Could you help me to understand some of Cessna AMM, please ?

[Cavalryman]

Hello to everyone !

As the maintenance organisations hates to replace costly HT's/LLP's I need to be confident when they will blame me for asking to replace, let's say, throttle+mixture control cables.

Cessna 152 AMM says about engine control cables:

Inspect each 100 hours for general conditions and freedom of movement. These controls are not repairable. Replace every 1500 hours or whenever maximum linear movement exceeds 0.050 inch.

So far I was thinking, that these cables shall be replaced each 1500 hours TIS in any case (assuming, that linear movement is always ok). But now I see, that there is no widely used (in 152 AMM also) magical "whichever occurs first" phrase at the end. The same thing about fuel tank inspection: "each 1000 hours, or to coincide with engine overhaul".

So.... can we wait until control cables will be inoperative (linear movement exceeded or just poor condition) and then replace it ? Can we perform fuel tank inspection only at engine overhaul ?

If inspector comes, can I point that "there is no <whichever occurs first>, so this note gives us an option to do this OR to do this" ? Overdue life limited part is finding 1, right ?

P.S. By the way, is carburetor heat cable also referred to engine c.c. ?

[SeldomFixit]

The word " whenever " is your absolute guide, in this case.
If linear movement exceeds the stated limit after 1.0 hours in service it MUST be replaced.

[NutLoose]

The reason the throttle cable is listed as that, is due to the fact you cannot slip the cable out of its outer to inspect it, (on the mixture and the carb heat you can remove the inner, and inspect the inner cable for wear, so there is no life except at engine change because they are visually inspectable for wear by removing the inner.) the reasoning behind the throttle life is if you are on say finals you pull the throttle shut, the cable snaps at idle and you need power again you are going to crash! hence the life imposed on it........ I think Mcfarlane ones have a longer life BTW

Recommended Service Life
Due to the criticalness of engine
controls and considering their
operating environment, the maximum
recommended in service time for
McFarlane engine controls is equal to
the maximum time between engine
overhauls as recommended by the

engine manufacturer.

see page 7
http://www.mcfarlane-aviation.com/pd...g2010-2011.pdf


So the life IS 1500 hrs, but if you find signs of wear by doing the linear check the life of them is less.

Fuel tank one I tend to do on the annual when I do the guaging check and have the tanks empty. I also check the straps as they can break.

Hope that helps?

carb heat is an engine control as it needs a duplicate when replacing.

[Cavalryman]

SeldomFixit,
That is clear. But I am asking about flying, for example, 10 000 hours without control cables change, assuming that their condition is fine.

NutLoose,
Thank you very much, unfortunately I am not able to visit MRO, so it is very nice to find out what is happening in real life, not in IPC

In summary (in case of C152) we have the following: Carburetor heat cable, Mixture cable and Throttle cable MUST be replaced each 1500 hours TIS, regardless of their linear movement, regardless of when the engine was overhauled, regardless of which moon is now.

Fuel tank one I tend to do on the annual when I do the guaging check and have the tanks empty.

Guaging test is SEB 99-18, right ?

Thanks for the link to cable manufacturer. I will advise to use it for MRO.

[Rigga]

The AMM cannot make it any clearer - the legal phrase in use is:

"Replace every 1500 hours or whenever maximum linear movement exceeds 0.050 inch."

The word "or" gives precedence to the first parameter with a backstop of the second parameter.

You don't have any other choices except to ignore the AMM and lose any insurance cover you have (or maybe you dont have...)

Hope this helps

[Cavalryman]

Thanks, Rigga.
At least I know for sure now about replacement time.

You don't have any other choices except to ignore the AMM and lose any insurance cover you have

They have insurance, I guess.

By the way, I got work report on one AC recently, where MRO replied something like: "ok, your cables are overdue. We ordered new ones. Placed as <Hold item>. Will be replaced on next maintenance."
But CRS was signed... What happened in this case ? Aircraft is flying with LLP overdue and nobody cares ? What CAA would say in case of inspection ?

I already know how important is to handle properly with AD's. But what about components? Theoretically, aircraft should be grounded in case of life limited component overdue (as it is with AD's), but experienced MRO signs the CRS.

P.S. may be I didnt say it before, but airplanes are used commercially (flight school).

[Capot]

Read the words, forget about unstated "other meanings".

Rigga is right as ever, the sentence is crystal clear. Replace at 1500 hours, unless you find (in one of the 100 hour inspections) that it exceeds the stated tolerance, in which case it must be replaced immediately.

To put it another way, without a replacement cable the aircraft is unserviceable if (a) the cable has more than 1500 hours or (b) on the last 100 hour inspection it was found to exceed the allowed tolerance.

There is no leeway on the 100 hour inspection either, as I understand it. Hmmm, I wonder how many aircraft fly with that one overdue? Can Rigga comment?

[Cavalryman]

Capot,

Hmmm, I wonder how many aircraft fly with that one overdue?

There is a whole swarm of these planes with TT over 5000-8000 hours with control cables never changed.

[Malcom]

What happened to only ADs and Airworthiness Limitations being legally enforcible, while you decide what you want to do with any manufacturers requirements in your maintenance program ?

Same saga with Cessna seat belts has been done to death umpteen times!

[Rigga]

Dependant on the NAA/State of Registration - the cables MAY be extended by 10% if necessary.

But that is not a hard and fast rule - I don't know if these cables are subject to AD actions.

