Two interview questions. Help please.

[Low & Slow]

First descent rate required. Does anyone have a formula?
You're flying along at 300kts at FL240, in 12 miles you need to be at FL180, How many feet per minute descent? I can ballpark it but would like to be exact.

Also, passenger says you smell like you've been drinking whats your response?

 

[Mookie]

1. Sounds like you got slammed dunk3ed. The controller must have been distrcted by his breakfast burrito....
Pretty easy one though.
300 kts is 5 miles/minuute
12 miles at 5 per minute would take 2.4 minutes.
6000' loss in altitude/2.4 minutes =2500
(check my math please)

Better answer is 3000fpm and get to the restriction 2 miles prior!!! (or program the fms and let vnav do it for you)

2. I had this happen to a buddy once. He immediately called the chief pilot, and told him personally he wanted to be taken off of the trip and tested to prove he was innocent. Pro-active stance got him out of alot of potential trouble. Can't be too careful these days.

Mookie

 

[NDPILOT]

Here is a little different way of doing that descent problem.

Need to lose 6000 ft in 12 miles which equals 500 ft per NM

Just like those departure climb gradient problems

divide 500 by 60 and multiply it by your groundspeed

500/60 x 300 = 2499 ft/min

 

[Low & Slow]

Thanks.

Thank you for the help.

 

[azpilot]

Here's another way. From the Rules of Thumb page on this site:

Subtract crossing altitude from present altitude times three.

Example: cross PVD at 11000 and your present altitude is 20000. 20000-11000=9000, 9000/1000=9 9x3=27nm. So start descent 27nm from PVD.

For descent rate multiply your groundspeed times 6.
Ex: Your groundspeed is 300kts times 6= 1800fpm.

 

[rgnlwannabe]

I was thinking the 3/6 rule myself, but if you take 3x6 (altitude to be lost), you get 18 miles, but you only have 12 miles, so 1800 fpm would not be enough to get you down in time (6x3 for descent rate). So I guess you would have to use one of the other ways above for this question. probably done on purpose so the 3/6 rule doesn't work