Factory CHT required?

[carusoam]

Igor,

the words used, doesn’t imply one flight is legal... it may sound that way, though...

 

It is a statistical risk analysis situation... if I understand GSXer as well as I think I do...

• Getting caught...
• Getting caught locally...
• Getting caught while on holiday with family...
• Could anything go wrong that would endanger people on the ground or in flight...

So it may be against the FAR to fly without a CHT indicator... (ship’s gauge)

But flying locally would help diagnose the problem... 

So it may be against the FAR technically, to fly around the pattern running tests...

It isn’t any more dangerous for the pilot. It could be hazardous to the cylinder if something were to go wrong with its cooling on that flight...

In other words... flying with something missing from the MEL is bad. Nobody would want to make a habit of it. 

A typical Mooney CHT system can be fully tested on the ground. If it isn’t working on the ground, it probably won’t get any better in flight...

PP thoughts only, not a mechanic...

Seeing if @chrixxer got the CHT ship’s gauge challenge nailed down?

Best regards,

-a-

 

[chrixxer]

"If it isn’t working on the ground, it probably won’t get any better in flight"

Ah, but that's the rub. It works(ish; it reads lower than the EDM-830, but it does provide a reading) on the ground and in flight. And the EDM-830 never hiccups on the ground, no matter how you test it - but a few minutes into any flight, it starts complaining about bad probes and flashing red Xs at you.

I've reached out to the FSDO, and I'm told there are "options," but I don't know yet what those are.

Worst case I'll just replace the factory CHT probe, un-INOP the factory gauge, and see if that cures the issue with the JPI.

[carusoam]

Got a video of the JPI when it starts to act up?

The probes operate on such tiny voltages... they are ultra sensitive to any voltage difference between probes, engine block, fire wall and instrument panel...

If you haven’t reviewed all the grounding straps and their mounting cleanliness... now would be a good time...

Some instrument panels have lost their ground wires over time...

In flight, you might try things like turning the alternator off (field wire switch) or anything else to see if something else is causing the JPI’s problem...

In flight we get heat, vibration, bending of the airframe, and lots of energy and voltage being generated... all the grounds need to be working and not being stressed or strained...

Could be an easy find... a loose ground wire connecting the panel might have a simple solution...

PP thoughts only, not an instrument guy at all...

Best regards,

-a-

[Pete M]

On 4/21/2019 at 11:57 PM, carusoam said:

One small victory after another...

See if you can obtain the latest POH that was ever printed for the the M20F... that would go great to fill in the data that isn’t available for the document that matches your year of build....

PP thoughts only, I got this recommendation from the factory, when I owned an M20C.... a guy from the engineering department named Bill Wheat told me this... then I found Bill’s signature on the AW page of my first Mooney Log Book... 35years after he wielded the pen....

Best regards,

-a-

Bill Wheat was great to talk to. The guy knew everything. I'm assuming he's passed now?

[carusoam]

2 hours ago, Pete M said:

Bill Wheat was great to talk to. The guy knew everything. I'm assuming he's passed now?

Unfortunately, Bill has passed... he flew west, not that long ago, in Mooney years...

He was not only knowledgeable, and skilled, and well respected... he didn’t mind answering the phone and giving Mooney owners great technical advice...

Bill gets mentioned often, as he has given great advice to so many MSers...

https://mooneyspace.com/search/?q=Bill Wheat&updated_after=any&sortby=relevancy&search_and_or=and

Best regards,

-a-

[chrixxer]

11 hours ago, carusoam said:

Got a video of the JPI when it starts to act up?

The probes operate on such tiny voltages... they are ultra sensitive to any voltage difference between probes, engine block, fire wall and instrument panel...

If you haven’t reviewed all the grounding straps and their mounting cleanliness... now would be a good time...

Some instrument panels have lost their ground wires over time...

In flight, you might try things like turning the alternator off (field wire switch) or anything else to see if something else is causing the JPI’s problem...

In flight we get heat, vibration, bending of the airframe, and lots of energy and voltage being generated... all the grounds need to be working and not being stressed or strained...

Could be an easy find... a loose ground wire connecting the panel might have a simple solution...

PP thoughts only, not an instrument guy at all...

Best regards,

-a-

It's been re-grounded. I've been working with JPI on troubleshooting.

