Super cat video,out of balance.

[flyerme]

Took th supercat up this mourning,and defenately nose heavy! notice the s;ight porposing on take off but approach mderate porposing needing throttle to keep her up,had to look back to confim elervator was doing what stick was..enjoy

 

 

 

[ayavner]

Where is the camera on that? How is it mounted? Beautiful video, glad you made it back down safely ;)

 

 

[Deskpilot]

thanks Flyerme. Quick flight, not the best weather conditions though. That cat sure does skid around corners don't she. All the same, very nice landing.

 

 

[flyerme]

Where is the camera on that? How is it mounted? Beautiful video, glad you made it back down safely ;)

Its mounted on the tail..air race style..lol fibre glass tape.lol

 

 

[flyerme]

thanks Flyerme. Quick flight, not the best weather conditions though. That cat sure does skid around corners don't she. All the same, very nice landing.

Hey Doug,thats not the weather....it was smooth but I was fighting to keep the nose level,notice in turns skidding and nose kept dopping ,,landing is all plane(NOT WEATHER) nose kept dropping and needed almost full elevator and throttle bursts to keep nose up..to round out I neede a quickburst to get the nose up for flair and full back pressure.

 

 

[Guernsey]

Out of balance??? Fit a heavier camera.

 

Only joking as usual, however it was a good video and you did an excellent job under the circumstances.

 

Alan.

 

 

[facthunter]

You really should fix it. It's not the only plane that has a massive CofG change with fuel load in a forward tank. If you get them tail heavy when the fuel is low it's much more dangerous, than front heavy. Nev

 

 

[flyerme]

You really should fix it. It's not the only plane that has a massive CofG change with fuel load in a forward tank. If you get them tail heavy when the fuel is low it's much more dangerous, than front heavy. Nev

Hey Nev,just before this flight I drained 17ltrs leaving 25 ltrs in tank,(have flown with 35 ltrs no issue),,the new engine is identicle,and now has had a piece of exhaust removed and the pullstart bell removed so should be less wieght? only thing different is 2 air intake scoops on the each side of the cowling?also the bottom of cowling has been cat away(for more air exhaust),but it was noticed by another pilot test flying with NO cowling,he noted nose heavy? engine is sitting in exact same position?yet another super cat mystry.....can,t find the c of g any where???????????????????????no info???? wieghed and messured today and just starting the number crunching, first 2 calculations came up 4.56ft and 4.62 from datum(front of prop mount, this puts th c of g 3 " behind the leading edge..(about 8%) Im guessing it that c of g should be aroung 25%?

 

 

[flyerme]

found it..you can stop looking now? c of g...lol 25%(12")-35%(16"),ideal 30%=14.3"....

 

my c .of g =1/2 tank fuel 14.7" full tank =13.2 " empty =15.1" so all within range....hmmm so I have removed side air intake scoops,and refitted bottom of cowling ,also re measure of engine mounts and engine sittin 4mil higher..will lower back 4 mil today and have it ready for test 3 thurs....

 

 

[facthunter]

Well those figures sound fine. Is the horizontal stabiliser adjustable? You might have to look there as you are running out of elevator at low speed. Nev

 

 

[flyerme]

Ok been up another 2 times after removing side scoops and replacing bottom of cowling, still the same but I think I have an idea whats goin on? asi out? first landing noted thottle off and nose her over and she wants to continue?needing a lot of back stick to hold her,but give some throttle and she seemed fine? first landing nice,but noted asi,stuck at 60knts and then joollt down to 50 knotts? second fly,landing came in at 55-60 knotts and noted wing drop a couple of times and plane felt very slopy.ground speed seemed fast but as I set 55 knotss(50 being real appoach speed) at around 20ft hight she started to shutter and droped on the strip, I bounced back 10ft gave a lil throttle ,levelled and put her down gently. really sus on the asi? but felt nice and stable in level flight set at 60 knotts,noted engine sets pitch?drop revs and she noses over give her throttle(NO stick) snd she instantly climbs. sure do wish it like the trusty thruster on approach?went for an awesome fly in the thruster last night and set approach and was able to take my hands off and pour a cupper and eat some bickies on the way down...well almost..

 

 

[Guest Maj Millard]

Flyerme, the fact that you need to use a bit of power to raise the nose is significent. You are doing one of two things there, either increasing airspeed a bit plus blowing extra lift over the wing which raises the nose, or two, the thrust line of the prop is off, and you are adjusting the longatudinal axis with the power-increase which because of the angle of the prop raises the nose. I'm thinking the later or a combo of both.

