How to dertermine climb gradient

[mas618 17]

Hi fellow simmers!1st sorry for the spelling in the headline ;(So I've been flying in and out of Innsbruck and Salzburg these days. Both airports have requirements regarding climb gradients on departure and on missed approach procedures.My problems is, that I have not been able to figure out how and can calculate if I meet those requirements, based on weight, thrust, weather and so on?Looking through FCOM 1 I can only find climb gradients for Go-around with one engine INOP at flaps 15. That takes care of the whole Go-around issue.1. Regarding TO climb gradient, I've been unable to find any table? Have I missed something? (using the GA table would be incorrect, as the climb gradient is higher with flaps 15 rather than flaps 5 - correct?)2. Is it correct, that only JAR ops (based on KGS and Meters) exist for the 736?3. Using the obstacle clearence chart is not really possible, because it is limited to obstacles of 300 meters high... Correct?Any help appriciated!Mas

[janpitor 2]

Hi, the gradient is higher for flaps 5 than for flaps 15, because you have less drag, so theoretically you may use the table.

[mas618 17]

Hi, the gradient is higher for flaps 5 than for flaps 15, because you have less drag, so theoretically you may use the table.

Ahh - I see. I'll use the table for now then. But surely a table for climbgardients at various TOW and thrust configs must exist?Thx for the tip Ján!Mas

[mas618 17]

Ahh - I see. I'll use the table for now then. But surely a table for climbgardients at various TOW and thrust configs must exist?Thx for the tip Ján!Mas

I'm gonna quote my self here, because that was really nonesence what I just wrote. Using the GA tables are off course not ok for TO, because at GA point the A/C would all ready be in speed and the distance to a given object would be far greater than that from the "brake release point", which is what I'm interested in speaking of climb gradient on take off...I'm really twisting my head on this one. The climb gradient on any departure must be calculated everytime there is a requirement for this in the SID - someone must know this? TOPCAT does not contain the climb gradient requirements for LOWI departure, and I cannot insert i manually, because it exceeds TOPCAT definition limits for an obstacle (!?) -What do you guys do when flying a SID with a climb gradient requirement? HOPE that you'll make it? That's usually a bad idea ;);Mas

[El padrino 2]

This might help a bithttp://www.flightsimaviation.com/rule-of-thumb/1_Convert_Climb_Gradient_to_Climb_Rate_RoC.html

[JRBarrett 3,078]

I'm gonna quote my self here' date=' because that was really nonesence what I just wrote. Using the GA tables are off course not ok for TO, because at GA point the A/C would all ready be in speed and the distance to a given object would be far greater than that from the "brake release point", which is what I'm interested in speaking of climb gradient on take off...I'm really twisting my head on this one. The climb gradient on any departure must be calculated everytime there is a requirement for this in the SID - someone must know this? TOPCAT does not contain the climb gradient requirements for LOWI departure, and I cannot insert i manually, because it exceeds TOPCAT definition limits for an obstacle (!?) -What do you guys do when flying a SID with a climb gradient requirement? HOPE that you'll make it? That's usually a bad idea ;);Mas[/quote']If required climb gradient is given in feet per nautical mile (which is typical), do the following:Call the required feet per nautical mile F The formula is F divided by 6076 multiplied by 100If, for example, the required climb gradient is 750 feet per nautical mile you would have 750 / 6076 x 100, which equals 12.34That answer, 12.34, is your climb gradient in percent. To convert that to feet per minute on the VSI gauge, simply multiply the percentage by your ground speed. Unless you have a major head or tail wind on climb out, just use your climb airspeed, so if you are climbing out at 165 knots, the final answer would be 12.34 x 165, which equals 1974 feet per minute climb rate.The faster your airspeed, the higher vertical speed you'll need to meet the specified climb gradient.

[mas618 17]

This might help a bithttp://www.flightsim...b_Rate_RoC.html

Thx for that George - guess it's the same calculations that Jim expains.

If required climb gradient is given in feet per nautical mile (which is typical), do the following:Call the required feet per nautical mile F The formula is F divided by 6076 multiplied by 100If, for example, the required climb gradient is 750 feet per nautical mile you would have 750 / 6076 x 100, which equals 12.34That answer, 12.34, is your climb gradient in percent. To convert that to feet per minute on the VSI gauge, simply multiply the percentage by your ground speed. Unless you have a major head or tail wind on climb out, just use your climb airspeed, so if you are climbing out at 165 knots, the final answer would be 12.34 x 165, which equals 1974 feet per minute climb rate.The faster your airspeed, the higher vertical speed you'll need to meet the specified climb gradient.

