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Crosswind takeoff and landing, Cessna 172p

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Crosswind takeoff and landing, Cessna 172p

Postby ohneale » Thu May 27, 2010 10:42 pm

I'm using Flightgear 1.9.1 on Linux. During takeoff in 15 kt crosswind I find it difficult to keep the aircraft on the runway because the rudder seems unable to counter the crosswind even with full deflection. Has anyone encountered similar behavior? The Cessna 172p is rated for at least 15 kt crosswind, is it not?

Another question: sometimes during landing just before or after touchdown when I'm pulling up, the elevator is abruptly deflected up far too much. Needless to say, this is not a good thing and usually leads to a short bounce and a stall. Old optical mouses often jump in a way I imagine could cause this but my mouse (Logitech RX250) is not old and I have a mouse pad that is supposed to be good for gaming. I have never seen any cursor jumps outside Flightgear. Has anyone ever encountered similar problems?
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Re: Crosswind takeoff and landing, Cessna 172p

Postby dany93 » Sat May 29, 2010 6:22 pm

Hi ohneale,

I'm using FG 1.9.1b on Windows Vista.
I think most, if not all real aircrafts, including ultralights, are able to takeoff and land in 15 kt crosswind.
Takeoff with Flightgear Cessna 172p in 15 kt crosswind is possible for me with about 50 % rudder (it may depend a bit from the wind side). It's even possible with 20 kt (60 - 80% rudder)
Something else: Do you know your mouse can temporarily act as a rudder by Left Clicking for rollling on the runway? It is easier to control (at least with no or weak crosswind, because you need yoke for ailerons with strong crosswind).

During landing, C 172 may be a bit too sensitive to the yoke (elevator), but it is still controllable (moreover, I feel it is more "soft" with mouse than with my joystick).

You can read your rudder, ailerons, elevator positions by:
Help > Joystick Information,
and
File > Browse Internal Properties > Surface Positions.

Dany
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Re: Crosswind takeoff and landing, Cessna 172p

Postby sim » Mon May 31, 2010 12:28 am

A touch of brake on the downwind side too, does that not help you keep it straight? What I miss about flying by mouse since buying a joystick, is the stability. My mouse once the plane is set flying straight and level used to allow me to put the kettle on and make a cuppa and wander back 5 mins later with nothing amiss. My stick won't do that! Slight hint to stick makers, incorporate that mouse attribute into your next design. You'll have a winner! Reckon your new mouse is a Micky Mouse or else FG has the heebe-jeebies.
Cheers, sim
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Re: Crosswind takeoff and landing, Cessna 172p

Postby dany93 » Mon May 31, 2010 2:35 pm

Hi, Sim
sim wrote:A touch of brake on the downwind side too, does that not help you keep it straight?

I've never heard of or read that (I'm also in instruction on a very light real aircraft). I understand it can counter the tendency to turn nose to the crosswind during rolling for takeoff, but to apply one brake when you wish to accelerate is a difficult compromise .... Moreover, control by one brake can help turning at very low speed, but I'm afraid it is not very accurate, even dangerous, at high speed. And you have to combine it with accurate ruddder control .... I think that if you are rudder in the corner and obliged to push on a brake to counter weather cock effect, you are close to or out of the crosswind limits of your aircraft: landing may be even more tricky.

What I miss about flying by mouse since buying a joystick, is the stability. My mouse once the plane is set flying straight and level used to allow me to put the kettle on and make a cuppa and wander back 5 mins later with nothing amiss. My stick won't do that!

Does your joystick have two pairs of buttons left? On mine, I've allocated two buttons for elevator trim, and two others for ailerons trim. Each trim is of course dependent on present thrust and speed, but you can adjust them to avoid pushing permanently on the yoke. You can go straight and level enough for a while (don't abuse!). If you are interested, the lines are :
Code: Select all
 <button n="2">
  <desc>Elevator trim up</desc>
  <repeatable type="bool">true</repeatable>
  <binding>
   <command>property-adjust</command>
   <property>/controls/flight/elevator-trim</property>
   <step type="double">-0.001</step>
  </binding>
 </button>

 <button n="3">
  <desc>Elevator trim down</desc>
  <repeatable type="bool">true</repeatable>
  <binding>
   <command>property-adjust</command>
   <property>/controls/flight/elevator-trim</property>
   <step type="double">0.001</step>
  </binding>
 </button>

 <button n="10">
  <desc>Aileron trim left</desc>
  <repeatable type="bool">true</repeatable>
  <binding>
   <command>nasal</command>
   <script>controls.aileronTrim(-0.5)</script>
  </binding>
 </button>

 <button n="11">
  <desc>Aileron trim right</desc>
  <repeatable type="bool">true</repeatable>
  <binding>
   <command>nasal</command>
   <script>controls.aileronTrim(0.5)</script>
  </binding>
 </button>

Cheers

Dany
Last edited by dany93 on Mon May 31, 2010 11:45 pm, edited 2 times in total.
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Re: Crosswind takeoff and landing, Cessna 172p

Postby MAKG » Mon May 31, 2010 3:10 pm

In the default configuration, my joystick uses the hat for rudder and elevator trim, if the "shift" button is pressed. Nice feature; very quick and intuitive. It's a Saitek Syborg EVO Force.
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Re: Crosswind takeoff and landing, Cessna 172p

Postby dany93 » Mon May 31, 2010 11:38 pm

Fine. And you don't need more buttons.

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Re: Crosswind takeoff and landing, Cessna 172p

Postby sim » Tue Jun 01, 2010 2:49 am

Sure Dany, does sound daft braking on one side during take-off but it does the trick if you haven't gathered enough speed for effective rudder to yet counter X-wind. After all on tail-draggers it's quite normal to brake either side to control taxying direction. As you gather speed on take-off and gain better rudder control you naturally ease-off this braking technique! I have used this X-wind method on real planes but it wasn't always possible, some like the Tiger Moth had no brakes!
Use my HAT for elevator/aileron trim using trigger as modifier as otherwise it pans views.
Cheers, Sim
Hi Ohneale, hope you are learning no bad flying habits from me!
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Re: Crosswind takeoff and landing, Cessna 172p

Postby MD-Terp » Tue Jun 01, 2010 3:10 am

sim wrote:Use my HAT for elevator/aileron trim using trigger as modifier as otherwise it pans views.

On my stick configuration, because I'm not big on "modifiers", I use the hat switch as elevator and rudder trim, and have several other buttons set to look around with when needed. My trigger is my mic push-to-talk. :)
Cheers,
-Rob.

"Retired" from FlightGear involvement as of July 2010.
viewtopic.php?f=3&t=8809
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