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 Post subject: Radial engine operation
PostPosted: Sun Feb 18, 2007 10:06 am 
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I've been around or behind large radials since 1968 and have always been one to "BABY" these expensive pieces of machinery. We have an on going debate within our group that centers on how to operate these engines (1820's, 1830's) with regard to full power use on takeoff and cruise climbs vs. manaul listed power settings. I'm well aware of the power enrichment valve and the pros and cons if you lose an engine on take off. I'd very much like to hear from other owner/operators on the proceedures they use to keep these big engines healthy. Thanks very much in advance for any and all feedback.

Jake Fendermen Fendermen's the name, flying's the game :D


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 Post subject: radials
PostPosted: Sun Feb 18, 2007 10:41 am 
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According to an ad, an Alaskan freight co. got good results when switching from mineral oil to Phillips 25w-60 in C-47s, etc. The problem with owner info is it is all kind of opinion, a guy does it one way and assumes it works best. Nobody takes 50 radials or 50 Merlins and runs half one way and half the other IN A SCIENTIFICALLY CONTROLLED STUDY and checks the results. In the great days of Rolls Royce they had test runs going 24 hours a day. If something failed they made it better. It worked great unless you were a neighbor trying to sleep. Perhaps the airlines have good data on radials.I rode with some guys last year who belive T-6 takoffs shoud be done at 30" rather than the book 36", if I recall the numbers right. We had some real fence skimming climb outs!

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PostPosted: Sun Feb 18, 2007 11:33 am 
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P&W manual sez 36" and 2250 rpm for T/O with the R1340, thats the way to fly it.

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 Post subject: radial engine operation
PostPosted: Sun Feb 18, 2007 3:58 pm 
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Joined: Sat Jun 03, 2006 7:30 pm
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Bill & Stoney, Thanks for the input. I owned 2 different T-6's over 31 years and always used 36" MP on takeoff. I'm looking more on feedback for the DC-3 & S-2F and any other large round engines. I did check out in the Gordon Plasket TF-51D in 1979 and I remember we only used 56" MP on takeoff. Those were the days. JF :D


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 Post subject:
PostPosted: Sun Feb 18, 2007 9:05 pm 
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Click on Randy Sohn Warbird Notes.
http://www.enginehistory.org/operation.htm


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 Post subject:
PostPosted: Sun Feb 18, 2007 10:58 pm 
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OK, so I come from an auto racing background but hydraulic lock is hydraulic lock no matter what the engine is in.

I am somewhat confused in the discussions of not walking the prop through backwards. I understand the theory that if you walk through backwards, when the intake valve opens, the oil is forced into the intake manifold. However, if the four stroke cycle is reversed, it becomes exhaust, power, compression, intake, exhaust...

So, if there is oil in the cylinder that will be forced through the intake valve on the "intake stroke" and then back into the cylinder when the next intake stroke opens the valve, the next stroke through would be the exhaust which would then force the oil out the exhaust valve and into the exhaust manifold. With sufficient cycles through, all oil should be forced into the exhaust manifold, no?

Now the only issue that remains is if the cylinder with oil in question happens to be on the compression stroke, whether you are pulling through forward or backward, hydraulic lock is the same.

So, I think that as long as you are not at a compression stroke, it would almost be better to pull through in reverse rotation as the stroke immediately following the intake (valve open) is the exhaust (valve open) thus pumping the oil directly into the exhaust.

So what am I missing?

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 Post subject:
PostPosted: Mon Feb 19, 2007 1:06 am 
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the way I pull them thru is to NEVER go backwards, unless it is due to a over prime. The oil could go back into the intake, and when it starts, it can get pulled back into the cylinder and then you get a hydraulic lock when the engine is running. If I hit a hydraulic lock, it is far better to pull some plugs until you strike oil. Also, pulling it thru is not a race, slow steady pressure on the compression stroke and let it bleed off, if you haul on the prop for all your worth, you can cause major damage if you run into a hydraulic lock.

Any radial can hydraulic on you, even one that has never done so in the past. The DC-3 I take care of sat for a month or more with no trouble. We ran it up one day, the next day we were going to run it again and I went to pull it thru and after 4 blades, it locked up tight. Never trust a radial engine when it comes to hydraulicing, ALWAYS pull them thru if it is physically possiable, some planes it is not possiable, IE the PBY, C-119, HU-16.

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 Post subject:
PostPosted: Mon Feb 19, 2007 8:48 am 
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Never pull a radial through backwards for the reason Matt said. It pulls the oil that caused the lock up into the intake tube, seeming to clear it, until the engine starts and you get all that oil back in the combustion chamber with the engine running. Theoretically the clutch on most starters would prevent most damage by slipping when it came up against a lock – if the engine fires all bets are off.
I only operate a small radial, but one with aluminum link rods making it particularly subsceptable to damage. Any gurgling sound is reason for me to remove the lower plugs and clear it out. (R755-B2)


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 Post subject:
PostPosted: Mon Feb 19, 2007 11:38 am 
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Matt and Skybolt are correct. You have to answer this, where do it go?. Another thing to consider is the brushes on the starter and generator. The armature can chip the brushes because they are set at an angle. The same is true if you have a dry air pump on the engine. The rotor and vanes are carbon, and very delicate to reverse rotation.

