Cessna fuel sender and fuelsenders.com

Well, it's back in the plane and working well. I did not get a chance to see the repaired part before it went back in, but my A&P says it didn't look any different, besides cleaned up. (Not surprising, the changes to the design are reportedly subtle.) He indicated that it went in cleanly, was appropriately calibrated, and the gasket looks substantially similar to Cessna's and worked just fine.

Turn around was better than promised. I was told 5 days. He turned it around in less than 48 hours. Some of that had to do with my A&P marking it P1 went he sent it in. Paul called me and apologized that he could not get it back in 24 hours, and I told him that it wasn't really P1 and to relax a little. Otherwise it would have been even faster. Most of the time was spent on overnight shipping, not repair.

Paul Malakian, who is the one-man shop doing the work, seems like a great guy. He's insanely chatty, and my only concern about the warranty and $100 repairs is that he's past due to retire. I did not ask his age, but he was talking about jewelers school that he graduated from in the early '50's. But it's not much of a concern: this one service alone without the warranty or the $100 repair is much better than getting the part from Cessna.
 
Why Fuel Gauges Suck in GA

In the 1950’s when a majority of GA aircraft were designed, the aircraft manufacturers in the USA turned to automotive fuel senders and equivalent gauges made by the same manufacturer - AC DELCO or in some cases Stewart Warner.

These gauges and senders were produced by the millions for the primary automotive application Buicks and Cadillacs in the mid 1950's. I get a sense looking at these senders and gauges now 50 or 60 yrs later that there was a sense of pride, they did last far longer than they should have. But even 50 yr old automobiles have issues.

The trouble with these automotive senders is that they are:
  • Made of Steel.
  • Only in production for a few years. (more of this later)
Fuel tanks for both applications automobile and aircraft in the 1950's were very similar in size

  • The sender and gauge face size that were matched. The indication size allowing for the automotive requirement to provide a warning of impending fuel starvation. The intended purpose of a fuel gauge.
  • Interesting note: in that automotive systems are biased to show a faster fall in fuel level from 1/2 tank to zero - the Big Three were trying to keep car owners from running out of fuel. That clever manipulation is still being used in automobiles today.
Now because aircraft are aluminum we have introduced dis-similar metal corrosion. Steel sender body and aluminum aircraft tank or structure.

NOTE: Rochester Gauges senders have aluminum cast bodies. About time this occurred at the - 1995 re-introduction

Water vapor introduced on descent is one of the reasons we sump the tank before flight. But water vapor also condenses on the steel sender body.

Water increases the rate of galvanic corrosion.

NOTE: Bladder tanks with rubber concentrate the corrosion on the sender body

The aluminum is more susceptible - and this shows up as an intermittent ground connection - Some manufacturers isolate the sender body for this reason

The other factor is latent time - If the sender were washed regularly with fuel - corrosion has a less likely time to take hold. Most automobiles now sink the sender below 1/2 tank of fuel &some place the sender function at the bottom of the tank for this reason.

Most aircraft sit idle for relatively long periods of time, which doesn't help.

We should replace the senders every so often, yes that would be a good plan - the only issue is that that particular automotive/tractor sender is no longer made.

  • What we have found is that fuel senders of the traditional type typically last only 12 years in aircraft applications on average and the subsequent rebuilds carry an average life of 1/2 the previous life
-------------------------
Cessna in this case already has another sender manufacturer in place after Rochester Gauges and another vendor is waiting in the wings.

Rochester is restricted from selling you this sender from a signed Product Support Agreement - So this sender is not available at preferred pricing as if it were in production.

Cessna has asked owners to update the whole fuel sender system when replacing senders - remember those automotive senders only lasted for a decade or so in production. As each sender system ( AC/Delco, Stewart Warner, Rochester) had different operating parameters. Cessna still stocks conversion kits for older sensors in 172's for newish Rochester senders and gauges

RARELY IF EVER is this done -

What we get is a mishmash of senders in older Cessna aircraft reporting to the original gauge that may or typically may not have been designed for.

