MT Propeller

[Louis]

This morning, it was Halloween day.  Neil came for a walk in the mountain next to my house.  It was raining.  Somewhere not so far on our small planet, the world leaders of the G20 were meeting.  Well, without China president, and without Mexico and Russia. A remarkable absence for a meeting that is supposed to be global to be able to « save » the planet.  So on that important day, Neil and I decided to talk about…. MT propeller and frequency of oil change. 

He is a strong believer in longer prop for STOL operation.  And a strong believer in those wide and long blades with a considerable twist of the MT.  Longevity is something else, since some have issues with the MT.  But performance is there.  For a better  engine longevity with a MT, he is not sure.  He thinks that the engine must deliver the same HP in cruse to obtain the same speed.    We fly two Pilatus.  One with thin blades, the other one with large and thick blades.  On these PT6 engines, there is a torque meter sensor somewhere in the turbine.  A real sensor giving the true torque developed by the engine.  Not a calculated one, but a sensor that measures it.  On both planes, the one with the flimsy prop, and the one with the beefed-up prop, we have exact same torque to obtain the same speed.  Suggesting that on cruise, efficacy of the prop have a marginal effect.  But, one plane is less streamlined than the other, since the wing is a little longer and some external fuel tank hanging out the wing.  So the verdict might be wrong too.  Now the Pilatus are equipped with four blades, but it is mainly for sound regulation in Germany.  The three blades is still used for float operation.  We never did a balance test attached to a telephone pole to check on static thrust, like we did for a 250, a 295, a 800, and a 185.  We fear the telephone pole would come off the ground with the Pilatus    ;-)


Doug, you stated you are using a multi-viscosity fully synthetic oil.  We don’t have any experience with that oil.  So you might be right that your oil is good to 40 hours.  We use Shell W100 PLUS.  And change it at 20 or below hours.  Those first 20 hours only need one quart to add between 15 and 20.  When we were operating over 20 hours, it needed an extra quart more and more often after 20 hours.  Maximum was around 28 hours before new oil, since my legs are usually 4 hours, and after 25 hours, i had to put two quarts to be able to finish the leg with 8.5 quarts remaining.  Anything over 10.5 quarts seems to go out the breathing tube.

A long time ago, we used the infamous Mobil AV1 fully synthetic oil.  Because of the winter.  But as we all know, it was the best oil….. with a catch of engine failure.  My friend went into the trees in his 172 XP with a loss of power with the Mobil Av1.  So i stopped using it even before Mobil send the notice to stop using it.

The neighbor use Phillips 66 in the Robinson helicopter, and Bell, with great success.  He says that he can do a longer time without putting a quart.  Up to now, he did not convince us to switch.

Tomorrow, we might talk about the future of the planet, or may be how VG could be chosen instead of slats if Otto C. Koppen would redesigned the Helio in 2021

[Doug Johnson]

Louis, maybe I didn't use a fully synthetic oil, maybe semisynthetic its been 20 years since I sold my Helio and haven't bought any thing but lots of Diesel engine oil or owned an a/c since other than a couple Kasperwing ultralights and they use 2-cycle oil, I've been using Amsoil in all my 2 cycles engines since it was introduced 30 years ago and it is fully synthetic, I even went out to the garage and looked at a bottle.

I'm sorta kinda thinking the aviation oil was Shell oil 15-50 maybe. I seem to remember that 'scallop shell' logo.

I think I would  remember using an oil that had to be withdrawn from the market.

I just googled all the Aviation oils I'm still not sure which oil I used.

[Kevin Dunn]

Doug,

Just to confirm, the logbooks say you were using Aeroshell 15W50.

Kevin

[Louis]

The Aeroshell 15w50 is approved for the Lycoming geared engine.  It already incorporates the additive that we find in the PLUS of other oil.  As stated by the manufacturer:

The anti-wear additive system in AeroShell Oil W 15W-50 provides outstanding wear protection for critical camshafts, lifters and other high wear metal to metal components.

