[CLOSED] Climb rate appears to be to high, even for 109k

[javelina1]

3400 KG, ie. 100% guns and fuel

full power and MW WEP on (1.8ata manifold pressure, 2800 rpm)

 

Radiators roughly 2/3s open up to 6-7 km.

Above rated altitude (7500) coolant radiators gradually closing, reaching 1/4 open at ceiling (probably could be done on AUTO?)

 

This is the condition the figures on the chart represent.

 

Climb at roughly 270 kph IAS.

 

Thanks Kurfurst. Later today, I'm going to try this. (OP - thanks for asking the clarification).

[rel4y]

If I read correctly the time estimation is for 1.45 ATA Steig und Kampfleistung.

 

I just tested 4 times with 1.8 ATA + MW50 Sondernotleistung, starting at approx. 20 m above MSL, ending 7500m MSL, 100% fuel & ammo, starting speed ~300 km/h, 20° C temperature and no weather effects set on the map. I measured twice with rads set to auto and twice with rads fully open.

 

rads auto: 347s, 345s -> 21.6 m/s

rads fully open: 383s, 382s -> 19.6 m/s

 

I tried to keep it in the speed range of 270-280 km/h and the ball always centered.

 

I also just tested once 1.45 ATA, rads fully open, everything else exactly as above.

 

550s -> 13.6 m/s

 

That corresponds pretty well to the graph. The data shown on the graph give a heigth estimation of about 7700-7800m after 550s climb time. Keep in mind though I used fully opened rads, started at ~300 km/h and I cant tell if the normal or the thin blade prop were used for this graph.

 

Im very interested in other results. I would not yet draw conclusions with my tests alone

 

Edit: Sometimes Im just stupid.. The props perform the same until FTH is reached, that is why I measured to 7500m in the first place.

Edited December 27, 2015 by rel4y

[ArkRoyal]

In game right now the 109 climbs at about 25m/s (5000ft/min) at max fuel and ammo etc. It should be around 22.5m/s (4400fpm). It has been this way for a long time. When it was first released, it climbed at around 6000ft/min.

 

What I think is interesting here is that we somehow have a 109k that is too slow, but climbs to fast.

[rel4y]

Last test for today: rads 2/3rds open 499s -> avg. to 7500m 15 m/s

 

In game right now the 109 climbs at about 25m/s (5000ft/min) at max fuel and ammo etc. It should be around 22.5m/s (4400fpm). It has been this way for a long time. When it was first released, it climbed at around 6000ft/min.

 

What I think is interesting here is that we somehow have a 109k that is too slow, but climbs to fast.

Actually I cant confirm that atm. Took me 8 min 19 s to 7500m with rads 2/3rds open. The chart would suggest 7200m altitude. Others may fly smoother and therefore climb better than I do, but in my last test at 1.45 ATA the K4 seems to overclimb only marginally compared to the chart.
Edited December 27, 2015 by rel4y

[ArkRoyal]

Last test for today: rads 2/3rds open 499s -> avg. to 7500m 15 m/s

 

Actually I cant confirm that atm. Took me 8 min 19 s to 7500m with rads 2/3rds open. The chart would suggest 7200m altitude. Others may fly smoother and therefore climb better than I do, but in my last test at 1.45 ATA the K4 seems to overclimb only marginally compared to the chart. Again I have no knowledge of the prop used for it.

 

Your measure average climb rate if I'm reading your posts right. The problem with the flight model is climb rate at specific altitudes. Around sea level to 7000ft, to be precise.

 

To do a climb test, maintain a constant speed of 300kmh IAS up to 7k. Use tacview or the in-game vario-meter to check the climb rate at different points.

[rel4y]

Your measure average climb rate if I'm reading your posts right. The problem with the flight model is climb rate at specific altitudes. Around sea level to 7000ft, to be precise.

 

To do a climb test, maintain a constant speed of 300kmh IAS up to 7k. Use tacview or the in-game vario-meter to check the climb rate at different points.

 

Yes I simply calculated average climb rates. Can you tell me at which altitude it is overclimbing by 2,5 m/s? Tomorrow I will then test on said altitude in more detail. I sadly dont own TacView.

