Mental Math

[BengalsFan]

But I only have 1 engine, so it doesn't really matter

 

[B +]

But I only have 1 engine, so it doesn't really matter

You are right with only one engine you do not need to worry about your climb rate after an engine failure. You will have things to worry about but climb rate will not be one of them.

This thread is on the subject of mental math help for the NJA interview. Anyone interviewing at NJA should understand 2nd segment climbs and if you can quickly calculate the angle using this simple rule you will impress the interviewer. I was ask this on my interview.

As a side note I predict the Bungals will give the Dolphins a late Christmas present on Dec 30. Miami will get their one and only win of the season thanks to Cincinnati.

 

[gunfyter]

what ever happened to just landing the f*&^ing airplane?

its nice to know that after you pass the VDP on a non-precision approach without seeing the runway ... you can count on executing the missed approach once you reach the MAP. No need to be surprised since you made your decision already when you passed the VDP.

 

[Wankel7]

Any good mental math for the ...

Your 20 miles out from a crossing restriction and have to lose 10000 in that distance?

that includes GS?

 

[gunfyter]

GS/60 X Altitude/Dist = Rate of descent

You are flying a jet so you are close to:

360 6 miles per minute
420 7 mles per minute
480 8 miles per minute
540 9 miles per minute
600 10 miles per minute

take the altitude divide by the distance and multiply by the miles per minute.

Citation X 9 miles per minute X 10000ft/ 20 miles

9 X 500 = 4500 feet per minute

CJ 6 miles per minute X 10,000 ft / 20 miles

6 X 500 = 3000 feet per minute...

to descend 10000 feet in 20 miles.

 

[Wankel7]

Thats good stuff...thanks!

 

[atpcliff]

Hi!

B+: I am normally about 150 knts in 2nd segment climb-how does that work?

Also, in the climb from 1000' to 3000' agl we are normally at 200, and then after 3000' agl we're 250.

How do you figure the angle for 150/200 and 250. I'm good at math, but I only had 1 math class in college!

Thanx 4 the help!

cliff
BNA

 

[imacdog]

Cliff, you only need to find the angle required for the departure. No matter what speed you climb out single engine, just look at the 100-knot ROC on the chart. That will give you the angle of climb required for the departure. Use that angle against your single engine climb charts to see if you can do the departure. Two-engine climbs are almost always well above the requirements for the departure, so that's where your climb profiles come in. Otherwise, you're climbing at V2 until a safe altitude.

 

[atpcliff]

Hi!

Thanx 4 that explaination.

cliff
BNA

 

[B +]

Hi!

B+: I am normally about 150 knts in 2nd segment climb-how does that work?

Also, in the climb from 1000' to 3000' agl we are normally at 200, and then after 3000' agl we're 250.

How do you figure the angle for 150/200 and 250. I'm good at math, but I only had 1 math class in college!

Thanx 4 the help!

cliff
BNA

The reason the 100 knot ROC converts easily is because of the following math.
At 100 knots you will cover 10000 feet per minute.
Gradient is rise over run so if the required ROC at 100 kts is 680 fpm then 680/10000=.068 or 6.8%.
You would get the same gradient using any other of the speeds but the math would not be as easy since the distance traveled in a minute will not be the nice round number like it is at 100 kts.

 

[LogbookSlave]

A quick rule for the Vnav planning:

1000s of feet to lose X 3 (as stated previously) AT

Groundspeed X 6 (for descent rate).

500 knots groundspeed covers 8.3 nm/min. If you need to lose 30,000 feet for a crossing restriction, you need to start 90 miles prior to the restriction (30 X 3). It will take you just under 11 minutes to cover the 90 miles in the descent (10.8 to be more precise). In order to lose the 30,000 feet in the 10.8 minutes, you would need a descent rate of 2777 ft/min.

Using the gs x 6 method, at 500 kts groundspeed, you get 3000 ft/min for the descent. I like this method because it typically gives a little buffer prior to the restriction. I also reevaluate the numbers every couple thousand feet in the descent.

I'm a geek . . . I know.