View Full Version : FSD Commander 115TC question
02-07-2002, 05:05 AM
I've been flying this plane ever since I bought it, but something bothers me (I'm not a real pilot): it seems that the aircraft can literally leap off the runway on takeoff. I use a USB Flightsim Yoke. When I reach 70 kts (full power), I gently pull the yoke and the plane goes off to a 1,000-1,500 fpm climb. I always have to lower the nose in order to get to a "normal" 500 fpm climb. I usually lower power to cruise at around 1,000 ft AGL and then everything seems normal again.
Trying to pull the yoke in an even gentler manner is next to impossible on shorter runways, even with flaps.
Is this a realistic behaviour? I know that if I kept the "leap" attitude for too long I would stall. But it's the "leaping" moment itself that I'm wondering about. Seems like a lot of vertical power for an aircraft going at 70 kts.
Thanks for any help.
02-07-2002, 06:14 AM
Yep, that's the Commander all right - load it up with four people and full fuel and still get 1,000fpm at sea level.
Trim is quite important for this aircraft - and fortunately this is one aircraft that trims properly.
Note the power settings in the kneeboard - you don't need full power for high rates of climb. 29 inches and 2,400rpm is enough.
02-07-2002, 08:26 AM
I have a Commander 114TC (must be the daddy of your plane?) I got many moons ago. I honestly can't remember who or what group designed it. It suffers from pretty much the same problem you relate above. It behaved pretty much like that in FS2000 as well.
Realistically or not (I'm not a real pilot either), I started setting the trim far "lower" than normal for a takeoff. I have the trim adjusted for a significant downward force on the elevator when I take off. That keeps it from leaping into the air - somewhat. But that also causes another problem.
Once you're safely off the runway and have a few hundred feet between you and terra firma, if you turn control of the plane over to the autopilot, watch out! That semi-negative or downward trim is going to make the plane descend suddenly before the autopilot has an chance to get the trim adjusted properly.
Either (1) "help" the autopilot keep the nose up by pulling back on the yoke or (2) adjust the trim carefully until it's in more of a normal attitude, backing off the power somewhat (you may still have to use a *little* push on the yoke), etc., until it all gets properly into sync.
We apparently need someone who knows more than us to tweak the flight dynamics! I'll bet in real life this doesn't happen that often! Granted, a small airplane (with a reasonable length runway) can buzz down the runway and gradually lift itself off without too much help from the pilot. But what you and I see certainly doesn't seem too realistic.
All that said, I love my Commander. I've gotten to the point now where that's about all I fly. Now if I could just fix my Pilatus PC-12 for FS2002!
02-07-2002, 08:27 AM
When using full power at 30inHG, the climb rate can be quite high, up to 2000, like you're seeing. This full power, max RPM setting should only be used for short periods, as in takeoff. I usually use full power up to 1000 ft, while I set the trim, and retract gear, retract flaps, and turn to the intended heading. Then lower the power to 29in 2500 RPM, to continue the climb. At that power and airspeed of 100 knots, you should get 1000fpm, approximately. I was lead to believe this airplane was quite realistically modelled.
02-07-2002, 09:28 AM
Yep, a common thread in most of Steve Small's flight models is that the trim setting reflects real world practice - he puts a hell of a lot of effort into getting the little things like the C of G correct.
A mistake often made is to assume that the `T/O` setting on the trim wheel is a fixed factor. It isn't. It's actually only accurate for one configuration of the aircraft, under certain circumstances. The rest of the time you must alter it by hand. Just take off with full fuel then go back and do it again with 15 percent fuel - you'll see (and feel) the trim difference!
In the real world books of trim tables can give you much more precise guidance on where you might expect to have to place the trim wheel before flight, and aircraft are often weighed and balanced for that reason, but we don't model that level of realism on FS, yet. Maybe FS2004...
For Steve's models I recommend trimming the aircraft BEFORE engaging the a/p, just as one would as a real pilot. We still have this awful FS legacy of a/p controlling attitude via trim. It's utterly vile and should have been banished years ago, but it does mean that it's better to start the a/p from a trimmed configuration, just like the real thing.
So with the Commander I get the wheels up, flaps up, set climb power and rpm, then engage the autopilot. For ultra-realism one should also get the aircraft trimmed in the desired climb attitude too, but FS can normally take over and put the aircraft into the correct pitch without too much difficulty.
If you go to:
they've got some clips from flight test articles on the Commander range. Just compare the numbers with the FSD Commander and you might be pleasantly surprised at just how close this baby is.
Hope this helps.
02-07-2002, 02:07 PM
Does an autopilot "trim" an aircraft in real life or is this manually done by the pilot. Is this an inaccuracy of MSFS2002?
02-07-2002, 02:34 PM
Yes the A/P trims the aircraft. You will see nearly constant slight movements of the trim wheel with the A/P engaged which must happen in order to maintain a constant altitude in spite of nearly constantly changing wind forces.
One of the more dangerous aspects of A/P usage (or merely in the case of electric pitch trim even without an A/P) is runaway pitch trim. I don't know if FS simulates that condition but it is a killer. The scenario is that the pitch trim engages without command, say it pitches up. The pilot panics and applies forward yoke/stick to counteract the climb but that just makes the up pitch trim behave more aggressively until the airplane is at an extremely high deck angle in spite of full forward yoke.
Then, the pilot gets his wits together... sort of...and defeats the A/P and or elec. trim by one of various means (pulling breakers, turning the master switch off etc.) but he still has full forward yoke applied and is about the buy the ranch as they say.
The BOLD FACE as the fighter jocks refer to emergency procedures, is to leave the yoke/stick alone and defeat the trim and/or A/P by systematically selecting A/P off, pulling the breakers (which you have a safety wire attached to so you can find it instantly) turning off the master, turning off the ignition until the pitch stops functioning.
If you're sharp, all that can be done in less than 10 seconds and you should be well bleow a stall angle of attack/airspeed in that short period of time with the only remaining emergency proceedure being a change of underwear as soon as practicable!
FS 2002 does simulate this it has happened to me by having the autopilot on and reducing power for a descent and forgetting to add power back when leveling off. The AP keeps trying to keep altitude and the plane is almost straight up.
02-07-2002, 04:18 PM
We bought our Cherokee 235 based on such performance.
We first test flew it on a cold winter day, with the FBO's chief pilot. There was him, along with my father and I in the plane, and none of us were light weights. I was much heavier back then, and between the three of us, and 504 lbs of full fuel, we were within 200 lbs of gross weight.
Just dial in some nose up trim, reach takeoff speed, and that Cherokee took off like a rocket. Good 'ol Verl Doolin (may he RIP) pegged the VSI at 2000 fpm. Indeed, she lept right off, very realisitic!
Leave the slow gradual climb outs to fully loaded aircraft on hot summer days, and even then.....;-)
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