 

Edit: Sorry I misread your post. I will test from 0 - 7000ft.

[javelina1]

Sorry, don't have TacView either....

 

A quick and dirty test. Takeoff from Nellis. (Flying DCS 2.0). kept my crate level at 20 meters above the deck, close to 300kph. Set the rads & PPC to auto, and then punched it to 1.8 ATA.

 

Tried to keep her at 300kph, but I varied in speed from 240-280kph. (Not such a good pilot yet). :-) Went up to 3000 meters, and I calculated an approx. climb rate of just around 19 m/s.

 

Need to practice my ideal climb rate, and will try again, (using DCS 1.5) and fly out from a sea level airstrip there.

[rel4y]

Alright I think ArkRoyal has a point. Although I cannot reproduce a figure of 25 m/s I consistently measure 23.8 m/s (6 different testruns) climbrate with rads at 2/3rds, 1.8 ATA MW50 engaged between 1000 m and 2000 m altitude. I started several times at 1000 m and 1500 m and measured the time for 500m climb, when starting at 1000 m I also measured the time to 2000 m. Ball was centered, speed 300 +-5 km/h.

 

For 500 m to 1000 m I measured consistenly somewhere in between 20-21 s. That would roughly equate to 24.4 m/s climbrate. These are all handtaken ballbark figures and no exact science, but interesting nontheless. Since I am done packing up my stuff I can test some more tonight. Tomorrow I will leave for vacation anyway. :)

 

Edit: Thanks javelina1 for your efforts. Try making a mission with standard parameters no weather effects, air start, fuel and ammo at 100% and start off at sea level. Then setting the radiators to be just about parallel (=~2/3rds open), bleed off excess speed and go on from there with the desired ATA setting. Good luck!

Edited December 26, 2015 by rel4y

[javelina1]

rel4y,

 

Flying DCS 1.5. Set a mission for 20m above the sea level. Had the Rad's at auto, (same with the PPC). 100% fuel and ammo. Stabilized speed at 300kph (level), and then put the hammer down at 1.8 ATA.

 

Climbed from 50m to 3050m, and had a climb rate of 24.39 m/s.

 

cheers,

 

-Jav

[Echo38]

Stabilized speed at 300kph (level), and then put the hammer down at 1.8 ATA.

Climbed from 50m to 3050m, and had a climb rate of 24.39 m/s.

 

This brings back some old memories. I recall, perhaps ten years ago, on another forum, a discussion on climb rate methods. If I remember well, the consensus was that USAAF and Luftwaffe climb test methods differed significantly. Something like: USAAF procedure was measured from takeoff, while Luftwaffe procedure was more similar to what you describe. But, that's just my recollection, from memory, of hearsay.

 

Before we can determine whether or not the 109 is over-climbing, I think, it would first be necessary to definitely settle this issue of climb rate procedure, with appropriate documentation. It would affect the results largely, of course, if it were not being properly accounted for. Hopefully, I'm "late to the party," with this already discussed & concluded in one of the recent threads on the subject, but I don't see anything about it in this one. I would assume that Yo-Yo knows about this issue, because he is far more knowledgeable on the entire subject than I am; however, it is still worth confirming that this has been accounted for.

 

Hmm. I wonder what those little "hooks" at the bottom of that climb rate graph mean ... the temporary spikes in climb rate from sea level to 1000m. I can't tell if that's the climb rate rising as the pilot pulls back on the stick, before peak sustained climb rate is established? Surely it doesn't take 1000m for that to happen, though. Is it, instead, that the test was begun at wheels-up, after all, and the spike is the result of going from takeoff speed to best climb speed, before starting to naturally drop as altitude is gained? Puzzling.

Edited December 28, 2015 by Echo38

[Kurfürst]

Hmm. I wonder what those little "hooks" at the bottom of that climb rate graph mean ... the temporary spikes in climb rate from sea level to 1000m. I can't tell if that's the climb rate rising as the pilot pulls back on the stick, before peak sustained climb rate is established? Surely it doesn't take 1000m for that to happen, though. Is it, instead, that the test was begun at wheels-up, after all, and the spike is the result of going from takeoff speed to best climb speed, before starting to naturally drop as altitude is gained? Puzzling.

