Use of Parking Brake - C172
 

Hiya all,

I've been assigned to produce a new set of SOP:s for the school I am working for. The material we have now is really poor, both in content and presentation. The school's philosophy is to not deviate from the POH at all, I may add items but not remove. There arises the question about the use of parking brake in C172 (or any small plane for that matter). Yes, the POH says "Parking Brake - SET" for a number of situations incl. before start-up, before take-off and securing. But I have a few concerns if this is actually good practice or not...

I've was taught to fly in an environment where using the parking brake could have serious effects, e.g. taxying through slush that freezes the brake. So I personally don't use it extensively nor have I ever taught to do it. The students simply hold the brakes with their feet while the engine is running. Some of the concerns of always setting the parking brake I can think of:

- Since it's on the secure checklist in the POH, and the aircraft are parked outside overnight, the aircraft will certainly experience significant temperature changes which can both damage the parking brake and relieve the pressure holding it so what's the purpose?

- We're operating from a busy GA aerodrome, regularly told to expedite departures. Can easily see how the parking brake will be forgotten in this case, especially solo, unless last point on before take-off checklist says to release parking brake.

- Using the parking brake every time they stop, they may eventually rely too much on it? Until the day it fails… Good practice is of course to keep your feet on the pedals anyway.

- Maintenance issue, if it's used extensively during a normal training day with maybe five or more flights, will it eventually wear out and break? Unnecessary cost?

What are you other people's take on the matter? Of course it's always advisable to operate i.a.w. the POH, but in some cases I am not sure if the checklists in the POH are written for the type of operation that we do. Thanks for your help in advance!

Before and during startup: set and backed up by manually holding the brakes

During taxi: off if you need to stop to give way to another aircraft, ON (this is a must) on all holding points, since it's quite hard (especially for a student) to recognize that the aircraft is slowly moving - and once you pass the holding line, it's officially runway incursion. Setting the parking brake at arriving on holding point and releasing it when cleared for lineup shouldn't be a matter of checklist, but it has to be done automatically. Far from saying the parking brake item shouldn't be on the checklist - on the opposite, it should be included as the last item, but parking brake should be released automatically. If not, it's only a matter of time when the future pilot will be "in a hurry", skip over the whole or at least part (we prefer to skip the last parts) of it, forget to release the brake and the party begins. However, parking brake should not be set once past the holding point (e.g. on the runway during line-up), since you never know when you'll have to immediately vacate the runway (for example aircraft with engine failure on opposite final) - besides, the time between line-up and takeoff clearance isn't longer than 20-30 seconds. It's not that hard to step on the brakes for a minute or so when you don't have anything else to do, except to scan for traffic and listen to ATC awaiting takeoff clearance.

Shutdown: on, then released after the engine stops, since the brakes tend to get quite warm during landing (especially if you had to brake quite hard) and taxi (if you had to use differential braking). I wouldn't set the parking brake on unless the apron has a significant slope - and even then it's FAR better to use chocks.

The Cessna C 172 parking brake is not very well designed.
Over time the cables stretch and uneven pressure is applied to each side as well as system friction can cause the brakes to not fully release. For that reason I teach that the system never be used.

Trusting the Cessna Mickey Mouse parking brake to hold during runup is IMO the height of foolishness and any student that is not capable of holding the brakes while performing the appropriate checks is IMO not fit to hold a licence. Leaving the parking brake on after the flight will warp the brake discs.

My 02 cents

Hold the brakes with your feet when the engine is running and use chocks when the aircraft is unattended.

I never depend upon any parking brake. I once did in a C 310, and was very alarmed to look up and see the plane slowly moving. The parking brake is a design requirement, and therefore, provided with the aircraft, whether affective or not. Few I have ever used worked in a way which would make me want to rely on it. If they do hold at low power, they still might not at high power, which can lead to a really nasty surprise at the worst time during a run-up!

I believe that "setting" the parking brake, and then going on with other actions, without monitoring the aircraft for motion, is very foolish. It also defeats the intent of "being at the controls" while the engine is running. If the aircraft is creeping forward on a slipping parking brake, and you the pilot don't stop it, you are responsible for anything going wrong - you can't blame a poor parking brake. Use your feet.

I respect the dilemma of being told to not remove anything from the manufacturer's checklist, while creating your own. I suggest that the phrase "Apply brakes" or "Insert wheel chocks" as appropriate be used.

Yes, Cessna parking brakes will become less effective with use. They can also bleed down, so they are not at all suitable for any length of time. Their use will cause strain on a "loc-o-seal" component in the master cylinder, which will eventually decrease pedal brake effectiveness. If you leave a parking break on, and someone moves the plane, something could get damaged. If it is applied, and then does not release fully (which certainly happens) and goes un-noticed, you'll get a longer takeoff run, and lots of brake wear/damage. If you get airborne that way, and then land again, it's even worse.

So I never use them (except to test at annual inspection time). Why are they there? To satisfy a design requirement, not an operational one....

Read posts 3 & 4 and take note.
Don't add anything more to your list.
Keep things nice and seemples.

