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TOPIC: Twin Wing Centre of Cravity and Centre of Pressure

Twin Wing Centre of Cravity and Centre of Pressure 5 years 1 month ago #1527

  • AlanThomas
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I think we can all agree that the twin wing configuration is considerably different to a standard mono plane in as much as the "Centre of Pressure" is shared between two wings which in the Quickie type is around 60%/40% between canard and main wing of which is considerably manipulated in relation to the "Centre of Gravity" by control services such as canard reflects and T-Tail whereas a mono is far more simplistic whereby the centre of pressure is almost static its relationship with the centre of gravity.

This fundamental difference appears to have developed vastly different viewpoints as how to correctly pilot a quickie resulting in much discussion about modification to this type in order to do need the operational expectations which have been significantly coloured by monoplane flight training. As a newly acquainted Quickie owner I am somewhat disconcerted at the situation where so many people are so far apart on the rather unique avionic characteristics. It would seem to me that most people have fallen into what is usual and comfortable as to how things should be. Of course almost 100 years ago this would not been an issue because everything was extremely different.

In New Zealand there are about 5 Q1s and about 6 Q2s with a few dragonflies. Auckland which has a third of the New Zealand population, where I live, has none until I purchased my Q2. The problem I'm experiencing getting started is that only the local instructor to get type rated before my fun of learning can begin. We are noticing the variations and inconsistencies amongst not only New Zealand Quickie pilots but othersoffshore. The manufacturer's pilot manual only go so far.

Any suggestions???
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Twin Wing Centre of Cravity and Centre of Pressure 5 years 1 month ago #1530

  • F3A-1
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WHAT?!!!!!!!!

Do a weight and balance per the pilots manual, a preflight, and push the throttle forward!

If you know you are not able to fly it don't try to make it more complicated than it is, just sell it. Bi wing or not it is JUST AN AIRPLANE. I don't mean to be crass. The Q-2's are not bad airplanes! Follow the pilots manual and keep the plane in good working order and you will find it flies more like a regular "AIRPLANE" than you would think.


Best of luck with you bird,
Lex
An ego is no match for gravity.
Last Edit: 5 years 1 month ago by F3A-1. Reason: I was less than polite
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Twin Wing Centre of Cravity and Centre of Pressure 5 years 1 month ago #1531

  • AlanThomas
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Lex thanks for your input. Unfortunately as I have described it does appear that many Quickie owners are finding this business of flying more complicated than it really is by not following the twin wing flying principles that certainly do not match up with a mono wing plane and as such are not getting the full performance available. I do not agree that it is just an aeroplane despite the fact that it certainly can be flown just like an aeroplane if that's what you want to do.

In addition since the original design there has been a number of additions which have been added for very good reasons. A small portion of quickie pilots have claimed better performance than others. This is not just attributable to just the build itself so that leaves the pilot configuring the various control surfaces. The original design ofcourse minimised these control surfaces. However with the introduction of bigger motors to go faster, air brakes to slow down, winglets, reflexes, T-Tails and go faster stripes et cetera the flight characteristics have changed quite a bit since the original flight manual. The reflexor can crank the ailerons into flaps for increased lift which unloads the canard elevator, also acting as flaps which kind of messes things up to slow flight can be restored by the T-Tail restoring the desired attitude and therefore achieving a slower speed still. This of course monkeys about with the fulcrum point between the canard and main wing centres of pressures which is an entirely different issue to the centre of gravity. I do not see this issue being discussed by anyone and I would very much like to hear from someone who comprehends these matters in order to tidy this area of piloting skills up in order that we will fly right.

While I note that the main focus has been on high speed and endurance there is very little on minimum speed which is very important for a country such as New Zealand who has a plethora of short runways.

The added interest of course is re-certifying quickies as ultralights (microlights) for many obvious benefits and as such I personally think it is worth our effort to squeeze every last drop of technology that already exists on these planes before doing anything radical.
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Twin Wing Centre of Cravity and Centre of Pressure 5 years 1 month ago #1532

  • F3A-1
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Alan,

Now that I have thought about this a little I will try to reply in a constructive manner.
Usually I have "time in type" before I offer someone advice on how to fly a specific airplane, or inform them they are flying the plane incorrectly. That said, I have short field (3000' sod) in a Q-2, which I was comfortable with, and some time in a Dragonfly from paved runways, and one landing on an Interstate Freeway. I have flown both at the ends of the envelop. I personally, would not choose to operate this type as a bush plane. I would use one of many types I have flown suited to the task. If you choose to operate your Q-2 in such manner you must be a great pilot.
I do not see an evolution of a Q-2 or Quickie into a short/rough field plane. I do not feel that minor changes in pilot technique will dramatically change the lower speed much. I personally have "ZERO" interest in changing the design.
Good luck to you and your plans to modify a Q-2 into a bush plane. I do not see a line of more than "1" forming to do so.

Fly safe,
Lex
An ego is no match for gravity.
Last Edit: 5 years 1 month ago by F3A-1.
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Twin Wing Centre of Cravity and Centre of Pressure 5 years 4 weeks ago #1533

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Thank you for your thoughts Lex and of course you are perfectly entitled to have zero interest in advancing the technology however I have noticed that the majority are enthusiasts wanted to know and achieve the full operational envelope of the aircraft is any good pilot would.

I raised this issue concerning the difference between the centre of gravity and the centre of pressure because of the unique situation these twin when aircraft present us with whereby there are a number of variables not normally encountered such a degree as a conventional aircraft. Of course the control surfaces directly affect the centre of pressure without affecting the centre of gravity. Quite a neat trick altering the 60%/40% wing loading pressure With the assistance of the main wing Reflexor generating a flaps lift effect combined with the T Tail leverage Restoring the pitch up attitude with the additional benefit of unloading the canard which can be gradually increased as speed is reduced.

It does seem, in theory, correctly configured, that 42 kn is achievable. Maybe the test pilot making the notes and my cue to log book did it right. However naturally I would like to have these figures replicated by someone with the appropriate level of skill so as they may pass that skill onto myself. The alternative will be a back to the drawing board situation hopefully with the help of those who are interested in broadening the horizons of the site.

The various add-ons seem to have explored the potential of the quickie series but i have noticed the lack of reliable documentation whereby some certainly need to straighten up and fly right. Obviously we don't want to be adding ballast and other forms of jiggery-pokery in the belief that two wrongs make a right. We know that technology has moved forward a great deal over the last 30 years and I'm sure some amongst us have joined this site to share their knowledge.

I joined this site to take advantage of an increased knowledge base and experience due to my lack of knowledge and experience. This does not in any way suggest i want to be a target for abuse.

There are very sound reasons to enable a Quickie to not only fly fast economically but also increase the levels of safety when landing and the typical New Zealand runway.

Achieving a microlight (ultralight) status for a Quickie enables an owner to not only service their own aircraft but it will also immediately increase its value.
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Twin Wing Centre of Cravity and Centre of Pressure 5 years 4 weeks ago #1534

  • F3A-1
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Alan,

Even if I have "ZERO" interest in making a Q type a bush plane, I have even less interest in abuse of a fellow Quickhead! For that perception I sincerely apologize to you and anyone else on this site who though so.


In the US an ultra lite is closer to a powered kite than a Q-2. I have flown them and I am not knocking them either. I suspect some of our lack of clear communication on my part is due to this. We may also have different ideas of what short strips are. As I said before, I felt comfortable with 3,000' of smooth sod,(at gross) in a Q-2 with clear approaches. If you are talking about less than 2,000' I would not be confident.

I do not intend to impede advances in this type of plane, I am just happy with it as is for myself. If you can improve the low end performance it would be good for those intending to do what you want to do. That is EXPERIMENTAL aviation, and I support that.

Regards,
Lex
An ego is no match for gravity.
Last Edit: 5 years 4 weeks ago by F3A-1.
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