Post by Tom Goodrick on Dec 12, 2010 16:41:02 GMT -5
I downloaded from avsim an airplane that turned out to be very badly done. I tried fixing it but gave up after finding it was unstable with divergent pitch oscillations at high altitude. I have tried fixing that problem in the past but it is very much like chasing your tail. I dumped the plane.
It was Gulfstream G100 jet. It looked pretty good unless you looked closely. Then you saw a crack along the leading edge of the wing through which you could see the nicely done interior! The problems became evident as soon as I looked in the aircraft.cfg at the weights. The G100 is a new name for the old IAI Astra SPX that I have had for several years. I wanted a new model of it for use on the laptop. I tried emailing it to myself but it got lost in cyberspace.
The problem was it listed the gross weight as 51,500 lb, the empty weight as 44,000 lbs and the payload as zero. If you caqrried more than 50% fuel you'd exceed MTOW with just the crew. Also, the MTOW of the Astra is 23,650. That problem was the tip of the ice berg. The geometry was all off by a similar proportion. The MOI's were 100x too big. I don't know if the designer screwed up his conversion factors from meters and kilograms or if he just copied the specs for a different aircraft.
I fixed the weights, the engines and the major geometry items so it would fly nicely at low speeds and altitudes. But when I first climbed above 30,000 ft it diverged in pitch and did flips. I set the pitch stab factor to 1.6. It was good at 26kft and 30kft. At 34kft it oscillated 2 deg in AoA. At 38kft it oscillated 3 deg in AoA and 500 fpm in vert rate (while level). This was with the autopilot ON. I turned the autopilot OFF and it flipped 40 degrees in pitch and would have broken up if I allowed such a thing.
This crap has the file name ld-g100.zip. It's a shame. It looked nice on the ramp with the airstair door open - nice interior.
Oh well, I have a nice Hawker 800 and Learjet 60 as well as a G IV. They'll do.
It was Gulfstream G100 jet. It looked pretty good unless you looked closely. Then you saw a crack along the leading edge of the wing through which you could see the nicely done interior! The problems became evident as soon as I looked in the aircraft.cfg at the weights. The G100 is a new name for the old IAI Astra SPX that I have had for several years. I wanted a new model of it for use on the laptop. I tried emailing it to myself but it got lost in cyberspace.
The problem was it listed the gross weight as 51,500 lb, the empty weight as 44,000 lbs and the payload as zero. If you caqrried more than 50% fuel you'd exceed MTOW with just the crew. Also, the MTOW of the Astra is 23,650. That problem was the tip of the ice berg. The geometry was all off by a similar proportion. The MOI's were 100x too big. I don't know if the designer screwed up his conversion factors from meters and kilograms or if he just copied the specs for a different aircraft.
I fixed the weights, the engines and the major geometry items so it would fly nicely at low speeds and altitudes. But when I first climbed above 30,000 ft it diverged in pitch and did flips. I set the pitch stab factor to 1.6. It was good at 26kft and 30kft. At 34kft it oscillated 2 deg in AoA. At 38kft it oscillated 3 deg in AoA and 500 fpm in vert rate (while level). This was with the autopilot ON. I turned the autopilot OFF and it flipped 40 degrees in pitch and would have broken up if I allowed such a thing.
This crap has the file name ld-g100.zip. It's a shame. It looked nice on the ramp with the airstair door open - nice interior.
Oh well, I have a nice Hawker 800 and Learjet 60 as well as a G IV. They'll do.