Warm up procedure for P&W R2800?

[HighBypass 2,339]

My Google-Fu is weak. Having played around with the freeware C46, Yes, Libardo Guzman's freeware aircraft does give you some decent gauges and prop condition levers you can play with. I'm curious as to the procedure for warming these radials up in real life, just to watch the numbers in the sim :) . For example, as soon as FSX:SE loads the plane with engines running they are idling at a few hundred rpm with the low oil pressure lights illuminated. The lights only go out once I've advanced the condition levers to give more than 1000 rpm.I would have thought low oil pressure was bad regardless of engine temp/rpm.

 

Cheers!

[stans 702]

I'm not a real pilot nor mechanic, but it is my understanding that cylinder head temperature, oil temperature, oil pressure, and fuel pressure in the MS flight sims are tied directly to engine RPM.  Unless custom coding is performed, you can sit an aircraft in flight sim in the desert during the heat of the day and run the engines all day long with cowl flaps closed and not overheat.  Do that with a real aircraft and you will destroy the engine.  Custom coding in flight sim is possible.  A2A does it with their AccuSim packages.  For freeware, you can try RealEngine.

From what I have read in numerous manuals, warm up for the R-2800 is with cowl flaps open and engine turning 900-1000 rpm.

[Chock 17,769]

As with your car, the oil pressure warning light will come on when the ignition is on, and it will stay on until the oil pressure comes on, it's if it stays on that there is a problem. It takes a while for the pressure to get up, so it is not unusual for an oil pressure light to be on for a brief period, if it stays on though, you''re either low on oil, or the engine is indicating a problem, such as the oil seals being blown or whatever, since there is a sensor on the back of the engine which reads how much pressure there is in the oil system. Needless to say, if you are p*ssing oil out because of a blown gasket or a loose hose clamp or whatever, it is a fire risk, so that's why you watch that PSI reading.

Depending on how your aeroplane is simulated, and to what level of realism, it may be using (or you may have chosen to use) oil dilution for a start up in the cold, which is basically where a bit of fuel is mixed in with the oil in order to thin it down a bit so the engine will crank more easily. Also note that oil controls the propeller pitch mechanism as well as lubricating the engine's moving parts on those big old radials, so when you are running the thing up to warm up, you should vary the prop pitch to clear congealed oil from the propeller pitch mechanism. If you don't, it can affect the oil pressure a bit, and of course having a load of gunk in the prop hub isn't a good idea anyway.

The cowl flaps on most radial engines should be open for ground operations, some people mistakenly think they can close the cowl flaps and warm the engine up a bit quicker, but all that will do is make the cylinder heads get hot and cause problems, so keep the cowl flaps open. This is especially true if you use oil dilution, because owing to how the dilution takes place, some of that fuel which gets mixed in with the oil to aid starting might not get burned off, and then if you have the cowl flaps closed and the engine getting hot with a load of unburned fuel dripping all over the shop, it can make the engines set on fire lol, this is because the priming fuel on most radial engines only goes in the top cylinders, and then of course if there is too much in there, it'll backfire the thing when you crank it and have unburned fuel dripping all over the engine and pooling in the bottom of the engine cowling as well as being over all the cylinder exteriors. This is why you often used to see people stood next to the engines with a fire extinguisher when they were starting them up, even if you are doing it all correctly, the amount of oil a radial engine flicks about all over the place when starting up is staggering, you literally get covered in oil and sh*t when stood near it, so fires were not that uncommon lol.

Expect to see the oil pressure light on at very low RPM and just after having started the thing up before it is pumping everything around properly and has burned off or cleared any gunk from the system and warmed up the oil to a suitable operating temperature. Once up and running, oil pressure gauge indications you should be seeing for typical RPM settings on a big radial such as the R2800 are as follows:

Engines idling... 25 psi (any lower than that and there is most likely a problem)

up to 1400 RPM... 50 psi

past 1500 RPM... between 55 and 90 psi

past 2000 RPM between 60 and 100 psi

 

 

[Alan_A 1,650]

The DC-6 POH lists the following procedures for warming up and running up the R-2800s (see below).  Some of the steps (e.g. water injection, superchargers) are specific to that aircraft, but this should at least give you the broad outlines of what to do and in what order, and what to look for.  Numbers for fuel pressure, oil pressure and oil temperature aren't specified here, but should be along the lines Chock suggested.  And yes, cowl flaps open.

