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Why do I need a THIRD radio if I want GNS430w + GNS530w (dual GNS certification issue)

Dual ADCs which must share a common failure mode
Should not be if they have their own pitot and static sources, alternators and buses.

They are different busses, they don’t use different alternators or different pitot head or different static ports on most general aviation aircraft. So there a still some common (single point) failure mode. Like we discussed a while ago, where a pilot didn’t notice that the pitot got iced up, and both ADC AND mechinal backup will give incorrect readings.

The weak point in a G1000 is the LCD and the associated circuitry – the drivers, and the backlight inverter which is probably the most common failure even on high-end laptops (top end Thinkpads) whose build quality is similar to the G1000.

Altought that might be a weak point as on most displays this and might be common, it would not be a common (single point) failure mode. As the G1000 uses two displays the second display could be used. It would be highly unlikely both failed. Where a single point failure mode such as iced up pitot, or single avionics switch / buss methode can introduce a complete system failure with only one faulty item.

The weak LCD is a hardware problem, which is not related to G1000 only.

EASA’s argument on dual GNS is a very weak argument as there are other single point failure modes in hardware they refuse.

What would be a valid argument is both systems running the same software, with a bug causing both system to hang. This however is part of the software certification, and quite hard on essential systems.

JP-Avionics
EHMZ

I think the logic went like that: "it is bad enough that they get these newfangled gps thingies with moving maps in the panel and i have to allow them because some idiot certified the device, they definitely don’t get TWO! If i give them that, what will they think of next – removing the ADF or not having a stopwatch???? Now back to writing this AIC on How GPS is not to be used for navigation, beats me why the called it NAVSTAR, this is misleading….

Biggin Hill

I think the real Q to ask is how did the TC holders get the approval.

That would need a contact at one of them – Cirrus Diamond or Socata I guess.

My normal contact at Socata managed to accidentally send me a derogatory email tail (in French) which shows their support attitude (well, anything beyond sales of parts, which is never a problem) on the piston aircraft line, which I got translated by several native French speakers just to make really sure that the google translation was really as bad as it looked, so I guess their support for the aircraft is limited nowadays But to be fair anybody involved back in the late 1990s would have left the company by now.

It probably won’t be any good asking EASA since all these were approved by national CAAs, pre-JAR probably, and grandfathered.

One might think that Socata would have had a cosy relationship with the DGAC – as per the standard French “industry / government relationship” – but the evidence points the opposite way. The DGAC demanded the fuel totaliser transducer to be mounted in a position where it reads about 25% out and Socata duly installed maybe 100 of these, with a Gallic shrug to anybody who wondered why it didn’t work too well even with a bodged K-factor. They they demanded the WX500 stormscope to have the heading input disconnected because otherwise it would enable the pilot to use it to avoid thunderstorms.

Last Edited by Peter at 29 Aug 15:20
Administrator
Shoreham EGKA, United Kingdom

They they demanded the WX500 stormscope to have the heading input disconnected because otherwise it would enable the pilot to use it to avoid thunderstorms.

Too funny.

The world of regulation is a world unto itself….

I am currently engaged to opine on a matter in my profession: two different regulators have been in consultation to decide how a relatively lightly regulated area of finance ought to be dealt with in the future in order to protect some large businesses from some really small potential losses. The regulators now invite opinions after having, perhaps not surprisingly, decided that a whole raft of new expensive regulations will do the trick! Give a man a hammer, and after a while everything starts to look like a nail!

Come the revolution…

Howard

Last Edited by Howard at 29 Aug 19:17
Flying a TB20 out of EGTR
Elstree (EGTR), United Kingdom

I think the real Q to ask is how did the TC holders get the approval.

It was not an problem to get a minor change on a dual installation in the past either.
Somebody just changed his/her mind or something like that.

JP-Avionics
EHMZ

By the ridiculous logic of common mode failure, two VOR Nav systems sharing the common antenna and using a common power source should mandate their removal. To make matters worse, if the GS receiver uses the common antenna thru the common cable to the common splitter, woe are you. With a single pilot using a single brain, those two eyes would not be approved in EASA. I am so happy that I only have to put up with the FAA BS.

KUZA, United States

The TB20 has a single engine, a single vacuum pump, a single alternator and a single drive dual magneto. The pilot at least is married :D

Don’t tell EASA.

Howard

Flying a TB20 out of EGTR
Elstree (EGTR), United Kingdom

The pilot at least is married

That bit I don’t understand. The MTBF of a marriage is about 7 years Mine dragged on for … let me count them … 8 years!

I think the average alternator will outlast the average marriage. The engine definitely will.

Last Edited by Peter at 30 Aug 19:47
Administrator
Shoreham EGKA, United Kingdom

:-)

Flying a TB20 out of EGTR
Elstree (EGTR), United Kingdom

[thread drift]
AIDS: Aviation-Induced Divorce Syndrome.

I have been married about the same time I have been flying and have exactly enough fingers and toes to count the years.

The first time my wife came to the flying club, she was presented with the most important document of all: a public information leaflet about divorce.
[/thread drift]

LFPT, LFPN
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