Prop stopped.

[spacesailor]

BUT without R E G, one particular hill is third gear.

Then blank removed , flat to floor in second gear !.

So, quite a big power loss. For any towing vehicle.

Then L P G injection gives a big boost to the same motor !,

IF you Never ever, run out of diesel,  the straight L P G will blow the engine.

spacesailor

[Garfly]

 

 

 

 

 

 

[Garfly]

On 14/05/2022 at 3:06 PM, Thruster88 said:

  His other vid showing the internally cut fuel line is interesting. This type of thing can happen with limited mechanical experience and ageing eyesight.  

I think this is the one you mean Thruster.  Yeah, an interesting suite of engine problems, trouble-shootings and seeming solutions:

 

 

[Mike Gearon]

I had my first prop stop a week or so ago. Caused by a combination of factors. Took off from a towered airport with Phoenix airspace nearby. First problem. After take off I couldn’t hear controller. Something had happened to volume. Wasn’t my Bose A20>…. As I was cleared for an easterly departure I turned east. No nav screens in aircraft so I was relying on iPad. No aircraft displayed on the iPad. Had no idea what airspace I was in. Finally figured that ForeFlight open in both iPad and iPhone gives priority to one only. Avplan in Australia I’d not experienced this. Turned off the iphone. Found my aircraft in what a glance said was Phoenix airspace. I took a screen shot as you see so I’d have evidence of exactly what happened. I worried all the way to Moriarty about the “phone call” until later realising I wasn’t in their space…screenshots… good!
 

These two things, missing tower call and navigation problem rattled me. Recovered and full tanks of fuel for a 3 hour flight with tail wind to New Mexico and ground speed of some 125kn. . Left tank only with rotax line return to left tank and my side of aircraft so get the weight sorted. Turned tanks at 30 minute intervals as recommended.

 

Next problem… late departure due to getting wings on aircraft (inexperience) meant a really rough ride and speed drops down as low as 70kn and dust devils to avoid and light rain following behind and I missed tank change. Ended up pumping fuel out of the left tank. 
 

Prop stopped over some pretty nasty ground west of Albuquerque. I must have spent a full 5 seconds pushing the throttle backward and forward looking for rpm change. Too long in my opinion now… anyway, turned off right tank and on left tank. About 20 seconds later I had power. To leave right on would just suck air. Pipistrel,forum mentioned this and I knew it. Then, to make sure the problem wasn’t elsewhere and I’d need an emergency landing I repeated. Prop,stopped and 20 seconds later I’m confirmed with problem and a full left tank to proceed. 
 

I’d had a buyer reject the aircraft and was ferrying to Robert Mudd in New Mexico as one of the recognised experts to give the aircraft a thorough going over. 7 year old rotax 912 with some 200 hours and due for rubber was on my mind!

 

Should I have turned the fuel tank off and repeat? Well, the fuel levels through fibreglass windows are notoriously difficult to read. I’d been flying rolled to one side then the other to try to see fuel move. I was fairly certain left was full and right empty but wanted it confirmed or I’d divert and land. 
 

I was relaxed enough to get a nice picture of camelback on the way out. 🙂 

 

[facthunter]

It's usually a combination of factors that get you. Nev

[Mike Gearon]

Just a short note on sucking air. I’d read some 12 months ago about the problem and a Pipistrel did go down some years back and was found to have both tanks open and fuel remaining in 1 tank. The Australian importer had noted on the Pipistrel forum that in their tests they’d empty a tank and prop stop, turn empty tank off and crank start. I relied on windmill start. Twice. I also note the importer discussed how bad air in the lines is. Had about 5,000ft and 27:1 glide so not a large problem.  To repeat the experience  I’d not have tested it again and put air in the lines a second time. 
 

Take home is to reinforce emergency procedures. I redo first aid each year and while it’s always annoying and I think unnecessary there are holes that have developed over the 12 months. 
 

It’s well worth installing a reserve tank with rotax return to the reserve. Double or triple fix. 1. No need to switch tanks. 2/ Reserve of some 16-18 litres is another hour Rotax flying time as a bonus, 3. alarm or tube site the reserve and plenty of time to find an airport.

 

 

[IBob]

Mike, the Savannah has a 6litre receiver tank behind the passenger seat, with a low level switch in the top of it and an indicator on the panel: gives about 20minutes of warning, remedies all sorts of things like momentary unporting, allows flying of outboard tanks to exhaustion without loss of power etc.

I'm sure many other aircraft have something similar, it's a terrific feature which avoids all manner of problems.

[Garfly]

This guy took his sister for a fly ... she seemed to be enjoying the whole thing immensely, until ...

