VOR tracking beacons

VORs are assigned radio channels between 108.0 MHz (megahertz) and 117.95 MHz (with 50 kHz spacing); this is in the VHF (very high frequency) range. The first 4 MHz is shared with the ILS band (See Instrument landing system). To leave channels for ILS, in the range 108.0 to 111.95MHz, the 100 kHz digit is always even, so 108.00, 108.05, 108.20, and so on are VOR frequencies but 108.10, 108.15, 108.30, and so on, are reserved for ILS.
The VOR encodes azimuth (direction from the station) as the phase relationship of a reference and a variable signal. The omni-directional signal contains a modulated continuous wave (MCW) 7 wpm Morse code station identifier, and usually contains an amplitude modulated (AM) voice channel. The conventional 30 Hz reference signal is on a 9960 Hz frequency modulated (FM) subcarrier. The variable amplitude modulated (AM) signal is conventionally derived from the lighthouse-like rotation of a directional antenna array 30 times per second. Although older antennas were mechanically rotated, current installations scan electronically to achieve an equivalent result with no moving parts. When the signal is received in the aircraft, the two 30 Hz signals are detected and then compared to determine the phase angle between them. The phase angle by which the AM signal lags the FM subcarrier signal is equal to the direction from the station to the aircraft, in degrees from local magnetic north, and is called the "radial."
This information is then fed to one of four common types of indicators:

1. An Omni-Bearing Indicator (OBI) is the typical light-airplane VOR indicator^[3] and is shown in the accompanying illustration. It consists of a knob to rotate an "Omni Bearing Selector" (OBS), and the OBS scale around the outside of the instrument, used to set the desired course. A "course deviation indicator" (CDI) is centered when the aircraft is on the selected course, or gives left/right steering commands to return to the course. An "ambiguity" (TO-FROM) indicator shows whether following the selected course would take the aircraft to, or away from the station.
2. A Horizontal Situation Indicator (HSI) is considerably more expensive and complex than a standard VOR indicator, but combines heading information with the navigation display in a much more user-friendly format, approximating a simplified moving map.
3. A Radio Magnetic Indicator (RMI), developed previous to the HSI, features a course arrow superimposed on a rotating card which shows the aircraft's current heading at the top of the dial. The "tail" of the course arrow points at the current radial from the station, and the "head" of the arrow points at the reciprocal (180 degrees different) course to the station.
4. An Area Navigation (RNAV) system is an onboard computer, with display, and up-to-date navigation database. At least two VOR stations, or one VOR/DME station is required, for the computer to plot aircraft position on a moving map, or display course deviation relative to a waypoint (virtual VOR station).

D-VORTAC TGO (TANGO) Germany

In many cases, VOR stations have co-located DME (Distance Measuring Equipment) or military TACAN (TACtical Air Navigation) — the latter includes both the DME distance feature and a separate TACAN azimuth feature that provides military pilots data similar to the civilian VOR. A co-located VOR and TACAN beacon is called a VORTAC. A VOR co-located only with DME is called a VOR-DME. A VOR radial with a DME distance allows a one-station position fix. Both VOR-DMEs and TACANs share the same DME system.
VORTACs and VOR-DMEs use a standardized scheme of VOR frequency to TACAN/DME channel pairing so that a specific VOR frequency is always paired with a specific co-located TACAN or DME channel. On civilian equipment, the VHF frequency is tuned and the appropriate TACAN/DME channel is automatically selected.

Seaweed as jet fuel

For airlines, the solution to soaring fuel prices might be as simple as seaweed.
Virgin Atlantic, Air New Zealand, and Boeing are working together to create the world’s first green aviation fuel made from pond-grown algae.
Higher fuel prices and growing concerns over environmental damage caused by conventional aviation fuel are driving plans to produce biofuels based on algae.
Virgin’s Sir Richard Branson says that the concept has “huge potential,” adding, that it’s a source of energy that “doesn’t lead to deforestation or take away land or water from the cultivation of essential food crops.”
Why algae? Scientists say it can grow incredibly fast – doubling in size in a few hours – and it does not need fresh water or good quality land.
Thick green algae produces at least 15 times more oil per hectare than alternatives such as palm oil, soya or jatropha, a nut-bearing shrub cultivated in several countries as a biofuel.
Separately, Continental Airlines, Boeing, and GE Aviation is hoping to flight test a type of biofuel in 2009. Green Car Congress reported in March that green fuels are ready for takeoff.

The Continental Airlines biofuel flight will use a Boeing Next-Generation 737 equipped with CFM International CFM56-7B engines, using a blend of between 20%-50% of a second-generation biofuel in one engine.