Malcolm,
Forgive my "Black-and-White" attitude, I'm from the big jet world.
AD's are legally binding and all the other stuff is at least recommended and, at most, highly recommended by the OEM/manfacturer. (try telling Airbus that!) Only NAAs can make maintenance actions, Lives and Inspections "mandatory".

However, if, during an post accident investigation, a fault is found to be caused by a component that has overrun its recomended life or has not had some recommended maintenance, then I'm pretty sure the insurance is unlikely to pay up?

That doesn't mean its all mandatory but, in good-ole' hindsight, one might be considered quite foolish for not doing the recommended jobs.

Think of all those Aussie farm accidents...

[NutLoose]

By the way, I got work report on one AC recently, where MRO replied something like: "ok, your cables are overdue. We ordered new ones. Placed as <Hold item>. Will be replaced on next maintenance."
But CRS was signed... What happened in this case ? Aircraft is flying with LLP overdue and nobody cares ? What CAA would say in case of inspection ?

Cannot be done, the 1500 hr max is what is stated in the manual and in EASA/CAA land you have to comply with the manuals limits, you might be able to apply for a dispensation to fly past it from your CAA, say if spares were unavailable as we did on an engine, but that would be between the maintainance company and your CAA....... but as said other countries may vary...... in CAA land Pre EASA all the other limits such as seatbelts used to be on condition as they were checked in company, which is the sensible route, HOWEVER they still then insisted on the 1500 hr rule for the throttle cable.

I replied earlier but the server was busy so I lost the answer I was doing,

The mixture and Carb heat DO NOT have the 1500 hr limit as they can be inspected internally........

The only thing I can think of on the c152 that can exceed the limits is the engine hoses, they can continue in service provided they are deemed servicable, and replacements are immediately ordered and fitted within a set time period.

Trouble with Cessna is they never update the manuals, the brake hoses 5 year replacement in the book is wrong, there was a service letter in 1985 i think, stating if Teflon hoses were fitted the hose part of the inspection went onto condition............ they were supposed to by the letter be incorporated into the manual shortly, alas 26 years later we are still awaiting it being incorporated!!! In fact check out the aileron balancing.............. it is for the wrong type of ailerons!!!! and is wrong.

[Cavalryman]

NutLoose,

Thank you so much about those brake hoses! Just went through Cesview Service Info and find SB you mentioned.
SNL 85-54

The mixture and Carb heat DO NOT have the 1500 hr limit as they can be inspected internally

I will try to find some document on this. May be some SB is saying something about it... This will be like a provement.

Thank you again.

[Malcom]

I dont say ignore any manufacturers recommendations - but at least review them and incorporate them ( or an practical alternative ) in your own maintenance programme - such as the internal inspection mentioned which I dont remember being a Cessna specified one, but presumably a locally devised alternative?

[NutLoose]

Well there you go, just rechecked the manual and you are right, the MIXTURE and CARB HEAT are included in the 1500 hr inspection, It was a surveyor told me the throttle was the only one because it couldn't be stripped and I have been working to that idea, stripping the other two down when changing the throttle one...... Luckily I had a look at the hours this morning and the closest to requiring it is still a good 215 hours away. So thank you

[Cavalryman]

Ouch... I just created one WO with throttle cable mentioned only.

Oh my... poor aviation. She is suffering from guys like me. But from the other hand, I am the first person who read the AMM in my organisation.

[NutLoose]

Still you can tell them once the teflon brake hoses are fitted you do not need to replace them anymore unless they are damaged.

Odd thing though on the engine ones, the Teflon I think extends the life to 10 years from 5 years, but on a lot of other aircraft makes they go onto being condition if teflon..... even the Spitfire next door has engine hoses being teflon are on condition!

[Cavalryman]

I have heard about 10 years for Teflon hoses too.

But for engine hoses we are assuming the following so far: if engine (let's say Lycoming O-235-xxx) was overhauled at least once, then it doesn't have "Cessna installed hoses" any more. During the overhaul, engine hoses to be changed in accordance with Mandatory Replacement Parts SIL or Engine Overhaul Manual or something like this.
By the way, Cessna AMM asks to follow Lycoming/TCM manuals about their hoses.

In this case, engine should come with new hoses after the overhaul... is it really so ? If no, then how the hell "Lycoming installed hoses" can appear ?

[hawker man]

When your Engine comes back from overhaul all Mod's,SB's and component changes should be listed on the Form 1 and in the Engine log book.

[NutLoose]

I have actually been researching this today as I have some due,

Ok Cessna hoses I would count as ones in the Cessna Manual under the aircraft and with a Cessna Part number or alternate, I have never had an O-235 back from overhaul with any hoses fitted as Lycoming do not supply them with them, and I have had a lot of Lycoming supplied engines.

This is where it all gets a bit Cessnaesque and totally unhelpful.

The Cessna 152 manual states (1978 through 1985) ( ITEM 2)



However the Cessna 100 series manual (1963-1963 )amended 2003 gives








Now although the 152 one only refers to rubber hoses, the latter for the earlier version of the aircraft under the 100 series refers specifically to the Teflon as well, So to be on the safe side I use the latter more stricter limits as the Cessna 152 stand alone manual does not mention Teflon hoses. You could read it as the 152 manual only gives a life on rubber hoses, therefore the Teflon ones are on condition...

So Cessna give you two different standards......... how unusual.