BEST ANGLE vs BEST RATE of climb

[eaglectl]

Hello
Please explain what is vx and vy?
What I have learned is best angle of climb is that speed u gain max height at minimum distance. And best rate of climb is that speed u get max height at minimum time. So if two aircrafts with same configuration and weights and power under same condition start to climb to 5000 feet AGL.but the difference is that one is maintaining Vx best angle and the other one vy best rate of climb. My question is which aircraft will reach 5000 feet first. Please give aerodynamic reference?

[On Track]

I think you have already answered your own question.

The aircraft flying at Vy (best rate of climb speed) will get to 5000 feet before the aircraft flying at Vx (best angle of climb speed) but it will cover more ground in doing so.

Vx results in a steeper, slower climb while Vy gives a faster, shallower climb.

The POH will provide the relevant speeds for a particular aircraft.

[Jabawocky]

My cheeky response, which is of far more use to the young real world pilots, not those doing an assignment or theory exam.

The one who gets to 5000' with optimal engine parameters, and had greater safety margin in the early part of the take off is the pilot who used best rate plus 10-35 knots (depending on type).

He also got to 5000' a little further down range, and had a better view of traffic along the way etc.

:)

[MyNameIsIs]

Think about it simply.

Angle is a measurement in relation to the horizontal.
Rate is a measurement in relation to time.


Therefore:
Best angle will give you the greatest vertical height increase for the shortest horizontal distance travelled.
Best rate will give you the greatest vertical height increase for time airborne.


The aircraft are climbing at different airspeeds, and thus different groundspeeds.
You may be confusing yourself by stating that two identical planes are operating at the same power... don't forget that you could be at 100% power and pointing straight up, completely straight and level, or straight down- or anywhere in between, and so your rates and angles are all going to be different.

It all has to do with your power/thrust curves and which speed you get the max excess.

[Homesick-Angel]

Best Rate is based on excess power and best angle is based on excess thrust over what's available for straight and level flight.

Vy occurs at a higher airspeed than Vx and Vx occurs at a higher AoA than Vy so more induced drag at Vx.

Just think of rate being work done over time, so even tho the angle of climb as we look at it from the ground looks steeper, and it is, the best rate of climb gives us the best climb performance both vertically and horizontally(over a period of say 2 mins) mainly due to there being less drag to overcome at that angle of attack.

Several books cover it pretty well Bob tait for basics and mechanics of flight for something a little more in depth..

[Jabawocky]

based on excess power

There is no such thing :} Too much is almost enough! :p

[Homesick-Angel]

Particularly in a 40 year old 152..

[Jack Ranga]

What's the difference between excess power & excess thrust?

[RENURPP]

Vx is maximum excess thrust over thrust required for LEVEL flight

Vy is maximum excess power over power required for LEVEL flight
What's the difference between excess power & excess thrust?

Power = Thrust * velocity
so whenever you know the thrust of an airplane, you can figure out how much power it's developing by multiplying that number by how fast the airplane is going. Thrust is the more fundamental concept, because without thrust, you have no power.

One way I think about it is that power incorporates not only the concept of thrust, but also the velocity that the thrust produces. This is useful in certain contexts, because some aircraft performance parameters depend on that velocity.

For instance, your angle of climb depends on how much excess thrust you have. The velocity of the aircraft along that flight path is irrelevant. If my climb angle is 45 degrees, it remains 45 degrees no matter how fast I'm flying.

However, rate of climb depends on power. If my climb angle is 45 degrees, the faster I fly along that flight path, the greater my rate of climb is.

[Jabawocky]

RENURP

How about this explanation, for the engineers in the audience.

Power is Torque x speed, in a rotational sense as you have in an engine. Thus (Torque NM x RPM)/9550 = kW.

Thrust is the force generated by a fan, prop or exhaust gas expulsion (rockets). So the thrust from a Prop or Fan is the reactive force which is generated by the power ((nmxrpm)/9550)of the rotating fan/prop blades.

So in order for you to have excess thrust, to accelerate S&L or to climb, you need to have excess power. (which I have stated there is no such thing :E)

:ok:

[ga_trojan]

Someone get Stephen Holding to post on this he is the guru of these things and can actually explan it properly.

Also worth noting that thrust is the air moved rearward, power is what the engine delivers to the shaft.

[Goat Rider]

So to summarise there young grasshopper, if you thrust at best power with your best angle you will get to the end at your best rate.

