Beagle Pup experiment

[IAHM-COL]

Taxing? negative bombers. Its too shallow for real turns, unless I want to use all the state of New Jersey to line up my runway in JFK.

I've just gone around KSFO as if it's a race track...

honest..

Video time....

[sanhozay]

Have we got the latest version? The max_steer is 2 degrees in what I have. Which isn't much by any standards.

[IAHM-COL]

no new version. Turning this bitch is a b.....

[sanhozay]

Going back to Richard's FDM for a moment (if he's still reading) ...

I had a look at some of the numbers and the inertia values are much higher than my Aeromatic++ FDM or those of broadly similar aircraft like the C172P and DHC2. I tried increasing my ixx, iyy and izz and I did get similar behaviour to your FDM. Perhaps that's an area to look at -- are they valid and how did you end up those numbers?

[bomber]

I'm learning how to 'drift' my pup.....it's like an episode of Fast n Furious here...

[Richard]

Been looking at the MOI since you mentioned it; as I think you're probably right. The lightest certified sim I've flown is about 10,000lb and I've only got 30 minutes on a Cessna (152) - which was so long ago I can't remember; so the higher inertias probably felt right to me because of this, but they're clearly not.

Trouble is that I can't remember exactly where I got the numbers that are in the FDM from. I think it might have been VSPAERO, or it could have been a random website. I looked at the formulas from Roksam, but these aren't good enough.

So I recalculated using VSPAERO, with an extra lump at the front to represent the engine. Now the trouble with this is that I had to estimate the density for engine - the rest of the body is at 1.0; so by a bit of trial and error I came up with a density of 12; i.e. the engine is 12 times more dense than a fuselage section. This gives the aircraft mass as 785 - but I'm not actually sure what this represents as VSPAERO is dimensionless.

This is what I get from VSPAERO. I think it flies better.

Code: Select all

  <ixx unit="SLUG*FT2">3511</ixx>
  <iyy unit="SLUG*FT2">14135</iyy>
  <izz unit="SLUG*FT2">16505</izz>
  <ixz unit="SLUG*FT2">293</ixz>


At the moment I'm struggling to understand the pitch instability; I'm going back and rechecking all of my geometry, the aircraft aligns with the 3view that I have but that isn't exactly reliable - the exact positions in x,y,z of the surfaces and a definitive source for mass/balance (CoG) information is what I've got to find.

So at the moment I'm fairly happy that the wings are the correct area, span and therefore chord. I'm not certain about the wing dihedral, incidence or the exact parameters for the airfoil (as the NACA 63(2)615 has a degree of flexibility in the parameters in VSP, so I'm assuming that (subscript) 2 is a=0.2). From the pictures the horizontal tail seems to have an incidence, maybe this is just relative to the wings not the FRL, but hard to be certain. If there was one of these near me I'd be tempted to measure it all properly (or to the best of my abilities) - but up until them I'm just going to have to rely on what I can find.

[IAHM-COL]

@bomber

My video

Flying the T4T-beagle
AVAILABLE NOW

Notes:

1. I did extra loop on the apron to show you the taxi behavior. I used hud so you can see I put the rudder to extremes to still get very mild behavior
On the taxiway I actually applied differential brake several parts to keep somehow in control. Clearly not a nice view this taxiing.

2. all stick flying. Tried the elevator trim to no good. It's like no trim existed. I ignored aileron trim for what we've discussed.

3. Flying a non-standard pattern to the right 1500 @ KJFK. (sorry if RL does not allow VFR operations here. This is FG! )

4. The pattern was ok. I didn't do "great" but somehow that's the pilot. Not the plane. As you can see the plane did behave rather nicely, but I didnt do much rudder corrective on the turns. Still could get rather nice sharp fast turns. Good speed, good flyability.
once again. Check the Hud. I am stuck to the stick. Releasing my stick means up-attitude, + fast left roll. (Dont know if we already discussed this is all expected. I may do another video tomorrow to show what if I let the stick go under controlled flight)

5. Landing. Sorry about that Pilot in Command Error. Approach came really good, and I lost concentration on the RWY threshold.

(but pilots survived... so: If you walk away....... Its' a good landing! )

[bomber]

guys try these values in your flight damage model file..

Code: Select all

    <ground_reactions>
        <contact type="BOGEY" name="nose">
            <location unit="FT">
                <x> -0.98 </x>
                <y> 0.0 </y>
            <z> -4.146 </z>
         </location>
         <static_friction>  0.80 </static_friction> <!--  the smaller the number the easier the tire tread breaks from the road surface causing a SKID -->
         <dynamic_friction> 0.5 </dynamic_friction> <!--  the smaller the number the easier to wheel spin  ? -->
            <rolling_friction> 0.05 </rolling_friction> <!--  the larger the number the more thrust needed to INITIALY get the wheels rolling -->
           <spring_coeff unit="LBS/FT"> 2400 </spring_coeff> <!--  weight * 1.5 -->
            <damping_coeff unit="LBS/FT/SEC"> 360 </damping_coeff> <!--  spring_coeff * 0.15 -->
            <damping_coeff_rebound unit="LBS/FT/SEC"> 36 </damping_coeff_rebound> <!--  damping_coeff * 0.1 -->
            <max_steer unit="DEG"> 2 </max_steer>
            <brake_group> NONE </brake_group>
            <retractable>0</retractable>
        </contact>

        <contact type="BOGEY" name="left_main">
           <location unit="FT">
                <x> 3.74 </x>
                <y> -3.28 </y>
                <z> -4.1 </z>
            </location>
         <static_friction>  0.8 </static_friction>
         <dynamic_friction> 0.5 </dynamic_friction>
            <rolling_friction> 0.05 </rolling_friction>
            <spring_coeff unit="LBS/FT"> 3265 </spring_coeff> <!--  weight * 2.1 -->
            <damping_coeff unit="LBS/FT/SEC"> 490 </damping_coeff> <!--  spring_coeff * 0.15 -->
            <damping_coeff_rebound unit="LBS/FT/SEC"> 49 </damping_coeff_rebound> <!--  damping_coeff * 0.1 -->
            <max_steer unit="DEG"> 0.0 </max_steer>
            <brake_group> LEFT </brake_group>
            <retractable>0</retractable>
        </contact>

        <contact type="BOGEY" name="right_main">
           <location unit="FT">
                <x> 3.74 </x>
                <y> 3.28 </y>
                <z> -4.1 </z>
            </location>
         <static_friction>  0.8 </static_friction>
         <dynamic_friction> 0.5 </dynamic_friction>
            <rolling_friction> 0.05 </rolling_friction>
            <spring_coeff unit="LBS/FT"> 3265 </spring_coeff> <!--  weight * 2.1 -->
            <damping_coeff unit="LBS/FT/SEC"> 490 </damping_coeff> <!--  spring_coeff * 0.15 -->
            <damping_coeff_rebound unit="LBS/FT/SEC"> 49 </damping_coeff_rebound> <!--  damping_coeff * 0.1 -->
            <max_steer unit="DEG"> 0.0 </max_steer>
            <brake_group> RIGHT </brake_group>
            <retractable>0</retractable>
        </contact>

elevator trim... it's a cheap version I use as I've yet to link it to dynamic pressure... but pressing number pad 7 & 1 should change the trim... it's very fine though, so you have to keep your finger pressed down.

Also I'm using version 3.4, what version of FG are you running.... cause I can't work out why you aint steering..

I'm going rally crossing in the pup.... it's great fun.

[IAHM-COL]

2016.4

[bomber]

4. Performance is certainly closer to what I'd expect but it does get off the ground very easily on my 830m test runway, maybe half way down. As with Richard's FDM, there seems to be too much power at idle throttle -- it races away when the parking brake goes off.

You aren't firewalling the throttle are you, cause the speed with which you apply the throttle will effect the take-off distance.