I recently had the chance to fly Frontier Airlines from Denver, CO to Louisville, KY and back. The outbound flight to Louisville was in an Airbus A319, and on the way inbound to Denver, It was an Airbus A320. I noticed that our outbound captain taxied with only the #1 engine, and started up #2 only for flight. Our inbound captain taxied to the runway with both engines, but shut #2 down on the way back to the gate at DEN.I figured that asymetrical thrust wasn't really a problem, because the plane seemed to be taxiing quite straight.I had never done this in FS before, so I decided to give it a try. I replicated the aforementioned flight in every way possible, right down to the same aircraft starting at the same gate. I then tried to taxi on one engine but it didn't really work. The asymetrical thrust was so strong that above certain N1s, I couldn't taxi straight at all, and when I could, the plane kept pulling right and I had to deflect the rudder left to keep the plane straight.It's only on wing-mounted engines too, my MD-80s and CRJs still taxi straight even on one engine. I know that even in real life, asymetrical thrust affects wing-mounted-engine aircraft more than tail-mounted-engine aircraft, so this wasn't much of a surprise.This brought two questions up in my head that I couldn't really fathom. First of all, is there a way to reduce the effects of asymetrical thrust on wing-mounted-engine aircraft in FS?And what I've always wondered, does the asymetrical thrust really affect wing-mounted-engine aircraft in real life, even though I couldn't feel it? Was our captain having to deflect the rudder left to keep the plane straight, thereby dragging the slightly turned nosewheel along the ground?Thanks very much in advance!

Can't say how well it's modeled in FSX - I've used it and it seems normal to me. IRL, I had an engione go out in a Piper Apache and I can guarantee that I was really standing on opposite rudder until I got the rudder trim dialed in. I would guess in your real life flight that the Captain dialed in rudder trim to keep iot staight.As i said, I've had no problem taxiing with differential thrust in FSX.Vic

The only aircraft I have that taxys on one engine is the Majestic Dash 8-300.

You know its funny that you should mention this BoeingGuy, because I actually tried this for the first time yesterday in the LDS 767. I never though to try it, but I had been listening to the DFW tower all day long yesterday and there were really bad storms in the area. While the a/c on the ground were waiting for the storm to clear, many of them were directed to push back, start one engine and taxi to a waiting area. Later in the day while flying I though I would give it a shot in the LDS 767. I can say this about that plane anyway, frankly it doesn't work. I had only the left engine started and when I applied a little thrust the airplane would barely move, once I added more thrust it would start to go but wouldn't turn left only hard right. Having not flown an a/c of this sort in real life, I would have imagined that when only the left engine running it would have wanted to pull to the left, if anything with such a low amount of thrust I was giving it.In short it didn't work very well and I dont have pedals that have the ability to set up toe brakes for each side. Maybe then it would have worked better, but in the LDS 767 it doesn't seem to be modeled very well considering the amount of thrust I need just to start taxiing, then the amount of pull to the right was way to strong.I haven't tried in any any of my other payware a/c, but I may give it a shot just to see how well it works.

Rudder authority on the ground for most aircraft has no use until a given airspeed, on twins the engines are relatively close to the fuselage but there will still be a turning moment, the reason this doesnt work well in our FSX world is that ground friction is not properly modeled. You have to apply way too much thrust to get things moving when in most jets if you release the parking brake even at mid-weights the aircraft will start to move with engines at ground idle. Addons that model low breakaway thrust have I beleive had to tweak the airfile in other areas to achieve this result.I was on the 777 sim a while back and the skipper demonstrated to me how they perform a 180 turn on the runway at I think Jamaica, this uses differential thrust coupled with nosewheel steering, the effect is almost like the aircraft is on castors! Aim the nose so your positioned over the runway edge lights and stop at 45deg offset to runway HDG. Apply left engine power only and turn the tilller full starboard, flight deck almost goes backwards! IT is probably the most riskiest move BA do I fly GA aircraft and the difference between taxiing a prop on grass and on tarmac is huge. Grass needs at least 1800RPM to get the ac rolling but on concrete it will start rolling forward at 1200RPM In essence I think we need a new SIM1.DLL like the old FS9 one for this to work properly, but that then breaks all the addons

