Hi,
if I read my manual, it says "... a takeoff alternate is available within a range of 1hr flying time at single engine cruising speed based on the actual takeoff weight, still air and standard conditions."
I stand to be corrected (I consulted some colleagues), but this means that "1hr" is only a value to calculate the range, while it is not a "time limit".
If your FPPM says your single-engine ground speed is 300 kts for the given weight, you can take an aerodrome located 300 NM from your departure airfield as your takeoff alternate. And you will not reach this alternate within 1hr, since your speed during climb and descent/approach will be less.
If your OM doesn't state any specific company value (range), the procedure would be :
- take the TOW
- take the cruising flight level you will fly to clear terrain
- refer to the One Engine INOP LRC table in the FPPM to obtain the single engine cruising speed
- multiply speed (kts) by 1 hour = distance/range (NM)
Perhaps I am wrong, just let me know,
Pat