REP as a learning tool for sim pilots

When I first thought to a software similar to the Reality Expansion Pack, I wanted a tool that would be useful for my personal training. As a real life pilot, sometimes I cannot fly for a long period of time because of personal commitments or the bad weather (especially during the winter).
In those ground periods I need some realistic simulator to keep me in touch with the real life procedures, in order to not loose the good habits I developed in my years of fliyng.
I started to think how such a software would have been developed and then, step by step, I decided to build something that would have been useful for others too, as a learning tool for instance.

The Reality Expansion Pack can teach you what to do (and how to do it) when you fly an airplane in X-Plane. This because:

  • It provides high fidelity flight dynamics (correct engine power output, correct speeds and fuel burn)
  • It simulates a large variety of advanced systems onboard the aircraft
  • It has a “hangar” view that reports the status of your aircraft
  • If something went wrong, it warns you and tells you how to avoid the problem in the future.

The last point is the one on which I want to focus now.
If you do not manage your aircraft correctly, you may incurr in a sytem failure. If you are an expert pilot you may understand what happened and how to recover but if you’re still learning you may want something like the following screenshot.

REP Failure Message: a useful learning tool

That’s right. REP tells you what happened and how to avoid the same problem to re-occur in the future.
So, together with the software manual, you will also get a kind of a “personal” instructor that tells you what you did wrong: the learning tool I was thinking about.

PS: The hardcore simmers will be able to disable this feature in the settings menu of REP. ;-)

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REP: Airplane load balance in X-Plane

The Reality Expansion Pack project is all about taking the real things and putting them into X-Plane as much as possible. Making things more real lets you have more fun but also lets you learn something about real aviation.
For instance, the first thing you want to learn when you take your step from flight simming to real flying is safety.

Safety: The airplane load limits

When you are going to fly a real airplane, even before doing your ground checks you have to make sure that at the current load your plane can safely fly into the sky.
To do that you have to make some calculations to see if the Takeoff Weight (TOW) of your airplane is below the Maximum Takeoff Weight (MTOW) and that the center of gravity (CG) is inside its limits.
Basically, you sum the airplane’s empty weight (EW), the passengers and baggages weight (Payload) and the fuel weight to get the total weight of the plane on takeoff (Takeoff Weight). Then, knowing how far each load station (such the front seats) is from a reference point (defined by the airplane manufacturer), you calculate its moment of force.
Now all you have to do is sum all the moments of force and divide the result by the TOW. You will get a number that is the distance of the center of gravity from the reference point of the aircraft. If the TOW is below the MTOW and the CG is inside its limits (defined in the plane’s operator handbook, or POH), you are good to go.
If you want to get more information about this, I think that this video shows a lot on how to calculate the load balance of an airplane.

Load Balance in X-Plane using REP

X-Plane doesn’t come with a tool that lets you easily do the calculations described above. Also, you can manually adjust the CG at the position you prefere by going into the “Weight and Fuel” menu.
This is far from reality, where you can slightly move the CG only by moving the load inside the plane.
So here is where REP takes action providing you a new tool to calculate and apply the load balance of your airplane into X-Plane.
All you have to do is go in the REP menu and choose “Weight & Balance”. Then, the following window will popup.

Load Balance

Well balanced airplane in REP

In the window shown above you can set the passengers weight and the fuel load. REP then takes care of everything and shows you the CG envelope plot you can see in the right pane of the screenshot. In that plot, you get the airplane weight on the Y axis and the CG position on the X axis.
As long as the small green cross is inside the area delimited by the blue line (that’s the CG envelope!) you are good to go.
If your plane is too heavy or the CG is outside its limits, you will get a red cross outside the envelope, as shown below.

Load Balance

Overloaded airplane in REP

When you are fine with the payload of your airplane, just press the “Apply” button and REP will set the X-Plane payload and center of gravity accordingly to your settings. You will actually see the plane changing its pitch when the center of gravity position is set.

In these screenshots the CG position is shown in meters and the airplane weight in kg but in the REP’s settings menu you can switch to inches and lbs if you US units of measure are more familiar to you.

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REP: User Interface Preview

In my last post I’ve promised some screenshots of the user interface that REP provides to you to manage your aircraft.
With the Reality Expansion Pack you can manage your aircraft’s systems in the “Hangar” window.
The screenshots that I’ve attached are those of the working UI that we are already using. Keep in mind that there are still a lot of things that we want to improve (and more tabs that we will add, such the one related to the Oxygen System).
These screenshot are related to the Hangar window only. More pictures of the other windows will come in the next weeks.

