LaGG-3 Supercharger

[Chuck_Owl]

Hullo everyone!

 

Still flying the LaGG-3 and I didn't think I'd have so much fun trying to tame that bird. I finally figured out how to land and takeoff, but I'm at a point where I start wondering how well I know my machine. I realized that I didn't know how to use the supercharger, under what circumstances and why. I practically never use the supercharger (when there is one) on any plane, so I'm a bit at loss about what it's supposed to do. Could anyone be kind enough to provide me with some explanations?

 

Thanks in advance,

 

Chuck

 

P.S. Oh, and also, would anyone have recommendations about good books about Soviet WWII warbirds like the LaGG-3, Yak-1, La-5, Il-2 and the like? I'm not necessarily looking for pilot accounts, but more for an in-depth technical description of the aircraft structure, systems and performance a la "Haynes manual". There seem to be very few good sources in english... I've looked up in this topic http://forum.il2sturmovik.com/topic/1867-how-has-sim-expanded-your-bookshelf-just-bought-ospreys-lagg/?hl=bookshelf but, like I said, I'm not really looking for pilot accounts.

Edited November 20, 2013 by Chuck_Owl

[III/JG53Frankyboy]

a fast and lazy answer

http://en.wikipedia.org/wiki/Supercharger#Aircraft

 

books:

as an overview volume 1&2 of this

http://www.amazon.com/Soviet-Combat-Aircraft-Second-World/dp/1857800834

Edited November 20, 2013 by III/JG53Frankyboy

[Mewt]

No Haynes manual for the Lagg 3 but there is one for the 109. It's really good. Amazon.

[AbortedMan]

On my cell, so it's short, but you can watch your engine manifold pressure decrease as you climb higher and higher. I remember the gauge sitting at close to 12 at low altitude and dropping to 8 at around 3km. Popping the supercharger to stage 2 sent it back up to 11-ish by feeding the engine more air, since it was basically starving at at height.

 

Tl;Dr: activate stage 2 at around 2500m alt, back to stage 1 if you come back down.

[Requiem]

The supercharger has two stages which are used at different altitudes. The idea behind a supercharger is to compress air and force more of it into the engine. Having more air means you can burn more fuel at the same mixture ratio and get more horsepower.

 

I think the Lagg supercharger Stage 2 can be activated at 2000m (it's in the mission texts somewhere), but to be safe you can just wait until you notice your manifold pressure decreasing (due to lower air density at altitude) when at full throttle before activating Stage 2. If the MP is dropping at full throttle it means you aren't pulling as much air into the engine as you should be, so you then move to the next stage of the supercharger to bring back some engine performance.

 

Hope that helps.

[LukeFF]

The first mission indeed says to shift the supercharger into stage 2 above 2000 meters.

[BeastyBaiter]

I've noticed manifold pressure starts dropping at 1500m, been switching at 1600-1700m without incident.

[Blooddawn1942]

Regarding altitude...I never managed to climb significantly over 7000m. I assumed that the LaGG would climb higher. At the end it does not matter because most air combat on the eastern front took place in low and medium altitudes.

Just wondering.

[BeastyBaiter]

I've taken her to 10,100m. Top speed 210km/h IAS. I couldn't hold anything higher. From a practical standpoint, fighting above 5km/h would be less than optimal.

[Finkeren]

At 10,000m you're well above service ceiling, and anecdotal evidence suggests, that the LaGG was a poor performer at altitude, so it seems to me, that performance is just about where it should be. 

[SCG_motoadve]

Why not leave supercharger at stage 2 all the time, since it doesnt have any effect at low alt?

[SAG]

Why not leave supercharger at stage 2 all the time, since it doesnt have any effect at low alt

 

 

Because it generates engine drag, which makes you slower

[Finkeren]

Why not leave supercharger at stage 2 all the time, since it doesnt have any effect at low alt?

 

The supercharger uses power from the engine to compress air, the 2nd gear uses more power than the first, which means that below the designated altitude, you are using extra power and getting no benefit compared to 1st gear.

