Ta 152

[Krusty]

Yes, it was merely a tangent. The main issue remains.

[Babalonian]

Mind I am not questioning the weight of the 152 so much, similar to the A-8 debate/issue (which is another story), but its handling characteristic of being so unstable at high speeds and consistent/stable at low to almost backwards speeds.

Yes, it was merely a tangent. The main issue remains.

Which is it's odd handling characteristics and stability issues, correct?  If the weights are correct, and their distributions are correct (?), then is a CoG issue completely ruled out?

In regards to CoG, I am no physics professor, but I thought it was heavily dependent on weights and distribution.  If it's not the weight, is it the distribution then?  Or is it certain that with the correct weights and their distributions that we have the correct CoG?

The 152s weight is right as far as my sources say. There is a bunch of differences with the 152c different motor different wing different tail.

I know there are a bunch of differences between the Cs and Hs, thus why I'm speculating about an inadvertant mix up between the two somewhere in something (the CoG?).  Either in regards to the aircraft's characteristic for so easily stalling at a high rate of speed while rolling, or in regards to its characteristic of being repeatedly recoverable starting at very low and backwards speeds as a stable aircraft should that also wouldn't so easily be induced into the stall in the first place (go back to my "repeatedly getting your tire stuck in the same mud hole traveling at 45mph, and repeatedly getting it unstuck bouncing it back and forth at 2-4 mph" analogy).  How is it possible to be so unstable to go into a tail-first stall at over 400 mph and then at the same time so stable/reliable at recovering from the backwards tail-first stall at negative to low airspeeds?

[Stoney]

stuff...

Do you understand how a problem with an aircraft's center of gravity is manifested in flight?

[Debrody]

Mind I am not questioning the weight of the 152 so much, similar to the A-8 debate/issue (which is another story), but its handling characteristic of being so unstable at high speeds and consistent/stable at low to almost backwards speeds.

I can agree on the high-speed instability, there is a nasty yaw motion what makes aiming very difficult even at 400mph. Whatever amout of fuel you have, this will appear.
It only increases when you slow down, with 75% fuel at 250mph you can instantly fall into that signature flatspin if youre unwary.
At slow speeds i wouldnt say the plane is stable, does the same moves without any warning as at higher speeds. The only thing that helps a bit is to dry out all the tanks.

To me it looks like a simple CoG issue, from the aircraft design or the modelling, i dont know. For me the biggest problem is the none to medium warning before the tailslide. Its not what i expect from a plane what has a very big and heavy engine in the nose combined with an enlarged tail section/vertical stab compared to its predecessor, the Dora. The P-39 has itss engine behind the pilot and i never had the same experience with it.
It would be nice to have a review on this question.
Apologize for the grammatical mistakes.

[FLS]

I think the handling issue is likely from having a high aspect ratio 48 ft wingspan on a 33 ft fuselage. German pilots, who typically had Sailplane experience,  wouldn't have as much trouble coordinating the increased adverse yaw as somebody encountering it for the first time.

[Stoney]

The P-39 has itss engine behind the pilot and i never had the same experience with it.

The actual location of the engine doesn't have any bearing on CoG.  What's important is where the sum of the moments occur.  Besides, even though the engine on the P-39 was "behind" the pilot, it was also pretty much right above the wing (i.e. very close to aerodynamic center).

It doesn't matter where the engine was, and it doesn't matter if they made the horizontal and vertical stabs bigger.  If the aircraft was still unstable despite this, or perpetually at the aft limit of the CG despite this, it could still potentially display this kind of behavior.

@Bablyon--my question remains.  I'm still curious as to whether you know how a CG problem would manifest itself in flight.  Because, in order to understand what you're suggesting, you have to understand how stable flight is maintained regardless of where the CG is.

[Krusty]

I'm not so certain it is purely CoG related. It looks and feels more like the stabilizers lose all impact on actual flight.

2 other similar examples of this happen: When the Mossie had quirks/issues, and when the Spit1 would pancake flat down. Both of these were cited by HTC as being 1) a CoG bug and 2) an error where the flight engine simply didn't know what to do.

Here we have a Ta152 where at speeds well above stall and high enough to "catch" the stabilizers and re-point the nose back into the direction of flight, it simply acts as if the tail is gone (sometimes).

To me it is indicative of a larger bug than just CoG. EDIT: Maybe CoG explains it, or maybe it's tied to it (as with Mossie), but it seems a flaw in the model rather than just poor weight distribution. Unless 90% of the weight was in the tail it wouldn't behave this way. Also, while HTC remodeled the airflow and lift and all that, I would imagine they kept the same weights breakdown/layout as in AH1, and AH1 didn't have any of these issues. Therefore I think the problem lies in the airflow/lift/control properties rather than only in the weight.

FLS: See above, aspect ratio may explain some things like the wandering nose in roll-outs, but not the above.

[FLS]

Krusty I believe the instability is due to the model being correct. We don't usually have to worry much about adverse yaw but the TA-152 really requires coordination.

