% climb gradient

[captain dad]

I have never dealt with this before. Does anyone have a quick way of explaining how to figure these out from feet per minute?

Thanks

 

[145BOSS]

In the refernce section in the front of your Jepessens there is a Gradient to Rate Table that can be used to figure out the minimum vertical speed of climb or descent to maintain a gradient based on your ground speed. Other than the old trick of multiplying your groundspeed by 5 to get an approximate rate of descent for a glideslope (3.0 degrees) I don't know of any other way of figuring it out.

 

[buxflyr]

Ft. per NM/6000 * 100 = %

 

[Ty Webb]

This subject has been covered extensively on this board in years past. Search in the "General" forums, or in the 91/135 forums.

If those forums don't help, try Penthouse "Forum". It probably won't address climb gradients, but will have many letters from other "readers" that will start with "You're probably not going to believe this, but . . . " and will probably contain the words "knob", "knockers" and/or "quim".


.

 

[plattsburgher]

200 ft/NM = 3.3%

 

[Lake Alice]

Make sure you understand how to compute a climb gradient, what that means and the difference between net and gross.

5-2-6. Instrument Departures states:

The FAA has combined the former standard instrument departures (SID's) and textual IFR departure procedures into a single entity called an instrument departure procedure (DP). DP's will be published in either text form, like the former IFR departure procedures, or in charted graphic form like the former SID's. Regardless of the format, all DP's provide the pilot with a way to depart the airport and transition to the en route structure safely. All DP's provide obstacle clearance and any DP may be filed for and flown. Pilots operating under 14 CFR Part 91 are strongly encouraged to file and fly a DP at night, during marginal Visual Meteorological Conditions (VMC) and Instrument Meteorological Conditions (IMC), when one is available. The following paragraphs will provide an overview of the DP program, why DP's are developed, what criteria are used, when. What criteria is used to provide obstruction clearance during departure?
1. Unless specified otherwise, required obstacle clearance for all published departures, including diverse, is based on the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing restriction. A greater climb gradient may be specified in the DP to clear obstacles or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway elevation is specified in the DP, the turn should be commenced at the higher altitude. If a turn is specified at a fix, the turn must be made at that fix. Fixes may have minimum and/or maximum crossing altitudes that must be adhered to prior to passing the fix. In rare instances, obstacles that exist on the extended runway centerline may make an "early turn" more desirable than proceeding straight ahead. In these cases, the published departure instructions will include the language "turn left(right) as soon as practicable." These departures will also include a ceiling and visibility minimum of at least 400 and 1. Pilots encountering one of these DP's should preplan the climb out to gain altitude and begin the turn as quickly as possible within the bounds of safe operating practices and operating limitations.

Therefore a standard instrument departure requires a 200 feet per nautical mile climb equaling a 3.3 percent climb gradient.
(200 fpnm/ 6028 nautical mile = 3.3%)
The 200 fpnm breaks down to 152 fpm slope and 48’ obstacle clearence required by TERPS

Sec. 25.115 states:

(a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the takeoff distance determined in accordance with Sec. 25.113(a) or (b), as appropriate for the runway surface condition.]
(b) The net takeoff flight path data must be determined so that they represent the actual takeoff flight paths (determined in accordance with Sec. 25.111 and with paragraph (a) of this section) reduced at each point by a gradient of climb equal to--
(1) 0.8 percent for two-engine airplanes;

Note: Therefore a 0.8 percent reduction for a two engine airplane – 2.4 % for a two engine airplane(25.121b) = 1.6% net climb gradient for a two engine airplane.

 

[Whine Lover]

Gradient schmadient.

Take off and FLY.

That calculation crap is for needle dicks, ex-military, and ERAU grads.

I know...I am in the process of recovering from several of the above character defects.


YKW

 

[Lake Alice]

Its realy only an issue for 135 operators. I haven't seen it come up in 121 since we have dispatchers. But you are correct about the Riddlites!

 

[FLYLOW22]

Its realy only an issue for 135 operators. I haven't seen it come up in 121 since we have dispatchers. But you are correct about the Riddlites!

121 = Dispatch deptartment takes care of it all.
91 = You take care of it all using the AFM.
91K/135 = Depends on the ability of the dispatch department.

 

[JAM-BRO]

It's based on groundspeed. If you are climbing at 120kts and your climb gradient reqs a min of, for example, 230ft/nm, you need a min 460ft/min climb.... At 120kts gs you are going 2 miles/min over the ground. 2x230=460. If your speed is 150kts then you multiply by 2.5, 90kts=1.5,180kts=3, and so on...

Hope that helps...

 

[hyflyt560]

NM/6076 x 100 = % (6076.115 feet in a nautical mile)

 

[Beanie]

...learn more here:


http://cavucompanies.com/CAVU/discuss.htm#Climb gradients, a primer

and here:

http://forums.flightinfo.com/printthread.php?t=57299&pp=15
http://forums.flightinfo.com/printthread.php?=57299&pp=15
Lead sled will guide you through it.

 

[TheBaron]

NM/6076 x 100 = % (6076.115 feet in a nautical mile)

Thank you. Somebody finally got it right. Even if it is nitpicking, and I assume you meant Feet Per Nautical Mile/6076.1 x 100 = % instead of NM. D@mn, there I go nitpicking!

 

[metrodriver]

a lot of SID plates give a column with the fpm requirement at different airspeeds

 

[Beanie]

The original poster knows that the conversions are on the SIDs. He is asking about converting to a percentage of climb gradient and back again for the climb gradients in the AFM of his aircraft.

Example: The standard is 200 ft per naut. mile. To convert this to a percentage, you would have to take the 200 and divide by 6076.

200/6076 *100 = 3.3% climb gradient.

I would bet he does not have APG data (runway analysis for each runway) that we have with a 121 carrier. He is having to figure his engine out climb gradients so he can comply with his AFM and the FAA regarding Part 25 certification of his airlplane. The AFM is going to have the data presented in a percentage of climb gradient for each segment up to 1500 feet agl. Taking his groundspeed and multiplying it by the SID requirement in FPM only tells him if he can comply with the SID with all engines running, which is what SIDs are based on, not if he meets the Part 25 certification. If you have any questions, look at the links I put in my previous post. It should clear things up.