 

It's a different story with planes that have turbochargers, like the P-38 or P-47, because it uses exhaust gasses to drive a turbine that runs the compressor, thereby not stealing any power from the engine.

[SCG_motoadve]

Thanks for the info I am glad I asked.

[Plurp]

Quick Tests:  Stalingrad Autumn map: 100% Throttle & Prop: 50% Rads:  50% Fuel

 

300 m:  504 km/h stage 1:  481 stage 2

 

2000 m:  496:  480

 

3000 m:  467:  473

Edited October 12, 2017 by Beedo

[Finkeren]

Seems about right. Would be great if you had also registered temperatures.

The water temperature should be slightly higher from running the supercharger in the wrong gear at low level because of the strain it puts on the system.

[GridiroN]

Regarding altitude...I never managed to climb significantly over 7000m. I assumed that the LaGG would climb higher. At the end it does not matter because most air combat on the eastern front took place in low and medium altitudes.

Just wondering.

In a Yak 1b, which uses the same Klimov engine, there is a significant loss of MP at 2200+2500+. Using stage 1 at altitude would put you at a significant disadvantage. Edited October 12, 2017 by GridiroN

[Finkeren]

I've taken the LaGG-3 to about 9500m, it wasn't easy and it stopped having any kind of fighting capability long before that.

[Plurp]

Seems about right. Would be great if you had also registered temperatures.

The water temperature should be slightly higher from running the supercharger in the wrong gear at low level because of the strain it puts on the system.

 

At 300m, water and oil temps go down a bit switching to stage 2

Edited October 12, 2017 by Beedo

[Finkeren]

Strange, I would presume the opposite.

[Finkeren]

Nobody said, that not all engines in the sim are supercharged or that the supercharger isn't running all the time, nor did anyone claim, that you should shift supercharger gear the moment MP starts to drop off. There is a certain calculated altitude (or rather: certain outside air pressure) where the benefits of using 2nd gear starts outweighing the extra power used.

 

You are fighting windmills here Klaus. Noone has misunderstood things the way you seem to think.

Edited October 12, 2017 by Finkeren

[6./ZG26_Klaus_Mann]

So much disinformation out here. 

 

First of all: All ingame Aircraft are "using" the Supercharger ALL of the time. This isn't Mad Max. How else would you expect your Engine Intake Pressure to be higher than your surrounding Atmospheric Pressure?

 

Also: NO: You can't overboost in Second Gear. You have Wastegate, and that just blows excessive Pressure out of the System. 

 

YES, all ingame Aircraft are supercharged. (Who even started all of these myths?). Some Aircraft can change the Ratios at which the Supercharger Spins in Relation to Engine RPM. 

That is what most people call "Shifting the Supercharger", "Switching the Supercharger on" and whatever else NONSENSICAL, MISLEADING terminology they come up with. 

 

Switching it to a higher Speed simply means it CAN deliver more Air at the expense of Power. All excess air is just blown off through the Wastegate Valve. 

The Amount of Power the Supercharger requires is constant at a constant RPM. Running it at high RPM eats more Power than it does at low RPM. 

If you Switch up too early you just produce a lot of excess Pressure for NOTHING. 

 

No, the Point to shift is NOT when MAP starts dropping. Imagine your Altitude as a X Axis and your Power on the Y-Axis. Per Supercharger Gear you have a distinctive Power Curve. Peak Power is created at FTH for each Gear. 

For example: A Theoretical Engine Produces 

• 1st Gear: 1000hp at 0m; 1100hp at 1000m; 1200hp at 2000 (FTH, now MAP drops); 1000hp at 3000; 800hp at 4000m
• 2nd Gear: 700hp at 0m; 800hp at 1000m; 900hp at 2000m; 1000hp at 3000m; 1100hp at 4000m (FTH)
• Although MAP drops at 2000m, only when shifting at 3000m do you gain Power again. 

