Flap deployment and pitching moment... and gear drag...

[DHenriques_]

Is there a model, that might be wrong? My airplane felt as if the nose was connected to the flap lever. It just nosed down. At the same time, it's not as if the pitch down, requires some heavy trimming (or pulling back on the stick), so it won't dive. The upwards ballooning of a Cessna, and the need to push against the yoke, was always much more noticeable, than the pitch down, of a Piper Cherokee model, or my RV.

Not sure I understand the question? What model? Which model? Real airplane? Sim airplane? )
DH[/quote]

I was just wondering why jcomm was asking. Figured it's some sim model, or a question in a different forum, perhaps. Not too long ago, a question was raised about a Carenado Piper Warrior (could have been the Archer) on the X-Plane org. forum. A student pilot thought that the Piper should pitch up with flaps. My recollection was..............that it was almost neutral or pitch down. The Piper definitely didn't pitch up like a Cessna high wing. Never the less, my reply's over there are moderated, and in this case, the student pilot's opinion was the last one, as mine never got posted. Of course, the A2A Cherokee doesn't pitch up. Now that I got that off my chest, it has nothing to due with this thread.... [/quote]

Oh, I understand.....I think )))

The one thing missing from this thread anyway is that it's not an either or situation regarding pitch up or pitch down high wing vs low wing with this issue.
Depending on the airplane involved there are various things happening and all of it is happening within the cg envelope. Some aircraft can be completely neutral as the weight and balance configuration vs the center of pressure movement rearward balance out as the flaps and or the gear cycle down.

Dudley Henriques

[jcomm]

Initial post was based on a sim vs sim behavior...

A2A's p51d Civil I believe belongs to a generation of accusimed aircraft that didn't have much of the flight dynamics inside of the a2a hands, but were still relying on MSFS's default core FDM. Most recent releases, as the C172, C182, Piper 180 and Comanche I believe are more sophisticated, and I believe I even read that induced drag calculation are now brought into Accusim.

Now, back to the topic, in the A2A p51d, lowering flaps to any detent, at any speed and or configuration results in an immediate pitch down. My comparison is DCS's P51d, where, depending on many factors as CoG, speed / AoA and hence CL, power settings, etc... different outcomes are possible, but there is always an initial slight tendency of the nose to rise, and only after that starting to pitch down to it's new trimmed state.

I was asking because just as Larry pointed out, in some real aircraft ( like his own Vans RV6 ), lowering flaps resulted in an immediate pitch down.

I believe the way DCS models the effect is probably much closer to reality, because a lot more is taken into consideration in their FDM, specially because I think that the A2A p51d is still using native FSX FDM...

[L.A.]

Initial post was based on a sim vs sim behavior...

A2A's p51d Civil I believe belongs to a generation of accusimed aircraft that didn't have much of the flight dynamics inside of the a2a hands, but were still relying on MSFS's default core FDM. Most recent releases, as the C172, C182, Piper 180 and Comanche I believe are more sophisticated, and I believe I even read that induced drag calculation are now brought into Accusim.

Now, back to the topic, in the A2A p51d, lowering flaps to any detent, at any speed and or configuration results in an immediate pitch down. My comparison is DCS's P51d, where, depending on many factors as CoG, speed / AoA and hence CL, power settings, etc... different outcomes are possible, but there is always an initial slight tendency of the nose to rise, and only after that starting to pitch down to it's new trimmed state.

I was asking because just as Larry pointed out, in some real aircraft ( like his own Vans RV6 ), lowering flaps resulted in an immediate pitch down.

I believe the way DCS models the effect is probably much closer to reality, because a lot more is taken into consideration in their FDM, specially because I think that the A2A p51d is still using native FSX FDM...

I suppose I have to ask why..................would you think that the nose has to initially rise? I'm aware that some low wing airplanes pitch up with flaps. I just don't remember flying any. And of course, there is many different types of flap configurations. The RV's flap setup is more along the lines of the P-51. I know that X-Plane can't figure out, if the plane should pitch up or down with flap extension. That needs to be entered manually. Personally, I'd be thinking that the DCS model is wrong. But then...........I've only ridden in a 1944 P-51 from a back seat (Cavalier conversion), and no controls.

[jcomm]

To be honest I also think it is wrong, at least in the amount of up nose I get, and the A2A probably a lot closer to reality, hence having asked the only who could answer from his real life experience - Dudley, more than I or any simmer

You're a different case Larry, because you did fly prop aircraft, and even owned one, with those particular characteristic, which, by the way, the Vans in MS FLIGHT did correctly replicate

So when I say the way DCS models is probably closer to reality, I mean the amount of effects and variable taken into consideration...

But from observing a few youtubes of RW pilot flying the p51d, I seem to see them trimming tail heavy as they deploy the flaps - so, apparently, they're exactly countering the pitch down tendency from flap deployment...

Know what Larry ? B.E.T. is no answer to everything

[DHenriques_]

Initial post was based on a sim vs sim behavior...

A2A's p51d Civil I believe belongs to a generation of accusimed aircraft that didn't have much of the flight dynamics inside of the a2a hands, but were still relying on MSFS's default core FDM. Most recent releases, as the C172, C182, Piper 180 and Comanche I believe are more sophisticated, and I believe I even read that induced drag calculation are now brought into Accusim.

Now, back to the topic, in the A2A p51d, lowering flaps to any detent, at any speed and or configuration results in an immediate pitch down. My comparison is DCS's P51d, where, depending on many factors as CoG, speed / AoA and hence CL, power settings, etc... different outcomes are possible, but there is always an initial slight tendency of the nose to rise, and only after that starting to pitch down to it's new trimmed state.

I was asking because just as Larry pointed out, in some real aircraft ( like his own Vans RV6 ), lowering flaps resulted in an immediate pitch down.

I believe the way DCS models the effect is probably much closer to reality, because a lot more is taken into consideration in their FDM, specially because I think that the A2A p51d is still using native FSX FDM...

I can't speak to DCS but I can confirm that A2A's FDE for the Civ Mustang is quite accurate.
Dudley Henriques

[DHenriques_]

A2A's p51d Civil I believe belongs to a generation of accusimed aircraft that didn't have much of the flight dynamics inside of the a2a hands, but were still relying on MSFS's default core FDM. Most recent releases, as the C172, C182, Piper 180 and Comanche I believe are more sophisticated, and I believe I even read that induced drag calculation are now brought into Accusim.

I believe the way DCS models the effect is probably much closer to reality, because a lot more is taken into consideration in their FDM, specially because I think that the A2A p51d is still using native FSX FDM...

[/quote]

Nothing could be further from the truth!

The FDE on the A2A Mustang was taken outside the default flight models and is run in Accusim. It is accurate to as far as we could go using actual experience flying the airplane. I would add that it is true the Accusim engine is improving as new aircraft come off the A2A flight line, but that involves both global and specific aircraft behaviors so that which is unique to the Mustang stays with the Mustang or if we notice something on the Mustang we think will make it better, that can be added to the FDE via any update.
Based on my personal experience flying the Mustang, the A2A flight model for the P51 is extremely accurate and that includes the pitch moments as included for flap deployment.
Dudley Henriques

[jcomm]

Dudley,

again, thank you for the response.

You quoted L.A, although it was me in an answer to him who suggested the FDM used for the p51d could be simplified...

I'm glad I was wrong.

Dudley, and it's not only the flight dynamics - it's the full effects of engine management, persistent engine and overall cell states from flight to flight, and many other aspects which are indeed unique to A2A's aircraft.

I diverted into combat flight simulators, but with the Comanche, I decided to install back the Sptitfire, the P51d, The B377, and am planning to get the P40 or the Razorback ( still haven't decided ), as well as the B17.

I have the Whole World simulated and excellent weather generators to make the experience in FSX overall more interesting.

So, don't get me wrong with my comparisons... I'm always trying to find perfection, and flight simulation is no exception ...