I am sure that plenty of people have downloaded the Lockheed Delta Airlines tri star which has 3 engines. I downloaded that plane and tryed to take off and I could not get the plane off the ground. so is the plane defective or is there something that I may not be doing right???

Don't pull back on the stick until the end of the runway, or your plane goes up by it self.

Allot of runway & alto of speed.
Check your flaps and I think I might have encountered this problem a while back with this aircraft. I think you do need to really play with the trim, designer something.
Try this.

Spool up the engines, as she starts to roll down the runway, the entire time keep adjusting the trim up while pulling back on the stick. I know this is not correct but at least she might take off. I think it is the AC. This happened to me. Now get up in the air and adjust the trim so you are in level flight. Go land the aircraft and leave the trim setting alone. Now take off and see if she takes off easy without the trim adjusted.
I know it is not how you fly this thing but it will confirm the trim setting is not correct  by default.

Hope it works!

Dave

return it for a refund. 

Hey Cybersurf

I love the Tristars and fly them a lot.
Yep they're beasts to get off the ground (at least
the way their written up).
First, as others have mentioned check ur weight
and fuel to ensure your not out of configuration.
Here's how I get them up:
Full flaps, full power, trim leveled out and keep the brakes on until your N1 gauges read full.
Off brakes and let er rip.
You'll still need all the rwy available but she'll
fly. I've got the newest Deltas and I also fly an
old Dragon Air from fs98. They all work well but
they're touchy.

Suerte / Nek