climb gradient vs flight path angle
Thank you ater
I would add RoC in the airmass, which normally is moving WRT to the ground.
If you have a headwind on takeoff of extreme velocity, you have a greatly reduced takeoff roll and using basic climb schedule can easily have a "true" climb angle very high. Not pitch attitude, not AoA plus pitch, but a velocity vector referenced to Mother Earth. Hell, if the headwind was strong enough you could have 30, 40 or 50 degrees of actual climb compared to the runway.
The "gradient" WRT to the ground was what I was always concerned about. How many feet to get above the ground for available runway and obstacles at the other end. On one mission at heavy weight, I had the wind shift halfway down the rwy and simply stopped getting more CAS. Too fast to abort, and skimmed over the palm trees on the edge of the max AoA once up, barely. So I know what the "gradient" is. On that ride we had about 80% of available runway "computed" for takeoff considering our weight and the "predicted" wind down the runway. Then two check speeds at various rwy markers. Not something a commercial jet would go with, but it was a wartime scenario, O.K.?
Ground speed is what determines climb gradient; i.e. "This departure requires a climb gradient of 425 feet per mile. Those miles are ground miles, not air miles.
If you have a headwind on takeoff of extreme velocity, you have a greatly reduced takeoff roll and using basic climb schedule can easily have a "true" climb angle very high. Not pitch attitude, not AoA plus pitch, but a velocity vector referenced to Mother Earth. Hell, if the headwind was strong enough you could have 30, 40 or 50 degrees of actual climb compared to the runway.
The "gradient" WRT to the ground was what I was always concerned about. How many feet to get above the ground for available runway and obstacles at the other end. On one mission at heavy weight, I had the wind shift halfway down the rwy and simply stopped getting more CAS. Too fast to abort, and skimmed over the palm trees on the edge of the max AoA once up, barely. So I know what the "gradient" is. On that ride we had about 80% of available runway "computed" for takeoff considering our weight and the "predicted" wind down the runway. Then two check speeds at various rwy markers. Not something a commercial jet would go with, but it was a wartime scenario, O.K.?
Join Date: Dec 2007
Location: Pasadena
Posts: 633
Likes: 0
Received 0 Likes
on
0 Posts
Gums and aterpster have good points:
Whether and how you fly depends on your airspeed, but where the mountains and palm trees are depends on your ground speed.
Whether you have the right terminology is perhaps less important than whether you are confident that you're going to keep flying and avoid them based on using the right measures for the right problem.
Whether and how you fly depends on your airspeed, but where the mountains and palm trees are depends on your ground speed.
Whether you have the right terminology is perhaps less important than whether you are confident that you're going to keep flying and avoid them based on using the right measures for the right problem.
Thread Starter
Join Date: Apr 2008
Location: UK
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Thank you all for great feedback,
The situation and questions arise from a lesson in performance.
Talking about the different required gradient for certification for the 4 stages.
For this I assume still wind,
As for day to day operation and obstacle clearance it is evident that wind does affect our flight path and Is taken into consideration...
I initially reacted to a simple statement ..
Headwind increases your climb gradient
Well yes if speaking about obstacle clearance.. (ground referenced gradient)but NOT when considering your climb gradient of whatever depending on number of engines
I still maintain that without specifying what the gradient gradient is referenced to. The aforementioned statement is incorrect..
What I have learned sofar, is. Perspectives from either side of the pond as well between mil & civil pilots differ..
We all achieve the same outcome , but our verbiage to describe what we are doing seems to be different.. perhaps it is a context issue too..
I am adamant to get to the bottom of this simple conundrum, so please continue to give feedback
The situation and questions arise from a lesson in performance.
Talking about the different required gradient for certification for the 4 stages.
For this I assume still wind,
As for day to day operation and obstacle clearance it is evident that wind does affect our flight path and Is taken into consideration...
I initially reacted to a simple statement ..
Headwind increases your climb gradient
Well yes if speaking about obstacle clearance.. (ground referenced gradient)but NOT when considering your climb gradient of whatever depending on number of engines
I still maintain that without specifying what the gradient gradient is referenced to. The aforementioned statement is incorrect..
What I have learned sofar, is. Perspectives from either side of the pond as well between mil & civil pilots differ..
We all achieve the same outcome , but our verbiage to describe what we are doing seems to be different.. perhaps it is a context issue too..
I am adamant to get to the bottom of this simple conundrum, so please continue to give feedback
Thread Starter
Join Date: Apr 2008
Location: UK
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Flyer 101,
Are you sure ??
Roc is fpm, and you don't get to fl 100 any faster in a headwind..
Time to climb is also unaffected right ?
You are though correct that you will get to your level over a shorter Ground Distance.
