AirWrench entries?

[pstrany]

Hi;

I've finally got around to doing some serious tinkering with AirWrench (very nice!) but I have a few questions about some of the entries that I just don't understand.

In Ailerons, what is Target Roll Rate and speed? Is this simply how fast the aircraft will roll at a specified speed?

Under engine, what is Critical altitude? What is Actual normal HP, and how does it relate to normal rated HP? In the prop section, what is Beta Min and Beta Max?

Under Tune-up, what is P-factor? Torque effect seems to be the prop's ability to "turn" the aircraft. Gyro precession on yaw and roll is what?

Guess that will do it for now, this tool is a real help, especially for those of us who never got around to getting that degree in aeronautical engineering. I have managed to destroy several perfectly serviceable flight models so far, but I'm starting to see how this tool helps tweak things, and hopefully as I learn I'll get a little better at it......

Paul

[fliger747]

Paul:

Some data is available for the roll rates of many period aircraft, though this seems to be one of the murkier areas. America's Hundred Thousand for instanace does have a few partial curves and data points. By specifying a roll rate and target speed you can modify the amplitude and shape of the curve within limits imposed by the aircraft geometry. For a Zero that I am currently working on, I was able to actually get the roll rate to decrease with speed beyond 220 knots or so by specifying the target speed fairly low. Some other aircraft such as the F4U had much better roll rates at higher speeds and were a bit mush at low speed. Experiment with different values and see how the curve moves.

Critical altitude is a super/turbo charged piston engine term, it is the altitude to which it can maintain rated power, typically into the mid twenties for many WWII fighters.

Say for a R2800 10W, the normal rated HP is 2000, at this point you need some test guages, Jerry has some good ones, or the AFSD ones are goos as well. With these you can measure the 'actual' HP and enter that in the actual normal HP block. This computes a 'fudge factor' to correct the actual measured HP. You may need to do this a couple of times.

Props get a bit more complicated and I suggest you find a good reference, but basically P-factor has to do with asymetric development of thrust across the propeller disc due to changes in angle of attack of the blades through the rotational cycle due to variation from alignment of the prop disc to normal to the airflow. Beta is the angle of the prop blade, usually measured at about 75 % of the distance from the hub. The values stated are max-min values that the constant speed prop can use to maintain specified rotational velocity.

My understanding as a pilot is that torque as it is called is actually a screwlike swirling of the airflow behind the prop, which impacting the verticle stabilizer at an angle causes the aircraft to want to swing.

Gyro Precession, well as a fairly heavy spinning mass a propeller has gyroscopic precession charcteristics. Th get a handle on how this works see if you can find one of those old kids gyroscopes somewhere, or even a fan, pick it up and try to turn it, you will feel a resisting force.

Perhaps Jerry can explain this better or correct any errors.

Cheers: Tom...

[Henry]

Paul:


Say for a R2800 10W, the normal rated HP is 2000, at this point you need some test guages, Jerry has some good ones, or the AFSD ones are goos as well. With these you can measure the 'actual' HP and enter that in the actual normal HP block. This computes a 'fudge factor' to correct the actual measured HP. You may need to do this a couple of times.



Perhaps Jerry can explain this better or correct any errors.

Cheers: Tom...
well i certainly cannot:redf:
you can find the test panel and gauges here
certainy a must
http://www.mudpond.org/
H

[sparks]

I've been working on answers for these questions in my spare time over the past few days. I think Tom's answers are pretty much spot on, so my comments may not add all that much.


> In Ailerons, what is Target Roll Rate and speed? Is this simply how fast the aircraft will roll at a specified speed?

Yes. AirWrench will attempt to set up the air file so the estimated Roll Performance graph displayed peaks at the specified roll rate and airspeed.

The Aileron Parameters (area and deflection angles) along with the wing span determine the Helix Angle.

Helix Angle is perhaps the best size-independent measure of how resonsive an aircraft will feel. During WWII, NACA found that it didn't matter if an aircraft was a fighter, attack aircraft, heavy bomber or transport, if the helix angle was greater than 0.07 degrees, pilots perceived the aircraft as responsive and controllable.

> Under engine, what is Critical altitude?

In FS, horsepower for turbocharged engines is constant from sea-level to the critical alitude.

> What is Actual normal HP.

The maximum horsepower measured in FS at run-time.

> How does it relate to normal rated HP?

AirWrench attempts to set up the air file to match Normal Rated HP, but it's not totally accurate.

(There's also a page in the AirWrench Tutorial devoted to tuning engine performance.)

> In the prop section, what is Beta Min and Beta Max?

These are aircraft.cfg parameters, included in AirWrench for your convience.

> Under Tune-up, what is P-factor? Torque effect seems to be the prop's ability to "turn" the aircraft. Gyro precession on yaw and roll is what?

These sliders are used to set the corresponding scalars found in the aircraft.cfg file.

If there's anything you don't understand about aircraft.cfg parameters, see the FS2004 Aircraft Container SDK on the MS FS2004 website.

http://www.microsoft.com/games/flightsimulator/fs2004_downloads_sdk.asp#aircraftcontainer

Many of the default FS2004 aircraft.cfg files are also very well commented and may be more comprehensible than the MS SDK docs.