X-ing restrictions

[Knob]

I used to use the ALT to lose * 3, GS * 5 to make crossing restrictions in the EMB-120, however this can lead to descent rates of 3000 fpm or more in the ERJ. What other methods (besides the FMS) are you people using out there? Thanks.

 

[Nindiri]

The FMS is the only way to go in the CRJ. I let it show me a 3 degree descent and I use the VS to execute it. Fuel efficient and smooth ride for the pax.

 

[Sgt. Hartman]

I use altitude to loose X2 and I just keep track of my progress as I go. eg. 60 miles out at 30000 40 miles out at 20000 etc. If you get a little high or low on the profile adjust the rate of descent accordingly.

sgt.

 

[Blueridge]

If you need to do over 3000 fpm on a 3 degree descent, that implies you're doing over 600 kts gs. I'm guessing the math is screwed up somewhere. At my company, we use:

alt to lose / 3 = miles req. for descent.
rate of descent = ground speed * 5 (or 1/2 the gs and add a zero)

For example, you're at FL250 and told to cross XYZ at 110 and you're doing 440 kts gs. We would begin our descent 47 miles from XYZ and hold 2200 fpm on the way down. Assuming the winds don't change with altitude, you should be spot on with the crossing.

Hope this helps,

BR

 

[rstev1955]

I find 2000fpm is normally fairly close to a 3 degree glidepath from altitude and is a smooth ride for the PAX. It is easy to just take half of the altitude you need to lose (in thousands) and start down that many minutes before the fix. If you also need to slow down, i.e. 10000ft and 250K then start down a minute earlier.

As long as you keep updating how many minutes to the fix, you can make minor adjustments to cross it right on altitude and/or speed. The only thing you have to watch for is a decreasing headwind as you descend, which will get you to the fix quicker than you originally planned.

Another good techinique in the RJ is if you have been given an alititude below 10000ft then descend at 310K and whatever descent rate you want. When you get to 12000ft, use idle power and 1200fpm. you should get to 250K just as you are approaching 10000ft.

Cheers.

 

[Captain X]

I used to use the ALT to lose * 3, GS * 5 to make crossing restrictions in the EMB-120, however this can lead to descent rates of 3000 fpm or more in the ERJ. What other methods (besides the FMS) are you people using out there? Thanks.

How often do you see 600 Knots GS in the ERJ?

I can say i've only seen it only once or twice while descending on the "steeper" parts of an arrival into in the winter with some kick ass tailwinds.

Most of the time though I never see a descent rate in excess of 2500 FPM using the very method you describe.

Alt to Lose X 3 for distance TO BE ESTABLISHED in the descent.

Add 1 mile for every 10 KIAS above 250 (if there is a speed requirement)

Groundspeed at TOD X 5 for Rate of Descent.

Ex. FL370 to cross a fix at 10K and 250 KIAS, current ground speed 500 Knots

37-10 = 27 X 3 = 81

320 KIAH -250 KIAS = 70/10 = 7

81+7 = 88 miles out (round up to 90)

500 KTS GS X 5 = 2500 FPM

600 KTS GS would be 3000 FPM.

650 GS would be 3250 FPM

You'd have to see 700 to get to 3500 FPM

Been working like a charm for the last 5 years and never had a pax complain or felt like I was "rushing" to make a restriction.

 

[Caveman]

I put the little pink banana thingy in front of the fix and go back to reading the paper.

 

[EMB170Pilot]

Vnav or use time from FMS to the next waypoint and use 1,000 fpm or 2,000 fpm whatever...no problems

 

[CitationLover]

why are you complicating your life? use the FMS. do you make mental notes and mental gyros when flying the needles? use the FMS, it is a tool for you to use.

 

[Captain X]

use the FMS, it is a tool for you to use.

As is the grey matter 'tween your ears that you will rely on when the box takes a dump. Helps to keep it tuned up and runnin' right....

Now where'd I put that Gingko Biloba?

 

[Nindiri]

FMS inop?

Declare an emergency!