The factory CHT was the culprit. We swapped in a new one and I did 0.7 and it works perfectly now (before it would start to freak out almost immediately after rotation). The factory CHT gauge also reads a lot closer to what the JPI is showing, too, bonus.

Now to fix the seat recline!

[carusoam]

Great video chrix.

 

That is unique.

Thanks for sharing it.

Best regards,

-a-

[Cruiser]

23 hours ago, chrixxer said:

It's been re-grounded. I've been working with JPI on troubleshooting.

The factory CHT was the culprit. We swapped in a new one and I did 0.7 and it works perfectly now (before it would start to freak out almost immediately after rotation). The factory CHT gauge also reads a lot closer to what the JPI is showing, too, bonus.

Now to fix the seat recline!

this makes no sense at all unless someone tied (spliced) the two probes together. The OEM CHT should be totally separate from everything else.

Are you using a separate probe for the JPI and a separate probe for the OEM CHT ? 

How are they attached to the Cylinder ?

[chrixxer]

9 minutes ago, Cruiser said:

this makes no sense at all unless someone tied (spliced) the two probes together. The OEM CHT should be totally separate from everything else.

Are you using a separate probe for the JPI and a separate probe for the OEM CHT ? 

How are they attached to the Cylinder ?

The JPI probe is piggybacked on the factory probe. Here's what JPI (Tim Sullivan) said: "Disconnect factory CHT probe and go on a flight. If that probe is bad or not grounded well, will induce voltage into EDM. 2-3” separation from ignition harness. Ignition harness shielding and p-leads terminated correctly." 

(This was after properly grounding the EDM-830 to the engine block didn't cure the issue.) (Well separates from the ignition harness and the harness and p-leads are brand new and properly installed.)

I've flown ~2 hours with it behaving perfectly, now; before it would start to spaz before I hit 400' AGL on climbout.

 

[MooneyBe]

Bringing this thread back to life.. 

Does the requirement to have a 'steam gauge' CHT instrument apply across Mooney models (I'm asking about a Bravo) if you have the JPI 830? I.e. if I have a fully functional 830 but the CHT gauge is inop, am I not legal? 

[carusoam]

Be,

Briefly...

1) Determine if you need the CHT to fly... Is it required for Day VFR?  
2) Can it be substituted by fancy flashy important looking jewelry, or does the ship’s gauge still need to be functional?

 

The list of required instruments is in the POH...

You are going to find all airplanes probably have a CHT as a requirement...

The limitations section is where the list probably is...

It is broken down into VFR/IFR day/night...

and probably corresponds with your training of things like tomato flames...  

No requirement to be an analog or a digital gauge... but it must meet the requirements for being a primary gauge...

JPI830s are lower in cost, and are not primary... JPI900s are more expensive and meet the requirements for being primary...

The ship’s CHT gauge is probably required for all flights in most single engine planes.... it is so easy to fix... in most cases... get on it!

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[kortopates]

Bringing this thread back to life.. 
Does the requirement to have a 'steam gauge' CHT instrument apply across Mooney models (I'm asking about a Bravo) if you have the JPI 830? I.e. if I have a fully functional 830 but the CHT gauge is inop, am I not legal? 

Look at your 830 documentation - it says it’s not legal to replace anything being a non-TSO’d unit.
Upgrade to one of the 9xx TSO’d units and then you can pull or remove your OEM CHT.


Sent from my iPhone using Tapatalk

[ArtVandelay]

Look at your 830 documentation - it says it’s not legal to replace anything being a non-TSO’d unit.
Upgrade to one of the 9xx TSO’d units and then you can pull or remove your OEM CHT.

And all the other engine and fuel gauges as well.

[carusoam]

Very important to know which variables are required...  MP, RPM, CHT, Fuel level... etc...

And that the engine monitor being used is primary for all things in the display...

Some fancy engine monitors are only primary for a few functions, but not all of the functions it can display...

Best regards,

-a-

[Shadrach]

2 hours ago, MooneyBe said:

Bringing this thread back to life.. 

Does the requirement to have a 'steam gauge' CHT instrument apply across Mooney models (I'm asking about a Bravo) if you have the JPI 830? I.e. if I have a fully functional 830 but the CHT gauge is inop, am I not legal? 

The answer is very straight forward. Not legal. The 830 is not approved as a primary instrument. I have a similar set up. My factory CHT has always been questionable. It has never matched the EDM which we know is accurate. Factory gauge is there but I never use it. 
 

