Engine bearings and how you can keep them happy

[Diesel_Thunder]

This seems to be a hot topic lately, so I've put in some research to learn as much as possible about this, and what we can do to mitigate the problem with wrecking our bearings.

Background on the problem:

This is a problem that is unique to radial engines, and is not much of a factor in inline or V engines, in that reciprocating loads can damage bearings. Under normal conditions, combustion happens, pushes the piston and connecting rod down in the cylinder, which turns the crankshaft. Crankshaft turns the reduction gears, gears turn the propeller, propeller creates thrust. This is true for both radial and inline/V engines.

Lets briefly explore V engines, like the famous Merlin 61 V-12, used in warbirds such as the Spitfire and Mustang. The crankpins on the crankshaft were only attached to two connecting rods, and being a four stroke engine, only take the force of a power stroke only once per revolution. This is the key concept here, but bears repeating, the crankpins only take the force of a power stroke only once per revolution in a V engine. Here's a picture illustrating this. Note that two pistons share a crankpin.

 

 

Radial engines are a whole different animal compared to their V shaped cousins. The crankshaft layout is a lot simpler, with one row of cylinders sharing one crankpin. The cylinders are then spaced evenly around that point, and nearly always feature an odd number of cylinders in that row. Having an odd number of cylinders simplifies the ignition timing, as every other cylinder fires in turn. (a nine cylinder would have the firing order of 1-3-5-7-9-2-4-6-8) Since all of the cylinders have to share one crankpin, the crankshaft is built much larger and stronger to handle the forces involved. The connecting rods also have a unique arrangement, with one serving as the master rod which connects to the crankshaft, and the other cylinders rods are articulating rods that bolt to the master rod. Looks something like this:

 

 

On to our R-2800 engines now. The cylinders in one row, nine of them spaced 40° apart, share one crankpin, and every other cylinder fires as the engine runs. The crankshaft thus takes the force of a power stroke every 80° of rotation, or 4.5 times every revolution in each row. Contrast that with the V engine where a crankpin only takes one power stroke every revolution. That's a lot of force on the crankshaft, but fortunately Pratt and Whitney thought this through and added a hole for pressurized oil to flow in between the crankshaft and master rod assembly at the correct place where a power stroke would be pushing down on the crank (the thrust side). You certainly don't want any metal on metal contact, especially in the one spot on the crankshaft where power strokes are pounding down on it. A lot of radial engine crankshafts featured this oil hole, not just ones built by P&W.

 

Here's what the R-2800 crankshaft looks like. There are several bearings pointed out here, the mains and the crank journals. The mains are supported by the crankcase, and are not the ones that we damage by running the engine improperly. Those would be the crank journals that take the damage. There are only two, one for the front row, and one for the rear. In the photo, if you look at the rear crank journal (right hand side) you can see the oil hole for that bearing facing downward.

 

This (and a lot of others) radial engine were very well designed, and provided many hours of reliable service (combat damage and ham fisted pilots not withstanding). So how do the bearings get damaged? By reversing the reciprocating load on them, or in other words, windmilling the prop.

 

The engine is designed to provide power to the prop and is built to do exactly that. When power is reduced and sufficient wind speed exerts more force on the prop than what the engine is providing, the loads in the engine are reversed by 180º. The prop is now driving the crankshaft, which is now moving the pistons around. The crank journal is taking the load on the side opposite of the oil hole, where there is very little oil. This leads to metal on metal contact, an overheated bearing, and metal in the oil, loss of power, and given enough time, total engine failure. This is likely amplified somewhat in that since the engine is still turning it has oil pressure, and that is likely exerting some hydraulic force on the thrust side of the crank, pulling the opposite side in a bit closer. Oil pressure eventually falls and the oil temperature rises due the engine wear and friction (not sure if DCS models this behavior). While this is happening the piston rings are also fluttering in their grooves, leading to damaged ring lands and broken rings (not sure if DCS models this either). How quickly damage accumulates is a function of severity and time. A high RPM steep dive would damage the engine more rapidly than a moderate RPM shallow dive.

