flyerme

ITS EVEN NOW i REMOVED THE RUBBER STOP i PUT IN...it is now back to origanal and the trailing edge of elevator now moves an extra 3inches, so was just running out of stick..but the pitching I now believe is the trimming tabs which more than likely have been bent down more during tranport 3 weeks ago ,as I did have to bend 1 corner of the left elevator tab as it got bent/folded during transport.

anyone know anything about trimming tabs? what would happen on approach if a cessna left the trim up or down?

may have found the cause? any one know about trimming tabs? it has 2 small trimming tabs on elevatot trimed down..I guess to keep it hand free in level criuse? but what happens in approach? as these would still be pulling the nose down yeh? and to be clear the stall at landing was all my mistake with the rubber stop on the elevator..as we know the longer the arm the further the travell .. bloody goose.. im ashamed to say without the stop the elevator has a fair bit more travel at the trailing edge..any way back to trimming tabs,,ive never seen these prior the super cat.Note:at some stage it has been set up for long distance flying and has 409hrs on the clock,vhf,gps (arial and wiring),compass ,aviation thermometer,alt/qne/ etc...so it may be set up for long cruise with tabs and not set best for landings ?

ok found something causing my "running out on back stick",my bad I put a rubber stop because when full back the control arm hit the back wall and has rubbed a dent,any way removed it (a good 3 mill thick) and replaced with tyre tube cut out,but still doesnt explain needing 1/2-3/4 back stick as soon as she pitch's over? thinking about last flight it feels like not enough air flow over tail unless power applied, will test next chance to see if in level fight at 60 knotts with centre stick,if i back off power see if she will nose over,but already notice in level flight at 60 knotts stick is centred but on approach at 60knotts(less revs) she need 1/2=3/4 back pressure and if you throttle up(as the elevator already 3/4 up) she instantly gets more airflow and lifts,,im really thinking airflow?

OK just finished a static balance,and perfect!! with 1/2 fuel and 70kg pilot it sits level at 14.2" if moved to max aft 16" it balance's nose down slightly,set at 12"max forward and balance's slightly tail down.

NOT a c of g prob? any other ideas?

Hey Pud, you gettin it sorted? I had revs probs you may recall (NOT over heating though) after a re-pitch managed the factpry recomended static=6200rpm and cclimb is 6500rpm,good luck

make it from prop to erect penis tip 81"

sorry was a double post..appologies:augie:

Flyerme, that looks like a Powerfin prop you've got there...happy with it ?.....I've got 650 hours on mine now on the Lightwing and it's going fine....................................................Maj...[ATTACH=full]17360[/ATTACH]

fuel moment from prop to centre of tank is 37" 1/2 full=22ltrs full=45 litrs

pilot c.g was taken with me seated, measuered to my belly button from prop

Sorry, but that would explain fog on the inside, but not the outside.What creates fog, is warm moist air that is close to the dewpoint temperature for its level of humidity. Upon hitting cold air or a cold windscreen, the air in contact is cooled below the dewpoint and water condenses out as fog.

 

So you possible flew up into warm moist air that was just above its dewpoint. The solution, apart fromapplying anti-fogging agents, would be windscreen heating. If it were possible to vent some warm air from around the engine, up over the outside of the windscreen, that might alleviate the problem. ie. a demister on the outside.

 

If you have seen it on the Thruster too, then I suspect it isn't the aircraft per se, but rather the specific conditions that would appear to occur in your vicinity.

 

P.S. Now I'm on the PC, I've looked up the windscreen product I use and updated the previous post.

The original engine was not what advertised.it was worn inside lot of scores on both piston and bores,,replacement engine has genuine 47 hrs from new and still has factory machining criss cross marks on bore ,piston No scores and is slightly later made..that said it should be lighter in the front end but not by much as I have removed the add on exhaust(which some bright spark welded between the manifold and tuned exspansion chamber) also removed pullstart bell)thinking back to when I flew at purchace I really dont recall searching for more elevator.

must say from a pilots point of view it feels front heavy.Take off feels normal and balanced,level flight at cruise seems normal but the intant you back off revs she nose over and want to contiue noseing without 3/4 stick,now with revs set 60 kt level I pushed her forward and set approach angle and she still wanted to pitch forward asi now 70...? if not front heavy I would say tail plane,I spent 15 years designing and biulding R.C scale models and if it where a large model doing this and the balance was right I would 1.adjust tail plane (NOT a thrust line issue as it does it throttled back)and check for adequet air flow over them,2 exsteand the tail to main gap and re balance.but she aint a model and I cant stretch her..lol

What am I missing then...?Tail wheel : 162" x 21kg = 3402

 

RH Main : 47" x 93kg = 4371

 

LH Main : 47" x 88kg = 4136

 

Pilot : 85" x 70kg = 5950

 

Total Moment : 3402 + 4371 + 4136 + 5950 = 17859

 

Total Weight : 21 + 93 + 88 + 70 = 272

 

CofG : 17859 / 272 = ~65.7

 

Less Prop -> Leading Edge = (65.7 - 50) = 15.7" from leading edge with 1/2 fuel

What am I missing then...?Tail wheel : 162" x 21kg = 3402

 

RH Main : 47" x 93kg = 4371

 

LH Main : 47" x 88kg = 4136

 

Pilot : 85" x 70kg = 5950

 

Total Moment : 3402 + 4371 + 4136 + 5950 = 17859

 

Total Weight : 21 + 93 + 88 + 70 = 272

 

CofG : 17859 / 272 = ~65.7

 

Less Prop -> Leading Edge = (65.7 - 50) = 15.7" from leading edge with 1/2 fuel

just done a very rough balance on a beem with plane level and 70kgpilot.set beem(1 1/2" thick beam under fuselarge which is flat) at 14"(optimum cg) and it lifted the mains ? looking tail heavy? will move beem tomorrow to find at which point the tail lifts and find where current cg is sitting.

They really are a short coupled aeroplane aren't they? In the absence of a longer moment arm, would VGs below the horizontal stabiliser do the job? ( or fins ahead of the horiz stabilisers like fitted to some DH-82's. (Tiger Moths). Also what is the movement of the Cof G from full fuel to fuel empty, at max AUW on take-off ( corresponding to full fuel ). Nev.

allowable c of g = 12" to 16" ,,14.3" optimum

any ideas? nothing stand out?

pics

yes and the plane that had engine failure flying it home after 3 hours circut work.(earlier thread)

battery is behind pilot.

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.

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"

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

[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...

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?

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

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...