SO WHY ARE AIRCRAFT FUEL SENDERS CRAP

---If they are original they are corroded beyond recognition (Think Titanic)
---If they were replaced, nearly every pilot looked for the quick fix and not the engineered solution offered by the manufacturer.
---As the original poster stated - if nobody was looking over his/her shoulder - it wouldn't get done.
---If some mechanic offered to do it for fractional AMU's that is what would be accomplished.
---Aircraft parts have always been expensive for pilots - Low volume and regulatory oversight have been a watchword forever

Capacitance by the way is crap in AVGAS aircraft for a lot of the reasons above - Cessna gave up on the Pennycap system back in 1985 - to much maintenance
 
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Scott Philiben said:
SO WHY ARE AIRCRAFT FUEL SENDERS CRAP

---If they are original they are corroded beyond recognition (Think Titanic)
---If they were replaced, nearly every pilot looked for the quick fix and not the engineered solution offered by the manufacturer.
---As the original poster stated - if nobody was looking over his/her shoulder - it wouldn't get done.
---If some mechanic offered to do it for fractional AMU's that is what would be accomplished.
---Aircraft parts have always been expensive for pilots - Low volume and regulatory oversight have been a watchword forever

Capacitance by the way is crap in AVGAS aircraft for a lot of the reasons above - Cessna gave up on the Pennycap system back in 1985 - to much maintenance
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Nice post. With a screen name of fuellevel, I'm guessing this is you: https://www.linkedin.com/in/scott-philiben-796a4b4 (You should totally take the linkedin.com/in/fuellevel vanity name!)

I did see your system come up in my search (assuming I've got the right person). Didn't seem to be an option for my 172S. Looks like you've switched out the pot for an optical encoder? That's makes a ton of sense. Curious if you have averaging in the sender to damp out the bumps or if you're depending on the gauge for that.

My original fuel sender had a Rochester deposit-film pot. My understanding is that Cessna is going back to the wirewound pot, but it isn't ready yet. You guys planning an STC for 172? It's a 2003, so it should not have gotten to the point of terrible corrosion. I didn't see the original before it was sent for overhaul, so I can't comment on what it really looked like. Paul indicated that he routinely sees senders with only about 60 hours on them at failure for the deposit film pots. 60 hours! (Of course, his sample is skewed toward the failures, as he does not see the ones that never have problems.)
 
@Scott Philiben , I just dug into your site deeper and realized that you do have an option for my aircraft via 337. And the price is actually right on par with other options at $395 per side. But...it does require a digital engine monitor certified to replace the primary fuel gauges. And replacing both sides. Wish my A&P had offered me that solution. Would have been 2 to 4 AMU instead of a bit less than 1, but would have fixed the problem for all time. Something I would have considered.

It wasn't super-obvious from your website that there were such options. I looked in the Applications tab, noted the Cirrus and Vans entries (coupled with the Cirrus banner on the frontpage), and came to faulty conclusion that that was all there was. Digging into the Applications -> Aircraft -> Aircraft Kit Pricing menu finally located the info I needed, though a few weeks late. It's also not particularly obvious how to buy one.

If/when the other tank gives out, I'll definitely consider one of your systems.
 
arnoha said:
Nice post. With a screen name of fuellevel, I'm guessing this is you: https://www.linkedin.com/in/scott-philiben-796a4b4 (You should totally take the linkedin.com/in/fuellevel vanity name!)

I did see your system come up in my search (assuming I've got the right person). Didn't seem to be an option for my 172S. Looks like you've switched out the pot for an optical encoder? That's makes a ton of sense. Curious if you have averaging in the sender to damp out the bumps or if you're depending on the gauge for that.

My original fuel sender had a Rochester deposit-film pot. My understanding is that Cessna is going back to the wirewound pot, but it isn't ready yet. You guys planning an STC for 172? It's a 2003, so it should not have gotten to the point of terrible corrosion. I didn't see the original before it was sent for overhaul, so I can't comment on what it really looked like. Paul indicated that he routinely sees senders with only about 60 hours on them at failure for the deposit film pots. 60 hours! (Of course, his sample is skewed toward the failures, as he does not see the ones that never have problems.)
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Yes that is me

Actually we just did a 182T the other day - Billings Aerotronics did the work, they signed it off as a logbook entry. This system reports to Garmin

Our senders are TSO'd and I didn't include the STC yet - (which your aircraft is on) as it isn't quite signed - I need to get an 8110.3 for Software

Textron - as far as I know is going with us next year and we can replace your sender with our technology. That is Cessna's intent, I have the specification control drawings in front of me.

Funny you should mention an optical encoder - we tried that with a grey code - it didn't work as well as we thought it would and it is patent protected

We use an Anisotropic Magneto Resistance sensor- so it is entirely out of the fuel volume - pretty neat technology
and yes we have intelligence onboard the sensor - so we can manipulate output to be suitable for any application.

