Board index FlightGear Support Flying

Rudder-Alerion Trim

Controlling your aircraft, using the autopilot etc.

Rudder-Alerion Trim

Postby ricj7 » Tue Dec 23, 2014 2:05 am

What are the keyboard keys for the Rudder and Alerion Trims. Those small arrows on the HUD above and below Alerion and Rudder. The only trim I know in FG is the ELEVATOR which is used to put nose up or down to relieve the pressure on the yolk.

Also, while landing which is the fastest way to reduce the sink rate of the plane. Ofcourse nose up makes sense but that messes up the touch point on the runway or worst even create a scenario of overshooting etc.

This sink rate is probably the reason why upon landing there is a) either a small bump or hop by the plane or b) the nose goes up further creating a half-hop situation where plane angles up although still in some sort of contact with the ground i.e. landing gear first two wheels off the ground while third one still on the ground.
ricj7
 
Posts: 22
Joined: Fri May 11, 2012 3:49 am

Re: Rudder-Alerion Trim

Postby sanhozay » Tue Dec 23, 2014 7:42 am

Trim only makes sense with a joystick or yoke; to maintain level flight when the axes of the stick are centered. I don't know of any keyboard shortcuts for trim but some aircraft have controls in the cockpit and joystick/yoke buttons can be assigned to adjust it. Trim makes most sense on joystick/yoke buttons.

Are you using a stick or yoke?

When landing, if you are sinking too fast, you need to add some power. Bringing the nose up might stop you sinking temporarily but it just exchanges speed for altitude. If the speed gets too low, you risk a premature stall. So add a little power to reduce your sink rate and raise the nose if you need to avoid speeding up. Think of the power as giving you an extra push to your landing point. Obviously to increase sink rate, remove power and lower the nose to maintain speed.

When you are ready to land, bring the nose up gently (flare) and remove power so that the aircraft stops flying and settles nicely on the runway. Don't try and force the landing.

I'm assuming this is a tricycle gear aircraft you are flying but the same basic principles apply to conventional gear (tail dragger) aircraft, although getting the landing attitude correct is more critical in a tail dragger. The natural tendency of a tricycle gear is for the nose to go down on landing, which means it stays on the ground, whereas a tail dragger's nose wants to go up and start flying again.

What are you flying?
sanhozay
 
Posts: 1207
Joined: Thu Dec 26, 2013 11:57 am
Location: EGNM
Callsign: G-SHOZ
Version: Git
OS: Ubuntu 16.04

Re: Rudder-Alerion Trim

Postby ricj7 » Tue Dec 23, 2014 8:15 pm

I am using only keyboard, just do FG for fun, no intention to upgrade to joystick etc. as have no intention to fly in the real world.

I am flying 777-200 and do not use auto pilot etc. or go highly technical. Usually while landing what is the rate of descent recommended in the last 200ft ofcourse at 10ft a flare is needed which will further reduce the rate of descend.

One more thing, when taking off I usually employ 1st level of flaps, do not have nose (yolk) up at all., go full throttle. Usually plane itself takes off at 180-190 knots. After take off, I need to throw the yolk down 1-2 keystrokes i.e. nose down, to stop the plane from going nearly vertical up into the air. This way take offs are pretty much 30-45 degrees angle. However, is it a common practice in the real world?

At what point after take-off, time and height wise, should the pilot reduce his power from full throttle to say 25% of full. Should I not take off with 100% full throttle in order to avoid putting nose down to stop plane going nearly vertical?
ricj7
 
Posts: 22
Joined: Fri May 11, 2012 3:49 am

Re: Rudder-Alerion Trim

Postby sanhozay » Tue Dec 23, 2014 8:45 pm

You don't need to want to fly for real to get a joystick but it does allow you to fly more aircraft in a simulator -- helicopters and tail draggers are more manageable for example. Plus anything in a crosswind.

The rate of descent toward the runway is usually about 3 degrees, which equates to about 700fpm at 140kts.

Unless you have a lot of fuel weight on a 777, you don't need to blast it at full throttle. 5 degrees flaps for takeoff is usual I think, maybe 15. Rotate (pull back on the yoke to lift off) at about 150-160kts. Then maintain about 10 degrees pitch up and throttle back for a climb speed around 180-200kts. Down to 1 degree flaps at about 200, accelerate through 220 and raise the flaps, then push on to 250kts which is the speed limit below 10,000ft (can be exceeded with ATC clearance). From then on they usually increase speed, say 280-300kts and level out for the climb. Seatbelt signs go off around this time.

