Eurocopter EC120 ZK-IWC noted at Ardmore today, 1Dec, undergoing engine runs with its registration temporarily applied on the tail. It was registered to Henley Property Trust, Invercargill in July of this year so not sure if it has taken this long to surface or if its a repaint and just not quite completed yet.

Not the best location unfortunately, but nice to see a different scheme on a Eurocopter.
Robinson R22 Beta ZK-HHQ also at Ardmore today, still wearing the titles of Aspiring Helicopters however now registered to Heliflite Pacific where it was sitting outside of. Aspiring took delivery of another R22 Beta, ZK-IHQ, earlier this year.

ZK-HHQ not to be confused with...............
ZK-IHQ in January 2009.

Ailerons control

Ailerons control roll about the longitudinal axis. The ailerons are attached to the outboard trailing edge of each wing and move in the opposite direction from each other. Ailerons are connected by cables, bell cranks, pulleys and/or push-pull tubes to a control wheel or control stick.

Moving the control wheel or control stick to the right causes the right aileron to deflect upward and the left aileron to deflect downward. The upward deflection of the right aileron decreases the camber resulting in decreased lift on the right wing. The corresponding downward deflection of the left aileron increases the camber resulting in increased lift on the left wing. Thus, the increased lift on the left wing and the decreased lift on the right wing cause the airplane to roll to the right. Adverse Yaw Since the downward deflected aileron produces more lift as evidenced by the wing rising, it also produces more drag. This added drag causes the wing to slow down slightly. This results in the aircraft yawing toward the wing which had experienced an increase in lift (and drag). From the pilot’s perspective, the yaw is opposite the direction of the bank. The adverse yaw is a result of differential drag and the slight difference in the velocity of the left and right wings. [Figure 5-5]

Adverse yaw becomes more pronounced at low airspeeds. At these slower airspeeds aerodynamic pressure on control low and larger control inputs are required to maneuver the airplane. As a result, the increase in aileron deflection causes an increase in adverse yaw. The yaw is especially evident in aircraft with long wing spans.

Application of rudder is used to counteract adverse yaw. The amount of rudder control required is greatest at low airspeeds, high angles of attack, and with large aileron deflections. Like all control surfaces at lower airspeeds, the vertical stabilizer/rudder becomes less effective, and magnifies the control problems associated with adverse yaw.

All turns are coordinated by use of ailerons, rudder, and elevator. Applying aileron pressure is necessary to place the aircraft in the desired angle of bank, while simultaneous application of rudder pressure is necessary to counteract the resultant adverse yaw. Additionally, because more lift is required during a turn than when in straight-and-level flight, the angle of attack (AOA) must be increased by applying elevator back pressure. The steeper the turn, the more elevator back pressure is needed.

As the desired angle of bank is established, aileron and rudder pressures should be relaxed. This stops the angle of bank from increasing, because the aileron and rudder control surfaces are in a neutral and streamlined position. Elevator back pressure should be held constant to maintain altitude. The roll-out from a turn is similar to the roll-in, except the flight controls are applied in the opposite direction. Aileron and rudder are applied in the direction of the roll-out or toward the high wing. As the angle of bank decreases, the elevator back pressure should be relaxed as necessary to maintain altitude.

In an attempt to reduce the effects of adverse yaw, manufacturers have engineered four systems: differential ailerons, frise-type ailerons, coupled ailerons and rudder, and flaperons.

For Technorati Claim: 5V6X2HKVUHC4

Up and Away

A small selection of photographs taken and supplied by Warren Thompson from an early morning balloon launch out of the Cust Domain on Sunday the 29th.

Three balloons were involved. Above are the Cameron A-275 ZK-FAA (c/n 10249) with the smaller Cameron Z-90 ZK-UUA (4942) beyond.

VFR on top.
Below ZK-UUA which was on a training flight descending towards cloud tops.

Above is the Cameron A-375 ZK-FAR3 (10703) with the shadow of envelop and basket with a "Glory" around the photographer as they are about to enter cloud on descent.
FYI. The model number, eg "375" , is the cubic capacity of the envelope in thousands of cubic feet. So ZK-FAR has an envelope of 375,000 cubic feet.

Primary Flight Controls

Aircraft control systems are carefully designed to provide adequate responsiveness to control inputs while allowing a natural feel. At low airspeeds, the controls usually feel soft and sluggish, and the aircraft responds slowly to control applications. At higher airspeeds, the controls become increasingly firm and aircraft response is more rapid.

Movement of any of the three primaries flight control surfaces (ailerons, elevator or stabilator, or rudder), changes the airflow and pressure distribution over and around the airfoil. These changes affect the lift and drag produced by the airfoil/control surface combination, and allows a pilot to control the aircraft about its three axes of rotation.

Design features limit the amount of deflection of flight control surfaces. For example, control-stop mechanisms may be incorporated into the flight control linkages, or movement of the control column and/or rudder pedals may be limited. The purpose of these design limits is to prevent the pilot from inadvertently over controlling and overstressing the aircraft during normal maneuvers.

A properly designed airplane is stable and easily controlled during normal maneuvering. Control surface inputs cause movement about the three axes of rotation. The types of stability an airplane exhibits also relate to the three axes of rotation. [Figure 5-4]

Post-Turkey Day Update

"It's a bird! It's a plane! Actually, it's both...and edible!"

Fresh but larger in girth from the great American pastime of massive calorie infusions and days of leftovers (turkey sandwich/curried Turkey/cranberry yogurt surprise (don't ask) etc., let's see whassup around the old info-hangar.

Looking to e-gab with other light sport enthusiasts? There are some cool sites around with lots of hands-on topics such as training, maintenance, fun flying and more. Here are a couple I've come across that seem well-attended: Sport Pilot Talk and South Africa's AvCom with a look at Light Sport and GA flying in the southern Hemisphere

Lots of links here to tons of general LSA sites : Light Sport Aircraft HQ

Flight training resource guide: Pilot Journey

Experimental/homebuilt and light sport discussions (Jabiru and Rotax forums here): Wings Forum

BTW: Sebring's annual Light Sport Aviation Expo is kicking off Jan. 21-24, read all about this ever-growing LSA-exclusive show that kicks off the year's flying events.

Here's a nice general piece by Dan Pimentel, still timely, that looks at the Sport Pilot demographic on the Aircraft website.

A lively blog, Aviation Critic, has an interesting riff on our recent article on the ICON A5 plus lots of other cool topics.

The Big Daddy: Aviation Week has been around for longer than I can remember (I drew pictures from their photos in my teens in the '60s) and covers pretty much everything of global aviation import. For instance, here's a piece they just did on AVIC, the Chinese air defense monolith that includes Shenyang, the company that's making, you guessed it, Cessna's SkyCatcher!

Speaking of the C-162, the general press is catching on.

Stay tuned, there's more to come, flyfolk!

Flight Control Systems

Aircraft flight control systems consist of primary and secondary systems. The ailerons, elevator (or stabilator), and rudder constitute the primary control system and are required to control an aircraft safely during flight. Wing flaps, leading edge devices, spoilers, and trim systems constitute the secondary control system and improve the performance characteristics of the airplane or relieve the pilot of excessive control forces.

