Rate of Climb / Angle of Ascent

Steve Smith · 29 January 2004, 10:45 AM

Hi -

I am trying to find some performance data For the DR1 & SE5. What I am looking for is the angle of ascent for the best rate of Climb. To calculate the angle of ascent using the rate of climb, you need to know the airspeed of the plane. Would the airspeed be the stall speed or would the best rate of climb be with a smaller angle of ascent and a higher air speed. Is there a reference or website that would give such performance data?

Barrett · 29 January 2004, 04:20 PM

An airplane cannot climb while stalled--I know--I've tried!

Best rate of climb is not necessarily the best climbing airspeed, if you know what I mean (and I ain't REAL sure that I do!) Rather, the rate of ascent, as you note, may not be the fastest the machine can go with the nose pointed above the horizon. Like every other maneuver, it's a compromise. Presumably what you want is best SUSTAINED rate of climb.

Haven't run across any web sites that address the matter.

30 January 2004, 08:29 AM

For whatever this is worth, best climb rate will occur at a speed where the a/c enjoys maximum excess power availability at the prop.

This gets a bit complicated to calculate for early a/c with fixed pitch props. Although the engine might produce a steady amount of power at the crank hub, the efficiency of their fixed pitch props in translating that engine power into the air will vary according to the design of the prop and the airspeed at which the a/c is moving relative to the optimum speed regime within which the prop was designed to operate. For example, a coarse pitch prop optimized for high speed flight will show relatively poor efficiency at slower climb speeds and a finer pitch prop optimized for best efficiency at climb speeds will reduce the maximum speed of the a/c. This broadly equates to transmission gears in an automobile - top gear for highest speed, lower gear for best hill climbing ability.

When addressing the matter of the Dr.I, there are some tantalizing hints circulating (see

Three Wings for the Red Baron, for example) that Dr.I's were possibly equipped with different type props - i.e., that props optimized for climb rate may have been fitted later during the service career of the Dr.I.

Byron

timjnf · 30 January 2004, 10:57 AM

Quote:

An airplane cannot climb while stalled--I know--I've tried!

You just didn't have a high enough power to weight ratio

If you know the time to climb to a certain altitude and the speed at which you would normally climb (either from published stats or from someone who has flown the aircraft in question,) you could then figure out how many miles you'd travel (slant range (D=V*T)) in the amount of time it took to complete the climb. Simple trig would get you the angle.

SineΘ=Altitude/Horizontal distance flown during climb

(The angle will vary if there is a headwind or tailwind)

For instance: Your aircraft's climb speed is 70mph. Time to climb to 4000' is 6 minutes.
Horizontal Distance = 70*0.1 (0.1hrs = 6 minutes) = 7 Miles = 36960 feet.

SineΘ=4000/36960 = 0.1082 Which means Θ = approx 6 degrees

Any mathematicians out there? Did I get my math right?

greenknight · 30 January 2004, 11:22 AM

Steve,

There are a few books you might find helpful for understanding climb performance, and the factors affecting it.

Any Private Pilot training manual such as those by William Kershner or Jeppesen would have a discussion of the significance of the various climb speeds such as the speed for "best rate" vs. "best angle" of climb.

The classic "Stick and Rudder" by Wolfgang Langewiesche (written in the 1940's) has a chapter called "The Working Speeds of an Airplane" which should also be helpful.

At least one of Barry Schiff's books (I believe "The Proficient Pilot: Volume I") also has a nice practical discussion of climb performance, and I think maybe some rules of thumb for estimating these speeds relative to stall speed, etc. for (relatively modern) light aircraft.

Check your local library. You can also find a WWI Era flying instruction manual posted online. Don't know what it says about climb specifically but worth checking out:

http://www.warillustrated.com/practicalflying/

From time-to-time journals like "World War I Aero" publish pilot reports, on WWI types, both those written back then, and ones done recently on reproductions and restorations. A few years back they carried an excellent article by Javier Arango comparing flying 2 Fokker D.VII reproductions, one of which was Mercedes powered.

Hope this is of assistance.

Barrett · 30 January 2004, 05:06 PM

A loud "Amen" to Green Knight's endorsement of "Stick & Rudder." If you're gonna read one How To Fly book, that's it. My dad made me read it twice before I started flying, and it made the instructor's comments more lucid to me. Just a terrific example of expository writing.

FlyXwire · 31 January 2004, 02:24 AM

Steve,

Here's a page on achieving optimum angle/rate of climb from John S. Denker's excellent online flight tutorial See How It Flies:

Chapter 7

The best information on flying the Fokker Dr.I (IMO) is found in Paul Leaman's book Fokker Dr.I Triplane, A World War One Legend, still you'll be lucky to find anything close to the specific data you're seeking on any WWI aircraft. This is why the era of early aviation is so fascinating...........so much has to be inferred, and so many contradictions reconciled to arrive at the "truth".

Much of our present day understanding of aerodynamics and aeronautics comes from post-WWI research..........even our vernacular has changed over the years! Here's a research document prepared in 1920 that might prove interesting although it's only indirectly related to the discussion subject here (I find it formulates essential rationale for understanding and speaking about WWI aircraft flight performance though):

NACA Report 105

Researching the era of early aviation will continuely lead to greater discoveries, and just like back then much of it today continues to be by the seat of your pants!

Barrett · 31 January 2004, 09:19 AM

Good point about What They Knew. The flying technique employed in WW I appears sensible from our perspective because we grew up with Theory of FLight, etc. It's pretty clear, however, that many Great War guys just did whatever it took without much concern as to reasons & theory. One example is in Chris Draper's "The Mad Major" in which he had trouble rolling a Camel (intentionally, that is!) The instructor merely said, "Fly it through." IIRC Draper went away perplexed, wanting more detailed info, but found with experimentation that what appeared to have been control reversal over the top was just logical use of the rudder to keep the nose up while the wings passed thru the horizon.

Steve Smith · 31 January 2004, 01:05 PM

Thanks for all your comments-

I have read Leamans book and " Three Wings" , both of which are excellent but perhaps I need to comb them a bit more thoroughly.

It sorta surprises me though that this info would be so esoteric or hard to find. What do the develpers of the various flight sims or game designers use as a basis for the flight performance of the planes they are simulating, especially some of the more obscure types that dont have the documentary coverage that the SE5 & DR1 have?

FlyXwire · 31 January 2004, 04:00 PM

Well Steve, they model the aircraft as accurately as possible, plug in the know flight parameters, and let the physics model spit out a "rough draft"...........then it's on to reconciling the differences between the simulated model's flight performance and the existing record of contemporary and historical flight accounts for more tweaking.

Let's hope Knights Over Europe gets us in the ballpark!

Hey Barrett, I always enjoy your comments..........keep em coming!