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Could it be safer to *not* replace Rotax hoses after five years and/or overhaul at 2000 hours?


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It will depend on the smallest ICE that can power the generator to keep the batteries charged. I am not sure on how much horsepower size engine would be required. Generators now can be at a lot higher speed so you could get more efficency then hopefuly the weight penalty could be minimal. If you could extend flight range to say 3 or 4 hrs plus reserve that would be ok for our market.

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Beware of statistics. Not doing replacement as being safer is ridiculous. Things used to be test flown. Cost has stopped that. IF a maintenance process can cause a safety concern adjust the process to

While I agree that the chances of powerplant problems increase after maintenance, it is also a comparable point that rubber components have a higher failure rate after a few years.   Rubber

come on 5 years or 2000 hours isnt much to ask.  

Yeah hence the interest in high output constant speed power plants like that rotary etc derivatives.

ICE has to be at least 10% above  cruise power (efficiencies of gen-mot)  plus a bit to put the TO and climb phase  back into the batteries.  So for a 60kW cruise, you need a 70kW ish ICE...90HP ICE. depends if we are talking clutch coupled ICE , or uncoupled

Golly this thread has really gone off track.

Edited by RFguy
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It needs to be managed and that is more complex than it is with just reserve fuel.  I don't know about "off track" as reliability  was the essence of the original discussion.  Forum topics do have a LIFE of their own that you can sometimes just let RUN without much harm done. Nev

Edited by facthunter
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Well I'd certainly like to have 20 minutes  of (barely if necessary) straight and level up my sleeve  in a single, and I would be prepared to have some weight and endurance  penalty  for it. 

 

 

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I actually think we are onto something even with only current technology  here . We can do a feasibility with a few weights and figures. Could be justified on reliability too Maybe? Nev

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Yeah I've done a sums a few times, the difficulty and time is having someone to do the mechanical design and fabrication of various mounts and cradles. 

 

some early decisions are

1) do you do a conventional coupled hybrid
- that is  existing aircraft engine, with a clutch and a electric motor that can drive the prop flange . I say a clutch because I'll assume the ICE failure is a crankshaft lockup.

The electric motor is used for TO supplement and EF provision (20 minutes)  .


2) do you do a constant speed ICE coupled hybrid-

- that is a high RPM constant speed ICE on a reduction gearbox (or CVT or torque converter)  to a prop via a clutch, and as above have the electric motor that can drive the prop flange. as above, electric motor used for TO and EF.

3) an uncoupled hybrid- 

- ICE as a generator-charger-  Batteries driving electric motor direct drive  to prop. Continuous  ICE output is cruise rated only, and the energy difference required  for TO comes out of the batteries for the short TO+climb period.  
 

supplementary electric motor driving clutch coupled can be a direct drive thru shaft pancake motor (thin and wide) or driven on a belt on a ring gear. or hydraulics.. direct drive saves efficiency.

 

While (3) is great, there really is NOT much gained at this stage over (2) or (1).

 

(2) is likely mechanically easier because you likely have more choices on where to put stuff because a small ICE revving at 7k RPM is going to chew up less space than a conventional aircraft engine running at 2500revs. leaving your more weight and space for electrics, clutches, batteries.

 

 

 

 

 

 

 

 

 

 

 

 

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Reprioritise (3). An electric battery powered plane with a genset  to boost the electric motor for t/o and prolong the range in flight If you land refuel the genset to charge battery and top up before T/O. Use external power when these things become more common but you are self sustaining though the genset gets no rest. If it dies inflight you still have a functioning electric aeroplane with a reduced range.  This is the most dead simple arrangement using pretty much currently available components. Nev

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Agreed, from a mechanical point of view, since the ICE is uncoupled, that simplifies placement enormously. Complete freedom for location of the ICE. although you'd probably have it in the firewall forward .

 

Only have to deal with mount for electric motor-prop drive

 

90kW motor (J230 size)  is a good first look.


But the way sizes and controllers go, TWO 45kW motors with controllers is about the same money .  IE two motors on a single shaft. More redundancy. 
 

the two smaller motors compared to one big one- the smaller motors have much less excess metal devoted to cooling, since they don't need to move the same thermal flux (movement of energy) as the larger motor, so everything from the motor and the controller is much easier . IE its easier to get LESS heat out. 

