Tricycle Steering Method: Brakes vs Nose Wheel

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addaon

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Differential brakes: Pro: Can turn amazingly sharply by standing on one brake, using power. Con: Requires more active input for normal taxiing (repeatedly tapping the brake gently).

Nose wheel steering: Pro: Simple to taxi, feels very natural. Marginally less brake wear. Cons: Hard to retract, additional weight and complexity, changes rudder pedal feel.

Personally, the only two options I'd consider are either steerable nosewheel + differential brakes, or just differential brakes. I see no real advantage to implementing a steerable nosewheel and symmetric brakes, unless for some reason you really really need to use finger brakes (in which case you don't have much choice).
 

flyoz

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I fly a trigear from a grassy sloping airfield thats short . It has a steerable nosewheel and i have modified the brakes to act differentially . I never seem to use differential braking on takeoff , but landing in strong crosswinds means the nosewheel is trying to follow the rudder and if the main gear is down and the nosewheel is still up , coupled with some slope and wet grass it can get messy - i certainly use the differential brakes . One word of caution - its best only to use the brakes differentially when the nosewheel is up otherwise it can place side thrust loads on the nosewheel strut . I try to"follow" the nosewheel with the brakes when i turn during taxi to reduce that effect . Would i use the same sytem again ? - for sure .
 

GESchwarz

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Thanks for the input.

Because I've never used differential braking, I suspect that they may be touchy/sensitive on the take off and landing high speed roll. Is this a valid concern or is it, in actuality, no big deal?
 

Tom Nalevanko

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I had differential braking only on my Stallion and your concern was no big deal. You get used to the diff braking quickly on taxiing; trick is not to taxi at a very, very slow speed. On takeoff, you mostly use the rudder. On landing, don't brake differentially until you turn off on a taxiway.
 

GESchwarz

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So I take it that there are two sets of pedals, one for rudder, and one for brakes? If that's the case I'll have to see how they're arranged on the floor. Obviously this is the first time I've really looked into these controls.

Tom, you raised another question...while on the landing run, how do I select between differential braking and combined braking. I'm thinking that without some kind of selector valve to join the two sides and my brake system is set up for differential braking and I go to apply brakes, that one side is going to brake harder due to uneven foot pressure, and I'm going to do a ground loop like a tail dragger. I'm sure this sort of think doesn't happen, I'm just trying to understand how it works.
 
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flyvulcan

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I used to fly a 2 seat jet trainer that had no nosewheel steering. You get used to the differential braking very quickly. Maintaining directional control while braking, including in strong crosswinds just means applying a little more braking on one side than the other. There is generally no selection for "differential" braking, simply press one brake harder than the other.
The problem with using differential braking for directional control is that by necessity, you are using the brakes and consequently, "brake energy" considerations come into play. If your brakes are "weak", with constant use you can find that they become less effective or even ineffective.
When teaching turning while taxying, we always taught "lead with the rudder" i.e. when approaching the turn, apply full rudder in the direction of the turn, then squeeze the brake at the appropriate time to commence the turn. When exiting the turn, anticipate the "rollout" by applying full opposite rudder, then squeeze the opposite brake to stop the turn. When pointing in the correct direction, centralise rudder and release brakes (unless in a strong crosswind where you will have to apply consistent pressure on the downwind brake to prevent weathercocking).
Hope this helps.
 

Dana

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So I take it that there are two sets of pedals, one for rudder, and one for brakes? If that's the case I'll have to see how they're arranged on the floor. Obviously this is the first time I've really looked into these controls.

Aircraft brakes can be either "toe brakes" or "heel brakes". Toe brakes are more common on newer aircraft; the entire rudder pedal moves for rudder action, while tilting the pedal forward (with the too, see?) operates the brake on that side. Heel brakes are tiny pedals near the bottom of each rudder and offset, usually toward the aircraft centerline. Many pilots, particularly those who trained on aircraft with toe brakes, find heel brakes awkward; others prefer (including me) them. Toe brakes are probably better if they're going to be the primary ground steering control.

