Warbird Information Exchange

I am interested to know if anyone has had any failures with the Gorila oil filters part #HD6A from air wolf. I installed one 3 years on my Yak 9 which has a Allison 1710 and have had no problems until the other day when I started the plane it pushed the O ring out of the filter? .This is the 3rd filter on it since the install and I had 16 hours on this filter. Before the install I checked the flow rate of the filter to make sure it could handle the flow rate of the engine which it could . Also after the failure I check the savenage pressure for any blockage in the oil system and it checked out good 38psi cooled and 21 psi hot. The filter is used for R2000, R1830 ,R1820, R1340 & others. Anyone running one I would like to know.
Thanks
Eddie

I have had no issue with the Airwolf filters as used on the T-28 and other aircraft. The filter no. for the T-28 is a Fram HP-6A. Airwolf specifies using the Fram filter only.

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Expert:
Ex: Former.
Spurt: A drip under pressure.

I haven't had a problem but only have used it on a T-6/1340.
I have used the Fram HP-6A only and can't see how the seal would give if installed properly.
The seal on the Fram is more of a square seal with a large flat contact area.

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Rich Palmer

Remember an Injured Youth
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Yes your right the filter is a HP-6A . I purchased all the filters from air wolf . I cut the filter open to check the internal bypass and it was there .

What was the ambient temp when you started the engine?
Are you using 60 wt?
Cold thick oil on start up will be the hardest on the system.
The scavenge system normally won't spike much pressure but an oil regulator issue could have caused a spike in pressure.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

The temp was 50 F when I started and the same two days later when I started it cold to check the scavange pressure. I use aero shell 120W

50 on the oil temp or air temp? Is the hangar heated or oil tank have heating strips attached?
Do you have a pre-oiler?
Is there a chance that overnight temps were a bit colder and the A/C was cold soaked?
When we had A/C (P-51 and SNJ) in unheated hangars in the past we had strip heaters glued onto the oil tank and always had them plugged in if temps were below 60 F.
If you pre-oil and have a large amount of cold, thick oil to scavenge from the engine there is a chance that you had an extreme spike in pressure.
I've seen oil coolers burst before.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

On cold days on the test truck I have seen scavenge pressure go to 55/60 PSI at idle with an oil temp of 20 C. That pressure drops relatively quickly as the engine begins to warm. When the engine is up and running at operating temps, 70/75C oil temp the scavenge pressure is 5 PSI or less. In using an H model heat exchanger modified for a racing application by plugging the center by-pass tube and removing the vernatherm so all oil would go through the cooler core at all times, in the airplane the scavenge pressure applied to the inlet of the heat exchanger never went above 25 PSI at start up with a cold engine. There is no direct correlation between the main engine oil pressure value one reads on the main oil pressure gauge in the cockpit versus what scavenge pressure/output pressure to the oil cooler is.

The air temp was 55 F oil 50. I have a skinny dipper in the oil tank that tells me temp & qty. I flew the plane twice the day before and put it in the hanger over night. When testing the scaveage pressure at start up I saw 80 psi with in 10 to 15 seconds it was stable at 38 psi when the oil was 100 f pressure was 21psi. I did preoil the engine on each cold start . I have 2 oil coolers with no vernatherm. I could even move oil through the system by blow on the hose to the coolers . I talk to the engine builder he said he sees 40 psi cooled and 15 to 20 psi hot 75 c on his test truck .

Air Wolf claims 450psi busrt pressure on there filter . After looking at the filter closer the outer ridge on the base that holds the O ring was Not as tall as the inner .I think this was the problem ,I cut the filter open to look at the bypass and it was there and working.

It probably wasn't the bypass in the filter as your problem. Pressure built up in the filter because of some situation elsewhere.

If there was a problem upstream of the filter, oil cooler, regulator on oil cooler, and the oil was thick and couldn't move fast enough, it could build a spike in pressure because a large volume of cold oil couldn't move fast enough. This would be in the whole system from the feed line to the oil tank back to the oil outlet of the engine, including the oil cooler, reg, and the filter. The filter and it's seal seemed to be the weak point at that moment and let go.

Either you have a problem with something in the system being too restricted for the oil to flow freely at cold temps, the filter wasn't tight enough or there was a defective filter. If for some reason the oil regulator's bypass function failed or something is sitting in an oil line creating a blockage, the seal blowing might have saved some other component from failing such as the core of the oil cooler.

Are your oil lines metal tubes joined by Mil-6000 rubber hose and hose clamps, SS flex hose w/AN fittings or Med Pressure Rubber hose w/AN fittings?

Resolutions are-

Insp oil regulator on your oil cooler. It should have a bypass to allow cold oil flow to not go through the cooler core. This protects the more fragile core and allows the oil to move with less restriction when cold.

Insp oil lines to make sure no debris or object could be sitting in one restricting oil flow.

Use the Larger Airwolf filter bodies with 2 of the HP-6A filters as a part of the assy.

Use W100 (50 wt) in the colder months.

Keep the A/C in a heated hangar.

Install heated strips on the oil tank or use a heat source for a period of time directed into the cowling.

Check oil line dia matches what is normal for P-40, P-38 ect.

Ensure filter is tightened per instructions on the filter.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

Thanks Rich,
I will investigate all of those things , some I have done all ready . I use AN-16 hoses & fittings med pressure in the oil system.
Eddie

1" ID sounds small for that setup to me. -16 AN fittings are actually smaller than the orig metal line ID of 1" on the ID of some hose fittings. Sometimes a flap of rubber can be induced during the install of the fittings in the hose. Sometimes the flap rarely interferes and maybe only causes an issue once which causes some failure.
Mustang oil lines varies between 1 1/4" to 1 1/2". Spitfire is 1 1/4". These are all metal tubes with rubber hoses connecting them.
T-6 uses 1" metal oil lines on the 1340.
Good luck.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!