You know its funny that you should mention this BoeingGuy, because I actually tried this for the first time yesterday in the LDS 767. I never though to try it, but I had been listening to the DFW tower all day long yesterday and there were really bad storms in the area. While the a/c on the ground were waiting for the storm to clear, many of them were directed to push back, start one engine and taxi to a waiting area. Later in the day while flying I though I would give it a shot in the LDS 767. I can say this about that plane anyway, frankly it doesn't work. I had only the left engine started and when I applied a little thrust the airplane would barely move, once I added more thrust it would start to go but wouldn't turn left only hard right. Having not flown an a/c of this sort in real life, I would have imagined that when only the left engine running it would have wanted to pull to the left, if anything with such a low amount of thrust I was giving it.In short it didn't work very well and I dont have pedals that have the ability to set up toe brakes for each side. Maybe then it would have worked better, but in the LDS 767 it doesn't seem to be modeled very well considering the amount of thrust I need just to start taxiing, then the amount of pull to the right was way to strong.I haven't tried in any any of my other payware a/c, but I may give it a shot just to see how well it works.

If you have left only engine, the aircraft should pull ( or I should say pushes) to the right, not left, this is because thrust is only coming from the left side pushing that side forward, which results in the aircraft pushing to the right. It does make it hard to taxi in the opposite direction though. The CS767, handles this better than the LDS767 in this regard. Also with 1 engine, you should be using the right engine as Engine 2 then 1 is the proper starting sequence for the 767. That may have played a role since I believe that affects the hydraulics. One thing I did find interesting, is looking at the aircraft.cfg for the LDS-767, it appears it may be under powered. The LDS models the GE variant so the static thrust should be 62100, but it's only set to 61500. It may be done that way for a reason though, as it doesn't seem to effect expected flight performance calculated by the FMC. I also noticed the same with the CS767, but by a greater margin. This affected the flight performance of it. While it was able to reach it's optimum altitude calculated by the FMC it couldn't climb to it's max calculated altitude. Setting it to it's proper thrust rating it was able to make the climb.

If you have left only engine, the aircraft should pull ( or I should say pushes) to the right, not left, this is because thrust is only coming from the left side pushing that side forward, which results in the aircraft pushing to the right. It does make it hard to taxi in the opposite direction though. The CS767, handles this better than the LDS767 in this regard. Also with 1 engine, you should be using the right engine as Engine 2 then 1 is the proper starting sequence for the 767. That may have played a role since I believe that affects the hydraulics. One thing I did find interesting, is looking at the aircraft.cfg for the LDS-767, it appears it may be under powered. The LDS models the GE variant so the static thrust should be 62100, but it's only set to 61500. It may be done that way for a reason though, as it doesn't seem to effect expected flight performance calculated by the FMC. I also noticed the same with the CS767, but by a greater margin. This affected the flight performance of it. While it was able to reach it's optimum altitude calculated by the FMC it couldn't climb to it's max calculated altitude. Setting it to it's proper thrust rating it was able to make the climb.

Thanks for clearing that up Tom, makes sense. I am surprised that it is that hard to taxi in the sim with the LDS model. Like you said, maybe having the left engine on prior to the right made a difference. I will have to try with the right engine only, thanks for pointing that out. I had forgotten that it is the right engine that is supposed to start first.

Given that the cause of the problem is poor ground friction modelling is FS, maybe there's an argument for compensating for this by moving the engines?A user would need to decide what part of a flight model is more important; loss of an engine in flight or more accurate 1 engine taxiing?If you can't remember the last time you tried to fly your A320, B767 (or whatever) with 1 engine (and let's face it, how often does it happen in the real world), there must be a legitimate excuse for moving the engines in the aircraft.cfg i.e. move them closer, thereby reducing the exagerated asymetrical thrust.I've never actually thought about before, or seen it suggested, so there may be a good reason not to do this that I've not thought of.