Legal ≠ Safe

Safe ≠ Legal

[chriscalandro]

On 4/19/2019 at 12:23 PM, chrixxer said:

Okay, none of this in any way addresses what I asked (and my 1969 M20F has neither a POH nor an MEL)...

Factory CHT required when a TSO’d EDM-830 (including 4-probe CHT) is installed: yes or no? If yes, based on what?

The 830 is not certified as a primary instrument so your primary cht is the factory one and is required. 

[EricJ]

FWIW, whether or not a CHT gauge is required appears to depend on whether or not the airplane has cowl flaps.    If it doesn't have adjustable cowl flaps, it generally doesn't have a CHT (at least, I've not found a counter example, e.g., I've not seen a Piper Arrow with a CHT gauge, they have no cowl flaps).   I seem to recall there were some serial numbers of some M20 model that had fixed cowl flaps, and those may not require a CHT.

As pointed out previously, the POH for the particular airplane should indicate definitively.

[PT20J]

On 8/7/2020 at 11:50 PM, kortopates said:

Look at your 830 documentation 

Kind of amazing what info is to be found in all those manuals ...

[carusoam]

The O gets a CHT...  and has no cowl flaps...   

And has really good CHT control...

And goes really fast...

 

I can see why David was working so diligently on a cowling mod project...

Lots of opportunity in a good cowl design...

Best regards,

-a-

[EricJ]

Just now, carusoam said:

The O gets a CHT...  and has no cowl flaps...   

And has really good CHT control...

And goes really fast...

Ah, interesting.   The CHT is required in all operations, too, so that blows my counter-example example.    It is still true that many, even complex, aircraft without cowl flaps have no CHT.   Now I wonder what the difference is.

[Hank]

2 minutes ago, EricJ said:

Ah, interesting.   The CHT is required in all operations, too, so that blows my counter-example example.    It is still true that many, even complex, aircraft without cowl flaps have no CHT.   Now I wonder what the difference is.

My C, like Anthony's R, has fixed cowl flaps and factory CHT, but isn't quite as fast.

[philiplane]

On 8/8/2020 at 2:45 AM, MooneyBe said:

Bringing this thread back to life.. 

Does the requirement to have a 'steam gauge' CHT instrument apply across Mooney models (I'm asking about a Bravo) if you have the JPI 830? I.e. if I have a fully functional 830 but the CHT gauge is inop, am I not legal? 

For an airplane with cowl flaps, you must have a CHT gauge per FAA 14CFR part 91.

[chrixxer]

10 hours ago, philiplane said:

For an airplane with cowl flaps, you must have a CHT gauge per FAA 14CFR part 91.

Where is that in part 91? (Hint: it’s not.)

there’s a requirement under part 23 (though our planes were certified under CAR 3...)

[cferr59]

56 minutes ago, chrixxer said:

Where is that in part 91? (Hint: it’s not.)

there’s a requirement under part 23 (though our planes were certified under CAR 3...)

Its also required under CAR 3 if you have cowl flaps.  The second point references engine cooling tests.  I'm not sure how to determine which speed they were performed at.  

§ 3.675 Cylinder head temperature indicating system for air-cooled engines. A cylinder head temperature indicator shall be provided for each engine on airplanes equipped with cowl flaps. In the case of airplanes which do not have cowl flaps, an indicator shall be provided if compliance with the provisions of § 3.581 is demonstrated at a speed in excess of the speed of best rate of climb.

[philiplane]

15 hours ago, chrixxer said:

Where is that in part 91? (Hint: it’s not.)

there’s a requirement under part 23 (though our planes were certified under CAR 3...)

The part 91 operating limits are the most important. You can have an airplane with a broken CHT, but you just can't fly it. Just like you sign off an annual on a plane without a current transponder/static system check, but you cant fly it.

Although our planes were certificated under CAR3, since 1968 we've had to operate them under part 91 and maintain them under part 43. 23.1305, power plant instruments, says you have to have a CHT gauge if you have cowl flaps. 91.213 says your required equipment must be operable for flight, unless you have an approved MEL that says otherwise. Too bad we have to rely upon some of the ancient gauges that aren't that accurate, and in many cases we can't get parts to fix them.

 

Edited August 11, 2020 by philiplane