 

Now that we know the how and the why the bearings get damaged, how do we prevent it, and why does this happen more during landings? And with that, how do we know when the engine is being windmilled?

 

The point where the engine starts to be windmilled is different between aircraft (weight, speed, props, RPM, and MP settings). Aircraft that had a BMEP gauge or torquemeter had a decent idea of when this happened as those instruments were a good direct measurement of power output. Other aircraft just had to make do with the RPM and MP settings. One of the old "rules of thumb" was to keep at least one inch of MP for every 100 RPM. If you're doing steep dives link the prop lever with the throttle and pull them both back during the dive. Don't close the throttle entirely during the dive, keep some power on.

 

For landing techniques, there are two schools of thought. The military method and the airline method. I'll elaborate on both, but keep in mind the time frame of this (1930's to 1960's), the heyday of radial engine aircraft.

 

The military technique mostly utilized the overhead break landing pattern, with a high RPM setting during the approach. The Mustang usually had 2,700 RPM set, the Jug set 2,550 RPM. The Air Corps/Air Force preferred to have its pilots ready for a go around, hence the high RPM setting. During the war, if the engine could be used for the next mission, great. If not, a new one was installed and the damaged one sent out for overhaul. This mentality carried on into the Cold War when the military had a fairly generous budget. Keep in mind that jets were up and coming as well. Accident rates with them were higher, mostly due to pilots transitioning from piston engines to jets. Piston engine can deliver power pretty quick when you push that throttle up, early jets not so much. Jet engine spool up times took a lot longer than pistons, especially if one was on short final. It took a while for the Air Force to adopt the stabilized approach (high drag, high thrust) with jets. The high RPM approach with pistons, stayed with them. Better to risk engine damage and a go around in order to use the plane (and pilot) again. Maintenance costs were not of much concern.

 

If you are going to use the military high RPM approach, follow the 1" MP per 100 RPM rule of thumb. With RPM set at 2,550 RPM, don't let the MP fall below 25", until you are on final and near the flare. By then your airspeed should be between 90-110 MPH, and your RPM should naturally fallen some. The prop should be sitting on the low pitch stops and there won't be sufficient wind speed to drive the prop.

 

The airline technique was much different. They had to stay profitable and keep happy customers, and work within much tighter budgets than the military. Pilots wrecking engines would eat up maintenance budgets with replacement engines, not to mention taking a bird out of service and cancelling flights. Aircraft only make money when they are flying. Their technique with descents and landings was to start down sooner (shallower descent) while keeping the engines at cruise RPM settings (around 1,900 RPM). and also not allowing the MP to fall below the 1" per 100 RPM (or following specified BMEP or torque setting if equipped with that instrument). This would be maintained during landing, with the the RPM brought up at the flare when the throttles are closed when there was no risk of the prop driving the engine. This led to quieter operations and higher engine longevity.

 

This method gives some more flexibility with power settings as you are not constrained to a fixed RPM during the descent and approach.

 

The key points in summary:

 

• Radial engines are pretty tough, but can be easily damaged if its pilot is not careful with the engine settings.
• Pull the RPM back before entering a steep dive and keep a little bit of power on.
• During descent and approach, keep at least 1" of MP for every 100 RPM to ensure the engine is providing power and not being driven by the prop.

 

 

Edited April 20, 2022 by Diesel_Thunder

[_Spad_]

Wow! Thanks for taking the time to explain this. Makes learning the Jug all that much easier.

[PL_Harpoon]

I'd like to add one clarification.

Just because your prop lever is set to 2550 doesn't mean your actual RPM is going to be 2550.

 

That's why at low speed you can easily idle the engine - there's not enough wind to windmill the prop so the RPM will naturally drop.

I do pretty much all my landings (finals) with throttle at idle.

 

On the other hand you can have your prop lever fully backwards and still have high RPM if you're fast enough. In this case you cannot reduce MP without risking damaging the engine.

 

 

[grafspee]

I do my landings exact the same, i cut throttle to 0 when im landing. While in final i test, if i wind mill or not, so i drop throttle a little bit when engine rpm drops then im good to go for throttle idle.