So, here the images.

Engine user interface

In the “Engine” tab you can check the status of each cylinder and fix them id necessary. You can also check your oil and change it when necessary. At the bottom, you can check the starter status.
The engine management interface

Electrical/Avionics user interface

In this tab you can check the status of the battery and fix the avionics (which may be broken if it was already turned on when you started or shutted down the engine). Unchecking the little checkbox will disconnect the battery to avoid a self discharge when the plane is not flown for a while.
The electrical system user interface

Landing Gear user interface

Here you can check and fix your landing gear mechanics, the brakes status and the tires damages.
A bad landing may results in a damaged landing gear as much as a prolonged braking may overheat the brakes.
The landing gear user interface

I think that the next week I’ll be able to post something more.
Stay tuned!

PS: Some user complained that the XP user interface is ugly.
I agree with you that the default XP interface isn’t something you would call “beautiful”.
We decided, anyway, to use it mainly for two reasons:

  1. It is consistent: It works using the same flow of the sim interface
  2. It may be replaced easily with some custom graphics: we can easily update our code to replace the default X-Plane style with something else if it’s needed. If you look closely, you will see that we have already replaced the progress bars.
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REP: The electrical system

I’ve been out for a while. In the meantime the work on REP is gone further ahead.
We have been working on the electrical system (which is not really complex on a GA airplane).
The most complex components are the battery and the alternator.
A Cessna 152 battery (lower left corner)Both are rendered quite realistically in X-Plane so we didn’t have to do much work, I must say. Mainly, what we did is model the battery dynamics when the battery itself is switched off.
A battery is, in fact, “alive” even when you are not using it.
For instance, every battery suffers of self-discharge and so does the battery we have on board of our GA piston aircrafts.
A self discharge is a phenomena that takes action when the battery is not used. Also, it is more effective when the battery is connected to a circuit, even if the circuit is turned off.
REP keeps the battery state between sessions: if you discharge the battery and then reload the sim, you will get the same electrical charge you left in it in the previous session minus a little amount dued to the battery self discharge.
The amount of charge lost by self-discharge is relative to the amount of time the battery was left unused, so if you leave the sim for two days you will loose less charge than leaving the sim for two weeks.
If you plan to not use a REP powered plane for a long time (for example, for an entire season) you may want to disconnect the battery in order to keep it safe. You can do this via the “Hangar” menu of the plugin.
If you disconnect the battery it will still loose a little bit of charge but not too much.

That’s it for today!

PS: In the next days I’m planning to release some screenshot of REP’s UI and maybe a video showing part of the damages system. ;-)

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REP development: from devs to sim pilots

I want to explain a little bit how REP is developed and what we plan for the next months.
We are at something like the 50-60% of the REP development and we have written more than 12.000 lines of code.
It’s a lot of time that we started this project and so I think you should know why you have to wait so much for it to be ready.

The REP development

As I said in my other posts, REP is not only a plugin but a set of flight dynamics, sounds and, of course, C++ code.
In the past months we created a robust codebase that, if correctly configured, can simulate almost any mechanical part of any aircraft.
Basing on our personal experience as developers and real life pilots, our efforts were spent to provide a deeply modular code structure made of something like LEGO® bricks. We can now add, remove and modify parts of the system on the fly.
Also, a modular system allows us to easily test every component outside X-Plane, using a bunch of automated tests that ensure that everything is working as expected.
Our plan is to have a first version of the software that can be upgraded fast, adding more bricks in order to provide more features.

No aircraft is like another

There’s no way to get an accurate simulation of every airplane with just one software without a very precise configuration.
Let’s be clear: REP will work with one plane at a time. It means that we will release REP for, let’s say, the Cessna 172, then we will release (after few months) the PA28 and so on.
This means that REP will not automatically work with every airplane that you load in the sim because the sim itself does not provide enough information about the airplane you are using.
For example, if the airplane is powered with a turbocharged engine, wich kind of turbocharger it is? How does its wastegate work? Simply we don’t get this information in the sim so we need to configure the systems for each plane we want to fly with REP.
The need for a very deep system configuration requires a lot of attention to details thus it take a lot of time.


  • We’re working very hard
  • Releasing the first aircraft will take much time
  • Releasing the other aircrafts will take much less time

    See you soon!

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