Agusta A109E brake system

[Dick Smith]

I’ve owned an Agusta A109E for about 5 years and I’ve noted that the park brake system pressure bleeds off over time. That is, if you put on the handbrake when on the ground, the pressure bleeds off and there are no brakes at all.

As the aircraft is on wheels, I’m wondering if there have been incidents or accidents where the pressure has bled off and the aircraft has then rolled into something.

It seems amazing to me that the design should be this way. In fixed wing aircraft such as Citations and Caravans, the hand brake actuator actually closes the hydraulic lines and the pressure remains on.

I look forward to comments.

[Bushrat]

lots of fixed wing aircraft all the way up to A380 have excellent parking brakes....but you won't see very many parked without wheel chocks....my 2 cents

BR

[bellsux]

At the factory they did explain this to me and has been designed that way since the A109A. No big issue as long as you put the wheel chocks in. It runs off the electric hydraulic pack so power has to be switched on to charge up the parking brake prior to removing the chocks.

[helopat]

At the factory they did explain this to me and has been designed that way since the A109A. No big issue as long as you put the wheel chocks in. It runs off the electric hydraulic pack so power has to be switched on to charge up the parking brake prior to removing the chocks.

Sorry to disagree. I fly the 109E and there is no electrical hydraulic pack on the aircraft...you must start the aircraft for the hydraulic pumps to work...this in turn recharges the relevant hydraulic accumulators. The bottom line is that the parking brake can become ineffective over time.

Chocks...thats the answer.

HP

[bellsux]

I stand corrected then.. so no hyd pack in the E just the accumualtors.

[Dick Smith]

Yes, I always use chocks but it is amazing the number of times I’ve seen a 109E parked on a slightly sloping ramp without them.

The problem of course arises if you have the chock in, and you are a solo pilot. How do you start the machine to get hydraulic pressure, then get out to remove the chock?

[rotorbrent]

I always found a rock to put on the downslope side if I thought there would be some movement before I got the Hyd pressure up for the brakes. I always joked about if there were no rocks I would chock it with some of the luggage but that never happended.

As a note not in the flight manual but you could In a emergency throw the emergency accumulator valve and then you would have brake pressure to stop you if it was getting away from you on a slope start. This has stopped one or two agustas from rolling over the edge or into objects.

But I repeat this is not in the flight manual. and then I would NOT retract the gear but it would keep you from rolling off the edge of whatever.

[Freewheel]

1. remove chocks
2a if pointing downhill run alongside and hop in, flick chocks onto LH seat
2b if pointing uphill, just wait and swing yourself in as it comes past.
3. fire it up and get things going on
4. pump on the foot brakes to get it slowed down
5. when everything's stopped and with enough pressure, apply park brake and complete other checklist items


just like bump starting an old FIAT isn't it?

[John Eacott]

Dick,

Let me know when you have a suitable answer: it's (one of) the banes of operating a 109, no nosewheel lock on start up, and no brakes, if the machine is left for a day or two :uhoh:

Single pilot: one option, of course, is to put a single chock on the downhill side of a mainwheel, and leave it behind. It doesn't have to be an aviation spec chock, a hefty chunk of rock, brick or a branch would do, but don't go into questions about "what if" it clutters a hardstanding, etc, as I don't have an answer ;)

bellsux: the electric pack for the third hydraulic system was only on the 109A and AII, IIRC. The current E's and S's are off the utility hydraulics, which has a larger reservoir running to an accumulator. Common error is to see the utility hyd reservoir sight glass showing low hyd oil, without releasing pressure on the accumulator to return the level to a correct level. Resulting overfill can be a PITA :ok:

[Dick Smith]

Now we may be getting somewhere. Can anyone advise if you pump on the foot brakes without the rotor going, if it does anything? That is, will it stop the machine?

[BlenderPilot]

Having just this morning looked at the Brake System at the course in Agusta Philadelphia,

I can just say a few things . . . . .

- Always chock the wheels
- Agusta guarantees that the accumulators will hold pressure for ZERO time
- No, pumping the brakes doesn't help
- The average time I have seen the brakes hold has been around 5 hours, no more, and this comes from flying at least 5 different A109E in the last couple of years.
- Yes there have been several incidents with aircraft rolling off
- And if the aircraft ever starts rolling off when shut down, an easy way to stop it would be break the little wire and lower the landing gear to the emergency down position, that WILL stop it, of course maintenance action will be required but, no more than having the aircraft going into a ditch.