You cant afford to keep throttle opened especial on short airfield we have on normandy or channel maps.

I use same rule, 2550rpm minimum MP = 26"

Still i don't understand why engine is dying at 2900rpm, manual states that 3060rpm is max, 2900rpm should not kill engine. No matter the MP even 52" wont save the engine. I guess that this is error in damage modeling. 

Edited February 2, 2021 by grafspee

[Nealius]

I'm curious how pilots handled throttle/RPM in the overhead break. They would come in low and fast at max continuous, break upwards to downwind. Easy enough to cut to idle in the Mustang or Spit so you can safely lower the gear, but in the Jug if you only reduce to 26" you would need so much G to get down to gear down speed your abeam distance would be way too close to the runway. 

[grafspee]

1 hour ago, Nealius said:

I'm curious how pilots handled throttle/RPM in the overhead break. They would come in low and fast at max continuous, break upwards to downwind. Easy enough to cut to idle in the Mustang or Spit so you can safely lower the gear, but in the Jug if you only reduce to 26" you would need so much G to get down to gear down speed your abeam distance would be way too close to the runway. 

Looks like P-47 needs different pattern.

[Nealius]

The period documentary "Thunderbolt" shows them doing the same pattern as everyone else in Italy during the war.

[Diesel_Thunder]

Here's the landing diagram from the real P-47N manual. It's the same as the D model pattern with two exceptions. The D model calls for 2,550 RPM and turns no less than 130 MPH, where the N model specifies 2,400 RPM and turns no less than 150.

 

The sequence is as follows:

 

• Landing gear can be lowered below 200 MPH
• Flaps can be lowered under 190 MPH
• Reduce speed to 140-150 MPH
• Set RPM to 2,550, mixture to AUTO RICH, and propeller control to AUTO (electric switch on panel forward of the throttle lever)
• Turns in the pattern no less than 130 MPH
• Final approach speed 115 - 120 MPH
• Tail wheel locked

The manual does caution against doing long, flat approaches as it leaves little time for emergency action in case the engine dies. It also advises against throttling up in turns as that pulls the nose up and steepens your turn.

 

15 hours ago, PL_Harpoon said:

I'd like to add one clarification.

Just because your prop lever is set to 2550 doesn't mean your actual RPM is going to be 2550.

 

That's why at low speed you can easily idle the engine - there's not enough wind to windmill the prop so the RPM will naturally drop.

I do pretty much all my landings (finals) with throttle at idle.

 

On the other hand you can have your prop lever fully backwards and still have high RPM if you're fast enough. In this case you cannot reduce MP without risking damaging the engine.

 

Absolutely! As airspeed decreases the prop governor brings the pitch back to maintain RPM until it hits the mechanical limits, and from that point RPM is controlled by power and airspeed. You know when this happens as the RPM gauge starts dropping from its setting of 2,550.

Edited February 2, 2021 by Diesel_Thunder

[grafspee]

This is from D model.

[Rover]

Man, we (I) really need a damage "debriefing" by the "mechanic" after a flight. I can't learn from my mistakes if I don't know I made them. 

[Nealius]

I'm not talking about standard landing patterns, I'm talking about the overhead break, which is not in the manuals. Mimicking the same flow, I cannot bleed enough speed without going full idle in the peel. See from 33:18:

 

 

Edited February 3, 2021 by Nealius

[grafspee]

I don't know if sounds are accurate but it is very clearly hearable that they cut throttle just before touch down.

So it could be some errors in FM ?

I cant test it i don't know entry speed.

I would tell that the were doing something like 220-240 mph no more

I managed to do something like this

 

Edited February 3, 2021 by grafspee

[Mogster]

Interesting article by Richard Grace on flying the P47.
 

He mentions the risk of engine damage from reverse loads caused by excessive windmilling, saying you can rapidly kill the engine. He also says landing is impossible with throttle on as you’ll just carry on flying floating above the runway. Engine failure seems to be a constant concern, he talks about glancing at the oil pressure gauge every few seconds. His comments about raising the gear as soon as possible are interesting. He says if the engine packs in (engine stress again...) then a belly landing causes much less damage than ripping the gear off. Not really a concern in sim land but interesting non the less.