The Rochester is better from a corrosion standpoint - but I have lots of failed Rochester Gauge products - both wire and film
Just for fun we included it the vibe test - it fell apart before 30 seconds was up, It would never ever last the several hours and several sessions the test was run on our sensors in a vibe schedule. I am not big on Rochester Gauges - the propane senders I have on my RV are just as bad.

 
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I'm glad somebody is putting effort into fuel gauging systems. It seems like it has been way under developed.

That being said, anyone that believes the typical float in their car would outlast the one that came with a typical 1980s airplane might be stretching it.

My Stewart Warners are 49 years old with 1800 hours on them. They still function astonishing well. The old Cessna 150B I had was about the same age with around 4500 hours on it. The senders were flaky, why would anyone expect otherwise? 4500 hrs of bouncing around, wing rolling, slips, sloshing, vibration, Umh...DUH?!? That's about (400,000 miles of use give or take).
 
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arnoha said:
I just dug into your site deeper and realized that you do have an option for my aircraft via 337. And the price is actually right on par with other options at $395 per side. But...it does require a digital engine monitor certified to replace the primary fuel gauges. And replacing both sides. Wish my A&P had offered me that solution. Would have been 2 to 4 AMU instead of a bit less than 1, but would have fixed the problem for all time. Something I would have considered.

It wasn't super-obvious from your website that there were such options. I looked in the Applications tab, noted the Cirrus and Vans entries (coupled with the Cirrus banner on the frontpage), and came to faulty conclusion that that was all there was. Digging into the Applications -> Aircraft -> Aircraft Kit Pricing menu finally located the info I needed, though a few weeks late. It's also not particularly obvious how to buy one. If/when the other tank gives out, I'll definitely consider one of your systems.
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I appreciate the feedback - I will try to fix the issues you found. We report out to any FAA Approved gauge (i.e. the existing Rochester Gauges) the issue is that we need both a Tank profile and a Gauge profile to accomplish this effectively, when we have both we make analog gauges hum. But for supporting the aftermarket - it is best to have a digital gauge with it's own tank calibration. Customers are satisfied faster and the digital gauges I reference, have a few new safety features. Yes we fix fuel gauges permanently and they are accurate and reliable - most importantly ...... trusted.....
350,000 operational hours - No unscheduled removals.

We have lots of legacy Cirrus aircraft on leasebacks that faced the same issue as you - None of those aircraft have been rejected for faulty fuel indication to this date - some were our aftermarket very first adopters. They jumped to address the issues you faced, but now find fuel planning to be simple for the SR20 and the various loads they want to carry, same would be true for the 172. They do it with confidence.

Our business is primarily OEM - there is a lot of resistance to accurate fuel quantity in GA with current pilots. I am poking at them on POA
 
but83: Thanks for that - I heard that a lot at Oshkosh - Glad that somebody took on GA fuel quantity, about 20 times an hour. We really did fix it, as Cirrus stated we put a nail in the issue
funny thing is, that it wasn't really that hard.

Like I said - it appeared that the original senders were built with some pretty good tooling and processes - State of the Art 50 years ago
they would have to be, to have lasted this long.

I can say that when I get old set in to pattern a new set - I test the senders and gauges - both are usually crap and then I put them together and like an old successful married couple they seem to work

NO EXPLANATION
 
Scott Philiben said:
Our business is primarily OEM - there is a lot of resistance to accurate fuel quantity in GA with current pilots. I am poking at them on POA
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I figured your business is primarily OEM given the direction of the website. That may be why I didn't scrutinize it enough to find the info I needed. "Oh, 172 is just too small a business when they're mostly doing big jets. Won't be anything here for me..." Turns out, I'm happily wrong!

What do you anticipate the cost will be once Cessna makes it official? Still $800 for the parts? Cessna has a habit of pricing parts to the moon.

Either way, sounds like I made the right decision. By the time the next one fails, the whole STC for my aircraft is likely to be ready. Seems I've bought just enough time to get there with the overhaul.

