Agusta A109E brake system
Thread Starter
Agusta A109E brake system
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.
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.
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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.
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.
Chocks...thats the answer.
HP
Thread Starter
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?
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?
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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.
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.
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How about;
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?
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?
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
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
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
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
Thread Starter
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?
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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.
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.
Last edited by BlenderPilot; 13th Feb 2009 at 04:30.
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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)
Cheers
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)
Cheers
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
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
Last edited by VeeAny; 13th Feb 2009 at 11:07.
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The new electrical hydraulic system option is the old A109 electrical hydraulic pack so you will have hydraulic pressure
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.
Avoid imitations
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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....
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
"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....
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
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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.
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.
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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.
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.