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SE5a FM - review & fixes!


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#41 hq_Reflected

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Posted 01 September 2011 - 06:54

Not anymore? That's great. Last time we had a discussion about this you did otherwise. Cool then.
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#42 MiG-77

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Posted 01 September 2011 - 08:29

Not anymore? That's great. Last time we had a discussion about this you did otherwise. Cool then.

That is why I retested all the planes in 1.015 and started that thread ;) So planes have been tested same way in my test from 1.015 to this day.
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#43 Rexmundi

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Posted 01 September 2011 - 09:32

How good is the auto pilot?

I wonder if it's worth making a mission whereby the AI does the flight testing, so that any one could down load the mission, change the plane in the editor, get the AI to fly it and record the numbers.

It may help with reproducibility, and it would (if the idea's feasible)give an independent base line all could agree on. A bench marking mission, if you like.
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#44 gavagai

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Posted 01 September 2011 - 09:47

Reflected, I also did my test from the point the wheels left the ground, and my results were a little faster than Mig-77's.
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#45 An.Petrovich

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Posted 01 September 2011 - 10:32

Hi guys,

Also, look here:

http://www.theaerodr...climb-rate.html" onclick="window.open(this.href);return false;">http://www.theaerodr...com/forum/aircr … -rate.html

Viper:

Various test reports summarized by J. M. Bruce (Aeroplane Monthly, Nov 1977) …
Thank you for info!
However, the data is a bit uneven,
is it possible to get this source?..

Not the Viper, but:

Hi Reflected,
British Aeroplanes, 1914-1918, by J.M.Bruce, page 455 Performance table …

Yes, I have this source:

Attached File  British Aeroplanes, 1914-1918, by J.M.Bruce, page 455.jpg   202.16KB   654 downloads
And the analysis of this table show us a explicit error of speed 126mph at 10'000ft:

Attached File  Analysis.jpg   272.93KB   654 downloads
It's exactly what do I mean here:

some other sources says about 126mph (I don't believe them because it's impossible to have 138mph at sea level, 126mph at 10'000ft, and 123mph at 15'000 - it's a wrong curve in this case; 130mph at 10’000ft looks right, especially according on data for other versions of SE5 & SE5a, equipped other engines)
Do you agree, guys?
Sincerely,
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#46 piecost

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Posted 01 September 2011 - 11:16

The data table from British Aeroplanes 1914-18

Unfortunately, no trial report is given for the 200HP Viper test, or I might have been able to obtain a copy of the report.

Attached Files


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#47 hq_Reflected

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Posted 01 September 2011 - 11:19

That's the same as what An.Petrocivh posted. I think it's the best source we can get, but the 126 mph might be off, I agree.
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#48 ImPeRaToR

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Posted 01 September 2011 - 11:22

I am hardly an expert but all the other curves seem to have that "bend" in it so your adjusted curve makes sense to me!
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#49 piecost

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Posted 01 September 2011 - 12:00

doh, I didn't notice. I'll try to delete the post.

I will be posting more R&M reports for the SE5/SE5a in this thread:

Data Topic for Airplanes Performance.

over the next few days
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#50 ZaltysZ

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Posted 01 September 2011 - 12:06

Do you agree, guys?

Regarding the curve - yes, however are you sure that speed at 10000 ft is wrong and not at 15000 ft?
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#51 An.Petrovich

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Posted 01 September 2011 - 12:19

doh, I didn't notice. I'll try to delete the post.

I will be posting more R&M reports for the SE5/SE5a in this thread:

Data Topic for Airplanes Performance.

over the next few days

Thank you very much! Great docs! :S!:


Do you agree, guys?

Regarding the curve - yes, however are you sure that speed at 10000 ft is wrong and not at 15000 ft?

Yes, I'm sure:

Attached File  Profile.jpg   837.23KB   879 downloads
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#52 MiG-77

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Posted 01 September 2011 - 12:57

Do you agree, guys?


Yep, your corrected curve seems about right.
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#53 An.Petrovich

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Posted 01 September 2011 - 14:29

I've tested SE5a climb on ver.1.021 today, and the results are quite close to the test by MiG-77 (but I note the time from the start with the place; full fuel, no bombs):

5000ft - 4:17 (MiG-77 - 4:18)
6500ft - 5:45
10000ft - 9:50 (MiG-77 - 9:51)
15000ft - 18:18

So, it's better than real SE5a anyway. It will be fixed, of course.
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#54 An.Petrovich

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Posted 02 September 2011 - 12:37

Some discourse about stall speed.

