Taxi steering. Brakes or Rudder or both?

So, I wanted to get an idea of what some of you do most of the time to steer during taxi. My other airplane is a Hawk XP, and because it has the nosewheel steering, I rarely use differential braking during taxi. If the crosswind is not too stiff, I can usually steer my 9A during taxi with just the rudders and stick all the way back. However, I sometimes find my taxi speed is quite high to maintain some level of rudder authority. I have already had the experience of overheating the brake system and losing the brake fluid during a long taxi (back when I was still only using differential braking to steer). I have since gone the Viton "o" ring and the high temp brake fluid route. I don't quite know what my taxi speed is because my Skyview does not display slower speeds. However, I do know that it is much faster than what my CFI back in the day told me to never exceed. I'm afraid, one day, a ground Controller is going to call me out and radio me that he has not cleared me to take off in the wrong direction on that taxiway...

Any feedback out there to keep brakes from overheating during taxi, particularly at those long C and D taxiways?

Idle RPM ?

I don't have a 9A or any A model, but speed/taxi /heat issues can affect all RV models. I have a -4 and keep an eye on my speed just as you. What is your idle speed? RV's roll so easy anyway, and you need your idle speed as low as possible. I have a fixed pitch wood prop and idling below 700 is difficult and still pulls the plane. You may be able to get yours down below 600 RPM and help your situation. I often slow rapidly to a crawl, then coast back up and repeat as needed, rather than drag the brakes on long taxi. Also, I lean as much as possible to prevent fouling of the plugs at low RPM.

Bill, ditto on the lean as much as possible. The issue that I find is that if I go too slow, i just do not have enough rudder authority to steer without brakes....

mikerv9a said:

Bill, ditto on the lean as much as possible. The issue that I find is that if I go too slow, i just do not have enough rudder authority to steer without brakes....

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Remember that if you’re ‘taxiing back’ (e.g., taxiing with a tailwind) there will always be a ground speed where there is zero wind over the rudder. Since you mentioned excessively high taxi speeds, have you tried the opposite (e.g., taxi very slowly)? You will then need to use opposite rudder with a strong tailwind. As suggested above, ‘stabbing’ at the brake, then letting it roll free and cool, seems to work better than continually dragging it.

I try not to use my brakes during taxi and one thing I've found to help the rudder steering is a little blast from the prop using the throttle. It's amazing how much prop slip-stream helps when I need a little correction, already have the rudder deployed and increase the throttle momentarily to correct.

-Marc

BobTurner said:

Remember that if you’re ‘taxiing back’ (e.g., taxiing with a tailwind) there will always be a ground speed where there is zero wind over the rudder. Since you mentioned excessively high taxi speeds, have you tried the opposite (e.g., taxi very slowly)? You will then need to use opposite rudder with a strong tailwind. As suggested above, ‘stabbing’ at the brake, then letting it roll free and cool, seems to work better than continually dragging it.

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This concept of LARGE and RAPID rudder inputs applied as soon as the aircraft direction starts to deviate from the desired direction is key to successful taxiing without excessive braking.

Likewise for the recommendation for a short stab of brakes to induce movement in the proper direction. Still, if your rudder pedal isn't at max deflection already then you haven't yet reached the condition where brakes are required. Rudder to max... still not enough steering? Then add a jab of brake.

EDIT: Those who know me will know I don't own an RV but rather a Glasair Sportsman. The technique mentioned above is very much brand agnostic. If the airplane has a castoring nosewheel, the technique mentioned above is applicable. Note the Sportsman has a huge vertical fin and rudder in order for the aircraft to be well suited to stable flight when fitted with floats and amphibious floats. That giant vertical fin adds to weathervaning during ground operations. With this being the case one is best served by "fast feet" when taxiiing in trike configuration.

Check the nosewheel break out force. Sounds like it might be too little if there's lots of wandering.

Personally, I do brake 'stabs' which seem to get the nose wheel cocked over to wherever it needs to be, and it will stay there for a while.

Rudder is for yaw control, and when we are steering on the ground, we are yawing.
For that reason, my opinion is that the primary steering control on the ground is the rudder. In instances where full rudder is not sufficient, then you add brake to supplement. This saves on brake wear.

There are instances where the Rudder won’t be anywhere close to sufficient, such as in really strong cross winds. In those instances, I usually allow a little bit of S turning/weaving on the taxiway and stab brake intermittently to get the airplane, turned towards the downwind direction, and then let it swing back slowly.
The critical thing in this type of situation is that you don’t constantly drag a break for a long period of time. In a severe case, this can severely overheat the break, and potentially cause the wheel pant to catch fire.


Has already been mentioned, there can be cases where, while taxiing downwind in a strong wind, using opposite rudder, can get you a turn in the direction that you want, but I have only experienced this situation may be a couple of times in 30 years flying tri gear, RVs.

Thanks, great feedback! And yes, I adjusted the breakout force on the nosewheel during the last CI upward and the steering improvement was very noticeable.

mikerv9a said:

However, I do know that it is much faster than what my CFI back in the day told me to never exceed. at?

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For a pre-solo student, that usually applies, but like many procedures and techniques it’s fine to be scale it to the situation and your experience.

On my 6A it's "jabs" of brakes or throttle. Anything but staying on the brakes. Not even light pressure. I'm on them or not.

mikerv9a said:

I don't quite know what my taxi speed is because my Skyview does not display slower speeds.

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Mike,

Off topic. My SkyView Touch shows low ground speeds while taxiing. I'm curious as why yours does not. Maybe you don't have the Ground Speed widget activated? Here are a couple of examples.

10 MPH GS:



14 MPH GS:

Carl, you're right I do get the GPS calculated ground speed on the Skyview and 650xi. I should have stated: IAS. Neither of us show the IAS. I figure that the IAS would give me a better predictor of rudder authority...

As mentioned above, don't hold a brake continuously in a crosswind as this can lead to brake overheating. There may be situations where a S-turn is the result of deliberate intermittent brake application. Nothing wrong with that, some taildraggers do it all the time for over the nose visibility.