of Mooney and which model of engine determines the RPM/power restrictions.

From the Hartzell Top Prop sales page and the Type certificate page for the propeller.

Clarence

[EricJ]

2 hours ago, M20Doc said:

Depending on which model of propeller is installed on which model of Mooney and which model of engine determines the RPM/power restrictions.

From the Hartzell Top Prop sales page and the Type certificate page for the propeller.

Clarence

The manual for my Hartzell top prop only has one other limitation that might be potentially relevant, that an HC-C2YR-1BF/F7666A-2 installed on a Lyc O-360-A1A with Lightspeed Plasma II electronic ignition has an rpm limitation against continuous operation between 2000 and 2250 rpm and restricted to above 2600 rpm only for takeoff.

So, probably doesn't affect any, or at least very many, Mooneys, and certainly no J models.

 

[A64Pilot]

What are the operating conditions that will get you in the avoid range? On taxi I hit 15” prior to the bottom of the yellow, but I’m at sea level, maybe high altitude airports?

interesting if I lean excessively for taxiing which I usually do, then I can get into the avoid range, other than that I assume you would have to be descending at a low airspeed to get into the avoid range?  On short final I may be in the range, but not continuously.

[A64Pilot]

On 8/1/2021 at 2:17 PM, carusoam said:

 

If we dampened only the baseline vibrations and left the harmonics…. I bet you would easily feel them!

PP thoughts only not a mechanical engineer…

Best regards,

-a-

Maybe, but maybe not. I’ve done quite a bit of prop work as in prop selections on aircraft and vibe surveys etc, and one very dangerous harmonic in particular when it occurs I’ve been told the prop if anything feels smoother than normal, it’s called the “reactionless mode” and has caused several prop failures and deaths.

Google “reactionless mode” if your interested. I believe the name reactionless comes from an excessive prop vibe that is not transmitted, it’s “reactionless” But I may be wrong.

It may be a turbine only thing, but prop harmonics can be extremely damaging and cause prop failure on recips too.

Hartzell has gotten so good at vibe surveys that often they can sign one off by analysis.

Some of the Engineers I’ve talked to at Hartzell hated ignition systems that could change timing, there are engine advantages to variable timing of course, but apparently it really complicates a vibe survey by possibly causing harmonics where none existed with a fixed timing ignition.

Edited August 3, 2021 by A64Pilot

[Mooney Dog]

52 minutes ago, A64Pilot said:

What are the operating conditions that will get you in the avoid range? On taxi I hit 15” prior to the bottom of the yellow, but I’m at sea level, maybe high altitude airports?

interesting if I lean excessively for taxiing which I usually do, then I can get into the avoid range, other than that I assume you would have to be descending at a low airspeed to get into the avoid range?  On short final I may be in the range, but not continuously.

under basic point to point use, probably no real situation.

If you're going out to practice slow flight or stalls and falls, you might run into those areas from time to time, but YMMV. 

 

Its not that you'll never get to those points per say, its that if you do find yourself in those ranges, adjust what you're doing or dont stay in that situation for long. 

[bradp]

If you pull the prop back on descent this could be a factor.  

[PT20J]

After thinking about this, if I had a Hartzell prop specified in the TCDS I would remove the placard. I wouldn’t bother to remove the yellow range from the tach unless I replaced it or had it overhauled. At that point, my authority for removing the yellow arc would be the TCDS and if questioned about the limitations in the AFM I would argue that the associated placard listed in the same limitations chapter clearly states “McCauley Propeller Only.”

Skip

[EricJ]

2 hours ago, PT20J said:

After thinking about this, if I had a Hartzell prop specified in the TCDS I would remove the placard. I wouldn’t bother to remove the yellow range from the tach unless I replaced it or had it overhauled. At that point, my authority for removing the yellow arc would be the TCDS and if questioned about the limitations in the AFM I would argue that the associated placard listed in the same limitations chapter clearly states “McCauley Propeller Only.”

Skip

That seems reasonable to me, but when JPI sets up an EDM I think they mark the range per the POH regardless of the propeller installed.   I don't know how other digital instrument systems manage it, but I'd be curious how they'd get around the POH limitation.

