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tailplane balance

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riddon(at)sent.com
Guest

Posted: Mon Jun 25, 2007 2:37 pm Post subject: tailplane balance

At the expense of showing my ignorance, why is the tailplane balanced as

it is? i.e. with the pivot point well forward of the c of g which

necessitates a balancing weight. Could it not have been designed with

the pivot point at the position of the c of g so no weight would be

needed?



Richard Iddon G-RIXS

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grahamsingleton(at)btinte
Guest

Posted: Mon Jun 25, 2007 3:13 pm Post subject: tailplane balance

That's for aerodynamic reasons, in the early days the pivot was moved 

about a bit to avoid "short period oscillation" and the present position 

was perhaps the best compromise. The pivot needs to be in front of the 

centre of pressure, which can move about a bit. Symetrical sections tend 

not to have moving Cp but maybe it does move a bit.

Graham



Richard Iddon wrote:

 	  Quote: 	
		   

 

 At the expense of showing my ignorance, why is the tailplane balanced as

 it is? i.e. with the pivot point well forward of the c of g which

 necessitates a balancing weight. Could it not have been designed with

 the pivot point at the position of the c of g so no weight would be

 needed?

 

 Richard Iddon G-RIXS

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davidjoyce(at)doctors.org
Guest

Posted: Tue Jun 26, 2007 12:33 am Post subject: tailplane balance

Richard, It is critical that the centre of lift or pressure is on the axis

or behind it for an all moving tail plane. If it is in front then any

increase in incidence immediately produces a force trying to further

increase that incidence. Such a system is highly unstable and would try to

snatch the stick out of your hand! If it succeeds disaster inevitably

follows.

Regards, David Joyce, G-XSDJ

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tonywickens(at)btconnect.
Guest

Posted: Tue Jun 26, 2007 4:36 am Post subject: Tailplane Balance

I am not moved to write often but just to add my two cents worth. Almost  everything we are saying is based on supposition regarding, in particular, the  tragic accident to Williams Europa. There has naturally been much speculation,  particularly after the early mention of flutter as a possible cause. As with all  accidents there were probably a number of mutually divergent occurancies which led to the eventual  loss of control but I am waiting for the AAIB to give their findings as it would  appear that a preliminary report is imminent. 

<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office" />  

Making reference to comments in recent e-mails 

  

If the tailplane balance weights were placed in the leading edge of each  tailplane you would end up with about four times the weight of the present  TP19’s (200mm arm as opposed to the 800mm at present). I don’t have access to  the TP19’s at the moment but they are heavy and four times heavy is very heavy,  and this would obviously be undesirable in weight and C of G terms. However it  is probably correct that the mono is slightly more prone to shock loading at the  pin securing the TP12. Although the ‘system’ is balanced, the tailplane is  itself tail heavy, and on landing and over rough ground this couple is resisted  mainly by the TP12 pins. A similar situation occurs of course with the balance  weight arm at TP9 and its two pins TP14C. Pronounced pitching on the close  coupled Trike gear on a rough surface would cause similar forces. Taxi-ing at  slower speeds is desireable for this and many other reasons. 

  

All design is a compromise but obviously if the balance weights were in  the leading edge of the tailplane then it would avoid the above situation and  each tailplane would be individually balanced as the ailerons are on the Europa.  I suspect that in the original design this option was discarded in the interests  of weight saving, and bearing in mind the arm length, from a weight and balance  point of view. 

  

I  think there is a lot of truth in what you are hinting at. Us trigear 

jockeys  are having to pay dearly for shortcomings in the  mono. 

  

I don’t think comments such as those above are very  helpful. All design is a compromise and the Europa was designed around a unique  set of operational objectives which is why so many of us bought Europa kits. It  is different to other taildraggers and requires slight modifications to standard  taildragger technique as does the Pitts Special and some other more demanding  aircraft. It is the only kit to have multi configuration which allows people to  make a personal choice depending on their preferences. As I said at the  beginning lets wait for the results of the investigation before jumping to  dubious judgments.    

  

Tony

   [quote][b]

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DuaneFamly(at)aol.com
Guest

Posted: Tue Jun 26, 2007 7:59 am Post subject: Tailplane Balance

In a message dated 6/26/2007 5:37:08 A.M. Pacific Daylight Time,  tonywickens(at)btconnect.com writes:

  	  Quote: 	
		  It is different to other taildraggers and requires slight modifications    to standard taildragger technique as does the Pitts Special and some other    more demanding aircraft. 	


 

 Good Day Tony,

  

 If you have specific knowledge with regard to the Europa I would appreciate  it if you could elaborate on this sentence. I have flown only Citabrias for my  tailwheel transition and am building my Europa with a conventional setup. I was  just wondering what adjustments I might have to make.

  

 Thanks in advance.

  

 Mike Duane  A207A

Redding, California

XS Conventional Gear

Jabiru 3300  

Sensenich R64Z N

Ground Adjustable Prop



See what's free at AOL.com. 

  [quote][b]

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tonywickens(at)btconnect.
Guest

Posted: Tue Jun 26, 2007 11:39 am Post subject: Tailplane Balance

Hi Mike

 I was only referring to the Pitts as an aircraft that required just a  little more training for anyone new to the type as does the Europa. I am  personally not familiar with the Citabria although from what I have read that  experience will be more than adequate. In the UK the PFA instituted a coaching  scheme where experienced pilots are cleared to give conversion training on  specific aircraft. This has worked well over here and I believe is very popular  with the insurance companies. In fact I think they make such training a  condition of cover. I am still building but also have a share in a monowheel and  had conversion training as mentioned above. The airplane is a delight to fly but  a bit more demanding on landing. I found the most difficult thing to get used to  was the power and sensitivity of the elevator after other taildragers that I  have flown. Having said that it is not difficult to get used to and of course it  is vital to use the rudder to keep straight until the aircraft stops as is the  case with all taildraggers. Hard runways are a little more testing than grass in  terms of keeping straight but again this is not too demanding. I agree with the  people who wisely advise to limit the cross winds building up your personal  limits gradually, particularly on hard runways. Take offs are easy, holding  the tail on the ground until aerodynamic aileron control is established. It is  IMNSHO the best handling kit aircraft and a delight to fly and tour in. Like all  aircraft types one needs to fully understand them, and as the late Tommy  Sopwith so aptly put it "make friends with them". Best advice I would give is  find a good coach or instructor but one experienced on the Europa and spend a  few hours, four or five is not too many, until you feel comfortable with the  aircraft and then very slowly expand your own envelope. The level of coach over  here is very high, in fact the person that converted me was a Royal Air  Force test pilot and is now a test pilot with Airbus, although they come from  all backgrounds and I am sure there are many such people in California. I would  think Kim Prout would be an excellent source of knowledge although California is  very big and he may not live close to you. I should add that I am not a  professional pilot, I am a professional engineer, now retired but I have been  flying taildraggers mainly since 1959 with a beak of about 20 years when I  couldn't afford to rent airplanes. So if I can fly the Europa I am sure anyone  can.

 Regards

 Tony 

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