Not done this specific journey but have done lots of connections. I personally wouldn't go for a 1 hr 50 mins connection - it can be done but you need everything in your favour.
On arrival in PHL you first of all clear US Immigration where wait times of up to an hour are not uncommon (it all depends on what other flights arrive when you do), collect bags, clear US Customs, return bags to US Airways (there should be a drop off point just after customs) and get to your departure gate which will probably involve going through airport security.
I normally allow 3 hrs for this - it can be done in less but it all depends on queues on the day, try to sit near the front of the plane from Man to get to the head of the immigration queue.
If you miss the connecting flight then US Airways will put on the next available flight which might not be the next flight as they won't bump passengers to seat delayed passengers.
You might find that your schedule changes before you travel which could solve the problem or reduce the connection time even further.