Cherokee Bankstown 3-10-20

[Bosi72]

I had gusty xwind landing yesterday.. As per normal, wing-down, a bit faster ~70 approach with 10deg flaps, but the gust was still strong.. All the way along the final, the aircraft was experiencing sudden drops, then flying, then drop, then on threshold engine goes idle and flaring, then (unexpected) drop and bang on the ground 🙂 

Then, the aircraft still wanted to continue flying, but I managed to keep it on the ground whilst balancing by extending flaps (hand lever flaps between 10 and 40deg) and gently applying brakes whilst keeping the wing down and rudder on the centerline..

Full arms/hands/legs/feet and brain work, but that feeling after the workout - priceless 🙂

Cheers

 

 

[RFguy]

How to Jab pilots manage getting onto the brakes in a hurry just after touchdown in a pressing condition ? (considering brakes  are in the middle). I have long arms and can reach them easily enough I have found , it is NOT a nature maneouver !,   - I will miss the differential  toe breaks of the Brumby for sure....

[kgwilson]

Hand operated brakes is one of the few drawbacks of the Jabiru and also a lot of other recreational aircraft. Toe operated differential brakes are way better especially in gusty crosswind conditions but all the time in fact. Combine that with a castoring nosewheel and you can spin around with ease in your own length.

[facthunter]

Castoring nosewheels don't handle crosswind taxying very well, and ALL nosewheels can experience shimmy. Very few U/L aero brakes are good enough to be called brakes.  and wheels are too small and the brakes get hot. A mate of mine destroyed a plane from a brake fire. Use them sparingly.. I "lost" a brake on one side on a straight tail 182 at Sydney (Mascot) in a strong wind taxying...Don't count on your planes brakes too much. That's the message. Nev

[kgwilson]

My Matco brakes are excellent. I can lock the wheels up on seal though doing this is not efficient & wears tyres out. I have never experienced shimmy with my setup though plenty do and I don't have problems taxiing in strong crosswinds. Maybe I'm just lucky.

[Jase T]

Hand operated brakes are a real PTA in my opinion. Manys the time I have asked a passenger to hold the stick all the way back for me while we taxi along so I can have 2 hands free for taxiing! But it is what it is! 

[Bennyboy320]

4 minutes ago, Jase T said:

Hand operated brakes are a real PTA in my opinion

I agree on the Jab, however on the Foxbat with the Y stick they very user friendly.

[RFguy]

I've seen pilots rest their forearms  in the Y (for control) on  the Jabs (later Jabs have the dual ctl Y stick) and hold the brakes with their hand. didnt look too hard. Other Jab pilots I have seen right over with the throttle hand. depends what is going on I guess.

needs a slave actuator  somewhere. .. switches on rudder pedals driving actuators I dunno. 

anyway, sorry, off topic !

 

That discussion is for another  forum topic .

 

 

[turboplanner]

1 hour ago, RFguy said:

I've seen pilots rest their forearms  in the Y (for control) on  the Jabs (later Jabs have the dual ctl Y stick) and hold the brakes with their hand. didnt look too hard. Other Jab pilots I have seen right over with the throttle hand. depends what is going on I guess.

needs a slave actuator  somewhere. .. switches on rudder pedals driving actuators I dunno. 

anyway, sorry, off topic !

 

That discussion is for another  forum topic . The J170 has a short lever and small brakes, and ergonomics where it would be better to start again. You get used to it, But flying a Cherokee with toe brakes and a big wheel brakes that will skid the tyres on dry bitumen (and no that's not what you do) and stop on a dime, you have way more options than the Jab if things get tight; for a start differential braking so you can skid into a ground loop rather than have to steer around into one etc.

 

 

You are, but something useful always comes out.

[RFguy]

The Brumby i have been flying has diff toe brakes. it's an ideal task for toes !!!! that are otherwise unused. I like the idea of using all my body parts.

 

[RFguy]

An big improvement to the Jab would be simply dual levers right next to each other and dual cylinders.... looks a bit like thrust levers of a twin. Should be able to 3D print a pair of levers in fibreglass improved Nylon on a Markforge.....  Project # 7.

 

 

 

 

[kgwilson]

Toe differential brakes would be a bigger improvement along with decent discs. The discs they have look like they come from a bicycle, but there is a weight saving I suppose..

[RFguy]

good weight saving would come from replacing the cast or pressed (depending on which ones you have) steel rims with a Titanium alloy , 3D printed using SLS.... you could build in some fan blades to assist cooling slightly.

 

And there are more advanced discs. Much of the Jab appears to be designed so you can get the parts anywhere and the parts being fairly non critical, low performance spec (like those brake discs). 

 

Need to study what is done for toe brake  implementation in other airplanes. many options. Electro-mechanical assist to generate pseudo-differential not out of the question- done in F1 cars. 

3D print some internal spring flipper lever - pedal that would slide over existing pedals, with electronic inclination sensor (to sense the tilt on the pedal) , take to a controller and drive an actuator for a master master cylinder setup. not as hard as it sounds. In case of fault turn power off to actuator and existing system (centre brake) is unimpeded and functions normally. 

