Mixed bag

Pula is Croatia’s worst performer this year
As October draws to a close, the Croatian ministry for sea, transport and infrastructure has published the country’s airport figures for the month of September. Although some airports are reporting good growth, Zagreb is yet to stage a recovery. Other airports which are worse off than last year are Split, Dubrovnik and Pula. Meanwhile, Zadar, Osijek and Rijeka are reporting growth.

Zagreb’s passenger figures in September fell by 6.8% when compared to the same month last year. The airport welcomed 198.364 passengers this September, compared to 212.735 last year. The airport is also reporting a substantial reduction in transit passengers, which fell by 81%. Split saw an 11.6% passenger decrease while 159.724 passengers passed through Dubrovnik, 14.296 passengers less than in September 2008. Pula Airport is reporting the greatest passenger decrease, continuing the negative trends which began a few months ago. The airport reported a 24.4% passenger decrease.

Osijek continues to report growth. In September the airport saw a 113% passenger increase, although this brings the number of passengers up to only 3.302 this September. Zadar saw 28.734 passengers, 51.6% passengers more than in September 2008. Rijeka saw a moderate increase of 5.6%.

So far, in the elapsed 9 months of the year, Pula has seen the greatest passenger decline of up to 20.9%. Osijek is reporting the greatest increase, of up to 34.7% while Zagreb has seen a 4.2% passenger decline this year. The bankruptcy of SkyEurope has had a significant effect on some airports in Croatia.

Passenger figures at Croatian airports:
· January
· February
· March
· April
· May
· June
· July
· August

50 States In An LSA!

At this summer's Oshkosh fly-in, I had the pleasure to meet an inspiring new pilot, Michael Combs, who briefed me on his plans to fly a Remos GX to every state in the US of A, beginning next spring.
Good news: Michael just finished his check ride - that's him below with his CFI, Justin Shelley of U.S. Flight Academy- and is now a happily licensed Sport Pilot. Congratulations Mike!
The odyssey flight will serve as more than just an adventurous lark, although that would certainly be enough motivation for most of us. The intrepid fledgling pilot - and a survivor of a serious illness - will make 135 stops during the inspirational mission, dubbed “Flight For The Human Spirit”, to champion what he recently described as "...proof of human capability and of accomplishing what you are able to dream."
He intends to demonstrate, in dramatic fashion, that “a Sport Pilot license is a passport to unlimited adventure...a celebration of freedom.
Mike estimates he'll have more than 100 flight hours under his belt by the time the 40-day trip launches. He'll have all the latest electronic nav gear, including XM weather and satellite tracking that will update his progress every two minutes, which you can follow on his website: www.flightforthehumanspirit.com.
---photo courtesy Remos Aircraft

Montenegro eyes Macedonia

Flying towards Macedonia
Recently Adria, Jat and Turkish Airlines have all been speculated to have an intention of setting up future flag carriers in Macedonia. The latest addition to this list is Montenegro Airlines.

Montenegro Airlines has sent in an offer to the Macedonian government for the creation of a joint new national carrier. The Macedonian government has not responded to Montenegro Airlines’ request but the Macedonian Civil Aviation Directorate (ACV) has said that Montenegro Airlines could set up services from Skopje as the two countries have a bilateral aviation agreement. The director of the ACV says that Montenegro Airlines could cover the market with 2 aircraft, but adds that the Macedonian government is not in favour of setting up a national flag carrier after the demise of MAT Macedonian Airlines which on September 1 lost its Air Operator Certificate (AOC).

It has been confirmed that Turkish Airlines is no longer interested in setting up an airline in Macedonia, although a Turkish company is hoping to set up Laluna Airlines. Monte Air which would be partly operated by Dubrovnik Airline is also planned, while Jat Airways plans to activate Aeromak, 11 years after it was registered.

Montenegro Airlines recently launched flights from Podgorica to Skopje.

Niš gets flights

Busy times ahead for Niš
Serbia’s third largest city, and second international airport, has received some good news as foreign airlines plan to begin scheduled flights from Constantine the Great Airport. After Jat Airways announced its withdrawal from the Niš – Zurich service (and Niš itself), Montenegro Airlines announced the inauguration of flights between Niš and the Swiss city on November 14. Flights from Podgorica to Niš will be launched a day earlier, on November 13. Flights will operate twice per week with the Fokker F100. Montenegro Airlines promises that it will introduce more flights from Niš in the near future.