 

As a rough guideline, when the wing airfoil is at the flying/lifting angle, (level cruise) usually around 3-5 deg depending on the aircraft type, the prop should be pretty much vertical (view from the side) to the longatudinal axis which runs nose to tail through the the fuselage from approx the prophub back.

 

Slight adjustments to this prop angle can make huge changes to the way the aircraft flys and handles. Often this can be suitably adjusted by adding or removing a washer or two under the rear engine mount rubbers. The Supercat being a relativly short aircraft, will notice this effect more than say a longer aircraft.

 

From the sound of your in-flight experiences the top of the prop (viewed from the side) would be too far to the rear, so you may need to raise the rear of the engine a bit.Generally the prop wants to travel through the air in a vertical position, and the aircraft simply wants to follow it. If your prop agle to the plane is all wrong, then the plane won't be happy in flight. This degree of unstableness changes with different applications of power.

 

Rough guidelines only, give the whole thing a good deal of thought and treat each flight as a test flight until your happy...If everything is set up right, changes in power should not rapidly effect pitch, it will of course effect lift produced by the wing which will of course cause the nose to drop slightly. If it has the opposite effect of raising the nose the thrust -line of the prop is off for sure.......................................................................................................Maj...

 

 

[flyerme]

Flyerme, the fact that you need to use a bit of power to raise the nose is significent. You are doing one of two things there, either increasing airspeed a bit plus blowing extra lift over the wing which raises the nose, or two, the thrust line of the prop is off, and you are adjusting the longatudinal axis with the power-increase which because of the angle of the prop raises the nose. I'm thinking the later or a combo of both.As a rough guideline, when the wing airfoil is at the flying/lifting angle, (level cruise) usually around 3-5 deg depending on the aircraft type, the prop should be pretty much vertical (view from the side) to the longatudinal axis which runs nose to tail through the the fuselage from approx the prophub back.

Slight adjustments to this prop angle can make huge changes to the way the aircraft flys and handles. Often this can be suitably adjusted by adding or removing a washer or two under the rear engine mount rubbers. The Supercat being a relativly short aircraft, will notice this effect more than say a longer aircraft.

 

From the sound of your in-flight experiences the top of the prop (viewed from the side) would be too far to the rear, so you may need to raise the rear of the engine a bit.Generally the prop wants to travel through the air in a vertical position, and the aircraft simply wants to follow it. If your prop agle to the plane is all wrong, then the plane won't be happy in flight. This degree of unstableness changes with different applications of power.

 

Rough guidelines only, give the whole thing a good deal of thought and treat each flight as a test flight until your happy...If everything is set up right, changes in power should not rapidly effect pitch, it will of course effect lift produced by the wing which will of course cause the nose to drop slightly. If it has the opposite effect of raising the nose the thrust -line of the prop is off for sure.......................................................................................................Maj...

very interesting,I was thinking a thust line issue so when I removed side scoops ,I replaced bottom NEW(higher 5mil) with origanal bottom mounts,No change, but I wonder if whilst replacing engine I droped a washer above the mount plate? oh well cowl off yet again and get the fine toothed comb out... and thank you muchly.......... I want all opinions and all the suggestions one could think of..even the un likley ones...

 

 

[facthunter]

Check where you static port(s) are (for the ASI). If it is vented to the cockpit the ASI will read high at low speeds. Practice flying slow at a safe height and see what indicated speed relates to "at the stall". Nev

 

 

[flyerme]

Man yo

 

Check where you static port(s) are (for the ASI). If it is vented to the cockpit the ASI will read high at low speeds. Practice flying slow at a safe height and see what indicated speed relates to "at the stall". Nev

u guys are good!!! I just made a phone call to my cfi and mentour(whome is out of range for 6 weeks) and by fluke he got reception..He said as the pito is undernieth wing(low wing) itll have some crap in it .so ill blow it out..now balance issues ..he said its time to go all old school on its ass...lol..time to use the hanger as a hanger and hang the plane with a sling set at c of g and see if she is truly balanced?thatll elimanate my mathimatical calculations,wow that was some big words,pitty about the spelling..lol

 

 

[flyerme]

damn,how do i hang from c of g on a low winger?thinking 2 slings under each wing against fuselarge and a pole threw them above cockpit and block and tackle attacheed to centre of ploe,pole will sit at c og g,,that make sence?

 

 

[Guest Maj Millard]

 

You'll have to include about 3/4 fuel and yourself to get an accurate static CG by hanging, that's the hard part, getting everything set up and finally climbing in yourself. You can of course substitute weight for the pilot, but the hang must be done as it would be flown, for an accurate static balance.

 

I did a hanging static CG originally when I built my biplane, and had no dramas with CG in flight at all.

 

The GC of the aircraft (flying) must always remain just fwd of the wing center of pressure which moves back and forth as the wing AOA changes. On some airfoil types the center of pressure moves more than others. At the high AOA at the stall point the center of pressure has moved foward to it's furthest point, this is where the COG needs to be ahead of it to ensure the nose drops through.....................................................Maj...

 

 

[flyerme]

[ATTACH=full]17338[/ATTACH]You'll have to include about 3/4 fuel and yourself to get an accurate static CG by hanging, that's the hard part, getting everything set up and finally climbing in yourself. You can of course substitute weight for the pilot, but the hang must be done as it would be flown, for an accurate static balance.

 

I did a hanging static CG originally when I built my biplane, and had no dramas with CG in flight at all.

 

The GC of the aircraft (flying) must always remain just fwd of the wing center of pressure which moves back and forth as the wing AOA changes. On some airfoil types the center of pressure moves more than others. At the high AOA at the stall point the center of pressure has moved foward to it's furthest point, this is where the COG needs to be ahead of it to ensure the nose drops through.....................................................Maj...

Hey Maj,how did you hang it?I mean where and how did you fit a sling etc..P.S love the lil bipe,is that a brs on top?

 

 

[Guest Maj Millard]

Well the bipe was easy to hang, there were gaps at the wing roots and I passed a rope down between each wing, and under the fuselage. It doesn't need to hang too high just a few inches above the floor.

 

Don't know how you would hang a Supercat as chances are your static CG will be around the wing somewhere.

 

Final fine adjustment is often done with battery location, or pilot seat adjustments.

 

Strange thing was, as I had mine hanging a local aircraft restorer came in who restored Stearmans and Wacos etc. He was amazed and impressed I was doing it that way, but it sure did work, as the bipe flew just fine.........................................................Maj...

 

 

[Deskpilot]

Flyme, don't hang it............jack it up whilst resting on a narrow beam. Just move the beam back or forward till balance is achieved.

 

 

[djpacro]

Flyerme, if you like to send me the data you have I will crunch the numbers for you, a lot easier than physical determination of cg. Send me a private message to get my email. I'll probably ask for a few more measurements.

 

 

[flyerme]

Hey Doug,how do you mean? a beam running undernieth parrallel with wings in line with c.og g( in line with wing spar)? how thick a beam ? Thanx

 

 

[flyerme]

Flyerme, if you like to send me the data you have I will crunch the numbers for you, a lot easier than physical determination of cg. Send me a private message to get my email. I'll probably ask for a few more measurements.

Hi djpacro, that would be awesome..

wieght in kgs with 1/2 fuel and NO pilot measurments in inches

 

tail wheel = 21kgs DATUM taken from front of prop

 

r/h main wheel = 93kgs from prop to centre main wheels = 47"

 

l/h main wheel = 88kgs from prop to centre tail wheel =162"

 

from prop to pilot =85"

 

from prop to leading edge =50"

 

pilot wieght = 70kgs

 

c of g for supercat =datum from prop to c of g = max forward =62"

 

max aft =66"

 

optimum c.g=64.3"

 

c of g for supercat =Datum from leading edge =max forward =12"

 

max aft =16"

 

optimum c.g =14.3"

 

 

 

[Guest pookemon]

I make the CofG to be at 65.7" from the prop based on the above (but, bear in mind, I haven't really done much in the way of CofG calc's - I've only done it on my BAK - See the table below for my Calcs). That would put the CofG right at the rear of your limits. Where's the battery located in the SuperCat? Whatever you do, don't gain any weight!

 

Item Dist (Inch) Dist mm Weight Arm (inch) (D*W) Arm(mm) (D*W)

 

Tail wheel 162 4114.8 21 3402 86410.8

 

RH Main 47 1193.8 93 4371 111023.4

 

LH Main 47 1193.8 88 4136 105054.4

 

Pilot 85 2159 70 5950 151130

 

Totals 272 17859 453618.6

 

 

CofG 65.7 1667.715

 

 

[Guest pookemon]

Grrr - the table hasn't quite worked...

 

You can download the spreadsheet from here