[RBurn]

My questions is why do people put multiple EFIS brands into their aircraft?

I'll start off by saying that I've never flown in an RV, or behind any of the EFIS systems currently on the market. However, I do know from reading these forums that these systems are feature filled and software intensive.

In my opinion people should stick to one EFIS system in their aircraft and learn to deal with the enhancing qualities and deficiencies of that system.

Here is my reasoning for this...

Aircraft are already complex, requiring the pilot to know how all the systems operate. In an emergency that knowledge should be second nature, and the pilot should be able to react without thinking. Having multiple EFIS brands/GPS units, etc. leads to the pilot having to think about where items are located in the menus. On top of that, the pilot also has to remember the failure modes of the different pieces of equipment. This can become overwhelming especially in an emergency.

Let's use computers as an example. I'm currently using a Vista machine at home. My laptop at work has XP. Some of the other computers at work have Windows 2000. Jumping from one system to another usually isn't a problem, but when I need to get to something quickly, I have to think about where it's located. Windows is an easy example because they are pretty similar to each other. However lets say you use Windows at home, and you use a Mac or UNIX at work. Then it's very different. Similar to what I think using different EFIS systems would be. Also try making a network work with different operating systems, it's not always easy. Same with getting avionics to talk with one another.

The reason I think people put multiple systems is in case one fails the other one hopefully will not. But as pointed out in another thread, if your pitot tube gets jammed then neither system will work (unless you have an independent pitot and static for each system).

In summary, I think people should stick to one EFIS system for safety. Now they become familiar with one system and know it well.

I don't want this to become a sounding board for how reliable different brands are (notice that I haven't specified any). Nor, should this be why brand X has better redundancy than brand Y. I just want to hear everyones logic on why or why not to use multiple systems.

Thanks,
Ron

RV wannabe

 

[Bugsy]

Your question is relevant. In military systems we mandate in the requirements that our standby systems be on a seperate bus and from a different series design. However from a human factors standpoint your thought is relevant. I have investigated several spatial D mishaps were pilots were unwilling to utilize the standby ADI/EFIS. Our lessons learned throughout wasnt that the original requirement was invalid but that we need more practice and comfort with standby instruments. Our new simulator syllibii are including not only emergency procedures that emphasize recovery but also more insidious situations that emphasize recognition.

I believe the desire/requirement for different design series or manufactures is valid, but without practice and comfort in transition negates the benefit. Now of course none of this matters if all you want is something cheaper to sit on the passenger side, and nothing wrong with that either.

 

[flyeyes]

My questions is why do people put multiple EFIS brands into their aircraft?

(snip0if your pitot tube gets jammed then neither system will work (unless you have an independent pitot and static for each system).
(snip)
In summary, I think people should stick to one EFIS system for safety. Now they become familiar with one system and know it well.


Thanks,
Ron

RV wannabe

The really important stuff on the EFIS boxes (i.e. attitude, heading, altitude) tends to be a simple, intuitive interface and doesn't vary much between designers/manufacturers. The navigation interfaces can have a steep learning curve, but I don't learning two boxes is really very difficult.

I routinely fly three different aircraft, two of which are EFIS-equipped. All the equipment is different in each plane, but it really isn't too much of a problem.

The reason to mix vendors is that it reduces the chance of a single unforeseen point of failure, especially in software. These problems can show up even in expensive, carefully vetted systems. A great example is here.

A lot of certified autopilots use the aircraft's primary attitude gyro as a reference. If the gyro fails, the pilot loses his primary attitude reference and his autopilot at the same time. I like the idea of a stand-alone independent autopilot.

Your point about pitot-static is well taken, and many larger airplanes have independent systems. Both of the IFR-equipped aircraft I fly have backup static sources, and my RV-8 has an independent pitot as well.