Discrepancies from manual to modeling ingame , all kind of planes

[LonesomeRanger]

Hi,

we (me and some other forum members) noticed some discrepancies reading up on the actual (translated) manual for the Yak1 and I think it´s a good idea to discuss it here. Manual statements are underlined. Current in game modeling in orange

 

first regarding the maximum/recommended temperatures:

 

Oil temperature:

Max: 110°C

Recommended:90°C-100°C

In game the overheat warning comes at 115°C

Water temperature:

Max: 110°C for 10 minutes

Recommended: 90°C-100°C

In game the overheat warning comes at 115°C and you can fly indefinitely with 110°C

 

second regarding dive:

 

92. The dive must be made starting with a twist or a half roll to prevent the fall of oil pressure. It allows for any dive angle, reaching the output speed of 650 km / h by the indicator. During the dive disallow propeller overrev above 2800 rpm

 

no.1 discrepancy:
I noticed test flying : going negative g , the oil pressure never drops until red-out, engine seems to go off though , shouldn’t the pressure go down and if kept going negative g shouldn’t the pressure drop too far and the engine take damage? i know the German manuals say it was forbidden to do prolonged inverted flights , as the oil pressure would fail and could damage the engine. (This is something that is just not modeled in game per se for all models)

 

no.2 discrepancy:

dive limit according to manual is 650 km/h , in game damage occurs at around 740 km/h , that’s a pretty big safety margin modeled in game , especially if you look at the FW190 ,which has a dive limit of 850 (also according to manual) and starts taking damage at around 880 km/h... theres no doubt a safety-margin in the manual limits , question is how high? it is known that testflights did often show higher possible divespeeds.yet divespeed-limits in manuals are there for a reason. 

 

no.3 discrepancy:

the manual talks about not allowing rpm more than 2800 rpm in the dive, showing that the governor could not control the speed of the prop over certain airspeeds , in game the governor is nailed at 2700 rpm and does not overrev. This is also true for the FW190 , which goes up to maximum emergency rpm and stays there.it was common practice to throttle back at dives as to not overran the engine. This is not correctly modeled in game.

 

 

We would like to compose reports regarding those matters  or at least post these questions to developers. We would like to invite you to please share documents and flight reports here, in favor or against the points made and also discuss these matters.

[Hutzlipuh]

Quick search for FW190 numbers/tests:

 

http://www.wwiiaircraftperformance.org/fw190/fw190-0022-dive.html

http://www.shockwaveproductions.com/store/fw190/tactical_trials.htm <talks about achieved dive speed of  580 mph / 934 km/h ...and that with a captured aircraft.....

 

 

Quick search for 109 dive tests:

http://www.wwiiaircraftperformance.org/me109/me109g.html <- tas reached 906 km/h

also : http://www.wwiiaircraftperformance.org/me109/Me_109_Dive_Test.pdf <german document

http://www.wwiiaircraftperformance.org/me109/Diving_Test_109F_W.Nr.9228_ger_eng.pdf 109F with 109G wings ?

 

Quick search for the Macchi 202 :

 

Wikipedia article excerpt: "On 21 August 1941, Tenente Giulio Reiner, one of the most skillful and experienced pilots of 9° Gruppo, flew the "military control flight" in Lonate Pozzolo, The Ufficio tecnico (Technical Bureau) recorded the maximum speed of 1,078.27 km/h in the Folgore in a vertical dive, with 5.8 G. forces while pulling out of the dive. Ingegner Mario Castoldi, the designer of the 202 questioned whether Reiner had properly flown the test. In fact, during the vertical dive, Reiner had to face very strong vibrations throughout the airframe and in the control stick, while the flying controls were locked and the propeller blades were jammed at maximum pitch. The clean aerodynamics offered by the inline engine permitted dive speeds high enough for pilots to encounter the then-unknown phenomenon of compressibility.["   YEAH I KNOW ITS WIKIPEDIA , but the story has to come from somewhere....