 

https://vintageaviationecho.com/p-47-thunderbolt-nellie/
 

 

[Nealius]

What version of Jug is Nellie? The number printed on the side indicates -40, but there's no ventral fin and the cockpit layout is totally different than the -30 and -40. 

[Mogster]

It seems it was built in 45 as a D -40. It was in service with the Peruvian airforce till 1967, so lots could have happened to it in the meantime.
 

https://www.flyinglegends.com/aircraft/republic-p-47d-thunderbolt-g-thun.html

[RodBorza]

On 2/2/2021 at 1:38 AM, Diesel_Thunder said:

This seems to be a hot topic lately, so I've put in some research to learn as much as possible about this, and what we can do to mitigate the problem with wrecking our bearings.

Background on the problem:

This is a problem that is unique to radial engines, and is not much of a factor in inline or V engines, in that reciprocating loads can damage bearings. Under normal conditions, combustion happens, pushes the piston and connecting rod down in the cylinder, which turns the crankshaft. Crankshaft turns the reduction gears, gears turn the propeller, propeller creates thrust. This is true for both radial and inline/V engines.

Lets briefly explore V engines, like the famous Merlin 61 V-12, used in warbirds such as the Spitfire and Mustang. The crankpins on the crankshaft were only attached to two connecting rods, and being a four stroke engine, only take the force of a power stroke only once per revolution. This is the key concept here, but bears repeating, the crankpins only take the force of a power stroke only once per revolution in a V engine. Here's a picture illustrating this. Note that two pistons share a crankpin.

 

 

Radial engines are a whole different animal compared to their V shaped cousins. The crankshaft layout is a lot simpler, with one row of cylinders sharing one crankpin. The cylinders are then spaced evenly around that point, and nearly always feature an odd number of cylinders in that row. Having an odd number of cylinders simplifies the ignition timing, as every other cylinder fires in turn. (a nine cylinder would have the firing order of 1-3-5-7-9-2-4-6-8) Since all of the cylinders have to share one crankpin, the crankshaft is built much larger and stronger to handle the forces involved. The connecting rods also have a unique arrangement, with one serving as the master rod which connects to the crankshaft, and the other cylinders rods are articulating rods that bolt to the master rod. Looks something like this:

 

 

On to our R-2800 engines now. The cylinders in one row, nine of them spaced 40° apart, share one crankpin, and every other cylinder fires as the engine runs. The crankshaft thus takes the force of a power stroke every 80° of rotation, or 4.5 times every revolution. Contrast that with the V engine where a crankpin only takes one power stroke every revolution. That's a lot of force on the crankshaft, but fortunately Pratt and Whitney thought this through and added a hole for pressurized oil to flow in between the crankshaft and master rod assembly at the correct place where a power stroke would be pushing down on the crank (the thrust side). You certainly don't want any metal on metal contact, especially in the one spot on the crankshaft where power strokes are pounding down on it. A lot of radial engine crankshafts featured this oil hole, not just ones built by P&W.

 

Here's what the R-2800 crankshaft looks like. There are several bearings pointed out here, the mains and the crank journals. The mains are supported by the crankcase, and are not the ones that we damage by running the engine improperly. Those would be the crank journals that take the damage. There are only two, one for the front row, and one for the rear. In the photo, if you look at the rear crank journal (right hand side) you can see the oil hole for that bearing facing downward.

 

This (and a lot of others) radial engine were very well designed, and provided many hours of reliable service (combat damage and ham fisted pilots not withstanding). So how do the bearings get damaged? By reversing the reciprocating load on them, or in other words, windmilling the prop.