[spinwing]

Mmmm ....

Wheeled aircraft ...... should ALWAYS use wheel chocks.

Dick FYI when Agusta designed the AW139 they went to a system where the brakes are independent of the 3 other hydraulic systems and you CAN pump up the brake pressures from the pedals prior to a rotor start .... seems to work well.

Answer ..... trade up to the 139! (Ha Ha) :E

Cheers

[VeeAny]

Dick

Apart from rocks behind the wheels which I've had to do myself. If you are on an apron and don't want to leave FOD around and have no one to help you, then although its a pain and costs a start , why not start one engine, charge the utility hydraulics, shut it down, put the chocks away in the boot and then off you go albeit 3 minutes later.

Bellsux

Like HP says in the newer models there is no electric pump for the utility hydraulics. It was done away with since the Aii and pressure is now fed from the #2 hydraulic system to both the main and emergency utilties. The fluid for the utilities comes from the #2 system and is the reason why the #2 tank is bigger. As John Eacott says its a favourite reason for pilots to think there is no fluid in #2 and top it up. When the utilitiy systems are pressurised on start up some of the fluid flows into them hence the low looking level.


GS

[helopat]

Gentlemen,

This has been, quite possibly, one of the most useful, pleasant and civil discussions I've been in/on. Good advice, ideas and MANNERS.

Fly safe.

HP

[rotorbrent]

The new electrical hydraulic system option is the old A109 electrical hydraulic pack so you will have hydraulic pressure.

[TRC]

The new electrical hydraulic system option is the old A109 electrical hydraulic pack so you will have hydraulic pressure


Even so..

I know of a pilot of a corporate 109A who parked it overnight at the boss's house.

Next morning he diligently commenced his preflight. Starting at the front he opened the battery compartment and pressed the two red buttons on the accumulators to check the levels.

The helicopter started to roll backwards down the slight slope.

He had to connect the battery, unlock the pilot's door, turn the battery and the bus switches on and get the accumulators charged before the helicopter ended up in the swimming pool that was at the bottom of the slope.

The whole lot stopped with the entire tailboom overhanging the pool and the main wheels just short of the edge.

This would have been avoided, as mentioned before, by using probably the one of the least technical devices in aviation.

Chocks.

[ShyTorque]

I also fly the type, it's not a good system and the only helicopter type I know where it's a problem. I once landed at an airfield and was marshalled to park on the large and mainly empty apron. They watched me as I put the aircraft to bed with all covers and tip socks on and chocked it for overnight. About an hour later I was about to get into my taxi to my overnight accommodation when the handler came out and said they needed to move the aircraft and wanted me to sit in to apply the brakes while they towed it. I said no thanks, the brakes don't work after shutdown so if the towing arm broke I would be part of the accident with no way of steering or stopping.

"But our SOPs say the aircraft brakes must be manned whilst towing....!", came the reply.

Said I: "In which case you have two choices. Leave the aircraft where it you got me to park it, or get your SOPs changed! Or one of your chaps to walk alongside with a chock!"

"But we aren't allowed to do that, it's dangerous...!"

"More dangerous than putting someone inside a potential runaway?"

It was still parked there next day.... :ok:

The other problem is that the hydraulic rotor brake doesn't hold for long either, so there's little point leaving it "ON" after rotor shutdown. It DOES come on if you then start the engines..... once the hydraulics begin to pressurise this quickly destroys the rotor brake and other expensive parts in the transmission.. Yes, I know of a poor soul who did this on the first day (and only day) with his new boss :}

[Pandalet]

Out of curiosity, and having never flown anything with wheels, much less used chocks:

The usual aviation chocks are essentially two triangular bits of rubber, joined together by a bit of string, right? Could you not tie a bit of string to them, start the engines with the door open, then use the extra bit of string to pull the chocks over to the pilot's door? So once the brakes are pressurised, the chocks can be removed without the pilot needing to leave the aircraft?

It's not ideal, but then a parking brake that stops working shortly after parking seems pretty daft to begin with, to my uneducated mind.

[ShyTorque]

But in view of the lack of stowage space in a 109 cockpit where would the pilot now stow two oily dirty chocks and twenty feet of rope? On his lap, or on the cream leather seat? :}

There is a narrow space behind the seats but that's where the tech log, flight manuals, charts and Jeppesen's manuals are kept. I wouldn't want to wet that lot (it would always be wet, just like the tip socks and other blanks after an overnight stop).