 

J170 size, 80HP >> 60kW  , so two 30kW motors.

 

Just that J230 etc has some space and also the position of the wing lends itself to batteries in the back (meets W&B and still has good payload) . I also considered the Brumby low wing, there are a few kicking around Cowra, easy to retrofit wings with batteries... and they're helpful. 

 

J230 does of course fly just fine on the smaller 80HP   engine, just doesnt fly as fast, and probably struggle a bit in hot wx.

 

Call it 100HP  replacement, so it suits conversions of existing 912ULS machines

so that's two x 37kW motors or a single 75kW motor. 

 

Which leaves...... the ICE !  about needs to be about 75% of 75kW or 56kW ish ....

 

hence- looking at rotary types an derivatives. or turbines.

or small reciprocating piston revving its head off ?????

 

Edited by RFguy
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Thats a nice looking aircraft..interesting is that it is all electric now but they are going to do a hybrid using a 57kw wankel as the source...so they seem to think thats the way to go as well

 

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yeah. the problem is not complex, so not unlikely many people would come up with the same solution.

 

Either that or Turbs will come up with something for us. screaming motorcycle engine ? I'm not against reciprocating engines, they're fine if designed and run well.

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On 11/06/2021 at 9:06 PM, RFguy said:

Jab in recent times reduced their hose replacement to 2 years.

 

Some of the hoses around the oil cooler plumbing are pretty close to the exhaust manifold, and also, they are unrestrained and flop about a bit. fatigue.

 

The fuel hose is also not well restrained as it might be, looks like the fire sleeve does alot of the stiffening job.

 

I wouldnt hesitate to do hoses 5 years or 2000 hours. Alot of far more intensive aircraft maintenance tasks would go past in that time !  

 

Restraining and securing of hoses and wiring etc is not the responsibility of the manufacturer but of the maintainer and the owner. The manufacturer can only nurse you so far. Do the maintenance required and work out any other possible failure points and fix them. Let others know what you have done so that they might avoid any pitfalls.

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On 11/06/2021 at 9:01 PM, Kyle Communications said:

Well if you dont do it you are a candidate to be a statistic for sure. Fuel hose is notorious for breaking down with age and heat as KG says.

In the scheme of things it is cheap to do if you buy all good quality hoses from elsewhere that Rotax. There is plenty of parts that are far better than what Rotax supply. Now you must also replace the fuel pump every 5 years. I didnt think it was that necessary until my mate has had his fail. Luckily he caught it before any drama by always monitoring his engine parameters while flying.

 

 

 

My rubber replacement was done December ‘20, the red fuel hose used has started to split and has turned to concrete……so I am ripping the lot out and have bought Australian made Mackay Rubber hose, obtainable trade in 10 metre roll boxes.

Using all new Tridon clips to secure the new hoses.

 

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On 12/06/2021 at 1:47 PM, RFguy said:

Yeah hence the interest in high output constant speed power plants like that rotary etc derivatives.

ICE has to be at least 10% above  cruise power (efficiencies of gen-mot)  plus a bit to put the TO and climb phase  back into the batteries.  So for a 60kW cruise, you need a 70kW ish ICE...90HP ICE. depends if we are talking clutch coupled ICE , or uncoupled

Golly this thread has really gone off track.

I’m happy for topics to go off track. Also, I’ll stick my neck out and say electric power for airplanes is a long way off. Batteries are too heavy. Synthetic fuel (petrol or diesel), made from renewable electricity, water and carbon dioxide would be better.   

Edited by APenNameAndThatA
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3 hours ago, jackc said:

My rubber replacement was done December ‘20, the red fuel hose used has started to split and has turned to concrete……so I am ripping the lot out and have bought Australian made Mackay Rubber hose, obtainable trade in 10 metre roll boxes.

Using all new Tridon clips to secure the new hoses.

 

Good quality automotive reinforced neoprene hose outperforms and outlasts everything else. 