Introduction to Flight Controls

This chapter focuses on the flight control systems a pilot uses to control the forces of flight, and the aircraft’s direction and attitude. It should be noted that flight control systems and characteristics can vary greatly depending on the type of aircraft flown. The most basic flight control system designs are mechanical and date back to early aircraft. They operate with a collection of mechanical parts such as rods, cables, pulleys, and sometimes chains to transmit the forces of the flight deck controls to the control surfaces. Mechanical flight control systems are still used today in small general and sport category aircraft where the aerodynamic forces are not excessive. [Figure 5-1]

As aviation matured and aircraft designers learned more about aerodynamics, the industry produced larger and faster aircraft. Therefore, the aerodynamic forces acting upon the control surfaces increased exponentially. To make the control force required by pilots manageable, aircraft engineers designed more complex systems. At first, hydro mechanical designs, consisting of a mechanical circuit and a hydraulic circuit, were used to reduce the complexity, weight, and limitations of mechanical flight controls systems. [Figure 5-2]

As aircraft became more sophisticated, the control surfaces were actuated by electric motors, digital computers, or fiber optic cables. Called “fly-by-wire,” this flight control system replaces the physical connection between pilot controls and the flight control surfaces with an electrical interface. In addition, in some large and fast aircraft, controls are boosted by hydraulically or electrically actuated systems. In the fly-by-wire and boosted controls, the feel of the control reaction is fed back to the pilot by simulated means.

Current research at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center involves Intelligent Flight Control Systems (IFCS). The goal of this flight project is to develop an adaptive neural network-based control system. Applied directly to flight control system feedback errors, IFCS provides adjustments to improve aircraft performance in normal flight as well as with system failures. With IFCS, a pilot is able to maintain control and safely land an aircraft that has suffered a failure to a control surface or damage to the airframe. It also improves mission capability, increases the reliability and safety of flight, and eases the pilot workload.

Today’s aircraft employ a variety of flight control systems. For example, some aircraft in the sport pilot category rely on weight-shift control to fly while balloons use a standard burn technique. Helicopters utilize a cyclic to tilt the rotor in the desired direction along with a collective to manipulate rotor pitch and anti-torque pedals to control yaw. [Figure 5-3]

For additional information on flight control systems, refer to the appropriate handbook for information related to the flight control systems and characteristics of specific types of aircraft.

Austrian and Jat unite

No easy ride for Niki
Austrian and Jat Airways have united forces in order to protect their monopoly on the Vienna – Belgrade – Vienna service which they have held for years. The 2 will face tough competition from the Austrian based low cost Niki, which will begin services from Vienna to Belgrade on February 1. Austrian has negotiated with Jat and decided to launch 4 extra weekly services. The airline’s new flights will depart from Vienna in the evening and depart from Belgrade at 4.40 in the morning. However, Jat is negotiating to shift the departure time from Belgrade to a more suitable morning hour. Jat Airways will code share on all 4 additional flights.

On the other hand, Jat Airways will increase capacity on services to Vienna. The airline will upgrade 4 of its weekly flights from an ATR72 to a Boeing B737-300. Austrian will also codeshare on these flights.

The 2 airlines will have 31 weekly flights from Belgrade to Vienna from February 1, 2010 when the extra frequencies commence. Austrian and Jat are hoping to extinguish the competition they face from Niki. A return ticket with Austrian/Jat will set passengers back 107 Euros including all taxes.

Meanwhile, Romania’s TAROM will begin services from Bucharest to Belgrade soon. Jat Airways will codeshare on the service.

Crisis not over yet

Zagreb reports greater passenger decreases
Some Croatian airports for the month of October have reported a big decline in passenger figures when compared to last year. Over the past few months the number of passengers handled was lower than last year but the losses were not as great as they were at the beginning of the year, prompting the belief that all the affected airports will stage a recovery by the end of 2009. However, Zagreb, Split, Dubrovnik and Pula continue to see passenger numbers fall while Rijeka is the newest addition to the list.

The number of passengers handled at Zagreb Airport in October decreased by 10.4%. A total of 174.490 passed through the airport this October compared to last year’s 194.747. The number of passengers transiting through Zagreb Airport fell by a significant 71%. Rijeka, which saw a 5.6% increase in September saw a 15.3% passenger decline in October. Continuing with its downward trend was Pula Airport which handled 10.781 passengers, down by 16%. Dubrovnik and Split also reported losses – 8.2% and 2% respectively.

On a more positive note, Zadar continues to report substantial passenger growth with its October 2009 figures increasing by 83.8%. This growth can be largely contributed by the increased number of operations from the airport. Osijek also reported good results with passenger figures increasing by 62.6%.

Passenger figures at Croatian airports in 2009:
· January
· February
· March
· April
· May
· June
· July
· August
· September

Question Time # 80 resolved

Flammin Nora - The correct answer before the ink had even dried. Looks like I will have to go fishing today.

It is indeed Reims/Cessna F406 Caravan II ZK-XLF (c/n 0057) being tinkered around with at Hamilton on 23-02-2009.

So Anonymous scores : If you flick your snail mail address to me at bluebus@windowslive.com I will send the fish forth.

Thanks ZK-CKE for the info on the CII allocation - I hadn't picked up on that earlier.

There have been two airframes on the NZ register scattered over five registrations.

C/n 0012 ex Kenya. Became ZK-CII on 10-08-1998 to Aeromotive. Re-registered as ZK-VAA2 for Vincent on 08-05-2003. Re-re-registered as ZK-XLC with Kiwi Air on 15-01-2008.

C/n 0057 ex New Caledonia. Became ZK-VAF on 31-12-2002 with Vincent. Re-registered as ZK-XLF on 27-01-09 for Kiwi Air.

Question time #80

Type + Model + Registration = Chocolate Fish.

Forli flights for Niš

Soon in Niš
On Thursday, after weeks of negotiations, the Italian low cost airline Wind Jet confirmed that it will commence services from Forli to Niš Constantine the Great Airport in Serbia. The agreement was signed between the airport’s and airline’s management in the Serbian city. Wind Jet will operate flights every Thursday, once per week. This excludes the inaugural flight which will operate on Saturday, December 26. A return ticket from Forli to Niš will set passengers back between 83 and 200 Euros (depending if the passenger decides to choose greater flexibility with ticketing) – all taxes included. Fares above or below this price range won’t be found until June next year as the prices have been fixed during the promotional trial period.

Forli is located South-East of Bologna and will take passengers an extra hour to arrive there by bus, if they choose to do so. The management of Niš Airport is hoping that Swiss authorities will issue a license to Montenegro Airlines so that it can begin services from the airport to Zurich. Although, this seems unlikely at this point. The CEO of Jat Airways, which terminated all services from Niš this winter, said that the Serbian national carrier is interested in restarting flights from the city if it is economically viable. After a meeting with the mayor of Niš, Srdjan Radovanović said that the airline will look into possible routes that could be launched during the 2010 summer season.

All flight details for the new Forli – Niš service can be found on the right hand side in the “new route launches” section.

From the shoe box. Canterbury Wanderer. Auster J5F Aiglet Trainer ZK-BCQ

I was talking to a very elderly gentleman recently and he mentioned the "Canterbury Wanderer" that he flew in the 60's. From the clues he could recall I deduced it to be the Auster J5F Aiglet Trainer ZK-BCQ.
The J5F (as I am sure you all know) was basically a J5 fuselage slightly widened and stressed to become the first fully aerobatic Auster. It had an entirely new wing some 4 foot shorter and supported by equal sized wing struts. It also had a larger, horn balanced rudder. The prototype, using the Auster test registration of G-25-1 first flew in 1951 (I think) followed by a further 89 airframes; eight of which reach NZ.
ZK-BCQ (c/n 3111) was imported new by the NZ agents & obtained its CofA on 26-02-1954 and delivered to the Canterbury Aero Club. The above photograph was taken in March of 1954.
I believe it went briefly to a K F Sutherland in 1964 but was returned to the Canterbury Aero Club fairly soon after. About this time it seemed to have gained the "Canterbury Wanderer" name.
The above pic taken on 28-06-1969 shows it in the rear half of the old Club hangar at Christchurch. Note the Turbulent in behind. At about this time ownership moved to C R Dann & S M Marker of Christchurch. (Mr Marker previously operated the Tiger Moth ZK-BFS and the Fox Moth ZK-ASP in the early 60's). Annual ownership changes then took place with W G Bradshaw from 07-04-1970; R T Lloyd from 25-03-1971 (pic below taken at Wellington on 17-10-1971 - with "The Pig" in the background);
Ray Thurston of Blenheim from 01-03-1973 then a quick move to Auckland for J W Bushell & G M Ritchie on 14-04-1973. J W Black of Huntly is listed from 08-05-1978. On 02-07-1978 during a precautionary landing on the beach near Port Waikato its undercarriage collapsed. It was then submerged by the incoming tide.
Pic above is at North Shore on 05-01-1986 (looking rather bent & twisted - and is that fire damage up front ?)
It was then stored with ownership moving to the Confederate Air Force NZ Wing on 17-01-1986. Its registration was cancelled on 23-01-1991.
I believe it is currently under restoration at Omaka with Shane Glassey and Graham Orphan.
I would appreciated any additional details on this aircraft.