Wherever I can, I park the aircraft facing uphill, borrow someone else's chock to put behind one mainwheel (stow my portable chocks in the baggage bay) and taxi forward off it. Or park on grass, where the wheels bed in and self-chock.

[Shawn Coyle]

I was told that you could walk the blades around to pressurize the brakes before starting.
Anyone have practical knowledge of this?

[ShyTorque]

Shawn, it might be possible but I think you'd need to be quite tall and walk quite a lot.

Who told you that - an Agusta salesman? :)

[VeeAny]

I'd heard about that too, we tried it once at an engineering base, engineer spinning the blades from the front where he could reach them, I watched the EDU we got a flicker on the hydraulic pressure gauges and got bored after about 5 revolutions.

If it does work I guess you'd need patience.

[John Eacott]

Can anyone advise if you pump on the foot brakes without the rotor going, if it does anything? That is, will it stop the machine?

Dick,

The toe brake controls are really actuator controls for the brake valves: if there is no pressure in the hyd system, they are inoperative.

I've been reading the 109S training notes (essentially the same hydraulic system as the 109E), and in every hyd diagram for the brakes and the nosewheel lock the notes show an emergency pressure line input. There is no narrative (that I can find) as to how that emergency pressure is used for the brakes or NW lock!

Using the schematic on page 3 of 29-21-3M it appears that the emergency pressure line routes via the landing gear selector valve into the triplex selector valve, but it seems to go through the landing gear selector valve first. My interpretation is that this would only give pressure from the emergency accumulator to the brakes & nosewheel in the event that the U/C lever is then moved to the emergency down after selecting the emergency system.

I suppose that you could try changing the Emergency Selector (under the landing gear lever) from Normal to Emerg when the brake pressure is zero, and see if it then charges the parking brake, but I am dubious as to how it would route through the landing gear valve. As to whether the emergency accumulator will hold its pressure any better than the normal accumulator, I don't know, but if it works, it may give you brakes to hold the machine until engine start and recharge of both hyd systems :ok:

The schematic is downloadable as a full size jpg here, (http://www.eacott.com.au/gallery/d/2990-1/29-00-3M+45.jpg) or as a pdf here. (http://www.eacott.com.au/gallery/d/2987-1/29-00-3M+45.pdf)


http://www.eacott.com.au/gallery/d/2992-2/29-00-3M+45.jpg

[helopat]

There is no reference (that I can find) as to how that emergency pressure is used for the brakes or NW lock!

John,

If you select the landing gear handle to the emergency down position you will enable the parking brake and nosewheel lock through the emergency hyd system. This only enables the nosewheel lock and the parking brake...it does not give you toe brakes. The idea is that you'll still be able to stop following an emergency gear extension using the parking brake handle. Moving the landing gear locking lever to emergency doesn't do anything except allow the gear lever to be lowered to the emergency down position.

The emergency system DOES keep its charge pretty well, but putting the gear handle down just for brakes is at best an emergency procedure. Put the handle in emergency down and you must undergo maintenance action before resetting. Also, this will only work if you've left the accumulators pressurized...if you've dumped the accumulators (pre flight to check hyd rsvr levels) then no ammount of moving gear handle or park brake lever will help.

Hope all's well down there.

All the best,

HeloPat

[hoistop]

If it is any comfort to you - I used to work on Airbus 320 jet and if left on the apron with park brake engaged, its park brake accumulator pressure was depleted in about 6 - 8 hours... So 109E is not the only one with this problem... Chock it ALLWAYS even if it is level, as machine might move under some extreme downwash from (big) helicopter landing nearby.
I am aware of one incident where an EMS (A-109K2) helicopter landed on the (inclined) road, attending a road traffic accident, and one brake released, went unnoticed, so helicopter went off road and rolled over..:(
(Same EMS operator lost another K2 skids equipped, when it skidded (skied?) downhill on a ski piste.)
Now I work on A-109E too and can only confirm that breaking safetywire and moving Emergency lever only allows you to move LDGear handle to EMER position, thus releasing pressure (if there is any) from emergency utility accumulator to PARK brake ONLY! (no toe brakes!!) And this requires maintenance action, so you can use it only to prevent something bad to happen.
To release pressure from accumulators to see the correct level in Hyd sys 2 reservoir, you have to open the little door under the nose on the right side (no tools needed) and push one after the other two buttons (one accumulator each) and keep them pushed until hissing stops with a distinguished click) Correct level is marked on the rim of the glass - not on the sightglass itself!!
Another tricky thing is oil level in transmission (not on all A-109E-depends on PN, SN) Make sure you do the correct procedure for your SN, otherwise you might easily end up with not enough oil in the system ( low TXMSN oil press caption might flicker) or overfilling it. In our case you must check level five min. after shutdown after rotor RPM decayed naturally and oil level shall be ABOVE MAX marking (max 5 mm above) in TXMSN sightglass with nearly empty in CGB sightglass (below MIN marking).
Regards,
hoistop