If you really want to get a handle on managing a big radial, you can't do better than A2A.  The P-47 puts you in charge of all the plumbing of an R-2800 - cowl flaps, oil cooler, intercooler for the turbocharger system, etc.  The T-6 simulates hydraulic lock, so hand-propping is required.  The B-17 models damage to individual cylinders.  The T-6 and the Connie allow primer-only starts.

Be careful - detailed simulation of radial engines has been known to lead to an obsessive hobby in itself... 

 

Quote

 

2.3. ENGINE WARM-UP
Throttles—adjust to 1000 engine rpm until engine and cabin supercharger oil
temperatures are up to the minimum.

2.4. ENGINE RUN-UP — On dry runways, all four engines can be run up simultaneously.
(Gust lock must be disengaged.)
(1) Propeller reverse pitch—check.
(2) All engines-1500 rpm.
(3) Propellers—test; return to take-off position after testing.
(4) Propeller feathering—check.
(5) Engines—manifold pressure equivalent to field barometric pressure.
(6) Fuel and oil pressures—check.
(7) Cylinder and oil temperatures—check.
(8) Generator amperage and voltage—check.
(9) Inverters—check voltage.
(10) Blowers—”HIGH” then “LOW.”
(11) Magnetos—check.
(12) W/A injection, system — switches “ON” to bleed system, and check.
(13) BMEP indicators-check.
(14) Cabin supercharger oil pressure and temperature—check.
(15) Engines—1000 rpm.
(16) Pitot and airscoop heater amperage—check.
(17) Propeller de-icing system—check.

 

 

[Chock 17,769]

44 minutes ago, Alan_A said:

Be careful - detailed simulation of radial engines has been known to lead to an obsessive hobby in itself... 

Yup 

[Patco Lch 1,464]

It amazes me the turbine engine wasn't developed before the recip considering the complexity. I guess the recip was born of the steam piston concept. 

[HighBypass 2,339]

Thank you very much , Gentlemen. I'm not sure of the level of coding involved in the freeware C46. I look upon it as a (very!) light intro to the husbandry of big radials LOL! I'm inclined to believe the engines behave as Stans says. It has cylinder head temp gauges that appear to read ambient until the engines are started.The oil pressure at idle is above 25psi despite the oil lights staying on. If I increase throttle or move the condition levers to get rpm just over 1000 then the lights go off. 1000 rpm is the number any less and the lights come on even with nigh on 60 psi!! I'll try and grenade a cold virtual engine .

Oil temp does warm up as the engine warms. Oil dilution doesn't appear to be modelled - no switches for it either.

I've not tried to see how hot the the engines will go if I just leave them idling - as Stans says, I don't think they'd ever overheat. In flight however, I've seen the temps go past 200.... before I pull power and condition levers.

 

Dammit! I thought I was a jet guy!! 

 

[Alan_A 1,650]

2 hours ago, PATCO LCH said:

It amazes me the turbine engine wasn't developed before the recip considering the complexity. I guess the recip was born of the steam piston concept. 

It was only after I got to know the Wasp Major (thanks to the A2A Stratocruiser) that I realized that the turbine wasn't just a nice evolutionary step - it was an absolute necessity.  The story of those big late-model piston engines is that the demand for power has reached a point where the mechanical system and the metal itself can't stand up to it.

The original recips were steam-driven, of course, and the original turbine was a steam turbine.  There's a wonderful description in John Maxtone-Graham's classic The Only Way to Cross of Parsons demonstrating it by racing the Turbinia (his prototype demonstrator) into the middle of Queen Victoria's Diamond Jubilee Fleet Review in 1897.  HMS Dreadnought was powered by steam turbines.  So were RMS Mauritania and Lusitania.  The rival Titanic wasn't - she had a turbine driving the center propeller and recips on the outboards - one of several ways in which she wasn't as advanced as the Cunard ships were.
 