 

The engine is designed to provide power to the prop and is built to do exactly that. When power is reduced and sufficient wind speed exerts more force on the prop than what the engine is providing, the loads in the engine are reversed by 180º. The prop is now driving the crankshaft, which is now moving the pistons around. The crank journal is taking the load on the side opposite of the oil hole, where there is very little oil. This leads to metal on metal contact, an overheated bearing, and metal in the oil, loss of power, and given enough time, total engine failure. This is likely amplified somewhat in that since the engine is still turning it has oil pressure, and that is likely exerting some hydraulic force on the thrust side of the crank, pulling the opposite side in a bit closer. Oil pressure eventually falls and the oil temperature rises due the engine wear and friction (not sure if DCS models this behavior). While this is happening the piston rings are also fluttering in their grooves, leading to damaged ring lands and broken rings (not sure if DCS models this either). How quickly damage accumulates is a function of severity and time. A high RPM steep dive would damage the engine more rapidly than a moderate RPM shallow dive.

 

Now that we know the how and the why the bearings get damaged, how do we prevent it, and why does this happen more during landings? And with that, how do we know when the engine is being windmilled?

 

The point where the engine starts to be windmilled is different between aircraft (weight, speed, props, RPM, and MP settings). Aircraft that had a BMEP gauge or torquemeter had a decent idea of when this happened as those instruments were a good direct measurement of power output. Other aircraft just had to make do with the RPM and MP settings. One of the old "rules of thumb" was to keep at least one inch of MP for every 100 RPM. If you're doing steep dives link the prop lever with the throttle and pull them both back during the dive. Don't close the throttle entirely during the dive, keep some power on.

 

For landing techniques, there are two schools of thought. The military method and the airline method. I'll elaborate on both, but keep in mind the time frame of this (1930's to 1960's), the heyday of radial engine aircraft.

 

The military technique mostly utilized the overhead break landing pattern, with a high RPM setting during the approach. The Mustang usually had 2,700 RPM set, the Jug set 2,550 RPM. The Air Corps/Air Force preferred to have its pilots ready for a go around, hence the high RPM setting. During the war, if the engine could be used for the next mission, great. If not, a new one was installed and the damaged one sent out for overhaul. This mentality carried on into the Cold War when the military had a fairly generous budget. Keep in mind that jets were up and coming as well. Accident rates with them were higher, mostly due to pilots transitioning from piston engines to jets. Piston engine can deliver power pretty quick when you push that throttle up, early jets not so much. Jet engine spool up times took a lot longer than pistons, especially if one was on short final. It took a while for the Air Force to adopt the stabilized approach (high drag, high thrust) with jets. The high RPM approach with pistons, stayed with them. Better to risk engine damage and a go around in order to use the plane (and pilot) again. Maintenance costs were not of much concern.

 

If you are going to use the military high RPM approach, follow the 1" MP per 100 RPM rule of thumb. With RPM set at 2,550 RPM, don't let the MP fall below 26", until you are on final and near the flare. By then your airspeed should be between 90-110 MPH, and your RPM should naturally fallen some. The prop should be sitting on the low pitch stops and there won't be sufficient wind speed to drive the prop.

 

The airline technique was much different. They had to stay profitable and keep happy customers, and work within much tighter budgets than the military. Pilots wrecking engines would eat up maintenance budgets with replacement engines, not to mention taking a bird out of service and cancelling flights. Aircraft only make money when they are flying. Their technique with descents and landings was to start down sooner (shallower descent) while keeping the engines at cruise RPM settings (around 1,900 RPM). and also not allowing the MP to fall below the 1" per 100 RPM (or following specified BMEP or torque setting if equipped with that instrument). This would be maintained during landing, with the the RPM brought up at the flare when the throttles are closed when there was no risk of the prop driving the engine. This led to quieter operations and higher engine longevity.

 

This method gives some more flexibility with power settings as you are not constrained to a fixed RPM during the descent and approach.

 

The key points in summary:

 

• Radial engines are pretty tough, but can be easily damaged if its pilot is not careful with the engine settings.
• Pull the RPM back before entering a steep dive and keep a little bit of power on.
• During descent and approach, keep at least 1" of MP for every 100 RPM to ensure the engine is providing power and not being driven by the prop.

