OAT probe

[jetdriven]

Ask him the FAA definition of a "major alteration" and why a clock or OAT qualifies as such.

 

Here's some ammo:

 

 

CFR › Title 14 › Chapter I › Subchapter C › Part 43 › Appendix A

14 CFR Part 43, Appendix A to Part 43 - Major Alterations, Major Repairs, and Preventive Maintenance

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View PDF at GPO Pt. 43, App. A

Appendix A to Part 43—Major Alterations, Major Repairs, and Preventive Maintenance

Link to an amendment published at 77 FR 71096, November 29, 2012.

(a) Major alterations—(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:

(i) Wings.

(ii) Tail surfaces.

(iii) Fuselage.

(iv) Engine mounts.

(v) Control system.

(vi) Landing gear.

(vii) Hull or floats.

(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.

(ix) Hydraulic and electrical actuating system of components.

(x) Rotor blades.

(xi) Changes to the empty weight or empty balance which result in an increase in the maximum certificated weight or center of gravity limits of the aircraft.

(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.

(xiii) Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration characteristics.

 

Minor alteration: an alteration other than a major alteration.

[OR75]

agreed you would think an OAT install be considered minor based of the criteria above.

on the other hand , on the Davtron website, when you look at the installation section for the M300 ( OAT , no clock) it says explicitly that a form 337 is required ( unless the OAT is installed on one of the models for which the M300 is PMA'd.)

confusing

[Awqward]

Ok, the new OAT probe was installed as part of an Electronics International EAC-1 combined EGT/CHT/OAT gauge installation. The mooney OAT/EGT gauge was removed but they left the probe under the right wing... The paperwork with the EAC makes it very clear the instrument is NOT certified as a Primary Replacement....I still have the Mooney CHT gauge but the Mooney EGT has been removed...my research of the regulations and the Type certificate revealed that only the CHT is mandatory (in the TC)...not the EGT or OAT so I believe all is Ok....I think!

[Guest]

And especially an accurate one!  I'd like to know if it is 31 dF or 35 dF before entering that cloud or precip...

 

It isn't difficult to put the probes in the proper location under the wing, so don't settle for one exposed to sunlight, engine heat, etc.

How does one go about calibrating or proving accuracy? Most that I've seen don't agree with ATIS broadcasts.

Inaccurate OAT used to calculate TAS make speed claims unreliable.

Clarence

[N201MKTurbo]

There are many ways to check the accuracy of a temperature sensor. I have found thermocouples to be the most reliable. Get a good quality thermocouple meter and a J or K thermocouple. Place the thermocouple junction on your probe and tape or Ty-wrap it to the probe. Let them equalize for a few minuets then compare the readings. The closer you can do this to zero C the better you will be because that is the only temperature that is important. Your gauge could have scale errors and have a single point calibration at zero C.

Most modern temperature sensors are within 2 C without calibration over their operating range.

[jetdriven]

I chcked mine with two different laser thermometers. The kind you put the dot on the target and pull the trigger. All three said 57 F.  I'd say its accurate to one degree.

[Shadrach]

My plane had the OAT replaced just before I bought it. It was placed on the LHS of the fuselage just fwd of the leading edge....so it sticks out sideways....not sure why they didn't put it under the right wing where the old probe (still is)....I did a search of CAR3, FAR Part 23, part 91 and the M20 TCDS and I cannot find a requirement for an OAT probe, IFR or otherwise......however IMO it is still a Major Alteration requiring a 337 and IA....(and an STC).....so I'm still chasing this down with the previous owner as the paperwork is not quite right yet....a major hassle dealing with a French previous owner and the French shop and French IA who is rarely in the country!

 Mounting an OAT probe on the opposite side of the fuselage is a major alteration???  You may have a promising future with the FAA should you ever decide to move stateside...   Is this considered a major alteration in Scotland (JAA?)?

[Awqward]

No, I guess the Major Alteration was the installation of the EI EAC-1 combined EGT/CHT/OAT instrument....although even for that I can't see that it meets the definition of Major....but my IA thinks so....

[Awqward]

I forgot to add that JAA (now EASA) has nothing to do with it....the plane is on the US register

[KSMooniac]

Some/many IA's will default to calling anything a major alteration just to CYA, and force the decision making (or liability trail) further up the food chain.  It is silly, but today's regulatory environment breeds such behavior.

[Awqward]

I think it's possibly worse over here in Europe because most IAs are also EASA certified and EASA has in general a far more strict (onerous) view of things.... The other issue is the form 8130-3...it is treated as mandatory...whereas as far as I can tell the FARs not only do not mandate a 8130-3, in fact there is no traceability requirement at all....the A&P/IA just needs to ascertain the "airworthiness" of the component/installation....the 8130-3 simply makes such a determination easier....again over here anything going on an EASA plane does need such traceability, which affects the IA's thinking...just my theory!

[N201MKTurbo]

My plane had the OAT replaced just before I bought it. It was placed on the LHS of the fuselage just fwd of the leading edge....so it sticks out sideways....not sure why they didn't put it under the right wing where the old probe (still is)....I did a search of CAR3, FAR Part 23, part 91 and the M20 TCDS and I cannot find a requirement for an OAT probe, IFR or otherwise......however IMO it is still a Major Alteration requiring a 337 and IA....(and an STC).....so I'm still chasing this down with the previous owner as the paperwork is not quite right yet....a major hassle dealing with a French previous owner and the French shop and French IA who is rarely in the country!