Mat Airways – the story continues

Mat Airways awaits license
As was reported earlier this year, the defunct national carrier of Macedonia will be revived under a new name, Mat Airways, in a combined Serbian-Macedonian business venture. As the Macedonian website “Total” reports, the new owners will allegedly be Serbia’s largest tour operator Kontiki Travel, as well as the Belgrade based Metropolitan Investment Group and Gomeks Financing from Skopje which would take care of finances. Gorgi Čačkirov, a former MAT pilot, has been named the CEO of the airline.

The Macedonian Civil Aviation Agency (ACV), which had been in constant war with MAT Macedonian Airlines until it finally grounded the airline, has not confirmed whether Mat Airways registration papers had been handed inn but warns that any start up airline in Macedonia must have at least 51% of its shares owned by a Macedonian company. The ACV also says that when registration papers are handed inn a commission will have to rule whether r there is a connection between the defunct MAT and Mat Airways.

Reportedly, several former MAT employees are working on the new Mat Airways project. “It has not been decided when the airline will begin operations. Mat Airways is an independent airline and is not associated with MAT”, Čačkirov says.MAT Macedonian Airlines has still not begun bankruptcy proceedings. When this process commences it ill be determined who exactly will receive the airline’s property, including a Boeing B737-500. Mat Airways is the latest in a string of companies trying to register airlines in the country following the demise of MAT.

easyJet to Priština

Soon in Priština
After Air Berlin created a new base at Priština Airport, the low cost easyJet has requested a license from authorities. From June 19, 2010, easyJet is initially expected to operate 2 weekly services from Geneva, with the option to expand its Priština network further in the future. In markets where easyJet operates, its strategy has been to offer low prices. In the first three quarters of this year, easyJet had an income of 2.6 billion British Pounds and 45.2 million passengers.

easyJet currently has regular flights to some 100 cities in 27 European countries. Following Air Berlin, which began flights to Priština from Swiss and German cities in November, easyJet will be the second major European air carrier to enter the market. However, easyJet will first have to wait for approval before tickets can go on sale.

As a result of the increased number of airlines operating flights to Priština, the airport is one of the rare in the region posting strong passenger growth this year.

Revived interest in Jat?

Deja vu
Serbian media are reporting that Turkish Airlines, Aeroflot and the Greek based Marfin Investment Group, are all interested in becoming partners with Jat Airways. According to media reports, Turkish Airlines is looking for yet another strategic partner in the region and would take over a part of the Serbian Government’s share in Jat, like it has done with Bosnia’s B&H Airlines. Turkish Airlines wouldn’t, apparently, provide Jat with finances but would provide the airline with much needed aircraft.

Russia’s Aeroflot which seemed keen on purchasing Jat in 2008, only to change its mind mid-year, is also interested in a strategic partnership with the Serbian carrier. The Marfin Investment Group, which recently purchased Olympic Airlines (now known as Olympic Air), is also reportedly interested in purchasing Jat and reorganising the airline.

However, in September, the Serbian Government announced that it does not intend to privatise Jat until 2012, by which it expects the airline will be back on its feet. The Serbian minister for infrastructure says that “there are a lot of interested parties willing to purchase Jat. The Government has formed a work group which will evaluate offers and the terms of any possible sale”.

The news should be taken with great caution as often media tend to sensationalise aviation news as was visible during Jat’s privatisation process last year when there were reports of wide scale interest. In spite of this it turned out that no company even purchased the tender documentation for the privatisation of the airline.

Super Drifter: New Tail for Oldie-but-Goodie

Lockwood Aircraft's Super Drifter open-cockpit kitbuilt plane, the resurrection of the Drifter design that was the basic concept for Phil Lockwood's AirCam twin-engine airplane, (a unique camera platform first created for National Geographic), is getting a new set of tailfeathers.
I first flew a Hummer ultralight, designed by Klaus Hill, back in the fall of 1980 at Crested Butte, CO. It belonged to hang gliding pal Gil Kinzie.
We were in CB for a soaring contest and he let several of us fly it, though most of us had no general aviation training. Ah, those wild and wooly days of free flight.
As such, the Drifter was one of the very first viable ultralights and presented a unique flying feel to its pilots: you sat out on the end of a long fuselage keel tube with everything - wings, motor, wheels - behind you!
Once you got over the initial floating-in-space challenges to your comfort zone, you fell in love with the incredibly open, free feeling.
But I digress.
Lockwood Aircraft has brought back the beloved design as the Super Drifter, with an 81hp Rotax 912UL - which gives the 495 lb. (empty wgt.) bird a real kick in the pants!
Specs and a blurb are here.
The tail mod, due next March, has two feet more horizontal span to augment pitch stability and elevator authority for float-equipped models. Lots of folks fly Super Drifters on floats.
Increasing the horsepower pops the Super Drifter off the water quickly and at low speeds, for shorter water takeoff runs. Low-power cruise makes for quiet flight, the power reserve is impressive and fuel efficiency is reputed to be super. The bird cruises between 55 and 75 mph.
The new horizontal stabilizers will be available as a retrofit kit for existing float-equipped Super Drifters and standard on new kits going on floats, according to Lockwood's go-to guy George Weber.
If you like to bolt things together and have a spare $45K or so laying around, the Super Drifter is one great way to go for purely fun flight.
---Super Drifter photo courtesy Lockwood Aircraft
---Gil Kinzie photo courtesy John Coe

Avid Heavy Hauler UL ZK-WEN.

Jabiru powered Avid Heavy Hauler UL ZK-WEN (c/n 1226D) as seen at Rangiora today (24-11-2009) having a transponder fitted.

Built by Warren Edward Newland and using his initials it became ZK-WEN on 12-02-1997.

It was sold on to Howard B Jenkin on 03-12-2002 and Warren went on to the Alpi Pioneer ZK-WLD from 29-11-2005. I believe Warren operated a Micro B22 Bantam between 1987 & 1988.

ZK-WEN changed hands again on 26-07-2005 to Peter Karl of Ohaupo. Now Peter has had a fair share of aircraft over the years including :- Delore Skytrike ZK-EZY 1982-1999: Micro B22 Bantam ZK-FXG 1990-2000: Aerochute Dual ZK-JHD 2000-2005: Avid Flyer STOL ZK-SPY 2000- 2006: Titan Tornado ZK-TRT2 2006-2008: Avid Flyer Speedwing ZK-MMP 2006-2009: Eipper Quicksilver MXL 11 ZK-MWB from 2007: Jabiru UL-T ZK-CJP from 2009 and Micro B22 Bantam ZK-FWN from 2009.

ZK-WEN moved on to Geoff I Royds of Ashburton on 10-10-2005. Geoff has also operated Auster J1B ZK-AZU 1970-1974: Cessna 180 ZK-BLL 1974-1980: Cessna A188 ZK-CSE 1979-1981: and Cessna A188B ZK-DPW 1980-1989.
Now how many aircraft have I missed that have been operated by these respective owners ??

Ljubljana Airport transformation

Future of Ljubljana Airport
Passengers and income have significantly declined at Slovenia’s largest airport this year, however development which is taking place is securing Ljubljana’s leading position when it comes to modernity and future prospects.

Figures show that the number of passengers and the amount cargo at the airport has doubled within the last decade. This places it among the most important regional distribution and logistics centres. The opportunities this trend offers were recognised by Ljubljana Jože Pučnik Airport’s management, which has made plans to build a city in its own right next to Slovenia’s central airport. Aeropolis will stretch over 80 hectors of land and will radically change the appearance of the airport. This substantial project aims to develop the airport’s commercial infrastructure and provide hotel accommodation, office space, commercial premises and logistics services, which the airport currently lacks but are in high demand. “Investors have already expressed a considerable interest for the projects”, Zmago Skobir, the CEO of Ljubljana Airport said to the “Slovenian Times”.

Ljubljana’s airport will be transformed into a bustling hub catering to the needs of travellers, those involved in business as well as for the demands of freight traffic. The master plan includes a hotel area, business centre, business park and logistics park. The implementation of these four key projects is about to begin. The project will begin with the construction of a new airport terminal building. The construction of Aeropolis will take place in four phases: the first one, which should be complete in 2012, is decisive and most important because it will dictate the further development of the entire project. Its priorities are a hotel and congress centre alongside the further enlargement of the logistics park. Other milestones in the expected development are the relocation of the existing access road and the construction of a business park by 2015 as well as railway construction in the final stage. The continuous upgrade of the infrastructure is planned, however, the first two stages will dictate its extent.

Other airports close by have recognised the scale of Ljubljana’s project and the transformation it will undergo. The previous CEO of Zagreb Airport said, a few months ago, that Croatia’s main airport must start with the construction of a new terminal otherwise it might loose clients to Slovenia’s Ljubljana Airport. The airport project in Ljubljana has been labelled of national importance by the Slovenian Government.

Knockin' Around The Campus

With the holiday season about to land on our heads, who's got time to see who's doing what around the industry? Me, that's who.

Hit the links below to some recent news and events:

Chesapeake Sport Pilot hosted an event recently on its home turf, to celebrate opening a new 6,000 sq. ft. building for its light sport training ops. CSP claims 70 active LSA flight students and 300 LSA renters.

Many years ago I built an experimental Kitfox (s.n. #124 - last I heard it's still flying, 22 years later!) The company has been through several iterations and owner changes since then but it's back to the future and running strong as Kitfox Aircraft LLC, run by John McBean of Homedale, ID. Now they've got an SLSA version of the lovely taildragger, base price around $83K, also available in tricycle gear. Check it out.

CubCrafters has jumped into the +100 sales club this fall, according to industry watchdog Dan Johnson and in this economy that's no mean feat. Only Flight Design, American Legend, Tecnam and Remos had broken the century mark before. Congrats folks!

Popular flight instrument maker Dynon has set prices for the new SkyView 10" and 7" PFD and Engine Monitor EFIS displays.


Another shot of Vans RV9A ZK-RVY at Ardmore 23Nov (following on from Sir Minty's recent post earlier this month).

Serbia invites low cost airlines

Will Belgrade be seeing pink anytime soon?
Ryanair, Wizz Air and easyJet , Europe’s leading low cost airlines have been invited to Belgrade by the Serbian Civil Aviation Directorate. The Directorate will present to them the structure of Serbia’s travel industry and the advantages of doing business in Serbia. The presentations will be headed by the director of Serbia’s Civil Aviation Directorate, Nebojša Starčević (a former Jat Airways CEO). “We want to show that things in Serbia are changing”, a spokeswomen from the Directorate was quoted by local media. Last year, answering to questions posed by a Belgrade newspaper, a Ryanair spokesperson said that “the airline has no immediate plans to begin services to Serbia”. None of the 3 aforementioned airlines have responded to the Directorate’s invitation.

Drawn in by the new open sky agreement and a European Union decision to allow Serbian citizens to travel visa free from December 19, airlines from Romania, Hungary, Slovenia and Croatia are set to begin flying from Belgrade in the next 6 months. Romania's TAROM will commence flights between Bucharest and Belgrade on December 7. Croatia Airlines and Slovenia's Adria Airways are due to begin flights to Belgrade next year. The Adria Airways service from Ljubljana to Belgrade is planned from March 1, while flights from Zagreb are expected to commence on May 1. Hungary’s Malev is set to begin flights to Belgrade in mid December.

Question time # 79 resolved

Yes indeed it is the tail end of the Polikarpov I-16 ZK-JIO (Red 34).
As seen at Wanaka on 11-10-2007.
Chocky fish won on the first very first response: By Anonymous.

High Speed Flight Controls

On high-speed aircraft, flight controls are divided into primary flight controls and secondary or auxiliary flight controls. The primary flight controls maneuver the aircraft about the pitch, roll, and yaw axes. They include the ailerons, elevator, and rudder. Secondary or auxiliary flight controls include tabs, leading edge flaps, trailing edge flaps, spoilers, and slats.

Spoilers are used on the upper surface of the wing to spoil or reduce lift. High speed aircraft, due to their clean low drag design use spoilers as speed brakes to slow them down. Spoilers are extended immediately after touchdown to dump lift and thus transfer the weight of the aircraft from the wings onto the wheels for better braking performance. [Figure 4-63]
Jet transport aircraft have small ailerons. The space for ailerons is limited because as much of the wing trailing edge as possible is needed for flaps. Also, a conventional size aileron would cause wing twist at high speed. For that reason, spoilers are used in unison with ailerons to provide additional roll control.

Some jet transports have two sets of ailerons, a pair of outboard low-speed ailerons and a pair of high-speed inboard ailerons. When the flaps are fully retracted after takeoff, the outboard ailerons are automatically locked out in the faired position.

When used for roll control, the spoiler on the side of the up-going aileron extends and reduces the lift on that side, causing the wing to drop. If the spoilers are extended as speed brakes, they can still be used for roll control. If they are the differential type, they extend further on one side and retract on the other side. If they are the non-differential type, they extend further on one side but do not retract on the other side. When fully extended as speed brakes, the non-differential spoilers remain extended and do not supplement the ailerons.

To obtain a smooth stall and a higher AOA without airflow separation, the wing’s leading edge should have a well-rounded almost blunt shape that the airflow can adhere to at the higher AOA. With this shape, the airflow separation starts at the trailing edge and progresses forward gradually as AOA is increased.

The pointed leading edge necessary for high-speed flight results in an abrupt stall and restricts the use of trailing edge flaps because the airflow cannot follow the sharp curve around the wing leading edge. The airflow tends to tear loose rather suddenly from the upper surface at a moderate AOA. To utilize trailing edge flaps, and thus increase the MAX, the wing must go to a higher AOA without airflow separation. Therefore, leading edge slots, slats, and flaps are used to improve the low-speed characteristics during takeoff, climb, and landing. Although these devices are not as powerful as trailing edge flaps, they are effective when used full span in combination with high-lift trailing edge flaps. With the aid of these sophisticated high-lift devices, airflow separation is delayed and the MAX is increased considerably. In fact, a 50 knot reduction in stall speed is not uncommon.