Thanks very much for your replies, it sure gives some useful insights. I think it's agreed among instructors that none should trust the parking brake and still use foot pressure. Beside that though, I can imagine an increase in maintenance write-ups regarding the brakes. Our aircraft do fly 5-6 flights a day so it will involve a lot of use of parking brakes. Talking to our maintenance department they agreed that overuse of the parking brake may lead to excessive wear which makes the brake itself less efficient. Then it will always be the human factor with a forgotten/not fully released parking brake, which can be counterproductive to safety. Oh well... I guess the persuasion have to continue :ugh:

Driver,

I will add to my thought, that if management is requiring that all the Cessna checklist items are being carried over to your company checklists, and this is capturing the use of the parking brake at certain occasions, you might present the other side of the situation to them....

If your company procedures require the pilot to apply brake pressure at all times no motion is desired, and your checklist does not make any statement with respect to the use of the parking brake, you just evaded being assigned responsibility by the pilot of a errant airplane, who would surely say: "But I applied the parking brake, as the checklist said, and it still moved, it's not my fault!".

If you need more cheklist insight, PM me. Writing Flight Manual Supplements and checklists is a part of what I do, and I have some background information which might be of help to you...

I pulled the 172 into the hanger the other day, with the parking brake on. Did not notice any difference in the effort required!

One the other hand, I was onced asked at the last minute to deliver a 172 up to the other airport. As I started up, in rather a hurry, and tried to taxi. I noticed resistance. I looked out, and the mainwheels were not turning. The aircraft was, however, sliding nicely on the wet grass.

I knew the aircraft "had" to be delivered, and the owner had already sent away the mechanic, to meet me at the next airport. I was moving, and it was a grass departure, and a grass arrival, so off I went. Once moving, I hardly noticed a difference, and was easily airborne.

When I landed, I taxied up to the beginning of the paved apron, and shut down. The mechanic came out and asked me why I had not taxiied all the way in. I handed him the keys, and said "you'll find out shortly".

Another of my long list of reasons to know that a recently maintained aircraft is the one to most likely need a preflight inspection!

Parking brake on a 172?

Do you mean that handle thing you pull out from under the panel that you hang your headset on when vacating the aircraft?

That is what I assumed it was for as it was b*gg*r all use as a parking brake. :rolleyes:

Unless you have a new airframe most of them are so worn out they slip off the ratchet and unlock by themselves anyway.

...and drop your expensive headset on the floor....

Ah there speaks the voice of experience me thinks:)

But more seriously the 172 park brake is not that bad compared to some others in the GA world.

Generally on most types I only used to set the park brake on after engine shut down. Even then I would prefer to tie the aircraft down or chock the wheels. I have seen too many examples of hot brakes cooling down and letting go. Worst I witnessed was a hopelessly inadequate pilot trying to stop his King Air 200 rolling downhill by hanging on to it. :eek:

One of the exceptions was the Yak 52 which had an industrial bicycle type hand operated brake on the stick, no foot brakes. If I had to stop for more than a minute or two I would raise the simple metal latch to hold the brakes on. To hold it manually for much longer required hand muscles like Arnie - Schwarz - his - name.

My opinion only, others may differ

I have little time for the parking brake in many GA aircraft. The 152 is another example. Set it and it will (may) hold. Breath in the general direction of the rudder pedals and there is a chance the parking brake will release.

But it's OK, we accept these quaint idiosyncrasies because it is a Cessna and therefore it must be a damn good piece of technology :rolleyes:

Cessna singles don't have good park brakes. However, I'm thinking of another reason why not to use them. Our instructors tell students never to use them, for a long time I didn't know why. Because it's in the POH, I started doing it sometimes when the apron was not level for example.
One day I was taxiing for takeoff and noticed a steering problem. the aircraft did not turn right anymore with full rudder applied. I aborted takeoff, shut down the aircraft with 1 wing still on the rwy...Manually pushing the aircraft was not possible. 5 minutes later the mechanics came and pushed the aircraft back without a problem...
Seemed that 1 brake was still applied, a good knock on it with a mechanics boot and it let loose. And when I told our instructor what I experienced he told that was the reason why his students may not apply PB. He told a solo student had also had a dragging brake, didn't notice it and took off. During that takeoff the brake overheated and got on fire.

During an early checkride in a Piper in a busy circuit my instructor suggested the use of the handbrake to allow a faster slowdown allowing us to take the first exit freeing up the runway for those close behind. It worked a treat but one needs to be careful.

However, in Cessna-land it was company policy to completely ignore the park brake on all models with a tailwheel; without exception.

What a ridiculous and stupid suggestion. Normal brakes are perfectly adequate, and if your instructor was suggesting the park brake would lock the wheels, then he has both a poor understanding of how a vehicle brakes, and a complete disregard for the state of the aircraft's tyres.

Forget the aircraft behind you. If they're that close, they'll probably go around. They are not your problem - land your own aircraft, not the one following you.

Alot of us have flown a slab wing cherokee that only has that handle brake as the only form of breaking.

It takes a bit of getting used to but actually promotes good braking practise because it is virtually impossible to ride the brakes and not notice.

Those daft handles are not only parking brakes they are also emergency brakes for when the servo cylinder pisses all its fluid out onto your shoes and makes the brake pedals go all flappy on some types.

Speaking of brakes, I have on, 3 occasions, had brakes which worked on the taxi out fail during the flight (loss of hydraulic fluid twice and air leak). I always check the brakes on my prelanding checks.:ok: