Having recently experienced quite long GPS outages due to jamming and having VOR as the only navigational reference, I wouldn’t fly IFR without VOR (actually without 2 VORs and DME). Than you see how having three moving maps with three separate GPS receivers is completely useless when they rely on a single point of failure.
The market for this is someone who currently has a GNC300XL or one of these with a separate Com or NavCom unit: GPS155XL or KLN90B or KLN89B or KLN94. It also makes sense for those who already have dual Nav/Com and wish to add a WAAS GPS/Com capability
arj1 wrote:
Still trying to understand what is the main difference between this device and GTN 635 (GPS+Comm).
The GNC 355 is only for Part 23 Class I/II aircraft (<2730 kg). The GTN 635 is not so limited. I think this permits a lower level of software design assurance (level C) in the GNC 355, which may reduce the cost.
It fits in a smaller space!
bookworm wrote:
The GNC 355 is only for Part 23 Class I/II aircraft (<2730 kg). The GTN 635 is not so limited. I think this permits a lower level of software design assurance (level C) in the GNC 355, which may reduce the cost.
I don’t see why they wouldn’t simply reuse the software from the GTN635 and just disable the features the GNC355 can’t (or is not supposed to) have. That’s what I would do….
Airborne_Again wrote:
I don’t see why they wouldn’t simply reuse the software from the GTN635 and just disable the features the GNC355 can’t (or is not supposed to) have. That’s what I would do….
If the hardware is sufficiently compatible, yes, exactly. And then one certifies the version-with-disabled-features to the lower software design assurance, to “justify” the lower cost :)
lionel wrote:
And then one certifies the version-with-disabled-features to the lower software design assurance, to “justify” the lower cost :)
Why do you have to recertify the software? Anyway, the lower cost justified by lack of features and screen size, is it not?
You can legitimately claim the cheaper product’s software meets a less stringent requirement, even if it is identical to the other one.
It’s all a part of a strategy called product differentiation and everybody does it 
Peter wrote:
It’s all a part of a strategy called product differentiation and everybody does it
Sure. My favourite story comes from a guy in my club who was manager of cabin systems at Scandinavian Airlines (this was in the 1980s). As old enough people will remember, in-flight entertainment in Economy Class at that time did not use proper headphones. Instead there were speakers in the armrests which were connected to headphone-like things by plastic tubes. Of course Business Class had proper electric headphones.
Now, this guy told me that it was actually more expensive to do it this way than it would be if economy class also had proper headphones. But it was important for product differentiation between the two ticket classes.
So the airline actually took additional costs to make service in Economy Class worse!
Airborne_Again.
Business is not about making sense, it is about making Money.