 

...sadly not much more found regarding documents for the MC202

 

YAK1,LA5,LaGG3,I16 -> not much to find other then ususal wikipedia stuff, other games wikis....and my kyrillic isnt really good , so would someone please step up for that?

 

 

Edit: As far as i know regarding the propellor-governor system on the YAK1 (ser.69), it was a license-built Hamilton-Standard RPM-Control and the ViSH-61P blades were adjustable from 20-35 deg and therefor needed a pitch lever  . The ViSH-105SV of the Yak-1b was a similar design....so no CONSTANT SPEED PROP as many think,only a CSU(Constant Speed Unit/rpm-controller)...as aPilot you had to therefor adjust the proppitch according to flightspeed , rpm and altitude....NOT MODELED INGAME

 

Regarding Temperature and Complex engine managment , my opinion is that this game is lacking sadly in this regard , also the overheat issue with the YAK is known already, cant remember where i read about it....

Edited March 22, 2017 by Hutzlipuh

[19//Moach]

you mentioned oil temps and pressures

 

 

with experience in aircraft by the extraordinarily detailed A2A simulations (particularly their wonderful P51 for FSX) - I have learned every good pilot's habit to turn to the oil pressure gauge as soon as the engine starts puffing -- and then I have noticed that as far as this sim goes, that game is not much more than decorative....

 

temperatures have no visible impact on oil pressure (it should be higher when cold, which is the real reason why warm-ups are necessary - and overcooling is dangerous)

 

pressure will also not change, even with damage to the engine and oil found abundantly over the windshield and a suspicious black trail behind the aircraft...

 

even when lubrication fails completely, and oil temperatures are observed to be near ambient on the cooler, and past boiling point on the engine (visible on the IL2, which has separate engine and cooler oil temp gaiges) -- this is the telltale sign you're five seconds from learning the joys of glider flying - yet there is no visible change in pressure - it only drops off once the engine stops running completely

 

in effect - that gauge is not more than a "is my engine running?" indicator.... alas, this leaves us dependent on not-very-realistic technochat as the only means to determine the presence engine damage....

 

 

the fuel pressure gauge seems to function more as expected, and can be noticed going down as fuel makes the undesirable transition from "resource" to "memory"

 

 

 

 

as for the comment on the constant speed prop - I understood what you were saying there about the ViSH-105SV design, but any prop which has a constant-speed-unit fitted is by definition a constant speed propeller -- I reckon you were thinking of  a "variable pitch propeller" there - which is a design in which the pilot has to adjust the blade angles manually to maintain RPM (like the early 109s)

 

propeller pitch is a part of propeller rpm control - but a prop pitch lever does not imply it sets a constant rpm....

 

 

propeller technology evolution goes:   fixed-pitch → variable-pitch → constant-speed   

 

the difference between the latter two being the presence of a governor, (either hydramatic or electric) which adjusts prop pitch to maintain a maximum rpm set by the pilot, hence a "CSU" - as opposed to the pilot doing that job by adjusting the pitch himself as he flies with the simpler "variable pitch" design

 

 

 

 

another note on engine temperature management in game -- all engines will currently overcool when idling on the ground - contrary to several manuals and accounts which specifically state "take off or shut it down, else it'll boil" in some way or another

 

the dangerously weak brakes on all planes we have in the sim are incapable to holding a plane stopped at the power levels required for actually warming up an engine, even with radiators closed in a hot(ish) day

Edited March 22, 2017 by 19//Moach

[Hutzlipuh]

 

 

as for the comment on the constant speed prop - I understood what you were saying there about the ViSH-105SV design, but any prop which has a constant-speed-unit fitted is by definition a constant speed propeller -- I reckon you were thinking of  a "variable pitch propeller" there - which is a design in which the pilot has to adjust the blade angles manually to maintain RPM (like the early 109s)

 

propeller pitch is a part of propeller rpm control - but a prop pitch lever does not imply it sets a constant rpm....