 

There is no pilot, its a calculated climb rate. The little hook is simply the power spike of the engine, the output is 1850 PS at sea level but it increases a little after that. The climb rate just reflects the output characteristics of the engine.

[javelina1]

 

Before we can determine whether or not the 109 is over-climbing, I think, it would first be necessary to definitely settle this issue of climb rate procedure, with appropriate documentation. It would affect the results largely, of course, if it were not being properly accounted for.... .

 

Completely agree. We should follow a consistent process for the data collection. (FYI - just doing this for fun. I love the DCS 109, and hope everything is tuned to be as close to life as possible). :thumbup:

[VO101_MMaister]

There is no pilot, its a calculated climb rate. The little hook is simply the power spike of the engine, the output is 1850 PS at sea level but it increases a little after that. The climb rate just reflects the output characteristics of the engine.

 

And according to Yo-yo, the exhaust thrust's effect is probably not included in these calculations. Hence the ingame climb rate is slightly higher.

[Anatoli-Kagari9]

And according to Yo-yo, the exhaust thrust's effect is probably not included in these calculations. Hence the ingame climb rate is slightly higher.

 

 

I don't get it...

 

Are the charts based **only** in calculations, or also in RL measurements performed by test pilots ?

 

If based on tests performed by pilots flying the K4, then they already account for the ramjet effect, right ?

Edited December 28, 2015 by jcomm

[VO101_MMaister]

I don't get it...

 

Are the charts based **only** in calculations, or also in RL measurements performed by test pilots ?

 

If based on tests performed by pilots flying the K4, then they already account for the ramjet effect, right ?

 

As far as I know ( and it is purely based on information I have read on this forum) this sheet shows an engineer calculated benchmark of the k4's climb rate , and not actual test results. Yo-Yo checked this, and he claims that the ramjet effect was probably not taken into the formula, therefore the sheet shows a somewhat lower climb rate than what he calculated and used in the FM.

[Anatoli-Kagari9]

As far as I know ( and it is purely based on information I have read on this forum) this sheet shows an engineer calculated benchmark of the k4's climb rate , and not actual test results. Yo-Yo checked this, and he claims that the ramjet effect was probably not taken into the formula, therefore the sheet shows a somewhat lower climb rate than what he calculated and used in the FM.

 

Ah! Ok, understood, but still in doubt that engineer would forget about it ? ? ?

[Crumpp]

Yo-Yo proved Focke Wulf did not use exhaust thrust. I would not be surprised if Mtt also did not. Exhaust thrust wasn't much of a factor in aircraft designs until the late 1930's. An engine has to be powerful enough and have the correct exhaust design to realize its benefits.

 

The DB605 series had the right engineering to realize exhaust thrust gains. Knowing the difficulty faced in making a climb analysis, I wouldn't be surprised to find it was commonly left out on many World War II aircraft calculated climb performance analysis. That is why you see so many reports investigating its effects during the war. It was a new thing and everybody was experimenting and measuring its effect.

 

It is also a good way to ensure the customer who ordered the aircraft is happy with the finished product as your estimates will always be conservative.

[Crumpp]

What CAS is used for those tests ?

 

What should I use in DCS to run similar tests ? And, BTW, should I set fuel to 100% and guns to 100% ?

 

Thx!

 

Vw is True Airspeed

 

"W" stands for "wahre".

[Crumpp]

Compare the Mustang calculated climb performance with flight test at similar weights:

 

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

 

 

The flight testing performance is consistently better than the calculated climb performance.

[Hummingbird]

Compare the Mustang calculated climb performance with flight test at similar weights:

 

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

 

 

The flight testing performance is consistently better than the calculated climb performance.

 

Yes, it was a common theme, and it litterally was the case with pretty much every MTT, NA or FW AG calculation vs real flight test.

Edited December 29, 2015 by Hummingbird

[Anatoli-Kagari9]

Very interesting to learn that!

 

So, I can feel even more confident now with my climb rates in the K4 :-)

[Screamadelica]

Great thread.

I never stop learning with this sim and the wealth of knowledge on these forums is incredible. Thank you to everyone for all the information.

S! Scream.