Carenado T34B Navy Power and Airspeed

[84Park 3]

I am flying the Carenado T34B in FSX with Acceleration trying to use the Navy power settings. The problem is that airspeed is too high using the Navy specified manifold pressure and prop settings. For instance, with prop at 2000 rpm and MAP at 23", the airspeed (trimmed for level flight at 1000') is about 135-140 knots rather than 120 knots as anticipated. At 90 knots on approach with gear down, the prescribed MAP will accelerate the aircraft to 105 knots, requiring MAP to be reduced from the Navy specified value to 2-3" less to maintain the desired airspeed. My question is how to adjust .cfg settings to obtain the desired airspeed for the specified MAP and prop?

I could increase drag which seems incorrect, or maybe adjust rpm efficiency. Those were the only settings I saw that might match MAP to trimmed airspeed. If you have suggestions as to how to make this adjustment, I would like your ideas.

As purchased, the aircraft is a bit "lively" in elevators and ailerons. I have turned down their efficiencies to make the aircraft fly a bit more like I remember it--fairly well balanced but still able to do basic acrobatic maneuvers. I added John Detrick's VT-1 Navy repaint and edited the 2D gauges to better match the Navy instrument panel. Once I get the flight dynamics tuned a bit, it will fly like the original trainer.

If you have a well tuned T34B, I would appreciate getting a copy of your .cfg settings.

Thanks, Lowell

(Win7/8.1, FSX, Acceleration, FSUIPC, X52 Throttle/Stick, CH Yoke, Arduino Pedals, Mobiflight instruments)

[hs118 706]

Hi Lowell,

US Navy aviation obsessive/compulsive here. A long time ago, I decided to pass on the T-34B model. Lots of factors in my decision but mostly reasons identical to what you are finding: it does not fly like the NATOPS.

If you are keen on that type of flying, try the Virtavia T-34C. It flies very close to the book, has some interesting failure modes, and, overall, models the Navy training flights much better.

Hope you get a positive, direct response to your question. If someone has reworked the flight model of the Bravo, I might reconsider picking it up.

Good hunting in all your training.

[84Park 3]

Thanks, Henry. I have not flown the T34C, but I have that on my list. Your endorsement sounds good. I also have the Ants T28C & D which are a bit lively also, and also seems to have more power than I remember. They are fun to fly.

Lowell

[hs118 706]

What simulator are you using? FSX, FSX Steam Edition, P3D?

[84Park 3]

FSX with Acceleration. I have it running pretty well on both Win7 and 8.1. I have not used Steam or P3D.

[hs118 706]

I piddle in X-Plane a little bit and one of the developers for them had a video on configuring the controls dampening in the simulator. He based his settings on realworld aircraft design concepts. The short of all of it was, in the sim, he turned the sensitivity of the roll axis down about 5% from max, then applied some proportional factors. On the roll/aileron axis, he left the sensitivity at about 95% of max, on the pitch/elevator access, he reduced the sensitivity to about 2x the roll value, and on yaw/rudder axis, he reduced it to 4x the roll value.

I have applied this basic concept to all of my aircraft add-ons that use the built-in flight dynamics (not aircraft like PMDG, A2A, or VRS) and it seems to be more real world like.

The absolute amount of sensitivity can be adjusted to your taste and experience, the key thing is keep the proportions between the axes.

Hope this helps. Here is a screenshot.

http://www.fsfiles.org/flightsimshotsv2/images/2017/08/11/FSXControls.png

[84Park 3]

Thank you. I will take a look and try some mods to the dynamics. I checked out the T34C. They dropped the price so that has me thinking...

[84Park 3]

I spent most of today testing the T34B with various drag coefficients. The default coefficients for Parasite Drag and Induced Drag were set to 1.0 in the original aircraft.cfg. Those 1.0 settings gave level flight airspeeds of about +23 knots above those published by NATOPS for the T34B aircraft. An FSX Parasite Drag value of 1.65 provided the expected 120 knot level cruise airspeed for 23" manifold pressure and 2000 rpm as specified by NATOPS. Nose attitudes for 100 knot climb and 120 knot and 90 knot descents all seemed normal with that Parasite Drag value. However, Slow Flight required 18" MAP rather than the NATOPS 19"-21" to achieve 70 knots. Adding Induced Drag of 1.5 provided the desired Slow Flight 70 knots airspeed at about 19.2" MAP, and 63 knots at 18" MAP. The Induced Drag could be raised above 1.5, but I stopped at 1.5 to limit the chance of an unintentional low-speed stall during landing. Parasite drag has a strong effect at most throttle settings and Induced Drag has more effect at lower throttle settings. Adding the Induced Drag brought the Slow Flight dynamics into range with limited effect on higher throttle airspeeds.

I will test these two drag settings to determine if I experience any undesired effects during takeoffs, landing, or cross-country flights.

Lowell

[84Park 3]

To follow on this topic, the aircraft.cfg had two parameters set that greatly altered the flight characteristics of the T34B. The thrust_scalar=1.5 and power_scalar=1.050 seem to put the plane on steroids. When those were set to 1.0, with no added drag, the plane started to fly close to the Navy specs for AS by throttle MAP. The aircraft max_rated_hp=285.000 was also changed to 225 to match the Navy engine, but that seemed to have little effect. I am guessing the 285 was a typ-o from the T34A 185 engine. The plane continued to have huge swings in VS (+/- 1000 ft) and was very difficult to trim. I turned on Autopilot, and it could trim the plane very well, but when AP was off, trimming was almost impossible.  I saw in one forum that vertical_speed_time_constant might need to be checked, and in the T34B and Bonanza aircraft.cfg files,  vertical_speed_time_constant=1.0, while MSFT says the default should be 2.0. Setting vertical_speed_time_constant to higher values helped get the plane to where it could be trimmed in various attitudes. These changes have the plane flying the Navy Standard Field Landing approaches pretty much to spec, without the need for increased parasitic and induced drag. I still have a bit of tug-o-war between the elevator and elevator trim that needs to be fixed, but the plane is flying pretty well now.

I welcome any comments or suggestions for improving the flight characteristics of this plane.

Lowell