Also, I'm disappointed you haven't taken in/fuellevel yet... ;)
 
I am looking into it as we speak - couldn't locate how to do it - will have to use HELP

We are just scratching our way upward - there is a lot of FLOAT discrimination to overcome
but we have lots of Jet A platforms in the works

I have no idea on pricing from Cessna - but I would expect it to be all that

They want to put a program together for all re-start aircraft - so I would expect a bit of marketing
 
Scott Philiben said:
I am looking into it as we speak - couldn't locate how to do it - will have to use HELP

We are just scratching our way upward - there is a lot of FLOAT discrimination to overcome
but we have lots of Jet A platforms in the works

I have no idea on pricing from Cessna - but I would expect it to be all that

They want to put a program together for all re-start aircraft - so I would expect a bit of marketing
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On the desktop site,

Menu -> Profile -> Edit Profile
Call to action dropdown left of your connection count (500+ for you) -> Manage public profile settings
Upper right, Your public profile URL, then the pencil icon by the vanity url
Set a new one!

Then you'll have one like mine: http://www.linkedin.com/in/arnoha
 
Here is the first OEM aircraft and the first owner - interestingly a leaseback owner
 
Bleh. The right side is acting up again in exactly the same way. It's in annual right now, so I'll find out soon what the real verdict is. Makes me wonder if it was never the fuel sender, but rather something else in the chain. I finally observed the symptoms directly, instead of just relying on reports from my A&P and renters. The right-side fuel gauge drops to zero for some period of time and the LOW FUEL light for the right side lights up. Sometimes it's so short that only flickering of the low fuel light is seen. Sometimes it sticks on zero for a few seconds to 10's of seconds. Never seen it exceed a minute, but I believe my renters have. It appears accurate when it is reporting a number. It's done it when the engine is running and off. It's done it on the ground and in the air.

It's under warranty if it turns out to be the sender itself. Still going to be stuck with a labor charge, of course. @Scott Philiben any news on the STC? Seriously considering it if this turns out to be a bigger deal than a warranty repair.

EDIT: Also, in rereading this thread, I just realized you had said that optical encoders and grey code are under patent. How the hell is that possible? Both are super-basic technologies and techniques.
 
Yeah I know - sorry to replay 30 days later but that is what I found doing a search. Frankly using Hall Effect is just as easy and there are 20 or so patents there for fuel level. We have your configuration - we fix the problem permanently
 
Update: The problem was intermittent enough that it didn't come to a head until now. Looks like it will need to go to warranty, so I contacted Instrument Rebuild. Turns out Paul Malkasian passed away in November. I was sorry to hear that. Only talked to him on the phone, but he was definitely a character and seemed to be a good guy. Fortunately, his son, Bill, is honoring the warranty, so we'll see what happens. I'll be sending it up in May to get fixed again. I'll post another update in mid to late May.

If it acts up again after that, I'm definitely considering @Scott Philiben 's system. I have zero trust in the Cessna film-based pots.
 
It will that is the design nature of a potentiometer in a fuel volume - or fix the problem permanently as we guarantee them for life
 
We hold TSO Approval and we are STC'd - What component part of 21.303 are you referring to?

06238d4ed7e48ba341b924945826d259
 
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weirdjim said:
Y'all want to read 21.303(b)(2) REAL CAREFULLY.

Jim
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I'm confused. How does the owner-produced parts verbiage apply at all in this situation? Cryptic hint is cryptic.

§21.303 Replacement and modification parts.
(a) Except as provided in paragraph (b) of this section, no person may produce a modification or replacement part for sale for installation on a type certificated product unless it is produced pursuant to a Parts Manufacturer Approval issued under this subpart.
(b) This section does not apply to the following:
(2) Parts produced by an owner or operator for maintaining or altering his own product.
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arnoha said:
I'm confused. How does the owner-produced parts verbiage apply at all in this situation? Cryptic hint is cryptic.
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It means that if the owner of the aircraft wishes to manufacture that sender for him/herself that it is legitimate to do so. That is far less expensive than the other options.

Jim
 
weirdjim said:
It means that if the owner of the aircraft wishes to manufacture that sender for him/herself that it is legitimate to do so. That is far less expensive than the other options.

Jim
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You've got more skills than I do. I can't make one of these by myself for anything like a reasonable price.

s-l1600.jpeg
 
Capt. Geoffrey Thorpe said:
https://www.amazon.com/Bosch-SP0F00...coding=UTF8&psc=1&refRID=048RGMFPYGAFRCCWNMHX

Same thing.
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Yep, and the guidance letter from the FAA's General Counsel (the Fed Shyster) says that you can take ANY subassembly (like this Bosch sender), modify it to your own drawing, and use it on your own airplane IF it can be shown to perform in form, function, and fit to the original part.

You don't REALLY think that CessPipMooBee manufactures all those Buick alternators and Ford door handles on our airplanes, do you?

Jim
 
weirdjim said:
Yep, and the guidance letter from the FAA's General Counsel (the Fed Shyster) says that you can take ANY subassembly (like this Bosch sender), modify it to your own drawing, and use it on your own airplane IF it can be shown to perform in form, function, and fit to the original part.

You don't REALLY think that CessPipMooBee manufactures all those Buick alternators and Ford door handles on our airplanes, do you?

Jim
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Which interpretation are you referring to?
 
weirdjim said:
I don't understand the question. So far as I know the FAA Chief Counsel has only written one opinion on this matter.

Jim
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Sorry, I didn't know that there was only one. What is the name used in the interpretation? So I can follow along as well.
 
JAWS said:
Sorry, I didn't know that there was only one. What is the name used in the interpretation? So I can follow along as well.
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Here you go:

Memorandum
U.S. Department of Transportation
Federal Aviation Administration
Subject: INFORMATION: Definition of \"Owner
Produced Part,\" FAR 21.303(b) (2)
Date:
AUG
5 1993
From: Assistant Chief Counsel for Regulations,
AGC-200
Reply to Attn. of:
To: Manager, General Aviation and Commercial
Branch, AFS-340
This responds to your memorandum, dated April 8 to Senior Attorney Mardi Thompson, in which you asked for a definition of
\"owner (or operator] produced part,\" as described in Federal Aviation Regulations (FAR) Section 21.303(b) (2). You asked several questions in your memorandum. We answer your questions in the order you asked them. Attachment A provides a background foundation for our answers. The answers should frame a workable definition of how to determine if the exception in FAR 21.303 (b) (2) applies.
We answer your questions as follows:
First question: Does the owner have to manufacture the part himself, in order for the part to be considered an “owner produced\" part? Answer: No. An owner would be considered a producer of a part if the owner participated in controlling the design, manufacture, or quality of the part. We would look at many factors in determining whether a person participated in controlling the design, manufacture, or quality of a part. The following would tend to indicate the a person produced a part:
1. The owner provided the manufacturer with design or performance data from which to manufacture the part. (This may occur, for instance, where a person provided a part to the manufacturer and asked that the part be duplicated.)
2. The owner provided the manufacturer with materials from which to manufacture the part.
3. The owner provided the manufacturer with fabrication processes or assembly methods to be used in the manufacture
of the part. .
4. The owner provided the manufacturer with quality control procedures to be used in the manufacture of the part.
5. The owner supervised the manufacturer of the part.


We would not construe the ordering of a part, standing alone, as participating in controlling the design, manufacture, or quality of a part.
Second question: Can the owner contract for the manufacture of the part, and still have a part that is considered an \"owner produced\" part? Answer: Yes, in certain circumstances. The owner would still be considered a producer of the part if he participated in controlling the design, manufacture, or quality control of the part. Note that, as explained in Attachment A, the person with whom the owner contracted would also be a \"producer. II
Third question: Can the owner (merely) supervise or assume responsibility for a mechanic manufacturing the part for the owner, and still have a part that is considered an \"owner produced\" part? Answer: Yes, with respect to supervision. Owner supervision would indicate that the owner participated in controlling the design, manufacture, or quality of the part. A common example would be where an air carrier mechanic manufactured a part for installation on the air carrier's aircraft; the part produced would be owner or operator produced. We are not sure what you meant by the owner \"assuming responsibility\" for manufacture of a part. If your reference was to something other than participating in controlling the design, manufacture, or quality control of the part, our opinion is that the owner probably would not be determined to have produced the part.
 
Part two, because the folks that designed this board limited it to 10,000 characters (why???)

