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104

Several of the hijackers, including Mohamed Atta, held at least private pilot certificates and had undergone ATP level jet training in DC9 and 737 full motion simulators in December of 2000. Atta himself held a commercial license with instrument and multi engine ratings. They were well versed in aerial navigation techniques and more than capable of ...


78

The direct route you show is actually only a straight line on your map projection. The surface of the Earth is curved and the straight line between London Heathrow and New York JFK looks like this (courtesy of greatcirclemapper.net): That still does not quite get you over Scotland, but the actual flight path over the Atlantic typically uses a North Atlantic ...


74

This is how I explain it, hopefully it helps more than hinders! Heading: This is where my nose points - and seeing as my nose is attached to my head, this is where my head (and thus my machine) is pointing relative to North. Course: This is my INTENDED path of travel that I have calculated taking into consideration winds, variation and declination. Track: ...


69

When aircraft fly inside clouds, they fly under "instrument" rules. It doesn't matter whether the visibility is reduced (e.g. at night) or totally blocked (in a thick cloud), this mode of flying simply assumes the crew has no external visual reference, they fly using appropriate indications given by on-board instruments. The following short video shows a ...


69

The pilots in this case did know where they were going: Edinburgh. BA said a paperwork error was to blame, with the pilot following orders from Germany, where WDL’s head office had filed the incorrect flight plan. The pilots flew according to the flight plan they were given, and ATC happily routed their plane along that flight plan as well. The pilots had ...


61

Airways simply allow for better management of traffic. Imagine for a moment that everyone had an off-road capable car, if all the drivers were going "GPS Direct" to their destination how would drivers ensure separation? How would you avoid hitting other cars if there were no roads? Airways are the aviation solution to this problem: Defined routes between ...


60

If an aircraft is following a magnetic course changes in magnetic declination as the aircraft moves along its route of flight will affect the true course, and on a long flight such as the hypothetical trip posed here we need to take that into account. Magnetic declination is empirical data, i.e. there are tables of it, and while formulas exist to ...


55

All of the hijacked flights were going in different directions and had to be piloted to a different destination. The hijacker pilots had different degrees of success in doing this. The flight paths they took are shown in this map published by the FBI: Mohamed Atta, the ringleader of the effort, was a licensed commercial pilot received significant simulator ...


49

Ooh, a celestial navigation question...about airplanes... I never thought I'd see one of these in the 21st century! To answer the basic question: Pilot training doesn't cover sextant use, but there is still a "Flight Navigator" certificate (you'll find it in Part 63 of the FARs), and an associated Flight Navigator Handbook (FAA-H-8083-18), last updated in ...


43

Can a sextant be used while flying? Yes it can. Some aircraft like 747 for example had a sextant port to allow celestial navigation. How accurate/reliable is a sextant, both standing still and at 500+ mph? Sextant is not accurate. At least not accurate enough for today's navigation purposes. You cannot perform a RNP-RNAV approach with a sextant. Per ...


36

This article from AA (titled "Over the Top" by Gerard J. Arpey) says, By the way, because of the limitations of older navigation systems, none of the polar routes we fly crosses exactly over the North Pole. At the Pole, an airplane’s compass changes from a due-north heading to due south, and that change of course could potentially lead to problems with ­...


35

Only in military applications nowadays, primarily helicopters as the system doesn't require the alignment process of the INS system, is not subject to GPS jamming, is very accurate when flying low (as opposed to high and fast over oceans), and most helicopters don't do the occasional barrel roll (the system is belly mounted to track the ground below). (Calm ...


34

If the GPS is unavailable, it will be quite an impact to the aviation industry. All airliners in-flight will experience degraded RNAV performance, but they would make it to the destination using VORs, DMEs and ILSs. For general aviation, things are not so lucky. The GPS display provides an excellent situation awareness in small aircrafts; without it, ...


33

Short answer Aircraft still use inertial navigation systems because INS is autonomous, it doesn't need any external support to work. There is no plan to stop using it. On the contrary, INS is required for certain operations. For instance the B787 cannot be flown without at least one IRU operative. See B787 Master Minimum Equipment List MMEL, item 21-01-01 ...


33

VFR aviation maps called "sectionals" (and now GPS map displays) depict the types of airspace through borders with different colors and dashed lines. You can buy or download the maps for free from this FAA site. It is always the responsibility of a pilot to know where they are and follow all applicable laws. In the US, a pilot that breaks a rule because ...


31

Short two-bullet answer (1) Differences between VOR/DME and TACAN include: TACAN uses UHF (VOR uses VHF) to increase bearing determination accuracy; a single frequency for range and bearing (VOR/DME uses two frequencies); two small rotating drums with parasitic antenna elements (VOR uses a large circular array of antennas). A VOR/DME station actually uses ...


31

In short The longer time required to align an inertial unit is the price to pay for its independency on any external equipment or signal, but Earth itself. A GPS receiver is faster, but is only one small piece in a huge system. The GPS ground segment (control and monitoring stations) and space segment (satellites) are necessary for the GPS receivers (user ...


29

The beam strength decreases as you move away from it's own centreline, so is it actually that the entire modulated signal strength decreases which when de-modulated is effectively a difference in amplitude modulation depth? Your question is very relevant, it can arise naturally if you happen to look at web pages using half correct descriptions (for ...


28

As of currently, the answer to this question is in principle no for commercial aircraft, at least not remotely. There are two parts to this: From a system perspective: Aircraft systems could probably be 'hacked'- assuming you could for instance screw up the flight computer by changing the chips in the belly- but there is no way you could really pull this ...


28

Looks like they were avoiding a storm system from Oregon north into Canada.


27

It only takes 3 satellites for a GPS fix (4 if you want altitude). There are 32 satellites currently in orbit and at any given time you can most likely receive a signal from half a dozen of them at least. That being said the chances of them failing completely is almost 0%. But of course what if they did, well... There is always the Russian version of GPS ...


26

Well, most airlines do cross the ocean with GPS in today's world. That being said, most (if not all) transcontinental airliners, and many flying domestic routes as well, have what's called an inertial navigation system (a form of dead-reckoning where gyros and accelerometers are used to compute changes in position). The INS feeds into the flight management ...


25

The ILS works using two components, a localizer and a glideslope. The frequencies for the localizer are between 108.1-111.95 MHz and the glide slope between 329.15-335.0 MHz. These frequencies are the carrier waves that the modulation you mention takes place upon. A pilot is only concerned with the localizer frequency as the navigation equipment knows the ...


24

The absolute minimum for a generalized vehicle that needs to know its position and attitude (orientation) in space is one per degree of freedom. This can be reduced if we have information about the natural modes of the system and their stability. For simplicity, let's assume a vehicle moving in 3 dimensions, that means a total of 6 DoF: 3 coordinates in ...


23

The delay is not 50 milliseconds, but 50 microseconds. It takes some time for the ground equipment to decode the incoming signal, decide it needs to reply, and fire up its transmitter. In order for the distance measurement to be reliable, this inevitable delay needs to be precisely defined and the same for all DME stations. It also gives the airborne ...


21

Over the North Atlantic, there are no predefined low-level or high-level airways as there are over the continents. In order for aircraft to get a tailwind for eastbound flights and get out of the wind for westbound flights, Canadian and UK air traffic control set tracks based on the expected wind conditions twice a day. The lines you are seeing are called ...


21

Inertial Navigation Systems, unlike other navigation systems, do not depend on external (radio) measurements. Instead an INS keeps track of its position by accurately measuring acceleration (accelerometers) and rotation (gyroscopes). It therefore works in remote areas where there are no ground based navaids available. Initially, the INS gets its position ...


21

Navigation has gotten much simpler over the years. Initially, navigation would be done by a combination of dead reckoning, looking out the window for landmarks, and for night or long-distance flights, by celestial navigation (many old airplanes have a window at the navigator's station specifically to let the navigator see the stars). This took quite a bit ...


21

Airliners do generally have GPS receivers, but GPS doesn't give you the information that's needed in this case. In AF 447, the primary consequence of the blocked pitot tubes was that the flight envelope protection system couldn't do its job properly and therefore automatically disengaged together with the autopilot. The subsequent crash was caused by the ...


21

Australia Brisbane / Melbourne FIRs boundary PUDYA SWEED LIPPS ALIDL CLOZA TOUDA PHONE (Put your sweet lips a little closer to the phone, Jim Reeves) Brisbane RWY19 STARs LEAKY BOATS SINNK and DRAIN PLUGG SINNK. BLAKA MOOVI by the South. Gold Coast (YBCG) SID 14/32 LUVLY MEETA MAIDS (Lovely meter maids) USA Frederick, Maryland (KFDK) RNAV (GPS) RWY 5 ...


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