R-985 operation and leaning.

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C-FDPB
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R-985 operation and leaning.

#1 Post by C-FDPB » Mon Aug 21, 2017 6:51 pm

Been flying the beaver for over 1000 hours now and think I'm starting to learn the bird. I know she'll teach you something new just about every week. Just wondering what some of the old timers think in regards to engine operation with different power settings, leaning etc. I've seen the beaver flown with gradual power reduction to final trying to keep temperatures in check, and I've seen going from an abrupt cruise power to idle once on the intended lakes shoreline. Thoughts on what this will do to cylinders? Shock cooling risk? Cracked cylinders? Also wondering what your opinions are on leaning for .1 or .2 hops all flown below 2500 ASL. Any thoughts opinions and info welcomed.

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Cat Driver
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Re: R-985 operation and leaning.

#2 Post by Cat Driver » Mon Aug 21, 2017 7:10 pm

Leaning at low altitudes on short trips is at the discretion of the pilot.

Abrupt throttle movement, especially on power reduction on any radial engine is harmful to the engine because radial engines have counter weights and also it induces reverse loading on the bearings.

The larger the radial engine the more sensitive to throttle movements they are.

Personally I would not employ a throttle jockey on any airplane.

But that is just my opinion. :(
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Re: R-985 operation and leaning.

#3 Post by C-FDPB » Mon Aug 21, 2017 7:19 pm

This is kind of what i was thinking. Was just an observation of another aviator. Also cat driver. What sort of power settings did you use. I've heard of 28/18 in cruise and 29/19 .
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Re: R-985 operation and leaning.

#4 Post by valleyboy » Tue Aug 22, 2017 5:19 am

Many years since I was behind a junior. As Cat points out, abrupt throttle movements are a strict no no. Power settings we used were 28/1800 and 30/2000 for climb I have had americans sit beside me and as why power setting were so low. They used 30/2000 for cruise (that was in a bch18). A very old time bush pilot once said to me just about the time I was starting to shave "it's not how much power you use but how you apply it" -- good words if you stop and think about it. There was a pilot who used 42 inches on every T/O and pulled back to 36 on step. It was a survey beaver and engine went its time. We never went there.

My pet peeve(I live on a lake beside a float base) are the throttle jammers, makes me cringe every time I hear the prop trying to keep up with throttle application. The junior was likely the 2nd best radial ever built and very reliable (R2800 #1) Maintain temps and manage the power well and it will serve very for a long time

Leaning seems to be a relatively modern issue. I can never remember ever leaning an engine until I started flying a DC3 - thinking was that on floats the aircraft was way slower than on wheels and rich was for better cooling and short trips you never really got temps stabilized enough to consider leaning. In the summer the whoredyne was always on the red line or in excess of 205C and approaching 232C, especially with an external load. That was then, circa 1970 -- so yes time marches on and times change. Maybe we were wrong, maybe not :mrgreen:
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Re: R-985 operation and leaning.

#5 Post by Rowdy » Tue Aug 22, 2017 1:14 pm

I've got a couple thousand hours now behind and beside R985's and a slew of other piston engines...doesn't make me an expert however.. Just an observer.

I know exactly who you were flying with that was whacking the power to idle once they were at a lake shoreline. I remember the justification he gave me for it too and I still refused to do it. Needless to say, he goes through a lot of cylinders. But, when you're paying the bills, do whatever you want.

I'm sure you're aware that Radials and most piston engines like smooth applications and reductions in power. No big temps spikes or drops. Never drive the thing with the prop(more of a concern with the 1340)... Don't make the prop governor try and play catch up. Make sure you're in the green and warmed up properly before a takeoff (this was a big one, watched a couple rookies pop oil coolers and seals). These simple things will keep cylinders AND the person footing the overhaul bill happy. The quasi SOP we used on the coast was full rated takeoff, and as you broke water come back to 33/2200. Climb out after obstacles at 30/2000 and cruise at 28/1800, although occasionally a 'hot' cruise power of 29/19 in a couple of the machines that needed the extra :wink: I haven't spun a 985 in anger in just about a year now though...

Ohh and edited to add, we never leaned. Legs were too short to make a difference and on 87 it didn't much care for it.
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Re: R-985 operation and leaning.

#6 Post by bronson » Tue Nov 21, 2017 4:21 pm

You know...there's nothing wrong with the settings in the manual....
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Re: R-985 operation and leaning.

#7 Post by BC04 » Wed Nov 29, 2017 12:19 pm

You are probably starting to sense a bit of a theme here. Abrupt throttle adjustments are less than ideal on these engines, set yourself up early and slowly reduce power as you are coming in for approach and it will help you from shock cooling the engine and will also result in a more stabilized approach. The company I work for on the coast climbs out at 30/20 if there are no obstacles to clear and we cruise at 29/19, both seem to work well. When I was in Ontario we were cruising at 28/18, it was also a fine setting. In terms of leaning I will only lean at altitude (4000+) or if I am starting to feel a little light on fuel.
Just my experiences.
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Re: R-985 operation and leaning.

#8 Post by peterdillon » Thu Nov 30, 2017 10:01 pm

Lots of good advice above. We are at 700Ft and as soon as we are off the water and back to 28-18 we are starting to lean carefully. No two 985's are running the exact same overall mixture even when in full rich nor are all the cylinders of any given 958 running the same mixture with 1930 technology. If you don't need the extra fuel for cooling then setting up a safe mixture for the leanest cylinder will not hurt the engine and save a very noticeable amount of fuel. If I was hiring pilots to fly my planes short hops I would recommend full rich as the risk of over leaning isn't worth any fuel saved. Lots of people don't agree but I have done the same with lots of different float planes and never had a cylinder or valve problem but might just be lucky. We always were running fairly low percentage power though.
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Re: R-985 operation and leaning.

#9 Post by twistedoldwrench » Tue Dec 05, 2017 7:26 pm

Another point to consider is that the 985 carburator was originally set up to burn 80/87 fuel. Back in the early 80's ?? the OH shops started to put a bit bigger main jet in the carb to add a bit more fuel at take off for additional cooling, as the 100/130 burned somewhat hotter. This caused the fuel burn to be somewhat more than the 1945 manual called up. Just an interesting tid bit of info to add to the discussion
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Re: R-985 operation and leaning.

#10 Post by peterdillon » Tue Dec 05, 2017 9:03 pm

Didn't know about the jet change although the owner of our maintenance facility said that their could be one of 2 different main jets in any Beaver so that all makes sense.
Our Beaver has both the manual and electric and I have seen lots with the electric but never even thought to look to see if the wobble pump was still there. I always use the manual but check the electric every once in awhile in flight by monetarily turning it on and watch it bump the pressure.
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Re: R-985 operation and leaning.

#11 Post by Rowdy » Sat Dec 09, 2017 11:08 pm

twistedoldwrench wrote:
Tue Dec 05, 2017 7:26 pm
Another point to consider is that the 985 carburator was originally set up to burn 80/87 fuel. Back in the early 80's ?? the OH shops started to put a bit bigger main jet in the carb to add a bit more fuel at take off for additional cooling, as the 100/130 burned somewhat hotter. This caused the fuel burn to be somewhat more than the 1945 manual called up. Just an interesting tid bit of info to add to the discussion

Incredibly erroneous. Higher octane fuel does NOT burn hotter. It simply burns 'slower' as it may and is much more resistance to preignition and detonation. 100/130 does not make more power. just like running 94 in your car makes no difference than 87, so long as it is not prone to preignition (boost, high compression, crazy advanced ignition timing). 100/130 was meant for the multi row supercharged big radials and big flat motors that got HOT and ran a LOT of boost. Simply to stop detonation.

You are right that they did in fact swap to larger jets, but that was at the behest of lowering cylinder temperatures, as they found you could actually use a richer mixture to aid in cooling to prolong engine life. One of the many reasons they went from like 900hrs to 1400hrs TBO in the 985.. among other things :rolleyes:

Short hops, low alts, don't be leaning that poor ol 'jr. They like it a bit rich.
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Re: R-985 operation and leaning.

#12 Post by W5 » Mon Dec 11, 2017 8:31 pm

The multi row supercharged radials mainly used 115/145; until it was no longer available; which differed depending on location.
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