The International Cessna 170 Association

I don't have the responsibility or authority to approve parts...so I can admit I don't have an answer for that question. But I believe it's correct to say that the IPC is a catalog only.... for the purpose of ordering parts from Cessna or other suppliers. Whether it can be used to identify whether or not a particular item is interchangeable with others... is a horse of a different color (as the Wizard would say.)

If the parts catalog isn't an approved source of which parts are legit, what other source is there to use for mechanics to verify part numbers ?

The aircraft's manufacturer.
IPC's. To this day, the IPC is not considered to be part of the data set provided by the manufacturer to the regulatory system for use in approving an aircraft's in the certification process.
As well IPC's could never keep up with the changes that are made in the parts that make up a modern aircraft. Mistakes happen all the time, sometimes with interesting results. A part has been replaced by another but the IPC doesn't mentioned it's also installed on the other wing and when you replace one, you replace them in pairs. Part is changed, aircraft takes off for test flight and promptly wants to do some acrobatics. Has happened more than you'd like to know.

lowNslow wrote:If the parts catalog isn't an approved source of which parts are legit, what other source is there to use for mechanics to verify part numbers ?

You've inadvertently answered your own question. Do you see the words "FAA Approved" ...anywhere in or on your 170 IPC?

(It is not an approved document. It's a catalog... for ordering parts from approved sources.)

Also, (risk of repetition in this regard is a good thing).... the IPC is Unreliable as a reference for assembly. There are numerous errors in the illustrations as far as assembling the parts go. (Fuel selector is one example. It will never shut off the fuel if assembled per the IPC, and it will likely also result in reduced fuel-flow. The elevator cable routing is another... If routed in accordance with the IPC, not only will they not likely be capable of being properly tensioned, .... that method will result in OPPOSITE ELEVATOR... OR REVERSED FLIGHT CONTROLS.

Use the IPC only for ordering parts. (And even then, you might end up owning a part for 17 years not knowing what it does or where it goes...and find out none of the 170's have it after-all.)

George, that wasn't my question. My question is with the lack of any other reference, what do you use to verify part applicability?

lowNslow wrote:George, that wasn't my question. My question is with the lack of any other reference, what do you use to verify part applicability?

Also, what is the approved source for assembling a Cessna 170 or a sub system?
The IPC isn't approved and has quite a few omissions and errors but what else is out there that is FAA Approved data for the 170?

None, other than the type document, just common aircraft sense, standard practices and lots of acceptable data. It's a case where the " system " developed after the airplane. Common practices, a sense of purpose and good judgement ruled the day when these airplane's first took-off. Then things slowly developed, more of you can't do that, do it this way. Then the system strove to improve itself with more regulations and that's how we have arrived at; you can't do anything unless someone with possibly little sense or idea as to how something works, now is calling the shots.
It's kind of like the path from Abe Lincoln to ah...somebody really bad and possibly fake. and yes the issue is the same up here.
Hopefully the pendulum will swing back the other way.

c170b53 wrote:None, other than the type document, just common aircraft sense, standard practices and lots of acceptable data. It's a case where the " system " developed after the airplane. Common practices, a sense of purpose and good judgement ruled the day when these airplane's first took-off. Then things slowly developed, more of you can't do that, do it this way. Then the system strove to improve itself with more regulations and that's how we have arrived at; you can't do anything unless someone with possibly little sense or idea as to how something works, now is calling the shots.
It's kind of like the path from Abe Lincoln to ah...somebody really bad and possibly fake. and yes the issue is the same up here.
Hopefully the pendulum will swing back the other way.

That was the point I was gently trying to make. If we had to rely only on FAA Approved data - no one could work on a 170 as there is no approved data for it. We use acceptable data within reason and good common sense practice.
Example is the 100 series repair manual. It's not for the 170 but common sense tells you that a lot of it is appropriate and acceptable.

Ben, your 172A wings; the basic structural assemblies are identical. The only reason the left wing has a different 'next higher assembly' number is because of the fuel vent system and electrical configurations. When you properly alter these systems to conform to a 170B wing, you have effectively changed the the assembly number to be a left 170B wing. You don't need any further data.

gahorn wrote:I don't have the responsibility or authority to approve parts...so I can admit I don't have an answer for that question. But I believe it's correct to say that the IPC is a catalog only.... for the purpose of ordering parts from Cessna or other suppliers. Whether it can be used to identify whether or not a particular item is interchangeable with others... is a horse of a different color (as the Wizard would say.)

I'm crossing this bridge now. D55 Baron left factory with long chord flaps. The most current IPC says long chord flaps can be replaced with short chord flaps, in pairs only (of course). IPC is not approved data and does not offer any performance change data.

Thanks guys for helping me chase this down the rabit hole of he said she said. I received my reply from Cessna today. That being said I'm putting them on.

Ben
Your logic is sound, the -1 is approved and was used on the 170B, and the -58 is an approved spare for both the 172 and the 170B. However, the 172 wasn’t originally built with the 0523005-58. The early 172 up through serial 29819 used the same 0523005 wing structure as the 170B. Nonetheless, using wings from 17228849 will be no issue as the original and replacement wing part numbers are shared with the 170B.

Thank you

Geoff Kelley
Customer Service Engineer
Propeller Hotline
Textron Aviation

Congratulations Ben. You have a definitive answer. And its a good one.

But in light of the discussion in this thread about sources of approved data, Mr Kelley's reference to approvals ("approved and was used on the 170B" and "approved spare") makes me wonder what his source of approval is. I'm not doubting it, especially in this case as it's pretty straightforward. I just would love to know what he consulted to determine what was approved, given the lack of published/public data. It would be nice if whatever he consulted were published/public.

Aryana wrote:Oh the joys of owning an aircraft that predates the FAA!

It's always informative to learn from all the debate. I'm glad I'm just an owner/operator and only have to make sure that my checks don't bounce and that I have done everything within my power to ensure that the aircraft is airworthy. The brunt of this falls on my IA which is probably why he gets quite a big chunk of cash each year.

It is quite a bit of liability every year sighing off aircraft for their annual inspection. In this case it is even harder not having any log books or history. I have been able to conclude that the air frame has aprox 1800 hrs on it. But beyond that I have to disassemble everything to inspect. Searching for potential damage and previous repairs. Ultimately someone has to fly with my blessing and being a pilot as well as an IA I want to ensure I have done everything in my power to make this plane safe for flight. Fortunitly the airplane is mine and I am a perfectionist and purist. This will deffinitly be an amazing plane when I am done.

Check the control cables very carefully.
Mine only has 1400 hours and the rudder cables under the last pulley felt like a porcupine. To fully inspect the cables under every pulley is so much work, I'm just replacing them all with new.

[quote="bagarre"]Check the control cables very carefully.
Mine only has 1400 hours and the rudder cables under the last pulley felt like a porcupine. To fully inspect the cables under every pulley is so much work, I'm just replacing them all with new.[/quote

thank yo for the heads up on that.
We are replacing all of the cables wit new. When the plane had its wings removed prior to my ownership they cut all the wing cables. and the rudder cables were rusty So I am replacing those as well as the steering cables