Post by Tim Glubaskas on Feb 20, 2017 11:22:49 GMT -9
We recently had a plane do a noser. Complete loss of hydraulic pressure. Never had that happen before in the 18 or so years I've been here running a bunch of PA31s.
Culprit - NLG 'Down' Line Sheared off.
We found that the NLG actuator had a 90 degree fitting and a 45 degree fitting installed. The plane was taken over by us in 2012 with no issues from the actuator, fittings, or lines since we began maintaining it. The plane was acquired from another operator a while back but the records transferred were very 'light,' to say the least, so we cant really ascertain how long the actuator has been in service. During routine gear swings it seems to function great and continued to work flawlessly throughout the years.
When we took the line involved out it was hard as a rock (-35 or colder in flight), and that, combined with a non-optimal angle for the fitting, most likely caused it to snap off. Chances are this would never be an issue where temperatures don't border on the insane, but one can never know.
Our 15 other planes all have a 45 and 45 installed. The only thing we can guess is that the original installer was worried about the hose possibly rubbing on the top of the wheel well so they changed it out. Another possibility is confusion caused since Piper does not call out the NLG fittings (though it shows 45s in a picture) and the Piper Part Number is the same for both MLG and NLG actuators. The MLG has the 90 degree fitting on it.
We contacted piper through the our FSDO and Keith Knowles in Atlanta - when they revise the Parts Manual the proper numbers will be included.
To make sure this doesn't happen again on our end we will be adding a line in our AAIP to ensure the fittings are verified during conformity. We are also looking at life limiting our hoses for the gear at 10 years to rid us of any substandard ones.
Because of the part number confusion we have also separated this part number into 2 bins, one for MLG and one for NLG.
Members of our community should take a quick peak at their NLG actuators to verify proper fitting placement - wouldn't hurt checking the MLG also since the PN confusion could result in a mechanic grabbing an item set up in correctly for the task at hand.
NLG Actuator - both 45s
Reference Figure 105, page 3C10
Another line with fittings unidentified on the same page.
FROM PIPER
"Tim, FYI
The two fittings common to the actuator are AN837-4D “45 degree elbow” fittings, 2 places.
Regarding the TEE fitting, it is part number AN824-4D.
I will speak to the manager of tech pubs about including these part numbers at the next revision to the parts catalog."
(Pet peeve....i know the CFR states you can toss certain records after a year but DON'T FREAKIN' DO IT....they could be useful when trying to determine whether a part needs a life limit, etc etc (and you look sketchy as freakin' hell doing it...) - - - rant over)
Have a good rest of winter and safe flying, all!
Tim
Culprit - NLG 'Down' Line Sheared off.
We found that the NLG actuator had a 90 degree fitting and a 45 degree fitting installed. The plane was taken over by us in 2012 with no issues from the actuator, fittings, or lines since we began maintaining it. The plane was acquired from another operator a while back but the records transferred were very 'light,' to say the least, so we cant really ascertain how long the actuator has been in service. During routine gear swings it seems to function great and continued to work flawlessly throughout the years.
When we took the line involved out it was hard as a rock (-35 or colder in flight), and that, combined with a non-optimal angle for the fitting, most likely caused it to snap off. Chances are this would never be an issue where temperatures don't border on the insane, but one can never know.
Our 15 other planes all have a 45 and 45 installed. The only thing we can guess is that the original installer was worried about the hose possibly rubbing on the top of the wheel well so they changed it out. Another possibility is confusion caused since Piper does not call out the NLG fittings (though it shows 45s in a picture) and the Piper Part Number is the same for both MLG and NLG actuators. The MLG has the 90 degree fitting on it.
We contacted piper through the our FSDO and Keith Knowles in Atlanta - when they revise the Parts Manual the proper numbers will be included.
To make sure this doesn't happen again on our end we will be adding a line in our AAIP to ensure the fittings are verified during conformity. We are also looking at life limiting our hoses for the gear at 10 years to rid us of any substandard ones.
Because of the part number confusion we have also separated this part number into 2 bins, one for MLG and one for NLG.
Members of our community should take a quick peak at their NLG actuators to verify proper fitting placement - wouldn't hurt checking the MLG also since the PN confusion could result in a mechanic grabbing an item set up in correctly for the task at hand.
NLG Actuator - both 45s
Reference Figure 105, page 3C10
Another line with fittings unidentified on the same page.
FROM PIPER
"Tim, FYI
The two fittings common to the actuator are AN837-4D “45 degree elbow” fittings, 2 places.
Regarding the TEE fitting, it is part number AN824-4D.
I will speak to the manager of tech pubs about including these part numbers at the next revision to the parts catalog."
(Pet peeve....i know the CFR states you can toss certain records after a year but DON'T FREAKIN' DO IT....they could be useful when trying to determine whether a part needs a life limit, etc etc (and you look sketchy as freakin' hell doing it...) - - - rant over)
Have a good rest of winter and safe flying, all!
Tim
