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25 May 2022, 11:49 [ UTC - 5; DST ]


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 17:31 
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Username Protected wrote:
The -8 and -10N used in the 441 have two points of temperature compensation, the compensating resistor on the engine case that the EGT probes are connected to, and the fuel computer SRL system that uses multiple inputs (temp, airspeed, etc.) to condition the EGT so the pilot can always use 450C as the red line. This secondary system can be turned off by flipping off the fuel computer, in which case a chart is needed to compute redline. The resistor on the engine case can be adjusted within a range set at overhaul (or manufacture) and listed on the DSC sheet. The EGT value is then basically an arbitrary value based on these two adjustments.

The -14/15 are unique scaled up versions with a larger case and components, so not sure what might apply there.

I was unaware there was any way for the pilot to turn off any engine controls from the cockpit and I don’t recall any ‘off’ switch on the fuel control itself, but it’s been 25 years since I last worked on TPEs.

BTW, while the -14GR/HR and -15AW models are larger physically (aka large blocks), the basic architecture is similar to the small block 331s.


Fuel computer can be turned off, not the fuel controller on the engine. The computer controls the FCU via a servo based on power lever position and other inputs. The condition levers can cut fuel manually though of course.

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 17:33 
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Username Protected wrote:
Very interesting Art.

Would you be able to answer why the -14 has an electronic FCU, whereas the small block 331's have either Bendix or Woodward "bellows and monkey motion" FCU's? Was there ever talk about "downscaling" the -14 FCU to the small block series?

Reason I'm asking is that a friend over at the Commander forum was kinda taken to the cleaners overhauling his Bendix unit just recently. Bad service, very expensive and there is only one overhaul shop. Seems like an electronic FCU (basically an advanced fuel injection pump, right?) would be so much more reliable and easy.


The -8 on the 441 has an analog electronic FCU. I am not familiar enough with the -14 system to compare them.


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 17:46 
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Joined: 08/05/16
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Username Protected wrote:
Very interesting Art.

Would you be able to answer why the -14 has an electronic FCU, whereas the small block 331's have either Bendix or Woodward "bellows and monkey motion" FCU's? Was there ever talk about "downscaling" the -14 FCU to the small block series?

Reason I'm asking is that a friend over at the Commander forum was kinda taken to the cleaners overhauling his Bendix unit just recently. Bad service, very expensive and there is only one overhaul shop. Seems like an electronic FCU (basically an advanced fuel injection pump, right?) would be so much more reliable and easy.


The -8 on the 441 has an analog electronic FCU. I am not familiar enough with the -14 system to compare them.


In case terms are being confused (maybe it's me that is confused), the unit on the engine, which can work without a computer, is mechanical. This unit on the -8/-10 on the 441 can (additionally) be controlled via an electronic computer located under the cabin floor, that reads the power lever position along with a few other inputs to send a signal to a motor that moves the mechanical fuel control unit.

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 18:06 
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Username Protected wrote:
Very interesting Art.

Would you be able to answer why the -14 has an electronic FCU, whereas the small block 331's have either Bendix or Woodward "bellows and monkey motion" FCU's? Was there ever talk about "downscaling" the -14 FCU to the small block series?

Reason I'm asking is that a friend over at the Commander forum was kinda taken to the cleaners overhauling his Bendix unit just recently. Bad service, very expensive and there is only one overhaul shop. Seems like an electronic FCU (basically an advanced fuel injection pump, right?) would be so much more reliable and easy.

You are absolutely correct. Basically, it comes down to cost.

This question came up repeatedly during my career. It was always a variation of "why can't our cutting edge 'X' technology be retrofitted into our legacy products?" The answer was one or both of the following:

    * The newer technology would not be incorporated if the basic configuration was reconsidered or caused too much 'collateral' damage. Some examples: a new turbine blade ceramic coating might reduce the amount of cooling air required, but also require the blade's internal passages to be redesigned (with new castings required) to achieve this benefit; adding a new design might require redesign of all the surrounding hardware - sort of pulling a thread and having everything unravel

    * The cost of certifying the new technology would never be recouped. If there isn't a big enough market demand to justify the NRE (non-recurring engineering) costs, it'll doom any retrofit. Remember, also that in addition to the engineering and certification costs, the hardware price to the customer must also absorb the manufacturing material, labor, and tooling expenditures, plus overhead, utilities, taxes, etc and PROFIT!

On occasion improvements did occur, but it was usually because of some external factor, such as a supplier refusing to make the part anymore (too costly or not enough business to justify) or the processes used to make the part became illegal (lots of chemicals used in the manufacture of aerospace hardware have slowly been banned in states like California and throughout New England, with the suppliers deciding to give up the business rather than relocating their facilities). Fun fact: In one of my jobs, it was a real struggle to stay ahead of prohibited chemicals. The European Union was banning chemical compounds at the rate of about 30 a week/1500 annually. As soon as we would check thousands of active drawings and specs to ensure compliance for European regulators, a new list would be published and we'd be going over everything again.

As to the specifics regarding engine controls, like FCUs, we were always bitching about the mechanical/hydraulic systems. They were typically large, heavy, complicated, prone to failure and in general a PITA. However, once certified, things tended to stay untouched (unless there was a safety of flight issue - then things got updated pronto!). Newer models of an existing product would get upgrades, but rarely did it make sense to retrofit.

The -14/-15, being part of the big block family, was a blank slate. Engineering had to design new everything from the centerline out, new tooling was required, and the opportunity to put the latest and greatest controls was rolled up into the NRE and certification costs. Sadly, I'm not sure the big blocks ever sold enough units to put the program in the black.