I've had to take the lower four front plugs out of an 1820, and start it with them out to purge oil from the induction system. It messy, but it works.

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 Post subject: P&W
PostPosted: Mon Feb 19, 2007 12:11 pm 
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Stoney, on the T-6 power setting for takeoff, I'm with you. It had been some time since I have flown a T-6 (John Reynolds), but I thought I recalled 36" in the manual. The situation was, it was someone else plane so you do what they want. It may have been 30" or 32", in any case it doesn't leap off the runway. I wonder if there is any evidence that the lower power setting extends engine life at all. I doubt it.

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PostPosted: Mon Feb 19, 2007 12:30 pm 
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From two B-25 operators I know, Tom Reilly and Larry Kelley, I have been told that there is a set of alternative minimum power settings in the manuals for the R-2600's, which is based on the octane rating of the fuel used. The power settings for take off, which are 44inches of MP on the R2600, were designed for 115/130 octane (?) which is not readily available today. The lower octane rating of the 100LL available causes considerable damage to valve seats when run at high manifold pressure. So both of them, and quite a few other operators, have been running lower manifold pressures at take-off and go-around. Surprise, surprise, they have had less cylinder changes at annual and longer life on cylinders in general. Both of them, when their airplanes were run at the normal take-off rating of 44 inches MP, at next annual needed cylinder changes.

Evidently, this concept has been hard to take by many operators, some of whom continue to operate their aircraft an manual settings, and don't use alternative minimum power settings. But at the 2006 NWOC, this was a topic of discussion in the B-25 operators session, and more people are coming to use it.

From personal experience with vintage motorcycle engines on this crappy gas made today, and the continued re-formulation of standard gasoline including aviation gasoline, I am inclined to believe them on this one. But I don't have a radial to fly behind and play with this stuff, so everything said here is second hand. But if you are involved in the operation of an engine which could use alternative power settings, and are at sea level, this wouldn't be a bad thing to play with and compare over the course of a year's operation between annuals.

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 Post subject:
PostPosted: Mon Feb 19, 2007 3:42 pm 
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When the engine shuts down and a lower cylinder happens to be on the intake stroke, would the intake tubes be the collecting point for the oil? If the cylinder was on compression, "lock" would result, and if on the exhaust stroke, oil smoke on start up?

If I understand correctly, when you pull through and feel the "lock" it would really not make any difference from that point whether you then went forward or back as a lock is a lock and the plugs need to be pulled and the cylinder head drained?

Thanks, :?

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 Post subject:
PostPosted: Mon Feb 19, 2007 4:09 pm 
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sdennison wrote:
When the engine shuts down and a lower cylinder happens to be on the intake stroke, would the intake tubes be the collecting point for the oil? <

No, it would just give it more area to fill with oil, There is no oil in the induction system, the oil comes from the crank case and pistons and guides.


>If the cylinder was on compression, "lock" would result, and if on the exhaust stroke, oil smoke on start up? <

the smoke is from oil collecting in the exhaust, and inside the cylinders.

>If I understand correctly, when you pull through and feel the "lock" it would really not make any difference from that point whether you then went forward or back as a lock is a lock and the plugs need to be pulled and the cylinder head drained?<

in my book, yes, pulling it backwards does not do anything cept makes you think you don't have a problem. If you hit a lock, the only fix is to pull plugs until you strike oil.



Thanks, :?

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 Post subject: radial engine operation
PostPosted: Mon Feb 19, 2007 6:09 pm 
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Flight Sergeant

Joined: Sat Jun 03, 2006 7:30 pm
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Hello Forgotten Field,

That's the kind of feed back I'm looking for and appreciate your input. I'm interested if any other operators are using reduced MP on takeoff and if they have noticed less or more maintenance. I'd also like to hear if any owner/operators are using lower power settings in their climbs to altitude especially on the DC-3/S-2 aircraft.
Thanks again. Jake :D

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 Post subject:
PostPosted: Mon Feb 19, 2007 7:42 pm 
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We pre-oil and manually push through all the bomber engines. Although I have heard that the 1830's have hydo locked I have never seen it. The 1830 is really easy to push through one handed...9 blades an engine. The 1820's on the B-17 require a bit more effort to push through but you can feel the oil in the bottom cylinders, and you can feel it flow out of the cylinders. The B-25 is a whole "nother" animal. It usually takes two people a blade to pull the props through and when it locks, plugs are coming out. I know some owners that use the starter to "bump" the props through, counting the clutch if it locks. We don't.

As for power settings, usually no more than 40" for takeoff power and 35" for Meto power(all 3 airplanes). Part of our pre landing checklist is briefing the missed approach which is planned at Meto power, beyond that it is "whatever it takes". From what I have witnessed, pre-oiling, not allowing a reverse loading to happen, and constant monitoring CHTs has prolonged our engine life remarkably.

JimH


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