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Yes that was a bit tongue in cheek. Personally I think electric aircraft they are are better than ICE aircraft in every way except range at present.

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An electric trike !. with a ' ductedFan '.

Now theres a different take on it.

I didn,t get the details, just saw the picture with caption.

AND it looked good.

Just checked utube, & it,s there !.

Richard Charlton from Western Australia , electro aero. Perth.

spacesailor

Edited by spacesailor
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Airbus built a clean design with 2 ducted fans some years back.  I can't see any draggy thing being much use except as a test bed. Nev

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2 readings are worth doing here...  I'd start with Mike Busch.

Some maintenance jobs enhance reliability and some do the opposite.

It takes some knowledge to see what is what here. Reliability centered maintenance is quite a science now but as Mike Bush says, this has gone unnoticed by GA.

In ww2, a prof called Waddington vastly improved  the reliability of a squadron of u-boat killing Liberators by doing LESS maintenance.

Yes, it is intuitive to think " maintenance is good therefore the more we do the better" but this is just not so. 

On rubber hoses : I reckon these are highly inspectable things and you squash them too see if there are tiny cracks showing in the tension surfaces, also you feel their elasticity.

How often do you replace them in your car? But if you were Mr Rotax, of course you would assume the worst possible case for rubber deterioration.

There was a Jabiru landed on the Sruart Highway because of a tiny fault caused by replacement of the fuel hose.  I could cite other examples, but the message is that maintenance is quite a dangerous thing to do.

And as for airliners, their increased reliability is partly due to their smaller maintenance lists.

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There's something very wrong IF something is less reliable after it's repaired, checked or adjusted.. Sloppy maintenance can  result in unreliability or if it's done in a poor maintenance environment. (using improvised methods) and tooling). Fiddling with an engine just to make you feel good is not maintenance.

   Saying maintenance is quite a dangerous thing to do is BS.  and bloody irresponsible. The engine's designer/ builder should know the most about a product. The opposite of maintenance is NEGLECT. examples tyre tread depth tyre pressure  Brake lining limits wheel bearing adjustment control system play exhaust system cracks and springs engine mounts tappet clearances fuel and oil filters. I could write a book here.  Nev

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Nev, read the second sentence again...   " some maintenance jobs enhance reliability and some do the opposite".

I reckon you have fallen into the trap of thinking that maintenance is so good that you can't have too much of it.

Reliability-centered maintenance is the subject of books these days and the message is NOT one of neglect at all.  There are some actions, like changing the oil, which enhance reliability. The other things you mentioned like tread depth and tyre pressures are also  in this category. There are other actions, like replacing perfectly good hoses, which detract from reliability.

I was a mate of this guy who flew helicopters  in the airforce. He hated the first flight after maintenance as there would be something wrong for sure.

From your response, I don't think you know the Waddington story. He faced a lot of the stuff you have come up with but, amazingly to me, he got his way and doubled the reliability

of those Liberators. I reckon he must have had powerful backing, possibly up to Churchill, to do this. He was not a pilot or an engineer himself, but he was a good scientist who believed in evidence.

Of course, the Waddington stuff was top secret and unknown for many years.

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Just read carefully what I say thanks and don't put words into my mouth. Of course the first  flight after a plane has been on the ground a long while is often quite dangerous because the system checks are not adequate. Sub assemblies should be bench tested not tested on the plane. IF corners are cut there will be plenty of unreliability.. and there often is due to being pressured into getting the plane back in the air and pirating bits off other planes or a quick fix..  with a swapped bit that looks ok.

  Many of these "revelations "  may make good reading but a few I've read are pretty questionable. and I've had inflight failures I didn't cause and done test flying where things failed. IF better maintenance had been done they would not have failed, but it's It's a quantum leap of misplaced logic to take that as do less maintenance and you have less failures. You fix your maintenance set ups faults, like documentation and shift change over procedures and account for every tool used and part installed and removed.. Nev

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Maintenance! .

The 4X4 clubs tell everyone to carry spare parts AND to replace parts before going on long offroad trips.

My thought is, if replacing perfectly good parts, why not csrry them as spares, after all they were good Before having to remove them. 

spacesailor

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