[MK-84]

I'm not so certain it is purely CoG related. It looks and feels more like the stabilizers lose all impact on actual flight.

2 other similar examples of this happen: When the Mossie had quirks/issues, and when the Spit1 would pancake flat down. Both of these were cited by HTC as being 1) a CoG bug and 2) an error where the flight engine simply didn't know what to do.

Here we have a Ta152 where at speeds well above stall and high enough to "catch" the stabilizers and re-point the nose back into the direction of flight, it simply acts as if the tail is gone (sometimes).

To me it is indicative of a larger bug than just CoG. EDIT: Maybe CoG explains it, or maybe it's tied to it (as with Mossie), but it seems a flaw in the model rather than just poor weight distribution. Unless 90% of the weight was in the tail it wouldn't behave this way. Also, while HTC remodeled the airflow and lift and all that, I would imagine they kept the same weights breakdown/layout as in AH1, and AH1 didn't have any of these issues. Therefore I think the problem lies in the airflow/lift/control properties rather than only in the weight.

FLS: See above, aspect ratio may explain some things like the wandering nose in roll-outs, but not the above.

An aircraft can theoretically stall at any speed.

[Krusty]

I recognize that for the record. However accelerated stalls manifest themselves in snaprolls or dipped wings in those cases. In the Ta152 the main wing seems to remain unstalled and the stabilizers swing out in front of you.

So perhaps "stall" was the wrong word, in that it doesn't behave like a stall, but it was the closest choice.

[dtango]

@Bablyon--my question remains.  I'm still curious as to whether you know how a CG problem would manifest itself in flight.  Because, in order to understand what you're suggesting, you have to understand how stable flight is maintained regardless of where the CG is.

More specifically he needs to demonstrate how he has deteremined from the flying qualities of the AH Ta-152 where CG is in relationship to the neutral point compared to where he expects it to be.  After 12 pages in this thread I have yet to see evidence of this.

[dtango]

I'm not so certain it is purely CoG related. It looks and feels more like the stabilizers lose all impact on actual flight.

2 other similar examples of this happen: When the Mossie had quirks/issues, and when the Spit1 would pancake flat down. Both of these were cited by HTC as being 1) a CoG bug and 2) an error where the flight engine simply didn't know what to do.

The Spit1 and Mossie pancake issues are related to how AH handles deep stalls.  It appears they changed the Mossie's pitching moment to address it.  I guarantee you that at least the Spit1 (still), Spit5, P-51B/D, Hurri all still experience extreme stability in deep stalls still in AH ...unrecoverable (or nearly so) stalls that occur in situations like initiated from a tail slide, etc.  I would not be surprised that the 152 behaves similarly.

Is this is a "physics wrongness" issue or is this simply a detail of modeling issue?  Given that high alpha departed dynamics is fiendishly difficult to model even for aero geeks armed to the teeth with all flavors of CFD running on high end computers, I'll give HTC the benefit of the doubt to do the best they can to approximate what might occur in very high alpha situations .

[Krusty]

Dtango it's both an issue of physics being wrong as illustrated with how this planes flies. You mention only in deep stalls, but this is not a deep stall. This is in the middle of the prime manuvering envelope. As you can see on the film posted a page back and in my film and in other examples, the behavior is abnormal.

It's not that this is only at 50mph where you really force the plane into a tail slide by stalling nose high, nor is it only at 600mph where you dove straight down from 45000 feet to get fast enough to experience it. It's happening at speeds and moments quite normal to almost every plane in the game.

I don't recall a good explanation of the criteria used to "fix" the mossie being brought up either. How, exactly, was this fixed other than a lot of people doing a lot of checking and finding "this shouldn't be this way" ?

What's the established precedent required in this matter? Because I don't recall a level of doubt for the mossie being as much as demonstrated here.


As an aside:

I, personally, am not as attached to the CoG issue as just to the notion there IS an issue. So many things are all put into a flight model I don't know them all but I put forth it could be one thing or several, that end up with abnormal behavior. The end result is "broken," be it caused by CoG or something else. I'm all for "close" and I'm all for "good enough given the work required," but with the 152 it's an issue needing fixing.

[dtango]

Krusty, honestly I haven't looked at your film.  Nothing in this thread has given me any motivation to go through the trouble of resetting up my PC & associated equipment post-house-move for the latest ver of AH to analyze .  That being said departure ending ultimately in high alpha situations could occur no matter where you are at in the flight envelope.

As to the "152 needs fixing" IMHO I haven't seen any real physics argument demonstrating that the "152 is broken".

[Charge]

"It appears they changed the Mossie's pitching moment to address it."

Why, who requested it and with what data to support the idea that it is not prone to pancake with that round fuselage and that tiny rudder?

Mind you they put a huge a55 rudder to Ta152H and ME410 to make it stable so what was so special in Mossie it does not need that? 

-C+