 

 

propeller technology evolution goes:   fixed-pitch → variable-pitch → constant-speed   

 

the difference between the latter two being the presence of a governor, (either hydramatic or electric) which adjusts prop pitch to maintain a maximum rpm set by the pilot, hence a "CSU" - as opposed to the pilot doing that job by adjusting the pitch himself as he flies with the simpler "variable pitch" design

 

 the YAK manual also clearly shows there was a proppitch-lever present,if you have a governor why have a seperate proppitch-lever?.read it up please

 

also what do you think about the governor not being able to keep rpm above certain airspeeds? ingame fixed at the selected rpm and not going over maximum (in case of YAK 2700 rpm)

[=TBAS=Sshadow14]

Max Dive speed heavily based on Altitude, Map Air density/Pressure and Temperature

a plane with dive limit of 800kph on deck Will never reach that speed @ 3,000m it will brake apart up there around 750kph

[19//Moach]

 the YAK manual also clearly shows there was a proppitch-lever present,if you have a governor why have a seperate proppitch-lever?.read it up please

 

also what do you think about the governor not being able to keep rpm above certain airspeeds? ingame fixed at the selected rpm and not going over maximum (in case of YAK 2700 rpm)

 

 

the terms prop pitch and prop rpm are often used mixedly in flight simulators - for instance, il2 correctly names the control "prop rpm" while fsx has it labelled "prop pitch" - regardless of whether the aircraft has a variable pitch or constant speed propeller

 

I was not disputing your claim about the yak, anyways - though I think we would all like to see what sources you have for what you claim (I'm simply curious, as I find this stuff fascinating)

if you could provide us a link, that'd be awesome

 

my comment was really about the way you had it phrased, in which you said "no constant speed prop, only a CSU" - which is really a self contradicting statement - but reading the rest of what you said, it was clear enough that you had meant "no constant speed, only variable pitch" - and that was the only thing I pointed out...

 

 

it was all about terminology, since this is almost the aviation equivalent of, and often times about as coherently employed as, the "how's a motor unlike an engine" debate (if motors are just electric, why do we have "motorsports" and "why is detroit called motor city"... it goes on and on)

 

 

 

if what you say is true - then indeed, it's a rather major discrepancy from the real life plane that we have in the sim

[LonesomeRanger]

Max Dive speed heavily based on Altitude, Map Air density/Pressure and Temperature

 

The plane does not break apart b/c of the speed, but because of air resistance.

 

 

 

a plane with dive limit of 800kph on deck Will never reach that speed @ 3,000m it will brake apart up there around 750kph

 

so what you say does not make sense at all.

 

That air resistance is kept constant in the indicated speed, which you are talking about as I presume. I am sure the engineers tested with indicated speed, otherwise they would need to give different limits for different altitudes/temperatures... and that would not make sense at all. So no matter what the plane should fall apart when the indicator reads 650 km/h.

Edited March 23, 2017 by LonesomeRanger

[-=PHX=-SuperEtendard]

About the safety margin and the manual limit, in another thread someone asked for the P-39 limit:

 

"The maximum permissible diving speed is 523 miles per hour (842 km/h). 475 mph (764 km/h) is the maximum recommended indicated air speed"

 

 

Manual here: https://es.scribd.com/document/61806618/Pilot-Flight-Manual-for-the-P-39K-L

 

So around 80 km/h safety for the P-39, we should find some similar statement in a document/test report for the Yak-LaGG etc. And ideally in IAS ... it isn't the same doing 900 km/h true air speed at 5000 meters than at 2000 meters.

Edited March 23, 2017 by -=PHX=-SuperEtendard

[unreasonable]

 the YAK manual also clearly shows there was a proppitch-lever present,if you have a governor why have a seperate proppitch-lever?.read it up please

 

also what do you think about the governor not being able to keep rpm above certain airspeeds? ingame fixed at the selected rpm and not going over maximum (in case of YAK 2700 rpm)

 

Are you a Russian speaker? You should think about what you are claiming here: that a group of Russian aero-geeks reading Russian documents about a Russian plane cannot tell the difference between an RPM governor and a variable pitch control. 