The operational requirements of a large jet transport aircraft necessitate large pitch trim changes. Some requirements are:

  • A large CG range
  • A large speed range
  • The ability to perform large trim changes due to wing leading edge and trailing edge high-lift devices without limiting the amount of elevator remaining
  • Maintaining trim drag to a minimum

These requirements are met by the use of a variable incidence horizontal stabilizer. Large trim changes on a fixed-tail aircraft require large elevator defiections. At these large defiections, little further elevator movement remains in the same direction. A variable incidence horizontal stabilizer is designed to take out the trim changes. The stabilizer is larger than the elevator, and consequently does not need to be moving through as large an angle. This leaves the elevator streamlining the tail plane with a full range of movement up and down. The variable incidence horizontal stabilizer can be set to handle the bulk of the pitch control demand, with the elevator handling the rest. On aircraft equipped with a variable incidence horizontal stabilizer, the elevator is smaller and less effective in isolation than it is on a fixed-tail aircraft. In comparison to other flight controls, the variable incidence horizontal stabilizer is enormously powerful in its effect.
Because of the size and high speeds of jet transport aircraft, the forces required to move the control surfaces can be beyond the strength of the pilot. Consequently, the control surfaces are actuated by hydraulic or electrical power units. Moving the controls in the flight deck signals the control angle required, and the power unit positions the actual control surface. In the event of complete power unit failure, movement of the control surface can be effected by manually controlling the control tabs. Moving the control tab upsets the aerodynamic balance which causes the control surface to move.

John Shakes Shakes J1

Seen at Hood airfield, Masterton, late in the afternoon following the Vintage Aviator show last weekend was this little single-seater.
ZK-JGX is listed as a John Shakes Shakes J1. Apart from that, I know nothing about it.
Is it a local design, or built off an overseas-sourced plan?
Maybe Sir Minty will give us the benefit of his extensive knowledge.

No go for low cost airlines

No low cost flights to Montenegro anytime soon
Montenegro, a country whose economy is centred on tourism, is yet to attract any low cost airline. It seems that no low cost carrier is interested in beginning services to the country although the Montenegrin newspaper “Vijesti” outlines that the Montenegrin Government has not extended a helpful hand either. The ministry for transportation, maritime affairs and telecommunications says that people should be aware of the dark side of low cost airlines. “Low cost airlines that are interested in commencing services to Montenegro want certain amenities, such as lower airport taxes, reduced airport handling fees and so on. If we allow this to happen we would seriously be infringing competitiveness regulations and equal rights for all”, the ministry outlines. The ministry also added that no low cost airline has been issued permits to operate to Montenegro because no airline has asked for one.

The ministry has rejected claims that the Government is protecting the state owned Montenegro Airlines, which will end the year on a positive note, with more passengers and a break even balance sheet. Many Montenegrins are opting to fly out of Dubrovnik in Croatia with low cost carriers, the newspaper adds. Montenegro’s ministry of tourism says that it is trying to attract high-end tourists and present Montenegro as a luxurious tourist destination for the rich and famous.

Do you think low cost airlines could turn a profit on services to Podgorica and Tivat? Send a comment with your thoughts.

Function of Mach Buffet Boundaries

Mach buffet is a function of the speed of the airflow over the wing—not necessarily the speed of the aircraft. Any time that too great a lift demand is made on the wing, whether from too fast airspeed or from too high an AOA near the MMO, the “high-speed” buffet occurs. There are also occasions when the buffet can be experienced at much lower speeds known as the “low-speed Mach buffet.”

An aircraft flown at a speed too slow for its weight and altitude necessitating a high AOA is the most likely situation to cause a low-speed Mach buffet. This very high AOA has the effect of increasing airflow velocity over the upper surface of the wing until the same effects of the shock waves and buffet occur as in the high-speed buffet situation. The AOA of the wing has the greatest effect on inducing the Mach buffet at either the high-speed or low-speed boundaries for the aircraft. The conditions that increase the AOA, the speed of the airflow over the wing, and chances of Mach buffet are:

  • High altitudes—the higher an aircraft flies, the thinner the air and the greater the AOA required to produce the lift needed to maintain level flight.
  • Heavy weights—the heavier the aircraft, the greater the lift required of the wing, and all other things being equal, the greater the AOA.
  • G loading—an increase in the G loading on the aircraft has the same effect as increasing the weight of the aircraft. Whether the increase in G forces is caused by turns, rough control usage, or turbulence, the effect of increasing the wing’s AOA is the same.

Sweepback Effect

Most of the difficulties of transonic flight are associated with shock wave induced flow separation. Therefore, any means of delaying or alleviating the shock induced separation improves aerodynamic performance. One method is wing sweepback. Sweepback theory is based upon the concept that it is only the component of the airflow perpendicular to the leading edge of the wing that affects pressure distribution and formation of shock waves. [Figure 4-60]

On a straight wing aircraft, the airflow strikes the wing leading edge at 90°, and its full impact produces pressure and lift. A wing with sweepback is struck by the same airflow at an angle smaller than 90°. This airflow on the swept wing has the effect of persuading the wing into believing that it is flying slower than it really is; thus the formation of shock waves is delayed. Advantages of wing sweep include an increase in critical Mach number, force divergence Mach number, and the Mach number at which drag rises peaks. In other words, sweep delays the onset of compressibility effects.

The Mach number, which produces a sharp change in drag coefficient, is termed the “force divergence” Mach number and, for most airfoils, usually exceeds the critical Mach number by 5 to 10 percent. At this speed, the airflow separation induced by shock wave formation can create significant variations in the drag, lift, or pitching moment coefficients. In addition to the delay of the onset of compressibility effects, sweepback reduces the magnitude in the changes of drag, lift or moment coefficients. In other words, the use of sweepback “softens” the force divergence.

The stall situation can be aggravated by a T-tail configuration, which affords little or no pre-stall warning in the form of tail control surface buffet. [Figure 4-62] The T-tail, being above the wing wake remains effective even after the wing has begun to stall, allowing the pilot to inadvertently drive the wing into a deeper stall at a much greater AOA. If the horizontal tail surfaces then become buried in the wing’s wake, the elevator may lose all effectiveness, making it impossible to reduce pitch attitude and break the stall. In the pre-stall and immediate post-stall regimes, the lift/drag qualities of a swept wing aircraft (specifically the enormous increase in drag at low speeds) can cause an increasingly flightpath with no change in pitch attitude, further the AOA. In this situation, without reliable AOA a nose-down pitch attitude with an increasing no guarantee that recovery has been affected, elevator movement at this stage may merely keep stalled.

Characteristic of T-tail aircraft to pitch up viciously stalled in extreme nose-high attitudes, making difficult or violent. The stick pusher inhibits this At approximately one knot above stall speed, programmed stick forces automatically move the stick preventing the stall from developing. A G-limiter incorporated into the system to prevent the pitch generated by the stick pusher from imposing excessive aircraft. A “stick shaker,” on the other hand provides stall warning when the airspeed is five to seven percent above stall speed.

Airplane Shock Waves

When an airplane flies at subsonic speeds, the air ahead is “warned” of the airplane’s coming by a pressure change transmitted ahead of the airplane at the speed of sound. Because of this warning, the air begins to move aside before the airplane arrives and is prepared to let it pass easily. When the airplane’s speed reaches the speed of sound, the pressure change can no longer warn the air ahead because the airplane is keeping up with its own pressure waves. Rather, the air particles pile up in front of the airplane causing a sharp decrease in the flow velocity directly in front of the airplane with a corresponding increase in air pressure and density.

As the airplane’s speed increases beyond the speed of sound, the pressure and density of the compressed air ahead of it increase, the area of compression extending some distance ahead of the airplane. At some point in the airstream, the air particles are completely undisturbed, having had no advanced warning of the airplane’s approach, and in the next instant the same air particles are forced to undergo sudden and drastic changes in temperature, pressure, density, and velocity. The boundary between the undisturbed air and the region of compressed air is called a shock or “compression” wave. This same type of wave is formed whenever a supersonic airstream is slowed to subsonic without a change in direction, such as when the airstream is accelerated to sonic speed over the cambered portion of a wing, and then decelerated to subsonic speed as the area of maximum camber is passed. A shock wave forms as a boundary between the supersonic and subsonic ranges.

