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PostPosted: Tue Jun 12, 2012 4:11 pm 
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Buzz313th wrote:
Thanks for replying Dudley, it's great that A2A has you as an adviser.

I'm the one who mentioned the instability of the Mustangs Rollout. I have no time in a P51 (wish I did) so I can't comment from experience. I got my info from a video another user posted of a current owner of the P51 named "Lady Alice".

If you view the video starting at 17:21 he starts talking about the rollout stability of the P51 that he owns. Maybe it's just specific to his mustang, dunno.


Here's the kink to the video. http://www.youtube.com/watch?v=WBIIhP_eOvE


I've seen this film before and I'm familiar with the pilot. He has a very nice well kept airplane. He flies well. He appears to me to be a VERY conservative pilot. My experience and I should say the general consensus in the Mustang community is that the 51 certainly isn't unnecessarily "tricky" on roll out, nor does it have any "unusual" traits in this area.
Keeping one's feet in the game is definitely advisable when flying ANY airplane, especially a tail dragger, but I would respectfully disagree with this pilot that the Mustang needs "special attention" because it's a Mustang.
I'm sure the pilot's comments are well intentioned and I have no doubt whatsoever that he believes what he is saying. If believing this is what it takes for him to fly safely I'm the last person on the planet who would say he's wrong to believe it.
As we say in the business............"whatever works for you"......or....... "different strokes for different folks!"
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PostPosted: Wed Jun 13, 2012 5:21 am 
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Hi,

I'll try and get some video of the behavior. It is so far off the chart it would be killing pilots in the real world.

EDIT: Thinking about it a bit more, it starts to get progressively worse from about 500 ft AGL with full flap and IAS about 180 MPH. It starts out yawing left requiring right rudder to correct, but in no time it "runs away" until you're against the stop and slipping like crazy. Despite the extreme slip angle at this point just to remain aligned, if you ease off to straighten it out, the aircraft will "blow" hard to the left despite the nose pointing right and rolling right to bring it back over whilst at the same time using a lot of power to maintain airspeed. Go-around is nearly impossible without extreme care. Once on the ground it will "blow" left and is uncontrollable. If you don't land to the right you will leave the runway. If you add a crosswind from the right, you're totally stuffed.

It isn't a rudder authority issue as there is plenty of that (fortunately so otherwise I'd be a smoking heap 9 times out of 10!).

This occurred with 1.3.x and 1.4 updates.

Best regards,
Robin.

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PostPosted: Wed Jun 13, 2012 12:15 pm 
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Out of curiosity, are you behind the power curve with this happens?

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PostPosted: Wed Jun 13, 2012 12:27 pm 
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CodyValkyrie wrote:
Out of curiosity, are you behind the power curve with this happens?



Yes... Aerodynamically I am. Personally I only experience this durring short final and slow, 100-150 MPH Indicated and in landing config with the power chopped to zero and high RPM on the prop. The Adverse yaw would get much more pronounced if I added power durring this flight state, but this is aerodynamically expected if we added power at high alpha.

And then once landed with tailwheel down, no brakes and power still chopped, the plane needs right rudder to stay on the centerline. This yaw moment changes as I transition below a certain IAS.

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PostPosted: Wed Jun 13, 2012 12:28 pm 
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I have never seen this, but I always keep power on during the approach.

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PostPosted: Wed Jun 13, 2012 12:33 pm 
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CodyValkyrie wrote:
I have never seen this, but I always keep power on during the approach.



Cody.. would it help if I recorded a FSRecorder track with all perameters recorded and sent it to ya? Then you could look at the data?

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PostPosted: Wed Jun 13, 2012 1:43 pm 
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Hi,

EDIT: In trying to get a video I think I found the problem: it flies better if you keep your feet OFF the pedals! It seems that the tiny bit of rudder input required (rudder trim neutral) to keep the nose aligned is too hard to input without slipping the aircraft. If you leave the rudder alone, the aircraft tracks straight (150 MPH, full flap), with only a tiny hint of left yaw.

:?

I'm going to try the same approach but with 5 degrees of right rudder trim (as recommended), see if that is all that is required. :? :?

Best regards,
Robin.

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PostPosted: Thu Jun 14, 2012 7:27 am 
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I'm afraid I just experienced the No-power pull-to-the-left rollout. Plane is in mint condition, according to the MH, so no mechanical explanation. No wind to speak of either. It was as if my brakes had locked up on the left side. On my next landing, I didn't experience this. Very bizarre.

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PostPosted: Thu Jun 14, 2012 7:53 am 
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Yes! It seems the problem is not related to the approach at all, but AFTER landing, during roll-out.

It seems that the aircraft enters a side-slip whilst on the ground and using rudder to maintain the center line. The wheels seem to have no grip on the ground, with the aircraft acting like it is still flying.

Maybe the landing is such that the sim thinks it is still flying and applies the physics of such?

I had it occur again last night after I applied a new procedure of not touching the rudder on approach more than necessary. The approach was fine to touchdown, then during braking the aircraft mysteriously slid sideways (like you applied a force from the side and pushed), requiring a boot full of rudder to swing the nose around (which made no difference despite a slip angle of 40 degrees and full power).

Best regards,
Robin.

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PostPosted: Thu Jun 14, 2012 1:33 pm 
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VulcanB2 wrote:
Yes! It seems the problem is not related to the approach at all, but AFTER landing, during roll-out.

It seems that the aircraft enters a side-slip whilst on the ground and using rudder to maintain the center line. The wheels seem to have no grip on the ground, with the aircraft acting like it is still flying.

Maybe the landing is such that the sim thinks it is still flying and applies the physics of such?