 

I'll start a thread on this when I get the airplane.

Edited October 9, 2020 by RFguy

[Thruster88]

18 minutes ago, RFguy said:

good weight saving would come from replacing the cast or pressed (depending on which ones you have) steel rims with a Titanium alloy , 3D printed using SLS.... you could build in some fan blades to assist cooling slightly.

 

And there are more advanced discs. Much of the Jab appears to be designed so you can get the parts anywhere and the parts being fairly non critical, low performance spec (like those brake discs). 

 

Need to study what is done for toe brake  implementation in other airplanes. many options. Electro-mechanical assist to generate pseudo-differential not out of the question- done in F1 cars. 

3D print some internal spring flipper lever - pedal that would slide over existing pedals, with electronic inclination sensor (to sense the tilt on the pedal) , take to a controller and drive an actuator for a master master cylinder setup. not as hard as it sounds. In case of fault turn power off to actuator and existing system (centre brake) is unimpeded and functions normally. 

 

I'll start a thread on this when I get the airplane.

Glen, why not put a rate gyro coupled to brakes and rudder to stop all that pesky yawing stuff (tail wheel) on the runway. I will keep my aircraft pure and simple.    

[RFguy]

Hi  T-88.  Of course that is what is done in remote-control model Helicopters.

 

But don't you think a human does a pretty good job of that in a real aircraft ?

 

I think the remote  actuator pedals are a pretty easy implementation. Will think about it some more.. Jab doesnt have full castering nose wheel (?)  so I guess  diff brakes for turning at ends of strips is of limited value for that nosewheel. I may be wrong about the Jab nosewheel limitations. Or does it caster beyond the pedal control ?

 

 

[facthunter]

You have to stop making micro-Processors run your plane. Make it so the pilot FLYs it. Powerful brakes either lock wheels and can spot tyres or cause them to blow or impose large loads making differential braking  most use only at lower speeds. Tailwheels ARE steerable when the tail is on the ground, if it's set up correctly. Generally unless there's some propwash  once you've slowed up, the rudder would not  have much authority especially ones that are small and  have rather short tail moment arms. A dorsal fin helps energise rudders but you still need a decent airflow. Nev

[RFguy]

Dont worry Nev, per my comment to Thruster    (I said) "But don't you think a human does a pretty good job of that in a real aircraft ?"

 

there are some things the pilot should be doing. He She is not doing it all day. and humans have proven reasonable pilots.

 

However, the toe brakes on the Jab would be nice.  I'll be interested to see just how "equal" the left and right brakes  are until moderate  braking.  My guess is under heavy braking, they'll be (expected) to be similar- where max clamping force on the disc that the little caliper can muster, is applied, all things become equal. ideally. I've found pad and disc INcompatibilities more of an issue in motor vehicles than anything else. IE pad doesnt like to be teamed up with that disc.

 

BTW- no microprocessors need be involved, to nit pick :-) 

 

[kgwilson]

You don't have or need power assistance with light aircraft toe (or any other sort) brakes but it is important to set the geometry up with the appropriate ratio of pedal pressure to braking force to get a good feel for their operation from very light through to heavy brake action.

[RFguy]

Hi KG

yeah that's the thing isnt it, any toe brake solution really needs to have pressure feedback like a real pedal. cannot be just a inclinometer on a spring. needs back pressure.  I'll take a really good look at the Brumby next time I am in it. 

-glen

 

[turboplanner]

39 minutes ago, RFguy said:

Hi KG

yeah that's the thing isnt it, any toe brake solution really needs to have pressure feedback like a real pedal. cannot be just a inclinometer on a spring. needs back pressure.  I'll take a really good look at the Brumby next time I am in it. 

-glen

 

That's called modulation and is a part of the design process. The brake performance and wiindow of operation between these two aircraft is like chalk and cheese, so is the price.

[facthunter]

  You can easily smoke a tyre with Clevelands  ..IF you are serious you must have anti skid. Differential braking is a must. If you have a flat tyre on one side for instance you have to equal the drag at least. Nev

[turboplanner]

1 hour ago, facthunter said:

  You can easily smoke a tyre with Clevelands  ..IF you are serious you must have anti skid. Differential braking is a must. If you have a flat tyre on one side for instance you have to equal the drag at least. Nev

You can but there's enough modulation on the Cherokee that only a hoon would; fabulous brakes.

 

Re the anti skid, I checked the Textron Skyhawk Specification sheet, but it doesn't give much detail other than overall dimensions.

[facthunter]

You don't have to be a hoon .If your seat is not correctly  adjusted or your feet positioned optimally, you might accidently apply the brakes enough during rudder application to momentarily lock one. There's varying amounts of lift involved also as well as cross wind and it's effects,. Anti skid reduces tyre blowouts BUT our planes have LOW stall speeds remember, so don't need F1 Brakes.  Tiny wheels don't have enough room to build bombproof brakes. Brakes have to absorb generated heat and that ability is always limited even with the best. Nev