TARMAC



The Official News Letter

Of The










August 2001


Your Executive Officers
El Presidente Andrew Parr 479 3235
Vice El Presidente Chris Todd 833 5841
Secretary Martin Seay 525 6505
Treasurer Peter Cole 473 0130
Committee Anton Lawrence 813 6404
Committee Willie Morton 025 901 796
Chief Flying Officer Willie Morton 025 901 796
Safety Officer Niol Lockington 817 5959
PPAB Peter Nicholson 625 4010
PPAB Gordon Swan 827 5089
PPAB Vern Booth 360 4016
Editor Anton Lawrence 813 6404


Web copy of TARMAC

Official ARMAC Web Site

Next Club Meeting, 3rd Tuesday of the month.
August 21st

At the Pikes Point Airpark Clubrooms 19:00

Committee Meeting at 18:30 Sharp.

Editorial
Jon Farmer reports that the Ports of Auckland have refused to sell Pikes point to the Auckland Parks and Recreation board. So the status Quo will prevail for the foreseeable future.
Niol will talk about ARMAC's SAFETY POLICY & MANUAL, following ARMAC sending him to a CAA SAFETY COORDINATOR'S COURSE on Aug 6 & 7. He will present a brief outline of the course, explaining why as a group we must pay more attention to safety. He will discuss the benefits if we do and ramifications if we don't. He will present an outline of what we could expect to achieve in the next year and proposals on how to do it. Niol says it won't be difficult, already most of us are just about there, it simply requires a system to enable us to collectively raise the level a couple of notches, which will make our operations safer and save some money too.

Anton Lawrence



Anyone interested in some GA flights contact Ross Glover 576 6884






Prez Sez

Well this month's not been so good with the weather, general speaking it's been great during the week and not great for the weekend this in turn becomes even more frustrating when I can see microlights operating while I 'm stuck in the office, maybe week day operations should be suspended! Clearly identified offenders here are Vern, Warwick and Bob Melse.
This month the microlight fraternity has suffered a tragic accident in the Waikato resulting in the loss of a life. On behalf of ARMAC our sympathies are extended to the families involved.
I feel that this would be a timely reminder to remind everybody that there safety is paramount and should not be compromised in any way. Niol is doing a safety presentation at club night this month after attending a safety seminar and we would like to see a good turn out for this.
A reminder to people that if you are witness to an incident, please DO NOT make comment to the media but direct them to someone in authority.
We are also looking for cost cutting ideas, so if you have some, please let the committee know and we are also looking for more articles for this newsletter so please forward to Anton.

Andrew





The Northland Fly in
By Anton Lawrence

The fly in at Logan's was well publicised and so many planes were expected.
I arrived by car at 08:00 and it was still very cold. Some hardy souls who had arrived the day before were scraping the ice off their wings prior to the first flight of the day. I very slowly rigged up the Raven, which was kept in Logan's hanger. Logan pushed the Tecnam out of the hanger and was instantly ready for flying. He handed me his cell phone and was off. A number of pilots from south of the Bombay's phoned in his absence to say they were fogged in and would be unable to make it.
None the les about 20 to 25 planes turned up, including three Tecnams, two Cessna 180's, two Trike's, more Bantams than you could shake a stick at plus several other aircraft of various makes and models.
Alex McNab was seen to do about 500 take off and landings in his latest Bantam, very proud was he. Steve Roda had the fan on his 503 come lose but was able to get down before the pistons out grew the cylinders.
Giovani had supplied a small tanker for fuel, which he and Logan proceeded to use up as fast as they could taking all and sundry for rides.
If this effort didn't convert several to the faith then nothing will.
Lunch was more a feast and for the price of $7.00 was by far the best value in town, with soup and sausages and pie and cake, tummies were soon full and warmed ready for more flying.
Denis Smith and I went for I fly out to the west coast and back on the Raven but the wind had picked form the north just a little bit but it made the cast nice and bumpy, I don't think Denis liked that as he was quick to point back to Logan's.
After lunch I towed Geoff Green in his Hang Glider up to 4000' in Guntrum's Wizard trike. It was very cold at this height but also very smooth. It took Geoff about 15mins to get down.
We did another tow, which demonstrated the week link. But it would have been better if it wasn't over the power lines, (22,000 volts), fortunately the rope fell between them and was easily recovered, the pilot made it safely back to the strip. Discretion became the better part of valour and so that part of the show was curtailed.
There was a dinner held at the local pub, but a previous engagement meant that I was unable to attend, by all accounts it was a great night out.
The next day proved to be quite windy and so the flying was finished early and a planed fly in to Kiapara flats was abandoned. This was not before Allex and I had a quick fly around the block in his Bantam.
There was a lot of other flying done on the Saturday by many other pilots but I was doing so much myself it was hard to keep up.
This is the second year Logan has organised a fly in and I'm sure it will not be the last. So if you missed out this year then you should book in for next year.
Thanks Logan for a fantastic weekend.





Why Rectangular Wings Are Best
Anton Lawrence

We have often heard how the elliptical wing is the most efficient plan form for an aircraft wing; the Spitfire is often given as an example. The reason for this is often not given so I will tell all. The elliptical wing, if untwisted has an elliptical lift distribution. This is because at every span wise station along the wing the lift coefficient is the same, but as the cord gets smaller as we approach the tip so does the lift at each span wise station. At the tip the lift is virtually zero. If the lift-coefficients along the wing are the same then the down wash will also be the same along the entire wing. It is the down wash that is responsible for the tip vortices; if the down wash is the same along the entire wing then the tip vortices and by definition the induced drag will be at a minimum.
There are two fundamental problems with this.
As the wing approaches the stall it will become obvious that the entire wing will stall simultaneously, not a good situation.
But to add to this, as the wing cord gets smaller so does the Reynolds number (The ratio of air speed x the cord, to the air viscosity). As the Reynolds number of a wing section gets smaller so does the maximum possible lift coefficient. That is to say a smaller cord wing travelling at the same air speed as a wider cord wing will stall at a lower angle of attack. Worse still!!
These combine to produce a wing that stalls at the tip before the root, so for our purposes makes an elliptical wing of only theoretical importance.
On the other hand if we have a wing of constant cord then the lift coefficients along the wing will not be constant, they will in fact reduce towards the tip. The Reynolds number factor will have no part to play.
As the wing approaches the stall the inner section will stall first, this is good. To give an extra margin of safety the wing can have a small amount of twist built in. That is less angle of attack at the tip. This type of configuration will be extremely safe. Of course the down wash will not be consistent and so the induced drag will be higher. Induced drag is at its worst at high lift coefficients or slow speeds. At cruise speeds it is not such a problem.
So a rectangular wing can be safe, have reasonable performance and be very easy and cheep to build.
Of course one could spend a lot of time and effort into designing a wing that has an elliptical lift distribution at a specified angle of attack. This would be done by combining taper and twist in just the right combination, a la a sailplane.



Comparison of a double taper wing to a rectangular wing at an angle of attack of 10 degrees.
cl= Section lift coefficient.
CL=Configuration lift coefficient
P=Air density
V=Free stream velocity
C=Section cord
S=Wing area
l=Section lift
L=Configuration lift
Y= Span wise station from root (starboard wing only)
Note that Section lift is defined as l=cl ½ pV²C and Configuration Lift
L=CL ½ pV² S



Double taper (close to elliptic) wing lift distribution



Double taper Lift coefficients.
Note how the cl's stay high all the way to the tip.




Rectangular wing lift distribution.




Rectangular wing lift coefficients.
The cl's drop off nicely towards the tip.




Trade And Exchange.
Private owners only
Contact the Editor to place an add
813 6404hm 025 354 998wk
kirstant@orcon.co.nz

Trike, FXN, current air cert, plenty of instruments, long range tank, rainbow wing a pleasure to fly, low engine hours, $3,800.00 neg contact Alex; 09 5366815 h or 09 5342190 e-mail atocollision@paridice.co.nz

Koenig  "Pagojer" 18 Hp 3 Cyl radial engine, with prop, cage, and  harness for powered 'chute. In good condition, reconditioned a few hours ago. $2000. Further details from:  BRODIE ANDREWS, ph. 8175433"

Warpdrive three blade 58"-60" left hand ground adjustable prop. Older type with two sets of hub plates to suit either standard Rotax 75mm or 4" bolt pattern for VW or Subaru. Moulded-in metal leading edge protection.
Never been used. $900 Contact Jon Farmer, ph (09) 520 0641

Icom A22 handheld radio, 760 com: channels plus VOR navigation readout. Alkaline battery pack. Brand new in box $950
Contact Jon Farmer, ph (09) 520 0641

Two quality Peltor headsets, intercom with cables for connection to Icom radio and push to talk switch. All new. $650 the lot or I can fit the headsets with standard GA plugs and sell them separately. Contact Jon Farmer, ph (09) 520 0641

Intercom, with connoectiions to radio $200 Contact Jon Farmer, ph (09) 520 0641

Helmets with clip on peak and Peltor earmuffs. Fully adjustable for size. Wear a beanie underneath in cold weather. Either red or blue. $180
I can customise these helmets with speakers and microphone to suit your requirements. Contact Jon Farmer, ph (09) 520 0641

Dac and ¼ share of Hanger No.3 at Pikes Point.
Dac has only 5 ½ hours airtime, recovery chute and many extras.
Make an offer for aircraft and hanger together or separately, but aircraft must be sold before hanger goes separately. Contact Brian Mcleod, 351 Weber Rd, RD1 Dannevirk 5491. Ph 06 374 6635.