I disagree with the assumption that the F-35 is single engined only to the services requirements. The US Navy has a twin engine requirement for over water operations.
I said it was based on the common design of all three varients and this only confirms it, since the USN had to compromise and take a single engine fighter, "against" their own requirements, since the main design was meant to replace single engine F16s and Harriers in the USAF and USMC. If the USN had the possibility to get an own stealth fighter, they would have opted for a twin engined.
The F/A-18E has two engines that produce 98 Kn.. the F-35 has one that produces 191Kn both at AB.. Yet the F-35 carrying two bombs and two AA missiles... flies farther than the F-18 and has better T/W in that configuration.
Actually it is meant to replace the Hornets, not the Super Hornets and they are lighter than the F35C, faster has a better TWR and recent reports said that the acceleration should be less too. The range might be higher, but the final specs of the F35C needs to be seen, the Pentagon corrected that downwards several times now.
You CANNOT value performance as a measure of the number of engines a fighter has.
I didn't said it generally, but for stealth fighters, which carries much higher basic weights than an F16s for example, which is also a medium class fighter with a single heavy engine. The F16 still is very agile and maneuverable, since it's basic weight is pretty low, a stealth fighter on the other side has to counter the higher weight with the power of a single engine only. That was even critizised even by US experts, that the F35A won't be able to match the flight performance of the F16s it will replace and PAF with the F16s and JF 17 is used to good flight performance, so do you think they will compromise with less?
Anyway, I am pretty sure that PAF will go for J31 anyway, for some commonality advantages to the JF 17 fleet and since PAF can't develop an own 5th gen fighter, nor is there currently another single engined stealth fighter under development, there hardly won't be a choice anyway.
The reason why all these large 5th gen projects are going for Twin engines is simply because at this stage there is no single engine powerful enough besides the F-135 and F-136 to produce the thrust needed to get an aircraft that carries all those avionics, weapons and RAM shaping measures and so on .. aloft by itself. Hence , you develop two engines that give it enough thrust to perform those tasks.
Exactly, but even these F35 engines doesn't produce enough thrust to offer good flight performances, but that simply wasn't the aim of the fighter anyway.