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TamJets A-4 problem tucking issue

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Old 11-16-2009, 12:04 PM
  #1
76Phantom
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Default TamJets A-4 problem tucking issue

I have an A-4 setup according to Tams instructions. It is powered by a Jetcat P-70 and weighs in at about 20lbs. The problem I'm having is when you fly it at anything other then 3/4 power and make a turn it wants to tuck in hard on the turns. I have balanced it on the front main wing tube according to the instructions for the first flight and it was tucking in hard on all turns. I almost lost it a few times during the first flight. I moved the CG back about 1/2 inch to the front wing former and flew it a second time. It got a little better but it still tucks hard in turns and I’m afraid that at some point I will not be able to recover it if flying at lower altitudes. Does anyone have any suggestions and on what the problem might be or how far back you can move the CG?
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Old 11-16-2009, 12:18 PM
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Default RE: TamJets A-4 problem tucking issue

Classic A-4 handling characteristic. Pull just hard enough but not to hard. You have to respect an A-4. Keep it in its performance envelope and an A-4 is a wonderful, easy jet to fly.
Push it outside of that envelope and it can bite.....sometimes disastrously. This has been the same for every A-4 I have built and flown. I built over 8 different A-4 models from Yellow, Byron, JHH and Tamjets.
I have 82 flight on mine now. Great jet but I get bit every once and awhile. Usually when switching back and fourth between models. It's easy to forget to respect it. Not a scratch on mine. I love flying this jet…it’s a challenge……defiantly not a Boomerang!!
Dom
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Old 11-16-2009, 12:19 PM
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Default RE: TamJets A-4 problem tucking issue

Don`t fly it slow unless the wings are level. Really nothing you can do about it, just power in the turns and ease up only when straight and level. I had a turned up P-60 in mine, the issue with the jet is not more power but just lighter flying weight.
V..
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Old 11-16-2009, 12:40 PM
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Default RE: TamJets A-4 problem tucking issue

Thanks you guys. I have flown many A-4's in the past an they are nothing like this one. In the final apporach it makes for faster landing speeds because I really cannot slow it down before the last turn for the landing even with crow and full flaps down.
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Old 11-16-2009, 12:45 PM
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Default RE: TamJets A-4 problem tucking issue

I suspect the weight is a problem. 20# is a lot for Tam's A4. The plane has been designed for a P60. I sold mine but if I remember properly it was more like 17#. It did tuck in every once in a while, but it was because I was too heavy on the elevator.

Arnaud
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Old 11-16-2009, 01:16 PM
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Default RE: TamJets A-4 problem tucking issue


Quote:
ORIGINAL: acw

I suspect the weight is a problem. 20# is a lot for Tam's A4. The plane has been designed for a P60. I sold mine but if I remember properly it was more like 17#. It did tuck in every once in a while, but it was because I was too heavy on the elevator.

Arnaud
I agree with Arnaud completely.
V..
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Old 11-16-2009, 02:44 PM
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Default RE: TamJets A-4 problem tucking issue

76,

Who are you? I notice you're in CV. Where do you fly your jets? Nice to see another guy in SD...
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Old 11-16-2009, 04:16 PM
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Default RE: TamJets A-4 problem tucking issue

My name is Troy Kauk. I fly donwn at the Chula Vista field. I fly the larger jets at Mirmar. I have been flying my Jetlegend F-16 1/8 and my TamJets 1/12 down here at the CV field.
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Old 11-16-2009, 05:42 PM
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Default RE: TamJets A-4 problem tucking issue

Quote:
ORIGINAL: acw

I suspect the weight is a problem. 20# is a lot for Tam's A4. The plane has been designed for a P60. I sold mine but if I remember properly it was more like 17#. It did tuck in every once in a while, but it was because I was too heavy on the elevator.

Arnaud
I buddy boxed with Arnaud, once, and I saw this little A-4 do a serious tuck of death that I thought for sure meant death. I only buddy boxed ONCE.

Arnaud did end up flying the crappola outta his a-4 so I'm sure he figured it out.

Raf
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Old 11-18-2009, 11:05 AM
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Default RE: TamJets A-4 problem tucking issue

With the delta type wing a very large percent of the lift is generated by the inboard part of the wing. With the large intakes blanking out that part of the wing during a turn the low wing will have less lift and the plane will tend to increase the roll. The fix on the full=scale was automatic leading edge deployment to compensate. Neither balance nor weight will correct the problem.
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Old 11-18-2009, 12:41 PM
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Default RE: TamJets A-4 problem tucking issue

oups
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Old 11-18-2009, 12:48 PM
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Default RE: TamJets A-4 problem tucking issue

The A-4 also had a row of vortex generators at about the highpoint of the wing's airfoil to help flow retention at higher angles of attack.
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Old 11-18-2009, 01:37 PM
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Default RE: TamJets A-4 problem tucking issue

I think the the leading edge slats deployed more as a function of airspeed amigo. can't remember exactly but i do remember if they deployed asymmetrically you would be in for a helluva ride until they both deployed.

