Well i am not to say but i find it rather easy to get this bird in the air on very short runways (15-1600meters with relativ heavy gross weight(230000kg)) so i was thinking this might not be simulated by PMDG or is it me? TOPCAT cannot perform takeoff calc for these short fields offcause.ThanksMichael Moe

Huh?

Just because you could get into the air on a short strip doesn't mean you would want commercial operations going on there. Still gotta stop at V1 and stay on pavement.

What Downs said. You may be able to get off the ground, but try going up to just before v1 speed, and cut the throttle. If you can stop on the runway, you're fine at that weight. If not, you need to be lighter. The MD-11 is actually known to be a good takeoff performer. Because of its higher V-speeds, it has a lot of power to accelerate faster to get to v1 quicker, especially at full power. Also why it has a high angle/rate of climb at takeoff

Something you need to understand about RW V1:It is adjusted for the length of the runway (+stopway,overrun). What that means is that while V1 might be 135 kias (choosen at random, not based on any calculation, just as an example) for a 10,000 ft runway, in the same atmospheric conditions, same weights, on a 3,500 ft runway the V1 would be adjusted lower. If the runway is that short, then V1 might be 65 kias. The numbers used in FS are not calculated the same way RW numbers are calculated.Another example of this is when we take the runway surface conditions into account. Hard compacted snow on the runway might drop V1 by 20 knots. Ice might drop V1 dramatically.

Something you need to understand about RW V1:It is adjusted for the length of the runway (+stopway,overrun). What that means is that while V1 might be 135 kias (choosen at random, not based on any calculation, just as an example) for a 10,000 ft runway, in the same atmospheric conditions, same weights, on a 3,500 ft runway the V1 would be adjusted lower. If the runway is that short, then V1 might be 65 kias. The numbers used in FS are not calculated the same way RW numbers are calculated.Another example of this is when we take the runway surface conditions into account. Hard compacted snow on the runway might drop V1 by 20 knots. Ice might drop V1 dramatically.

That's right! completely forgot about that.

thanks for explaining this Michael Moe

Just out of interest, how did you land on that very short runway you want to take off from?

According to TOPCAT (again, not the same calcs as RW), landing is doable on a 5300 ft runway, zero wind, standard day. You just have to be be nearly empty in terms of cargo and fuel. I'm having trouble getting it to spit anything out for a runway less than 6000 ft for takeoff though. I think you could do it, it just might not meet any regulatory requirements for required runway length.

If you can barely squeeze in when light and empty, why would you want to land there in the first place? You can't take on cargo or passengers and you can't even refuel.

Could be a small field attached to an aircraft bone-yard, or some other random "non-routine" mission. Besides this is FS... there's still always "just for the fun of it." :-)Every year there's a 747 parked in Lexington Kentucky for the Kentucky Derby. The Saudis use it to bring their horses over. That runway's a little longer, but not long enough for them to get back out with enough fuel to go home. They have to stop and get more fuel somewhere with a nice long runway before leaving the US. There's always some random mission.