Persisting issues with X-Plane Flight Model - defying laws of physics?

Question

I have been operating X-Plane for nearly 3 years, but I am still having issues with the flight models. Without applying thrust the aircraft moves forward on the ground plus what is more annoying it maintains altitude at a given speed without the application of thrust (thrust at idle)? Killing thrust does not seem to slow down the approach speed. This occurs with any aircraft type, stock or 3rd party. Interestingly when controlling the aircraft via flight director or autopilot the speed seems to be more responsive. Also aircraft often stall on manual approach when setting the aircraft 10 miles out of the airport. Flight controls are showed to be working in "Settings". What's more the problem does not seem to be consistent, not happening all of the time. Also the entire simulator seems to be running too fast! I have not put the simulation on fast forward. Related to this phenomenon on 6 x the Sim Speed with the aircraft on autopilot it is impossible to leave the sim alone for more then 5 minutes without provoking a crash of a flight continuing its flight plan. This is especially  annoying when operating a long haul flight. I have never managed to take-off and land an aircraft for a prolonged flight.

My biggest wish as to flight sim improvement is to be able to advance the simulation to any desired way point along the flight plan without having to fly the entire stretch in real time, either by dragging the aircraft on a moving map or by specifying a waypoint the aircraft should skip to. I realize that this poses a question by itself.

For now I would appreciate if anyone has experienced similar flight model problems and maybe solutions to overcome those.

My system profile:

My XP-10 setup is as follows:

XP 10-42 on Mac OS X El Capitan

iMac 27 late 2013 feat.  3,5 GHz Intel Core i7,

16 GB Ram 1600 MHz DDR3, 

NVIDIA Geforce GTX 780M 4 GB, 500 GB SSD

 

Main a/c in Hangar A320 Neo by Jar Design, Boeing 747-8i, Boeing 777 Worldliner, 

CRJ 200, Dash 8-400, Dornier 328

Scenery add-ons: Sky Maxx Pro, Zonephotos Fr, Alpilotx Mesh HD v3 Tiles

Saitek Controls: Joystick, Yoke System with Throttle Quadrant, Rudder Pedals

Answer 1

You may find it is the Saitek (now madCatz) controls needing a smidge more power than your system is sending them through USB. I have an X-55 which is 2 connectors plus Cessna style rudder which is a further 1. On FS9 and X-Plane it would do odd things and lose calibration - the fix - simple  - a powered USB hub. I tried suggesting to Mad Catz that they should mention this but they are deaf.

Answer 2

I have the same issue with the aircraft moving on the ground when the throttle is at its lowest power setting.

 

In XP10 the C172 just moves (and picks up a really good speed) even at the lowest power setting (800 RPM). This is unrealistic. In the real C172 I need to apply like 1200 RPM to get the aircraft moving (on near flat surfaces) which overcomes the inertia of the airplane. Then I can reduce to 'idle' speed. The idle speed I'm used to in the real C172 is 1000 RPM.

 

I've tried calibrating my Cessna Saitek throttle quadrant multiple times in settings 'calibrate joystick hardware' and moving the throttle through its full range. Maybe I'm not setting the idle thrust all the way?

Comments

The C172 in X-Plane is a default model. Expect some variance compared to real world. There is a payware C172 out there that is supposedly pretty good.

If you want to fiddle with the default Cessnas performance, use the (included) planemaker. First make a copy of the default Cessna (simply copy the folder and rename it), then open that one in planemaker. Change tire properties, propeller efficiency, engine horsepower, etc. until you are happy. Check your joystick range by outputting the axis values "on screen" (use settings, then data output). That way you can see if it is calibrated properly.

Jan

Answer 3

Sounds odd! Make sure that your hardware thrustlever is getting read correctly. It sounds like you are not setting "idle" thrust all the way.

Also be aware that most airliners WILL start moving on the ground with idle power, this is correct behaviour. They will also not loose any speed during approach at idle power UNLESS you deploy flaps and/or landing gear. Airliners are built to be slick and have little air-resistance, they will usually glide about 1 NM for every 350 feet of altitude at idle power.

Make sure that you dont accidentally set X-Plane to cover ground at an accelerated rate! There is an option for that (to make long flights go by faster) and you might have toggled it inadvertantly.

For someone who has so many problems and has  "never managed to take-off and land an aircraft for a prolonged flight." you have certainly an impressive amount of payware aircraft and add-ons, so I guess you are not easily discouraged :-)

Jan

Comments

Well Jan, first of all thanks for the quick reply. Yes, I am not easily frustrated by the sim, although I strive to make it appear more realistic to me. I probably would not have written in this forum, if a friend of mine didn't experience similar problems with his sim, though he is still on X-Plane v. 9.

I find it hard to accept that the aircraft can taxi or maintain constant altitude and speed with thrust @ idle.This does not represent real life physics. I am aware of the glide # which of course is best in a glider plane and worst in a fighter plane. As for decelerating speed with high lift devices, shouldn't it be the other way around. Flaps are deployed at lower speeds as to maintain lift at slower speeds. I get the impression that speed brakes in a number of aircraft do not correctly decrease speed. I observe this with stock aircraft or gratis 3rd party aircraft, like the Boeing 737 from EADT, or the Dornier 328-110 i.e. when flown manually.

I have all my flight controls set to work linearly.

On the issue of accelerating the sim speed, I am sure the sim is set up correctly. I have programmed two buttons, one to select the multiple speed options 2x, 4x and 6x and one two accelerate the sim at max speed at the chosen rendering settings  This option I however hardly use, because it does not give me any benefit. For me the first option works best for long range flights if I sit by the sim.

I am mainly interested if this kind of behavior is experienced by other simmers as well. If it cannot be remedied with the current version set-up it leaves us hoping it will get fixed in some future version.

Not to get me wrong, I am not at unhappy with the sim, just striving to make it better, unless I am the only one to observe this behavior.

---

Hi again,

an aircraft can taxi at idle thrust - but of course it shouldn´t be holding its airspeed at idle thrust without sinking. And flaps do increase lift, but at an even higher increase of drag. Thats why they are only used during take-off and landing.

Speedbrakes are increasing drag AND decreasing lift, so you might see more of an increase in sinkrate than a decrease in speed.

Without getting into a too deep discussion of aerodynamics: Rest assured that X-Plane does the best job of simulating flight that is available for PC simulation. The effects you see are not reported by anyone else, and are therefore not going to be changed or fixed in the future.

I can not vouch for 3rd party airplanes, and of course it is possible to feed wrong values to X-Plane, resulting in an erroneous flight-model. But there is (almost) nothing wrong with X-Planes basic flight model.

Good luck, Jan