Fourth question: Can an owner contract with a non-certificated individual to manufacture a part for use on the owner's aircraft, and still have a part that 1S considered an \"owner produced\" part? Answer: Yes, in certain circumstances. If the owner participated in controlling the design, manufacture, or quality of the part, the part would be considered to be produced by the owner. However, as explained in Attachment A, the non-certificated person would also be considered a \"producer.\"
Fifth question: If a mechanic manufactured parts (e.g., wing ribs) for an owner, and the parts were associated with a repair the mechanic was performing, would manufacture of the parts be considered maintenance associated with the repair, or production of a part by the owner for maintaining the owner's aircraft? Answer: It could be one or the other; in neither case, however, would there necessarily be an FAR violation. If it was concluded that the owner participated in controlling the design, manufacture, or quality of the part, he would be a producer, and the exception in FAR 21.303(b) (2) would apply. Therefore, the mechanic would not be in violation of 21.303(a)


As noted above, prior to Amendment 21-41, FAR 21.303(a) prohibited each person producing a replacement or modification part for sale for installation on a type certificated product from doing so without holding a PMA. In Amendment 21-41, the FAA amended FAR 2l.303(a) to allow a PMA holder to contract with a subcontractor or supplier to manufacture a modification or replacement part under the holder's PMA In that amendment, the FAA recognized that a modification or replacement part can conform to the approved design data and be safe for installation on a type certificated product, as long as the part is produced under an approved fabrication inspection system (FIS).
Amendment 21-41 did not specifically address who \"should have held the PMA\" where the part was produced in the absence of a
FMA. However, any interpretation of FAR 21.303(a) should be consistent with the focus in that amendment on the establishment and maintenance of the FIS; therefore, we submit that 21.303{a) creates liability for production of a modification or replacement part for sale for installation on a type certificated product for each person who:
1. Participates in controlling the design, manufacture, or quality of the part.
'\"-
2. And does so with the intent that the part be sold for installation on a type certificated product.
We would look at many factors in determining whether a person participated in controlling the design, manufacture, or quality,
_of a part. The following would tend to indicate that a person participated in controlling the design, manufacture, or quality of a part (i.e., \"produced\" the part):
1. The person provided the manufacturer with design or performance data from which to manufacture the part. (This may occur, for instance, where a person provided a part to a manufacturer and asked that the part be duplicated.)
2. The person provided the manufacturer with materials from which to manufacture the part.
3. The person provided the manufacturer with fabrication processes or assembly methods to be used in the manufacture of the part.
4. The person provided the manufacturer with quality control procedures to be used. in the manufacture of the part.
5. The person supervised the manufacturer of the part.
We would not construe the ordering of a part, standing alone, as participating in controlling the design, manufacture, or quality of a part.


- - --
- ----

One other issue needs to be addressed. Section 21.303(a) prohibits a person from producing a part for sale for installation on a type certificated product when the part is not produced pursuant to a PMA. The general intent of the proscription in FAR 21.303(a) is to prevent the introduction of an unapproved part into the aviation stream of commerce, where it could be subsequently installed on a type certificated product(s). The terms of 21.303(a), including \"for sale,” are defined in that context.
Notwithstanding that repair stations and mechanics bill their customers for parts, along with the labor of installing parts, those entities produce the parts for the purpose of accomplishing maintenance on products, limited to those products brought in by their customers. As described in Order No. 8000.50, a repair station may produce a replacement or modification part, under FAR Parts 43 and 145, for an STC modification or a field-approved repair or alteration, given certain circumstances that assure quality control of the part produced. Compliance with Part 43 gives the assurances of the quality control for a part produced by a Part 65 mechanic. In addition, compliance with the maintenance recordkeeping requirements memorializes the circumstances of production and installation of the part. Accordingly, the objectives of Subpart K are achieved when a part is produced by a repair station or mechanic for installation on a customer's product: the installed part is introduced into the aviation stream of commerce with the necessary evidence of the part's suitability. Thus, one can conclude, as a matter of law, that a repair station or mechanic has not produced the above-described part \"for sale\" for installation on a type certificated product, as defined in the context of 21.303 (a).


Attachment A
Background
Section 21.303(a) of the Federal Aviation Regulations (F&~) states:
Except as provided in paragraph (b) of this section, no person may produce a modification or replacement part for sale for installation on a type certificated product unless it is produced pursuant to a Parts Manufacturer Approval issued under this subpart.
Section 21.303(a) appears to contemplate that more than one person can '''produce'' a modification or replacement part. We base this observation on the following:
1. The regulation proscribes certain behavior unless the part is produced pursuant to a PMA; it does not specifically state that each person who is producing the part must hold a PMA. In fact, prior to Amendment 21-41, FAR 21.303(a) prohibited each person producing a replacement or modification part for sale for installation on a type certificated product from doing so without holding a PMA. In Amendment 21-41, the FAA amended
21.303(a) to allow a PMA holder to contract with a subcontractor or supplier to manufacture a modification or replacement part under the holder's PMA. That amendment recognized that more than one person can participate in the production of a part.
2. The only meaningful interpretation of FAR 21.303(b) accommodates the view that a modification or replacement part can be \"produced\" by more than one person. Section 21.303(b)(2) excepts from the PMA requirement of 21.303(a) “[p] arts produced by an owner or operator for maintaining or altering his own product. II If the 21.303(b)(2) exception were to apply only when the owner or operator produces the part, it would only except from 21.303(a) the production of a part produced by the owner or operator for sale to himself. This result would be illogical. Thus, 21.303(b)(2) must be interpreted as addressing the situation where a part is produced by an owner (or operator) and also is produced by another person.
.