I have two different sources where shows that the maximum CL of SE5a is likely not more than 1.1. The first source is aerodynamic characteristics of aerofoil RAF-15 (5:1 aspect ratio) where is CL_max = 2*0.52 = 1.04.

Attached File  RAF_SE5a_Airframe_Data.jpg   197.58KB   774 downloads

The second source is Reports and Memoranda, No.739, Apr.1921, where is CL_max = 2*0.55 = 1.1 for SE5a (elevators set to trim):

http://riseofflight....23903&mode=view" onclick="window.open(this.href);return false;">download/file.php?id=23903&mode=view
http://riseofflight....23902&mode=view" onclick="window.open(this.href);return false;">download/file.php?id=23902&mode=view

We also know that wing area is 244 sq.ft (22.67 sq.m) and gross weight is 1940 lb (880 kg).

The simple calculation by use a good-known formula for the Lift gives us the stall speed = 53.2 mph.

Even if SE5a have no military load (107 lb) and have no fuel and oil (247 lb) the stall speed is 48 mph. But many sources say about 42 - 43 mph. It’s possible only if CL = 1.44 for SE5a w/o military load, fuel and oil (GW = 1586 lb); or if CL = 1.76 for GW = 1940 lb. But it’s unreal CL for this type of aerofoil and biplane scheme.

(BTW, the same problem is about Nie.28 and its “worse horizontal maneuver” - because low CL)

What do I think about this?

I think that SE5a really has stall speed about 50 mph (depends on weight), but the airspeed indicator has an error at low airspeeds (depends on its place on airplane, airflow, angle of attack, influence of airscrew etc.) and may be a pilot actually see the stall speed a bit less on 5 - 7 mph.

What do you think, guys?
Sincerely,
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#55 MiG-77

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Posted 02 September 2011 - 12:45

I think that SE5a really has stall speed about 50 mph (depends on weight), but the airspeed indicator has an error at low airspeeds (depends on its place on airplane, airflow, angle of attack, influence of airscrew etc.) and may be a pilot actually see the stall speed a bit less on 5 - 7 mph.

What do you think, guys?
Sincerely,

I agree with that (and I had similar conclussion when discussing about this with Reflected). Also Naca (report no. 249) landing speed test show slowest possible speed for landing around 54mph.

Attached File  landing.jpg   190.56KB   759 downloads

EDIT: 54mph, not 53 :)
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#56 An.Petrovich

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Posted 02 September 2011 - 12:55

Great, thank you! :S!:
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#57 hq_Reflected

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Posted 02 September 2011 - 12:59

I could agree with that. If slowest possible landing speed of 53 mph, that would mean a stall speed slightly below that - so your 50mph estimation is very much plausible.

Mind you that's 7 lower than the 57 we have in game now)
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#58 An.Petrovich

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Posted 02 September 2011 - 13:20

Mind you that's 7 lower than the 57 we have in game now
Already fixed (will be released soon)
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#59 Greywing2

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Posted 02 September 2011 - 13:36

Mind you that's 7 lower than the 57 we have in game now
Already fixed (will be released soon)

Petrovich, can you please announce the list of FM fixes and in which patches do you PLAN to relese them?…to end our agony
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#60 An.Petrovich

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Posted 02 September 2011 - 14:01

TOP SECRET

:)

ok, no kidding:
I've been working about review FM of SE5a 2 weeks (fixed: dive, climb, maximum speed, stall speed, plane control), and this job will take 2-3 days on the next week, I think (it's already out of plan). But R.E.8 comming soon, and I have to return to developing of its FM… So, we're going to fix any other FM issues asap, but it depend on our roadmap of new airplanes. Hope on your understanding.
Sincerely,
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#61 1PL-Sahaj-1Esk

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Posted 02 September 2011 - 14:47

… oh I see, so you are the MAN our pleasure of flying depends upon :D good to know ;)

thx for reviewing the FM of SE5a, really, and I hope you can return soon and fix equally urgent FM issues.

:S!:
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#62 Greywing2

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Posted 02 September 2011 - 15:40

TOP SECRET

:)

ok, no kidding:
I've been working about review FM of SE5a 2 weeks (fixed: dive, climb, maximum speed, stall speed, plane control), and this job will take 2-3 days on the next week, I think (it's already out of plan). But R.E.8 comming soon, and I have to return to developing of its FM… So, we're going to fix any other FM issues asap, but it depend on our roadmap of new airplanes. Hope on your understanding.
Sincerely,

Ok thanks for the info. No problem in waiting and I know why the new planes have priority (money). But some FM innacuracies need and urgent fix because they are influencing on relative performance between planes (such is N17 too slow roll rate, Se5a "glass engine", Pup's climb rate, D7 roll rate, Bristols too good performance, Albatros speed etc.).
Is there a chance we can give a donations to 777 team to speed up the FM fixes? Im serious.
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#63 Jason_Williams

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Posted 02 September 2011 - 16:17

We're don't require donations nor do we want any. We continue to work on all aspects of ROF as fast as we can. Please stop with the donations talk. Just purchase content we make. That's all we ask. There is no way to speed up FM changes and it's clear we don't just make planes. We do a lot of other stuff as well.

