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Voyager

Planning flaps testing test plan

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Basically want to put together a simple and repeatable test of the flaps behavior in the P-47, and am looking for inputs to get solid runs. 

 

The theory that I want to test is that, in level flight, flaps should be expected to increase drag, and reduce stall speed. 

 

To test this, I'm proposing setting a P-47D-28, 100% fuel, with fixed loadout (extra ammo, all equipment including bomb racks, no external stores), using an air start at 1,000m and setting mixture to Auto lean, MP to 35", RPM to 1800, turbo to 0%, Oil Radiators to 100% Cole flaps to 30%, intercooler to 50%, aircraft in auto-level and then recording the equilibrium air speed with flaps up. If that equilibrium sipped is higher than 150mph indicated, reduce MP until an MP that produces a150mph IAS is identified and recorded. Then decrease manifold pressure until a stall is produced, then restart the flight and repeat this procedure for each of the numbered flap markings on the wing. 

 

My postulate is that the air speed for a given flap position will be lower for a given power setting, and that the stall speed will also be lower.

 

Anything missing in the test cycle? General thoughts? 

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Initial results, 150ias was at 56% throttle clean, stall was 120 IAS

 

10° 140mph at 56%, stall of 110

20° 130mph at 56%, stall of 106

30° 115mph at 56%, stall of 106

40° 85mph at 56%, stall of 85

 

The 40° flaps behavior appears to be an outlier, and I'll want to retest it a few times. One thing I did notice is that the angle of attack limits went way up once the flaps got to 30° deployed, as in the plane could sink at a high rate with the nose on the horizon and still have control authority. 

 

Afterwards I did try running the power up to see how it impacted the stall. I'll need to do a more thorough test, but at the 40° setting, running at 60", it seemed to drop the stall speed to the 60-70 mph indicated range. 

 

One thing that did cause some repeatability complications was the discovery that auto-level cuts out at 130mph.

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I suggest recording two to three polar diagrams in the power off or engine off condition at a fixed prop pitch.

In order to do this you would glide at a given IAS, starting from e.g. 1500 m ASL, and record the average sink rate for at least  4 speeds covering a range from stall speed to perhaps 400 kph. With tacview you get a lot of data, including the AoA.

 

In the end you plot the curves. The dots on the curves show you the lift-to-drag ratio across the speed range. If the modeling is correct in-game you should see that the L/D  ratio gets worse and the whole plot shifts towards lower speeds with increasing flap settings.

 

Here is the polar of the Fw190 A5 (no flaps).

661155740_FW190-A5Polar_AoA.jpg.b14604501f422bfa43cb639842e135ab.jpg

 

From this you can calculate the L/D ratio, also known as glide ratio. As you see the clean wing 190 peaks at an L/D of close to 12 at 260 kph IAS. The complete L/D plot would shift to the left and to lower glide ratios when deploying flaps.

914903180_FW190-A5Glideratio_AoA.jpg.bcd459adca023ce53ff0218234a31dee.jpg

 

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Could you walk me through what a polar chart is and how it's generated in this context? 

 

Also, are there ways one could generate the L/D for high power settings? 

 

Also, what command am I looking for to directly control the prop pitch? I've managed to get the prop RPM controlled and have found the command to toggle it to manual control, but apparently the control for prop rpm is separate from the prop pitch command. 

Edited by Voyager

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I would like to see Papafly actual test all of the aircraft!

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12 minutes ago, Haza said:

I would like to see Papafly actual test all of the aircraft!

You're asking a lot of him then. Especially without a robot pilot. But it would be also mostly academical, as for our practical purposes, the curves you get are largely similar (the aircraft perform similarish at similar power ratings) for the aircraft and you can roughly extrapolate depending on wing loading having this one curve. So you don't need to do all in detail.

 

That graph is good work.

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It would just be interesting to see another one his videos. In saying that I would enjoy anybody's videos demonstrating the various FMs and comparing RL with in game figures.