Whenever a shock wave forms perpendicular to the airflow, it is termed a “normal” shock wave, and the flow immediately behind the wave is subsonic. A supersonic airstream passing through a normal shock wave experiences these changes:
• The airstream is slowed to subsonic.
• The airflow immediately behind the shock wave does not change direction.
• The static pressure and density of the airstream behind the wave is greatly increased.
• The energy of the airstream (indicated by total pressure—dynamic plus static) is greatly reduced.

Shock wave formation causes an increase in drag. One of the principal effects of a shock wave is the formation of a dense high pressure region immediately behind the wave. The instability of the high pressure region, and the fact that part of the velocity energy of the airstream is converted to heat as it flows through the wave is a contributing factor in the drag increase, but the drag resulting from airflow separation is much greater. If the shock wave is strong, the boundary layer may not have sufficient kinetic energy to withstand airflow separation. The drag incurred in the transonic region due to shock wave formation and airflow separation is known as “wave drag.” When speed exceeds the critical Mach number by about 10 percent, wave drag increases sharply. A considerable increase in thrust (power) is required to increase flight speed beyond this point into the supersonic range where, depending on the airfoil shape and the angle of attack, the boundary layer may reattach.

Normal shock waves form on the wing’s upper surface and form an additional area of supersonic flow and a normal shock wave on the lower surface. As flight speed approaches the speed of sound, the areas of supersonic flow enlarge and the shock waves move nearer the trailing edge. [Figure 4-59]

Associated with “drag rise” are buffet (known as Mach buffet), trim and stability changes, and a decrease in control force effectiveness. The loss of lift due to airflow separation results in a loss of downwash, and a change in the position of the center pressure on the wing. Airflow separation produces a turbulent wake behind the wing, which causes the tail surfaces to buffet (vibrate). The nose-up and nose-down pitch control provided by the horizontal tail is dependent on the downwash behind the wing. Thus, an increase in downwash decreases the horizontal tail’s pitch control effectiveness since it effectively increases the angle of attack that the tail surface is seeing. Movement of the wing CP affects the wing pitching moment. If the CP moves aft, a diving moment referred to as “Mach tuck” or “tuck under” is produced, and if it moves forward, a nose-up moment is produced. This is the primary reason for the development of the T-tail configuration on many turbine-powered aircraft, which places the horizontal stabilizer as far as practical from the turbulence of the wings.

Boundary Layer Law

The viscous nature of airflow reduces the local velocities on a surface and is responsible for skin friction. As discussed earlier in the chapter, the layer of air over the wing’s surface that is slowed down or stopped by viscosity, is the boundary layer. There are two different types of boundary layer flow: laminar and turbulent.

Laminar Boundary Layer Flow
The laminar boundary layer is a very smooth flow, while the turbulent boundary layer contains swirls or “eddies.” The laminar flow creates less skin friction drag than the turbulent flow, but is less stable. Boundary layer flow over a wing surface begins as a smooth laminar flow. As the flow continues back from the leading edge, the laminar boundary layer increases in thickness.

Turbulent Boundary Layer Flow
At some distance back from the leading edge, the smooth laminar flow breaks down and transitions to a turbulent flow. From a drag standpoint, it is advisable to have the transition from laminar to turbulent flow as far aft on the wing as possible, or have a large amount of the wing surface within the laminar portion of the boundary layer. The low energy laminar flow, however, tends to break down more suddenly than the turbulent layer.

Boundary Layer Separation
Another phenomenon associated with viscous flow is separation. Separation occurs when the airflow breaks away from an airfoil. The natural progression is from laminar boundary layer to turbulent boundary layer and then to airflow separation. Airflow separation produces high drag and ultimately destroys lift. The boundary layer separation point moves forward on the wing as the AOA is increased. [Figure 4-58]

Vortex generators are used to delay or prevent shock wave induced boundary layer separation encountered in transonic flight. They are small low aspect ratio airfoils placed at a 12° to 15° AOA to the airstream. Usually spaced a few inches apart along the wing ahead of the ailerons or other control surfaces, vortex generators create a vortex which mixes the boundary airflow with the high energy airflow just above the surface. This produces higher surface velocities and increases the energy of the boundary layer. Thus, a stronger shock wave is necessary to produce airflow separation.

Recovery in sight for Adria?

Adria flying into profits and losses
Adria Airways posted an 800.000 Euro profit in the third quarter, its first profit in 2009. However, the airline expects a full year loss. This is despite the fact that the airline is expected to post another profit in the, current, fourth quarter. Speaking to the Slovenian News Agency, Adria Arways’ CEO, Tadej Tufek, said that the airline saw a decline in revenue due to the global financial crisis, which has led to a passenger decline as well as a financial deficit in other sectors Adria gains revenue from, such as cargo and aircraft maintenance. Tufek also mentions that the passenger structure has changed and that the airline has seen the transition of many business class passengers to economy, which in turn has seen finances tumble.

Nevertheless, the airline maintains that even with an avarage 15% passenger decrease in the first 9 months of 2009, it is still competitive. Adria is one of the rare European airlines which enjoys little competition on most of its services.

In a statement, Adria also confirmed that it will become a full member of Star Alliance in January. The group announced the elimination of the regional member designation (with Finland’s Blue1 and Croatia Airlines being the other 2 members) in June.

Adria removed a Boeing B737-500 from service this month. Next year it will withdraw one Airbus A320 from service and add 2 Airbus A319s. By next summer it plans to operate one A320, two A319s, four CRJ900s, six CRJ200s and one CRJ100.

Mach Number Versus Airspeed

It is important to understand how airspeed varies with Mach number. As an example, consider how the stall speed of a jet transport aircraft varies with an increase in altitude. The increase in altitude results in a corresponding drop in air density and outside temperature. Suppose this jet transport is in the clean configuration (gear and flaps up) and weighs 550,000 pounds. The aircraft might stall at approximately 152 KCAS at sea level. This is equal to (on a standard day) a
true velocity of 152 KTAS and a Mach number of 0.23. At FL 380, the aircraft will still stall at approximately 152 KCAS but the true velocity is about 287 KTAS with a Mach number of 0.50.

Although the stalling speed has remained the same for our purposes, both the Mach number and TAS have increased. With increasing altitude, the air density has decreased; this requires a faster true airspeed in order to have the same pressure sensed by the pitot tube for the same KCAS or KIAS (for our purposes, KCAS and KIAS are relatively close to each other). The dynamic pressure the wing experiences at FL 380 at 287 KTAS is the same as at sea level at 152 KTAS. However, it is flying at higher Mach number.

Another factor to consider is the speed of sound. A decrease in temperature in a gas results in a decrease in the speed of sound. Thus, as the aircraft climbs in altitude with outside temperature dropping, the speed of sound is dropping. At sea level, the speed of sound is approximately 661 KCAS, while at FL 380 it is 574 KCAS. Thus, for our jet transport aircraft, the stall speed (in KTAS) has gone from 152 at sea level to 287 at FL 380. Simultaneously, the speed of sound (in KCAS) has decreased from 661 to 574 and the Mach number has increased from 0.23 (152 KTAS divided by 661 KTAS) to 0.50 (287 KTAS divided by 574 KTAS). All the while the KCAS for stall has remained constant at 152. This describes what happens when the aircraft is at a constant KCAS with increasing altitude, but what happens when the pilot keeps Mach constant during the climb? In normal jet flight operations, the climb is at 250 KIAS (or higher (efig. heavy)) to 10,000 feet and then at a specified en route climb airspeed (such as about 330 if a DC10) until reaching an altitude in the “mid-twenties” where the pilot then climbs at a constant Mach number to cruise altitude.

