How much weight will an aircraft powered by a JDE54 or similar engine fly well at? Are there any rules-of-thumb for thrust to weight of these highly loaded planes?

How about a Dynamax / OS 91; how much weight will they fly and still have good vertical performance?

Eighty-some views and no other replies. These guys must be sleep surfing thru the threads

IMHO jets are no different than any other airplane when talking about thrust to weight and wing loading. Lighter is better and the more thrust to weight you can get the better.
I think the MAX weight you would want to try to fly with the Wren/JDE 54 or a Dynamax/91 would be about 18 lbs wet.

My personal rule of thumb for thrust to weight is 0.75 min wet.
So at 12 lbs engine thrust max aircraft weight would be about 16 lbs wet.

Im sure some other more experienced flyers could offer some actual numbers on different kits/models.

Cheers,
James

You also have to keep in mind the fact that a Turbine's thrust will not decay as will a Ducted Fan's thrust. Also, with the turbine, you'll loose airframe weight quickly as the fuel burns-off.

Craig

It's kinda hard to figure out the point of the question and the question can't be answered until we know where you want to go. You hint at vertical performance, but there's so many factors....

Many modern airplanes, like 747's, are flying at T/W ratios as low as .25 and lower. Actually you can go lower, it's only a question of takeoff roll and drag. It also depends greatly on wing loading and total surface area (wetted area = prime source of drag). Of course a higher T/W is better, except that leads to other considerations like costs, structures, flutter, fuel load, etc.

I did a 14' wingspan twin ducted fan flying wing at 50 lbs. The measured installed thrust, using a lab force guage, flat out was 13lbs, both engines together. Nothing like the expected 20 lbs you would guess from all the hype. So we flew at .25 T/W. T/O roll was 300' and in flight speed at 100 mph+.

T/W isn't the only measure of performance or airworthiness. 12 bs of thrust can fly a 30 lb airplane if you want, it might even have great vertical performance if you get a good entry speed and have a low drag planform. Best though if you stick to the smaller sized jet kits.

Thanks guys! i have a dynamax / OS 91 I'm going to build something for, I think I'll start with a Skyburner. Looks like it will have to be kept light to have aerobatic performance and to do large diameter loops. The ducted fan planes that I've seen fly seem to loose airspeed pretty easily unless they just fly a racetrack pattern.