 

[ArcticFlier]

3.8 degree gs gives us about 2700 to 3100 fpm in the CRJ. Works fine for me.

I use altitude to lose times 3 if the box takes a dump. Add or subtract 1 nm for every 10 knots of headwind or tailwind. Works pretty well.

If you have to slow as well, get down early (1 nm for every 10 knots to slow) ie slowing from 320 to 250 takes 7 nm at roughly 80% N2. It's about the only time I use N2 for anything like this.

AF

 

[scotts]

If you need to do over 3000 fpm on a 3 degree descent, that implies you're doing over 600 kts gs. I'm guessing the math is screwed up somewhere........

...Hope this helps,

BR

It's closer to a 4.0 degree G/S. Used if you want to descend at idle vs. with power applied during the descent. Rate of descent varies between about 2800 and 3500.

FWIW...

 

[CitationLover]

As is the grey matter 'tween your ears that you will rely on when the box takes a dump. Helps to keep it tuned up and runnin' right....

Now where'd I put that Gingko Biloba?

well you can always double check yourself WHILE using the FMS.

and they wonder why missed restrictions lead the ASAP reports.........

and besides these are meticulously maintained airplanes. nothing ever "takes a dump".

 

[DC8 Flyer]

4 times the altitude to loose. IE 350 and need to cross XYZ fix at 11000, equals 24 * 4 = 96 miles. Works for most almost any airspeed and groundspeed. 9 times out of 10 you will be early by about 10 or 15 miles.

Forget trying to get the fix at the altitude be early by a few miles. Especially when you get a crossing clearance below 10000 this gives you plenty of time to hit 11000 and start slowing to 250 and still make the restriction.

 

[CAVOK69]

It's closer to a 4.0 degree G/S. Used if you want to descend at idle vs. with power applied during the descent. Rate of descent varies between about 2800 and 3500.

FWIW...

if you use your altitude times 3 that will give u a 3 degree glide path, it is up to you to maintain that. i use gs divided by 2 for rate of descent. But honestly, even if you are doing 3000fpm, so what? Back in my lear 35 days( running on fumes) we would do idle throttle descents giving us an 8000fpm descent no 3 to 1... a 1.5 to 1 is what we would use. most fuel efficient type of descent is idle throttle as long as you start it at the right distance.

 

[FSB99]

some of you guys sound like you're saying 3000 fpm or descent is a bad thing.. it's a jet. flight idle, or at least very low thrust ain't gonna shock cool the motors, and it saves gas, keeps you on the required glide path etc etc.

 

[Four Strings]

2000 FPM descent. Alt to lose divide 2000 multiplied by ground speed in miles per minute.

26k to 10k. 420 knots GS

16k/2k multiplied by 7 = 56 miles. Usually add about 10 miles to that to allow for slowing to 250.

I always round to the higher even number. If I have to lose 17k of altitude I do the math in my head for 18k. 9*7=63.

300kts = 5 mpm
360 = 6 mpm
420 = 7
480 = 8
and so on

 

[h25b]

I simply use the "Force" ... But if your last name IS NOT Skywalker it might not work for you...

Now if I could just figure out a way to get my light sabre past the TSA I'll be in business...

 

[dojetdriver]

I put the little pink banana thingy in front of the fix and go back to reading the paper.

Dude, when I transitioned to the ERJ from an aircraft that had the banana/ VNAV thingy it was a shock. The ERJ doens't have one. I thought I was going to wash out of training right then and there.

 

[pianoman]

Yeah I don't understand why people hate any descent over 2000 FPM. If you look at the pressure controller, the cabin is still descending at the same rate. As long as you roll the VS down smoothly, I think that's probably the most fuel efficient and quickest way to go. If you start down way early, your TAS drops and you can back up traffic on the arrival also.

That said it's just my technique. If the FO wants to do something else and it's not a safety/ATC issue, more power to them as long as it works.

 

[DrunkIrishman]

I use the FMS. Once it says about 2000 fpm I start to descend so that the deck angle in the cabin doesn't get too steep for the pax.