For example this Bristol Engine. The Shifting Point is where the Power Curves intersect. You can'T see that however on the MAP Gauge and have to trust the Manufacturers Data

 

 

 

I practically never use the supercharger (when there is one) on any plane

 

Nobody said, that not all engines in the sim are supercharged or that the supercharger isn't running all the time, nor did anyone claim, that you should shift supercharger gear the moment MP starts to drop off. There is a certain calculated altitude (or rather: certain outside air pressure) where the benefits of using 2nd gear starts outweighing the extra power used.

You are fighting windmills here Klaus. Noone has misunderstood things the way you seem to think.

Why not leave supercharger at stage 2 all the time, since it doesnt have any effect at low alt?

 

Because it generates engine drag, which makes you slower

 

And yes, the Capslock are me Screaming Silently in Educational Anger. My Squadmate on TS was almost deafened by my angry Keyboard clackering.

Edited October 12, 2017 by 6./ZG26_Klaus-Mann

[Plurp]

If one could use level speed alone to compare to specs page of when to shift to stage 2, then:

 

Lagg-3:  Spec:  2500:  Close enough

 

Lagg-5:  Spec: 3500:  I did not get parity in speed until 4500.  Lagg-5 seems to suffer the worst if using the wrong gear:  (Ex. @ 300 m:  492 (1)  455 (2) )

 

Yak-1:  Spec:  2300:  2500 seems better

[6./ZG26_Klaus_Mann]

Imagine me like this:

 

If one could use level speed alone to compare to specs page of when to shift to stage 2, then:

 

Lagg-3:  Spec:  2500:  Close enough

 

Lagg-5:  Spec: 3500:  I did not get parity in speed until 4500.  Lagg-5 seems to suffer the worst if using the wrong gear:  (Ex. @ 300 m:  492 (1)  455 (2) )

 

Yak-1:  Spec:  2300:  2500 seems better

Exactly: You Sir are getting it Right. Although Yak and Lagg-3 are using the same Engine, so Shift Points are the same. 

 

Neither Gudkov nor Gorbunov were involved in the LaGG-3 M-82, and when it was renamed to La-5, it was just that, an La-5. Nobody except for People trying to look stupid call it a LaGG-5.

Edited October 12, 2017 by 6./ZG26_Klaus-Mann

[Plurp]

Yep, brain not engaged on the La-5

 

Lagg-3 and Yaks prolly closer to 2700-2750

[Venturi]

 

It's a different story with planes that have turbochargers, like the P-38 or P-47, because it uses exhaust gasses to drive a turbine that runs the compressor, thereby not stealing any power from the engine.

 

The turbocharger did not cause parasitic drag on the engine, yes --- however, it robbed the engine of most of the forward thrust from the gasses flowing from the exhaust manifolds (as the energy was used in spinning a turbine), which was very significant forward thrust indeed at high altitude. Additionally "throttle up" time when the throttle was pushed forwards, was prolonged when in turbocharger mode due to turbo lag. Unlike a supercharged aircraft, which should have immediate manifold pressure increase (like less than 1 second to full pressure). So it was not pure gain.

 

But the most important aspect of a turbo supercharger system was that it provided a very high critical altitude and a much wider optimal "altitude band", as well as much better fuel consumption at cruising speeds - all due to having variable turbine speeds based on engine throttle settings.

 

Both these American aircraft also retained the standard, very-effective, supercharger system for use at lower altitudes -- thereby bypassing the major difficulties with making supercharger gearing / staging optimal across all desirable altitude ranges from 12km down to ground level.

[ZachariasX]

Well, for THAT amount of shaft power you get at altitude by turbocharging, I‘d happily trade the exhaust stack jets for that.

 

Most people here judge aircraft mainly on just their abilty to Hartmann someone else out of the sky. In the real world, you actually have to be able to get there as well, and you have to go home. A turbocharger gives you much more options to deal with that. It is less relevant if you are tied to a certain „working altitude“ like the the P-51, then with optimal gearing of the supercharger you get a good solution. Else, technically, you cannot compete with a turbocharged engine.