Are you sure ??
Roc is fpm, and you don't get to fl 100 any faster in a headwind..
Time to climb is also unaffected right ?
You are though correct that you will get to your level over a shorter Ground Distance.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
From the FAA's AIM:
3. Pilots must preplan to determine if the aircraft can meet the climb gradient (expressed in feet per nautical mile) required by the departure procedure, and be aware that flying at a higher than anticipated ground speed increases the climb rate requirement in feet per minute. Higher than standard climb gradients are specified by a note on the departure procedure chart for graphic DPs, or in the Take-Off Minimums and (Obstacle) Departure Procedures section of the U.S. Terminal Procedures booklet for textual ODPs. The required climb gradient, or higher, must be maintained to the specified altitude or fix, then the standard climb gradient of 200 ft/NM can be resumed. A table for the conversion of climb gradient (feet per nautical mile) to climb rate (feet per minute), at a given ground speed, is included on the inside of the back cover of the U.S. Terminal Procedures booklets.
Join Date: Sep 1998
Location: wherever
Age: 55
Posts: 1,616
Likes: 0
Received 0 Likes
on
0 Posts
HYGHFLY33
You are overcomplicating things.
The gradient required, whether it be climb or obstacle related doesn't change with wind.
It's just geometry in the case of obstacles and rules in a book for segmented take off flight path.
The gradient you will achieve when flying at a fixed IAS will vary with head or tail wind.
Therefore we calculate the gradient we can achieve in the actual wind (not really) conditions and confirm it is greater than that required.
You are overcomplicating things.
The gradient required, whether it be climb or obstacle related doesn't change with wind.
It's just geometry in the case of obstacles and rules in a book for segmented take off flight path.
The gradient you will achieve when flying at a fixed IAS will vary with head or tail wind.
Therefore we calculate the gradient we can achieve in the actual wind (not really) conditions and confirm it is greater than that required.
Thank you, Hoppy and Ater.
Sheesh.
There must be fifty ways to define gradient ( cheap reference to Paul Simon's song).
The big thing is not to contact Mother Earth. THAT is where the "gradient" comes into play.
RoC is normally a constant for power, gross weight and AoA and such. That's in the air mass. Over Mother Earth, it's a different story.
You are making this more complicated than the original question, Highfly.
If the chart says you must achieve "x" feet, "x" miles from the runway, then I would look at my plane's performance and the appropriate charts for my plane.
This thread is getting old, and I am not sure we are satisfying the questions that Highfly started with. Many of us here have thousands of hours, and I flew many right at the limits of the aircraft performance. If one can not trust us to provide an decent answer, then who else can?
Sheesh.
There must be fifty ways to define gradient ( cheap reference to Paul Simon's song).
The big thing is not to contact Mother Earth. THAT is where the "gradient" comes into play.
RoC is normally a constant for power, gross weight and AoA and such. That's in the air mass. Over Mother Earth, it's a different story.
You are making this more complicated than the original question, Highfly.
If the chart says you must achieve "x" feet, "x" miles from the runway, then I would look at my plane's performance and the appropriate charts for my plane.
This thread is getting old, and I am not sure we are satisfying the questions that Highfly started with. Many of us here have thousands of hours, and I flew many right at the limits of the aircraft performance. If one can not trust us to provide an decent answer, then who else can?
Join Date: Sep 2013
Location: usa
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
Re question #27: I wasn't trying to say you always climb faster in a headwind. I was talking about a wind gradient. (Yet another use of the the term "gradient"!)
I agree that I'm adding another "twist" that wasn't stated in the original question, but a headwind gradient (increasing headwind with altitude) absolutely does boost the climb rate. So does a reverse tailwind gradient (decreasing tailwind with altitude) but this is much less common. We climb through some amount of headwind gradient on nearly every takeoff.
The same headwind gradient that helps the climb rate, also increases our sink rate as we descend down through it. This is a very real effect that demands some extra airspeed for a safe landing approach when the gradient is strong. So that we have enough energy to flare, ie. arrest the high sink rate.
Descending through a tailwind gradient, on the other hand, will reduce the sink rate. This can add to your woes if you are accidentally landing downwind, in which case there are two different factors tending to carry you far down the runway-- higher groundspeed than you may be used to, and also a lower sink rate.
These effects are real enough to be easily detectable in light plane flying. Near the ground is where the largest gradients usually exist. Are there real-world cases where you could measure a significant change in climb rate due to these effects when testing over intervals of 1000 feet or more, starting at least that high over the ground? I'm not sure...
I agree that I'm adding another "twist" that wasn't stated in the original question, but a headwind gradient (increasing headwind with altitude) absolutely does boost the climb rate. So does a reverse tailwind gradient (decreasing tailwind with altitude) but this is much less common. We climb through some amount of headwind gradient on nearly every takeoff.