 

 

 

Thank you fro this. I'm RE-learning this bird since last updates. A different beast than before, no doubt about it, since now we have engine damage model one. Yesterday I broke the engine in a steep dive and didn't know why, the debriefing page just said ENGINE MAIN BEARING DAMAGE. That's what got me to your post. Makes sense now.

Now I'm using the prop +throttle attached technique and it is working fine. Boost off, for good measure.

 

And regarding all this discussion about landings, what I do and ever did was to go full RPM during the pattern, using throttle to control the power, very fast on turns (~150 mph) and final speed around 1110-120 mph. After I cross the threshold I take out the throttle and flare to touch down around 90 mph. Works fine in every allied bird I've flown.

Don't know how other pilots can land this bird on throttle idle on final. I find it very heavy to do that. Anyway, everyone finds what it is best for them. As long we don't destroy the bird on landing, everything is fine.

[GUMAR]

On 2/2/2021 at 1:58 PM, grafspee said:

Still i don't understand why engine is dying at 2900rpm, manual states that 3060rpm is max, 2900rpm should not kill engine. No matter the MP even 52" wont save the engine. I guess that this is error in damage modeling. 

I think you are right - its bug. There is absolutely nothing in manuals of P-47 or pilots memoirs about killing the engine with cutting throttle to idle for a moment (e.g. switching to full tank after aux gets empty). In any description of a dive, pilots just cuts the throttle off and goes down.

From my experience of flying Antonov2 I can say that there was nothing to an engine when sometimes we used it as an airbrake. At 3000-4000ft full RPM and cut the throttle to go down quickly. And there was no such restriction in FM. And neither I was told by our old experienced instructor with more than 10k hours on that type.

[Diesel_Thunder]

On 3/8/2022 at 9:35 PM, RodBorza said:

Thank you fro this. I'm RE-learning this bird since last updates. A different beast than before, no doubt about it, since now we have engine damage model one. Yesterday I broke the engine in a steep dive and didn't know why, the debriefing page just said ENGINE MAIN BEARING DAMAGE. That's what got me to your post. Makes sense now.

Now I'm using the prop +throttle attached technique and it is working fine. Boost off, for good measure.

 

And regarding all this discussion about landings, what I do and ever did was to go full RPM during the pattern, using throttle to control the power, very fast on turns (~150 mph) and final speed around 1110-120 mph. After I cross the threshold I take out the throttle and flare to touch down around 90 mph. Works fine in every allied bird I've flown.

Don't know how other pilots can land this bird on throttle idle on final. I find it very heavy to do that. Anyway, everyone finds what it is best for them. As long we don't destroy the bird on landing, everything is fine.

Glad you found it helpful!

I don't usually land with the RPM at 2,500. I vary the RPM as needed and keep an eye on the MP to make sure I always have some power on the prop. I have a TM Warthog, throttle on the right handle and prop on the left handle. For approach and landing I have them split (throttle lever advanced farther than the prop lever), and move them together that way. Keeps both the RPM and MP happy. Think the only time I go to idle is at the flare, but I'm about 90 MPH by that point anyway.

 

On 3/9/2022 at 4:33 AM, GUMAR said:

I think you are right - its bug. There is absolutely nothing in manuals of P-47 or pilots memoirs about killing the engine with cutting throttle to idle for a moment (e.g. switching to full tank after aux gets empty). In any description of a dive, pilots just cuts the throttle off and goes down.

From my experience of flying Antonov2 I can say that there was nothing to an engine when sometimes we used it as an airbrake. At 3000-4000ft full RPM and cut the throttle to go down quickly. And there was no such restriction in FM. And neither I was told by our old experienced instructor with more than 10k hours on that type.

That's awesome that you flew the An-2! Turboprop pilots love that technique, where they can pull the power back and push the props full forward. Slows them down too, and they don't have to worry about crankshafts.

[grafspee]

Testing conditions of P-47-D30 during NACA flight tests, this test were performed to determine longitudinal characteristic of the plane, any way they did dives at 15" and 2550rpm to speeds above 300mph and high and low alt.

They did glide test to speeds up to 400mph indicated but not prop rpm setting mentioned in test table conditions.