 

Please post the specific wording, preferably in Russian,  that you think indicates that the Yak has a variable pitch control only and not an RPM control. I have read it up, also the Stephanets paper (in Google Translation) 'How to Fly the Yak" and I disagree with your conclusion, which I think is based on terminology perhaps made unclear by translation: I agree with Moach on this.  All of the wording in both documents is consistent with the use of the control to adjust RPM - not prop pitch.  edit - and there is nothing about the need to adjust the control at different speeds, which would be necessary if this was a pitch control rather than an rpm control. Indeed, the pilot is encouraged to put the rpm control to maximum and leave it there, in almost all circumstances except economy cruise.

 

 

 

no.3 discrepancy:

the manual talks about not allowing rpm more than 2800 rpm in the dive, showing that the governor could not control the speed of the prop over certain airspeeds , in game the governor is nailed at 2700 rpm and does not overrev. This is also true for the FW190 , which goes up to maximum emergency rpm and stays there.it was common practice to throttle back at dives as to not overran the engine. This is not correctly modeled in game.

 

 

Just a detail here - the governor stays at 2700 rpm if it is at maximum when you enter a dive. If you have it below - say 2600 - enter the dive, and then move it to maximum, it will blip up to 2800 and then settle back at 2700. But I could never make it go over 2800, so I agree this seems odd. edit - since overspeeding a CSU can only happen above a certain airspeed once the prop is at maximum coarse position, perhaps the difference between this speed and the "death-speed" ie terminal structural damage is so small that it was not worth designing in - just speculation. Certainly worth asking Han why the CSU does not overspeed in a fast dive.

Edited March 23, 2017 by unreasonable

[Dakpilot]

If you look at FM claim No.10 in here, Stickied at top of this section

 

https://forum.il2sturmovik.com/topic/11664-fm-claims-respond/

 

There is an answer/mention about Lagg-3 and Bf 109 dive limits and reasons, it may have relevance also to Yak-1 and reasons for limits

 

am fairly sure the Yak-1 dive limits comparing  the pilot's operating handbook recommendations vs RL test results have been discussed before, somewhere by Dev's a few times, just do not remember where/when

 

Cheers Dakpilot

[Hutzlipuh]

Excerpts fomr the translated INSTRUCTIONS FOR THE PILOTS ABOUT THE USE AND FLIGHT TECHNIQUES OF THE YAK-1, YAK-7, YAK-9 WITH M-105P, M-105PA Y M-105PF ENGINES Third edition
Military Edition
People's Commissariat of Defense
Moscow, 1944
Instruction developed by: Major Engineer STEPANETS Major PROSHAKOV Major Engineer POLITIKIN:

 

35. Reduce the throttle up to 2400 rpm and test the performance of the propeller and the speed controller R-7; for that, change the propeller pitch fine to coarse, and vice versa. During the winter, to warm the oil within the group of cylinders propeller must make 2 to 3 changes of propeller pitch; then place the command (either rotary or lever) fully forward.

 

51. Check the position of the mixture lever, fuel valve and control (rotary or lever) of the prop pitch.

 

71. To pass from climb to level flight, you should follow the following sequence: a) with the throttle set the flight speed to at least 250 km / h for all altitudes; b) by the prop pitch control (rotary or lever) set the corresponding revs to the speed; If after putting coarse pitch propeller, the speed varies, adjust it to the desired speed using the throttle.

 

Why does the manual clearly differntiate between RPM-Control (R7) and pitch-control (fine/coarse)?

 

EDIT: yeah it could be possible that there is some translation error... but then the translator could not differnitate between proppitch and rpm-control , two completely seperate words.

Edited March 23, 2017 by Hutzlipuh

[unreasonable]

Well I am looking at this:

 

12. Check the engine operation: a) the correct movement of the throttle; b) position of the control lever mixture (fully backward); c) position of the change lever of the supercharger (must be put in first stage); d) position of the prop pitch control (rotary or lever) (fully forward); d) water and oil radiators must be closed.

