44
votes
Accepted
Why does IRS alignment take so much time?
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 ...
- 80.9k
36
votes
Do today's aircraft still have INS (inertial navigation system)?
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 ...
- 80.9k
28
votes
Accepted
How do aircraft on the deck of a moving aircraft carrier align their INS/IRS?
The aircraft carrier has its own inertial navigation system, (SINS - Ship's Inertial Navigation System) and this information is transmitted to each individual aircraft INS by either cable or datalink.
...
- 27.3k
23
votes
How do missiles navigate and determine their orientation without GPS?
As per comments, this question is referring to guided weapons such as Stinger (IR guidance).
Guided missiles that acquire their target via signal return, such as infrared, radar or laser designation (...
- 30.5k
17
votes
Accepted
What's the difference between orientation and position?
Yes there is a distinction, pitch, roll and heading are angles [unit = radian] and latitude, longitude and altitude are linear distances [unit = meter]. Together, these six parameters define the six ...
- 62.9k
17
votes
Accepted
Is it possible to accurately measure airspeed without pitot tube?
Technically speaking, inertial measurements are not sufficient to derive airspeed. You need pressure measurement (or airspeed measurement, see LIDAR). Pitot-static probes are the most usual and ...
- 1,567
17
votes
Why are true headings followed above 73N in the northern hemisphere, whereas in the southern hemisphere the change is made at 60S?
Earth's magnetic field is not symmetric north to south. In particular, the magnetic declination can get significantly larger at a given southern latitude than it does at the corresponding northern ...
- 1,722
13
votes
Do today's aircraft still have INS (inertial navigation system)?
To answer the specific question on the 787, yes.
According to this article
Boeing 787 avionics overview
Rockwell Collins provides the flight deck display system, pilot
controls....Earth ...
- 102k
13
votes
Why did the Boeing 787 switch back to separate IRS systems?
There were also other practical end use issues as well. Having worked in the manufacturing and repair of theses fault tolerant units, one of the benefits was supposed to be the ability to plan ...
- 131
12
votes
Accepted
How do missiles navigate and determine their orientation without GPS?
Modern missiles pretty much all determine their orientation via some sort of IMU. Note that you do not need super-expensive RLG-IMU, but you might get away with cheaper MEMS-based IMUs (*1). However (...
- 5,044
11
votes
Is it possible to accurately measure airspeed without pitot tube?
Airspeed - not reliably under all circumstances. You need to feel that wind somewhere in order to get a direct and accurate measure of the speed of it, and the pitot tube is an accurate and proven ...
- 62.9k
11
votes
Accepted
Could airliners fetch data like AoA and speed from an INS?
An INS gives your speed & orientation in space, but without reference to what the airmass that you're flying in is doing.
The Pitot tube and AOA sensors give speed and pitch orientation in ...
- 53.7k
10
votes
Accepted
What makes inertial guidance unsuitable for auto-land?
Suitability for CAT III autoland requires much more than just accuracy. A big factor is system integrity which involves fault detection and alerting. Fault detection in autoland approved ILS/MLS/GLS ...
- 20.2k
10
votes
Accepted
Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS?
Could somebody explain a little bit why they need 2 separate GPS and 2 separate IRS?
So that if one fails, the other can still be used to complete the flight.
Airbus even have 3.
What is meant by ...
- 32.7k
9
votes
Do today's aircraft still have INS (inertial navigation system)?
Absolutely. Both intercontinental civil aircraft and military aircraft are equipped with GNSS updated solid state INS systems using ring laser gyros for positional detection and navigation.
- 75k
9
votes
What does "inertial" refer to in "inertial reference"?
It is called inertial, because it works by measuring—and integrating—inertial forces¹, that is forces due to acceleration of the reference frame (i.e. the aircraft). Gyroscopic effect used to measure ...
- 56.5k
8
votes
How does an air-data computer convert ram air pressure from the pitot tube into airspeed?
Usually there is an intermediate module ADM (air data module) that makes the conversion from analog pressure into digital numerical value. One ADM will do this for the ram air pressure, another ADM ...
- 1,807
7
votes
Do today's aircraft still have INS (inertial navigation system)?
Modern aircraft have an “inertial reference system”, which has the set of gyroscopes and accelerometers and is used to feed all systems that need those data.
The attitude, its rate of change, and ...
- 56.5k
7
votes
How do missiles navigate and determine their orientation without GPS?
To expand on the answer given by @Jpe61, homing missiles use a technique called 'Proportional Navigation'. It is a surprisingly simple algorithm in which the missile attempts to keep the target on a ...
- 423
7
votes
Accepted
How can a plane or an object gimbal lock itself?
You didn’t offer a quote from whatever text mislead you, but from a series of comments it appears that your question is based on a simple misunderstanding.
Aircraft and other objects cannot gimbal ...
- 27.3k
6
votes
Are the IMU velocities equivalent to the GPS ground velocity, except for the coordinate reference system?
An IMU uses gyro and accelerometer measurements to calculate its velocity vector relative to the Earth. Similarly, a GPS uses range, range-rate, doppler, and/or carrier phase shift measurements to ...
- 543
6
votes
What's the difference between orientation and position?
Position is where you are; orientation is which way you're pointing (including any roll).
- 12k
5
votes
Is it possible to accurately measure airspeed without pitot tube?
OP question answer: Yes, it is possible to much more accurately measure airspeed with Doppler lidar, than it is with a pitot /static system.
Discussion below:
I have used particle scattering and ...
- 17.8k
5
votes
Is it possible to accurately measure airspeed without pitot tube?
It is possible to think devices that could potentially replace Pitot tubes, while it is not very obvious how good they would operate under conditions of the real flight, for instance:
Compare ...
- 12.2k
5
votes
How does Kalman filtering work in inertial navigation systems?
A Kalman filter is used on all kinds of IRU's and INS's, even with airspeed information as in an ADIRU. A Kalman filter is just a general method (and a very useful one) for state estimation and ...
- 6,813
5
votes
Accepted
How does Kalman filtering work in inertial navigation systems?
First of all you should know that a Kalman filter is a state estimation technique. More than a filter, it is an estimator. Whilst it does filter sensor noise in the process, the most important use is ...
- 84.5k
5
votes
Accepted
How did KAL 007 get so far off course?
Chapter 4 of Degani's Taming HAL covers some of the details of this disaster, and is on a NASA site The Crash of Korean Air
Lines Flight 007
It details some of the interface deficiencies in the ...
- 6,081
5
votes
Why does the A320 IR2 MEL OPS procedure suggest to switch to ADR3?
Even if ADR and IR perform two independent and separate functions, they are the same hardware object (example). A IR2 malfunction is a malfunction: you do not know, in general, what is causing the ...
- 2,783
5
votes
Accepted
Can you fly with INS/ IRS at higher lattitudes?
Yes this would be possible. The limitation is for gyro-compassing only (alignment).
However being technically possible is only one aspect, there are associated regulations. Going into polar regions is ...
- 80.9k
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