 

[ArtVandelay]

That seems reasonable to me, but when JPI sets up an EDM I think they mark the range per the POH regardless of the propeller installed.   I don't know how other digital instrument systems manage it, but I'd be curious how they'd get around the POH limitation.
 

If you send them copies of any STCs that change the POH limits they will adjust accordingly.

[A64Pilot]

12 hours ago, bradp said:

If you pull the prop back on descent this could be a factor.  

below the green?

[PT20J]

10 hours ago, EricJ said:

That seems reasonable to me, but when JPI sets up an EDM I think they mark the range per the POH regardless of the propeller installed.   I don't know how other digital instrument systems manage it, but I'd be curious how they'd get around the POH limitation.

 

Garmin leaves it up to the installer. It’s interesting when two FAA-approved documents disagree. Might be able to work something out with JPI if you supplied all available documentation and pointed out the discrepancy. 

Skip

[A64Pilot]

The few primary systems I’ve worked with are required to be pre-programmed by the manufacturer, if for an experimental airplane, then your allowed to program the limits.

Systems that are not primary I believe you can program any way you want.

Yes other enunciations can be added, but your not allowed to change the limits.

EI has you fill out a sheet for at least the MVP-50 and they send it already programmed, if there is a mistake, they can issue you a onetime level one password that will allow you to make the change, unless things have changed, this password can only be used once, surely JPI has a way of changing their instrumentation to cover when you buy an STC’d prop and have different avoid ranges or whatever.

A problem with “legacy” engines etc is that they were built back in the day of analog gauges, so it was entirely normal say to have takeoff RPM for example be 2700 RPM, but 2701 is an exceedence meaning of course your operating beyond the red line. Digital instrumentation will alert every time a limit is exceeded so that the pilot will get a lot of false alerts

[OR75]

11 hours ago, EricJ said:

That seems reasonable to me, but when JPI sets up an EDM I think they mark the range per the POH regardless of the propeller installed.   I don't know how other digital instrument systems manage it, but I'd be curious how they'd get around the POH limitation.

 

The POH should reflect the limitations of the prop installed (per the STC if a prop was installed based on an STC)

it would be wrong if they are using a generic POH downloaded from the internet 

 

[ArtVandelay]

it would be wrong if they are using a generic POH downloaded from the internet

From personal experience I know JPI doesn’t, they rely on your avionics person sending them the correct pages from your POH, of course your avionics person is relying on you to point out whatever STC you have that affects limits.

[jaylw314]

14 hours ago, PT20J said:

After thinking about this, if I had a Hartzell prop specified in the TCDS I would remove the placard. I wouldn’t bother to remove the yellow range from the tach unless I replaced it or had it overhauled. At that point, my authority for removing the yellow arc would be the TCDS and if questioned about the limitations in the AFM I would argue that the associated placard listed in the same limitations chapter clearly states “McCauley Propeller Only.”

Skip

IIRC, when I had the Hartzell prop installed, it comes with an AFMS insert specifically stating the RPM limits no longer apply, so there shouldn't be any controversy.

[PT20J]

2 minutes ago, jaylw314 said:

IIRC, when I had the Hartzell prop installed, it comes with an AFMS insert specifically stating the RPM limits no longer apply, so there shouldn't be any controversy.

That should be the case if you had one installed by STC. The more interesting case is if you replace a McCauley prop with the model Hartzell listed in the TCDS because that would only require a logbook entry and no AFMS.

[OR75]

6 minutes ago, PT20J said:

That should be the case if you had one installed by STC. The more interesting case is if you replace a McCauley prop with the model Hartzell listed in the TCDS because that would only require a logbook entry and no AFMS.

Making sure the right placards are in place and POH updated when work is done is always a requirement. Even if when only a logbook entry is done.
 

say for example a change is made that does not require a 337 but does require a weight and balance recalculated (like simple move an item in the cone avionics rack)  It would only require a logbook entry but also a change in the POH . 
 

 

[jaylw314]

3 hours ago, PT20J said:

That should be the case if you had one installed by STC. The more interesting case is if you replace a McCauley prop with the model Hartzell listed in the TCDS because that would only require a logbook entry and no AFMS.

Oooooh, I forgot there was a Hartzell on the TCDS.