..........there must be a legitimate excuse for moving the engines in the aircraft.cfg i.e. move them closer, thereby reducing the exagerated asymetrical thrust.......

Hi Paul,What is the .cfg variable that needs tweaking to achieve moving of the engines? I don't have a .cfg file open on this PC so maybe its obvious.Thanks, Bruce.

Hi Paul,What is the .cfg variable that needs tweaking to achieve moving of the engines? I don't have a .cfg file open on this PC so maybe its obvious.

aircraft.cfg

[GeneralEngineData]engine_type		=  0engine.0		   =  -6.32, -5.85,  0.00,engine.1		   =  -6.32,  5.85,  0.00,

Position paramenters are y,x,z in feet with respect to the refrence_datum position.y=fore/aftx=port/starboardz=height (up/down)

Hi Paul,What is the .cfg variable that needs tweaking to achieve moving of the engines? I don't have a .cfg file open on this PC so maybe its obvious.Thanks, Bruce.

Just remember, it's a catch 22 if you do this, don't expect to practice engine failure scenarios and expect the aircraft to behave realistically!

One of my favourite aircraft is the old B25 from MAAM-Sim; It comes with copies of the old flying manuals and a couple of old US Air Force instructional films on how to manage this bird without killing yourself. Anyway - I guess it about three, maybe four years back I did a number of left-hand circuit/full stops into Hellinikon - LGAT, Greece, and I was perfectly able to manage the aircraft, prop feather, flaps, landing and then taxy to park. It pulled, and seemed extremely realistic, but I wouldn't want to try a go-around in the r/w version....Haven't had her installed for a while, maybe will do it again tonight. Great aircraft to fly.... thanks..

Just remember, it's a catch 22 if you do this, don't expect to practice engine failure scenarios and expect the aircraft to behave realistically!

ThanksTom and Fr. Bill.Bruce.

You know its funny that you should mention this BoeingGuy, because I actually tried this for the first time yesterday in the LDS 767. I never though to try it, but I had been listening to the DFW tower all day long yesterday and there were really bad storms in the area. While the a/c on the ground were waiting for the storm to clear, many of them were directed to push back, start one engine and taxi to a waiting area. Later in the day while flying I though I would give it a shot in the LDS 767. I can say this about that plane anyway, frankly it doesn't work. I had only the left engine started and when I applied a little thrust the airplane would barely move, once I added more thrust it would start to go but wouldn't turn left only hard right. Having not flown an a/c of this sort in real life, I would have imagined that when only the left engine running it would have wanted to pull to the left, if anything with such a low amount of thrust I was giving it.In short it didn't work very well and I dont have pedals that have the ability to set up toe brakes for each side. Maybe then it would have worked better, but in the LDS 767 it doesn't seem to be modeled very well considering the amount of thrust I need just to start taxiing, then the amount of pull to the right was way to strong.I haven't tried in any any of my other payware a/c, but I may give it a shot just to see how well it works.

>> While the a/c on the ground were waiting for the storm to clear, many of them were directed to push back, start one engine and taxi to a waiting area<<B.S.Towers do not direct anyone to start one engine. LOLThis is a carrier or Captains choice to choose this. Please delete this misguided post to the original posters question.Mitch

>> While the a/c on the ground were waiting for the storm to clear, many of them were directed to push back, start one engine and taxi to a waiting area<<B.S.Towers do not direct anyone to start one engine. LOLThis is a carrier or Captains choice to choose this. Please delete this misguided post to the original posters question.Mitch

Just reporting what I heard over the transmissions on Liveatc.net. Take it up with them. I clearly heard them tell numerous pilots to go ahead and get one engine started and taxi to the hold area while they were waiting for the storm to pass. Why in the world would I make it up?I also heard on the same day another pilot of which airline I dont remember, have to return from where they were holding to get more fuel.