How to do you calculate the ROD?

Question

How to do you calculate the ROD?

Answer 1

I use Vnav in the FMS.

Answer 2

Here are the elements:

Time to Target

Beginning Altitude

Ending Altitude

Time to target is figured based on airspeed.  If you are 20 miles out, and traveling at 2 miles per minute, then you are 10 minutes out.

If you are at 10,000 feet (beginning altitude) and need to be at 2,000 feet (ending altitude) - it means you need to descend 8,000 feet in 10 minutes, or 800 feet per minute.

Hope that makes sense.

Answer 3

Come on people, you shouldn't need a flight computer or an fms to do this.

First, always follow a 3:1 descent profile (start your descent x miles out, where x is the altitude you need to loose divided by 300).

Second, ROD = ground speed, add a 0, divide by 2

That's all you need to know.

Answer 4

to calculate Rate of Descent (ROD) you must have a distace to cover. So what ROD do you need over a specific distance. A rule of thumb that can be used (very good for VOR aproaches) 5 multiplied by ground speed (GS) assuming a 3 degree glide slope.

On the other hand, handling a ROD out of Cruise altitude is again used with GS calculated to Nautical miles. eg. 120kts GS is equal to 2 NM per minutes. Now if its over a 10 NM distance and you want to lose 5000 feet. Therefore it you cover 10 NM in 5 minutes (10nm/2nm/min). Now you would descend at 1000 feet per minute.

I hope this helps......

for me I use an Electronic Flight computer.....buying one would be an investment.