Green Arc and Red Lines

[Tom_Kitty]

Hi guys

I would like to get a couple of opinions. Problem beeing that as a pilot sometimes we get different answers for the same question.

Here is the question:
Oil pressure gauge has red lines at 100 (top end) and 80 (lower end) and a green arc from 100 to 90.
Is it advisable to keep flying that aeroplane with a oil pressure gage that constantly indicates 85? It is outside the green arc and above the lower red line ....

:confused::confused:

[Piper19]

Don't know what type you're talking about, but if it's a Cessna, Piper,... the aircraft manual should state the limits where your oil press should be in. Our checklists say "oil press in the green", so anywhere out of that is a no go for me. I should say anywhere out of the green and your engine is not healthy, anywhere near the red bands and your engine is about to quit.

Also consider the RPM you have. On low RPM's or idle, the oil press can be out of the green but above the minimum red line, which is normal. It will rise when applying more power e.g. during the mag check before takeoff.

[NutLoose]

Tom can you give us an aircraft or engine type please.

[Fark'n'ell]

Look at the numbers.80 psi seems rather high,most Lycoming/Continental engines are usually about 60/90 psi.Getyour oil pressure gauge checked/calibrated

[Tom_Kitty]

Hi again

Sorry NutLoose you are probably right. It is a PT6-28 on a Beech E-90.

Also got my facts a bit twisted. Redlines at 100 and 60. Green arc from 100 to 80. And we are constantly indicating about 60/65 to 80. As I said still within red lines but outside of green arc.

After a couple of talks with our AMO I also found out what the problem is. The wires coming out of the pressure sensor are too close to a strut of the engine mounting. After a repair and a couple of hours flying, the vibration breaks the strands inside the wire and we get a dodgy indication in the cockpit. Once the plug and wires get fixed/replaced we are good again for a couple of hours.

The matter is just extremely frustating...:ugh:

Any ideas or quick fixes :hmm: I could relay to our engineers ....?

[Engineer_aus]

Goope around the wires where the virbration is. Just use some PR1422 or in a heat environment use the Red stuff.

[Short_Circuit]

You could try stiffening the loom with a shrink sleeve over its entire length (between clamps if any) and goop wiring at the exit point of the sensor to stop vibrating there. Or simply tie or tape the loom against a stiffener, like a long zip-tie or plastic filler rod. (then there is always fencing wire, but I did not say that :oh:)

[Tom_Kitty]

Hahahaha, like the wire bit :ok:

Apparently there is a Beech approved mod of some sorts. Stiffening the loom as it exits the plug would be difficult, as the space between the plug and the engine truss is less than 5 mm. As the wire exits, it immediately bends through 90 degrees. I could only imagine rotating the pressure sensor a couple dgrees. As it is not centraly mounted this should give it some more space. On the other hand I don't know if that is possible at all.

Does anybody know if we could post pictures here? You know the thing about a thousand words ... :confused:

[Capot]

Well, Aquamon, that was a useful contribution. Well done.

I hope I never have to work with, for or near you.

Which bit of Once the plug and wires get fixed/replaced we are good again for a couple of hours. did you not quite understand? It's rep-et-it-ive fault which his maint-en-ance team are not man-ag-ing to fix, and he's getting fed up with it and them, especially if you are right and they are just fobbing him off with rubbish as they fail again to fix it properly.

[aquamon]

Well, if he's fed up with it, go to the Accountable Manager or QA.
Or maybe he's afraid.:zzz:

He doesn't even know the oil system on the airplane he saze he's flying.
I'm sure you don't, also.

Is the oil indication electrical on the pt6-28, lmfao!

Try replacing the "pressure sensor" with a transducer.:confused:

Verify problem is only indication using a dead-weight tester.

Replace vernatherm (oil cooler).

I can go on and on and on, but it's pointless as I'm here and the airplane is anywhere else with engineers that passed the same exams I did last century.

Bring me the airplane and I'll have it fixed within one hr.
Now eat your words caprat

[Tom_Kitty]

Hello aquamon

I think you are mising the point entirely. :* We (me and the fellow pilots) have an excellent relationship with our AMO. The facts I have stated here I got from our engineers. At no stage have I tried to tell them how to do their job, or questioned their abilities. I have merely related the information I gathered from them. In the meantime they are just as perplexed and are trying (nearly) daily to find a solution. They are aware of my postings here, by the way ....

I further resent your comment, that I dont know the systems. I have in excess of 1000 hrs on king airs and proud myself (thanks to our engineers) on my knowledge of the aircraft.

I think I have gathered the information I wanted using this forum. This will be my last post here.

I thank all who had helpfull and amusing comments. My eternal respect to engineers who manage to keep aircraft flying, sometimes under harrowing circumstances.:ok:

[Short_Circuit]

aquamon

I hope you never need help with an intermittent ARINC strap or hemi toroidal phase discriminator or what ever!
SC

[V1... Ooops]

...It is a PT6-28 on a Beech E-90.

Also got my facts a bit twisted. Redlines at 100 and 60. Green arc from 100 to 80. And we are constantly indicating about 60/65 to 80. As I said still within red lines but outside of green arc.


I am not familiar with the PT6A-28, but I am very familiar with the -27 variant, and I think there is very little difference between the two.

The PT6A-27 has a green arc on the oil pressure gauge from 80 to 100, and an amber arc from 40 to 80. When the engine was first released to market in the late 1960s, it only had the green arc. This meant that if the oil pressure remained below the green arc during operation, the engine had to be serviced.

After some investigation, Pratt & Whitney Canada added the amber arc from 40 to 80 in the mid 1970s, along with the notation in the maintenance manual that oil pressures between 40 and 80 were acceptable at idle, as long as oil pressure increased to above 80 (in other words, back into the green) when Ng was increased above 72%. The purpose of the amber arc was to make allowance for older engines that couldn't quite 'get it up' during idle, but did have satisfactory oil pressure during flight.

If you take a look in the most recent edition of the PWC MM for the small PT6 family, you will see a note appended to the engine limitations table that provides more or less the same information (but without the history lesson).

If your airframe oil pressure gauge only has a green arc on it and does not have an amber arc, it is possible that you might have a very early production oil pressure gauge installed. Perhaps check the IPC for your airframe and see if that indicator has been superseded by an indicator with a revised face on it that provides an amber arc.

Hope this information is useful to you.