Hi welcome to the hangar and happy new year I thought I'd start our new year
off by diving right into some maintenance and we're going to look at wheels and brakes today
this is a very important aircraft system but one that often gets neglected and overlooked.
There's a number of publications that can help us out with the jobs and maintenance around landing
gear specifically the wheels and brakes and I'll put the link for those in the description below.
We're going to take a look at the wheels and brakes on the Acroduster behind me
and we'll also have a look at a few items on the workbench to see where things can go wrong
and how we fix things when we do find issues. I hope you find this really helpful
and we'll get stuck right into it. Tool wise
basically we're just going to need some basic hand tools for the job today we'll need a few
different sizes of wrenches but nothing outside of your standard kit. We will need to be able to
pull and remove some cotter pins so these are kind of the three tools I normally use for doing those.
We will need a torque wrench as well putting the wheel halves back together and remember especially
if you're working on a certified aircraft that torque wrench is meant to be calibrated annually.
I have the advantage of running a business so all of my stuff does get done but but if you are doing
your own maintenance on a certified aircraft under the provisions allowed by certain regulations you
still do need a calibrated torque wrench for doing things back up again. So we need torque wrench and
we'll need a screwdriver and a couple of sockets okay very few tools needed there in addition
to that we're going to just check and clean the wheel bearings so we've got some appropriate rated
AeroShell grease and some cotter pins to replace what we remove from the gear. okay let's go ahead
and get our wheel pants removed. I got a little tub here to catch and look after our hardware.
Okay 7 16 we'll remove our two bolts here that removes the backing plate from the caliper which
will allow us to remove the actual wheel itself. Really good to see that these bolts nice and free
definitely corrosion issues here with cad plated or once the cad plating has worn off being inside
a magnesium housing causing dissimilar metal corrosion. I do quite often find these completely
seized and stuck in the housings very difficult to remove there if things have been neglected for a
long period of time we will also require a floor jack or some way of lifting the aircraft. Lifting
aircraft my least favorite job so certainly we want to make sure that we're doing that
safely and most certified aircraft again will have instructions in the maintenance manual on how to
jack and raise the aircraft so you want to have a look at those sections there to make sure that
you're doing it without damaging anything. Now that we've got the aircraft jacked up before I
remove the center nut I like to deflate the tire just in case we have any issues with the actual
bolts that hold this is a split rim so the bolts hold the split rim together
if we've removed all the air pressure we can't have any problems certainly before undoing the
the rim bolts we must have the pressure removed otherwise you're going to hurt yourself!
So just a little stem removing tool obviously you could just deflate it as well. You will
need a large set of channel locks to remove the axle nut. I will have to remove the axle
extension to remove the nut. Different airplanes are going to be done different ways a lot of the
Pipers the axle extension is just held in with the cotter pin that holds the axle nut so once you've
removed that cotter pin you'll be able to slide it out. This one has a very long axle extension
with a threaded nut on the opposite side and and that's what holds the wheel pant there so that's
a little different but that's just the way this one's done. Once that's out the way
we can remove our wheel and inspect our tire brake and the rest of the pads there as well.
I like to put something to support the aircraft especially if there's people around that might
be bumping it so it's not just sitting on the jack. So a nice box or a large block of wood
something like that just to protect things while you're away from it.