IRT the Tam A4, I would fly her again but not pull as tightly in the turns and see if that helps. float the turn and try to maintain as much energy at the completion of the turn as you began with.

if it doesn't then i would move the CG back a little bit more and try again. highly recommend being as smooth as possible when putting any G on the bird especially horizontally.

additionally, try taking her into a 1/2 loop and as you get near the top increase the G and see what happens. it might depart on you but the question you have to ask is when does it depart controlled flight? at the onset of increased elevator throw or somewhere nearer the last bit of elevator throw? if it does depart then relax the controls, allow the airspeed to increase while going wings level and then slowly add in elevator to fly out of the maneuver. once you get the hang of it she'll tumble with great enthusiasm

ultimately, the key to A4 is being smoooooooooovvvvvvveeeee

good luck but i'd venture to guess you're probably fine. Andy Wurner is flying one with a P70 at Miramar, maybe talk to him about his experiences.

cheers
buck

Quote:
ORIGINAL: Don Y

With the delta type wing a very large percent of the lift is generated by the inboard part of the wing. With the large intakes blanking out that part of the wing during a turn the low wing will have less lift and the plane will tend to increase the roll. The fix on the full=scale was automatic leading edge deployment to compensate. Neither balance nor weight will correct the problem.
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Old 11-18-2009, 01:38 PM
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Default RE: TamJets A-4 problem tucking issue

I have owned 3 Y/A A-4`s and they were "snappy" as well. A few years back i owned an Air Champ A-4, its was bigger than anything else out there at the time. Maybe 55" wing with 85" L fuse, it handled very nice with no bad habits. The wing "may" have been slightly larger than scale but not sure. All i know is it was a real sweet flyer and landed slow with full flaps.
I had 130 or so flights on my Tams A-4 and was carefull not to get slow in the turns, power all the way thru. Like i have said, only slow down when the wings are level and you will have fun with this jet. I can recall on one flight one of my mains was stuck in the up position. I tried to do a quick pull up to get the one gear down, it worked but the jet snapped and rolled over on its back in a spilt second!!! I righted it and came in with my knees shaking...
V..
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Old 11-18-2009, 02:34 PM
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Default RE: TamJets A-4 problem tucking issue

Almost sounds like you are discribing the flight charateristics of the F4 too. Mine likes to tuck on turns.
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Old 11-18-2009, 07:40 PM
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Default RE: TamJets A-4 problem tucking issue

move the CG back amigo. i've got barely 9 oz up front


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ORIGINAL: AndyAndrews

Almost sounds like you are discribing the flight charateristics of the F4 too. Mine likes to tuck on turns.
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Old 11-18-2009, 07:43 PM
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Default RE: TamJets A-4 problem tucking issue


Quote:
ORIGINAL: yeahbaby

move the CG back amigo. i've got barely 9 oz up front


Quote:
ORIGINAL: AndyAndrews

Almost sounds like you are discribing the flight charateristics of the F4 too. Mine likes to tuck on turns.
I'll try that, Thanks buddy.
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Old 11-19-2009, 11:23 PM
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Default RE: TamJets A-4 problem tucking issue

Buck,

It's been way too long for me, but if I remember correctly the slats deployed as a function of AOA. You COULD use their position on approach to judge your AOA/airspeed if you lost either; half travel of the slats was on-speed. The Blues bolted the slats shut to prevent the uncertainties and gyrations associated with slat deployment, especially assymetrical slat deployment.

I have to agree that lighter weight/wing loading will help. Keep the power on in the turns and smooth control inputs. I got a few minutes on one of Tam's before I bought my kit and I thought it flew very well.

Tom
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Old 11-20-2009, 04:39 AM
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Default RE: TamJets A-4 problem tucking issue

sounds reasonable amigo. its been a few years.

the lighter the better, i think the light weight version with a wren 44 would be as good as it gets.
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Old 11-20-2009, 10:34 AM
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Default RE: TamJets A-4 problem tucking issue


Quote:
ORIGINAL: 76Phantom

Thanks you guys. I have flown many A-4's in the past an they are nothing like this one. In the final apporach it makes for faster landing speeds because I really cannot slow it down before the last turn for the landing even with crow and full flaps down.
I've flown a few different Tam A-4's and own one myself. The A-4's I've flown fly sweet as butter but like everyone says the turn to final and such should be a gradual turn, maybe 30 degrees of bank, and in a descent towards the runway like you'd see in full scale. Do you have crow mixed in with your ailerons? Are you sure your A-4 is just 20 pounds? The CG position, crow setup and weight are the big three on initial thoughts. Also, re-check that your lateral balance - side to side - is reasonable and you don't have an undetected heavy side that you are making up for with aileron and then getting a snap stall as a result of the lowered aileron at high angles of attack. Best of luck in getting your A-4 all settled in and flying the way you like. When it's all dialed in it's sweet!
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Old 11-20-2009, 12:24 PM
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Default RE: TamJets A-4 problem tucking issue

i had two of the TamJet A-4s, both P-70 powered. my gray one was 19.5 lbs and flew great, the white was the light weight version and 18 lbs, it dug in hard in the turns even at full power/speed, took a 1/2 mile to turn around without dropping 300' of altitude in the turns problem turned out to be too aft a CG.
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