Mobil 254 Vs. Aeroshell 555

[Bell-powered]

I would like to know the advantages and disadvantages of the mobil 254 and aeroshell 555.

Since the Bell conditional inspection for the 206 states that if you use DOD-L-87534 oil in tranny and tr tranny and using the newer tq gauge you have a visual inspection on over tourque up to 130% rather than 120%

 

So what is the reasoning why so many operators are using the mobil 254?

Any input is greatly appreciated.

 

Be safe

[sven]

Mobil 254 is a high thermal stability oil (HTS) which means it handles heat well without breaking down.

This makes it ideal for the turbine engine environment.

 

The Aeroshell 555 has good lubrication qualities by leaving a film on all the gears to dramatically reduce wear. That's why you can get increased inspections and TBO's on gearboxes.

 

So both good oils with different uses.

 

Hope that helps.

[Bell-powered]

Ah so the reason why lots of operators are using 254 in engine and gb and tr gb. because they work great it all 3, while aeroshell is not great in the turbine.. ok sounds good thanks

[whirlygig]

I think you may have misunderstood.

 

People use 254 because you can use it in all three, not because it is the best in all three. Ideally for the sake of the machine you would use an HTS oil (like 254) in the engine and then 555 in the gearbox's.

[Hazy]

The reason most 206s share common engine and xmsn oil is there exists the possibility of oil transfer and most often its xsmn to engine. So you wouldn't want 555 mixing with 254. The oil pressure in the freewheel is higher than the ambient engine gearbox pressure. That being said, some require 555 in the gearboxes and you don't have the choice.... I'm thinking L4s, is that right?

[carhartt]

You're right with the L4's. You'll also find requirements for 555 in 412 gearboxes.

[hungstart]

not all 412 g/b

[Coastal]

The reason most 206s share common engine and xmsn oil is there exists the possibility of oil transfer and most often its xsmn to engine. So you wouldn't want 555 mixing with 254. The oil pressure in the freewheel is higher than the ambient engine gearbox pressure. That being said, some require 555 in the gearboxes and you don't have the choice.... I'm thinking L4s, is that right?

 

Interesting, I was under the impression that oil generally transferred from engine to mgb via the freewheel in 206s. The common explanation is because engine oil pressure is always higher than transmission oil pressure (just ask the gauges). However, as you stated I've never heard that ambient engine gearbox pressure is higher than freewheel pressure, so that makes sense as well. I should know this, but where is the engine oil pressure sensor located and is freewheel oil pressure the same as mgb oil pressure? Anyone else care to chime in on this?

[DGP]

The old 206,s used a wet line for oil pressure from the engine and tx right to the gauges...they also used a wet line for fuel pressure right to the gauge....some where around the 300 mark they changed it all to pressure transducers that were located in a number of places...some in the engine bay...tx was on the tx deck...fuel was in two places...started in the side panel with the fuel shutoff valve....then they stuck it in the engine bay next to the starter gen which proved to be a BAD spot...transducers always seemed to go bad and they were very expensive....so if you have them...good luck and keep lots of cash on hand...the newer aircraft went back to wet lines to the dash instruments ....same as the 407....we just changed the engine gearbox freewheel seals...was transferring from the engine to the tx which had 560 oil mixing with 555 oil...this was on a 407 lots of fun

[helicopterjim]

The old 206,s used a wet line for oil pressure from the engine and tx right to the gauges...they also used a wet line for fuel pressure right to the gauge....

 

I remember passengers telling me there was fuel dripping on their heads in the back seat - the head liner had chafed through the wet line and it was leaking pretty good! I was working south of Coppermine and no engineer let alone any chance of getting parts. Cleaned it off - put some metalset on it and ordered parts. Flew it again a year later and I popped the headliner down - the metalset was still there!