Brief description of the issue:
At a given fuel flow, elevator position we should be able to get any plane to do a procedural climb, or decent. Should be able to fly straight and level. I can’t achieve this with any of the GA aircraft.
Detail steps to reproduce the issue encountered:
Try to a stabilize any aircraft to straight and level
Trimming these acft for level flight is very tedious. Trim for an airspeed then adjust the throttle to control climb or descent. Planes don’t care if they’re climbing or descending. They do care what their airspeed is. Trim controls airspeed not altitude.
Depends on what you’re trying to trim with. Trimming with a yoke or joystick is 1,000 times easier than trying to trim with a keyboard.
It also depends a lot on the weather…
Just made a test with the 172 in zero wind: it really easy to flight straight and level with zero input. I could make a really boring video: flying straight and level with autopilot OFF.
With default custom preset weather it will not be possible because the minimum noise in wind speed is too big. With live weather you can find a place with quiet conditions to practice.
Only during slow flight in smaller planes – like when landing. Another way of saying that is “pitch for airspeed, throttle for altitude.” This is not the way bigger / faster aircraft fly.
In airliners and most turboprop and jet aircraft, you’re always going so fast and how so much power that pitch changes won’t affect airspeed much. If you trim up, you’ll climb more than you’ll slow down. If you trim down, then you’ll descend more than you’ll speed up. So pitch primarily controls altitude while throttle, flaps, gear, and spoilers primarily control airspeed.
So in small planes when flying slow (landing), pitch (trim) for airspeed, and throttle for altitude. In larger, more powerful planes, in general pitch for altitude and throttle for airspeed.
Every aircraft has a happy airspeed that will allow stable, 0 trim straight level flight, with a centered CG. Generally, the faster you go the more nose down trim required and the slower you go the more nose up trim required. This is very simplified, but also fundamental. By using the operating handbook you can find a particular aircraft’s optimal power setting for cruise/climb. Some trim will always be required as the CG, aircraft weight, density altitude and mixture setting (normally aspirated engines) all have an effect. Wings level is also permanently adjusted, using bendable trim tabs on the ailerons and rudder, to a specific airspeed.
This all translates into a stable aircraft only at specific airspeeds. The proper method of achieving stable flight is to first set the desired power setting followed by using the controls, not trim, to put the aircraft in the desired attitude to achieve level flight, climb or descent. Once the airspeed begins to stabilize in the desired attitude use trim to remove the pressure on the controls required to hold the attitude. Very minor adjustments to trim and power may be required to hold the target speed and climb, descent rate or level flight.
Wind will have no effect on the process although may give the impression of instability in the event you encounter turbulence but a trimmed aircraft will always try to re-stabilize at the chosen attitude and airspeed.
Except in cases where the aircraft has transitioned into the “Slow Flight” envelope, attitude always controls altitude and power always controls speed. The argument is age old among instructors but is based on which should come first when changing attitude. Power/Attitude or Attitude/Power is a matter of preference as some believe one is smoother than the other. Both are acceptable means of control.
Nailing a given airspeed for the chosen attitude or holding a specific rate of climb/descent at a chosen airspeed takes practice and an attention to detail. One method of getting it right is to get the aircraft trimmed for level flight at the recommended cruise power setting. Once stable, pull off 100 RPM. DO NOT touch the trim. The aircraft will want to maintain the same airspeed and so will begin to descend. Note the rate of descent. Pull off another 100 RPM. Again note the rate of descent. With practice, you will know exactly how much to reduce throttle to achieve a given rate, for THAT aircraft.
The next exercise is rate of climb. Most GA aircraft always climb at full power. this is where the handbook comes in again. Find the Best Rate of Climb (Vy) speed and Best Angle of Climb (Vx) speed. Vy is the greatest gain in altitude over a given period of time. Vx is the greatest gain in altitude over a given distance. Use Vx on takeoff to ensure clearance over any obstacles then accelerate to Vy to continue climbing to cruise altitude. Airliners or any aircraft with extreme power to weight ratios will require reducing power to prevent overspeed even in moderate climbs.
All of the above will require putting the aircraft in a desired attitude and then trim to reduce the control input required to stay there. Practice, Practice, Practice. Soon you will be flying by the numbers too.
I’m not following you around trying to contradict you on every point, but pitch for airspeed, power for throttle is true no matter what you’re flying. An airplane always tries to maintain it’s trimmed airspeed.
Not a problem at all. I enjoy the debates, and I enjoy learning. When you go up against someone that clearly has a clue, anyone reading the debate is bound to learn a lot. Our debate in the IFR thread maybe could have been more productive by both of us focusing on the general before we argued the specifics – we really were getting very technical and splitting hairs, and at the end I think we lost the audience on what ATC is fundamentally for.
As for the trim question, I kind of made the same statement as you did – over at Avsim, I think – and a jet pilot told us that it didn’t work that way for anything but smaller GA aircraft. I find it wise not to argue with a professional pilot. I’ll see if I can’t find that post for you.
I would expect that again there may be some hair splitting.
If I am hand flying a 747 and have it trimmed for level flight, a reduction of throttle will result in the nose dropping and the airspeed remaining constant. A corresponding increase in power will result in a climb at the same airspeed.
At no point would I ever intentionally fly that 747 into the Slow Flight envelope anywhere buy in a sim. Doing so will result in the same effect achieved in a 152. Throttle will hold altitude, might even get a climb if the pitch is not too extreme. Holding that same attitude and reducing power will result in a descent. Pitch will now also have the effect of increasing/decreasing airspeed. The effect in a 747 is very mushy and delayed as a result of the time it takes to spool the turbine.
In the event of an overshoot at near touchdown speeds that 747 will have to transition through the Slow Flight envelope before it is flying again, that is why getting the drag cleaned up is soo important in that case. Must reduce the amount of time spent on the backside of the power curve.
For a real world example, take a look at an F18 doing a slow dirty pass at an airshow. The pilot is on the backside, controlling his altitude with power and maintaining above stall with pitch. Even the best of them can have a bad day on the wrong side of the curve…
You’re absolutely right – about everybody being wrong, I mean. Or your absolutely right – about everybody being right. Or something like that.
I started doing some research and found a paper on the Embry-Riddle site (link below) that says pitch and power (airspeed and altitude) are inseparably intertwined. If you trim for airspeed and expect to maintain altitude, you’ll have to add power. If you trim for altitude, and expect airspeed to remain the same, then a power change is necessary. Et cetera.
So it seems both are right, and everything depends on the context and what you’re trying accomplish. The jet video is a great example, as is knife-edge flight, etc. I’m calling it a draw and not arguing about this with anyone! 
Just as I stated above…
And the reason every aircraft is tuned to a “Happy Spot”. The most efficient way of getting throught the air is with the bare minimum of drag using the least amount of power possible. Each aircraft is going to have a “perfect” balance in there somewhere that will give you the best efficiency. But that’s where tradeoffs happen. ie: 65% = Best Endurance / 75% = Best Range
That’s pilotage 201.
That’s what I can’t do in FS2020! It’s constantly over correcting. The only way I can do it is with AP.
What controller are you using and what flight model are you set to?
Thrustmaster Hotas 4
Modern
What are you using for trim? Keyboard or controls mapped to your controller.
When you say, “It’s…”, what is IT? The trim?
Yes. Watching the wheel it is not moving (unless I move it) but the aircraft will continue to dive or climb which ever you are trying to do
Can you hold the aircraft in a level attitude with your controller?
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.