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[FSX] rudder and roll effect

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m3duzas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3duzas Quote  Post ReplyReply Direct Link To This Post Topic: [FSX] rudder and roll effect
    Posted: 01 Jun 2018 at 11:55am
Has anybody noticed that when You want to make f.ex. a cross landing, c152 is going upside down? :-D
Say about 10KTS cross wind, ~20ft above threshold, speed ~50 KTS. You have to kick rudder after levelling out, still crabbing and want to make a side slip to touch down........and boom! landing on a roof. The same is in the air, You can do flaps 30, speed somewhere like 45-50KTS and kick rudder hard as If You want simulate crosslanding. Surprise will come very fast but while having altitude You can save Yourself. When landing You just kiss the ground :-)

It is also visible while flying normal cruise speed (~90 KTS or whatever). When I kick rudder plane has a very strong rolling moment. Direction of the pedal is no factor, both make the same fenomena. I very well know that in theory rolling moment from rudder work is normal but I just don't racall that kind of insane visible behaviour from real c152.........honestly I don't recall it from any other FSX plane I bought.

 Can You please correct it, cause definitely there is something wrong with it? :-|

Thanx
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stephane130281 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stephane130281 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2018 at 3:45pm
I m not a developer.
However, if you want to take a cross landing with the C152, in real life you approach at a much higher speed than what you describe.

Typically I go 75 kts and 10° of flaps. You have more time during round out to side slip and feel the aircraft during the manoeuver. Starting it at such low speed and full flaps is not recommanded. Actually doing side slip with full flaps is generally not recommanded in most GA planes especially high wings since it can perturbate the elevator effectiveness.

In xplane 11 version tho, I obvserve a lack of rudder authority during power on and off stalls. When the wing drops, kicking the rudder does not induce enough rolling moment to stop the spin entry.
In P3D seems to be the other way around according what you describe!

Maybe try xwind landing at 75 kts and 10° flaps and try side sliping during round out.
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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2018 at 7:07pm
There are a few aspects to this, I'll try and cover all of them!

Firstly, you are seeing two different things - roll as a secondary effect of rudder use (which you describe at normal cruise speeds) and roll as a result of a stall (the landing phase).

The first of these should be easily held with just the smallest of aileron adjustment. I developed (as always) with max realism settings in the sim and max sensitivity settings / min null zones for all controller axes. What I see in the sim is a slight rolling with application of full rudder, again just a small amount of aileron required to hold wings level.

Going on to the second part, and your crosswind approach. Stéphane's comments are important. Further to those, I will add from the sim point of view that the sim does not like very very low stall speeds on conventional aircraft - I remember from the Pasped Skylark several years ago that it was a struggle to get the 35kt stall speed. The 152 with full flaps should, according to the POH, stall between 31 and 35 kias (41-42 kcas) dependant on CG position at a weight of 1670lbs. I am getting slightly higher indicated airspeed for the stall by a couple of knots.

Also from the POH, a normal approach using full flap is flown at 55 to 65 kias. You are attempting to fly well below these figures in a crosswind.

Remember that the application of slip will increase the drag element, so the closer you are to the stall speed when you apply rudder (and also the more abruptly you use it) the more likely it is that you will begin to feel the onset of stall or, as in the description you give of landing upside down, actually going fully into the stall.

There is plenty of info around the internet (though nothing official that I could find) which suggests that the use of full flap during sideslip in the 152 is unwise because the flaps blank off the elevator. For the purpose of clarity, slip includes both wings-level crabbing and wing down with the rudder holding the nose lined up techniques.

Cheers,
Paul.
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m3duzas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3duzas Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2018 at 10:16am
What You Guys are trying to explain here, as far as I'm concerned, has no place in real cessna neither 152 nor 150. To be honest no such thing is visible even in other FSX cessna's. For me this is anomaly. But ok maybe Your theory is accurate enough for You because You met it in Your real flight training. I won't argue.

