Mental math for crossing restrictions..??

[tathepilot]

I'm looking for a few formulas..

 

[Snapshot]

3-to-1 works well on descent.

Three miles for every thousand feet you've got to lose.

10,000ft will take you 30 miles. Adjust 1 mile for each 10kts of wind.

15,000 ft to lose with a 20 kt headwind will be 43 miles. (15x3) -2

 

[RP170]

I'm looking for a few formulas..

You can take the altitude you need to lose divided by 1000 and multiply it by 3.

Example:

You want to descend from FL350 to FL200. Take 15 x 3 = begin descent 45 miles out.

Multiply your ground speed by 5 to determine the approximate ft/min descent rate for a 3.0 degree glide path.

 

[bluefishbeagle]

When you get the crossing restriction:

1. Flight idle
2. Spoiler extend
3. MMO or VNE whichever is less

At any time if Center asks if you can make it:

1. Say "no problem"
2. Gear down
3 Flaps extend
4 Pray.

Never missed one yet

 

[tathepilot]

When you get the crossing restriction:

1. Flight idle
2. Spoiler extend
3. MMO or VNE whichever is less

At any time if Center asks if you can make it:

1. Say "no problem"
2. Gear down
3 Flaps extend
4 Pray.

Never missed one yet

Yeah, huh..

 

[BushwickBill]

I'm looking for a few formulas..

Groundspeed add a zero /2 gives you 3 degree glide path.

400 knots = 4000/2 = 2000 fpm for a 3 degree decent

Altitude to loose 410 to cross "BAILL" at 11,000

30,000 / 2000 fpm = 15 minutes out from your crossing restriction begin decent.

Or you can press VNAV on the G530 and it will do it all for you.

 

[Papps]

Groundspeed add a zero /2 gives you 3 degree glide path.

400 knots = 4000/2 = 2000 fpm for a 3 degree decent

Altitude to loose 410 to cross "BAILL" at 11,000

30,000 / 2000 fpm = 15 minutes out from your crossing restriction begin decent.

Or you can press VNAV on the G530 and it will do it all for you.

I don't think about it in minutes but i do something similar.

410 to cross baill at 11000. 30000' to loose thats 90miles out.

If im averaging 400 knots GS I add a zero to 400 (4000) then divide by 2. 2000fpm

so 90miles from baill i start a 2000fpm descent.

 

[tathepilot]

You can take the altitude you need to lose divided by 1000 and multiply it by 3.

Example:

You want to descend from FL350 to FL200. Take 15 x 3 = begin descent 45 miles out.

Multiply your ground speed by 5 to determine the approximate ft/min descent rate for a 3.0 degree glide path.

I like this one, I'll give it a shot tomorrow..

 

[tathepilot]

.................

 

[tathepilot]

I don't think about it in minutes but i do something similar.

410 to cross baill at 11000. 30000' to loose thats 90miles out.

If im averaging 400 knots GS I add a zero to 400 (4000) then divide by 2. 2000fpm

so 90miles from baill i start a 2000fpm descent.

If you get a crossing restriction when you are 90 miles from the fix, are saying that you start a descent as soon as you get the restriction..??

BushwickBill used 90 miles as an example of when he got the crossing restriction. How does 90 miles fit into your example..??

 

[30West]

If you get a crossing restriction when you are 90 miles from the fix, are saying that you start a descent as soon as you get the restriction..??

BushwickBill used 90 miles as an example of when he got the crossing restriction. How does 90 miles fit into your example..??

90nm is 3x the altitude to be lost, or 30,000. Another way of stating the 3 to 1 rule.
To cross Baill @11000 you would leave 410 approximately 90nm from Baill.

 

[MrSky]

Here's what I like use...

Altitude to descend to fix, divided by 5000. Say your at 35,000 and need to cross BOZZO at 10,000 and 250k (25,000 / 5000 = 5)

Take the result, then when you get about 5 min from BOZZO, do the following...

1. Deploy Inboard Reverser's to Reverse Power Stop
2. Hold VMO
3. Shut up the screaming jumpseaters (or your engineer)
4. Level off, Stow Reverser's
Then you have about 10 miles to slow to 250k

No Problem, works every time!

 

[Papps]

If you get a crossing restriction when you are 90 miles from the fix, are saying that you start a descent as soon as you get the restriction..??

BushwickBill used 90 miles as an example of when he got the crossing restriction. How does 90 miles fit into your example..??

No you would probably get that clearance 150 miles out or further. But when the plane says your 90 miles from the fix, you start down.

 

[BushwickBill]

The phrase you want to hear is N1234A descend 240 at pilots discretion expect ABCDE at 11,000. BTW ABCDE at 11,000 is on you arrival plate and you should have been thinking of that a long time ago. Then you can wait until your going to need a 2000 fpm decent and start down. The logic is that you'll save tons of fuel and maintain a higher true airspeed by staying up high.

Whats with you guys using distance? Nothing wrong with it but I have always used time. It is available for both DME and GPS, although we rarely use DME unless the procedure calls for it. Since your true airspeed is decreasing in the decent your not going to get an exact time to start down anyway.

 

[acaTerry]

Altitude Selected

VNAV

Execute