Top of descent

Not a problem getting to cruise alt. However it has become a problem when to descend. I use a approach plate to determine approx 10 miles from the airport. Is there an easier way?

Your altitude divided by 3 usually tells you when to descend,

A good flight plan program should give you that point based on your aircraft.

I just wing it. ;-)

 

 

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Top of descent: Desired altitude to attain on descent,

Ex: If at FL300 and descending to 10,000: 30,000-10,000 = 20,000.

20 x 3 = 60NM. Then you figure the rate of descent to achieve the desired altitude within

60NM. Multiply your ground speed by 6 to get that answer

No easy way unless, as stated, you wing it. It's complicated if fact:

 

Current Flight Level - Target Flight Level = difference

 

difference / Decent Rate = Time needed for decent in minutes

 

Time (/60)in tenths of an hour * IAS = NM needed for Decent

 

NM for Decent + NM Target from end of RWY = Required Distance for Decent

 

 

Example with rough rounding:

21000 FL - 2000 = 19000

 

19000 - 1200 = 15.833

 

15.8/60 = 0.264

 

220 IAS / 0.264 = 58.06 NM

 

58.06 + 10.1 NM from RWY (last waypt)

 

= 68.16 NM

 

 

I only use it for the higher altitudes to give me a chance at getting to the runway without a nose dive.