I would absolutely have a battery backed up GPS.
Unfortunately (short of a 2nd panel mount GPS, backup battery powered via a nontrivial paperwork exercise
) the only way is a handheld unit mounted "temporarily"
in the yoke or similar.
I have a Garmin 496 thus mounted, with its audio output wired to the aircraft intercom. I got the yoke wiring signed off but obviously the 496 has to be "officially removable".
It works brilliantly as a substitute for the £25,000 Honeywell GPWS system and - apart from maybe cases of loss of obstacle clearance
while flying an approach (I think the G496 basically disables its 2-minute trajectory extrapolation when flying anywhere near a known approach) - I am sure it is every bit as good, and it provides a "five hundred" warning at 500ft AGL anywhere at all; great for doing the gear-down check. After flying with this for 4 years now, and having seen the warnings during certain visual approaches, I am at least 99% sure of never flying into terrain enroute. A fantastic feature for £1000... especially when you consider how many people get killed in CFITs.
It took a while to work out the audio connections, because Garmin's docs are useless and they rather arrogantly would not offer any additional info. I have the details if anybody wants to do this.
There is a simple upgrade from a KLN90B to a KLN94, I believe, which is not a bad option.
And a Garmin 430's screen is only marginally bigger than the 90/94 screen, by the time a chunk is lost to the radio frequencies etc. If I was spending any serious money, for IFR, I would never have a 430-sized unit as my sole moving map. The main feature of the 430 is that it is common as muck, replaces an old clapped out radio (a common enough requirement
), gives you an FM Immune radio (likewise), and incidentally also gives you 8.33k spacing. Today I would install a 530W, or perhaps a 430W with a big MFD which is capable of displaying stuff like Jepp approach plates, or just a decent map.
The other thing is that if you fly any significant VFR, you need a GPS which can display VRPs. These tend to be mainly portable units, though the now-obsolete KMD150/KMD550 products have European VRPs in them which was brilliant for my pre-IR long trips abroad. I would think the modern MFD products (GMX20 kind of stuff?) will display VRPs but it needs to be checked.
Often, outside the UK, one cannot file an
I flight plan to a destination which does not have an IAP and then (filing
Y to achieve Eurocontrol acceptance) you are flying 100% "officially VFR" at the end and are thus vulnerable to ATC throwing a few VRPs at you. A lot of foreign international-airfield ATC can barely speak English and a pilot not finding a VRP gets them really excited
Personally I fly with a KLN94 and a KMD550 MFD which is damn hard to beat for a mixture of VFR and IFR. I never bothered to install GPSS (even though it is just 4 extra wires in my case; about a day's labour) because even on a long trip, say 800nm, one has to adjust the course pointer maybe 20 times which is no great hardship
The only thing I can't do is fly one of the complicated PRNAV STARs/transitions (e.g. see LOWW) if ATC tell you the name of it with not enough time to load the individual waypoints by name from the database... and of course I can never have
PRNAV which would be a ~£20,000 refit exercise.
Anybody doing a serious IFR refit today must go for
PRNAV compliance
and get all the flight manual supplement paperwork. Most UK avionics shops are not capable of delivering this 100%, and some of those who are don't always deliver it, judging from pilots I know personally who got ever so slightly short-changed despite having paid 5 digits.