How is PFH computed ?

[Emmanuel]

Dear all,

I'm looking for some informations about the way the PFH is computed.

Is PFH approximated by w(t) ? If that's true then is w(T) = F(T) / T ?

With

    PFH = Probability of failure per hour;
    w(t) = Unconditional Failure Intensity;
    F(T) = Unreliability;
    T = mission time.

Thank you.