Hi, the JF-17 ejection seat is one of the best out there, made by Martin Baker. In a previous issue of Air Forces Monthly, there was a special on the JF-17. In it was a section on the ejection seat. It mentioned the PAF had specifically selected the Martin Baker PK16LE carbon/fiber alloy seat for the JF-17. In addition, the PAF had retrofitted their initial small batch production JF-17 Chinese TY-6 ejection seats with these ones.
A quote from Air Forces Monthly July 2011 Issue, page # 66:
"When the carbon/fibre alloy Martin Baker PK16LE ejection seat was selected for the JF-17, the PAF requested that there be some upgrades -- covering four main areas: passive leg restraints, the back rest extended by three inches with more cushions to increase comfort levels, a rearward firing headbox and drogue as well as an electronic sequencer.
From early 2008 until 2010, Martin Baker set about introducing these changes to the standard MK16 ejection seat to enhance its performance to provide the PAF with one of the most advanced ejection seats available. Several full ejections were performed across the speed range from zero to 600 knots to qualify the changes to the seat and verify its improved performance."
The Martin Baker PK16LE ejection seat in the JF-17 is a zero-zero seat, meaning the pilot can eject while the plane is stationary and on the ground. However, there are limits to when a pilot can eject, given the speed of the plane.
Lastly, in regards to the plane being inverted at the crash site, that does not automatically mean the pilot ejected in an inverted position. The plane was reportedly on fire, and could have been spinning and landed on its back. We do not have much information on that, and only a PAF inquiry board can determine the causes of the parachute not opening.