Meanwhile, the Swedish airline MCA will begin its 3 weekly service from Stockholm to Niš starting Monday December 14. A round trip will set passengers back approximately 300 Euros. Media reports state that the city authorities are negotiating with the Italian Windjet to commence flights from Bologna by the end of the year. A private, yet to be named, Russian airline has also apparently requested a license to begin flights to Niš. The Serbian Civil Aviation Directorate has said that it now gives out licenses to any airline wishing to begin flights to Serbia.

As the “good times role”, Niš Constantine the Great Airport launched a new look website.

Do you think all of these flights are disasters waiting to happen or a potential financial goldmine? Send in your comment.

All flight details can be found on the right hand side in the “new route launches” section.

New Zealand connection at Temora

Two shots of ex NZ aircraft as seen at a recent Temora flying event by Andy Heap.
Vickers Supermarine 361 Spitfire MkXVI ZK-XVI , c/n CBAF 10985 , was built in 1945. It was damaged in 1951 and then served time with the MGM Pinewood Film Studio. Rescued from there to entered the UK civil register as G-CDAN on 30-11-1982. It was shipped to NZ in 1988 and became ZK-XVI on 17-01-1989 with the Alpine Deer Group at Wanaka. Sold and cancelled from our register on 26-05-2006 it went to Australia to become VH-XVI with Temora Aviation Museum on 17-07-06.
N.Z.A.I CT-4A Airtrainer ZK-EUW , c/n 074 , was registered here on 10-03-1982 to NZAI Ltd at Hamilton and was delivered to the RAAF on 07-05-1983 to became A19-074.
It was sold off in 1993 and became VH-APV to Smiths Trucks on 13-12-1993. Five owners later it is with Neil Newton of Medowie, NSW. As you can see,it still retains its RAAF colour scheme.

Question time # 75 resolved

The aircraft in question was Pipistrel Sinus 912 ZK-GPI , c/n 134SN9120204kit49 , as registered to Pipistrel Aircraft NZ Ltd of Kerikeri (Alan & Donna Clarke) since 10-11-2006.

A second aircraft ZK-GIM2 , c/n 129S9120104 is with Kester Holdings of Auckland.
All photographs kindly supplied by Andy Heap. Taken during a photo shoot over the Lyttelton Harbour.

And the winner is :-

Well :- an early Anonymous mentioned a "High performance glider wing". Afraid the Sinus is not [in my view] in the high performance class.

Henry almost got it with the type and gave us the two Sinus registrations. Shame about the 503 reference.

Wayne started off ok but then removed his comments.

And then - [by the hair of my chinie chin chin] - another Anonymous gives all the details required.

So feeling extra generous tonight :- If Henry & the final Anonymous would like to send their snail mail address to me at bluebus@windowslive.com I will flick a fish in your direction.

Skywings spreads its wings

Skopje – Brussels and a hotel

The Macedonian based Skywings International Airlines, which has taken over the bulk of MAT Macedonian Airlines’ passengers, has begun operating 2 weekly flights from Skopje to Brussels. The service, which was inaugurated on Monday, will also operate every Friday using the airline’s sole Boeing B737-300. A return ticket will set passengers back 300 Euros. The airline operates scheduled flights to Istanbul, Zurich and Dusseldorf and plans to add another Boeing B737-300 to its fleet this December.

The airline has also unveiled a 500.000 Euro investment in the construction of a hotel near Skopje's Alexander the Great Airport. The chairman of the Skywings board of directors, Ajan Dzaferoski, announced the ambitious plan on Monday, during the inaugural flight to Brussels. Dzaferoski stressed that the construction of the hotel is set to begin March next year. Construction work is scheduled to be completed by June 2010. The project envisages a 20 room hotel, which will also accommodate the crew of Skywings International. The airline's headquarters will also be based at the hotel.

The airline will inaugurate flights to Rome this Sunday and flights to Bergamo will begin on November 10. Bookings are only available via the tour operator Airlift Service.

Under watchful eyes

Jat’s B737-700 is expected in Belgrade in March 2010
In face of large scale competition, Jat is rapidly moving to change its old ways. The Serbian carrier has announced a network wide ticket sale, starting today, which will see ticket prices slashed to many European services. Also today, the airline has called on Belgrade taxi corporations to send in their best offers for the free transportation of Jat Airways passengers to and from Belgrade Nikola Tesla Airport. From January 1, 2010 all passengers travelling Jat will be able to hitch a ride to and from the airport for free with a certain taxi company in Belgrade (which will be chosen through this tender). Passengers will present their Jat ticket to the taxi driver and receive a free ride, within Belgrade.

It has also been revealed that Jat is directly negotiating with Boeing’s director of sales for Europe and Russia for the lease of a Boeing B737-700, scheduled to join the airline in March 2010. Jat has requested for Boeing to send in its offer for the lease. This could mean that the aircraft could be either brand new or up to 2 years old.

All of these measures are part of the airline’s 2010 plan, also dubbed the “recovery plan”. The Serbian government will, by Friday, set up a task group that will oversee how the recovery plan is progessing and whether Jat is meeting its deadlines and obligations. Jat’s management has repeatedly blamed Jat’s previous CEO, Saša Vlaisavljević, and his team for destroying many aspects of the airline. He, as well as many of his colleagues have either lost their jobs or been demoted.

Question time # 75 reviewed.

Alright then. try yet another clue ! [added Thursday 29th].
Yet another clue for you. [added Wednesday 28th Oct].
Does this help narrow it down in any way ?

An additional clue [above] shows another aspect of the same aeronautical device as the original pic below.
So we are still trying to establish what the original photo [above] shows.

Once we establish that - I then require the aircraft type and its NZ civil registration please.

Flap mechanisms for RC aircraft



You was able to see the polar of KS118 on the previous blog post. Here is the airfoil in question, it is very similar but slightly different from KS125.


Here is a wing simulation with this airfoil:

Comparison between NACA and KS118, 2D-simulation

KS118 Cl-alpha polar, including stall region at 1M, comparison with NACA23012 and 23015 included:

New airfoil KS125


Dat file in QFLR5 format:

Here are the polars:

Montenegro turns 15

Early years, Montenegro Airlines' Fokker 28Mk 4000
Montenegro’s national carrier has celebrated 15 years of existence over the weekend.

Montenegro Airlines was registered on October 24, 1994. The airline’s founder and CEO Zoran Djurišić presented the airline’s plans to the government of Montenegro and Yugoslavia in 1993. However, it wouldn’t be until 1996 that the airline’s first aircraft would be purchased. Due to political and economic circumstances at the time, Montenegro Airlines took off to the sky on May 7, 1997 on route from Podgoica to Bari in Italy. The aircraft in question was a Fokker 28Mk 4000 and the second aircraft of this type was received the following year in 1998. In late 1999, Montenegro Airlines launched new flights, most notably to Frankfurt. The first Fokker F100, the airline’s signature aircraft, was purchased in 2000. In 2007, the airline purchased new Embraer jets in another wave of fleet modernisation.

Today, the airline is a member of IATA and soon to become the newest member of the Association of European Airlines. Despite a difficult year for the aviation industry, Montenegro Airlines is not reporting strong growth but has evaded any losses, passenger wise. The airline’s CEO, although a very controversial figure, announced on Saturday that Montenegro Airlines is the pride of Montenegro.

On Friday, the airline received permits to begin services from Niš, in Serbia, to Podgorica and Zurich. Serbia is Montenegro Airlines’ largest and most important market.

Another Rangiora time spot. Monday 26-10-2009

The latest Cessna 180 - the 180D Skywagon ZK-BZP2 , c/n 18051050 captured at Rangiora about high noon today. I believe that today was also its first flight in ZK marks. Purchased in Australia and registered to Peter Turvey back on 25-05-2007 it was imported to NZ and seen in its VH-MDK marks earlier this year. In certain aviation circles Peter is known as "Zippy" hence the "ZP" registration. The aircraft is based at Forest Field.
Below a close up of the marking on the 180's tail.

Another fleeting visitor was the NOTAR ZK-HYY2 , c/n LN107 , of Garden of Eden Helicopters dropping in for fuel.

A moment in time. Rangiora. Saturday 24-10-2009

A lunch stop at Rangiora on Saturday the 24th October 2009 was well worth the deviation from track. Barry (Baz) Payne from the Wainono Homestead, Studholme Junction (near Waimate) popped in for a cuppa coffee in his Piper PA-24-250 Comanche ZK-BAZ2 , c/n 24-3206 . Hard to believe that this is a 1962 model still in its original factory colour scheme. It has about 1750 airframe hours and is based Timaru based.
Grant Porter's Avid Mk IV ZK-JHW , c/n 1434D , has been undergoing a bit by bit refurbishment. The fuselage is now overall silver.
Another out of town aircraft was this Murphy Rebel ZK-JQD , c/n 387 . This was an eleven year project by Peter Kempthorne which joined the register on 24-08-2004.
Neil S Ross of Gore has used his initial as the registration of his Tecnam P92 Eaglet U/L ZK-NSR2 , c/n 1128 . Up on a dual x/c exercise from Ashburton; grabbing some fuel; a "P" stop; and then away again to points south. Ruth Presland in the right hand seat.
The TRC Toyoto Cessna T210R Turbo Centurion ZK-TRO3 , c/n 64918 , from Feildiing passed through again.
Behold, another stranger. In Paul Woodley's hangar was this Aviate Raptor 582 ZK-WHG , c/n AR 0009.belonging to John Osmers of Takaka. This is a South African machine and was registered as ZU-AXH before coming to NZ.

19 years later...

They took their time
On May 1, 2010 scheduled air service between the capital of Croatia, Zagreb and the capital of Serbia, Belgrade will be resumed, almost a full 19 years since they were abruptly terminated. Croatia Airlines will be offering scheduled flights between the two capitals 4 times per using its regional Dash 8-Q400 aircraft. Flights will operate every Tuesday, Thursday, Saturday and Sunday. Flights between the two cities ended on August 6, 1991 when JAT Yugoslav Airlines operated its last Zagreb – Belgrade flight. Air travel between Croatia and Serbia was resumed in 2007 when Jat began flights to Pula. It is expected that after Pula and Zagreb, Dubrovnik will also be connected to Serbia’s capital.

Meanwhile, Croatia Airlines has also announced that it will be launching flights to Athens on April 29. Flights will operate 3 times per week, every Tuesday, Thursday and Sunday using the Airbus A319.

All flight details can be found on the right hand side in the “new route launches” section.

Vertical Stability (Yawing)

Stability about the aircraft’s vertical axis (the sideways moment) is called yawing or directional stability. Yawing or directional stability is the most easily achieved stability in aircraft design. The area of the vertical fin and the sides of the fuselage aft of the CG are the prime contributors which make the aircraft act like the well known weather vane or arrow, pointing its nose into the relative wind.

In examining a weather vane, it can be seen that if exactly the same amount of surface were exposed to the wind in front of the pivot point as behind it, the forces fore and aft would be in balance and little or no directional movement would result. Consequently, it is necessary to have a greater surface aft of the pivot point than forward of it.

Similarly, the aircraft designer must ensure positive directional stability by making the side surface greater aft than ahead of the CG. [Figure 4-27] To provide additional positive stability to that provided by the fuselage, a vertical fin is added. The fin acts similar to the feather on an arrow in maintaining straight flight. Like the weather vane and the arrow, the farther aft this fin is placed and the larger its size, the greater the aircraft’s directional stability.

If an aircraft is flying in a straight line, and a sideward gust of air gives the aircraft a slight rotation about its vertical axis (i.e. the right), the motion is retarded and stopped by the fin because while the aircraft is rotating to the right, the air is striking the left side of the fin at an angle. This causes pressure on the left side of the fin, which resists the turning motion and slows down the aircraft’s yaw. In doing so, it acts somewhat like the weather vane by turning the aircraft into the relative wind. The initial change in direction of the aircraft’s flightpath is generally slightly behind its change of heading. Therefore, after a slight yawing of the aircraft to the right, there is a brief moment when the aircraft is still moving along its original path, but its longitudinal axis is pointed slightly to the right.

The aircraft is then momentarily skidding sideways, and during that moment (since it is assumed that although the yawing motion has stopped, the excess pressure on the left side of the fin still persists) there is necessarily a tendency for the aircraft to be turned partially back to the left. That is, there is a momentary restoring tendency caused by the fin.
This restoring tendency is relatively slow in developing and ceases when the aircraft stops skidding. When it ceases, the aircraft is flying in a direction slightly different from the original direction. In other words, it will not return of its own accord to the original heading; the pilot must reestablish the initial heading.

A minor improvement of directional stability may be obtained through sweepback. Sweepback is incorporated in the design of the wing primarily to delay the onset of compressibility during high-speed flight. In lighter and slower aircraft, sweepback aids in locating the center of pressure in the correct relationship with the CG. A longitudinally stable aircraft is built with the center of pressure aft of the CG.

Of structural reasons, aircraft designers sometimes attach the wings to the fuselage at the exact desired they had to mount the wings too far forward, and at angles to the fuselage, the center of pressure would not enough to the rear to result in the desired amount of stability. By building sweepback into the wings, the designers can move the center of pressure rear. The amount of sweepback and the position wings then place the center of pressure in the correct

Contribution of the wing to static directional stability is small. The swept wing provides a stable contribution on the amount of sweepback, but the contribution small when compared with other components.

Avian at Hamilton

Lurking behind the hangars at Hamilton Airport yesterday was the unique Cooke Avian Adventurer ZK-CKE/2. So far unfinished, this aircraft was registered to Bruce Cooke of Cambridge 19Nov2008. Powerplant is to be a Subaru EJ20 Single cam, with an Autoflight reduction gearbox driving an Ivoprop electric Variable pitch prop.

Work has proceeded mightily since I saw the project in Bruce's workshop early in 2008.

The first ZK-CKE was of course the second PL-11 Airtruck, built by Waitomo Aviation at Te Kuiti and first flown 9Mar1965. Seen here at Ardmore in January 1966, it crashed in 1967. There will be an article on the PL-11s in an upcomong Aviation News magazine.

Airfoil investigation database

Pretty neat airfoil database with search and quick illustration capabilities.


Stability (Rolling)

About the aircraft’s longitudinal axis, which extends nose of the aircraft to its tail, is called lateral This helps to stabilize the lateral or “rolling effect” wing gets lower than the wing on the opposite side aircraft. There are four main design factors that make laterally stable: dihedral, sweepback, keel effect, weight distribution.

Most common procedure for producing lateral stability builds the wings with an angle of one to three degrees perpendicular to the longitudinal axis. The wings on side of the aircraft join the fuselage to form a slight V or called “dihedral.” The amount of dihedral is measured angle made by each wing above a line parallel to the axis.

Involves a balance of lift created by the wings’ AOA side of the aircraft’s longitudinal axis. If a momentary wind forces one wing to rise and the other to lower, the banks. When the aircraft is banked without turning, tendency to sideslip or slide downward toward the lowered occurs. [Figure 4-25] Since the wings have dihedral, strikes the lower wing at a much greater AOA than the wing. The increased AOA on the lower wing creates than the higher wing. Increased lift causes the lower begin to rise upward. As the wings approach the position, the AOA on both wings once again are equal, the rolling tendency to subside. The effect of dihedral produce a rolling tendency to return the aircraft to a laterally balanced flight condition when a sideslip occurs.

The restoring force may move the low wing up too far, so that the opposite wing now goes down. If so, the process is repeated, decreasing with each lateral oscillation until a balance for wings-level flight is finally reached.

Conversely, excessive dihedral has an adverse effect on lateral maneuvering qualities. The aircraft may be so stable laterally that it resists an intentional rolling motion. For this reason, aircraft that require fast roll or banking characteristics usually have less dihedral than those designed for less maneuverability.

Sweepback is an addition to the dihedral that increases the lift created when a wing drops from the level position. A sweptback wing is one in which the leading edge slopes backward. When a disturbance causes an aircraft with sweepback to slip or drop a wing, the low wing presents its leading edge at an angle that is perpendicular to the relative airflow. As a result, the low wing acquires more lift, rises, and the aircraft is restored to its original flight attitude.

Sweepback also contributes to directional stability. When turbulence or rudder application causes the aircraft to yaw to one side, the right wing presents a longer leading edge perpendicular to the relative airflow. The airspeed of the right wing increases and it acquires more drag than the left wing. The additional drag on the right wing pulls it back, turning the aircraft back to its original path.

Keel Effect and Weight Distribution
An aircraft always has the tendency to turn the longitudinal axis of the aircraft into the relative wind. This “weather vane” tendency is similar to the keel of a ship and exerts a steadying influence on the aircraft laterally about the longitudinal axis. When the aircraft is disturbed and one wing dips, the fuselage weight acts like a pendulum returning the airplane to its original attitude.

2009/10 winter season timetableAdria Airways

Adria Airways will launch its 2009/10 winter schedule tomorrow with 12 aircraft – 1 Bombardier CRJ100, 6 Bombardier CRJ200s, 4 Bombardier CRJ900s and 2 Airbus A320. One of Adria's A320s will be used for charter flights only, while the airline will receive 2 Airbus A319s during the winter season, in April, which are yet to be added to their schedule. Adria’s Boeing B737-500 will be returned to Ukraine International Airlines within a week. The schedule below is subject to change. Any changes will be brought to your attention by visiting the blog.

Frequency changes

Adria will be reducing many of its frequencies particularly to cities within the Balkans. Adria will reduce services to Tirana by 5 weekly flights brining the total to one daily flight between Ljubljana and Albania’s capital. Flights to Priština will be reduced by 3 weekly services and to Skopje by 2. Sarajevo will see the greatest reduction of flights, from 13 to 7 per week. A total of 4 extra flights will be added on the Ljubljana to Copenhagen service and there will be 2 extra flights to Istanbul when compared to the summer season. The airline’s most frequent service (to Frankfurt) will continue to served 31 times per week.

New and suspended routes

Adria Airways will terminate its seasonal services to Manchester, Dublin and Ohrid, as expected. Unexpectedly, the airline will terminate flights to Madrid and Athens. Currently, there are no announcements regarding the launch of any new routes during the 2009/10 winter season.

The The following displays all of the modifications taking place in the Adria Airways 2009/10 winter schedule from Ljubljana

DestinationFrequency Summer 09

Frequency Winter 09/10

Aircraft Summer 09

Aircraft Winter 09/10


All frequencies are on a weekly basis

Longitudinal Stability (Pitching)

In designing an aircraft, a great deal of effort is spent in developing the desired degree of stability around all three axes. But longitudinal stability about the lateral axis is considered to be the most affected by certain variables in various flight conditions.

Longitudinal stability is the quality that makes an aircraft stable about its lateral axis. It involves the pitching motion as the aircraft’s nose moves up and down in flight. A longitudinally unstable aircraft has a tendency to dive or climb progressively into a very steep dive or climb, or even a stall. Thus, an aircraft with longitudinal instability becomes difficult and sometimes dangerous to fly.

Static longitudinal stability or instability in an aircraft, is dependent upon three factors:
1. Location of the wing with respect to the CG
2. Location of the horizontal tail surfaces with respect to the CG
3. Area or size of the tail surfaces

In analyzing stability, it should be recalled that a body free to rotate always turns about its CG.

To obtain static longitudinal stability, the relation of the wing and tail moments must be such that, if the moments are initially balanced and the aircraft is suddenly nose up, the wing moments and tail moments change so that the sum of their forces provides an unbalanced but restoring moment which, in turn, brings the nose down again. Similarly, if the aircraft is nose down, the resulting change in moments brings the nose back up.

The CL in most asymmetrical airfoils has a tendency to change its fore and aft positions with a change in the AOA. The CL tends to move forward with an increase in AOA and to move aft with a decrease in AOA. This means that when the AOA of an airfoil is increased, the CL, by moving forward, tends to lift the leading edge of the wing still more. This tendency gives the wing an inherent quality of instability. (NOTE: CL is also known as the center of pressure (CP).)

Figure 4-20 line CG-CL-T represents the aircraft’s longitudinal axis from the CG to a point T on the horizontal stabilizer.

Most aircraft are designed so that the wing’s CL is to the rear of the CG. This makes the aircraft “nose heavy” and requires that there be a slight downward force on the horizontal stabilizer in order to balance the aircraft and keep the nose from continually pitching downward. Compensation for this nose heaviness is provided by setting the horizontal stabilizer at a slight negative AOA. The downward force thus produced holds the tail down, counterbalancing the “heavy” nose. It is as if the line CG-CL-T were a lever with an upward force at CL and two downward forces balancing each other, one a strong force at the CG point and the other, a much lesser force, at point T (downward air pressure on the stabilizer). To better visualize this physics principle: If an iron bar were suspended at point CL, with a heavy weight hanging on it at the CG, it would take downward pressure at point T to keep the “lever” in balance.

Even though the horizontal stabilizer may be level when the aircraft is in level flight, there is a downwash of air from the wings. This downwash strikes the top of the stabilizer and produces a downward pressure, which at a certain speed is just enough to balance the “lever.” The faster the aircraft is flying, the greater this downwash and the greater the downward force on the horizontal stabilizer (except T-tails). [Figure 4-21] stabilizers, the aircraft manufacturer sets the stabilizer at an angle that provides the best stability (or balance) during flight at the design cruising speed and power setting.

If the aircraft’s speed decreases, the speed of the airflow over the wing is decreased. As a result of this decreased flow of air over the wing, the downwash is reduced, causing a lesser downward force on the horizontal stabilizer. In turn, the characteristic nose heaviness is accentuated, causing the aircraft’s nose to pitch down more. [Figure 4-22] This places the aircraft in a nose-low attitude, lessening the wing’s AOA and drag and allowing the airspeed to increase. As the aircraft continues in the nose-low attitude and its speed increases, force on the horizontal stabilizer is once again Consequently, the tail is again pushed downward into a climbing attitude.

Continues, the airspeed again decreases, causing force on the tail to decrease until the nose Because the aircraft is dynamically stable, lower as far this time as it did before. The enough speed in this more gradual dive to another climb, but the climb is not as steep as one.

These diminishing oscillations, in which rises and lowers, the aircraft finally speed at which the downward force on the counteracts the tendency of the aircraft to dive. is attained, the aircraft is once again in continues in stabilized flight as long as airspeed are not changed.

Noted upon closing the throttle. The wings is reduced and the force at T in Figure 4-20 is not enough to hold the horizontal stabilizer down. It seems as if the force at T on the lever were allowing the force of gravity to pull the nose down. This is a desirable characteristic because the aircraft is inherently trying to regain airspeed and reestablish the proper balance.
Power or thrust can also have a destabilizing effect in that an increase of power may tend to make the nose rise. The aircraft designer can offset this by establishing a “high thrust line” wherein the line of thrust passes above the CG. [Figures 4-23 and 4-24] In this case, as power or thrust is increased a moment is produced to counteract the down load on the tail. On the other hand, a very “low thrust line” would tend to add to the nose-up effect of the horizontal tail surface.

With CG forward of the CL and with an tail-down force, the aircraft usually tries to safe flying attitude.

Following is a simple demonstration of longitudinal Trim the aircraft for “hands off” control in level momentarily give the controls a slight push to aircraft down. If, within a brief period, the nose rises original position and then stops, the aircraft is statically Ordinarily, the nose passes the original position (that flight) and a series of slow pitching oscillations the oscillations gradually cease, the aircraft has stability; if they continue unevenly, the aircraft has stability; if they increase, the aircraft is unstable.

How to simulate a wing with QFLR5 -tutorial

1. Batch simulate airfoil for different Reynolds numbers so that the whole range of the wing is covered (speed you want to simulate + chord length on the root and tip). Fast way to calculate Reynolds numbers and mach numbers for your simulation case is to use this web page:
Use the metric values.

2. When you know your Mach number and Reynolds number range (ranging from tip to root), simulate the airfoil of your choice on QFLR5 on that range. Using batch analysis feature.

Please note that it can take significant amount of time to batch analysis all the airfoils you want to simulate (e.g. if your wing is going to use more than one airfoil for example, and if you want to compare it to other wings which have different airfoils).

3. Go to Wing and Plane Design. Select from Unit preferences. Replace millimeter units with meter, so you want m/s, m^2, m for length etc.

4. Select Define wing from the menu. A window with a spreadsheet appears.

5. Define the wing by entering the y positions (you can define as many as you like). For simple taper it is enough to enter root to y position 0 and then tip to the position where the wing ends. For 12 meters long wing this position is 6 meters (as the plane is quite often symmetric). Select chord length for the root and tip. Select dihedral and twist for the root and tip. Select foil for the root and tip. Select the number of panels you want for the simulation. The more panels, the more accurate. Please note that the dimensions here affect to the Reynolds number, so if your simulation later says it is out of flight envelope, it means that you have not simulated in the Foil direct analysis section the appropriate Reynolds number range, something is missing. Please go back to the web site stated above and check your Reynolds numbers.

6. When you have a wing with desired shape with desired airfoils, click Save and Close from the bottom.

8. Select from Polars menu Define analysis. Select your simulation speed. Please note that this affects your Reynolds number. You need to know at this point your desired speed you want to fly. Select plane weight and moment location on the wing. You can
then select 3D panels. For example I have 150 kt, 800 kg, 0.40 m, 0.00, 0.00.

9. Analysis settings on the right, uncheck sequence if you are interested in one angle of attack only. This most likely is the case if you want to simulate a constant speed (e.g. the 150 kts described above). Then click Analyze and your wing is analyzed for that angle of attack.

Some examples of analyzed wings:


KS20 (same wing):

NASA NLF414F (same wing again):

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