I assume that test were done with useful engine limits, so they actual did not kill engine every time when they did the tests, i think it would be pointless to test plane in that conditions.

Edited March 16, 2022 by grafspee

[Jobediah]

I have to say that this is the first DCS module I have purchased and the engine is extremely frustrating. There is little to no room for error. The fragility if this engine goes against anything I have ever learned. Caveat that I am no historian or professional engine builder. I love the module but the P-51 is so much more resilient and capable of finishing missions.

[Art-J]

8 hours ago, Jobediah said:

I have to say that this is the first DCS module I have purchased and the engine is extremely frustrating. There is little to no room for error. The fragility if this engine goes against anything I have ever learned. Caveat that I am no historian or professional engine builder. I love the module but the P-51 is so much more resilient and capable of finishing missions.

Wait until you want to use WEP in the -51, or you want to takeoff in hot weather with rads in auto and you'll change your mind quickly :D.

Seriously though, yes, keeping the engine healthy in -47 is a much more labour-intensive in DCS compared to Mustang. Partially because of questionable simulation of some things (prop and engine redline), but partially because of historic reasons - lack of manifold pressure regulator, fully manual operation of all flaps, gills and whatnot... The engine is bulletproof as long as you don't exceed limits (52" dry, 64" wet, 2700 RPM, all temps in green), but doing that is such a chore. Mustang is just more ergonomic and semi-automated all around.

[grafspee]

@Jobediah

Watch your oil temp, it is main reason why P-47's engine give up in DCS, in combat or in climb or at high power settings open oil cooler fully, if you set oil cooler at neutral position it will overheat in no time specially in warm weather.

Second thing is carb air temp, max is 40C or 50C can't remember exactly, but this is main limiting factor for turbocharger use, according to engine limitation you can pull 52 DRY and 64 WET MAP but max carb temp is also engine limitation, and manual says it, that in hot weather you may disconnect turbo for take off due to very high carb air temp limitation, conclusion is that there are cases that you can't pull 52 MAP or 64 MAP wet and you have to watch cylinder head temp, carb air temp rpm and MAP to be able to operate engine with in limits, it is much harder then in P-51

If for you cruise your P-47 at lean mixture do not forget to put it in to rich before increasing power, and for lean mixture max head temp is different then for rich mixture.

Edited April 29, 2022 by grafspee

[kablamoman]

Despite what some are saying with regards to the engine I have not had much luck getting it to work for me when fighting with it online. Granted, I haven’t even attempted it since SoW closed, but I’d find the engine would tend to die on me after a long successful sortie — half an hour to an hour — with a reduction in power, often when coming in to land. Temps and operating limits respected: No boost above the first red line without water, intercooler and oil shutters modulated to keep temps in green. And yet, all too often when turning base to final oil temps would spike uncontrollably high coupled with a loss of power at low speed at the worst possible time.

I do not trust the engine at all in this thing, and I have zero issues flying the rest of the warbirds. I still suspect something is very wrong with it.

[grafspee]

I did couple very long flights in P-47, 3 hours long, flight included high power climb 52/2700 also i used almost 70" at higher alt with water injection for couple minutes to test top speed and i managed to land safe. It wasn't combat flight but constantly watch of all gauges are required. Oil temp the most important, mine was wide open most of the flight

[peachmonkey]

I'm with @grafspee on this "issue", even though it's not an issue at all... unless it's about some VERY specific engine settings someone tries to achieve in DCS.

otherwise as long as I stick to the points below I never had any engine problems:

- keep the oil temps in the blue zone during ANY engine load

- keep the carb temps in the blue zone during ANY engine load

- don't use turbo on deck in normal flight situations

- use turbo only above 6k ft

- keep engine RPM's in green (2600)

- keep manifold at around 46"

- full MAX power with max turbo+2700+max manifold + WATER = will get you ~10 mins of WEP.  This is achieved at any alt.

 

I had a failure ONCE where I was climbing at 2600 and ~50" manifold.. but don't remember if it was the temps or the fact the manifold was in RED >50". Will test this out and see..