Not in the parts manual but...

NealRomeoGolf

NealRomeoGolf

En-Route
PoA Supporter
Joined
Apr 12, 2016
Messages
4,958
Location
Illinois
Display Name
Display name:
NRG
I guess I'm learning the lesson that the parts manual is only a guide, not the final answer.

I have a Piper PA32R-300. Mechanic discovered that my pressure cutoff switch for the landing gear isn't stopping until 2000 psi. It is designed to shut off at 1800 psi. I've been having all sorts of things breaking/cracking on the gear and we assume this is why.

But wait, there's more. If you go to the parts manual, it calls for switch 587-847, which is what my plane has. But if you go into the maintenance manual, you'll see there are two different pumps spec'd to PA32s. Mine is the HYC-5005 and it calls for a different switch, 487-937. It calls for a switch that wants the cut off to be 1400 psi.

I think it's interesting that the parts manual doesn't put an asterisk in there about which pump is spec'd. You have to refer to the maintenance manual to know the right one. I've learned something new today.

And yes, that new switch is over $2000. Life is pain. Anyone who says otherwise is selling something.
 
NealRomeoGolf said:
you'll see there are two different pumps spec'd to PA32s.
Click to expand...
NealRomeoGolf said:
I think it's interesting that the parts manual doesn't put an asterisk in there about which pump is spec'd.
Click to expand...
Was there an aircraft serial number difference between the pumps? Regardless, parts manuals are revised over time and using a later version for older aircraft can lead to issues similar to this. OEMs do not revise manuals backwards only forwards. So if using newer manuals its best to double check the "big picture" before simply ordering a part. If possible find an older manual that was current when your aircraft was produced. As to using the mx manual over the parts manual for parts use caution. While it appeared to work for you here it can send you down a slippery slope in general.
NealRomeoGolf said:
And yes, that new switch is over $2000.
Click to expand...
There should be a vendor part number for the switch. Trying looking for that number vs the Piper number as it can be cheaper to procure.
 
Bell206 said:
Was there an aircraft serial number difference between the pumps? Regardless, parts manuals are revised over time and using a later version for older aircraft can lead to issues similar to this. OEMs do not revise manuals backwards only forwards. So if using newer manuals its best to double check the "big picture" before simply ordering a part. If possible find an older manual that was current when your aircraft was produced. As to using the mx manual over the parts manual for parts use caution. While it appeared to work for you here it can send you down a slippery slope in general.

There should be a vendor part number for the switch. Trying looking for that number vs the Piper number as it can be cheaper to procure.
Click to expand...
I use a parts manual from 1980 for my 1977. I can try finding a 1978 or something.

The maintenance manual revision I found online is from 1987. Here is the page for the pumps.

upload_2023-4-29_11-58-30.png

The shop sent me a picture of the manual they use and it actually shows 3 pumps. Looks like their revision date is 2006 so the one I found is older.
 
Since I'm going down this rabbit hole, it is puzzling to me that then in the PA32R-301 manuals later on they are ok with an 1800 psi switch on the HYC5005. My pump was replaced in 2009 with an overhauled unit, if that matters.

upload_2023-4-29_12-19-44.png
 
NealRomeoGolf said:
it is puzzling to me that then in the PA32R-301 manuals later on they are ok with an 1800 psi switch on the HYC5005.
Click to expand...
Keep in mind per your original problem was the 1800 psi switch failed high which more than likely caused your issues and not the 1800 psi rating. As to the use of the 1800 psi switch in later manuals could simply be normal upgrades the OEM goes through. What does the equivalent parts book show for a switch part number for your S/N? For example, in new Cessna manuals most AN hardware has been replaced with NAS hardware. Does that make the AN hardware invalid? No. The reason is they retired the AN specification and now vendors only make NAS hardware. Same goes for hydraulic pressure switches etc. This is why its important to understand where your specific aircraft sits in the food chain when dealing with parts references and parts. The parts books give you the S/N effectivity if applicable. However if you're ever in doubt give the OEM tech support a call which is what I do if I can not connect the dots in the parts books.
 
Bell206 said:
Keep in mind per your original problem was the 1800 psi switch failed high which more than likely caused your issues and not the 1800 psi rating. As to the use of the 1800 psi switch in later manuals could simply be normal upgrades the OEM goes through. What does the equivalent parts book show for a switch part number for your S/N? For example, in new Cessna manuals most AN hardware has been replaced with NAS hardware. Does that make the AN hardware invalid? No. The reason is they retired the AN specification and now vendors only make NAS hardware. Same goes for hydraulic pressure switches etc. This is why its important to understand where your specific aircraft sits in the food chain when dealing with parts references and parts. The parts books give you the S/N effectivity if applicable. However if you're ever in doubt give the OEM tech support a call which is what I do if I can not connect the dots in the parts books.
Click to expand...
Understood that it is the switch failing and not the wrong switch that is causing my issues. I'd rather replace it with the 1800 psi one which the aircraft has been operating from what it seems birth. We don't see it ever replaced in the logs. I really think it came with that 1800 switch from the factory. The 1800 psi one is $600 cheaper. I would just need to convince the shop that it's ok.
 
NealRomeoGolf said:
I would just need to convince the shop that it's ok.
Click to expand...
Give Piper a call then. Maybe there's a SB/SL that upgrades the switch? At a minimum get an email from tech support showing that P/N switch good for your S/N aircraft. The shop should accept that.
 
I had to chuckle when I saw this in the pump service letter. See last sentence. So that says parts catalog trumps service manual? :cool: I can't find any service bulletins for the hydraulic pump/switch.

upload_2023-4-29_13-11-47.png
 
And found a service manual with just one pump and the 1400 switch. The page said it was revised in 1978, about 8 months after mine was manufactured.

upload_2023-4-29_13-23-18.png
 
Turns out you can adjust these switches back into tolerance. Shop got it back to 1800psi and is fine with using the switch instead of a 1400.
 
NealRomeoGolf said:
Life is pain. Anyone who says otherwise is selling something.
Click to expand...

Got an unused bottle of the good stuff from breaking my foot if you need something to take the edge off. I wanted the painful reminder of my stupidity. A glutton for punishment...or just a high pain tolerance.
 
If the parts manuals are approved data (ie blessed by the FAA) you must use the current revision. You can ot pick and choose based on your needs as the manufacturer will have made updates that you need to adhere to.

If you are using an original manual from the 70s when the factory has released multiple changes you need to update to the changef/revised pages.
 
pfarber said:
If the parts manuals are approved data (ie blessed by the FAA) you must use the current revision.
Click to expand...
FYI: parts manuals are not approved data nor are most maintenance manuals unless there is an ALS which is the only section approved. Both are considered acceptable data.
pfarber said:
You can ot pick and choose based on your needs as the manufacturer will have made updates that you need to adhere to.
Click to expand...
Not quite. You do not need to follow any OEM maintenance/inspection update unless it is attached to a rule like an AD or FAR. So long as the manuals you use were current at the time the aircraft was produced or a program was adopted its legal to use. Plenty of guidance on this. Perhaps if you wish to continue to offer mx "advice" you might want to at least read the applicable FAA maintenance guidance first.;)
 
You must log in or register to reply here.
Back
Top