Although they have yet to select the type of biofuel to use, the partners say that it will be a second-generation fuel that does not impact food production. It will also be able to be produced in sufficient quantities to support a pre-flight test schedule that includes laboratory and ground-based jet engine performance testing to ensure compliance with stringent aviation fuel performance and safety requirements.
In February 2008, Virgin Atlantic, Boeing, GE Aviation, and Imperium Renewables successfully flight-tested a Boeing 747 equipped with GE engines using a 20 percent blend of a biojet fuel—a transesterified bio-kerosene — derived from babassu and coconut oil in one engine.
This sounds good. But with fuel prices likely to fall now that Saudi Arabia has decided to increase oil production, will these alternative fuel initiatives endure?
Only time will tell.

Two missing planes

Five helicopters, including an SA Air Force Oryx, which was dispatched from the Hoedspruit Airforce Base, lifted off at about 40 minute intervals throughout the afternoon, searching in vain in mountainous terrain.
By 5pm yesterday, the search was called off.
"They are currently rerouting the helicopters to the centre and there has been no indication of a crash site yet,"Greater Mopani District Municipality spokesperson Mashadi Mathosa said.
At about 4.30pm, the Oryx left with a team of four search and rescue members on board, taking another stab at finding the two Albatros aeroplanes.
On its return, rescue team members, of whom many had to sleep in the veld overnight on Sunday, were fed dinner and coffee.
They were debriefed and had the night to rest, before regrouping to start the search at 6.30am.
Yesterday's search and rescue efforts continued in an atmosphere of tense efficiency, as every bit of information coming in to the centre was plotted on a map, and coordinates of any possible sighting sent to a helicopter.
The helicopter then swooped down to pick up a team of four rescuers, and headed out to the search areas, where the teams were dropped to search on foot.
The search included more than 100 members from various organisations such as the Limpopo Emergency Services, the SAAF, police, the Off Road Rescue and Mountain Rescue units and private pilots. It stretched over an area of between 180km² and 210km² in mountainous and vegetated terrain between Maake and George's Valley in the Wolkberge.
Low cloud cover and heavy fog limited visibility to about 10m, and caused the helicopters to be ineffective as search platforms, and could only be used to ferry search teams.
Aviation authorities lost contact with the two Albatros aircraft, confirmed to be carrying 13 passengers, at around 3pm on Sunday.
The planes were returning to Rand Airport from an airshow organised at the Tarentaal airstrip, about 15km outside Tzaneen.

Tire blowout!!!

Yesterday i was sitting in the office when i recieved a call from Neil one of the instructors here at Zero four, He said he had a burst tire on landing when he landed at port st Johns airfield which is around  an hours flying time away. Upon further disscussion on the matter it was decided that i would fly to Port st Johns with a spare tire, an engineer and a saftey pilot because of the intense wind. We arrived at the airfield and i set up an approach for landing, just before the start of the runway the wind gusted and pushed the plane sideways so i aborted landing and did a go around. On the second try i managed to get the plane alot straighter than before although the plane was still very skew, just before the start of the runway the wind changed direction and was now behind me, it pushed the plane forwards and gained a substantial amount of speed. I put the plane down as fast as I could and tried to slow the plane down before the end of the runway, on the other side of which was a 500m drop off a cliff.

I managerd to slow the plane down in time and we unloaded the spare tire and got the other plane going again, so it was an eventful day had by all but Port st Johns still remains a very tricky and dangerous runway when it comes to windy days.

One of the extraordinary sights associated with this supersonic transition is the production of a sudden visible vapor cloud around the aircraft. The report of the photographers is that they snap the shutter when they hear the sonic boom, which certainly associates the cloud with the breaking of the sound barrier. But the photo of the B-2 below, which is slightly subsonic, blurs that distinction. It seems safe to say that the phenomenon is associated with the extraordinary conditions very near the speed of sound. Mark Cramer describes this condensation effect in terms of the Prandtl-Glauert Singularity. In this phenomenon, the non-linear or "chaotic" effects amplify all pressure perturbations, leading to some regions of anomalously high and low pressure. If the associated volumes cannot quickly change, then the ideal gas law suggests that the temperature in the low pressure regions must drop, leading to condensation of the water vapor present. This general description probably applies, even though in the presence of condensation, the gases are not exactly "ideal".
The photo credit is Photographer's Mate Airman Chris M. Valdez, Navy NewsStand -- Eye on the Fleet Photo Gallery ( http://www.news.navy.mil/view_photos.asp, 040129-N-0905V-024).
F14-B Tomcat Fighter Jet, United States Navy, Mediterranean Sea, April 22, 2003

Load video of F-14

Photo credit:Photographer's Mate Airman Justin S. Osborne, Navy NewsStand -- Eye on the Fleet Photo Gallery ( http://www.news.navy.mil/view_photos.asp, 030422-N-0382O-588).
F/A-18 Hornet Fighter Jet, United States Navy, off the coast of Pusan, Taehan-min'guk - Republic of Korea, July 7, 1999Photo credit: Ensign John Gay, Navy NewsStand -- Eye on the Fleet Photo Gallery ( http://www.news.navy.mil/view_photos.asp, 990707-N-6483G-001).
This photo of the B-2 Spirit Stealth Bomber, which does not break the sound barrier, shows that the extraordinary cloud effect is not exactly tied to the breaking of the sound barrier. The aircraft was completing a mission over the Pacific Ocean.
This photo is credited to Bobbi Garcia, a civilian aerial photographer working for Rohmann Services in support of the Air Force Flight Test Center (AFFTC). It appeared in the December 30, 2002 issue of Aviation Week and Space Technology.
General references for the top three photos and many others: United States Navy (USN, http://www.navy.mil ), United States Department of Defense (DoD, http://www.DefenseLink.mil or http://www.dod.gov), Government of the United States of America (USA).

Sound barrier

Air Navigation and the point of no return

The first step in navigation is deciding where one wishes to go. A private pilot planning a flight under VFR will usually use an aeronautical chart of the area which is published specifically for the use of pilots. This map will depict controlled airspace, radio navigation aids and airfields prominently, as well as hazards to flying such as mountains, tall radio masts, etc. It also includes sufficient ground detail - towns, roads, wooded areas - to aid visual navigation. In the UK, the CAA publishes a series of maps covering the whole of the UK at various scales, updated annually. The information is also updated in the notices to airmen, or NOTAMs.
The pilot will choose a route, taking care to avoid controlled airspace that is not permitted for the flight, restricted areas, danger areas and so on. The chosen route is plotted on the map, and the lines drawn are called the track. The aim of all subsequent navigation is to follow the chosen track as accurately as possible. Occasionally, the pilot may elect on one leg to follow a clearly visible feature on the ground such as a railway track, river, highway, or coast.

Adjustment of an aircraft's heading to compensate for wind flow perpendicular to the ground track

When an aircraft is in flight, it is moving relative to the body of air through which it is flying; therefore maintaining an accurate ground track is not as easy as it might appear, unless there is no wind at all — a very rare occurrence. The pilot must adjust heading to compensate for the wind, in order to follow the ground track. Initially the pilot will calculate headings to fly for each leg of the trip prior to departure, using the forecast wind directions and speeds supplied by the meteorological authorities for the purpose. These figures are generally accurate and updated several times per day, but the unpredictable nature of the weather means that the pilot must be prepared to make further adjustments in flight. A general aviation (GA) pilot will often make use of either the E6B flight computer - a type of slide rule - or a purpose-designed electronic navigational computer to calculate initial headings.
The primary instrument of navigation is the magnetic compass. The needle or card aligns itself to magnetic north, which does not coincide with true north, so the pilot must also allow for this, called the magnetic variation (or declination). The variation that applies locally is also shown on the flight map. Once the pilot has calculated the actual headings required, the next step is to calculate the flight times for each leg. This is necessary to perform accurate dead reckoning. The pilot also needs to take into account the slower initial airspeed during climb to calculate the time to top of climb. It is also helpful to calculate the top of descent, or the point at which the pilot would plan to commence the descent for landing.
The flight time will depend on both the desired cruising speed of the aircraft, and the wind - a tailwind will shorten flight times, a headwind will increase them. The E6B has scales to help pilots compute these easily.
The point of no return, sometimes referred to as the PNR, is the point on a flight at which a plane has just enough fuel, plus any mandatory reserve, to return to the airfield from which it departed. Beyond this point that option is closed, and the plane must proceed to some other destination. Alternatively, with respect to a large region without airfields, e.g. an ocean, it can mean the point before which it is closer to turn around and after which it is closer to continue. Similarly, the Equal time point, referred to as the ETP (also Critical point(CP)), is the point in the flight where it would take the same time to continue flying straight, or track back to the departure aerodrome. the ETP is not dependant on fuel, but wind, giving a change in ground speed out from, and back to the departure aerodrome. In Nil wind conditions, the ETP is located halfway between the two aerodromes, but in reality it is shifted depending on the windspeed and direction.
The aircraft that is flying across the Ocean for example, would be required to calculate ETPs for one engine inoperative, depressurization, and a normal ETP; all of which could actually be different points along the route. For example, in one engine inoperative and depressurization situations the aircraft would be forced to lower operational altitudes, which would affect its fuel consumption, cruise speed and ground speed. Each situation therefore would have a different ETP.
Commercial aircraft are not allowed to operate along a route that is out of range of a suitable place to land if an emergency such as an engine failure occurs. The ETP calculations serve as a planning strategy, so flight crews always have an 'out' in an emergency event, allowing a safe diversion to their chosen alternate.
The final stage is to note which areas the route will pass through or over, and to make a note of all of the things to be done - which ATC units to contact, the appropriate frequencies, visual reporting points, and so on. It is also important to note which pressure setting regions will be entered, so that the pilot can ask for the QNH (air pressure) of those regions. Finally, the pilot should have in mind some alternative plans in case the route cannot be flown for some reason - unexpected weather conditions being the most common. At times the pilot may be required to file a flight plan for an alternate destination and to carry adequate fuel for this. The more work a pilot can do on the ground prior to departure, the easier it will be in the air.