I had it occur again last night after I applied a new procedure of not touching the rudder on approach more than necessary. The approach was fine to touchdown, then during braking the aircraft mysteriously slid sideways (like you applied a force from the side and pushed), requiring a boot full of rudder to swing the nose around (which made no difference despite a slip angle of 40 degrees and full power).

Best regards,
Robin.


Robin,

I experience the very same thing on some landings, and the way you describe everything is spot on. Unless we're both crazy, this is some flaky phenomenon going on with the physics modeling in FSX.

What I've found:

!) This only happens with tailwheel type aircraft

2) Seems to be tied to saved flight situation (.flt) files, especially ones that have been saved after the aircraft in question has landed at least once before the save files is initiated.

3) Happens irregardless of crosswind component and loadout

4) Happens when the nose of the aircraft is perfectly aligned with the runway centerline at touchdown

5) There is not enough rudder authority to keep aircraft on the runway after yaw commences

Try starting a flight from the FSX free flight menu. Select the A2A Mustang and then select whatever airport you wish to fly from. Select clear weather. Start up, fly around and land - see if you experience the adverse yaw at all under these circumstances.

And you know what else I'm finding? If I intentionally touchdown with the nose crabbed off to one side, the Mustang will of course start skidding sideways, but I can fairly easily recover using copious amounts of rudder. The landings aren't pretty, but they are salvageable. HOWEVER, as you and I have both experienced, when the mysterious adverse yaw bug appears out of nowhere, it doesn't care how perfect your landings are, the aircraft is simply going to yaw violently off to the side no matter what. So what I'm trying to illustrate is the yaw bug isn't seemingly tied to your landing technique at all; rather, it's completely random.

The super weird thing from my experience is that I can almost always make the yaw bug happen when I used certain saved flight situation files. I promise it's not my imagination, lol.


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 Post subject: Maybe on to something
PostPosted: Thu Jun 14, 2012 9:39 pm 
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Ok,

I'm circling back to what I suspect are corrupted saved .flt (flight situation files) and their tie-in with the adverse yaw bug with FSX taildraggers. I just saved a takeoff scenario with the Mustang and now experience the adverse yaw bug on every landing when starting from the .flt situation file in question. Before saving the flight, I had just landed the aircraft. This seems to be a factor - having saved a situation file in which a taildragger has previously just completed a landing. I don't know why, but this seems to be a factor.

Solution - Restart FSX, and manually place the Mustang at an airport from the FSX free flight menu. Takeoff from the same airport, same weather, same loadout, same aircraft - problem has gone away. Landings are smooth and predictable again.

Cowinky dink?


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PostPosted: Fri Jun 15, 2012 12:51 am 
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Hobart Escin wrote:
Ok,

I'm circling back to what I suspect are corrupted saved .flt (flight situation files) and their tie-in with the adverse yaw bug with FSX taildraggers. I just saved a takeoff scenario with the Mustang and now experience the adverse yaw bug on every landing when starting from the .flt situation file in question. Before saving the flight, I had just landed the aircraft. This seems to be a factor - having saved a situation file in which a taildragger has previously just completed a landing. I don't know why, but this seems to be a factor.

Solution - Restart FSX, and manually place the Mustang at an airport from the FSX free flight menu. Takeoff from the same airport, same weather, same loadout, same aircraft - problem has gone away. Landings are smooth and predictable again.

Cowinky dink?


I don't think saved flights are the issue. Like I said, I 've seen the issue being discussed here, and I've -never- saved a flight with the Mustang.

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PostPosted: Fri Jun 15, 2012 1:52 am 
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bigjuicyspider wrote:
Hobart Escin wrote:
Ok,

I'm circling back to what I suspect are corrupted saved .flt (flight situation files) and their tie-in with the adverse yaw bug with FSX taildraggers. I just saved a takeoff scenario with the Mustang and now experience the adverse yaw bug on every landing when starting from the .flt situation file in question. Before saving the flight, I had just landed the aircraft. This seems to be a factor - having saved a situation file in which a taildragger has previously just completed a landing. I don't know why, but this seems to be a factor.

Solution - Restart FSX, and manually place the Mustang at an airport from the FSX free flight menu. Takeoff from the same airport, same weather, same loadout, same aircraft - problem has gone away. Landings are smooth and predictable again.

Cowinky dink?


I don't think saved flights are the issue. Like I said, I 've seen the issue being discussed here, and I've -never- saved a flight with the Mustang.


Duly noted. Well, every bit of user input helps in at least eliminating what the problem is not, so to speak. Try starting a free flight with one of the default FSX tricycle gear planes (anything EXCEPT a taildragger), then select the A2A Mustang after you have initiated the flight (i.e. already placed the default FSX tricycle at your desired airport). Give it a whirl around the pattern and see if the yaw bug is still rearing it's head.

This is really starting to bug me now. I mentioned earlier that I quit flying the A2A P-47 specifically because of this random adverse yaw bug on landing thing; it just got to be too frustrating to deal with. Again though, I've never experienced the yaw bug with either the A2A B-17 or the A2A P-40. Have you?


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PostPosted: Fri Jun 15, 2012 8:03 am 
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I don't know, it only happened once or twice

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PostPosted: Fri Jun 15, 2012 8:22 am 
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Nice find!!!

I have a saved situation involving an aircraft with a castoring NOSEWHEEL. Now I'm not sure if it is technically a tail dragger in order for this to function in FSX??? That aircraft never experiences oddities in landing, BUT the flight WAS saved after it had flown and landed again. :idea:

I'll change the default flight file back to the FSX default and shall try what you suggest.

Note that even when selecting an MP flight that the default flight file is still loaded, so any quirks as a result will be present at that point as well.

Best regards,
Robin.

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