Can someone provide a formula for "Rate of Descent?"

[HizExceLenCy]

It would be so much easier to have this in a spreadsheet.

What I'm looking for is a formula that would tell me when I'm at "Top of Descent" i.e. or how far out from the airport, for example, I have to be to start my descent.
Also, I'd like to know my rate of descent, (ROD)

And if it's not too much to ask, how long will the descent take? (in minutes)

Thanks in advance,

HizExceLenCy

 

[shg]

[Table="width:, class:grid"][tr][td="bgcolor:#C0C0C0"][/td][td="bgcolor:#C0C0C0"]

A​

[/td][td="bgcolor:#C0C0C0"]

B​

[/td][td="bgcolor:#C0C0C0"]

C​

[/td][td="bgcolor:#C0C0C0"]

D​

[/td][/tr][tr][td="bgcolor:#C0C0C0"]

1​

[/td][td="bgcolor:#F3F3F3"]

​

[/td][td="bgcolor:#F3F3F3"]

Units​

[/td][td="bgcolor:#F3F3F3"]

Value​

[/td][td="bgcolor:#909090"][/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

2​

[/td][td]

Descent Ground Speed​

[/td][td]

kts​

[/td][td]

130​

[/td][td][/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

3​

[/td][td]

Cruise Altitude​

[/td][td]

ft MSL​

[/td][td]

10,000​

[/td][td][/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

4​

[/td][td]

Descent Rate​

[/td][td]

ft/min​

[/td][td]

500​

[/td][td][/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

5​

[/td][td]

Threshold Altitude​

[/td][td]

ft MSL​

[/td][td]

600​

[/td][td][/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

6​

[/td][td]

Descent time​

[/td][td]

m:s​

[/td][td="bgcolor:#E5E5E5"]

18:48​

[/td][td]C6: =(C3-C5)/C4/1440[/td][/tr]
[tr][td="bgcolor:#C0C0C0"]

7​

[/td][td]

Start descent​

[/td][td]

NM​

[/td][td="bgcolor:#E5E5E5"]

41​

[/td][td]C7: =C2*C6/"1:00"[/td][/tr]
[/table]

That assumes you're making a straight-in approach.

 

[HizExceLenCy]

[TABLE="class: grid"]
<tbody>[TR]
[TD="bgcolor: #C0C0C0"][/TD]
[TD="bgcolor: #C0C0C0"]

A​

[/TD]
[TD="bgcolor: #C0C0C0"]

B​

[/TD]
[TD="bgcolor: #C0C0C0"]

C​

[/TD]
[TD="bgcolor: #C0C0C0"]

D​

[/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

1​

[/TD]
[TD="bgcolor: #F3F3F3"][/TD]
[TD="bgcolor: #F3F3F3"]

Units​

[/TD]
[TD="bgcolor: #F3F3F3"]

Value​

[/TD]
[TD="bgcolor: #909090"][/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

2​

[/TD]
[TD]

Descent Ground Speed​

[/TD]
[TD]

kts​

[/TD]
[TD]

130​

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

3​

[/TD]
[TD]

Cruise Altitude​

[/TD]
[TD]

ft MSL​

[/TD]
[TD]

10,000​

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

4​

[/TD]
[TD]

Descent Rate​

[/TD]
[TD]

ft/min​

[/TD]
[TD]

500​

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

5​

[/TD]
[TD]

Threshold Altitude​

[/TD]
[TD]

ft MSL​

[/TD]
[TD]

600​

[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

6​

[/TD]
[TD]

Descent time​

[/TD]
[TD]

m:s​

[/TD]
[TD="bgcolor: #E5E5E5"]

18:48​

[/TD]
[TD]C6: =(C3-C5)/C4/1440[/TD]
[/TR]
[TR]
[TD="bgcolor: #C0C0C0"]

7​

[/TD]
[TD]

Start descent​

[/TD]
[TD]

NM​

[/TD]
[TD="bgcolor: #E5E5E5"]

41​

[/TD]
[TD]C7: =C2*C6/"1:00"[/TD]
[/TR]
</tbody>[/TABLE]


That assumes you're making a straight-in approach.

Will this work for jets?

 

[shg]

It will work for jets, helicopters, eagles, and butterflies if they all plug in appropriate numbers.

 

[shg]

... aside from the fact that jets fly at flight levels, not MSL altitudes.

 

[HizExceLenCy]

Thanks, for putting the spreadsheet together for me, and everyone else.

Could you explain to me the formulas you used?

Thanks.

HizExeLenCy

 

[shg]

Time to descend is the change in altitude divided by the descent rate. The 1440 converts decimal minutes to an Excel date/time.

Distance to descend is time to descend times speed.

 

[HizExceLenCy]

Thanks I appreciate the help.

HizExeLenCy

 

[shg]

You're welcome.

 

[HizExceLenCy]

Sorry to open up the thread again. I'm having a problem with what I see and how Excel is interpreting the data.

For example: To descend 4000 feet at 2000 feet per minute (fpm) will take no more than 2 minutes. The problem is, Excel returned a value of 2, but Excel thinks that means 48 hours, or 2 days; not 2 minutes.

Can I upload the file, so someone can have a look at it?

HizExceLenCy