If it was concluded that the mechanic produced the part for the purpose of effectuating the repair, the question would remain whether the mechanic would be in violation of 21.303(a). We submit that the mechanic would not be in violation of 21.303(a), because, as explained in Attachment A, the mechanic did not produce the part for sale for installation on a type certificated product.
We hope the above answers respond to your needs. For further discussion, please telephone Carey Terasaki, AGC-210, at
(202) 267-80
 
Thanks. Very interesting.
 
Interesting, @weirdjim . So...given that it's almost certainly the pot that's bad, I can drill out the rivets and replace that with an equivalent part stolen from an auto part and I'd be good? The one referenced by @Capt. Geoffrey Thorpe doesn't work, as it's in the wrong range. It would have to match both the resistance range and the mechanical range. It would also probably be preferred that it ground on the body, since the original does that and I wouldn't want to have to secure a ground wire where none had been before.

I want @Scott Philiben 's system in my plane, but it would be on the order of 4 AMU for a minimum install and 7 AMU or so if I went with a primary engine monitor (EI CGR-30P fits my plane best). If I went that route, I'd probably do the primary engine monitor, as it would replace several instruments. Can't justify it just yet.
 
This is a great example where fixing a plane can either cost 4AMU or 40USD. If you intend to make money in a leaseback, I'd suggest the 40USD option.
 
mtuomi said:
This is a great example where fixing a plane can either cost 4AMU or 40USD. If you intend to make money in a leaseback, I'd suggest the 40USD option.
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Well, it ain't $40, because even with an owner part, I still have to burn at least a couple hours of A&P time to get it out and installed again. Let's call it $300. Also, my time to fix the part is worth something. Let's say it takes me a couple hours to fix it and we'll use the same shop rate as an approximation. So...$500 best case. Still a half AMU. And that's assuming it works right the first time. It's an interesting idea, but short of explicit instructions and part numbers for my model of aircraft, I still can't do it for a price and risk that compares with just getting the overhaul done. (And this time it's a warranty repair and the warranty is being honored.)
 
arnoha said:
Well, it ain't $40, because even with an owner part, I still have to burn at least a couple hours of A&P time to get it out and installed again. Let's call it $300. Also, my time to fix the part is worth something. Let's say it takes me a couple hours to fix it and we'll use the same shop rate as an approximation. So...$500 best case. Still a half AMU. And that's assuming it works right the first time. It's an interesting idea, but short of explicit instructions and part numbers for my model of aircraft, I still can't do it for a price and risk that compares with just getting the overhaul done. (And this time it's a warranty repair and the warranty is being honored.)
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I guess there's the reason why you find it difficult to turn a profit on a leaseback. Your A&P rapes you if he charges a couple of hours for that.
I would go and pull it out (no A&P needed), it's what, 5 minutes a side?, do the mod (make sure the pot is 6ohm +-5ohm tank empty and 90ohm +-5 tank full), and take it to an A&P to accept and reinstall. $50 for the A&P, call it $50(2 hours) in my time, and $40 (less than that actually) in parts.
 
I am betting our solution is an 2 AMU and the problem is resolved forever. No fiddling - no jury rigging. Problem solved
 
Scott Philiben said:
I am betting our solution is an 2 AMU and the problem is resolved forever. No fiddling - no jury rigging. Problem solved
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How does that break down? I'm currently looking at an AMU, as it looks like the fuel sender is not repairable, so that is now pretty tempting.

EDIT: Sent in a quote request, too, at your website.
 
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Tempting enough to pull the trigger. Let's see if these Cies units work as advertised!
 
I'll start a new thread for the CiES units, which I just received, but wanted to round out the story on Instrument Rebuild.

