Prop stopped.

[Garfly]

16 minutes ago, IBob said:

And that's really cleaned up and fast for a Jodel. Very small air intakes......

 

Yes, and if you read his blog around 2018/19 you can see that the clean lines are no accident (a random sample):

 

 

"January 1st. 2019
Cover, oil cooling air outlet.

First of all, happy new year to all and full of success in what you are about to undertake.

For my part, I hope to beat a new speed record this year and fly at more than 130 kt.

 

 

 

 

I don't like to redo what I've already done, but yet it was necessary to redo the oil cooling outlet air duct for the new hood.
However, I made a few minor changes. First a curvature a little more studied than the original basic bend (first photo) with a slightly larger bend radius and a slight converging in the bend to locally accelerate the flow and avoid separations in the bend. Finally, the outlet on the cowl side will be flatter for better integration of the outlet flow into the general external flow.  The part was therefore laminated with epoxy on a polystyrene male mold covered with tape, as usual.
The exit is also more oriented upwards by an additional 5°, ie well parallel to the external air streams which at this point rise to bypass the leading edge of the wing towards the upper surface (observation by film of oil).
Finally, the output section is slightly decreased (-15%), which will decrease the flow a little, but will increase the output speed. Indeed, the cooling of the radiator has never been insufficient, even in hot weather, so I think I have a little margin to try to optimize this cooling trail."

 

Full blog:

 

https://speedjojo-blogspot-com.translate.goog/search?updated-max=2019-02-01T18:21:00%2B01:00&max-results=2&start=27&by-date=false&_x_tr_sl=fr&_x_tr_tl=en&_x_tr_hl=en&_x_tr_sch=http

[Mike Gearon]

14 hours ago, IBob said:

 

Regarding my Plane Crash YouTube links above, the pilot has not thought it through. The reason his fuel has gassed in the pipes is the elevated temperature in the engine compartment. Ideally, his fuel system should have a return that moves that gas, and the heat it contains, out of the engine compartment (as per Rotax recommendations), replacing it with cooler fuel. But what he has put in is a short loop that simply recirculates gas and heat under the hood, because somebody has told him this will fix the problem. That's what's called magical thinking.

 

Finally, since I wrote 'detail': note the fine fuel filter before pump and return etc in the Rotax recommended fuel system. This prevents not only carburettor jet blockage, it also prevents blockage of the orifice in the fuel return, and ensures the pressure relief bypass in the electric pump seats properly.

Yes, I’ve paid attention here. The tiny orifice of the return line necessary to maintain pressure and obviously to limit fuel return flow. Say 30 minutes and 10 litres to a wing tank as acceptable and 20 litres as way too much. Balancing act between keeping the fuel cool/ vapour exit and not returning an unmanageable amount of fuel.

 

Bottom line the small orifice can’t be avoided and unlikely still but still possible to block hence fuel strainer should be before the orifice. I’ll be checking and changing if needed on mine.

 

Magical thinking. 🙂 That was sure a dumb idea with that line. Not a shred of critical thought. Even if it went forward to cool airflow and through a little fuel radiator you’d still be left without an exit for vapour/ bubbles. Just has to go all the way back to tank with breather.

Edited June 16, 2022 by Mike Gearon

[RFguy]

any sort of fluid flow regulator in fluid world that doesnt involve a small orifice ?

 

[Thruster88]

Tesla valve? 

[RFguy]

https://en.wikipedia.org/wiki/Tesla_valve

 

https://www.machinedesign.com/mechanical-motion-systems/article/21164409/the-tesla-valve-bringing-back-a-forgotten-invention?gclid=CjwKCAjwqauVBhBGEiwAXOepkZbukSSZX8V3NxOmS2O7OQMISEit3U7EtPogZPL3nafKZlELvH2I1BoCJKcQAvD_B

 

I am sure there will be plenty of people here with backgrounds that can suggest something to return at 1 litre per minute over a wide range of pressure.

Edited June 16, 2022 by RFguy

[facthunter]

Not so easy. Everything added makes something else to go wrong.  Nev

[Garfly]

 

 

[Garfly]

 

While looking for that anti-heat-soak cowl-flap story for re-posting in Skippy's  Linear Actuator thread I was taken back to the main topic of JG3's original thread: Prop Stopped.  I reckon it's probably worth a bump; some interesting discussion around whether we should, from time to time, practise real dead-stick landings.