 

 

 

 

[facthunter]

At least he posted it.. I suppose you don't know your reaction till something happens. No damage as it worked out. I've flown one of those. They're nice. The landing looked fast,   but he was straight into wind by the sock. IF you know you are getting things wrong, slow down, but we are all different.. Your training shouldn't limit you. It should save you. I think the issue here is whether to keep trying for a field that relies on a failing engine to get you there   Nev

[Garfly]

20 hours ago, facthunter said:

Your training shouldn't limit you. It should save you. 

I'm not sure what you're reacting to, Nev, but I reckon the saying he puts up at the end and what you're saying amounts to the same thing, no?

 

"Under pressure, you don't rise to the occasion, you sink to the level of your training."

[facthunter]

A response I've heard many times Is "I don't know why I did that. I was trained to do something else." Good training and recent practice/experience will come through and keep you busy. When you are busy you don't have time to panic, but it's an unknown till you  experience it for yourself.  Some people freeze on the controls. Nev

[Mike Gearon]

On 5/6/2022 at 3:21 PM, IBob said:

Mike, the Savannah has a 6litre receiver tank behind the passenger seat, with a low level switch in the top of it and an indicator on the panel: gives about 20minutes of warning, remedies all sorts of things like momentary unporting, allows flying of outboard tanks to exhaustion without loss of power etc.

I'm sure many other aircraft have something similar, it's a terrific feature which avoids all manner of problems.

It should be a regulation. 6 litres is a nice amount to run a tank dry and get a warning light with of course preference to keeping an eye on the low tank and then keeping an eye on the receiver level.
 

Biggest benefit is the rotax return has to go back to the ON tank.

 

Almost as big a benefit is being able to completely empty a tank. If you’re half way to destination and a tanks empty then plans need to change. If you’re over half way and empty a tank and check your calculated distance and you’re short then work out what’s wrong and plans may need to change. 
 

Usable fuel on 2 low tanks that can unport is something you don’t want to be flying. I have a plan to put in a 150x150x600 stainless reserve. Approx 12 litres with sight gauge and  warning light in dash. Feed the 2 tank lines in and reserve return in with a bottom line out. Takes up a bit of room in storage area with the BRS and arguably more useful.

 

 

[Bosi72]

30mins fuel reserve is required by the law.

The aircraft's POH should say switch tanks every 30mins. I.e. use right tank when a minute hand is between 0 and 29, use left tank when minute hand is between 30 and 59.

 

Edited June 13, 2022 by Bosi72

[Mike Gearon]

Regarding fuel tanks/ reserves/ returns…

 

I’ve just received an education re return from Rotax. seems you can’t do the obvious and connect the return to header tank. I guess a few here already understood that from some helpful messages I received.

 

. Even returning to a wing tank has its potential problems.
 

https://www.rotax-owner.com/en/912-914-technical-questions/6329-mandatory-fuel-return-line?start=5

[RFguy]

Jabiru has header tank 🙂 and header tank warning bells.

On my 912 conversion, I will need to think about the fuel return. A few have done it as a dribble back to the header tank  and T'd the hose from the wing and a check valve..

Requires some thinking about.

Really I then will want a 2nd fuel flow sensor on the return so I can subtract it off. 

 

That rotax discussion was an interesting one, Mike. good reading. 

[Mike Gearon]

10 hours ago, RFguy said:

A few have done it as a dribble back to the header tank  and T'd the hose from the wing and a check valve.

Rotax comverison….? I’ll have to go back through threads and catch up. I recall you spent a lot of time on airflows with the jab. I’d go UL if you’ve not got to the buy stage yet. Those engines are so simple. More like a lyc/ cont engine. I’m very happy with our kit plane decision to go UL520 turbo 220hp.

 

Re PROP STOPpED as relates to the tanks/ headers/ return lines.

 

I didn’t realise a few things until both that read and a few helpful private discussions. The more I learn the less I know!

I had a discussion with a very knowledgeable guy here who mentioned vapour lock. Also mentioned how that return orifice could be easily blocked. I guess you could drive yourself crazy looking at all the “what if’s” but… now knowing this I’m thinking the rotax return line should have a flow meter. 

 

1. The fuel pump is creating bubbles… methane bubbles and vapour. These aren’t a big deal in the carburettor bowl because it’s like a tiny vented header tank. Not so great for fuel injection. Not so great to return to a header tank that isn’t vented. These bubbles also go back into solution under pressure.

 

2. I now understand the return has an orifice! Below lifted from rotax discusion on why the return line has an orifice/ restrictor. 
 

THE REASON

 

The fuel return line's purpose is to prevent vapour lock, by simply keeping a small amount of fuel always moving thru the system. The restrictor's job is to prevent the fuel pressure in the system from getting too low, while still allowing a small amount of fuel to pass thru the system, and be returned back to the fuel tank. Without the restrictor, fuel would flow at max rate, which might be too much for the fuel pump to handle. This would be similar to turning on your garden hose. Unrestricted, water gushes out of the hose, and the water pressure inside the hose is not very high. Now, place your thumb over the hose. Water still flows, but you have reduced the amount of water that flows, and you've raised the pressure inside the hose.