Jason
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#64 Greywing2

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Posted 02 September 2011 - 18:20

We're don't require donations nor do we want any. We continue to work on all aspects of ROF as fast as we can. Please stop with the donations talk. Just purchase content we make. That's all we ask. There is no way to speed up FM changes and it's clear we don't just make planes. We do a lot of other stuff as well.

Jason

your talking like we are retarded….you have one guy for FM and more money will bring another…FM fixes should be very important as relative performance between planes is porked now (relative comparing todocs and pilot accounts). You cant postpone the fixes forever (we didnt get a single FM fix from the relase date).
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#65 JamesMcCudden

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Posted 02 September 2011 - 19:52

Great news about the SE5a,fantastic,cheers guys,great job.
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#66 piecost

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Posted 02 September 2011 - 20:02

Petrovich wrote
Some discourse about stall speed.

A very interesting post, I know that you do not have much more time to devote to the SE5a flight model changes but I'll add some comments anyway. I will also post the last of my SE5a documents R&M in the other thread.

I had not considered the ASI error and do not have a good feel for its magnitude. Unfortunately R&M 603 does not mention if the stall speed was indicated (with error) or calibrated (error removed). The British were aware of ASI errors at about that time and I will post some documents about it tomorrow (an R&M report from 1919/20).

With regard to the wind tunnel data you attached.

Rather than quoting the Reynold's number as is modern practice, the value of L V was used (wing chord in feet multiplied by airspeed in feet/sec)

RAF_SE5a_Airframe_Data contains a wind tunnel test of a 3inch chord wing at 40 feet/sec with LV = 10

R&M 739 contains wind tunnel data for a 7inch chord wing tested between 20 to 80 feet/sec with LV = 20.9 to 52

The full sized SE5a with a wing chord of about 5 feet at 50 mph has an LV = 170

From comparison of the values of LV from wind tunnel test to full-sized it is clear that the Reynold's number of the test is very low. Modern aerodynamicists would not place too much faith in
such small wind tunnel models, tested at low speed, without boundary layer tripping, being accurate to the full sized.

Significant differences between the wind tunnel data and full-scale are may be present. It is possible that the model tests will: under predict the lift curve slope, under predict the stall angle, under predict maximum lift (2D). Give different lift & pitching moment characteristics at the stall and over predict the zero lift drag and give different pitching moment.

It may be reasonable to compare the data with other wing sections tested in the same National Physical Laboratory at the same conditions. But to say that it is representative to full scale may not be realistic. I remember a graph of RAF15 at a wide range of Reynold's numbers - it may have been a NACA report - but I can't find it. This would offer a chance of correcting the data to full scale. In an ideal world we could find someone to run a computational method such as XFOIL to correct the data to full sized.

It is not that helpful for me to point this out, especially since we have no other data !

So the choice of CLmax depends on which has the biggest error: the ASI error or wind tunnel data error.
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#67 MiG-77

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Posted 02 September 2011 - 20:25

In web, you can find RAF15 airfoild data aswell IE http://www.worldofkrauss.com/foils/608" onclick="window.open(this.href);return false;">http://www.worldofkrauss.com/foils/608

Also NACA report no. 309 has RAF15 airfoil data for 36 by 6 inch modell:

http://naca.central....ort.php?NID=833" onclick="window.open(this.href);return false;">http://naca.central....ort.php?NID=833
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#68 An.Petrovich

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Posted 02 September 2011 - 20:33

… I'll add some comments anyway …

Good analysis, thank you!
However, you have already posted info for the full sized SE5a here, and it seems that CL_max is about 1.1, isn't it? Also, the biplane wings have a bit less CL than separate wing at the same AoA.

MiG-77, thanks for links!

