Angle of climb vs rate of climb

[Guest Marius Grobler]

Hi there fellow aviators and friends

 

Assume an aircraft taking off in a headwind of k knots from runway XX. At the end of the runway there is a tall obstacle that the pilot has to clear.

 

He consults his tech manual and notices that his best angle of climb is 66 knots and the best rate of climb is 68 knots.

 

Which one woulod he follow and why?

 

 

[Guest tezza]

Best angle of climb is just that, the best or steepest climb angle you can safely obtain. If you have to clear obstacles that is what you use. Best rate of climb is simply the speed that gives you the fastest climb rate ie max ft/min climb, but the climb angle will be lower so there is less clearance of any obstacles.

 

Terry

 

 

[Guest Marius Grobler]

Indeed...except that I do not agree:

 

The best rate of climb, in mathematical terms, is the change in height divided by the change in time. If time were on the x-axis and height on the y-axis then, at the best rate of climb, the climb angle would be at its greatest. If the climb angle is steeper for rate of climb than angle of climb then it would mean that the best climb angle is, in fact, the best climb rate.

 

 

[Guest High Plains Drifter]

Marius Grobler, I see your from flat country Chinchilla - Id probably just borrow a farmers bull dozer and remove the tall obstacle from the end of the strip :thumb_up:

 

 

[Guest Marius Grobler]

 

Scar trees...whot. I dare not respond to that just in case the councillors are keeping tabs...

 

 

[Guest Marius Grobler]

Found this on Wiki

 

http://en.wikipedia.org/wiki/Rate_of_climb

 

I have to say, however, that for RA this is a large gray area because take-off is at full thrust.

 

Also refer to http://www.airliners.net/aviation-forums/tech_ops/read.main/111213/

 

 

[Guest tezza]

Indeed...except that I do not agree:The best rate of climb, in mathematical terms, is the change in height divided by the change in time. If time were on the x-axis and height on the y-axis then, at the best rate of climb, the climb angle would be at its greatest. If the climb angle is steeper for rate of climb than angle of climb then it would mean that the best climb angle is, in fact, the best climb rate.

No we are talking about 2 different angles. best rate of climb Vy is the steepest angle on a plot of ht vs time. but the best angle of climb Vx ( ie best obstacle clearance) is the steepest angle on a plot of ht vs horizontal distance travelled. Best angle of climb will always be achieved at a slower speed than best rate of climb, in fact the best climb angle will be achieved at the slowest safe speed, where excess thrust is a maximum. For most light aircraft Vx is about 10 kts less than Vy.

 

 

[Guest Baphomet]

The best angle of climb will give us a nominated height in the least DISTANCE from take-of point (what we need to avoid an obstacle). Best rate of climb will get us there sooner but further away from the take-off point (you hit the obstacle)

 

 

[Guest High Plains Drifter]

Assume an aircraft taking off in a headwind of k knots from runway XX. At the end of the runway there is a tall obstacle that the pilot has to clear

Marius Grobler, in this scenario, is there any turbulence to consider from the wind/obstacle interplay ?

 

 

[Guest Marius Grobler]

Okay. That figures. I can see that there is a semantic difference (is that a proper English term?). I can also appreciate that, for GA aircraft, the difference could be more than semantic.

 

 

[Guest Marius Grobler]

No, that was not the intent. All other things being equal...so to speak

 

 

[Mazda]

If obstacle clearance is an issue, consider a short field take off, climbing out at best angle until obstacle clearance is assured, then lower the nose to best rate.

 

 

[Yenn]

Keep away from those anti semanticists, they are politically incorrect, but most of the remarks are correct.

 

 

[Guest Marius Grobler]

 

As you say...the Borg is upon us!

 

 

[jacmiles]

Marius,What you need is a great big saw blade attached to your undercarage and if stuff up your angle of climb you will knock off the top of whatever is in your way.Therefore every time you take off it can only get easier:big_grin:

 

 

[ab0767]

I had a hard time grasping this same question during my training and to my instructors credit he took just as much time expalaining it. The best angle of climb is an angle 20 degress or 30 degress whatever. the best rate of climb is FPM. Your plane might climb at 30 degrees to cover an obstacle and will gain x amount of feet, less than it would have done in the same amount of time over a longer DISTANCE as the ASI is higher with a lower nose attitude and hence more lift . If you were to use best rate of climb you may not clear that obstacle as the distance is longer. Once you have cleared the obstacle go back to the best rate of climb.

 

 

[Guest Marius Grobler]

While you were awaiting a reply I have patented the "Take-off saw" and my U.S. lawyer has started proceedings against you for stealing my idea!

 

 

[Guest Marius Grobler]

Yes. It has taken me a while but I get it. There is quite a difference although I suspect that (at least in some AC) the difference would be indiscernable.

 

 

[IanR]

Yes. It has taken me a while but I get it. There is quite a difference although I suspect that (at least in some AC) the difference would be indiscernable.

That may be the case - but don't make assumptions - read the manual for each aircraft !