-Dana

Drink wet cement, and get completely stoned!
 

addaon

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Having flown both, but with more time with toe brakes, I find toe brakes more comfortable for actual use, but also more prone (just due to poor foot placement on my part) to accidentally landing with just a touch of brake pressure on. I wouldn't hesitate to build either (my 701 will have toe brakes, because I see no reason to deviate from the kit), or to fly either; transitioning between them is trivial.
 

BBerson

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My G109 has the right and left brakes hooked up to the rudder pedals. No need for heel or toe pedals. The brake works after full rudder is applied. It works rather well.
And a hand lever pulls both brakes for stopping and parking like an automobile.
 

addaon

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The system that BBerson describes is relatively common on designs that have twin rudders, especially rudders that deflect (each) in only one direction. Think Long-EZ and relatives. The reason it works is because it's both possible to push both rudder pedals in, and relatively meaningful; it applies an "air brake" with symmetric deflection, which transitions naturally to "ground brakes" with more deflection.

Even so, I've heard it said a couple times (this is all hearsay) by Long-EZ pilots that, for relatively steep approaches, there's a tendency to land with brakes engaged, because the detent between max airbrake (which you want for a steep approach) and initial groundbrake (which is bad) is subtle.
 

Waiter

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One very important point is the main landing gear geometry.

If the mains are close together (Theres a formula on the FAA web site), nose wheel stearing can easily cause an upset. i.e. turn to sharp and the plane tips.

However, its impossible to have an upset induced by differential braking. When you jam on a brake, if the plane starts to tip, the wheel lifts off and you loose braking in that direction and the plane imediatly straightens out.

My preferences, On large aircraft (Boeing 707) Nose wheel steering is a must. However on smaller aircraft, differential braking is advantagous.

I can lock up one wheel and turn the aircraft completely, pivoting on that one wheel.

Waiter
 

PTAirco

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I think the best of all worlds is a system used on many DeHavilland aircraft and others of the period: The brakes are applied by a hand lever and through a mixer system applied through the rudder pedals. There are no separate brake pedals, You apply as much brake as you want with the lever (Or pneumatics in case of a Hurricane or Spitfire, for example) and the brake will be applied on whatever side the rudder pedal is pushed. With the pedals straight, braking is straight. A litttle messy to design and build, but great in practice.
 

flyoz

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I use heel differential heel brakes . The heel is a natural pivot point and can stay fixed to the floor during rudder and braking application . Another benefit is you are not placing a force on the rudder assembly as you do when applying toe brakes . Most people at first seem to dislike the look of heel brakes , but after a little taxi experience they soon get the hang of it . The application of differential braking and braking simply comes naturally and IMHO are much easier to control than toe brakes .
 

fleetstreet

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I'm going to show my ignorance here: What's wrong with the way production aircraft steer and brake? Toe brakes for individual mains, nose wheel steering in conjunction with rudder. You can't spin the plane in its own length as you could with a castoring nose or tail wheel, but you can turn pretty sharply with, say, left rudder and left toe brake. Staying off the brakes during landing just involves teaching yourself to keep your heels on the floorboard. I flew some of the old Pipers that had a hand lever for braking both mains simultaneously. Never could get used to that.
 

addaon

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Fleetstreet, nothing wrong with it, and it's what most of us are used to. And you can still spin around pretty quick by flooring one brake and using enough throttle to lift the nose, on many planes. The main downside is complexity (a steering nose wheel is always going to be heavier than the same gear castoring; similarly, two hydraulic cylinders is twice as much to break as one). Certainly it's not a terribly complex system, but I think it's reasonable to consider if it's necessary for a particular design. Either system alone (differential brakes or steerable nose) may sometimes be adequate, and if so, may end up with a lighter and simpler plane. That said, any design of mine has both.
 
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