Climb gradients and noise abatement procedures

[VHOJT 165]

Hi allI have a couple of queries that I would like to pose to anyone with any knowledge on the matter and with any time to answer:1) When following a SID, and I am told to keep a minimum 5.5% gradient - without the table as in the chart on this link, is there any way of telling? Is this what is known as RNAV?http://www.caas.gov.sg/caasWeb/export/site...S-AD2-73_74.pdf2) On the departure VJR8B from RWY 20C as in the chart I linked to: How likely is it that a 744 at MTOW will make the initial 2000 ft or above restriction at SUDPO straight after take-off? I have read of several different climb/noise abatement climb techniques. The ones I know/understand are (feel free to correct me):- ICAO 1 - T/O thrust to 1500ft, then climb thrust, flap retraction and acceleration (seems to be what Captain Alan Carter used in 2000)- ICAO 2 - T/O thrust to 1500ft, then climb thrust, at 3000ft, flap retractin and acceleration- NADP1/NADP2 which are quite similar, bar thrust reduction at 800ft AAE.- Strange British Airways one for flaps 20 takeoff (also used in the year 2000, don't know about now) - T/O power to 1000ft, then climb power, then accelerate to Flap 10 retraction speed, set flaps 10, then continue to climb to 4000ft, then clean up and accelerate.To any pilots or anyone who knows - what procedures do you use? I remember reading somewhere ICAO2 is reasonably common noise abatement procedure? Is the technique you use dictated by the SID/circumstances/airline SOP/airport SOP?I realise these are pretty specific questions that maybe not many here would know (like myself!) - hopefully someone may be able to shed some light on this?Thanks for any help, regards;Rudy

[downscc 1,327]

Required rate of climb for a given gradient or slope is pretty easy using roundoff and approximation. A nm is about 6000 ft (6072), 5.5% roundup to 6% is about 360 ft; so your target slope is at least 360 ft/nm. If your groundspeed is about 240 kt that is equivalent to 4 nm/min (240/60); therefore, your desired rate of climb is 4x360= 1440 ft/min which is easily achieved under normal conditions. If your groundspeed is less then the required rate of climb is less but don't bother calculating it since you can easily achieve the higher requirement.I've noticed that all SIDs that I have seen have minimum climb slopes well below the normal operating ability of turbojet aircraft. It's safe to do a quick mental calc of the required climb slope then pay attention to the thrust reduction and flap schedule recommended for your type aircraft. I'm not B744 experienced, so I'll defer commend on operating practices to those that are better qualified.

[victorlima01 2]

Dan is right. However, I have a pretty easier way to do this. I just pick up my Jeppesen manual flight computer (the thing no one ever uses anymore) and ifnd that out in less than 10 seconds. This is about the only reason why I still have that thing, I only bought it because here in Brazil some of the our private pilot written exam navigation questions require that we use it for wind and TAS calculations. (I do carry it when I'm flying for real however... you never know...)Best Regards,Victor LimaSBGLhttp://www.precisionmanuals.com/images/forum/800driver.jpg

[VHOJT 165]

THanks for the replies Victor and Dan. That clears up the climb gradient question. I thought it would be something like that! Thanks a lot for your help with that!Hopefully there may be someone else knowing about the second question, as bizzare as it is!RegardsRudy

[Sylle 48]

A quicker way to calculate the V/S you need in order to meet the requested climb gradient is the following rule of thumb:groundspeed (kts) x climb gradient (%) = required V/S (ft/min)Let's take the same example as the one above:GS = 240ktsclimb gradient = 5.5% ~ 6%240 x 6 = 1440ft/minA lot easier isn't it?? :(Regarding the noise abatment procedures, in our company we choose one of the four procedures as described below:- if a specific noise abatment procedure is specified on the charts, that's the one we will use.- if no procedure is specified in the charts, we use ICAO 2.Best regards,Sylvain

[cowpatz 243]

I use the same method as Sylvain to work out the required rate of climb for departures. It is a little acaedemic as these are average rates of climb and it is a little impractical to stare at the VSI to try and figure it all out. Pans ops requirementsWe use a rule that a 3.3% gradient can be acchieved if 2000ft QFE can be reached by 10 miles. This is called a net gradient and normally a net to gross allowance is added (3.2 %) to get a gross gradient of 6.5%. This gradient can be difficult to acchieve with normal accel/ flap retraction schedules especially in an eng failure case and is why we used the 2000 by 10 rule. If this gradient is too steep for a given airfield then company performance engineers will work out an eng failure procedure to follow. We use a standard procedure practically where ever we go and that is TO thrust to 1500ft AGL and then climb thrust followed by flap retraction on schedule. There may be occasions where the flap retraction is higher due to terrain.CheersSteve

[VHOJT 165]

Sorry for the delayed reply - thanks for the replies Sylvain and Steve!Steve - if you have a few pretty close "at or above" constraints ahead, do you remain in VNAV during flap retraction or do you use V/S mode to keep you climbing slightly faster and accelerating slightly more slowly?Thanks again for all your help!CheersRudy

[cowpatz 243]

I remain in VNAV. Any obstacle issues would have been looked at by our performance engineers and an alternate procedure promulgated in the event of an eng failure.CheersSteve