Fiti In-flight Adjustable

[Guest Bristell]

I have had a 2 stage  Fiti inflight adjustable prop on my Bristell since 2013. The two settings are takeoff and cruise which are controlled by a simple 3 position switch. When it is working correctly it’s an excellent combination which will give a TAS around 129 kts on a good day. The problem has been with the little electric motor which adjusts the blades. They tend to burn out regularly and if I get 150 hours out of them I have done well. At almost $700 a pop they aint cheap. The Fiti factory have not been too helpful with comments such as “it must be poor alignment “ and” I must be trying to run it too coarse”  etc. If they get $700 for each new one I guess they will not be in a hurry to do a redesign and fix the problem. I did send the whole prop back to the factory early on  and apart from supplying a new motor they could find no fault. I am definitely not cruising too coarse because in accordance with Rotax’s advice wide open throttle at sea level is greater than 5500 rpm. Any suggestions? 

 

 

[Downunder]

Could be a lubrication issue. Inadequate lubrication or wrong type? (Not sure exactly what requires lubrication on your system. Linkages, threads and/or bearings)

 

Sounds like the motor is struggling to overcome the forces required to change pitch.

 

You could probably test current draw of the motor to see if it is within spec.

 

 

[Guest Bristell]

At the manufacturer’s direction I have lubricated the shaft with high temperature grease. There is quite a stiff spring which holds the prop in fine for takeoff which has to be overcome by the motor when it moves to coarse. I’m not sure how much force is required when you add airflow to the equation though.

 

 

[facthunter]

 IN Propeller school they teach you that aerodynamic forces tend to take the prop to Coarse and centripetal forces take it to fine. I would think that for this type of prop the flinging forces would easily overpower the aerodynamic ones. Any HUB  bearings are subject to high loads due to the RPM's. This would stiffen the action if it did anything. IF you cut the power (electrical) what happen? IF it runs to fine then the motor is holding it in coarse and that would not be a satisfactory arrangement.. The motor should incorporate a brake ideally. Curtis props are mostly electric motor operated. Yours probably has slip rings. as most do. Nev

 

 

[Downunder]

In the Flight Design CTSW I've looked at, the motor drives a screw so I guess there is no load on the electric motor unless changing pitch.

 

I would really hope it's not the motor holding the pitch on yours.....

 

 

[facthunter]

A fine worm and worm wheel will not drive in the reverse direction  generally but if it's "inching" and the motor is cutting in all the time the motor won't last long. When it fails are the windings cooked? Gone dark and smell acrid/ burned. Nev

 

 

[Guest Bristell]

The motor only runs when I move the switch. When I test it on the ground by moving it to coarse it runs quite freely at first but seems to labour over the last few mm. There are limit switches at either end of the drive. When the motors fail there is the acrid smell like its cooked. The top of the engine where the motor is bolted on also gets very hot so I wonder if that’s part of the problem. On the advice of the Bristell dealer I’m looking at changing over to a Duc constant speed . Apparently Bristell have been fitting these to new aircraft for several years with almost no issues so far and they also have decent leading edge protection which the Fitis lack.  About twice the price of my Fiti though! 

 

 

[facthunter]

 Maybe a limit switch is not set correctly. No part of your aero engine case gets hot enough to make the electric motor smell burnt. Nev

 

 

[skippydiesel]

With any l2 Volt electrical problem, I strongly advise, as a first investigation, checking for excellent continuity/earth return - all too many 12 Volt system fail due to poor earth return.

 

Second - check all contacts/joins for excellent security. All joins must be firm, not easily  move in any direction- a good tug will give you some indication.

 

Third - check that the controller is delivering the required power through all settings.

 

Fiti make a terrific ground adjustable prop - no experience with the in flight adjustables but would have expected similar service - it will be a pity if you have to go to another prop (let me know if the Fiti is available I would like to see if I can get it going reliably)

 

 

[onetrack]

I'd be checking that the wiring to the motor is of adequate enough size to carry the maximum current that the motor can draw, when it's labouring under heavy load.

 

Remember there's substantial current-carrying ability lost if the cable is long between battery and motor, too - so you have to take into account, the length of cable.

 

Skippy is on the mark with earth return and good connections. "Bright and Tight", is the old saying.

 

 

[Downunder]

You really need to check current draw through the range of movement.

 

Nev maybe correct that the limit is set wrong. I would expect a constant current draw throughout the movement range while engine is not running. If it runs out of "stroke" that will definately make motors fail.

 

Skippy makes a very good point about cable connections and size.

 

My aircraft mfg undersized my battery cable significantly for example. Now corrected to Rotax specs. 

 

Is the motor labeled or have specs? Manufacturer or model number?

 

 

[Guest Bristell]

The motor appears to be an Igarashi Type 33 G . With some difficulty I have managed to source one from Austria for about $30 plus freight of course. I plan to install it in the Fiti cradle on the gearbox and go from there. I have about four spare cradles now and $30 is a lot more manageable than $700. I will look further into what Skippy and Onetrack have said re current draw and wiring . If I decide to go with a different prop I will advise people on here. 

 

 

[Downunder]

I'm not sure if this is the one, 33 G as there seems to be a couple of reduction gear ratios.

 

50:1 and 312:1....... and some others it seems.

 

This is the pdf for the 50:1 unit....

 

 https://produktinfo.conrad.com/datenblaetter/225000-249999/244023-da-01-en-GETRIEBEMOTOR_1_50_TYP_33G.PDF?direct=

 

 

[skippydiesel]

It was Onetrack who mentioned cable size/amp rating. 

 

I have often observed how we human will jump to the most complex/costly solution to any problem - that's why I and others, have recommended starting with the simple low cost possibilities. Work through these more often than not this is where your solution/problem lies and if not, little has been lost, go spend the big bucks.

 

 

[Downunder]

It was Onetrack who mentioned cable size/amp rating.

 

My mistake.....won't happen again.....?

 

 

[Guest Bristell]

Thanks! I have ordered that motor from Conrad. Quite right to suggest working through the problem slowly but I’ve had this ongoing for over 6 years always hoping the next little modification we try will provide the answer. Even tried $5 Chinese motors at one stage . I usually carry a spare motor and tools when I go away on a big trip because they always seem to fail in Winton or Sweers Island or somewhere there is no help available.

 

 

[facthunter]

IF your cruising speed is below 120 knots you probably don't need it. Where does it fail ? Fine or coarse or anywhere? Nev

 

 

[skippydiesel]

Any chance you might post some photos (cowling of)  of the installation ?  - might help with the flow of suggestions.

 

 

[Blueadventures]

Have you opened up a motor, what do the windings look like, has it got brushes or brushless.  Would service to comutator section work?

 

 

[skippydiesel]

Bristell - Any progress???

 

 

[Guest Bristell]

Just waiting for new Igarashi motor to arrive from Austria. Will mate with one of my good gearboxes and see how it goes . Also have sent a complaint to the owner of the Bristell factory who has been promising a fix for this issue for years. Thanks Skippy

 

 

[skippydiesel]

Let us know what changes/adjustments you made and if they have any beneficial outcome - Good Luck!!!

 

 

[Guest Bristell]

Will do

 

 

[BirdDog]

I know this thread is old. But wondering what the outcome was?

[skippydiesel]

26 minutes ago, BirdDog said:

I know this thread is old. But wondering what the outcome was?

Me too!