 

Regards

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Prop (pitch) and/or engine rpm have a major impact on the results and it's not really possible to make them meaningful comparable to real life figures or among each other in game.

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On 2/23/2019 at 2:40 PM, Voyager said:

Could you walk me through what a polar chart is and how it's generated in this context?

 

I'd love to but I have no time due to real life obligations... Sorry

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53 minutes ago, JG27_PapaFly said:

 

I'd love to but I have no time due to real life obligations... Sorry

 

That's fine. It happens. I think I've tracked down Tacview, and am working on getting it set up and understanding it, probably wit the wing-overs first, then I'll move on to more direct test events from there.

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image.png.a58a22c0a296c673919d02874f995f00.png

 

image.png.f7564a40114c2926cf36c598c606df87.png

image.png.a6d58c57b0dc2bb7f99e12f46e8aa164.png

 

Current results on 3.010C. The glide slope seems reasonable. It is interesting that at speed, it appears to have only slightly more drag than the 190. I expect that that combination of low unloaded drag, combined with ludicrous engine power is what gives it its reputation as a diver

 

What is surprising is the range of AoA's in the full flaps tests, but I'm unsure of what, if any, the significance may be at this time.

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Posted (edited)

Voyager

 

I would recommend that you go onto Berloga and record a few tracks.  You will be amazed at the number of players who can deploy flaps, climb vertically with no effort and still level off and then climb again, or even better, watch how the aircraft just floats on a cushion of air with full control surface authority!  However, watch it for yourself to believe it, before i'm accused of making things up!  My enjoyment of the game has now reached new lows and have lost interest in playing!  

 

Regards

 

 

Edited by Haza
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On 3/3/2019 at 7:04 AM, Voyager said:

image.png.a58a22c0a296c673919d02874f995f00.png

 

image.png.f7564a40114c2926cf36c598c606df87.png

image.png.a6d58c57b0dc2bb7f99e12f46e8aa164.png

 

Current results on 3.010C. The glide slope seems reasonable. It is interesting that at speed, it appears to have only slightly more drag than the 190. I expect that that combination of low unloaded drag, combined with ludicrous engine power is what gives it its reputation as a diver

 

What is surprising is the range of AoA's in the full flaps tests, but I'm unsure of what, if any, the significance may be at this time.

The clean curve looks a bit strange. Is each data point in the diagrams a mean over several seconds of stable flight (stable speed and AOA)? That is very important and can be easily checked in tacview.

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Posted (edited)
29 minutes ago, JG27_PapaFly said:

The clean curve looks a bit strange. Is each data point in the diagrams a mean over several seconds of stable flight (stable speed and AOA)? That is very important and can be easily checked in tacview.

 

The low end of the curve is not very stable. 

 

The methodology I was going for was a long trimmed decent at the target speed, however the plane tended to want to go for the speeds it wanted to go for.

 

To really do this right I'd need to do several stabilised runs at each trim configuration, in the test load configuration, but given nothing truly weird turned up in the initial runs, I'm not sure it's going to yield much. 

 

At this point I suspect what people are seeing is what happens when you combine Fowler flaps with high engine power on a fast climbing aircraft. I'm thinking the historical inability of the P-47 to safely deploy flaps in dog fights prevented this sort of behavior from occurring in real life, but that, by the late war versions, if they could have used flaps in combat, we'd have seen the same sort of flap usage that turned up on the P-38 and P-51.

 

I'm also going to reiterate, according to the listed stats, the version of the Thunderbolt we have in game is one of the faster climbing aircraft currently in the game. At 18.1 m/s, 17.6 at 3km, it will beat every Russian fighter except the La-5+ at sea level, all Fw-190 at all altitudes, and even give most 109s a run for their money below 3km.

 

Also, the 18.1m/s is with full guns and 50% fuel ~6000kg,and one can generally pull another 500kg off of that if one wants to strip the plane for dog fighting. Most of the other climbers don't have that much extra payload that could be pulled off. 