 

How different flying is with only supercharged engines vs. turbocharged, you see in comparing the Lockheed Constellation with the Boeing 377. They also feel like a Yak1 vs a P-47. And you can see that the option of maintaining an economic cruise at FL280 is indeed a game changer.

 

With the turbocharger you can also improve fuel economy lower down on cruise flight. You can waste hot exhaust gases or you can turn them into power or range.

[Finkeren]

The thing about adding a turbocharger to your design is ofc that it takes up space inside the airframe and adds weight. It makes comparatively less of a difference on a large, heavy aircraft like a P-38 or P-47, but in a tiny Yak or MiG fighter?

[ZachariasX]

The thing about adding a turbocharger to your design is ofc that it takes up space inside the airframe and adds weight. It makes comparatively less of a difference on a large, heavy aircraft like a P-38 or P-47, but in a tiny Yak or MiG fighter?

They are not so heavy, but indeed the early ones are rather big, making them unsuitable for the little hotrods. My point was more that supercharging does things other than just „also compressing air“.

 

The benefits are such that the US had a real fetish for them. As they couldn‘t put them in the small planes, they just dropped any second stage compression allthogether. Not having developed any intercooler system, they replaced it with nothing and you got those single gear, single stage hill-huggers like the P-40 and P-39, or simple two gear systems like in the Wildcat or the Corsair.

[-TBC-AeroAce]

Interesting to know, I generally switch when the Mc drops a beat. Stupid auto correct"mp drops a bit"

Edited October 13, 2017 by AeroAce

[JtD]

Not having developed any intercooler system, they replaced it with nothing and you got those single gear, single stage hill-huggers like the P-40 and P-39, or simple two gear systems like in the Wildcat or the Corsair.

The R-2800-8 (and 10) as used on the Corsair (and Hellcat) were actually two stage supercharged engines. Both had a permanently coupled main stage, and auxiliary stage that could be in neutral (off), low or high gear. Basically a three speed two stage supercharger. They also used intercooling.

 

It should also be mentioned that several of the US aircraft, such as the P-38 used two stage turbo-supercharging combos, also with intercoolers.

[Venturi]

The US Navy insisted on two-stage superchargers, even for its earliest aircraft (Wildcat, etc).

 

The specific service arm dictated the engine performance requirements, the time before overhaul, the range of power conditions and the time limit for each -- pretty much everything about the engine was dictated by the service arm. The US Army's doctrine was based on super-turbocharging, because its bombers were super-turbocharged.

 

And pre-war doctrine was "the bomber will always get through". The US Army had very little regard for fighter aircraft performance at the highest doctrinal levels in the early war period. Even afterwards, its focus on fighter aircraft was primarily centered on how those fighters could protect the arm of the Air Force which really mattered- the bombers.

 

However, pilots themselves did not see it that way, and every pilot wanted to be a fighter pilot. Something that has rarely changed regardless of the specific year...

The P-38 was perhaps the most innovative aircraft of the second world war from a technical point of view. Its chief designer, Kelly Johnson, later went on to design some of the most famous and technically demanding aircraft of the cold war, including the SR-71 Blackbird.

[ZachariasX]

Yes, I got that wrong about the Corsair, looking through through its flight manual. Manual gear shift. 1 N 2.

 

The P-38 was custom tailored to fit the supercargers (hence its unusual design) and in the P-47 they found the space. They also found space in their bombers, owing much to the rather remarkable performance they had.

 

Still, the P-39 and the P-40 had to make without intended second stage.

 

What I find remarkable is that the compressor and/or turbocharger produce as much or high up much more power than the pistons in the engine block. In a P-47, the turbocharger gives you up to 4 times the power of the radial high up. And once you are good at making compressor turbines, you‘re nearly there building a gas turbine. Dumping the whole engine block after the radial compressor, you just make that burn the fuel and send the gases through the exhaust turbine, powering the intake compressor. Voilà, you have a RR Ghost turbine.