Converting feet/NM to FPM

[arb65912]

Gentlemen, I know that for some it will be a trivial question but I am having problem with it.
On IAP charts I see many times that aircraft has to have climb rate for example 305 ' per NM.
How do I convert it to FPM?

See IAP at San Carlos http://tiles.skyvector.com/sky/files/tp ... 19RZ30.PDF

Another question on a side, I checked preferred routes between some airports in ZOA area, there are not as many city pairs for TEC routes as in ZLA, is ZLA some kind of high priority versus ZOA?

Thank you. Cheers, Andrzej

[Orest Skrypuch]

Dead simple.

Let us say that your planned climbout speed is 90 knts. Here is the rule, for that speed you use a multiplier of 90/60 = 1.5. If you are curious, the units of that multiplier are nm/min, which explains the "trick".

Then take the required climbout rate of 305 ft/nm, and multiply: 305 ft/nm x 1.5 nm/min = 458 fpm

So, 458 is the required climbout in fpm.

If your climbout speed is a little different, than you just use a different calculated multiplier. BTW, if the winds are brisk or you are at high altitude, be sure to use your expected GS on climbout, not indicated airspeed.

* Orest

[arb65912]

Hi Orest,

Thank you very much.

All makes sense now, the higher my climbout speed, the higher my rate of ascend has to be to cover 305' over 1NM.

When I apply the numbers to Piper Cherokee 140 and 302' per 1NM climb:

Normal climbout speed 90 KT, I get 453 FPM

Best rate of Climb Vy 75KT, I get 377.5 FPM

Best Angle of Climb Vx 66 KT , I get 332.2 FPM

That tells me that I am good for San Carlos missed approach.

But, these numbers are calculated for IAS .... hmmmm, how do I know what my ground speed will be ?

Thank you again.

Cheers, Andrzej

[Orest Skrypuch]

Most of the time you will be taking off into a headwind, easy to make a reasonable estimation for a short climbout more or less on the runway line.

But it can get tricky if the departure has a quick turn after departure, then you have to make an allowance for the change in wind vector. Also remember that as you climb, the wind will usually veer and increase in speed. For long climbouts on the departure procedure, there can be a big change in wind once you exit the "boundary" layer, typically at 3000 AGL or so. Skew-T diagrams can help in the RW, but I doubt that FS will accurately model those wind changes predictably.

In any case, no way to take all of these precisely into account, just be conservative in your figuring and you should be fine. I would allow for at least a 50% margin in climb to be safe.

* Orest

[arb65912]

Thank you, Orest. I have a quite good idea now how to approach the subject. Cheers, Andrzej

[Brandon Grchan]

Another question on a side, I checked preferred routes between some airports in ZOA area, there are not as many city pairs for TEC routes as in ZLA, is ZLA some kind of high priority versus ZOA?

Thank you. Cheers, Andrzej

ZOA does not use a TEC route system like ZLA does. We do have some prefered routings in the ZOA/norcal area , but its not something that is published like the TEC routes.

[arb65912]

Thank you , Brandon.

I am still confused ... sorry.

Is the link for for NFDC Preferred Routes Database working in all US? I assume, yes.

When flying in ZOA area. should I still check for preferred routed ( there will not be many, I already know that) and then if there is no one, continue with my own route planning?

Sorry for dragging that subject but I want to understand and do things properly.

Cheers, AJ