Acceleration comparisons

[horseback]

Originally Posted by RPS69

I'am much more impressed by the LaGG66 acceleration, and having higher final speed. I think that some of this must be rechecked, and it would be a healthy thing to do.

Horseback, since you were on the WW view, you weren't checking the slip ball by chance? The higher the engine power, the more important it is.

Actually, I fly the test in cockpit mode and depend upon the depictions of the instruments to keep straight and level. I then watch the track in Wonder Woman because it allows me to obtain the precise altitude and TAS data which I record.

Part of what I'm trying to do is find the best way to fly accurately or get the best out of the aircraft as the average player with TIR and the usual array of controllers would, which is (partly) why I fly the tests in cockpit. In a lot of cases, there appears to be a sort of forced parallax, where the indicators don't align, particularly in the US type artificial horizons (and all of my photos and source material show no such parallax visible, either from the pilot's seat or even from shots taken just outside the cockpit). This tends to make it harder to keep your wings level when you're trying to hold the nose down until the elevator trim can be dialed in. Generally, the in-cockpit slip ball (or T&B needle in the case of British fighters) is at least slightly in conflict with the vector much of the time and the in-cockpit 'ball' is almost always in error versus the WW vector ball during any kind of change in direction or sudden power surges.

About the LaGG, I think that we have to take the altitude (approx 3000m) into account, as well as the fact that in-line engines are both more aerodynamically friendly and seem to 'rev up' more quickly. We also have to think about reputations; the later LaGGs were quite improved over the early models, but the pilots of the VVS appear to have lost faith in it the same way USAAF pilots in the Southwest Pacific lost faith in the Airacobra. At 3000m, the LaGG (66) may be closer to its best performance height than the La-5F and FN, as well as being a bit more aerodynamically refined.

I think that the results at 100m and 1500m will be quite different.

cheers

horseback

[Wea0versd]

I will be happy to answer questions or provide the charts showing direct comparisons of given types if I have tested them.

[gaunt1]

Thank you again Horseback!

Just going from IL-2 Compare graphs, at sea level, that's exactly what the difference is: about 20% without WEP on and 15,something% with it... admittedly, I haven't done any tests myself.

How can I check that? Is there an update/patch that adds acceleration graph? My version (4.11) has only summary, speed, rate of climb, ROC vs climb speed, turn time and fan plot.

[majorfailure]

Originally Posted by gaunt1

Thank you again Horseback!



How can I check that? Is there an update/patch that adds acceleration graph? My version (4.11) has only summary, speed, rate of climb, ROC vs climb speed, turn time and fan plot.

I think initial acceleration is roughly proportional to max RoC.

[MaxGunz]

I think initial acceleration is roughly proportional to max RoC.

As Far As I Can Tell Right Now:

As long as you can hold TAS steady, Ps = change in height / change in time.

And there's correction for when you can't that with 10/sec data rate from devicelink should be possible to get closely.

See equation 7.2 on page 14 of this PDF:
http://www.aviation.org.uk/docs/flig...-FTM108/c7.pdf

When change in TAS = 0, the correction factor goes away. A tiny change in TAS at low airspeed will make a small correction necessary.

Ps =dh/dt + VT / g * dVT / dt

where
d is "change in"
h is height
t is time
VT is TAS
g is gravity

dVT being change in TAS, if it is 0 then everything past dh/dt is 0

I have found close to steady IAS climbs to be easier to fly in IL2 than trying to keep level at full power from 200 kph to full speed.

Remember that Ps changes with both speed and alt. Whatever tests are run need to cover as much of the range as you want to chart. You don't have to get speed at every last kph or alt at every meter but the closer you get the smoother/more accurate your connect-the-data-dots curves will be.

That's as good as my NOT-AN-AE-SELF can do right now, the simple things.

[SadoMarxist]

Originally Posted by majorfailure

Quote:
Originally Posted by gaunt1 View Post
Thank you again Horseback!



How can I check that? Is there an update/patch that adds acceleration graph? My version (4.11) has only summary, speed, rate of climb, ROC vs climb speed, turn time and fan plot.

I think initial acceleration is roughly proportional to max RoC.

Exactly. The climb vs TAS diagram for a certain altitude also represents the Ps diagram for that altitude. To get the exact value of acceleration an aero plane can have in level flight at a certain altitude and airspeed multiply Ps value for said altitude and airspeed by gravitational acceleration and divide it by airspeed. Comparison of the ability of two aircraft to accelerate in level flight takes only a look at the ROC vs airspeed diagram in IL- 2 compare with the two aircraft selected: that which can out climb can also out accelerate. To express that in percents for a certain airspeed just calculate the percentage of advantage in ROC one aero plane holds over the other. Off course, we only have these diagrams available for sea level, but MaxGunz already explained this.

[MaxGunz]

I thought we only have them for 1000m.

But for many speeds at whatever alt we can compare FW accel to other planes *at the same speed*.

For the math challenged who can use the Windoze calculator, if you take the speed of the faster plane and divide by the speed of the slower plane then subtract 1 and multiply the result by 100 you will get the percent that the faster plane is faster.

640 / 620 = 1.032258064516129032258064516129

subtract 1 to get .032258064516129032258064516129

times 100 is 3.2258064516129032258064516129

640 is 3.2% faster than 620.

Comparing acceleration is the same way only it's acceleration, not speed.

Now repeat after me: The Sky Is Falling! The Sky Is Falling! It's A Conspiracy! The Sky Is Falling!