 

THE AMOUNT of fuel flowing in bypass (yes, you really can empty a wing tank out the rotax return line wing tank vent….I’ve done it! At 5gph (US gallons) that’s pretty easily done.

 

related to restrictor orifice.

 

 

 

0.3mm (0.012") to 0.7mm (0.028) have been used sucessfully.

The larger sizes would be more appropriate for the lower fuel pressures seen in the UL engines.

The smaller sizes would be more appropriate for the iS engines with 45 psi fuel rails.

 

Once you get it installed, Test it!

An unrestricted fuel system can pump ~30 gal per Hour.

You want to bypass ~5 gal per hour. Not too much more.

5 gph is one quart every 3 minutes.

Run the bypass hose to a quart jar.

It should be about half-full in 90 seconds.

[RFguy]

Hi Mike

I was very interested to read the advice that the bubbles were likely hydrocarbon gas bubbles and would be forced back into solution with a little pressure. (how much?)

 

as for the restriction.  I would be sure there are volume flow fluid restrictions that existing in fluid control world. Such a device might work in pulses, and if so would likely confuse most fuel flow meters unless some sort of accumulator (fuel filter might do the job), was used. 

 

To get the fuel back in the header tank without modifying the header tank would likely need a T on the wing line, and a check valve on both wing line and return line. Arrgh check valve in wing line. no thanks. extra stuff. Perhaps control the pressure of the return line so it cant pump into the wing tank. This needs to be thought about very carefully

 

Rather than vapour lock due to elev temps, could use Peltier effect cooling cold plate to pass the fuel through....at low flow of say 9 lph (only 2.5mL per second, which to reduce the temperature say 30 deg C (but must be closed loop as not to  make carb freezing easier)  1.9 grams/second at specific heat of 2.2kJkgK, requires cooling input of 125Js. Too much that aint gonna fly, too much power required. You'd be better to pass the fuel through a very small oil cooler radiator that was in the airflow.

 

So the return is the easy way. interesting the discussion of bubbles and the gascolator....

 

BTW- I got a 1900 hour 912ULS with full books at a great price. Going with EPROP, likely 4 blade to get size equiv. That that discussion is not for this forum topic- I will refresh my ULPOWER awareness.

 

-glen

[Mike Gearon]

I’m heading back to just dumping it in the one wing tank. Simple is best. 
 

UL is the engine Jabiru should have been! Rotax are pretty well sorted 

[facthunter]

Bubbles in a carburetter bowl make the liquid less dense and the float sinks and the carb floods so it's a Problem that would not be apparent at a later inspection time. Trying to cool it by bleeding fuel is a fairly silly idea that creates more problems.. Nev

[RFguy]

and a sinking float is no good.

Nev, when you say 'bleeding fuel' what are you referring to? the technique of returning fuel to the tank ?

 

 

[facthunter]

Yes. It increases flow but not by much and brings other problems with it Like venting and not knowing exactly where your fuel is and mucking up your fuel flow indications. Nev

[RFguy]

so best way is to avoid it to start with - well insulated fuel  lines. if mechanical from engine fuel pump, pump to be heat shielded and thermally isolated from engine block, etc etc

 

EFI runs high pressure, so I  *presume* not subject to vapour lock most cases. 

[facthunter]

Cold air "blast tubes" are the common way of dealing with such issues and Lagging of engine area fuel lines. Nev

[IBob]

All this theorising is all very well, but thousands of aircraft have a fuel return, via a small orifice, as per the Rotax installation spec. and it apparently works very well.
Yes, it's a pity if it mucks up your fuel flow readings.
No it's not difficult to arrange to vent it back to tank.

 

And in a vapour lock situation (which you potentially have with a heat soaked engine bay after a recent stop) what you are expelling via the orifice is not liquid, it is gas......and so passes far more freely.
How do I know? Shut down on mates strip, nobody home, set up for restart after 5mins, activate fuel pump and it chatters away for 10 to 15 secs before settling down to it's usual rate and fuel pressure is established.
PS: in that scenario we also don't take off immediately. We allow a few minutes of engine running to lower the temperature in the engine bay.

 

Or you could thermally insulate everything, and hope for the best???

 

Edited June 15, 2022 by IBob

[facthunter]

It's NOT theorising Bob It's been done. Having carbs on top of the motor is not ideal. particularly float type ones. Fuel isn't much of a cooling medium except when it vapourises and you sure don't want that in the carb.bowl.  This problem was also common with some road cars. Fixed now because Carburetters are a thing of the Past.. Nev