If the FMS is not an option, I multiply the alt to lose by 3 and take half of the GS and then add a 0 at the end to figure out my rate.

Alt: 37,000
Cross@10,000
GS: 500 kts
Alt to lose is 27,000 x 3 = 81 nm
1/2 of GS is 250. Add a zero to the end and you get 2500 fpm.

You will have to adjust your rate of descent when your GS changes, which it will...first it will increase, then it will decrease as you get lower in the atmosphere.

BTW, this also works for glideslope reference on an ILS. Instead of chasing your ball up and down, use the VSI as a lead reference. If you are flying at a GS 140 kts, then you should have a VSI showing 700 fpm (140/2 = 70, add a 0 to the end to get 700). If your VSI showed 500 fpm, you would know to push the nose down before your ILS ball started to move down.

 

[91100 100 set]

Okay, I'll bite.

(GS*desired slope angle*1.77)=the EXACT descent rate you need. Work it anyway you like. You want to desend at 2500 fpm? Divide that descent rate by your 1.77, then divide that number by your GS (remember that your GS will likely change with the wind and TAS changing in the descent), and presto, there's the angle to plug into your FMS.

No FMS? Then use the "times 3" rule and don't get too worked up about it, you're probably not flying an airplane where getting down to a crossing restriction a bit early will cost you much extra fuel anyway.

If we can't cowboy in these airplanes, we might as well occupy ourselves somehow. This is how I occupy myself, by being a nerd with the calculator in my shirt pocket.

 

[LAXSaabdude]

I used to use the ALT to lose * 3, GS * 5 to make crossing restrictions in the EMB-120, however this can lead to descent rates of 3000 fpm or more in the ERJ.

Actually, if you are descending correctly (i.e., flight idle descents), you should be looking at about 3000 fpm on the descent. That is normal, and, despite what some people may tell you, much smoother.

I watch some guys try to maintain a 2000 fpm descent, and they keep bringing the thrust UP AND DOWN AND UP AND DOWN AND UP AND DOWN....I'm sure the poeple in the back just love it.

Bring it smoothly back to idle, roll the VS to 3000, and just leave the thrust parked at idle. Quiet, smooth, and efficient.

LAXSaabdude.

 

[LAXSaabdude]

some of you guys sound like you're saying 3000 fpm or descent is a bad thing.. it's a jet. flight idle, or at least very low thrust ain't gonna shock cool the motors, and it saves gas, keeps you on the required glide path etc etc.

Yup, 'zackly. Fly it like it's meant to be flown. You're not flying a 402 anymore.

LAXSaabdude.

 

[CitationLover]

isn't a 1.00 epr descent the "best" descent?

 

[pianoman]

What reasons would make that the "best" descent, in your opinion? Honest question- our plane has N1, no EPR. I've always heard, at least with our jets and CAL's, that a flight idle descent without boards is kind of the holy grail. Up at altitude as long as possible, going fast and sipping gas.

 

[five-alive]

if you use your altitude times 3 that will give u a 3 degree glide path, it is up to you to maintain that. i use gs divided by 2 for rate of descent. But honestly, even if you are doing 3000fpm, so what? Back in my lear 35 days( running on fumes) we would do idle throttle descents giving us an 8000fpm descent no 3 to 1... a 1.5 to 1 is what we would use. most fuel efficient type of descent is idle throttle as long as you start it at the right distance.

Thrust idle gave you 8000 fpm? Yikes, I hope that was with spoilers. Otherwise that would be an aerodynamic equivalent of a brick with bricks for wings

 

[CitationLover]

What reasons would make that the "best" descent, in your opinion? Honest question- our plane has N1, no EPR. I've always heard, at least with our jets and CAL's, that a flight idle descent without boards is kind of the holy grail. Up at altitude as long as possible, going fast and sipping gas.

look i admit i'm ignorant in regards to this, hence the question.

however, i thought a 1 epr would be the most aerodynamically clean descent (ie the thrust output would equal the drag caused by the fan blades). i dunno though.