The same headwind gradient that helps the climb rate, also increases our sink rate as we descend down through it. This is a very real effect that demands some extra airspeed for a safe landing approach when the gradient is strong. So that we have enough energy to flare, ie. arrest the high sink rate.
Descending through a tailwind gradient, on the other hand, will reduce the sink rate. This can add to your woes if you are accidentally landing downwind, in which case there are two different factors tending to carry you far down the runway-- higher groundspeed than you may be used to, and also a lower sink rate.
These effects are real enough to be easily detectable in light plane flying. Near the ground is where the largest gradients usually exist. Are there real-world cases where you could measure a significant change in climb rate due to these effects when testing over intervals of 1000 feet or more, starting at least that high over the ground? I'm not sure...
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
flyer:
Wind gradient? How about wind component?
Here is what my PC's Webster dictionary has to say about the word gradient:
gradient
gra·di·ent [grįydee ?nt] noun (plural gra·di·ents)
1.slope: an upward or downward slope, for example, in a road or railroad
2.steepness: the rate at which the steepness of a slope increases
3.PHYSICS measure of change: a measure of change in a physical quantity such as temperature or pressure over a specified distance
4.BIOLOGY rate of growth: any of a series of changes in the rate of growth or metabolism of an organism, cell, or organ
5.MATHEMATICS slope on a curve: the slope of a line or a tangent at any point on a curve
adjective
sloping: sloping evenly and uniformly
Encarta® World English Dictionary © & (P) 1999,2000 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.
I agree that I'm adding another "twist" that wasn't stated in the original question, but a headwind gradient (increasing headwind with altitude) absolutely does boost the climb rate. So does a reverse tailwind gradient (decreasing tailwind with altitude) but this is much less common. We climb through some amount of headwind gradient on nearly every takeoff.
Here is what my PC's Webster dictionary has to say about the word gradient:
gradient
gra·di·ent [grįydee ?nt] noun (plural gra·di·ents)
1.slope: an upward or downward slope, for example, in a road or railroad
2.steepness: the rate at which the steepness of a slope increases
3.PHYSICS measure of change: a measure of change in a physical quantity such as temperature or pressure over a specified distance
4.BIOLOGY rate of growth: any of a series of changes in the rate of growth or metabolism of an organism, cell, or organ
5.MATHEMATICS slope on a curve: the slope of a line or a tangent at any point on a curve
adjective
sloping: sloping evenly and uniformly
Encarta® World English Dictionary © & (P) 1999,2000 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
FE Hoppy:
Only in terms of rapid velocity changes in climb or descent in a jet. 
In my performance experience related to departure procedures it simply means feet per mile (nautical ground mile).
Wind gradient is a very common term. I'm surprised a terpster isn't familiar with it.
In my performance experience related to departure procedures it simply means feet per mile (nautical ground mile).
Join Date: Sep 2013
Location: usa
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
Wind component means something different than wind gradient. Ask the albatross.
Every pilot should understand the effects of a wind gradient.
Surely we can do better in "the very best in technical discussion" than looking things up in various non-aviation dictionaries?
PS definition #3 fits exactly.
Every pilot should understand the effects of a wind gradient.
Surely we can do better in "the very best in technical discussion" than looking things up in various non-aviation dictionaries?
PS definition #3 fits exactly.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
flyer101flyer:
I did a phrase and word search in Aerodynamics for Naval Aviators.
Lots of "gradients" and lots of "wind," but no "wind gradient."
Wind component means something different than wind gradient. Ask the albatross.
Every pilot should understand the effects of a wind gradient.
Surely we can do better in "the very best in technical discussion" than looking things up in various non-aviation dictionaries?
PS definition #3 fits exactly.
Every pilot should understand the effects of a wind gradient.
Surely we can do better in "the very best in technical discussion" than looking things up in various non-aviation dictionaries?
PS definition #3 fits exactly.
Lots of "gradients" and lots of "wind," but no "wind gradient."
Moderator
"wind gradient" generally is used to refer to change of wind component with height. This is quite measurable at low level (ie boundary layer) especially over featureless terrain (eg oceanic). Important to the larger birds such as albatross.
Guest
Join Date: Apr 2009
Location: On the Beach
Posts: 3,336
Likes: 0
Received 0 Likes
on
0 Posts
J.T.:
Sort of what I said in Post #35:
"wind gradient" generally is used to refer to change of wind component with height. This is quite measurable at low level (ie boundary layer) especially over featureless terrain (eg oceanic). Important to the larger birds such as albatross.
Only in terms of rapid velocity changes in climb or descent in a jet.