Sincerely,
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#69 catchov

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Posted 02 September 2011 - 23:01

TOP SECRET


I've been working about review FM of SE5a 2 weeks (fixed: dive, climb, maximum speed, stall speed, plane control), and this job will take 2-3 days on the next week, I think (it's already out of plan). But R.E.8 comming soon, and I have to return to developing of its FM… So, we're going to fix any other FM issues asap, but it depend on our roadmap of new airplanes. Hope on your understanding.
Sincerely,

I know I can't say too much here because it's hush hush but thanks for leaking this Andrey. :S!: NEXT WEEK she shall be fixed and I shall be elated. :D
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#70 arjisme

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Posted 02 September 2011 - 23:37

I know I can't say too much here because it's hush hush but thanks for leaking this Andrey. :S!: NEXT WEEK she shall be fixed and I shall be elated. :D
Well, it was my understanding the changes to the SE5a FM would come in 1.022. Haven't heard about that being ready for next week. It's still great news that it is coming soon, but I think you are setting yourself up for some disappointment regarding next week. I'd be thrilled to be wrong about this, btw.
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#71 ImPeRaToR

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Posted 02 September 2011 - 23:40

Just because the S.E.5a FM might be fixed by next week does not mean that 1.022 will be released next week.
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#72 catchov

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Posted 03 September 2011 - 00:13

No problem gents and understood. :S!: I'm just elated that the fix is so rapid. :D
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#73 =IRFC=AirBiscuit

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Posted 03 September 2011 - 00:51

I'm really excited to fly a fixed SE5a – that'll be great! So many of the other planes need attention, too.. but this is an important first step towards delivering the historically accurate combat we crave so badly. I hope the Nieuports and Albatros all receive a little attention this autumn as well. Also, thanks a lot for disclosing this information, An.Petrovich!
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#74 SirFreddie

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Posted 03 September 2011 - 01:33

Nah! stuff the other FMs' Let's unleash the Evil superiority of the true SE5a FM on the virtual world :mrgreen: … Shut up Ball I'm tired of hearing about that N17 :D
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#75 =IRFC=AirBiscuit

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Posted 03 September 2011 - 01:46

Well.. it's going to climb slower, actually, so I think it's going to be even more raped by the Clown Wagon than it already is :lol:

At least it'll finally be able to out-dive that stupid, ridiculous plane.
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#76 Jason_Williams

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Posted 03 September 2011 - 04:46

We're don't require donations nor do we want any. We continue to work on all aspects of ROF as fast as we can. Please stop with the donations talk. Just purchase content we make. That's all we ask. There is no way to speed up FM changes and it's clear we don't just make planes. We do a lot of other stuff as well.

Jason

your talking like we are retarded….you have one guy for FM and more money will bring another…FM fixes should be very important as relative performance between planes is porked now (relative comparing todocs and pilot accounts). You cant postpone the fixes forever (we didnt get a single FM fix from the relase date).

Tvrdi,

Sometimes you make me wonder with your non stop nonsense. Just sit down and wait for Andrey to do his thing. Like he said and as I have said elsewhere on the forum. The FM changes will come over time and not all at once and don't expect wholesale changes to every plane. Andrey will change what he feels is wrong and will change what he can. FM changes will be rolled out over the next 6-12 months. It's always been in our plans, but new development and show stoppers take priority.

Jason
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#77 Josh_Echo

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Posted 03 September 2011 - 04:59

I think that SE5a really has stall speed about 50 mph (depends on weight), but the airspeed indicator has an error at low airspeeds (depends on its place on airplane, airflow, angle of attack, influence of airscrew etc.) and may be a pilot actually see the stall speed a bit less on 5 - 7 mph.
What do you think, guys?

Sounds right to me. I know that the Lockheed P-38 had this problem. Her pitot tube in the earlier production models (all but the last one or two, I.I.R.C.) was too close to the propeller or something, and so her power-on (military power?) indicated stall speed was something like 10 M.P.H. slower than it really was. So they came up with a table for calibrating the stall speed for pitot error. (Not into T.A.S., but calibrated I.A.S.)

This is wonderful news about making the S.E.5a more accurate, by the way. I judge from your posts that you are just as excited about it as we are. : )
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#78 piecost

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Posted 03 September 2011 - 23:17

The Effect of the Position of the Pressure Head on a Biplane on the Speed Indication

Reports & Memoranda No. 721

[Bristol Fighter, Sopwith Dolphin, BE2c]

Attached Files


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#79 piecost

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Posted 03 September 2011 - 23:17

The Effect of the Position of the Pressure Head on a Biplane on the Speed Indication

Reports & Memoranda No. 721

[Bristol Fighter, Sopwith Dolphin, BE2c]


…continued

Attached Files


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#80 piecost

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Posted 03 September 2011 - 23:19

Tests of Swivelling Pressure Heads

Reports & Memoranda No. 567

[BE2E]

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