In LOWI the cl requirements are given in obstacle altitude (FT) and distance to that in Meters? What I'm ultimately unsure of, is how can I determine, if I can actually perform that rate of climb? Be it feet/min og gradient i percent?I'm thinking that a table for one engine climb gradient must exist? In LOWI for ex. there is no Enginge Out procedure for the SID, so before a legal take off, I must be shure that I can can meet the required climb gradient even with one engine. I suspect that all this i taken care of by the dispatcher, but since I lack a such, I wanna make sure my self ;)But thanks for your answers - I'm not sure how the formula would go when we're talking meters and feet though?Mas

[scandinavian13 5,192]

In the real world, dispatchers can use their software to run the calcs. TOPCAT will also be able to run those calcs. Ever wonder why it says LIMIT: FIELD or LIMIT: CLIMB?). The limits should already be in there (limits being the climb gradients), but if they're not, you can add in obstacles on the EDIT AIRPORT option. There, just add in an obstacle close in to the runway that's right on the required climb gradient (e.g: Req. Gradient of 300'/nm, create an object 1nm from the threshold of the runway, 300' above the runway elevation).I'm sure there's a way to run it through the FMC, too. I don't know it, but I bet there's a way to check there, too.

[michal 44]

I'm thinking that a table for one engine climb gradient must exist?

Actually if you take typical takeoff performance tables which are custom prepared for a specific air carrier for a given airport/runway they automatically take care of this problem. In other words the combination of temperatures, weights and V1/VR/V2 do take into consideration immediate obstacles, required climb gradients and the fact that you may lose an engine.

[mas618 17]

In the real world, dispatchers can use their software to run the calcs. TOPCAT will also be able to run those calcs. Ever wonder why it says LIMIT: FIELD or LIMIT: CLIMB?). The limits should already be in there (limits being the climb gradients), but if they're not, you can add in obstacles on the EDIT AIRPORT option. There, just add in an obstacle close in to the runway that's right on the required climb gradient (e.g: Req. Gradient of 300'/nm, create an object 1nm from the threshold of the runway, 300' above the runway elevation).I'm sure there's a way to run it through the FMC, too. I don't know it, but I bet there's a way to check there, too.

Ok - maybe I'm missing something in TOPCAT.Here's the SID 26 chart for LOWI: http://charts.vacc-austria.org/LOWI/LOWI_Departure_SID%2026_01072011.pdfIn the Take Off section of TOPCAT with LOWI selected, I go to the EDITOR tab, and select Add in obstacles. Here I type 2100 meters for beginning of TakeOff run and then (4430-1907) = 2523 ft in Height above Runway. That gives an error saying "obstacle angle exceeds 10%" Aditionally, there's no obstacles in LOWI database, so I'm confused as what the limit code CLIMB is based on - is it simply the fact that the charts requires 3,3% climb gradient and that TOPCAT knows this?I gather by now that this should probably be directed at the TOPCAT forum, so I think I'll do that ;)But thanks for your help anyway!MAs

[scandinavian13 5,192]

Make sure you're entering the proper distance from the runway. If you don't, it's assuming there's a 2523' obstacle right where the runway ends, and that's illegal in most countries.

[japascoe 98]

I'm sure there's a way to run it through the FMC, too. I don't know it, but I bet there's a way to check there, too.

I'm guessing if you added in a custom waypoint with an altitude restriction VNAV would complain if the climb path was unachievable?

[3-2-1-Now 126]

Minimum Climb Rate:(ft / nm) * GS in kts * 101.266 (call it 102 to be safe).750 ft/nm gradient at 150 kts ground speed requires:(750/6076) * 150 * 102 = 1888 ft/min.If the gradient is given in percent:Assume the gradient required is 5.2% and we have a GS of 150 kts:150 * 102 * (5.2/100) = 795.6 ft/min.Note that SPEED IN KTS * 102 = SPEED IN FEET PER MINUTE.That is derived from:((kts / 60) * 6076)= (kts / 60) * (6076 / 1)= (kts * 6076) / (60 * 1)= 6076 / 60 = 101.2666...therefore: nm/h * 102 ~ ft/min. Saves the mental gymnastics when busy. :)Regarding whether you can make the performance - you need tables. No tables, no fly. Performance includes critical engine inoperative.Best regards,Robin.

[michal 44]

.....GS in kts * 101.266 (call it 102 to be safe).750 ft/nm gradient at 150 kts ground speed requires:(750/6076) * 150 * 102 = 1888 ft/min.

Even this is unnecessarily complicated, AOPA teaches GA pilots this formula:divide by 60 and multiply by ground speed.750/60 ~= between 12 and 13 (12.5 for someone who is sharp)(12.5)*150 = 1875 and it is close enough, many pilots can perform such arithmetic even with no calculator around.

[mas618 17]

Make sure you're entering the proper distance from the runway. If you don't, it's assuming there's a 2523' obstacle right where the runway ends, and that's illegal in most countries.

hehe - I entered the distance to be 2100 m as per the chart. But you make a fair assumption - that would probably be illegal in most countries... lol....