Jets - What's The Next Generation?
 

The turbine fraternity is without doubt "top of the food chain". The exhilaration and attraction are simply dynamite show stoppers, , , end of story! You guys are the elite of what most modelers fantasize on.

Now that I have you sitting on the right hand of God

I'd like to start a discussion on the technological developement of jet models. What is the next step of advancement?

Stage 1 -
I guess it all starts with Ducted Fans. As far as I'm concerned Bob Violett is #1 in his developement of ducted fans and his A4, many many moons ago.
Stage 2-
With the advent of turbines, we now see alot of models with a big 5" or so engine cavity, that can easily be converted to the smaller dia turbines.
Stage 3-
All out aircraft specifically design for turbines.
Stage 4- ??????

I still see one common problem with todays aircraft. They consume alot of fuel, hence a bigger wing loading on take off. This inherent problem lends itself to the low flight times. In general, it's a heck of alot of money for say 7-8 minutes of flight time. It's not really much "bang" for the buck.

To take technology to the next level how could this flight envelope be improved?

Thats the nature of jet engines. The engergy used to compress the air is very high.

I think the next big area will be electric jets. Multi stage impellers and multi motor units. Still 6-7 minute flights will be the norm.

Another thing they need is retractable landing gear that last more than a few flights.

The other thing that will open the market will be low cost/light weight 6-7 pound thust turbine engines. Maybe higher thrust levels at lower volocity speeds.

Hi Mike

I'm just brandy new to the jet fraternity, so my knowledge is very limited at this point. However, if you want my 2 cents worth (1.8 cents US), here it is:

If turbines do to you what they do to me, I think that 7-8 minutes is an awsome 'bang for the buck'. In addition to this, and from what I understand, due to the concentration involved and the resulting stress of flying an $8-10 K bill at around 200 mph,,, 7-8 minutes is actually quite a long time.
(especially when you're a rookie as opposed to a veteran)

With that said, I'm with you as far as wanting a little longer flight time. Although my solution is far from technical, my 'quick fix' is to buy a bigger airframe/turbine that will allow for bigger fuel cells. Besides, when it comes to R/C, I've always felt: Go Big or Go Home :D

Steve

What if a scale type of jet was larger. You would be able to carry more fuel for longer flight times. Yes your wing loading would also go up, but what would be a break even point for fuel vrs wing loading. ie: to achieve a 15 minute flight envelope as being a normal advancement. (estimating about 10 oz per minute at full demand), or is this totally impossible within MAAC weight limits.
Also, do all the turbines have only a single stage compressor?

Couple of things to consider:

1. Flight times with turbines are generally longer than we could get with ducted fan not so many years ago.

2. Fuel efficiency has improved very much, it's not uncommon to see 15 minute flights on a jet.

3. As Steve said, after 7 minutes or so you are starting to go a little numb if you've been rocketing around at 180 mph +, it's time to land anyway, ever notice how pylon racing only lasts a little over a minute ;)

4. If you're not worried about flying an entire flight at 180mph + you can extend your flight time considerably. Turbines are pretty fuel efficient at half throttle.

5. We are now more power hungry than ever. Ever notice how a plane like a Bandit which would fly fine on a 12lb thrust ducted fan is now using 30lb thrust engines? Jet pilots are willing to sacrifice some of that flight time for the ultimate jet performance, but if you want longer flight times, put a PST600 into a Bandit and you'll get 20 minutes with the tanks in a bandit.

6. The extra wing loading isn't really a big deal, it's most noticable on landing, so the trick is, you make sure your load is lighter when landing, just like a full scale jet. Landing with full tanks makes even full scale jets land faster. With tanks empty, a turbine powered jet isn't that much heavier than the same airframe with ducted fan power. Adding 5lbs of fuel might seem extreme, but we've also doubled our thrust from ducted fans in most cases, so the jets still have no issue with taking off and flying.



