Backups- electric and jet for single engined airplane

[RFguy]

back of the envelope....with lift proportional to velocity squared, to be useful, to extend glide range, this means (I think) airspeed has to be above the best glide speed because the wing isn't going to do much for you at low speeds. as you point out Nev, unlike the boat....you cant just fly home at 5 kts above the stall speed because the wings dont do much at low speeds without high drag devices used to improve lift. And you need power to overcome drag. I imagine there are maximum glide distance and also minimum decent rate options on unpowered descent ?

[facthunter]

Your best glide speed depends on the planes AUW at the time and the wind component existing. IF you must have a headwind expose yourself to it for the least time. Conversely if you have a tailwind letting it help you longer is more efficient. Applies when going X country as well. Nev

[Kenlsa]

all well and good...................we are still limited to one engine, 10 Rega/c excluded I think, but they will struggle to make the weight.

ken

[RFguy]

I'll need to read up on fixed wing flight 101 in aeronautical engineering texts to figure out what thrust is required to maintain some descent rate x. Which also means knowing quite alot about the aircraft but some gaps can be determined plugging in the known parameters. As it is not a simple power/rpm/airspeed. The interaction of prop thrust prop efficiency with rpm and airspeed is an interesting one.

 

However! users might know what prop RPM or engine power % can hold some descent rate x and what speed that is for what aircraft....

 

Actually my earlier comment of likely needing to be above best glide speed is not correct, since alternate lift/drag configurations could be generated by varying AoA, and substituting increased drag with a little bit of electric motor power.

 

I'll leave that one for the moment and concentrate on improving reliability with engine instrumentation.

[pmccarthy]

I once stood behind an electric model jet aircraft and nearly got blown over. If you ducted that into your carb it should boost something.

[facthunter]

If you have the aircrafts weight and lift coefficient Or still air glide performance you can work out what thrust it needs to. maintain height.. Might be about 10% of its mass for an average thing? Nev

[RFguy]

If you have the aircrafts weight and lift coefficient Or still air glide performance you can work out what thrust it needs to. maintain height.. Might be about 10% of its mass for an average thing? Nev

Somewhere around 12-13% for aircraft of LSA ilk.. from my first calcs... yeah. The 500kG aircraft of LSA breed is going to need a minimum of about 60kg of thrust. as the wings get bigger, which are in the denominator on the equation, the number falls. Am calculating a bunch of zero lift drag coefficients, lift/drag and liftMax for a few Jabs, I'll see where the numbers come out. The zero lift drag coefficient is surprisingly small.

 

That 25kg thrust EDF is pretty good for 3.5kg ! Two of those and you might stay in the air for quite a while longer than without. One will buy you time.

 

Now , Ken's point- we are only allowed one engine. I bet the regulations would be behind what is possible and it would be arguable grey. You can usually win a 'safety' argument with more safety.

[facthunter]

I wouldn't be betting my Sheep Station on it To keep the Country aspect, I reckon you are barking up the wrong tree. You don't have time to muck around with gadgets at low levels and the 45K stall speed means if there's any headwind at all and even a slight ground run, you will hit something well below 45 knots. Nev.

[RFguy]

I wouldn't be betting my Sheep Station on it To keep the Country aspect, I reckon you are barking up the wrong tree. You don't have time to muck around with gadgets at low levels and the 45K stall speed means if there's any headwind at all and even a slight ground run, you will hit something well below 45 knots. Nev.

agreed. 45 kts is tame.