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I had requested clarification on an answer to the question, How do I keep a C172 straight on the centerline during landing/rollout? I did not comprehend how pulling back after touch down provides better steering, the reply to my comment was:

The nose gear won't be off the ground, it will just have less pressure/force on it. The oleo strut won't be compressed, and the wheel will have an easier time turning side-to-side smoothly.

But,

  1. Isn't an uncompressed strut (or lightly compressed) limit/lock the steering because of the nose gear centering cam mating?

  2. AFAIK, at least for cars, better steering happens when the front axle is loaded more, whether mechanically or aerodynamically (front-end downforce).

  3. In jet-liners, pushing forward on the control column after landing (or during takeoff roll till about 80 knots) to firmly stick the nose gear is in many SOPs for better control (type dependent; degree of pushing varies). Boeing 777 example:

    On touchdown, take positive action to lower the nose gear to the runway and maintain moderate forward pressure on the control column to assist in directional control.

So what am I missing? I don't presume to know more than the above 3 points, after all suspension engineering is not an easy field (with the big shots working for the big racing teams).

Let's limit the scope to light GA planes (in tricycle configuration, of course).

I'm not questioning the validity of the technique, rather inquiring about the physics involved, perhaps there's more to it than the strut?

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  • $\begingroup$ I'm not sure this is the answer, but at higher speeds having back pressure means you are steering more with the rudder than the wheel, which is a good thing. As your speed declines, the weight transfers to the front wheel which is also good. You don't want to have a lot of front-wheel authority at higher speeds because if you've ever seen an over-jealous kid on a tricycle take a corner, you know that a tricycle tips easily, planes can do the same. It is also a good habit to have for rough fields. $\endgroup$
    – Ron Beyer
    Feb 15, 2019 at 15:06
  • $\begingroup$ Notice 777 jet cannot benefit from propwash and must reach 80 knots for rudder to be effective. $\endgroup$
    – Robert DiGiovanni
    Feb 15, 2019 at 15:57
  • $\begingroup$ @RobertDiGiovanni - You make a good point, may I recommend adding it to your answer below? $\endgroup$
    – user14897
    Feb 15, 2019 at 16:09
  • $\begingroup$ Many light GA aircraft don't even have nosewheel steering, diff brakes + rudder only $\endgroup$
    – pericynthion
    Feb 15, 2019 at 17:05
  • $\begingroup$ @Robert DiGiovanni: I don't think a 777 really qualifies as a light GA aircraft, though :-) $\endgroup$
    – jamesqf
    Feb 15, 2019 at 23:54

2 Answers 2

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Pulling back on the yoke does not improve nosewheel steering. If there is enough elevator effectiveness to hold the nose off then there will be plenty of rudder authority for directional control.

Not all airplanes are the same of course, but the Cessna 172 you specifically mentioned has a tendency for the nosewheel to shimmy at high speeds. Holding the nose off as long as possible reduces the annoying vibration and stress on the nose strut. It also prevents the pilot from over controlling.

As the elevator looses effectiveness so too does the rudder, and once the nose falls through direction control is maintained through nosewheel steering. Ideally this transition is smooth and virtually transparent to the pilot since rudder pedals are used for both.

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  • $\begingroup$ "Cessna 172 has a tendency for the nosewheel to shimmy at high speeds". That can be improved with shimmy dampener and other nosewheel parts servicing, and replacing the dampener with an elastomer filled dampener can also do wonders, such as lord.com/products-and-solutions/vibration-and-motion-control/… $\endgroup$
    – CrossRoads
    Feb 15, 2019 at 19:19
  • $\begingroup$ Good point. Just mentioning it as a better reason for holding the nose off than a questionable improvement to the effectiveness of nosewheel steering. $\endgroup$
    – Michael Hall
    Feb 15, 2019 at 19:29
  • $\begingroup$ If the plane is heavily loaded tho, it may not be possible to hold it off as long as when lightly loaded - and then you may have long rollout with lots of shimmy, which will not improve by itself. Nosewheel balancing, or replacement of tire and/or tube, replacing bearings in strut parts, filling the damper, replacing the damper, these can all help. $\endgroup$
    – CrossRoads
    Feb 15, 2019 at 19:33
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Main point here is with cars, the front wheels do to the steering and there for benefit from weight to reduce skidding. On a plane the rudder does the steering, even at taxiing speeds from propwash, and the mains assist through differential braking. The front wheel and strut are not designed to take side force and exist mainly to prevent prop strike and to allow the aircraft better forward vision, compared with tail draggers. You could design a very robust nose wheel assembly, but with an added weight penalty. It would also affect the CG.

The rudder of the 777 jet does not benefit from propwash and there for must rely on 80 knots of forward motion (airspeed) to become effective.

Bottom line, small GA plane steers without them, and they castor easier unloaded. Good habit to keep it that way with back pressure on the yolk.

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  • $\begingroup$ Not all small planes rely on castering front wheels (like a shopping cart). Many, many have nosewheels that are turned by the rudder pedals, with additional differential steering for tighter turns thru left or right braking. The pedals may be connected via springs or bungee cords, so the steering is not direct. $\endgroup$
    – CrossRoads
    Feb 15, 2019 at 17:40
  • $\begingroup$ So, less pull on spring or bungee if wheel has less load, correct? $\endgroup$
    – Robert DiGiovanni
    Feb 15, 2019 at 18:15
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    $\begingroup$ "On a plane the rudder does the steering, even at taxiing speeds from propwash, and the mains assist through differential braking." Robert, do you fly a single engine prop with a free castering nosewheel? (I never have, but I have flown a twin jet with a castering nosewheel so I have some perspective.) I don't believe that propwash at idle or slightly above is enough to allow direction control via the rudder. I don't think the mains merely assist, I thing differential braking is 99% + required. However, I will defer to anyone with direct experience. $\endgroup$
    – Michael Hall
    Feb 15, 2019 at 19:35
  • $\begingroup$ At idle, no, propwash is ineffective, and differential braking is used, a little bit of throttle can help a turn while rolling along with inside brake. $\endgroup$
    – Robert DiGiovanni
    Feb 15, 2019 at 22:32

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