5 minutes ago, HighBypass said:

Dammit! I thought I was a jet guy!! 

Much as I'm fascinated by radials and have clearly spent too much time managing simulated ones, I'm actually more comfortable around jets.  All those moving parts scare me.  Cf. Wasp Major, above... 

BTW, it's possible to create a scripted (that is, not fully modeled) piston engine that gives you some of the flavor of operating them.  The Manfred Jahn & Team C-47 does this well.  The PMDG DC-6 has a scripted startup but still demands that you pay attention to the operating limits.  A2A is probably still the gold standard but there are some other enjoyable ways in.

Of course, like we said, once you find your way in, you may never come back... 

[Chock 17,769]

2 hours ago, PATCO LCH said:

It amazes me the turbine engine wasn't developed before the recip considering the complexity. I guess the recip was born of the steam piston concept. 

Probably a lot to do with the minerals available in the 30s and 40s when jet engines were first being developed as an idea; this was when many minerals required for the production of the metal used in the hot parts of jet engines were among the rarer strategic materials, thus part of the reason various countries were fighting over the land where you could find such minerals in the first place.

As a result of this, the first few turbojet engines were not very durable, the Jumo 004 jet engine used on the Messerschmitt Me-262 was good for about 30 hours of operation, and much of that short lifespan was indeed down to the lack of availability of minerals in sufficient quantity to make more specialised alloys for not only the Germans but for all combatants, but it proved more of a problem for the Germans because they were placing such reliance upon the hope that 'wonder weapons' would redress the balance for them.

France was of course one of the major countries involved in WW2; being occupied by the Germans in the north and under their control in the south under the Vichy, this meant the Germans had access to large quantities of bauxite, which is the main mineral necessary for the production of aluminium, in fact bauxite is actually named after its place of discovery, Les Baux de Provence, in southern France. Although not generally acknowledged in many WW2 histories as one of the reasons for the expansion aims of Germany in WW2, bauxite reserves in France certainly was one of those reasons and was one of the concerns Britain had upon losing the Battle of France, since a lot of the aluminium they used for aircraft production came from France.

However, the Jumo 004 used in the Me262 was originally designed to use far fancier metals than mere aluminium, including ones made from stuff such as as cobalt, nickel and molybdenum, all of which Germany did not have a lot of, so the Jumo 004 was redesigned to replace all those parts with ones made from mild steel with an aluminium coating. This worked, but those compromise parts were progressively weakened by the exposure to the heat a jet engine produces, which is why the engine was good for only a few hours of operation. So like a lot of weapons and other technologies the Germans came up with, they were undeniably brilliant and very advanced, but they weren't very smart from a strategic standpoint and it was the allied countries after the war which were best able to profit from that genius when such exotic materials were at least available, which meant jet engines could become a practical proposition.

A good example of this lack of tougher metals spoiling the effectiveness of a weapon is the V-1 Fieseler Fi-103 flying bomb. It had a fairly accurate autopilot system, but the tailpipe was made from cheap thin mild steel, which might not seem important for a pilotless bomb which only ever had to make one flight, but the exhaust flame would burn through that cheap thin metal fairly quickly and then the resultant holes in the tailpipe would effectively vector the thrust sideways, making the V-1 go off course.

[Patco Lch 1,464]

That's interesting information. You two Alans  must have PHD'S in just about every thing. Appreciate you guys.

[Alan_A 1,650]

26 minutes ago, PATCO LCH said:

You two Alans  must have PHD'S in just about every thing.

Can't speak for the other Alan but for me... it's really just some engine parts I picked up on the streetcorner... 

[ckyliu 1,749]

Just to add to what the other chaps have said above, typically you don't sit at minimum idle rpm with an aviation piston engine for long because the spark plugs start to get fouled with oil, an occasionally burst of throttle can be used to burn it off (and produce plumes of blue smoke too!)

Also when they engines are cold (you're warming the engines up) you would also use an increased idle rpm.