 

This is a very different beast from the early versions.

Edited by Voyager

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9 hours ago, Haza said:

Voyager

 

I would recommend that you go onto Berloga and record a few tracks.  You will be amazed at the number of players who can deploy flaps, climb vertically with no effort and still level off and then climb again, or even better, watch how the aircraft just floats on a cushion of air with full control surface authority!  However, watch it for yourself to believe it, before i'm accused of making things up!  My enjoyment of the game has now reached new lows and have lost interest in playing!  

 

Regards

 

 

How would tracks on Berloga be any more valid than recording aircraft behaviour flying solo? Especially when lag effects on a crowded server can make planes behave really, really strangely.
 

 

17 minutes ago, Voyager said:

 

The low end of the curve is not very stable. 

 

The methodology I was going for was a long trimmed decent at the target speed, however the plane tended to want to go for the speeds it wanted to go for.

 

To really do this right I'd need to do several stabilised runs at each trim configuration, in the test load configuration, but given nothing truly weird turned up in the initial runs, I'm not sure it's going to yield much. 

 

At this point I suspect what people are seeing is what happens when you combine Fowler flaps with high engine power on a fast climbing aircraft. I'm thinking the historical inability of the P-47 to safely deploy flaps in dog fights prevented this sort of behavior from occurring in real life, but that, by the late war versions, if they could have used flaps in combat, we'd have seen the same sort of flap usage that turned up on the P-38 and P-51.

 

I'm also going to reiterate, according to the listed stats, the version of the Thunderbolt we have in game is one of the faster climbing aircraft currently in the game. At 18.1 m/s, 17.6 at 3km, it will beat every Russian fighter except the La-5+ at sea level, all Fw-190 at all altitudes, and even give most 109s a run for their money below 3km.

 

Also, the 18.1m/s is with full guns and 50% fuel ~6000kg,and one can generally pull another 500kg off of that if one wants to strip the plane for dog fighting. Most of the other climbers don't have that much extra payload that could be pulled off. 

 

This is a very different beast from the early versions.

So the issue we're seeing with flaps might just boil down to the fact that we can deploy flaps symmetrically, which was never possible in the real thing?

I know people talk alot about the low speed stall issues in the P-47  and I wonder if a lot of it isn't just overdone flap effects on lift combined with perfect synchronization of flap deployment, rather than the kind of fundamental broken-ness people assume. 

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Just now, RedKestrel said:

How would tracks on Berloga be any more valid than recording aircraft behaviour flying solo? Especially when lag effects on a crowded server can make planes behave really, really strangely.
 

 

So the issue we're seeing with flaps might just boil down to the fact that we can deploy flaps symmetrically, which was never possible in the real thing?

I know people talk alot about the low speed stall issues in the P-47  and I wonder if a lot of it isn't just overdone flap effects on lift combined with perfect synchronization of flap deployment, rather than the kind of fundamental broken-ness people assume. 

 

RedKestrel,

 

I think the point that I was trying to make was is that there are players who are obviously aware of the issues with flaps and hence if you were to record it, you would see how wide spread this issue is!  Now I would agree that on a crowded server there may be some lag issues, however, in my time zone, whether the server is "crowded" or virtually empty, it matters not, as players apparently do it almost as a matter of course.

 

Regards

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I still see the same global issues in the stall behaviour I documented in my vid:

- ailerons are too effective at critical AoA and beyond

- ailerons produce too little drag in those conditions

- planes can be recovered from spins with out-of-spin ailerons only, even if full in-spin rudder is applied

- aileron effectiveness is increased drastically when flaps are deployed

 

The net result is ufo-like plane behaviour and the widespread  use of tactics that were unthinkable in reality.

I'm a real-life pilot but to be honest I stopped using real-life control inputs to exit from spins. Instead, I apply full right rudder, full power, pull the stick all the way and apply out-of-spin ailerons: this method is always faster, providing instant recovery.

 

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