 

ie there is only one propeller control.  The question is is it a CSU or variable pitch unit, and the problem is that we are looking at translations.

 

You can also look at Stepanet's guide and read this:  " At Yak installed variable pitch screw centrifugal speed regulator. Available in the cockpit control knob allows you to without touching the throttle, change the momentum in a very wide range. This was done in order to be able to: "

 

You can read how the centrifugal system was used in early CSUs here https://en.wikipedia.org/wiki/Constant-speed_propeller

 

Or you could just assume that the developer's mistakes are unlikely to be this glaring. Or just email Han and ask him.

 

Failing all that, you could splash out and buy one: http://www.yakuk.com/aircraft/yak-1/

[19//Moach]

At Yak installed variable pitch screw centrifugal speed regulator. 

 

 

that is another way of saying "propeller governor" - aka:  constant speed unit

 

which is what it has in the game....

 

 

I would more likely suppose something got lost in translation than that our Yak would have such a fundamental inaccuracy implemented... it's a simpler, more likely explanation, I reckon 

[Brano]

This thread is shiny example of what happens when someone tries to argue on CFS forum using english translation of spanish translation of russian handbook :D

[unreasonable]

Perhaps if we took those quotations and Google translated them back into spanish, then from spanish to russian, and then gave them to a russian speaker and asked him to just post a  for CSU and a  for variable pitch unit....

 

Unfortunate for the OP - I would actually quite like to know if, or when, the CSU could over-rev beyond 2800 - on the face of it that does look like a genuine manual/game discrepancy, but I have no idea if it is material.

 

All the others seem simply to reflect that the engine management model is a bit simplified with various ad-hoc adjustments to safety limits, as we already knew.

[BlitzPig_EL]

Any constant speed prop unit has a fixed range in which the blades are able to move.

 

Under most flight conditions the range that the unit controls the blades in, is adequate to maintain the pilot's selected RPM, however, if you dive the aircraft, it is possible that you can attain speeds that are beyond the range of the CSU to compensate for.

That will require you to pull back on the throttle to maintain safe RPM limits, and even at that if you have an airframe strong enough, you may still exceed the engine's or propeller gear box's maximum limits.  This is no doubt what happened in the famous Spitfire dive test when the aircraft in question lost it's prop in a prolonged high speed dive.

 

Our in game P 40 E will do this, as it's Curtiss Electric Propeller eventually runs out of adjustment range, and you must throttle back to save the engine, the P 40 being very good in the dive.

 

Guys, this is all very basic stuff here, there is no magic in the operation of constant speed props, either the hydraulic ones of the Hamilton Standard type, like many allied aircraft used, including the Yak, or the electric type used by Curtiss on the P40s and also on the P38.   Or similar units on the German aircraft.  Exceptions being the manual pitch on early 109s, and various 2 speed units as used on early Spits, Hurris, the SM tri motors, and various early Japanese aircraft.

 

It is interesting that the Curtiss Electric unit can be used either way, as a fully automatic prop rpm control, or as a manual prop control, like the early 109s.

 

But, none the less, this isn't rocket science or an attempt to somehow "buff" the performance of the Yak, or to "nerf" it either.

It's just how Constant Speed Props work in the real world.

 

Which is how we want them to work in the sim, yes?

Edited March 23, 2017 by BlitzPig_EL

[JtD]

It's possible to over-rev the M105 in the Yak if you dive it from high altitude, preferably at full power. The constant speed unit will try to regulate rpm, but it will reach the upper end of the pitch range, and the engine will blow.

[unreasonable]

@BlitzPig  

 

Of course - the question is why is it not possible to overspeed the Yak 1 CSU in a fast dive in the game, while warning not to exceed 2800 in the manual. Perhaps it does overspeed eventually - but when I tried several times from 6000m the rpm was still at 2700 as I hit the ground with no control surfaces.

