Why change oil in airplanes?

[Ted]

Just spent the first part of this week with the CEO of the company I work with who has a Cheyenne IIIA. Just spent the better part of $1mm redoing the engines. Gulp.....

Reality bite$$$$$

 

[Henning]

I allow myself to look at airplane porn once per week dreaming of Conquests, Cheyennes, Commanders, and King Airs etc. I really need you guys to quit bringing reality into these threads.

The Conquest is a Unicorn, it runs on crushed fairy juice getting 3000 miles per fairy, and it poops pixie dust out the pipes and $100 bills rain from the overhead as you fly, and since fairies are only $50 a dozen, you make $4700 an hour flying.

You really should get one.

 

[Henning]

Just spent the first part of this week with the CEO of the company I work with who has a Cheyenne IIIA. Just spent the better part of $1mm redoing the engines. Gulp.....

Yep, that's why some people will buy mid time engines instead.

 

[James_Dean]

Yep, that's why some people will buy mid time engines instead.

They're putting on 400 - 500 hours per year and the owner is the kind of guy who likes to do it "right". Not saying that is always the most economical. I discussed it with him and he also said the used -61 aren't cheap because they're used in blackhawk conversions and are in demand. No idea how correct that is.

 

[Henning]

They're putting on 400 - 500 hours per year and the owner is the kind of guy who likes to do it "right". Not saying that is always the most economical. I discussed it with him and he also said the used -61 aren't cheap because they're used in blackhawk conversions and are in demand. No idea how correct that is.

I do not question his decission not to cheap out, just sayin that's how some people get by. If it's a popular engine it probably doesn't work out. It's when you use an engine that many people upgrade from where you get really good deals.

 

[James_Dean]

The Conquest is a Unicorn, it runs on crushed fairy juice getting 3000 miles per fairy, and it poops pixie dust out the pipes and $100 bills rain from the overhead as you fly, and since fairies are only $50 a dozen, you make $4700 an hour flying.

You really should get one.

Everyone knows that about the 425.... but what about the 441?

 

[stratobee]

The "Century" engine is a TPE-331 that is either the -1 or -2. These are old engines that were primarily used in the '60's. Garrett made several improvements after these which are essentially the engines used today.

The old Century series are getting harder to find components for, hence why operators have moved away from them. Basically the same with a PT6-6 or -20, they are out there but not well supported.

The Twin Commanders in question are the old 680W, 680V and 680T, which are essentially 680FLP's that had the Garrett's hung on them. The line didn't see any improvements until the 690's came along with improved engines and considerably beefed up airframe.

Correct. The 680 series and the 681 were the last ones made before the 690 series. They share very little structurally in common with the 690's. They have wings that are shorter. Smaller props. Narrower stance. Different speeds. The Century conversion got rid of the horrible Skydrol and hydraulic pressurization and replaced it with bleed air, but not all of them had the conversion done. Most of the ones with the -43BL engines (2000hr TBO, no HSI) have gone by the wayside (those are normally the ones you see at A&P schools).

The 680 series does not have the recurring spar inspection, nor does it have the aft pressure bulkhead AD, or the mandatory gear overhauls of the 690 (even though the gear is identical). That's where the big savings take place compared to a 690. It's also doesn't have the expensive heated windscreens of the 690. It has lower MTOW (9400lbs). It's not as fast, it can't fly as high.

There are still quite a few 681's flying as most of them came with the Century engines. Many Commander people consider the 681 to be the best compromise between utility and cost for a private owner. You get almost 690 speeds, but for much less cost.

Here are some pics of the 680V model. The first two photos are from one flying in Russia, the last one is of mine getting refuelled before delivery to mechanics. The 680/681's can be hard to differentiate from 690's, but as you can see in first photo, the wing attachment to the fuselage is at an angle and with some dihedral. The 690's have a straight extension that attaches to the fuselage and extends the wingspan. Their props are also much bigger and sit further out.

 

[EminiTrader]

I change my own oil in the Cirrus as its WAY cheaper. And not too hard to do. I do mine every 25 hours. Filter, 7 quarts oil, and Camguard - costs about $100.

Mine burns about 1 quart after 15 hours - has about 1600 HOBBS

 

[Ted]

Interesting that the 680s have props that turn the right way, unlike the 690s that have reverse rotation.

What are speeds and fuel burn? In the 690 we did FL260-270, 270 ktas @ 500 pph combined.

 

[stratobee]

Interesting that the 680s have props that turn the right way, unlike the 690s that have reverse rotation.

What are speeds and fuel burn? In the 690 we did FL260-270, 270 ktas @ 500 pph combined.

This is about 245-255kts on same fuel burn. Up high it drops to 400pph. Long range at ceiling (FL250) is 360pph, but it kind of runs out of wing around FL220-230. The 690's with the bigger wing do a lot better up there.

Never noticed the props turned the other way on the 690's.

 

[petrolero]

Bad title.

Piston engine in aircraft seem to burn oil at a faster rate than those in cars. By the time you need to change the oil (50hrs? Just a guess), wouldn't you have burned and replenished enough so that none of the original oil would exist?

I do not own an airplane.

I have a friend who owns a C172 that is 1000 past TBO. It burns oil at a moderate rate but compressions are still OK. He has the same thought... why "change" the oil when it is continuously changing anyway. Change filters every so often and call it good I guess.

He's just waiting for the compressions to get low enough and then he's going to do the 180 HP conversion.

 

[Ted]

This is about 245-255kts on same fuel burn. Up high it drops to 400pph. Long range at ceiling (FL250) is 360pph, but it kind of runs out of wing around FL220-230. The 690's with the bigger wing do a lot better up there.

So I'm guessing that mid 200s on speed is in the FL210-230 range? Interesting, thanks for the innfo.

 

[Henning]

So I'm guessing that mid 200s on speed is in the FL210-230 range? Interesting, thanks for the innfo.

You could add one to the nose of your 310.

 

[MBDiagMan]

Bad title.

Piston engine in aircraft seem to burn oil at a faster rate than those in cars. By the time you need to change the oil (50hrs? Just a guess), wouldn't you have burned and replenished enough so that none of the original oil would exist?

I do not own an airplane.

If an engine is worn enough for that kind of blow by, the oil is being contaminated so fast, that you need to take the OPPOSITE approach. Change it more often. The contaminants cause LOTS of problems. That much blow by is building acids in the crankcase at light speed.

 

[Ted]

You could add one to the nose of your 310.

Yeah, do like that turboprop Aerostar conversion. Of course in a non-pressurized plane that would be as useless as the TP Bonanzas, and I don't fly singles.

Of course, that would also be a bad deal in general since right now I'm mid 20s GPH for 190+ KTAS, and that would bring me to 30-40 GPH for not much faster. Would need to have something smaller and more efficient than than RR250s to make it workable in the altitudes I need to fly at.

 

[Henning]

Yeah, do like that turboprop Aerostar conversion. Of course in a non-pressurized plane that would be as useless as the TP Bonanzas, and I don't fly singles.

Of course, that would also be a bad deal in general since right now I'm mid 20s GPH for 190+ KTAS, and that would bring me to 30-40 GPH for not much faster. Would need to have something smaller and more efficient than than RR250s to make it workable in the altitudes I need to fly at.

Triple engine...

 

[Ted]

Triple engine...

New checklist:

Positive rate, gear up, declare fuel emergency.