As for the PLUS oil, the the Lycoming LW 16702 antiwear additive has been incorporated into the formulation thus eliminating the need for supplemental additive addition

This additive was specified for some Lycoming engines that have a high compression ratio ( 9:1 ) or turbo or supercharger, or geared.

We do fly with the 15W50 in winter.  It is easier to fly when it is pretty cool.  The problem we have without it is that  we are not able to heat the oil cooler on run-up on the ground.  The engine don't come enough warm to open the bypass to send the oil trough the oil radiator.  Yes we do pre-heat before under an engine cover, but you have to remove the engine cover to start the engine.  As soon as you remove it, the oil cooler start to cool down.  By the time the engine becomes warm, around 220 F, the oil cooler is freezed   And the oil by-pass don't send any oil to the oil radiator.  Then you take-off, the engine go up to 350 F, it opens the by-pass to send the oil to the radiator, but the oil can't flow in it.  The oil in the radiator is molasse.  Strangely, at those quite cold temperature, you see your oil heating too much and going over the 240 F limit on a very short time on take-off.  Sometimes, the thermostat will open soon enough and you see your oil going down fast once it does start to flow trough the radiator.  This happens with all engines that have the oil radiator in the front.  With the Cub, we have the radiator in the back of the engine, so it does warm -up in taxiing and run-up.  So we don't have this problem.  The placement of the thermostat is also determining. 

This happens around minus 20 with regular oil.  Using the semi-synthetic 15w50 will prevent this behaviour down to minus 40. 

Strange that the more the temperature is cold, the more we have the problem of too hot oil on take-off. 

We tried to put air flow reducer, like some 172 winter kit.  It does work... half of the time.  The hole in the aluminum reducer let too much air going to some place on the radiator.  The best we found was foam.  A piece of cushion foam on the radiator.  On the 295, it does hold by itself.  We tried air filter foam, but the air was going too much trough it.  A cushion foam insulate the radiator for the time you are taxiing and run-up.  Once you take off, the radiator is not freeze up and ready to receive the warm oil.  At speed we are going, the air goes trough the foam and you don't see any too hot temperature.  But it does help to keep it warm ( from your preheat under the engine cover )  from start-up to take-off.  Strangely, the more time you take to warm up your engine and taxi, the more you have problem with the radiator becoming too cold.

The 250 is fitted with a nice camera closure on the radiator that is operated from the cockpit.  We are able to close it when we start the engine.  Keeping the oil radiator enough warm until the takeoff . 

I think here is always some flow to the radiator before the thermostat valve open, but it looks it isn't enough at those temperature. We should also try to pre-heat at higher temperature.  Not just 32F but let's say around 70.  Or may be preheat the radiator at high temperature like 100F.  But those radiator are made to cool fast.  This is their mission in life. 

Anyway, using 15w50, plus the foam or closing the camera shutter on the 250 works well.

[Doug Johnson]

I don't remember seeing one of these shutters 30 years ago



Louis, Thanks for all the info I'm sure it will be helpful to a lot of Helio people.

I put a bunch of electric preheat stuff on my Helio but never really used it much until low 50's F upper 40's F, and in serious below zero weather i fund a reason to stay home.

I never flew much in the winter except my ultralight on skis, and if I did need an airplane I usually flew my 180hp 172B to a plowed strip. I can only remember flying a couple times in -20 below F and that's because it was that cold at my destination.

I lived in Anchorage and we rarely saw it get below -30 in fact the coldest I saw it get in Anchorage was -55. Whenever I got sent to Fairbanks in the winter and not by choice it seemed to be at least 50 below the rest of my time in below zero weather was riding snowmachines and we seemed to draw the line around 10-15 below except when racing snow machines then you just took what you got.

Here is a link to a previous post about preheater stuff https://flyhelio.com/smf/index.php?topic=1518.msg7169#msg7169