[FokkerInYour12]

a) Best angle = least ground distance. Use this for short runways/trees at end etc.

b) Best rate of climb = use this for headwinds at low levels.

c) If no obstacles, no low level headwinds, add an additional 10+ knots (for a single) for most efficient a-b on fuel burn. Somewhat nicer on the engine too (more airflow over the jugs).

a) and b) are in the POH. c) is not taught but experienced.

Wait until you do formation flying... then for formation takeoffs you do Vwa(worst aircraft) less a fudge factor so they can remain in formation. First time you do derated takeoffs your brain is going "nooooooooooooooooooooooo".

[MakeItHappenCaptain]

My cheeky response, which is of far more use to the young real world pilots, not those doing an assignment or theory exam.

The one who gets to 5000' with optimal engine parameters, and had greater safety margin in the early part of the take off is the pilot who used best rate plus 10-35 knots (depending on type).

So why wouldn't using best rate to gain the most height initially (which would also give you the greatest choice as to where to go in the event of an engine failure after take-off) be of any use to a "young real world" pilot?
Why does the manufacturer bother telling you what best rate is if you aren't supposed to use it?

If you can't react fast enough to get the nose down by the time the airspeed drops to Vs, then I would suggest you need to get an instructor to spring a few more EFATO's at you and start using a pre-take off safety briefing.

eg.
If the engine fails while airborne I will lower the nose to maintain control...

After your first 1000' AGL you can reduce attitude to a cruise climb and I can guarantee you won't be damaging your engine.

Wait until you do formation flying... then for formation takeoffs you do Vwa(worst aircraft) less a fudge factor so they can remain in formation. First time you do derated takeoffs your brain is going "nooooooooooooooooooooooo".
Otherwise known as flying to the lowest common denominator.:E

[Jabawocky]

MIHC

You probably have multiple times my flying experience and thus argue most things I post here it seems, but my comment above was based on things taught to me in detail by Chimbu Chuckles and John Deakin, JD who sat at my kitchen table recently over breakfast explained it again, for the umteenth time. I have read and talked to him about these kind of things several times before, but I learn something new every time.

The fact that in practise, what they have taught me works, suggests that in their collective 60'000 hours of flying more things in more places than I care to think about, not doing the same thing 60,000 times, suggests to me I should pay attention.

I am not going to even try writing it all down here, but it has been written by both of them over the years, so all I ask is do a search. Or just simply ignore this post, as I can't do it justice, or not without spending several hours.


If you can't react fast enough to get the nose down by the time the airspeed drops to Vs, then I would suggest you need to get an instructor to spring a few more EFATO's at you and start using a pre-take off safety briefing.

I would agree 100%, but you missed the point, or never had it. Besides from Best rate to Vs is a long time, but best glide is what you are searching for, and what is the most effective way to get there.

After your first 1000' AGL you can reduce attitude to a cruise climb and I can guarantee you won't be damaging your engine. Did I say engine damage? I said to 5000 with optimal engine parameters. :ugh: Read and use in context would ya. :ugh:

I think Fokker gets this. The POH is a book written with a description of the entire envelope (hopefully) and LIMITATIONS and scattered with some examples. There are infinite variations along the way inbetween that may be better for daily use or for special use. You the pilot need to use critical thinking to determine what is most suitable for the task.

[Wally Mk2]

'F12' said it simply & to the point, Vx being the one that really matters if you need to clear an obstacle.

Some very in depth answers here, you guys need to get out more:-)


'Jaba' why would yr mates be there for breaky?...yr not changin' are ya buddy?:E


Wmk2

[WOOLLY]

I see Best Angle as obstacle clearance only, short distance height gain but long term pain, bad L/D ratio. Once clear of obstacle go for Best Rate- efficient climb, best L/D ratio, will get to altitude sooner-just over a longer distance.

[Flying Binghi]

Heck, just install more horsepower and yer dont need to worry about all this stuff..:}







.

[Jabawocky]

FB

Yer not wrong! Too much is almost enough


'Jaba' why would yr mates be there for breaky?...yr not changin' are ya buddy?

They were hungry Wally :} Mrs Jaba's cooking perhaps.
Just staying here for a couple of weeks, seeing the sights, doing some work. All good fun.

[Anthill]

For initial climb speed it depends on what you are trying to achieve.