75KTS on approach? let's face it, even though I'll hold that speed to the threshold, what will happen when going idle and flare? I still have to keep rudder kicked to hold the postion (propeller on the center line, one wheel should touch the ground first while plane is banked to the wind direction). Speed just before touching ground will come close to stall and this is the situation I was trying to illustrate. This is the moment plane is losing it's stability, going upside down and I have no chance to control safe position related to the ground only with ailerons. If I release the rudder I will land traversed which is ofc not good :(

I asked if somebody else met the same problem as I have, becasue there is a slight chance I have something messed up with my control settings.
But c'mon don't try to convince me this is a normal behaviour of c152 :-))
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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2018 at 12:40pm
As you mention, before touching the ground you will come close to the stall. If you stall with a bootful of rudder, you will spin. That is what you are seeing. You need to raise your speed to allow for this and fly the aircraft onto the runway in the strong crosswind rather than letting it do what it wants. Flying the speeds for a 'normal' approach on a calm day will not result in a happy landing.

below is a video of the JF C152 in P3D spinning, I am fairly certain that what you are seeing is the entry at the start of that:

https://youtu.be/inNmKbkz614

When you round out, you need to do so just above the runway - not high enough that the aircraft can end up on its back! Much easier in real life than the sim, I grant you, because the visual cues are far greater. Unfortunately, if you are comparing it to other FSX Cessnas you may be disappointed because this was not developed with them in mind.
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m3duzas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3duzas Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2018 at 3:11pm
I'm definitely not talking about spin. I know what spin is and how to enter spin, and even how to recover from it. I know flying phisics quite well, I have to because I fly this thing in real. To make it even more dramatic, the thing we are deliberating about (crosswind landing) is a standard manouver which is trained while gaining Your license. So I just tried in FSX what I was trained in a field.......and I landed upside down, and said to myself WTF? :))

Ok, I'll try to put it as polite as I can.....Your plane is graphically just great, I love it, sounds and everything, starting from the engine sound and all the stuff with switches radios, fuel valve, I don't regret I bought it. It's pure fun to sit in it and look outta window. But I'm disappointed when it comes to other things and I'm pretty sure this plane built somebody who doesn't have full idea of flying c152, sorry :) It's my opinion. I also count You Guys will make soon proper corrections so it will fly properly. I count on it.

Anyway, I'll try to correct this rudder thing on my own. I think I have some ideas but I have to test it for a while.

Thanx
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m3duzas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3duzas Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jun 2018 at 9:58am
Ok, fixed it.

Oh and one more thing this time concerning fuel comsumption.
Why when flying cruise speed with let's say ~2300-2200 RPM, FF is about 10 gal/h?
Shouldn't it be somewhere about 6,5 - 7 gal/h?


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stephane130281 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stephane130281 Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jun 2018 at 8:30am
Hi,

I don't have the FSX version since I'm flying the XPlane 11 version. That's what I said to the XP version developer that fortunately or unfortunately, since the C152 is probably one of the most flown trainer in the world, it is easier to point out the inaccuracies because we can easily compare to the real C152.

I personally was trained as well during my PPL with xwind landing and still continue to practice when xwind conditions occur and free plane available for renting.
That s might be CFI different way of teaching, on my side I ve always been taught that xwind landing should be carried out with 10° flaps max (depending on runway length obviously) and a much higher speed.
Normal landing procedure is to keep 65 kts and when runway is done 60 kts.
Xwind landing: flaps 10° and 75 kts, when runway is done slowly decrease the speed down to 70-65 kts during the side slip and put it on the ground on one wheel (wheel in the wind first) and it should be a firm landing, not a floating landing cause you will most likely drift on the runway since there is not enough weight on the wheel to give enough friction for direction control.
I'm not saying that you do it wrong, just that the technique I've been taught is apparently different to the one that you learned (CFI related most probably).

PS: for the moment, I continue flying the C172 until the flight dynamic is corrected :)
I also confirm that 2200 cruising RPM should give you between 5 and 6 gal/h.

Cheers
Stephane
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Delta558 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Delta558 Quote  Post ReplyReply Direct Link To This Post Posted: 04 Jun 2018 at 9:59am
Fuel flow should have been fixed ages ago! If you go to your Aircraft.cfg file, head to the [Piston_Engine] section and the last line should read bestpowerspecificfuelconsumption = 0.5. That should, when leaned, give you about 6 gph at 2300rpm.
You are also correct that I've never flown a 152 - all my powered time has been on taildraggers, much more funWink  The fde was developed using the POH and input / testing from several people who do fly the 152 (including at least one instructor).

Cheers,
Paul.
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m3duzas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m3duzas Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jun 2018 at 7:13pm
The thing with this fuel parameter works, thanx Wink

Cheers
Pawel

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