Fuel economy has improved, and so has thrust. The old Golden west, JPX, etc turbines burned as much fuel as many of the 18lb thrust engines of today, the difference is those old turbines only produced 7 or 8 lbs of thrust.

Thank god jet fuel is cheaper than glow or it would be an issue, but I don't mind burning a gallon of fuel in a 10 minute flight when it only costs me about $7 for that gallon compared to $30 in glow fuel.

Really, in the RC hobby, almost anything of extreme performance goes through fuel, and carries a very small amount. Pylon racers carry enough for a race, that's it. Pattern planes carry enough to complete the sequence about one and a half times, even the giant scale 3D planes that are really competitve carry as little fuel as necessary. They are trying to get the max performance for the intended purpose, as a result, they are short flight times, sure the jets take lots of fuel for the short flight times, but look what you're getting :)

Are there known company's out there working on multi-stage compressors with corresponding multi-stage turbine rotors? any web sites showing this advancement? . . . or is everything single stage for now.
This would be a significant advancement like going from the original compressed air start designs, to todays full auto start.

I'm hoping for a turbofan that will fit in a Harrier and costs less than my house :wink:

This way no runway is needed.

Other is complete and flight tested models from off shore for under 3K.

And last will be autostart with intelligent real time feedback to monitor fuel level and other on board stuff :D


Peter

Iam with Peter, the turbofan will see quite a few 'major' performance breakthroughs and the turbofan is coming much sooner than later trust me they are very close to reality how does upto 70 lb thrust from a basic KJ66 sized engine sound :wink:
Larger turbine engines are also starting to become more and more popular and in demand which will see the gap between hobby and real world commercial/ home built aviation applications narrow very rapidly, all within next few years....

Smaller turbines i.e. 3-4lb thrust are here now and will fit stright into your parkflyer...

EDF technology is rapidly growing also as battery technology develops leaps and bounds we are now looking at certain EDF set ups capable of 12+ lb thrust easy... I predict we will see 20lb thrust EDF within next 2 years...

One thing I doubt we will see though is the initial purchase cost decreasing for these engines anytime soon, reason is lack of demand on a global scale within hobby market its more likely as any new designs appear we will see higher new product sticker prices, but what we will get for extra $$ is an overall more efficient powersystem with much longer service intervals due to increased engine performance effiency with like of turbofan which in the long term really means a less costly engine :D

Re: Jets - What's The Next Generation?
 

Personally, i have only seen 2 jets that turned my crank: 1 was a turbined powered scale F-86 flown at the 1996 NATS in Montreal (my first time seeing a turbine powered jet) and the other was a BVM Super Bandit at the 2006 Joe Nall (slow rolls at 2 feet going approx 200mph.... :D :D ....gorgeous) flown by Dave Schulman. Most of the turbine planes i've seen barely have unlimited vertical and max out around 130-140mph, which in my mind is very very boring to watch. While I do enjoy watching a 200mph jet doing its thing, i find watching a good IMAC Freestyle routine turns my crank.

On that note, do any of you guys forsee the price of the average P-80 sized engine coming down to around 2000$ (around the price of a DA100) in the future? I've always wanted to try a turbine powered sport jet in the 160mph+ range but it's still way out of my price range. Also, how much would it cost, with the market the way it is today, to get setup with a hot sport jet? (everything minus radio gear)...something like a Bandit with a P-120 or something along that line. I've seen AV8R's and I would never buy one becuase I think they are butt ugly...they are probably a great turbine trainer though. I've had a 40 size F-20 and it was fun to bore holes every once and a while.

Wish list
 

My wish list is comparable to Peter's I think.
Real time monitoring of fuel levels, full kero start, plus the almighty PRICE. Would be nice to see some highly prefab ARF types that I don't need to sell my house to buy. :) Imagine how nice it would be to get a good quality Bandit/Vigilante/Renegade/Aggressor type sport jet for $1000 bucks or less?!!
:shock: :rock: :P :shock: