Cessna 172R Flight Characteristics vs. Previous Models

[silentsage]

First, thanks to A2A for another great aircraft.

I have a question about the flight characteristics of the 172R vs. previous models. I have several hundred hours experience flying 172Ls, Ms, and Ns (as best I can determine from my log book). I have never flown an R model.

The only significant difference I see between the actual aircraft I flew and the A2A 172R is the behavior on take-off. In the older models, when set at take-off trim, it required a solid a pull on the yoke to rotate the aircraft for take-off at 65-70 knots. The A2A 172R flies itself off the ground at around 60 knots.

I don't question the validity of the A2A flight model. I'm just curious if anyone knows what was changed in the R model to make it behave this way. Did Cessna simply redefine the "take-off" trim setting"? Was the CG moved aft vs. the older models?

Not a big deal, but if it behaves this way in real-life, it would be disconcerting to have the aircraft leave the ground at that speed on its own. Forcing it to stay on the ground (i.e., forward stick) would be a bad idea due to the risk of wheel-barrowing down the runway.

[Nick - A2A]

Interesting post. I don't think your observations are consistent with my installation of the A2A 172R though. It never seems to need any forward control input during the take-off run (irrespective of W&B) and I'd guess it would lift off at about 70-80 KIAS if I hadn't introduced any aft control input beforehand.

Just wondering before further troubleshooting/discussion: did you download and run the Accu-Sim update after you installed the Skylane? The store download doesn't include all the latest updates and fixes and it's been a while now since A2A released the 172R, so there have been quite a few of those!

Cheers,
Nick

[silentsage]

Yes, everything is the latest and greatest. There are other threads in the forum where pilots with 172 experience have questioned the take-off behavior at the standard trim setting. None of those threads discussed the issue of why the R model might be different from previous models, hence my question. I searched the web for any info on the R model that might explain it but couldn't find anything.

When you purchase the 172 you get version 1, and the latest version is 2.14..............

[Nick - A2A]

Okay, what's your total weight when you see this behaviour? Also, are you talking about a take-off with the flaps retracted or at 10°? I'll see what I get with same config.

Nick

[Nick - A2A]

When you purchase the 172 you get version 1, and the latest version is 2.14

Just seen that edit to your post. Not sure about version numbers, but did you actually run the updater after installing the Skylane, and did it detect and update the installation properly?

Sorry to bang on about that, but it is worth double-checking.
Nick

[silentsage]

Yes and yes.

Payload is full fuel, full oil, 170 lb pilot. Field elevation is 700 MSL, temp is 78 F. Flaps are full up. Take-off trim setting is "take-off". Full throttle at take-off, mixture full rich. Local winds are set to zero MPH.

[Nick - A2A]

Okay - very quickly tested as I already had FSX running. With exactly the same config and W&B, and no pitch input whatsoever, I saw the 172R begin to pitch up and leave the runway at 75 KIAS, before it stabilised in the climb at about VY. Does that sound very different to what you're seeing?

Nick

P.S. Tested at just 20' or so above MSL and 59°F but that shouldn't make a difference if we're talking IAS.

[silentsage]

That's interesting. I'm running P3D v3.3 (latest version). I've been flying all afternoon and it consistently starts to raise the nose at 60 knots and the wheels leave the ground at 65 knots. At 79 knots it requires significant forward stick pressure to maintain that speed until retrimmed. If I leave it hands-off it continues to pitch up until it stalls (i.e. never gets to a stable climb).

I can't imagine the internal flight models between P3D and FSX are that different. I wonder if, in general there are slight differences between the P3D implementation and the FSX version.

Anyway, this has been an interesting exchange of notes on a Sunday afternoon.

[Nick - A2A]

Mmm! definitely sounds like there's a difference somewhere in the installations, unless it's a hardware thing. Do you have any axes set to control trim for instance? (I don't) Just to rule out an updater issue, please could you try manually deleting the following folder:

C:\Program Files (x86)\Lockheed Martin\Prepar3D v3\A2A\Cessna172\Update_fsx

Then re-run that Accu-Sim updater.

Thanks,
Nick

P.S. Early hours of Monday morning here unfortunately!

[silentsage]

I'll try it tomorrow and let you know..........

[Killratio]

Sim aside, just on the R model IRL.. the aircraft has a much heavier "feel" and always seems to have more inertia than the earlier models. I suspect the CG is slightly to the rear of where it used to be due to the deeper fuselage and more (heavier) creature comforts in the cabin. A slight "rocking" (manually ) on the ground from the wintips gives a completely different feel to the earlier models. In additions, stall tests we did, with 3 POB, took much more effort to recover from than the earlier models, despite "normal" stalls being easier... and with 4 POB stalls could be quite disconcerting, with the nose taking time and effort to force down.

Nick, I'd NEVER put forward pressure on the column on the takeoff run..as said, wheelbarrowing is a great danger. My technique has always been to hold back pressure as speed builds (to take pressure off the nosewheel) and then as speed builds towards takeoff, ease that pressure to neutral (or slight back pressure for a quicker liftoff). She will easily fly herself off You HAVE to be ready for considerable forward pressure to stop the nose climbing too far and at the same time be quite quick on the trim wheel to make life easy. I hold her just above level for a few seconds build speed and to adjust trim then pull up into a proper climb, adjust trim again. Solid a nosedown trim is needed for an 80knt climb at full power, along with firm rudder pressure.

I always found the R to be almost as different to fly from the earlier models as THEY are to fly from a 152... albeit in very different ways.

[Nick - A2A]

Nick, I'd NEVER put forward pressure on the column on the takeoff run..as said, wheelbarrowing is a great danger.

Thanks Darryl - yeah, agreed. (Well, with the caveat "unless the nose started pitching up unexpectedly because of a trim or W&B issue".) My point was that this isn't something which is needed in my installation of the 172R.

For the OP, one other thing I should probably have asked is did you check the maintenance hangar to make sure there are no defects with the trim tab or elevator?

Nick

[Oliver Branaschky]

I would definitely check whether the update was applied successfully, maybe even delete the update folder (Nick knows just how to do this ), for this sounds all too familiar, like for instance in this thread: http://www.a2asimulations.com/forum/vie ... hp?t=55066


Viele Grüße/Best regards
Oliver

Oliver Branaschky

[bobsk8]

I would definitely check whether the update was applied successfully, maybe even delete the update folder (Nick knows just how to do this ), for this sounds all too familiar, like for instance in this thread: http://www.a2asimulations.com/forum/vie ... hp?t=55066


Viele Grüße/Best regards
Oliver

Oliver Branaschky

That is exactly what happened to me even though I ran the update multiple times, it didn't work until I deleted the Update folder first. This happens too, when upgrading P3D to a new version, if you have P3D. You have to delete the update folder.

[AKar]

Either of you using/not using ASN/AS16 real weather?

-Esa