Factory CHT required?

[cferr59]

1 hour ago, philiplane said:

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. 91.1305, 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.

 

91.1305 doesn't exist as far as I can tell.  You are thinking of part 23.1305.  I don't think this applies to the M20 since its certification basis is CAR3.  However, the very similar section of CAR3 that I previously quoted would apply.

[N201MKTurbo]

You guys are looking in the wrong place. You are not trying to certify a new airplane, our airplanes have already been certified. The required instruments are listed in the TCDS. If you want to change what is in the TCDS, you need an STC, or a field approval (one time STC). 

[cferr59]

12 minutes ago, N201MKTurbo said:

You guys are looking in the wrong place. You are not trying to certify a new airplane, our airplanes have already been certified. The required instruments are listed in the TCDS. If you want to change what is in the TCDS, you need an STC, or a field approval (one time STC). 

I am not seeing it in the TCDS, but maybe there is a reference to some other material.  Nor am I seeing other seemingly required engine instrumentation listed. 

For reference, this is the TCDS:

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/6ea0f05ecca8304486258305006833cf/$FILE/2A3_Rev_58.pdf

[EricJ]

Just now, cferr59 said:

I am not seeing it in the TCDS.  Nor am I seeing other seemingly required engine instrumentation listed. 

For reference, this is the TCDS I am looking at:

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/6ea0f05ecca8304486258305006833cf/$FILE/2A3_Rev_58.pdf

That's the correct TCDS and if you look in the "Required equipment" section for each airplane it starts out with whatever CAR 3 requires, plus the things listed.   So CAR 3 has the basic requirements.   Since we fly under Part 91, it drives also.

 

[N201MKTurbo]

16 minutes ago, cferr59 said:

I am not seeing it in the TCDS, but maybe there is a reference to some other material.  Nor am I seeing other seemingly required engine instrumentation listed. 

For reference, this is the TCDS:

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/6ea0f05ecca8304486258305006833cf/$FILE/2A3_Rev_58.pdf

What Eric said...

[cferr59]

10 minutes ago, EricJ said:

That's the correct TCDS and if you look in the "Required equipment" section for each airplane it starts out with whatever CAR 3 requires, plus the things listed.   So CAR 3 has the basic requirements.   Since we fly under Part 91, it drives also.

 

Ok, so I think I get it now. 

To summarize (and feel free to correct me if this is incorrect):

The CHT guage is not listed as required equipment directly in part 91.  However, assuming you have cowl flaps,  you cannot operate under part 91 without the CHT guage because:

91.213.d.2.ii says "no person may take off an aircraft with inoperative instruments or equipment installed unless the following conditions are met:  ...

[The inoperative instruments and equipment are not] Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;    ..."

The TCDS under required equipment says "In addition to the pertinent required basic equipment specified in CAR 3..."

CAR 3.675 says:  "A cylinder head temperature indicator shall be provided for each engine on airplanes equipped with cowl flaps..."

[N201MKTurbo]

Just now, cferr59 said:

Ok, so I think I get it now. 

To summarize (and feel free to correct me if this is incorrect):

The CHT guage is not listed as required equipment directly in part 91.  However, assuming you have cowl flaps,  you cannot operate under part 91 without the CHT guage because:

91.213.d.2.ii says "no person may take off an aircraft with inoperative instruments or equipment installed unless the following conditions are met:  ...

[The inoperative instruments and equipment are not] Indicated as required on the aircraft's equipment list, or on the Kinds of Operations Equipment List for the kind of flight operation being conducted;    ..."

The TCDS under required equipment says "In addition to the pertinent required basic equipment specified in CAR 3..."

CAR 3.675 says:  "A cylinder head temperature indicator shall be provided for each engine on airplanes equipped with cowl flaps..."

I would have your IA call your FSDO and ask if your scanner meets the requirement. Send him references to all the above.  It looks like it does. But you don't have to convince me. I would then put it all on a 337 and have the FSDO inspector approve it. Field approval. Then you will be golden.

[jetdriven]

problem with the JPI EDM-830 is it is not certified as a primary instrument. Maybe you have a high quality AEM racecar CHT gauge, but to the feds, its the same thing.

[carusoam]

Take the PP short cut...
 

If you want to know if a gauge is required for flight...

Look in the limitations section for the plane...

If it is listed there.. with limitations... it is needed to inform the pilot when a certain event has been exceeded...Red lines and green arcs are typical...

For the M20C and CHT...

I present the M20C’s POH limitations section where it discusses the CHT gauge...

see page below...

Section 4: Limitations...
 

Later in the POH they discuss the variables of what is required when... Day/night VFR/IFR... since the engine is always running in all of these conditions.... expect that this particular gauge is a requirement... manufacturer name and model number have a meaning...

Even if an AEM gauge is higher quality....

There used to be limitations that wouldn’t allow adding extra gauges to the plane... the way things considered portable are allowed...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

[carusoam]

Interesting detail....

In our primary flying lessons....

Typically we learn Tomatoflames.... as a pneumonic for knowing what we need...

And Flaps for what we need at night...

Sure the second t stands for temperature...

But... according to these guys... it is only needed for each water cooled engine...

No mention of cowl flaps except for the night flying requirement pneumonic. 

https://www.m0a.com/required-vfr-day-night-instruments/

Sure, not everyone has the latest version of your plane’s POH... Because they weren’t required when your plane was built... time moved on.... data got filled in... it would be good to get one of these things.... for reference... 

Best regards,

-a-

[Hank]

12 hours ago, carusoam said:

Typically we learn Tomatoflames.... as a pneumonic for knowing what we need...

And Flaps for what we need at night...

Sure the second t stands for temperature...

I remember TOMATO FLAMES, just not what the letters stand for. But does your "T for Temperature" mean Oil Temp, or Cylinder Head Temp???

[Hank]

12 hours ago, carusoam said:

Take the PP short cut...
 

If you want to know if a gauge is required for flight...

Look in the limitations section for the plane...

If it is listed there.. with limitations... it is needed to inform the pilot when a certain event has been exceeded...Red lines and green arcs are typical...

For the M20C and CHT...

I present the M20C’s POH limitations section where it discusses the CHT gauge...

see page below...

Section 4: Limitations...
 

That describes marking on the instruments, but doesn't mention which ones are required. flip over to Page 4-7 for the list of Required Equipment for VFR flight, which are incorporated into all other Required Instrument lists, and there is Cylinder head temperature gage. It doesn't need to be the original factory gage, but it does need to be a gage certified for primary use in your model of aircraft.

Edited August 12, 2020 by Hank

[carusoam]

The tomatoflames and flaps lists....

Interesting how memory fills some things in, in a sub-ideal way...

OilT is an O... (oil cooled engine)

T is a different Temperature.... (water cooled engine)

Its an either or...   

-a-