 

I have no idea what is the right answer.

 

edit - just seen JtD's answer - that is not what I found in my tests.

 

edit. until I tested again, differently - see below.

Edited March 23, 2017 by unreasonable

[BlitzPig_EL]

unreasonable, I realize you understand how a CSP works. 

 

However there are a lot of people that don't grasp it, and i think a lot of that is trying to equate the relationship between the throttle lever and prop lever, to the accelerator and transmission in their automobile.  It really doesn't work that way, as you know, unless you have one of the perfectly awful CVT equipped cars, where it sort of works that way, kind of.   But the best thing for any new person to flight sims to do is stop thinking in terms of their automobile, and just learn how airplanes do things.  We were all there at one point.

[unreasonable]

@BlitzPig   - I "sort of" know how it works... 

 

Further to JtD's point, since he is not often wrong, I went and checked again, this time on the Winter map. Two or three tries and I got the behaviour he describes - a sudden erratic movement of the rpm over 2800 right upto the stops.

 

What was odd was that this was in a vertical dive but happened at a much lower speed than my previous test where the rpm was steady, ie well before any damage to ailerons. But in this case I put the plane into the dive far more abruptly - seems it was acceleration rather than airspeed as such that causes the rpm overspeed. Again no idea if that is correct, but it is certainly possible to overspeed the prop in a dive in a Yak, so the OP has his answer.

 

Will produce film if anyone really wants it. Sure I have some music I can use somewhere. 

[JtD]

edit - just seen JtD's answer - that is not what I found in my tests.

The pitch limit will be reached at about 900km/h TAS, meaning you need to reach the IAS dive limit of 700some at altitudes of more than 6000m. It's not relevant for any realistic air combat scenario, but testing confirms it is there.

 

It is most easily observed if you dive a Yak from 10000m and set pitch to 0% - you'll see the rpm creep up until they exceed 2700rpm, meaning that first you reach the regulation range limit causing rpm to creep up until the prop limit will cause the engine limit to be exceeded.

Edited March 23, 2017 by JtD

[BlitzPig_EL]

Well, at least we won't have this discussion about the Grumman F4F, it was so draggy that it didn't really have a Vne.

 

[=EXPEND=13SchwarzeHand]

 Cheers Dakpilot, that´s very helpfull

 

 

 

Posted Today, 07:00 If you look at FM claim No.10 in here, Stickied at top of this section https://forum.il2stu...claims-respond/ There is an answer/mention about Lagg-3 and Bf 109 dive limits and reasons, it may have relevance also to Yak-1 and reasons for limits

 

So we have:

 

Plane               vne IAS according to manual         according to rl tests        in game(diff)
Lagg-3             600                                                 700                                 750 (150)
Bf 109              750                                                 ???                                 850 (100)
Yak1 ser 69      650                                                ???                                 720 (70)

 

Seems coherent to me.

Edited March 23, 2017 by II/JG17_SchwarzeDreizehn

[Hutzlipuh]

Of course - the question is why is it not possible to overspeed the Yak 1 CSU in a fast dive in the game, while warning not to exceed 2800 in the manual. Perhaps it does overspeed eventually - but when I tried several times from 6000m the rpm was still at 2700 as I hit the ground with no control surfaces.

 

What bothers me is that there is in the same manual the 650 km/h dive limit and the 2800 rpm-limit which one shouldnt overgo.... so maybe then over-revving was in relation to both numbers? i think there are those numbers in the manual for a reason (e.g. end of contollable pitch,be it a csp or not)

dont forget yak was built with around 600 km,/h in mind , so the designers obviously laid out the controllable range for the prop in the same region (with some safety margin of course)...no point in laying the range for the pitch much higher,since the plane couldnt reach higher speed with engine power alone and also couldnt stay in higher regions for prolongued time

Edited March 23, 2017 by Hutzlipuh

[LonesomeRanger]

Thank you guys, that answered a lot of question