Here is a rule of thumb that held for my 40 year career. A new turbofan/turboprop engine design or model upgrade, (such as a TPE331-8 to a -10) required a minimum of 600 units sold to break even.

Art


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 18:12 
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Username Protected wrote:
In case terms are being confused (maybe it's me that is confused), the unit on the engine, which can work without a computer, is mechanical. This unit on the -8/-10 on the 441 can (additionally) be controlled via an electronic computer located under the cabin floor, that reads the power lever position along with a few other inputs to send a signal to a motor that moves the mechanical fuel control unit.


Most of the TPE models I worked on controlled the FCU via a cam mounted on the engine throttle. The cam position determined the amount of movement the throttle cable would allow the FCU arm to have. Garrett used to produce 'custom' cams for customers who wanted different throttle responses depending on the throttle lever angle. I did a number of jobs along these lines - a lot of fun laying them out using CAD


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 12 Jan 2022, 22:19 
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Username Protected wrote:
In case terms are being confused (maybe it's me that is confused), the unit on the engine, which can work without a computer, is mechanical. This unit on the -8/-10 on the 441 can (additionally) be controlled via an electronic computer located under the cabin floor, that reads the power lever position along with a few other inputs to send a signal to a motor that moves the mechanical fuel control unit.


Most of the TPE models I worked on controlled the FCU via a cam mounted on the engine throttle. The cam position determined the amount of movement the throttle cable would allow the FCU arm to have. Garrett used to produce 'custom' cams for customers who wanted different throttle responses depending on the throttle lever angle. I did a number of jobs along these lines - a lot of fun laying them out using CAD


That’s interesting. In normal operation on the 441 the computer controls a motor which controls the FCU, via a potentiometer attached to the power lever. Honeywell now charges $7,000 for these power lever pots, which I’m guessing cost $10 to make and could be found used for cents if it was in a car.

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 21 Jan 2022, 10:55 
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I am headed to a 3,000 foot runway Sunday.
Have not flown much in last month due to maintenance then covid so went up a few days ago.
Flew a couple of approaches then landed at my home drone 7,000ft then went to PYG-3400 feet.

Right gusty crosswind with about 10 knots of headwind component.
Stopped on runway about 2200 feet with healthy reverse and brief moderate braking.
9700 pounds.

Wheels up on take off was just a bit under 2200 feet. Warm brakes will hold at take off power.

Obviously I have to throw accelerate stop out the window when using a shorter runway.
For a couple times a year and light this slight increased risk is acceptable to me.

When I purchased this Avanti I never expected to land under 4,000 feet.

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 21 Jan 2022, 11:03 
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That's awesome Brad. I need to do some work on this. I"m conditioned by having rarely touched the brakes in the MU-2 and seeing $$$ every time I touch Avanti brakes. I don't think I've use a less than 5000' runway yet.

I did fly into a slightly contaminated (snow/deice/etc) runway a few weeks back. Was very cautious. It was fine on the runway because it was in pretty decent shape. However, I did learn that on an icy ramp the Avanti will rotate up a vertical axis - needing only it's wingspan to rotate 360 degrees!


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 21 Jan 2022, 11:26 
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I did fly into a slightly contaminated (snow/deice/etc) runway a few weeks back. Was very cautious. It was fine on the runway because it was in pretty decent shape. However, I did learn that on an icy ramp the Avanti will rotate up a vertical axis - needing only it's wingspan to rotate 360 degrees!


:bugeye:

My carbon brakes were overhauled 2/20. I do not use brakes normally other than having to warm them up a bit to hold for auto feather test each take off.

Moderate braking 4-5 times a year....hoping these brakes outlast me.

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 21 Jan 2022, 17:29 
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Took the commuter car 2600miles this week.

Tailwinds helped make short work of trip there. Was over 550kts groundspeed for a good chunk of the flight.

Coming home today I ducked out of the headwinds and stayed at FL300. Temps were cool and I almost made 400 tas :)

Had more temp and torque so could have cracked 400 if I had the STC for Mach .7 ops.

Approach to mins in light snow at the home drome. Good week of flying!


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 22 Jan 2022, 20:29 
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Username Protected wrote:
Took the commuter car 2600miles this week.

Tailwinds helped make short work of trip there. Was over 550kts groundspeed for a good chunk of the flight.

Coming home today I ducked out of the headwinds and stayed at FL300. Temps were cool and I almost made 400 tas :)

Had more temp and torque so could have cracked 400 if I had the STC for Mach .7 ops.

Approach to mins in light snow at the home drome. Good week of flying!


That's AWEsome! But without a side by side of the East bound leg at 550, this picture is incomplete... :shrug:


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 27 Jan 2022, 09:56 
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What's everyone's experience with foreign object damage to the props?
Of course, the prop guys say it happens "all the time with Piaggio". Another 3 weeks grounded.

I'm getting frustrated with all the downtime :pullhair:


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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 27 Jan 2022, 09:58 
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Username Protected wrote:
What's everyone's experience with foreign object damage to the props?
Of course, the prop guys say it happens "all the time with Piaggio". Another 3 weeks grounded.

I'm getting frustrated with all the downtime :pullhair:


Did it take a chip out of leading edge?

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 27 Jan 2022, 10:15 
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Username Protected wrote:
What's everyone's experience with foreign object damage to the props?
Of course, the prop guys say it happens "all the time with Piaggio". Another 3 weeks grounded.

I'm getting frustrated with all the downtime :pullhair:

How many times has this happened? What is the nature of the damage? Any idea how or where it happens?

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 Post subject: Re: The definitive Piaggio P180 Avanti thread.
PostPosted: 27 Jan 2022, 14:53 
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Yikes. Have not heard of that being a ‘problem’.

When I did my pre buy I had a nick in a blade that was repaired.


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