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The Staff of SOH
Balance
- Thread starter WarpD
- Start date
WD:
Provide some data and specific info and perhaps we can help you figgure this out. Any and all of the above points that Sparks mentions can be culprits. Sparks has a utility on his website, and also there is the AFSD utility by Herve Sors which can measure the actual weights and CG. Typically the static CG should be near 25% of the MAC for the plane to fly well.
Taildragger, nose dragger?
Cheers: T.
Provide some data and specific info and perhaps we can help you figgure this out. Any and all of the above points that Sparks mentions can be culprits. Sparks has a utility on his website, and also there is the AFSD utility by Herve Sors which can measure the actual weights and CG. Typically the static CG should be near 25% of the MAC for the plane to fly well.
Taildragger, nose dragger?
Cheers: T.
I can't post details because it's a commercial release I'm working on. Don't wanna get kicked in the rear by the boss. 
I have gone over the data, repeatedly and found it all to be 100% to the RW data.
I can tell you that according to real world documentation, the empty CG is physically aft of the 1/4 MAC position.
When the aircraft is empty or loaded, with engines off... it will sit correctly. The moment an engine is started, it will start to go nuts.
What I wish I had was a physical reading of the leading edge MAC position in relation to the reference datum position. I've seen where Air Wrench displays the MAC rectangle and states it's size... but I didn't see any reading of it's position.
I have gone over the data, repeatedly and found it all to be 100% to the RW data.
I can tell you that according to real world documentation, the empty CG is physically aft of the 1/4 MAC position.
When the aircraft is empty or loaded, with engines off... it will sit correctly. The moment an engine is started, it will start to go nuts.
What I wish I had was a physical reading of the leading edge MAC position in relation to the reference datum position. I've seen where Air Wrench displays the MAC rectangle and states it's size... but I didn't see any reading of it's position.
J
jcomm
Guest
Is it a prop aircraft?
Bradburger
Charter Member
Contact Points
Could this be a contact points issue?
I've had similar issues in the past with both nosewheel and taildraggers, where all is ok as regards dimensions, balance and CoG etc. (it flies ok) but I've had strange behaviour in the ground. Checking and adjusting the locations of the wheels (and also their compression ratios/static compression) usually sorts this out.
I must admit, this is easier said than done if you don't have Aircraft Container Manager (ACM), as at least you can see where everything is/should be in relation to the MDL with it.
Thank god I got a copy when I did, as I'd be lost without it! :d
Air Wrench also lets you see the locations of the contact points in the 'Balance' section, plus it also has the very useful abilty to calculate the compression ratio of the gear legs for you.
Cheers
Paul
Could this be a contact points issue?
I've had similar issues in the past with both nosewheel and taildraggers, where all is ok as regards dimensions, balance and CoG etc. (it flies ok) but I've had strange behaviour in the ground. Checking and adjusting the locations of the wheels (and also their compression ratios/static compression) usually sorts this out.
I must admit, this is easier said than done if you don't have Aircraft Container Manager (ACM), as at least you can see where everything is/should be in relation to the MDL with it.
Thank god I got a copy when I did, as I'd be lost without it! :d
Air Wrench also lets you see the locations of the contact points in the 'Balance' section, plus it also has the very useful abilty to calculate the compression ratio of the gear legs for you.
Cheers
Paul
I agree with Paul, it is probably an issue with the contact points. FS can have a flubber effect causing airplanes to dance around or even do higher and higher backflips into the air! Jerry Beckwith's (Sparks) mudpond.org website has a good explanation of the relationship between static compression, compression ratio and dampening. Typical compression ratios run around 2.5 and danpening values between 0.80 and 0.95.
The now dead and departed Aircraft Container manager showed graphically the virtual airplane vrs the visual model. A teriffic help! Jerry's later Airwrench versions of course display the CG and % MAC, there is also a seperate section that graphically shows how you have your landing gear compression set up.
If your CG is not displayed, it is possibly so far out as to not be in the picture! FS takes the values in feet, many aircraft ballance sheets list the values in inches! The Center of the FS aircraft should be set up as near the aerodynamic center and the CG should be very close to this, less than a foot! Check to make sure there are no issues with units and zero points.
If you want to discuss this further feel free to send me a PM.
Cheers: Tom
The now dead and departed Aircraft Container manager showed graphically the virtual airplane vrs the visual model. A teriffic help! Jerry's later Airwrench versions of course display the CG and % MAC, there is also a seperate section that graphically shows how you have your landing gear compression set up.
If your CG is not displayed, it is possibly so far out as to not be in the picture! FS takes the values in feet, many aircraft ballance sheets list the values in inches! The Center of the FS aircraft should be set up as near the aerodynamic center and the CG should be very close to this, less than a foot! Check to make sure there are no issues with units and zero points.
If you want to discuss this further feel free to send me a PM.
Cheers: Tom
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I haven't touched AirWrench. My comment was based on viewing screenshots of it from the mudpond website.
Shane Olguin
Charter Member
If you're working on a commercial release you probably wouldn't need AirWrench anyway, as you're an advanced guy that doesn't require its services. ;-)
His issue turned out to be bad original aircraft data. If Aircraft Container Manager was still available, it is the best way to quickly find out if such things are screwed up. Peeking at existing FM's (such as for a port over or adjustment) one ocassionally finds some pretty far out things. Understandable!
Cheers: T.
Cheers: T.