Assuming for illustration purposes that the pilot climbs at a of 0.82 from sea level up to FL 380. KCAS goes from 543 to 261. The KIAS at each altitude would follow the same behavior and just differ by a few knots. Recall from the earlier discussion that the speed of sound is decreasing with the drop in temperature as the aircraft climbs. The Mach number is simply the ratio of the true airspeed to the speed of sound at flight conditions. The significance of this is that at a constant Mach number climb, the KCAS (and KTAS or KIAS as well) is falling off.
If the aircraft climbed high enough at this constant with decreasing KIAS, KCAS, and KTAS, it would begin to approach its stall speed. At some point the stall speed of the aircraft in Mach number could equal the of the aircraft, and the pilot could neither slow up (without stalling) nor speed up (without exceeding the max operating speed of the aircraft). This has been dubbed the “coffin corner.”

High Speed Flight: Subsonic Versus Supersonic Flow

In subsonic aerodynamics, the theory of lift is based upon the forces generated on a body and a moving gas (air) in which it is immersed. At speeds of approximately 260 knots, air can be considered incompressible in that, at a fixed altitude, its density remains nearly constant while its pressure varies. Under this assumption, air acts the same as water and is classified as a fluid. Subsonic aerodynamic theory also assumes the effects of viscosity (the property of a fluid that tends to prevent motion of one part of the fluid with respect to another) are negligible, and classifies air as an ideal fluid, conforming to the principles of ideal-fluid aerodynamics such as continuity, Bernoulli’s principle, and circulation.

In reality, air is compressible and viscous. While the effects of these properties are negligible at low speeds, compressibility effects in particular become increasingly important as speed increases. Compressibility (and to a lesser extent viscosity) is of paramount importance at speeds approaching the speed of sound. In these speed ranges, compressibility causes a change in the density of the air around an aircraft.

During flight, a wing produces lift by accelerating the airflow over the upper surface. This accelerated air can, and does, reach sonic speeds even though the aircraft itself may be flying subsonic. At some extreme AOAs, in some aircraft.

Robinson R44 Astro ZK-HCR

The above shot taken in the Heli Maintenance hangar at Christchurch on 04-09-2009 shows the Robinson R44 Astro (c/n 0323) being re-assembled following import from the UK.
It was first registered as G-HRHS to Sloane Helicopters Ltd at Sywell, Northampton on 15-04-1997 with a change to Stratus Aviation C/- Professional Projects Ltd of Hong Kong on 24-08-1999. Its UK registration was cancelled on 19-05-2009 for it to become ZK-HCR2 on 23-07-09.
Photo above shows it at Heli Maintenance having its rotor blades tracked on 19-11-09.
It is registered to Brent Dovey of Blenheim

Question time # 79

What's this then ?
What type ?
Give us a registration as well to earn the last chocky fish currently in stock.

High Speed Flight: Speed Ranges

The speed of sound varies with temperature. Under standard temperature conditions of 15 °C, the speed of sound at sea level is 661 knots. At 40,000 feet, where the temperature is –55 °C, the speed of sound decreases to 574 knots. In high-speed flight and/or high-altitude flight, the measurement of speed is expressed in terms of a “Mach number”—the ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions. An aircraft traveling at the speed of sound is traveling at Mach 1.0. Aircraft speed regimes are defined approximately as follows:

Subsonic—Mach numbers below 0.75
Transonic—Mach numbers from 0.75 to 1.20
Supersonic—Mach numbers from 1.20 to 5.00
Hypersonic—Mach numbers above 5.00
While flights in the transonic and supersonic ranges are common occurrences for military aircraft, civilian jet aircraft normally operate in a cruise speed range of Mach 0.7 to Mach 0.90.
The speed of an aircraft in which airflow over any part of the aircraft or structure under consideration first reaches (but does not exceed) Mach 1.0 is termed “critical Mach number” or “Mach Crit.” Thus, critical Mach number is defined as the maximum operating limit speed. is expressed in knots calibrated airspeed (KCAS), while is expressed in Mach number. The limit is usually associated with operations at lower altitudes and deals with structural loads and flutter. The limit is associated with operations at higher altitudes and is usually more concerned with compressibility effects and flutter. At lower altitudes, structural loads and flutter are of concern; at higher altitudes, compressibility effects and flutter are of concern.

Adherence to these speeds prevents structural problems due to dynamic pressure or flutter, degradation in aircraft control response due to compressibility effects (efig., Mach Tuck, aileron reversal, or buzz), and separated airflow due to shock waves resulting in loss of lift or vibration and buffet. Any of these phenomena could prevent the pilot from being able to adequately control the aircraft.

For example, an early civilian jet aircraft had a limit of 306 KCAS up to approximately FL 310 (on a standard day). At this altitude (FL 310), an of 0.82 was approximately equal to 306 KCAS. Above this altitude, an of 0.82 always equaled a KCAS less than 306 KCAS and, thus, became the operating limit as you could not reach the limit without first reaching the limit. For example, at FL 380, an of 0.82 is equal to 261 KCAS.

Effect of Load Distribution

The effect of the position of the CG on the load imposed on an aircraft’s wing in flight is significant to climb and with aft loading and “nose-down” trim, the tail surfaces exert less down load, relieving the wing of that much wing loading and lift required to maintain altitude. The required AOA of the wing is less, so the drag is less, allowing for a faster cruise speed. Theoretically, a neutral load on the tail surfaces in cruising flight would produce the most efficient overall performance and fastest cruising speed, but it would also result in instability. Modern aircraft are designed to require a down load on the tail for stability and controllability.

A zero indication on the trim tab control is not necessarily the same as “neutral trim” because of the force exerted by downwash from the wings and the fuselage on the tail surfaces.
The effects of the distribution of the aircraft’s useful load have a significant influence on its flight characteristics, even when the load is within the CG limits and the maximum permissible gross weight. Important among these effects are changes in controllability, stability, and the actual load imposed on the wing.

An aircraft becomes less controllable, especially ight speeds, as the CG is moved further aft. Which cleanly recovers from a prolonged spin with one position may fail completely to respond to recovery attempts when the CG is moved aft by one inch.

Common practice for aircraft designers to establish an aft that is within one inch of the maximum which allows recovery from a one-turn spin. When certificating an the utility category to permit intentional spins, the limit is usually established at a point several inches of that permissible for certification in the normal

Factor affecting controllability, which has become important in current designs of large aircraft, is the effect moment arms to the positions of heavy equipment The same aircraft may be loaded to maximum weight within its CG limits by concentrating fuel, and cargo near the design CG, or by dispersing cargo loads in wingtip tanks and cargo bins forward the cabin.

Same total weight and CG, maneuvering the maintaining level flight in turbulent air requires application of greater control forces when the load is the longer moment arms to the positions of the heavy fuel and cargo loads must be overcome by the action of the control surfaces. An aircraft with full outboard wing tanks or tip tanks tends to be sluggish in roll when control situations are marginal, while one with full nose and aft cargo bins tends to be less responsive to the elevator controls.

The rearward CG limit of an aircraft is determined largely by considerations of stability. The original airworthiness requirements for a type certificate specify that an aircraft in flight at a certain speed dampens out vertical displacement of the nose within a certain number of oscillations. An aircraft loaded too far rearward may not do this. Instead, when the nose is momentarily pulled up, it may alternately climb and dive becoming steeper with each oscillation. This instability is not only uncomfortable to occupants, but it could even become dangerous by making the aircraft unmanageable under certain conditions.