It didn't work out. The overhauled unit was sent back under warranty, but was unrecoverable. Rochester also apparently went radio silence with them, and would not help them get a replacement pot. They're sending the unit back, cleaned and overhauled, but still with the original issue. Ultimately, I think they're doing a valiant effort to resuscitate a garbage part from Rochester. But even they can't make this pig smell good.

And when I say "they", I mean "he". The shop used to be a one-man shop. Unfortunately, Paul Malkasian passed away shortly after repairing my sender. I was grateful that his son, Bill, took the unit and attempted to honor the warranty.

In the end, I think I might use their shop to overhaul a unit that didn't come from Rochester. However, the Rochester parts in the SP are such trash that it's just too much headache. Assuming the CiES units do as they say, they should be a clearly better choice here.
 
I'm taking a fresh look at the Pennycap fuel system as an electronics engineer. I tried to fix a fuel monitor before it was sent back as a core ($750!!). It had a good side and a bad side, so I had some opportunity to look at it on my test bench. Here's what I found.

1) The "wired-in-parallel" fuel sensors on one tank side apparently "average" the fuel level when banking. A very simple concept, but apparently works. Fuel goes up on one, down on the other. Voila!

2) The sensors are merely capacitors. a tube with a rod up the center. Dirt simple, Highly reliable. I know, I know, someone said it fails. No, I think it's the wiring, not the sensor. Unless there is a known problem with contaminants "shorting out" the capacitive tube/rod, I don't think they fail. Maybe the connections go bad. But not the sensor itself. Think about it. Do butter knives fail? These are just as simple. No moving parts.

But... having said that, I am very suspicious of the coax cable wiring. If the shield grounding is insecure, two things happen. One, you now depend entirely on the airframe for the return path. Real bad! Two, the shield provides no protection for low frequency noise from the airframe. Also bad. This circuit is dependent on 100 to 300 picofarads of variation, to make it work. Picofarads!! If you wave your hand past it, it will change. In fact, test it by unplugging the wing tank connector from the fuel monitor box and touch the 1-pin Molex pin with your finger. You should see wild swings on the dash gauge. Test it. It is very sensitive. Don't worry - you can't damage it, if you ground your body first.

3) The dash gauges are also dirt simple. Right out of a car. They are driven by 100-300 micro-amps of current. Very small current. If anything is corroded or loose, the gauge itself can become sporadic. If both gauges move the same way in a failure mode, check the 28V supply on the other side of the gauges. The fuel monitor supplies the 'grounded' side of each gauge. If you short the gauge input to ground, through a 10K ohm resistor (to be safe), it should fully deflect.

4) The Fuel Monitor is also dirt simple. It is a 1960's design with 15 transistors and a bunch of resistors and capacitors. Any of the electrolytic caps can go bad. The transistors are ancient and the JFETs require a modern replacement. What makes the circuit board difficult is that the ingenious designer "overlapped" the functionality of several circuits to minimize the needed transistors. It is basically a capacitance to current converter. But not as intuitive as I suspected. Today, I would replace it with about 4 major components. I may try to redesign it, as a replacement for all these funky boxes, but that requires jumping through all the FAA malarkey.

Currently, I am reverse engineering the circuit board. I have the assembly drawing done and most of the schematic. But I need to simulate the circuit to prove I have it captured correctly. I have already had opportunity to "view" the operation of a good circuit, with test equipment, and I think I understand most of it. It's not that complex. But I need to complete my analysis so I have an accurate schematic and completely understand how it works. Then I can fix any of the problems and possibly redesign it. But it is so simple, it is almost not worth the STC hassle to make a modern version. I might do it just for fun. If I do, and someone wants a kit, that's your headache, not mine.

Ultimately, I will at least provide a troubleshooting manual and how to make repairs. I suspect these boxes are currently repaired with a shotgun approach because they don't have time to understand the beast. This stuff is way too expensive because of availability of "working" units. There is no way this bunch of parts should cost $1,000. No way. Let me see if I can change that. I may create a cottage business.

Yeah, I get it, Mr. Smart Guy. The FAA will be all over me in a flash. Not if I affect the repairs and someone else verifies it, and signs the yellow tag. Depending on what it costs to become a "Repair Station", I may go into that business too. I'm a belligerent son-of-a-gun. Watch and see. If nothing else, you'll benefit from what I find.


Dan Smith
thepilot@all3smiths.com
KLMO
N758FV
 
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