Climb gradient?

[LearLove]

In ref to jet operations, what information do I need to figure if a departure complies with a required climb gradient?

Say my SID says "maintain 350 ft/nm to 8000 ft"

I'm looking thru my old book and can't find much info on this stuff.

Any help would be appreciated. Thanks

 

[501261]

Well, the simplest and safest way is to buy Ultranav (www.ultranav.com) for your jet and let it figure out those performance numbers.

But since you probably want to figure out how to do it the old fashioned way here’s a couple of different ways that performance problem can be run.

The safest and easiest way is to go to your second segment climb gradient chart and find a weight that allows you to maintain your required climb gradient at the top of the climb. In your example just find a weight that lets you do 5.7% on the 8000’ chart. The problem with this method is that it unnecessarily restricts your takeoff weight*.

Another method is to go to your second segment climb gradient chart and find the altitude between your top of climb and field elevation (i.e. if T/O fields at 4000’ top of SID is 8000’, so use 6000’) and find the weight at 6000’ that lets meet the climb requirement. I call this the median altitude method.

A final method is to find a weight that lets you meet the climb requirement at field elevation add that to the weight that lets you meet the climb requirement at the top of climb and divide by two (i.e. at 8000’ you can T/O at 22,500lb and get 5.7%, but at sea level you can go at 30,000lb so you use 26,250lb as your maximum take off weight). I call this the median weight method.

*Reason this is unnecessarily restricting is that for the first part of you climb you will be exceeding your required performance. Let’s say you can only be at 75%MTOW at 8000’ and meet a 5.7% (350per nm) climb gradient, but at sea level you can be at 98% of MTOW and meet a 5.7%, if you take off at sea level at 75%MTOW you will be climbing out much better than 5.7%, thus exceeding the climb requirement.

 

[avbug]

You needn't calculate second segment gradient for the top of climb, as you've gone past your second segment at that point. Calculate second segment performance for the departure elevation.

 

[501261]

Right, you’re past the second segment usually after 400’. For these jet performance numbers though it’s usually better to simply use the second segment numbers all the way through. Reason being is that you’re final segment is usually going to have a worse climb gradient than the second segment.

If you were to actually lose an engine and had to fly the SID you would simply fly the second segment profile all the way to the top of the SID requirement.

 

[avbug]

Not necessarily. Often climb gradient requirements for a departure proceedure only apply to a given fix or altitude, not necessarily to the top of the climb.

 

[Gulfstream 200]

give 15 "pro pilots" a climb gradient/SID question and after 30 mins you get 15 different answers.

buy the ultranav.

 

[THE Flying Ace]

AvBug, 501261 isn't talking about the TOC, but only the top of the SID requirment.