Okay so we have our wheel assembly on the workbench we've deflated the tire prior to
removing the bolts which we're about to go and do right now so that we can get the disc
off. We've had a good look at this tire and we've got no cuts we've got nothing on the side
walls we've got nothing down in the actual ribs no exposed cord no flat spots so this tire no problem
there so that'll be remaining in service we'll just go ahead and change the actual rotor itself
Certified airplane you should be able to look up through the
illustrated parts catalog or through something like a RAPCO application guide
what wheel and brake is supposed to be on the aircraft failing that there is data plates
that should be on the wheel so this one's got one right here okay and
you might be able to just see it there so that tells us it's a Cleveland wheel and
it tells us what model it is what the static load rating is and it also gives us the size
that's supposed to be there as well as telling us the inch pounds to use for the torque for the
through bolts. In the Cleveland technician guide if this data plate because it's just like a foil
sticker if it's been destroyed or removed from the wheel or painted over and you can't read it
anymore you should if you know what wheel assembly you got you can look it up and you can look up
that particular wheel assembly to determine what torque it is. I have found the wrong
wheels on certified aircraft a number of times the worst was a 6.00-6 rim from
early 70s vintage 172. They were lighter casting than this one here they used smaller through bolts
that only get torqued to 90 inch pounds they have a very low static weight rating I found
one of those and the associated disc brake on a 300 horsepower retractable gear Piper Lance
with a tire that wasn't rated for the weight of the aircraft either! On top of all that they'd
also managed to assemble it onto the landing gear without a spacer on the axle so the actual rotor
was rubbing against the landing gear and it had been on the airplane for eight months when I found
it so obviously the danger there overloading the tire the rim you know blowing the tire or cracking
the rim. I have found broken rims and I have found broken castings around where the bearings get
pressed in when they're apart so these areas you really do want to be inspecting
to make sure there isn't damage so we have a good look at this this is a very heavy duty one this
is the heavier size with the larger bolts and it's on a very light airplane but I'm gonna have
a good look at it anyway so we should need a half inch for this particular model one on either side
and we'll just undo the three bolts
okay just a little bit of weight is quite often all that's needed around the edge to break it
free obviously there are bead breakers that you can mechanically do this as well. I would
not recommend using a screwdriver because it's easy to mar the the actual wheel half itself but
as I said normally very light pressure is needed and as I said I'm taking this apart
just so I can have a look and make sure I don't have any cracks or damage to the two wheel halves.
Tire and tube look in good condition so that's all I wanted to do there. Now temperature change can
cause a change in pressure about five Fahrenheit or three Celsius change in ambient temperature can
be about one percent change in tire pressure so certainly if you inflated your tires last
in the summertime and then it's -20 out you can have pretty significant tire pressure change! Okay
150 inch pounds to secure the bolts for this model and while I was installing the bolts through there
I kind of did it on a bit of an angle and was keeping pressure to keep the wheel halves
together so I didn't have them sliding around. The biggest danger there would
be pinching the tube between the two wheel halves and then when you go and inflate it
obviously the tube will not survive that okay 150 inch pounds
we'll go ahead and get the
wheel bearing on this side removed just use a flat standard screwdriver just to lift up the snap ring
and then we have normally a little metal washer with a felt disc inside it
then another metal washer I'm just going to give that all a clean and
we're just going to inspect see if wheel bearings are necessary in the near future
So we'll give that a good cleanup take a look here it actually looks pretty reasonable
clean out the race obviously pitting stains rust marks if you see anything like that in there
it's going to be indicative of them needing replacing quite often you can hear the wheel
bearings if they're bad especially on landing you know you shouldn't hear them sort of buzz and hum
as you touch down on the runway so these ones are actually looking looking to be in
in excellent condition yeah there's not a single mark on that race all the way around
very happy with how that's looking there so I'll just go ahead and and and clean that up squeeze
some fresh grease into it put it back together and then we'll do the same on the other side
now you don't have to use a grease packer like that you can clearly do them by hand as well I
just find them a very handy way of doing it and it really does inject the grease right through
the bearing and you know that you've cleaned out any dirt debris and it's very easy to keep
clean obviously we don't want to be pushing dirt into the bearing so I'll go ahead and
do the other side and get that assembled then we're ready to put this back on the aircraft
So we're back at the airplane and I'm about to go ahead and install the wheel back onto the axle
I've had a good look at the brake cylinder itself and what I've noticed is that
it appears I've actually got a hydraulic leak you can see that's wet there and
there's evidence when I look really close up there of it actually leaking hydraulic fluid
now I had inspected this earlier to determine what wheels were on it so that I could get the
appropriate pads and rotors and things like that I had a hydraulic leak at that time
that was very noticeable so I have actually had this caliper off and serviced the brake
it was in kind of bad shape and there was again pitting issues inside this slave cylinder so I
had reinstalled it with a new O-ring in the hopes that things would be okay looks like that is gonna
be a problem still so we're gonna once we've got the tire back on we're gonna go ahead and remove
the slave cylinder here and we'll have to order a new cylinder so that we can rebuild that and
and not get the pads and rotors contaminated with hydraulic fluid and have a constant leak going on.
okay so I'll remove my safety block
On an interesting side note Canada's worst aviation accident was caused by an
under-inflated tire! Now I always like to just
over-tighten these ever so slightly and then back them up to where it's loose
spinning freely I think I should say and we've got our new cotter pin here almost lost that.
