107

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 ...


92

This is how I explain it! 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: This is my actual path traveled over ...


79

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 ...


79

At uncontrolled airports, there is rarely enough traffic for signals to be needed, and pilots should (though are not required to) communicate with each other on CTAF—an option that cars do not have. In the air, if you're close enough to see a turn signal, you are way too close and need to immediately follow the collision avoidance procedure. More generally, ...


77

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


73

I would recommend that you don't introduce the term first and then try to explain it verbally, but demonstrate it in an interactive, hands-on practical way instead. Bring a globe, a flat map, and a piece of string to your next meeting. Have the cadets pick a departure and destination city pair. New York to Tokyo might be a good choice, because the effect ...


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 ...


65

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 ...


64

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 ...


58

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 ...


53

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 ...


52

I think the points raised in other answers are good, but they miss the essential difference. Cars choose from a discrete set of options, but planes do not. When you indicate left when driving you are communicating to other traffic that either you are taking the next left turn, or that you're changing lanes (depending on context). In some situations the exact ...


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 ...


43

GPS faster? Yes and no GPS is faster depends on which case we want to consider: Cold start, restart or operational use. Cold start, like for example the first time we use the instrument: Inertial reference systems (IRS) are faster than GPS to deliver the first fix (TTFF): Less than 10 minutes (alignment) against 12.5 minutes for the GPS, the time to receive ...


40

How is TACAN different from the VHF Omnidirectional Range (VOR) system? A very short question, but the answer calls for describing several techniques which are by themselves difficult to summarize without taking liberties with reality, so the post is rather long and should be read by sections of interest rather than totally at once. And for those not ...


39

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 ­...


36

Short answer Aircraft still use inertial navigation systems because INS is autonomous, it doesn't need any external support to work, it provides more information, and is more accurate than a GNSS in the short term. 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 ...


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, ...


34

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 a really good one. The depth of modulation is the ratio between the modulation amplitude and the carrier amplitude. ...


34

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 ...


30

It only takes 3 satellites for a GPS fix (4 if you want altitude). There are 31 operational 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 ...


29

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 ...


29

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 and attitude). The INS feeds into the flight ...


28

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


27

You sure can! It's not really done all too much any more in the days of GPS but it was done quite a bit in the early days of aviation. Historically, this was done by the "flight navigator" a position that no longer really exists. Some aircraft even had mounted sextants. (source) Here is a video of it being done in practice (fanta optional) This was even ...


26

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 ...


25

Short answer Do you find the null position, then assume it's 90 degrees from the beacon? That's correct. For the antenna pattern shown in the question, the angle between direction of nulls and peaks is 90°. When sensing a null (or a peak) there are two possible and opposite directions for the beacon. This ambiguity has to be removed. This could be done by ...


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 ...


23

Isn't it supposed that an airway has always the same magnetic course between navaids? No. The course depends on where you plot it from. That's a random RNAV airway I picked, it has two headings, 114° and 298°, and the difference is not 180°, it's 184°, so over the course of 112 nm there is a 4° shift. That's due to the curvature of the Earth. Consider ...


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