A climb at 30-45 degrees is a serious problem in real life because the flight attendants can't push the drinks trolleys up such a steep hill.
sanhozay
 
Posts: 1207
Joined: Thu Dec 26, 2013 11:57 am
Location: EGNM
Callsign: G-SHOZ
Version: Git
OS: Ubuntu 16.04

Re: Rudder-Alerion Trim

Postby Jabberwocky » Wed Dec 24, 2014 12:28 am

And you may want to try 0 and enter for rudders, 4 and 6 for trim and I think 7 and 1 for trim on the numeric keypad also. It's a while since I flew keyboard, but they are all there. Or were in 3.0 at least ...
Jabberwocky
Retired
 
Posts: 1319
Joined: Sat Mar 22, 2014 7:36 pm
Callsign: JWOCKY
Version: 3.0.0
OS: Ubuntu 14.04

Re: Rudder-Alerion Trim

Postby ricj7 » Wed Dec 24, 2014 6:23 am

sanhozay wrote in Tue Dec 23, 2014 8:45 pm:A climb at 30-45 degrees is a serious problem in real life because the flight attendants can't push the drinks trolleys up such a steep hill.


Lol!! with me in cockpit the pretties would not have to worry only about the steep angles but also lots of turbulence in up and down heights management. Guess my skills are only in the Cargo grade piloting as for now atleast.

guess the not 100% throttle works in not ending up with a steep climb. Basically for me the fun and challenge of simulator flying is only in the landings. I only fly from one airport to another and have not even climbed probably over 5K.

Btw, what is the way stop the plane from nosing up once the rear wheels have touched the ground. This nosing up even happens when landing at speeds of 110-120 knots. If i press on yolk down then the front wheel bangs down immediately.

Also is it ok to apply rudders once the rear wheel have touched, but not the front wheel. Upon landings the plane tends to go in the "left" direction and that's where another "wayward going" mess up happens if you are on the keyboard and not the joystick with throttle and rudder paddles. What are other ways, if any, to give plane on ground the direction without using the rudders.
ricj7
 
Posts: 22
Joined: Fri May 11, 2012 3:49 am

Re: Rudder-Alerion Trim

Postby sanhozay » Wed Dec 24, 2014 9:19 am

ricj7 wrote in Wed Dec 24, 2014 6:23 am:Btw, what is the way stop the plane from nosing up once the rear wheels have touched the ground. This nosing up even happens when landing at speeds of 110-120 knots. If i press on yolk down then the front wheel bangs down immediately.

Don't force the landing. Let the nose wheel come down gently if you can. It is unusual for the nose of a tricycle gear aircraft to want to come up after landing because the centre of gravity on an aircraft with a nosewheel tends to push the nose downward. Maybe you aren't reducing the throttles to idle?

Modern Boeing airliners have spoilers that can automatically deploy on touchdown and these will kill any lift. You'd usually set the speedbrake lever (found to the left of the throttles) to the "Armed" setting before touchdown to make this happen. Spoilers/speedbrakes look like doors on the top of the wing and add a lot of drag and reduce lift. The speedbrake lever can be pulled all the way back if you need to lose speed while descending (particularly approaching 10,000ft and the speed limit of 250kts). For landing, they would be returned to the armed setting to auto-deploy on touchdown.

Braking is well catered for on something like the 777. Autobrakes will apply gentle braking on the wheels after landing. I find the setting "1" is usually adequate. Pressing "b" to apply brakes disconnects the autobrakes. You also have thrust reversers which you can deploy after landing: pull the throttles to idle and press "delete" to engage and disengage. There's usually no need to panic and start reversing thrust and braking hard if you land on the landing zone of the runway. It will slow down.

Also is it ok to apply rudders once the rear wheel have touched, but not the front wheel. Upon landings the plane tends to go in the "left" direction and that's where another "wayward going" mess up happens if you are on the keyboard and not the joystick with throttle and rudder paddles. What are other ways, if any, to give plane on ground the direction without using the rudders.

Yes. Rudder would normally be applied throughout the landing and during roll-out (transition from landing to taxi). If you've been flying in Europe this week and using real weather, it's been very windy. The turning tendency on a jet aircraft usually comes from the weather-vane effect, where a crosswind from the left pushes the tail right and the aircraft pivots around the wheels making the nose go left -- like a weather-vane. Once the nose wheel is down, you get some steering capacity but, until then you may need rudder to keep it straight.