 

FWIW

 

the installation instructions for my Davtron said to install the probe just like above. I ignored the Davtron instructions and put it in the same place as the original but on the opposite wing to make the wiring easier. I just did a log book entry. My IA was cool with that.

 

Also the Davtron probe fit in the hole the original probe was in so I didn't have to drill any more holes in the plane. It was in an inspection panel. I just swapped the panel to the other wing.

[N201MKTurbo]

I chcked mine with two different laser thermometers. The kind you put the dot on the target and pull the trigger. All three said 57 F.  I'd say its accurate to one degree.

 

The laser (IR) thermometers are highly dependent on the emissivity of what you are trying to measure. They work great if you are trying to find a dead cylinder on an engine or a hot or cold spot in your house, but I would hesitate to use their reading to calibrate anything.

[Shadrach]

Some/many IA's will default to calling anything a major alteration just to CYA, and force the decision making (or liability trail) further up the food chain.  It is silly, but today's regulatory environment breeds such behavior.

It does, moreover, young and/or inexperienced FSDOs begin to believe it's major just because they've seen paperwork submitted by the last guy. I understand the "CYA" aspect, but the wording is relatively clear. I think it's a tough sell to say that the installation of an EI-EAC-1 meets the threshold of (1) or (2)... Any IAs care to ring in?

14 CFR Part 1.1

Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications -

(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) That is not done according to accepted practices or cannot be done by elementary operations.

[Awqward]

Thanks Ross....I may end up having to put that to the IA because at the moment he says he can't submit the 337 without an 8130-3.....If a 337 isn't even required it takes the wind out of his sails a bit...I pointed out that that the STC has an AML which covers the M20J (so that's Acceptable Data) so it comes down to him being satisfied that the unit itself is airworthy...for which he would normally rely on an 8130-3.....can anyone suggest an alternative means for the IA to satisfy himself as to the airworthiness of the actual unit? If I can crack that...case closed!

[N201MKTurbo]

Thanks Ross....I may end up having to put that to the IA because at the moment he says he can't submit the 337 without an 8130-3.....If a 337 isn't even required it takes the wind out of his sails a bit...I pointed out that that the STC has an AML which covers the M20J (so that's Acceptable Data) so it comes down to him being satisfied that the unit itself is airworthy...for which he would normally rely on an 8130-3.....can anyone suggest an alternative means for the IA to satisfy himself as to the airworthiness of the actual unit? If I can crack that...case closed!

 

There should have been an 8130 delivered with the unit. if it is not in the log contact the vendor to see if you can get a copy.

[Shadrach]

I'm pretty sure this is a minor alteration per the FAAs decision flow chart.

[Awqward]

I called Electronics International....they don't supply an 8130-3 as a matter of course...it has to be requested....the previous owner clearly didn't request one....and once the unit is shipped an 8130-3 cannot be issued retrospectively....I did email back and ask if they could issue a Certificate of Conformance based on the Serial Number....still waiting for a response....at the same time I am trying to convince the IA that he actually doesn't need either...

[Awqward]

Thanks again Ross...although because there is an STC with an AML there is no requirement for a Field Approval....but the flowchart is very useful

[Shadrach]

Thanks again Ross...although because there is an STC with an AML there is no requirement for a Field Approval....but the flowchart is very useful

I agree. It looks like this is a log book entry and that it was made before you purchased the plane... Your MX is hung up on the fact that it is acting as a primary instrument now. But I see no reg that makes it a major alteration because of that.  Don't feel bad, your IA is not the first to end up in a regulatory "catch 22" chasing his tail.  The IA that installed our JPI also wrote it up as minor (he's with the FAA now). My current IA got his panties in a wad over it, so I had him call the dude that originally installed it. He asked a series of questions to lead my IA to the Major vs Minor understanding and they finnaly arrived at the conclusion that a log book entry was all that was needed. Hi credentials probably did not hurt.

[Awqward]

I just got a response from EI....they will issue a CoC...so hopefully that will enable the pernickity IA to go ahead with the 337....even though I agree that it should only be a minor alteration and notwithstanding Scott's observation that it is contributing to the misconception between Minor and Major...

[KSMooniac]

Good luck.  What a fiasco for such a minor instrument replacement!  Be glad you're not installing a GPS or something similar...

[Awqward]

One interesting observation: Just reading Part 21E on STCs, it implies that an STC is only required when there is a Major design change....at the risk of breaking the rules of logic, does this mean that if there is an STC it is implied that the alteration is Major? I don't think that logic holds up, but it may explain the CYA apporach...

[KSMooniac]

That is more of the CYA approach... there are plenty of cases IMO for STC's and minor changes, like engine monitors that don't replace anything for example.  

[jetdriven]

The laser (IR) thermometers are highly dependent on the emissivity of what you are trying to measure. They work great if you are trying to find a dead cylinder on an engine or a hot or cold spot in your house, but I would hesitate to use their reading to calibrate anything.

 

Sure but the thermometer in my car, the wall on the shop, and the Wunderground site on my iPhone all also said 57 F. Im pretty sure that the probe is accurate.  Far more so than the inop Westach guage I removed and the thermometers that stick through the windshield.