We
need to put our core back in and inflate the tire in accordance with the
pilot operating handbook or maintenance manual I
could have made my life a little easier and put that back in prior to installing the wheel
Especially if you've changed the tube in the tire you want to fully inflate to the
correct pressure and then you want to completely deflate or almost completely
deflate the tire again and then re-inflate it once more and then check it within 24 hours
and that's because you can get air trapped inside
between the tube and the tire that can give you erroneous readings and let things go flat.
okay we'll lower this on the ground put our wheel pant back on then we're going to get into that
brake a bit. Okay each airplane is going to be different in the amount of access that's available
the Acroduster is very tight here with a hard line coming into the end of this fairing so
I can't actually remove this without breaking the hydraulic line. A lot of aircraft you can
actually because of flex lines get these off and and then the plate off to change pads and inspect.
This I am going to have to break which will require us to bleed the brake later
So I spring that open I need 9/16 wrench to undo here and we want to support the
end fitting which should be a 7/16 although the casting sometimes can be a little awkward
so if your 7/16 wrench doesn't fit a adjustable wrench can be an appropriate
tool to use to support that fitting what we're doing is
protecting our casting here so we don't get a crack right in the top
Okay so we've got this brake caliper off and we can see the
pressure plate here we'll just slide out of the way and we can inspect. Its not got
wear marks on it but there's actually quite a lot of life left in that pad
but it's definitely had some hydraulic fluid on it so I'm kind of tempted to change it anyway.
Actually it doesn't look that bad perhaps what we'll do is we'll do a
separate video to finish up this this brake job and in that video what we'll look at is
is is bleeding the brake changing the pad with the riveting tool to rivet new ones on reinstalling
this bleeding the brake system and and sort of finishing up. I think we'll finish that
in a second video that'll keep things a little shorter we actually got the wheel change complete.
Well I hope you found that helpful in inspecting and going through checking
out your wheels and brakes for a change as I said we'll finish up the actual riveting on and off of
new pads in a separate video and we'll take a closer look at that
cylinder slave cylinder as well to determine whether it's actually leaking and causing a
problem and if we need to buy a new one there so we'll finish things up in another video
please leave your comments below we'd love to hear from you hope you're all going to get lots
of flying done this year stay safe happy tailwinds and we'll talk to you all soon.
On the workbench here I've got just a couple of items I've got an old disc brake here this one
is about ten thou before being under limits but it does have some fairly heavy corrosion and pitting
in the surface of the rotor and that was causing some inadequate braking forces and that's why
that was removed there next to it here I have a wheel cylinder Cleveland wheel cylinder this was
removed from a Cessna 172 and it's very typical of the sort of problems that occur with the aircraft
it has deep pitting which is going to be very hard to show you with the light and the camera but it's
got deep pitting in the wall of the magnesium and what was happening was the piston was starting to
leak and weep hydraulic fluid and you couldn't get a seal because of that corrosion issue
the fluid quality was very poor in this brake so definitely a neglect there had caused issues
now furthermore this particular unit did actually have a crack in the
housing near the top here just in the side where the AN fitting that brings the hydraulic
fluid from the master cylinder was attached so there was also a crack in that housing so this
entire thing needed replacing. Here I have a plate for the cylinder so this is
our backing plate here that holds one of the brake pads and the holes on this have been quite badly
butchered probably by not using the correct tools most likely using a drill
and unfortunately what's happened now is you can't get a good seal
on the rivets when you squeeze them and you get movement in the brake pad itself so that's
not acceptable so there's a couple of items that often go wrong with the actual brake side of thing