The rudder is the primary control for direction immediately after landing but the aileron is usually directed slightly into a strong crosswind. A joystick with throttle and an axis for the rudder makes all of this a lot easier (but you can still enjoy flying without one).
sanhozay
 
Posts: 1207
Joined: Thu Dec 26, 2013 11:57 am
Location: EGNM
Callsign: G-SHOZ
Version: Git
OS: Ubuntu 16.04

Re: Rudder-Alerion Trim

Postby KL-666 » Wed Dec 24, 2014 1:38 pm

Good account sanhozay. I just want to add that with (strong) crosswind the rudder usage can best be started at 10-20 feet above the rw, to align the aircraft with the rw just before touchdown.

On a crosswind approach you kind of fly the localizer sideways with the nose towards the wind. At touchdown that would mean the wheels would get a lot of side force. In extreme cases this can make the aircraft want to roll over. Therefore aligning the aircraft just before touchdown can be important.

Have a nice x-mas, Vincent
KL-666
 
Posts: 784
Joined: Sat Jan 19, 2013 1:32 pm

Re: Rudder-Alerion Trim

Postby ricj7 » Sun Jan 04, 2015 1:42 am

Thanks for all the inputs. Have figured out few things but upon landing the nose still goes up. Basically to reduce the sink rate, I go higher on the throttle and also use trim to put the nose up, so upon landing there is a "nose up" scenario even very mild to moderate. Reducing the sink rate has surely helped in avoiding the "hopping" of the plane after touching the ground.

One question: why does plane seems to be well and steady i.e. maintaining same altitude and then slowly starts to nose down and lose height. Is that something to do with wind pressure etc. outside or something needs to be taken care of inside the cockpit.
ricj7
 
Posts: 22
Joined: Fri May 11, 2012 3:49 am

Re: Rudder-Alerion Trim

Postby sanhozay » Sun Jan 04, 2015 9:48 am

A nose up attitude on landing is correct. Watch some real aircraft landing videos and compare your replays.

If you are taking energy out of the aircraft by reducing throttle it may have a tendency to lower the nose and lose height. Adjust elevator to maintain pitch and control speed. Adjust throttle to control sink rate. Speed and sink are interelated, so readjustments to both elevator and throttle will be required, in addition to aileron and rudder to keep it straight. All the controls are pretty active during approach and landing.
sanhozay
 
Posts: 1207
Joined: Thu Dec 26, 2013 11:57 am
Location: EGNM
Callsign: G-SHOZ
Version: Git
OS: Ubuntu 16.04

Re: Rudder-Alerion Trim

Postby xen_steda » Sun Mar 15, 2020 12:58 am

Let me dust this topic off for a second, is there an actual Rudder Trim in FG yet?

I know the "enter" and "0" keys move the rudder but once the rudder is moved by the joystick twist in my case, the trim is reset. This is unlike the way we have Elevator Trim from what I can see.

Thanks for any information.
xen_steda
 
Posts: 234
Joined: Sun Jan 05, 2020 3:53 pm

Re: Rudder-Alerion Trim

Postby D-ECHO » Sun Mar 15, 2020 10:44 am

There is a rudder trim in FG if the aircraft implements it. I.e., not every real aircraft does have a rudder trim so not all aircraft in FG implement it.
User avatar
D-ECHO
 
Posts: 2077
Joined: Sat May 09, 2015 12:31 pm

Re: Rudder-Alerion Trim

Postby xen_steda » Sun Mar 15, 2020 10:57 am

Hi there, would you know of any aircraft that have Rudder Trim and also use JSBSim so I could take a look at the code? Or do you know how to add it to an aircraft? Thanks!
xen_steda
 
Posts: 234
Joined: Sun Jan 05, 2020 3:53 pm

Re: Rudder-Alerion Trim

Postby D-ECHO » Sun Mar 15, 2020 11:28 am

A simple example would be the Cessna 140 in FGAddon. Look at Systems/fcs.xml, especially around line 92
User avatar
D-ECHO
 
Posts: 2077
Joined: Sat May 09, 2015 12:31 pm

Re: Rudder-Alerion Trim

Postby xen_steda » Sun Mar 15, 2020 1:24 pm

Thanks, this is the same set up I have on the T6 which apparently needs a Rudder Trim to be the most realistic. The "0" and "Enter" keys move the rudder, but it doesn't act like a trim tab would I think. The rudder trim seems to be wiped out when more rudder is applied by the joystick (this is the case with the Cessna 140 too) I would like the trim to stay on the rudder even after altering it with the joystick, like the trim stays on the elevator even after the joystick alters pitch. Am I understanding rudder trim wrong?
xen_steda
 
Posts: 234
Joined: Sun Jan 05, 2020 3:53 pm

Next

Return to Flying

Who is online

Users browsing this forum: No registered users and 2 guests