[ericferret]

Makes an interesting comparison with a 365 equipped with power brakes.

This has an external pushbutton switch on the rh side of the nose that allows the brakes to recharged by the emergency electric pump without entering the cockpit.

However even this might not save you.

We had a pilot leave an aircraft for several days who failed to check that there was still brake pressure before pulling out the chocks.

Passers by were treated to the sight of a very tall pilot bent almost double trying to open a side panel and operate the switch while the aircraft was rolling away.

Aircraft fine ego badly bruised!!!!!

I just wonder how on earth this system got certified in the A109. I estimate that the weight of the 365 emergency pump is about 3 pounds plus say another 3 for piping.
It uses the LH main system for fluid supply. They must have really been scraping the weight saving barrel not to add a small pump for topping up the brakes on the 109. Maybe a mod is called for.

[ShyTorque]

My rule of thumb is NEVER to pull the chocks away on a hard surface. Try to remove them only gently. If they need a pull the wheel is leaning on them....nuff said

[Phrogman]

The procedure of moving that switch to emergency and throwing down the gear handle into the emergency position to set the parking brake was applied more than once in the US Coast Guard versions of the A109E, and thank goodness it works. The aircraft were landing on a pitching and rolling ship deck and the accumulators weren't getting charged due to a bad switch (details are kinda fuzzy on that, sorry, but corrosion issues led to some weird electrical issues while underway). The pitching up of the ship wasn't nearly as bad as the sudden pitching down and the slow roll towards the hangar. With regard to the electrical pump, we had the ability to activate such a thing without the rotors turning that would charge up the brake accumulators, but it was never shown in the system diagrams, why I can't answer. The CG has terminated that lease, so I know of at least 8 A109E's with that system on them, unless they took them out upon return to the factory.

[Freewheel]

I have to say I thought this might have been Dick taking the mickey.

I'm amazed to find it's a genuine nightmare.


My unreserved apologies and my unrestrained disbelief that this hasn't been fixed in the 30+ years the fault has been out there.....


Even old FIATs had a better setup.

[FloaterNorthWest]

I was taught to chock the aircraft and then release the brakes if parking for a long period. On your return, and just before departure, reapply the brakes (the pressure is still in the accumulator) and remove the chock.

FNW

[paulosaints]

RULE's OF THUMB in A109E:

The HYD systems in A109 are:

#1 HYD System
- cyclic, collective and pedals

#2 HYD System
- cyclic, collective

UTILITY HYD SYSTEM
- Normal System: parking break, toe brake, rotor brake, landing gear retraction/extraction and nose wheel center lock.
- Emergency System: landing gear extraction, parking break & nose wheel center lock.


If you want to power the HYD systems of the A109E you have to start the engines in order to have the transmission working. Why?? Because the pumps of the diferent systems are MECHANICALLY driven by the main transmission! So if you the rotor rotating you have HYD power!

If you dont have the transmission working you dont have any HYD power! Watch Out! The chucks/socks are your friend, use it!

In the A109E despite the WIRED Emergency selector is in the Landing Gear pedestal, it powers not only the Landing Gear Extraction, but also the parking break and the nose wheel center lock!

If you press the 2 buttons near the front avionics bay you will deplet the emergency accumulator and will be without any emergency pressure (but only on ground because in flight you cannot press them)!!!

Bye!

I am an A109E (co)pilot! (HEMS in Portugal)!

[paulosaints]

In a A109E that will never happen because if want to have access to the pressure inside those accumulators you have to break the gold wire and put the landing gear in emerg!