The recovery from a stall in any aircraft becomes progressively more difficult as its CG moves aft. This is particularly important in spin recovery, as there is a point in rearward loading of any aircraft at which a “flat” spin develops. A flat spin is one in which centrifugal force, acting through a CG located well to the rear, pulls the tail of the aircraft out away from the axis of the spin, making it impossible to get the nose down and recover.

An aircraft loaded to the rear limit of its permissible CG range handles differently in turns and stall maneuvers and has different landing characteristics than when it is loaded near the forward limit.

The forward CG limit is determined by a number of considerations. As a safety measure, it is required that the trimming device, whether tab or adjustable stabilizer, be capable of holding the aircraft in a normal glide with the power off. A conventional aircraft must be capable of a full stall, power-off landing in order to ensure minimum landing speed in emergencies. A tailwheel-type aircraft loaded excessively nose-heavy is difficult to taxi, particularly in high winds. It can be nosed over easily by use of the brakes, and it is difficult to land without bouncing since it tends to pitch down on the wheels as it is slowed down and flared for landing. Steering difficulties on the ground may occur in nosewheel-type aircraft, particularly during the landing roll and takeoff. To summarize the effects of load distribution:

  • The CG position influences the lift and AOA of the wing, the amount and direction of force on the tail, and the degree of defiection of the stabilizer needed to supply the proper tail force for equilibrium. The latter is very important because of its relationship to elevator control force.
  • The aircraft stalls at a higher speed with a forward CG location. This is because the stalling AOA is reached at a higher speed due to increased wing loading.
  • Higher elevator control forces normally exist with a forward CG location due to the increased stabilizer defiection required to balance the aircraft.
  • The aircraft cruises faster with an aft CG location because of reduced drag. The drag is reduced because a smaller AOA and less downward defiection of the stabilizer are required to support the aircraft and overcome the nose-down pitching tendency.
  • The aircraft becomes less stable as the CG is moved rearward. This is because when the CG is moved rearward it causes an increase in the AOA. Therefore, the wing contribution to the aircraft’s stability is now decreased, while the tail contribution is still stabilizing. When the point is reached that the wing and tail contributions balance, then neutral stability exists. Any CG movement further aft results in an unstable aircraft.
  • A forward CG location increases the need for greater back elevator pressure. The elevator may no longer be able to oppose any increase in nose-down pitching. Adequate elevator control is needed to control the aircraft throughout the airspeed range down to the stall.

Croatia Airlines losses swell

Passengers stable- finances trembling
Croatia Airlines has seen its losses soar. On Wednesday the airline reported that it ended the first 9 months of the year with a net loss of 94.2 million Kunas or 12.88 million Euros. During the same period last year, the airline reported losses of 22.2 million Kunas or 3 million Euros. Croatia Airlines’ operating earnings also fell by 18%. This is despite Croatia Airlines’ cost cutting measures, which were introduced earlier in the year. The Croatian national carrier has, unlike most European carriers, managed to keep its passenger numbers stable in spite of the global financial crisis. However, this did little to save the airline’s finances.

The other 2 main airlines in the region, Adria and Jat also reported losses with the latters amounting to 11 million Euros for the first 9 months while Adria has reported some improvement with its figures.

Despite the grim news, Croatia Airlines has announced that it will prolong its seasonal Split to London service until the end of November. After the winter break, the service will recommence in March.

Effect of Weight on Stability and Controllability

Overloading also affects stability. An aircraft that is stable and controllable when loaded normally may have very different flight characteristics when overloaded. Although the distribution of weight has the most direct effect on this, an increase in the aircraft’s gross weight may be expected to have an adverse effect on stability, regardless of location of the CG. The stability of many certificated aircraft is completely unsatisfactory if the gross weight is exceeded.

Effect of Weight on Aircraft Structure

The effect of additional weight on the wing structure of an aircraft is not readily apparent. Airworthiness requirements prescribe that the structure of an aircraft certificated in the normal category (in which acrobatics are prohibited) must be strong enough to withstand a load factor of 3.8 Gs to take care of dynamic loads caused by maneuvering and gusts. This means that the primary structure of the aircraft can withstand a load of 3.8 times the approved gross weight of the aircraft without structural failure occurring. If this is accepted as indicative of the load factors that may be imposed during operations for which the aircraft is intended, a 100-pound overload imposes a potential structural overload of 380 pounds. The same consideration is even more impressive in the case of utility and acrobatic category aircraft, which have load factor requirements of 4.4 and 6.0, respectively.

Structural failures which result from overloading may be dramatic and catastrophic, but more often they affect structural components progressively in a manner that is difficult to detect and expensive to repair. Habitual overloading tends to cause cumulative stress and damage that may not be detected during preflight inspections and result in structural failure later during completely normal operations. The additional stress placed on structural parts by overloading is believed to accelerate the occurrence of metallic fatigue failures.

Knowledge of load factors imposed by flight maneuvers and gusts emphasizes the consequences of an increase in the gross weight of an aircraft. The structure of an aircraft about to undergo a load factor of 3 Gs, as in recovery from a steep dive, must be prepared to withstand an added load of 300 pounds for each 100-pound increase in weight. It should be noted that this would be imposed by the addition of about 16 gallons of unneeded fuel in a particular aircraft. FAA-certificated civil aircraft have been analyzed structurally and tested for flight at the maximum gross weight authorized and within the speeds posted for the type of flights to be performed. Flights at weights in excess of this amount are quite possible and often are well within the performance capabilities of an aircraft. This fact should not mislead the pilot, as the pilot may not realize that loads for which the aircraft was not designed are being imposed on all or some part of the structure.

In loading an aircraft with either passengers or cargo, the structure must be considered. Seats, baggage compartments, and cabin floors are designed for a certain load or concentration of load and no more. For example, a light plane baggage compartment may be placarded for 20 pounds because of the limited strength of its supporting structure even though the aircraft may not be overloaded or out of CG limits with more weight at that location.

Effect of Weight on Flight Performance

The takeoff/climb and landing performance of an aircraft are determined on the basis of its maximum allowable takeoff and landing weights. A heavier gross weight results in a longer takeoff run and shallower climb, and a faster touchdown speed and longer landing roll. Even a minor overload may make it impossible for the aircraft to clear an obstacle that normally would not be a problem during takeoff under more favorable conditions.

The detrimental effects of overloading on performance are not limited to the immediate hazards involved with takeoffs and landings. Overloading has an adverse effect on all climb and cruise performance which leads to overheating during climbs, added wear on engine parts, increased fuel consumption, slower cruising speeds, and reduced range.

The manufacturers of modern aircraft furnish weight and balance data with each aircraft produced. Generally, this information may be found in the FAA-approved AFM/POH and easy-to-read charts for determining weight and balance data are now provided. Increased performance and load-carrying capability of these aircraft require strict adherence to the operating limitations prescribed by the manufacturer. Deviations from the recommendations can result in structural damage or complete failure of the aircraft’s structure. Even if an aircraft is loaded well within the maximum weight limitations, it is imperative that weight distribution be within the limits of CG location. The preceding brief study of aerodynamics and load factors points out the reasons for this precaution. The following discussion is background information into some of the reasons why weight and balance conditions are important to the safe flight of an aircraft.

In some aircraft, it is not possible to .ll all seats, baggage compartments, and fuel tanks, and still remains within approved weight or balance limits. For example, in several popular four-place aircraft, the fuel tanks may not be .lled to capacity when four occupants and their baggage are carried. In a certain two-place aircraft, no baggage may be carried in the compartment aft of the seats when spins are to be practiced. It is important for a pilot to be aware of the weight and balance limitations of the aircraft being flown and the reasons for these limitations.

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