If there is a terrain/obstacle the best angle is the speed that you want until you are above it and at a safe height. As an example one might wish to climb at Vx until above MSA/LSALT-good airmanship! Best angle is also best to use until you are pointing the aircraft in the direction of outbound track. Vx will get you over a line of weather, whereas Vy might climb you through the cloud tops.

The best RoC , Vy, will get you above conflicting traffic quicker (not all the time, Vx may be more appropriate in some instances) and into tail-winds quicker. If you are climbing into a head wind, you might want to consider a cruise climb speed that is greater than Vy as best rate will just climb you into an increasing head-wind.

What Fokker12 said :ok:

[MakeItHappenCaptain]

Jaba,

Yes, we certainly do have a difference of opinion on many topics, but please don't think I'm specifically targeting every post you present. If I was there would be a great many more posts to my name. On the contrary, I do find your passion and research commendable and belive you to be one of the more knowledgeable types on this site, but the fact remains, we have only been flying for just over 100 years and no-one yet knows ho to do it perfectly.

Just so you don't think this post is a sunshine blast;
While I may present a differing opinion, I will always have a reason to support my view; in this case maximising height gain for the initial climb as being the "safest" option. Not convinced "optimal" engine parameters will be deviated from by this course of action, but just covering the worst case rebuttal with the damage comment. Didn't say that you said anything about damaging an engine, but you have a pretty broad definition of "greater safety margin" in there.

I asked why wouldn't you use Vy as the safest option? I would like to know which GA type flown by a "young real world pilot" is going to use Vy+35Kts as the "safest" way to climb.:confused:

[Jabawocky]

MIHC

OK maybe its the tone and the written word, but the last one is far more effective.

Vy does not give you as much inertia and as has been explained to me, and shown by in flight testing with Chuckles a far better real world transition to best glide and successfully achieving the impossible turn.

One point of course....KNOW YOUR AIRCRAFT.

With many types as you no doubt fly this is a vast and wide experience base, but it would be interesting to get your results of tooling around experimenting. Maybe you do not get the opportunity to do that as much as you might like.

While Vy is the best rate, the trade off for a few extra knots in terms of speed and thus kinetic energy (1/2MV2) is that you get much more energy for very little loss in ROC. It is all about losses. Someone has already mentioned best L/D.

If I can get JD to drop a line he will explain it far better in far fewer words. I have flown with Chuckles in a Bonanza where he demonstrated this perfectly. I can't argue the results, simple as that.

The initial climb is in my view only a few hundred feet, of me it is until the turn back is so easily achived it is easy. In my a/c that is 400', others could be 1000'. Know your aeroplane. After that Vy is not optimal at all, somewhere above best L/D is better across the board. The transition from where the nose wheel breaks ground (or TW) to the point above 1000' is a gradual progression. To think of it as Vy all the way is not realistic.

would you climb all the way to 5000 feet on the edge of the blue line in a twin? No.

I said before that there is some learning to be had from a google search, well I got sucked in and did it for the benefit of the silent majority.

Enjoy this. Pelican's Perch #85: Where Are The Eyes? -- Part 1 (http://www.avweb.com/news/pelican/pelicans_perch_85_where_are_the_eyes_195130-1.html)

The pearls here are towards the end.

Part 2 is Pelican's Perch #86: Where Are the Eyes? -- Part 2 (http://www.avweb.com/news/pelican/pelicans_perch_86_where_are_the_eyes_part_2_195465-1.html)

I hope everyone enjoys and learns something from these. Use critical thinking.
I am blessed I tell ya for my privileged of friends such as these.

[Jack Ranga]

Jab mah man :ok:

JD's knowledge of such things pisses all over anything anybody on this site could post. The bloke is a certified aviation legend :ok:

I've always gotten a bit tongue tied with my explanation of excess thrust verse power. RENURP's explanation was pretty good but I've never heard a plain lingo explanation that cuts the mustard on this subject. My question was a Dorothy Dixer & I'm still waiting for all the plain lingo explanations...............

[Anthill]

would you climb all the way to 5000 feet on the edge of the blue line in a twin?
No.

I can't see why anyone would want to climb at Vyse (blue line) when Vx (all engines operating) would be the appropriate speed under normal circumstances.

Regarding initial climb speed? This would depend on the circumstance. A departure from an aerodrome where the LSALT for the route is 5000', the answer would be to climb at Vx to 5000'.

Once terrain clearance has been made, accelerate to the desired en-route climb speed.

[Jabawocky]

Exactly :ok: