Heatblur Simulations DCS: F-14A/A+/B Tomcat - Page 24 - ED Forums
 


Notices

Reply
 
Thread Tools Display Modes
Old 02-19-2018, 06:08 PM   #231
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default

Quote:
Originally Posted by Cobra847 View Post




The Tomcat has a new powerplant model!

While we’ve already undertaken the development of an engine model with the Viggen, we decided last year to completely redesign this portion of our simulation framework, in order to create an much more in-depth and realistic simulation of a turbofan engine. This will also help us in recreating the P&W TF-30 engines for the F-14A, as well as other turbofan, turbojet, or turboshaft engines for our future product lineup.

The F-14B is powered by two F110-GE-400 turbofan engines with variable exhaust nozzles and afterburner augmentation.They are dual-rotor engines consisting of a three-stage fan driven by a two stage, low-pressure turbine and a mechanically independent, aerodynamically balanced, nine-stage high-pressure compressor driven by a single-stage, air-cooled, high-pressure turbine. Engine operation is automatically regulated and maintained electrically by the augmenter fan temperature control unit and by throttle inputs to the main engine control.


This new F110 model has been built entirely from scratch, incorporating many new features and improving the accuracy and fidelity of the engine simulation. The following components of the engine have been modeled based on actual F110 engine data gathered from various sources:
  • Air Inlet Control System (AICS)
    The primary job of the AICS is to provide quality airflow to the engine in sufficient quantities to prevent engine operation issues. This involves a reduction of the speed of air entering the engine’s fan/compressor face. During this process, incoming freestream airflow is slowed and compressed. As a result, ram temperatures and pressures entering the engine are increased. On the F-14 this is achieved primarily by a system of 3 moving ramps per side that are scheduled based on flight conditions. During supersonic flight, these ramps are scheduled to move in a way that creates multiple shockwaves to more efficiently compress incoming air than a conventional duct would. The efficiency of the inlet’s pressure recovery throughout the flight envelope has been captured from real F-14 flight test data for use in the Heatblur F-14. Considerations for ramp actuator malfunctions have been made, which can include thrust loss and reduced stability margin (i.e. higher potential for compressor stall) if the ramps are out of their scheduled positions (i.e. high speed with the ramps in their stowed position...don’t do this!).
  • Augmenter Fan Temperature Controller/Main Engine Control (AFTC/MEC)
    The AFTC/MEC on the F-14 is similar to a FADEC (Full Authority Digital Engine Control) in function. It schedules fuel to the engine and afterburner based on numerous inputs. It also provides limiting functions to prevent engine damage and reduce risk of compressor stalls. RPM, EGT, and acceleration/deceleration are all limited by the AFTC to ensure safe engine operation. Other AFTC functions include engine start control, asymmetric thrust limiting, automatic relight, and fault detection. Fault detection automatically switches the engine control to secondary mode in the event of core overspeed, fan speed signal loss and other abnormal conditions. The AFTC/MEC simulation on the Heatblur F-14 takes in probe temperatures and pressures from the AICS, Mach number, pilot throttle positions, fan and core rpms, and engine ignition status, and outputs demanded fuel valve positions. These valve positions correspond to fuel flows that will cause the engine’s core to accelerate or decelerate as demanded by the pilot. While the pilot can demand a certain core speed, the AFTC is also constantly monitoring other engine parameters, such as N2 RPM and EGT to ensure that engine design limits are not exceeded and engine damage does not occur. Essentially, the AFTC protects the engine from the pilot while trying its best to give the pilot what he/she demands. When AFTC failures occur, the AFTC/MEC model reverts to what is known as secondary mode, in which the MEC governs N2 speed based on throttle inputs, but protection features such as EGT limiting are no longer available. Be aware that engine stall margin is decreased slightly at low rpm in this mode.
  • Fuel Metering Unit (FMU)
    The FMU consists of the system of valves and pumps responsible for carrying out AFTC fuel schedule demands. The AFTC outputs fuel valve position commands which in turn spray high pressure fuel into the combustor and afterburner when in use. The Heatblur F-14 model consists of a system of valves that open/close according to AFTC demands, as well as a shutoff valve for engine fires and automated shutdown commands coming from the AFTC. Failures such as stuck valves and clogged fuel filters may be implemented in the future.
  • Gas Generator (N2)
    The gas generator is the heart of any turbomachinery. Its primary purpose is to provide hot, high pressure air to the combustor. This is done by reducing the speed and increasing the pressure/temperature of the incoming inlet air even further, which the F110 can do at a pressure ratio of in excess of 30:1. The gas generator on the F110 is driven by a single stage high pressure turbine. The gas generator simulation in the Heatblur F-14 is robust, with the speed and acceleration of the core determined by fuel flow from the FMU, the speed of air entering the engine, and the inertia of the core itself. The amount of fuel introduced into the flow by the FMU directly corresponds to changes in torque applied to the power turbine, which in-turn changes the compressor speed as it is connected to the same spool. Failures such as compressor stalls (core airflow disturbances) may affect core speed, as well as any failures of upstream components that affect the fuel flow, such as AFTC/MEC or FMU failures.
  • Fan (N1)
    The fan on the F110 is driven by a two stage turbine, with a bypass duct that is mixed back in to the core flow in the afterburner section. The bypass ratio of the F110 is about 0.85. Low-bypass ratio turbofans such as the the F110 have the benefit of improved fuel economy at cruise speeds, while still maintaining very good high speed performance. This makes them excellent engines in fighter aircraft applications. The Heatblur F-14 fan simulation is driven as a function of core speed, with a given steady state core speed corresponding to a steady state fan speed. Any failures affecting the core will also affect fan speeds.
  • Combustor/Exhaust Gas Temperature Model
    The combustor section of the F110 ensures that high pressure fuel flow is efficiently ignited, dramatically increasing the temperature and pressure of the gases before the flow is expanded through power turbine section. The Heatblur F-14 combustor/EGT simulation is dependent on the amount of fuel being introduced into the engine, which is determined by the AFTC/MEC and FMU models.
  • Afterburner
    The afterburner on the F110 provides extra thrust by introducing additional fuel into the flow after the power turbine section. Fuel flow to the afterburner is controlled by the AFTC and AB Fuel Control (AFC), with its own set of high pressure fuel pumps that cycle fuel back to the engine boost pumps when afterburner is not in use. This ensures that high pressure AB fuel is available at all times to prevent thrust lags and surges when AB is initiated. The Heatblur F-14 afterburner simulation is purely dependent on available AB fuel flow and throttle position, with the extra thrust as a function of AB fuel flow and nozzle position. Failures to the AFTC/MEC, AB fuel pump failures, or exhaust nozzle failures will affect AB operation and performance. AB operation is inhibited when in AFTC/MEC secondary mode.
  • Starting System
    The engine start system is a turbine powered either by a ground air/power cart or via a crossbleed start from the opposite engine. Ground power can achieve approximately 30% N2 before light-off. In our F-14 starter simulation, the ENG CRANK switches open pneumatic valves allowing the ground cart air to begin spool-up of the core. As the core spins up, the MEC primes the engine with fuel and provides ignition and fuel control up to 59% N2 RPM.
  • Variable Exhaust Nozzle
    The variable exhaust nozzle is responsible for controlling the expansion of exhaust flow downstream of the afterburner section. Engine exhaust gases at higher thrust settings are discharged through the nozzle throat at sonic velocity and are accelerated to supersonic velocity by the controlled expansion of the gases. Varying nozzle throat area controls fan stall margin, which optimizes performance. The Heatblur F-14’s nozzle simulation is dependent on Mach number, altitude, throttle position, weight on wheels, engine oil pressure, and AB operation status. Failures in the nozzle will affect engine thrust and stability.


We’re still working on completing our engine simulation. In particular some of the remaining items to be completed pre and post early access include the:

  • Engine Oil System
  • Bleed Air Draw Effects
  • Generator Load Effects
  • AICS Anti-Ice and Icing Effects
  • AFTC/MEC Secondary Mode Effects
  • Reduced Arrestment Thrust System (RATS)
  • Asymmetric Thrust Limiting
  • Afterburner Ignition System
  • Throttle Control Modes (Approach Power Compensator already complete)
  • Windmill and Cross-start failures and effects
  • Battle Damage Effects
  • FOD Effects


This new engine modeling will serve as a robust and deep base for all of our future jet aircraft simulation. An accurate recreation of the aircraft’s powerplant and all of the follow on effects is important, as it allows us to more accurately depict common F-14 flight characteristics, failure states and especially dangerous situations arising from engine related issues. These effects will become even more apparent as we simulate the TF-30 engines as found in the F-14A. Be gentle with those throttles!

Below are a couple of exports from our engine diagnostic interface. The descriptions above each column describe the conditions in which the snapshot of data was taken in.



Click to enlarge


Thanks for reading!
Heatblur Simulations F-14 Team

Bye
Phant
__________________
phant is offline   Reply With Quote
Old 03-22-2018, 06:48 PM   #232
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default



Quote:
Using autolase script on a target, F-14 comes in low with GBU-12, designates CCRP target area visually on HUD, climbs for a loft toss then breaks away after releasing.

Disclaimer: potato graphics settings, placeholder 3D/2D art, no video editing or post-processing.

Bye
Phant
__________________
phant is offline   Reply With Quote
Old 03-22-2018, 11:41 PM   #233
Viper79
Senior Member
 
Viper79's Avatar
 
Join Date: Aug 2013
Location: Taranto - Puglia - Italy
Posts: 1,073
Default



















Fonte FB: https://www.facebook.com/heatblur/posts/862749253912694
__________________

CPU i5 4690k@4.4ghz | COOLER CM MasterLiquid lite 240 | MB Asrock z97 pro4 | RAM 16GB G.Skill Sniper DDR3 1866@2000 mhz | GPU MSI GTX 1070 Armor OC | SSD Samsung M.2 860 EVO 250 + Kingston ssdNow 240GB | HDD 500GB x3 meccanici | PSU Coolermaster GX650W 80 plus bronze | SO Windows 10 pro 64bit | TrackIR 5 | Logitech X56 Rhino | Logitech DFGT

"Mai discutere con un idiota, ti trascina al suo livello e ti batte con l'esperienza" cit. Oscar Wilde
Viper79 is offline   Reply With Quote
Old 04-01-2018, 12:37 PM   #234
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default

Quote:
Originally Posted by Cobra847 View Post





Dear All,

We’d like to wish you all a very happy easter weekend!

Since our last update, we’ve been working hard on finalizing several high level systems and fulfilling major milestones due in March.
We’ve reached many of our goals, but full completion of our March roadmap was hampered by a variety of factors, and a higher than expected non-development task loading.
None of these really come as a surprise in a dynamic development environment; but it does mean that we’ve had to burn the midnight oil and have had to spend much less time than expected on updating you on our progress - and especially so with fancy eye candy.

In detail, some of the progress made in March revolves around the following areas:

AN/ARC-182 & AN/ARC-159 Radios:
While these have been partially done for a long time, we’ve now gone back and brought these systems to full completion. Specifically, we’ve added:
  • The ability to read channel presets from mission settings and set these presets in the cockpit.

  • Synchronized remote displays between front and rear cockpits (each crew member only controls one radio, but receives readouts for both).

  • Completed the intercom and audio warning system, including four independent sound amplifiers and volume controls for different sound sources. Not all tones are generated by default at both stations, but a crew member can listen to the tones from the other cockpit by selecting different sound amplifier.
  • New failure states for each radios and associated transmission/receiving equipment.
One important aspect of DCS multiplayer is communication, and we decided to invest time into making the F-14 radios fully Simple Radio capable out of the box, with ICS, Radio transmission/receiving, pre-defined channels and KY-28 encryption all integrating with and communicating with SimpleRadio. Hot and Cold mic positions are supported for the intercom systems, and the SimpleRadio plugin functions are fully controllable through the F-14 cockpit.

Our hope is, that those of you running SimpleRadio in our squadrons and multiplayer environments will find the experience of transitioning to the F-14 smooth and painless, especially on the communication front. Special thanks to Ciribob, the creator of SRS for being supportive in ensuring smooth F-14 SRS support!

New F-110 Engine Model:
In late February, we revealed that we’ve been working on an entirely new, modularized jet propulsion model for the F-14 and future projects. If you haven’t read that update; you can find it here: https://forums.eagle.ru/showthread.php?t=203063

Since then, we’ve continued work on our engine model and integrating it into the F-14.

Minor engine updates include improvements to the afterburner fuel control and additional AFTC functionality.
Over the next few weeks, AFTC functionality such as RATS and Asymmetric Thrust limiting will be completed, as well as implementation of the last minor engine-related cockpit animations such as warning lights. After that, off-nominal cases such as flame out, compressor stall and battle damage will be added, essentially bringing the engine model to a fully complete state.

Major updates completed include implementing inlet spillage and lip suction (haha) drag effects based on real F-14 inlet wind tunnel test data.
This spillage drag/lip suction effect can be thought of as the force generated by air that the engine/inlet cannot ingest and must be “pushed” out of the way or around the sides of the inlet cowl, the profile drag of the cowl itself, and the friction drag of the air passing through the inlet duct and its interaction with the AICS ramp surfaces. Inlet drag is a function of mach, streamtube capture area, engine air mass flow (aka power setting), and AICS ramp position.

This drag data allowed the team to compute highly accurate installed net thrust, which in turn revealed that some previous FM drag tuning which slightly deviated from wind tunnel data was no longer needed. Level flight acceleration, fuel burn, and top speeds are now very close to published values.
Thrust is at the heart of any fighter jet - and ensuring accurate engine performance within a few percent of stated values is incredibly important to us.

We’ll go into much more detail on our engine simulation in upcoming videos.
New Kneeboard Functionality:
In order to facilitate the changing of various aircraft parameters while on the ground near ground crew, we decided to implement an “interactive” kneeboard to help you tweak these settings in a multiplayer environment. In particular; you can configure things like laser codes, M61 Vulcan gun burst lengths and KY encryption keys.
These settings will only be available near ground crew (or on the carrier) - and of course in the mission editor.
Navigation:
During the last month, we’ve entirely revised our modeling of the F-14’s INS (Inertial Navigation System) and associated subsystems.

This includes an overhaul of the INS (AN/ASN-92) and associated AWG-9, CSDC, AHRS and CADC functions.
In particular, we’ve also created an entirely new model for the IMU (Inertial Measurement Unit) which will offer a far more authentic simulation of limited precision of the INS.

We’ll be elaborating on this system next week.

Tying in with the Navigation system is a lot of finalization work on the navigation features of the RIO-centric user interfaces in the rear cockpit.
The F-14 includes plenty of complex and useful navigational functionality that will allow you, together as a crew, to better strike targets and fly your missions.
Much of this work mirrors functionality found in e.g. the Viggen; but turned up to 11 and involving many more subsystems (such as A-A radar and TCS).
Sound:
As the Artwork development process for the F-14 begins to draw to a close; we’ve now begun the process of designing the final soundscape of the F-14 module, starting with the F-110 engined F-14B.

Both the F-14B and -A will use fully authentic sounds, recorded directly from the appropriate engine type.
We’ve also sourced real, in-service F-14 sounds for everything from canopy sounds, engine starts, avionics and anything else you can think of giving off audible cues during aircraft operation.
While scanning and researching the F-14’s we had access to in the United States, we took the opportunity to record practically every single switch, level or control in the cockpit.

While we’re fairly satisfied with the audio design in the Viggen module (bar some bugs!) - we believe we can do much better, and we aim to make the F-14’s soundscape, both inside and out, the best yet.

Here’s a quick, heavily work in progress video of the exterior soundsets!

One of our main objectives in March has been to complete the tuning and tweaking of our Flight Model.
March has seen great focus on refining our low and high speed handling, and coaxing out unique flight characteristics at the edge of or beyond the standard flight envelope, such as aileron rolling reversal at appropriate angles of attack and lateral rudder usefulness at similar flight envelopes. It sounds like we’re repeating ourselves, and that’s because we are.
Tweaking and tuning a flightmodel is an incredibly time intensive and long process - hence it will likely continue right up until the day of release.

Getting the unique characteristics of the F-14 just right has required us to work closely with F-14 subject matter experts.
To date, we've had the pleasure of having worked with three F-14A pilots, one F-14B and D pilot, and three F-14 RIOs, in order to cover all of our bases.
Last year, we even flew over to the United States, to give a US Navy commander a hands on session with our F-14. The latest round of changes have been heavily based on feedback from our SMEs, and we have to tread the careful ground between maintaining performance figures reflecting the published documentation, as well as recreating the characteristics as described by our expert contacts.

Another big item on our list that has been worked on in March has been appropriate aerodynamic damage effects on the flight model.
Generally this is fairly straightforward - flight surfaces can be damaged or fall off, and the ensuing effects need to be appropriately modeled.
While straightforward, it is still time consuming, and this will continue to be worked on as we head into April.

In general, however, we consider the flight model to be practically release ready. This represents a massive milestone for the project and is the “beginning of the end” of 3 years of intensive flight modeling work. Strip away all of the avionics, radar, weapons systems, and graphics - and you’ll still be left with what can easily be called the crowning achievement of our F-14: the flight model.

The footage below is very raw and rough. It was originally intended to be a part of Episode II of the flight model highlight - but we’ve decided to just put it out as is instead due to a lack of time.
The aircraft is an F-14B equipped with our new F110 engine simulation. Enjoy a very dirty (Ew, Chromecat) look at how powerful the Tomcat really is, and some quick footage of low speed high altitude handling and subsequent acceleration:



Concurrently with everything else, work continues on the heart of the F-14’s combat capability; the AWG-9, TID and associated systems and subsystems.
There really is practically too much to list here, with work progressing on both AA and A2G functionality (though, the former, is practically complete from an early access standpoint).
Everything from targeting systems, HUD/TID/ECMD modes and readouts, datalink, radar, RWR, ECM, weapon combinations, LANTIRN, pylons/adapters has been worked on in March.

We’re again, confident in the F-14 launching in a very complete state. As ‘boring’ of a conclusion that is in an update like this - the depth of our simulation come release shall be excellent.

Much of the current work is also tied in with the aforementioned updates to our navigational systems and logic.
In the context of weapons systems, this is mainly relevant to datalink and target waypoints.
All in all - the F-14 as a development process is beginning to wrap up.
We’re late, but making the tough decisions last year to not only rebuild all of the artwork, but also to invest more into adding authenticity and breadth to the avionics and systems is paying off in spades. The extra time has allowed us to source new and exciting documentation that has filled any and all remaining gaps for us.

To give you an unfiltered insider’s look into just how much work goes on behind the scenes, here’s a look at just the F-14 code repository alone over the course of 10 days:



Major items remaining prior to release currently are as follows:
  • Completing the new cockpit and exterior, and the merge of the release branch of the Tomcat (and deprecating the placeholder Chromecat - we won’t miss it!)
  • Finalization of the new engine model, navigation systems and some other (relatively) minor parts; such as the ALR-67.
  • Final tuning of flight model.
  • Bugfixing!
  • Brushing the dust away and preparing for the rise of the Phoenix by stocking up on champagne.

We presently believe that the next 90 days will see most, if not all, of these major and minor items to be resolved, leaving us within touching distance of launching.
We’re keeping our fingers crossed and our coffee pots plentiful.


As always, thanks for your support and patience. Apologies for this update dropping so late in March and still being based on the Chromecat branch; but we’ve had to prioritize hitting development milestones over sticking to our planned PR roadmap. We had hoped to update you before the very end of the month. I’ll leave you with one more video; this time of a simple valley run and CCIP (Or, Computer/Pilot as it is known in the F-14). Featuring your first few glimpses at Jester AI!



Enjoy the F-18 livestream tomorrow!

Sincerely,
HB, F-14 Team




Bye
Phant
__________________
phant is offline   Reply With Quote
Old 04-10-2018, 12:59 AM   #235
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default

Quote:
Originally Posted by Cobra847 View Post
Dear All,

As mentioned previously; one of our main goals is to release the F-14 as complete as possible. One big item that we’re beginning to fully square away is the navigational systems, and in particular a new simulation of the inertial navigation system. The navigational systems tie in heavily with elements such as the TID and CAP, and we’ll go into more detail on these aspects in the future.

Enjoy a technical, physics based update on the navigational systems below, written by F-14 developer Krzysztof Sobczak (Ph.D Physics)!

Introduction
A good combat jet should provide the crew with means to navigate without external navigational aids or guidance. The way to achieve it is to equip the aircraft with an inertial navigation system (INS). An INS system measures and integrates sensed inertia forces (acceleration) and rotational velocities to calculate aircraft position and linear velocity. A good navigation system can precisely guide an aircraft on a route to a mission objective hundred or thousand miles-long, and then back to the home base, safely and reliably. Such a system is even more important when an aircraft is designed to operate over the ocean, far away from any ground-based TACAN or visual references.

The INS used on the F-14 is a multi-unit Carrier Aircraft Inertial Navigation System (CAINS) designated as AN/ASN-92. As you have already discovered, this system is the centre of this development update.
AN/ASN-92 features
The AN/ASN-92 INS is the primary navigation system on the F-14 and provides the crew and the other aircraft systems with:
  • Current latitude and longitude;
  • Attitude;
  • Heading true and magnetic;
  • Own ground speed and ground track;
  • Ability to store and display three waypoints, a fixed point (FP), an initial point (IP), a surface target (ST), a home base (HB), a defended point and a hostile area;
  • Range, bearing, command course, command heading and time-to-go to a selected destination point;
  • Calculated wind speed and direction;
  • Calculated magnetic variation;
  • Continuous monitoring of the status of the unit, and in case of failure inform the crew with advisory lights and appropriate acronyms displayed on the TID;
  • Backup navigation modes in case of partial system failure.

Although from the crew member’s point of view, the INS is used mostly for navigation, it is also essential for proper operations of other aircraft equipment. For example, the attitude is necessary for the radar. The attitude and the own position are required for some weapon delivery modes, particularly for long shots. Even more distressing to the crew, a complete failure of the INS renders weapons such as the AIM-7 inoperable.

The same information is used for data-link operations - when using erroneous INS data, own tracks and targets received from cooperating aircraft will not match and result in false contacts being displayed on the TID. These are only a few examples, and the INS data is used whenever aircraft position or attitude is required.
Construction and principles of operation

AN/ASN-92 is built from multiple components, but there are two particular components which constitute the core of the system: the inertial measurement unit (IMU) and the navigation computer.

The IMU is a three-axis, four-gimbal, all-attitude unit containing two gyros and three accelerometers. The gyros and the accelerometers are mounted to a platform that is free to rotate respect to the base (aircraft). The four-gimbal system provides gimbal-lock free rotation and uses torquer motors to correct platform attitude errors. The gyros sense angular rotation about their sensitive axes and are the source of information about the aircraft attitude. They also stabilise the whole platform and keep the constant orientation of the accelerometers respect to the ground. Two accelerometers are used to measure acceleration in the horizontal plane; the third accelerometer measures vertical acceleration. The sensitive axes of the accelerometers are orthogonal. The sensed acceleration signal is integrated in the computer and used to calculate aircraft velocity and displacement from the initial position. The attitude of the platform is also corrected continuously to account for the effects associated with the Earth’s rotation and device inaccuracies.

This design is widespread for gimballed inertial navigation systems. It was used for the F-14, but also for the Space Shuttle and many other aircraft of the era. Below, you can find a sketch of an IMU from the JA37 flight manual – this model is almost the same as the model used for the F-14.




An INS device like the AN/ASN-92 requires a high precision of measurements of the acceleration and the attitude, because even the smallest inaccuracy can result in a significant error when accumulated over extended time.

Consider an example: the inertial platform is slightly tilted from the nominal position, let’s say by 0.002 degrees. Then, the horizontal accelerometers are no longer parallel to the ground, and this means that they start to be sensitive to gravity. If not corrected, this gravitational component is interpreted by the navigation computer as a horizontal acceleration. If the wrong attitude is kept constant for one hour, it will result in an error of the measured position of over one nautical mile. It is a significant inaccuracy, and it comes as a result of such a minimal alignment error.

The accuracy of the INS degrades with time – usually the longer they operate in the navigation mode, the higher the error they accumulate.
INS alignment procedure
An INS device must be prepared before it is ready for navigation. This process is called alignment. Before the alignment begins, the RIO has to input aircraft coordinates and altitude.

Upon selection of the alignment mode, alignment routines are read into the computer and the first stage – the coarse alignment – is initiated. The platform is levelled using the accelerometer output, and the initial rough estimation of the aircraft heading is performed.

The second stage – fine alignment – uses the precise measurement of gyroscope drift to calculate aircraft’s true heading. This is possible because of the Earth’s rotation and utilises the mentioned before Shuler tuning. At no point of alignment, is the magnetic heading used, and the whole process relies only on the sensing of the non-inertial movement of the platform within the 3d space.

For shore-based operations, the whole alignment process should be finished within 8 minutes. It is possible to pre-align the aircraft on the ground, which allows for a quick-reaction response. This reduces the alignment time to 2 minutes but requires aircraft to be tied down in the alert position.

Carrier-based alignment is slightly more complicated than ground alignment because the ship is constantly moving. Thus, to support the process, ship’s INS data is transfer to the aircraft using data-link or deck-edge cable. The carrier-based alignment process should complete in 10-12 minutes. In case of the ship’s data being unavailable, ship’s true heading and speed have to be manually entered by the RIO.
Performance
A fully aligned AN/ASN-92 INS, in accordance with the requirements of the navy specification, for the latitude of 45 degrees North, should provide the following performance:

  • 3 arc minutes for heading,
  • 2.5 arc minutes for pitch and roll,
  • Position error rate of 0.75nm per hour (CEP),
  • Velocity error of 3 feet per second.

All values stand for standard deviation and assume a normal distribution of the error.
The RIO can decide to finish the alignment and switch to the INS navigation mode at any point after coarse alignment criteria have been met. However, a premature selection of the navigation mode will significantly degrade the navigation quality.


In-flight alignment of the F-14 INS is impossible. In case of an in-flight INS failure or a takeoff without proper INS alignment, two additional backup navigation modes are available. They provide dead-reckoning navigation using attitude information from the IMU or the AHRS (Attitude and Heading Reference Set), airspeed from the CADC (Central Air Data Computer), stored wind data and magnetic variation.


The RIO can improve (restore) the precision of the INS in-flight by updating the aircraft position:
  • With the radar by locking on the known reference point (waypoint);
  • Using TACAN signal and known coordinates of the TACAN station stored as a waypoint;
  • By overflying a visual reference point;
  • Using data-link, either when flying in close formation, or by hooking a radar track of the cooperating aircraft.
Updating the aircraft’s INS position in flight may introduce a greater error than before the update, and the accuracy is limited by the precision of the method used to update. Thus, updating has a greater usefulness when utilized as a backup navigation method when navigation stability is significantly reduced.
Simulation
Designing an INS (IMU) is an engineering challenge, which requires consideration of such problems as calibration, alignment, Earth’s rotational motion, inertia forces, thermal stability, analogue-digital converters precision, all different types of correction which have to be applied to keep the device precise over extended time, and many more. Simulating an INS platform is very similar - it is a complex undertaking.

At Heatblur, we decided to develop an entirely new mathematical model to simulate the AN/ASN-92 for our F-14. We included all the potential sources of errors contributing to the final precision of the device, and recreated the characteristic behaviour of a gimballed INS platform. The result is a set of algorithms providing an authentic representation of the AN/ASN-92 in DCS, yet optimised to have almost no impact on CPU performance.

Because a picture is worth a thousand words, below, you can find a plot which is the result of a test run of our simulation of the AN/ASN-92.

In this example, the aircraft was parked, and the initial misalignment of the IMU was equal to 0.0005 degrees - i.e. it was relatively low. The figure represents the magnitude of the INS calculated position error as a function of time. As you can observe, the rate of change is not constant, and there are periods when the magnitude of the error decreases. This oscillatory behaviour is a known effect, described by German engineer Maximilian Schuler in 1923 ( https://en.wikipedia.org/wiki/Schuler_tuning). The theoretically predicted period of this oscillation is equal to 84 minutes. In our model, those oscillations come as a natural product of the simulated physical processes. Finally, as you can see, the aircraft does not have to move for the IMU to accumulate errors.



From the functional point of view, our simulation of the AN/ASN-92 is an authentic virtual representation of the real unit and contains all features described above. Most of them are already implemented, and the final missing bits should be finished within the next weeks.
You can expect that your INS will:
  • Let you navigate to any destination point;
  • Drift and will not be 100% accurate;
  • Communicate with other aircraft systems and simulated INS inaccuracies will affect their performance;
  • Require proper alignment;
  • Use stored heading alignment method reducing the alignment time to less than 2 minutes if the appropriate checkbox is selected in the mission editor;
  • Sometimes fail and force you to use the backup modes.
Test flight results
To conclude this update, we would like to present to you a record of two test flights which we performed using our F-14 in DCS. We took off from Nellis AFB, climbed to 12000 ft, flew to Creech, then hit the dirt and turned to Groom Lake. After a zoom climb over Groom Lake, we descended back to ground level and flew straight to Lake Meade, crossed it to the Hoover Dam, passed Boulder City, and then back to Nellis. The whole route was almost 40 minutes long.

Before the first flight, we let the INS run the alignment until the “fine align” status was reached – it took a bit less than 8 minutes. The second flight was preceded by a partial alignment, stopped after 4 minutes.










For both flights, we recorded the true aircraft position and the INS calculated position.
We loaded the exported data to Google Earth and prepared graphics comparing the true flight path and the INS-sensed flight path.

The error of the calculated INS position at the end of the flight was equal to 0.4 nm for the fully aligned case, and over 4 nm for the 4 minutes long alignment.
If you want to take a closer look at the results, you can download the recorded flight paths and open them in Google Earth:
Fine alignment: https://drive.google.com/open?id=1yI...qvBaA6hnUHwDQx
4 minutes alignment: https://drive.google.com/open?id=1Bx...M3ZHA6QqRaxZKE
Many thanks for reading!
We will return to the AN/ASN-92 in one of the next development updates when we take a closer look at the practical side of using the navigation systems of the F-14.

As always, thank you for the support!

Sincerely,
Heatblur Simulations








Bye
Phant
__________________
phant is offline   Reply With Quote
Old 04-11-2018, 07:21 AM   #236
komemiute
Member
 
komemiute's Avatar
 
Join Date: Feb 2012
Posts: 821
Default

Bombcat confermato!
komemiute is offline   Reply With Quote
Old 04-23-2018, 12:09 AM   #237
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default


FONTE https://www.facebook.com/heatblur/posts/877804192407200


Bye
Phant
__________________
phant is offline   Reply With Quote
Old 05-07-2018, 01:13 AM   #238
phant
Senior Member
 
phant's Avatar
 
Join Date: Apr 2005
Location: Italy
Posts: 2,952
Default

Quote:
Originally Posted by Cobra847 View Post



Dear All,

Since our last development update, the team has been working hard towards the completion of the final items that we listed in our March update. We're making strong progress on all of these, and we're doing our utmost to try and complete as many high quality features for the F-14 as we possibly can. Later today, the team will be meeting to plan the last major push in features and development tasks required for Early Access release. There may be some quiet in the next month or two as we hunker down and crunch hard - but we won't rest until we are satisfied, so take it as busy silence in preparation for the coming rise of the phoenix.

All in all, we're incredibly excited to begin to reach the end of the beginning. Now that the aircraft becomes more and more feature complete, it's time for us to start going in depth on content. We're always been committed to ensuring that we launch of products with as much free, high quality content as we can. This includes e.g. campaigns and AI aircraft, ships and other assets. The F-14 will be no different - it will ship with two campaigns; one for the F-14A and one for the F-14B (A+). Work has begun on these, but they will not be part of the Early Access release. Early Access will however have Single Missions, Multiplayer Missions, Training Missions and Instant Action available from day one.

The objective of creating the F-14 campaigns was to create two separate opportunities for realistic gameplay that broadly exposed the player to the aircraft’s strengths and weaknesses, while taking inspiration from real scenarios.

DCS currently offers two combat theaters that are suited to the suited to the F-14: the Black Sea map and the Persian Gulf map.

We felt it was important to offer an included campaign that could be played by any DCS user who purchased the DCS: F-14A/B.

For these reasons, we chose the place the F-14B (as the F-14A+ operating in late-1990) in the Black Sea Map for its campaign. The F-14A will have a historically-based campaign that takes place in the Persian Gulf Map – taking direct inspiration from real deployments and combat events in the theater from 1987-88. This closely matches the timeframe of the module itself and the aircraft as equipped.

Below are overviews of the campaign storylines with the background leading up to the start operations. Effort will be made to include historically accurate airwing compositions and squadrons as part of the campaign.

Besides Campaigns, we're working hard on both announced (Forrestal Class) an unannounced extra content (aircraft & other units) for the F-14. On full release, we believe it will be one of the most comprehensive packages available for standard DCS pricing.

Enjoy the read!

Click the images to read!







Bye
Phant
__________________
phant is offline   Reply With Quote
Old 06-21-2018, 03:29 PM   #239
Mig Fulcrum
Member
 
Mig Fulcrum's Avatar
 
Join Date: Jul 2016
Location: Verona, Italy
Posts: 313
Default

Consiglio a chi ha un'oretta di tempo di ascoltare questa intervista allo staff HB, parla principalmente dell'F-14 ma anche del Viggen, Mig-21, progetti passati e futuri.
Mig Fulcrum is offline   Reply With Quote
Old 06-22-2018, 02:26 PM   #240
Lordfacker84
Member
 
Lordfacker84's Avatar
 
Join Date: Jul 2010
Posts: 315
Default

Ma scusate la domanda ma il mig 21 è uscito dall'early access? perchè sul sito della dcs c'è ancora scritto
Lordfacker84 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 11:55 AM. vBulletin Skin by ForumMonkeys. Powered by vBulletin®.
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.