 

And then, out of the blue, I came upon this example.

(I see the instructor returned the switches to ON ready for a restart if needed) :

 

 

 

Edited Thursday at 08:43 AM by Garfly

[facthunter]

It wasn't legal the last time I looked. The difference depends a lot on engine idle speed. So does the landing roll.  Nev

[RFguy]

at least from where they are, that should be an easy for any pilot.

But ya do need to  do them regularly to be regularly successful.

I find that doing them with some wind around is useful - IE adding the requirement to think about the wind . When I practice and end up short, its usually because I forgot to take into account the 10 kts at 500', which can make a difference....

 

Some are hesitant  when a bit high on final, to point the nose at the ground and / or use a slip near the ground in order to increase the rate of descent- still thinking about a 500fpm descent rate....

 

 

 

 

Edited Thursday at 09:13 AM by RFguy

[JG3]

I did it again a couple of days ago as part of my New Year flight. Climbed to 4000 ft to greet the sunrise then switched off and silent glide down to spot-on landing exactly where I intended. Of course I flipped the switches back to ON as soon as the engine stopped. Great experience! 

Good feeling to know that I can do it if ever needed for real. 

[RFguy]

JG3, any idea  how different is your sink rate with prop stopped versus idle ? . I do a glide whenever there is no one else  in circuit.  Not too polite a manoeuver, otherwise.

 

 

 

[JG3]

The sink rate is distinctly greater with prop stopped. Long ago I did careful measurements but don't have those figures to hand these days.

Flying from our quiet country airstrip, no one else flying early on New Years morning, maybe heads under pillows....

[RFguy]

I read there is a crossover point with faster aircraft , and that prop stopped is more drag than prop idle    for airplanes with 70-90 kts (for example) best glide. Your best glide would be , what , 50 kts clean ?

[Garfly]

25 minutes ago, JG3 said:

The sink rate is distinctly greater with prop stopped. Long ago I did careful measurements but don't have those figures to hand these days.

Aren't those the figures you reported in the original post of this thread (4 years ago)?

 

"For the Savannah, 50kts is the speed for best glide ratio, as determined by earlier testing.
Times recorded for these tests are - at idle 101 seconds, at prop stopped 94 seconds.

At idle -           101sec/1000ft = 594fpm descent rate = 8.5:1 glide ratio @ 50kts.
Prop stopped - 94sec/1000ft = 634fpm descent rate = 7.9:1 glide ratio @ 50kts.

So for each 1000 feet of descent, the aircraft will glide 8,500ft at idle or 7,900ft with prop stopped. So that’s 600ft (182m) less distance at prop stopped than at idle."

 

 

Edited Thursday at 10:51 PM by Garfly

[JG3]

Yes, that's correct. Good find.

[JG3]

Maybe should add that with a Rotax engine the prop will stop without power, no way to keep it milling.

[facthunter]

Plan to touch down about 1/3rd into the field.. Better to hit the far fence at walking speed than hitting the near one at flying speed.   IF there's a head wind you must fly faster where that affects you. Has anyone checked whether it's legal or not?  Nev

[turboplanner]

25 minutes ago, facthunter said:

Plan to touch down about 1/3rd into the field.. Better to hit the far fence at walking speed than hitting the near one at flying speed.   IF there's a head wind you must fly faster where that affects you. Has anyone checked whether it's legal or not?  Nev

Is it legal?

[facthunter]

To deliberately stop  the prop  I've mentioned it before. Thread topic is "Prop stopped" . Nev.

[Garfly]

 

 

Unintended touchdown

WWW.FLIGHTSAFETYAUSTRALIA.COM

---

As it was a nice day, I thought it would be good to take the plane out for a trip around the local area and was wondering about performing an engine-off landing as I had practised doing them now and again quite...

 

[turboplanner]

Does ANYONE know if it's legal?

[facthunter]

Good question.   Nev

[onetrack]

Page 30 on the following document clearly outlines the rules for shutting down a perfectly good engine during flight.

 

https://www.casa.gov.au/sites/default/files/2021-08/plain-english-guide-part-91-new-flight-operations-regulations-interactive-version.pdf

[kgwilson]

I have had instructors turn the engine off when performing a BFR though I've no idea of the legality of doing so. I have done the same to check glide performance and really didn't find any difference. There may have been a little but it wasn't obvious. The important thing is to turn the Mag switches back on as soon as the prop stops just in case you need a quick start