Increasing EFIS Back-Up Period

[Basil]

Under Australian Regulation CAO 20.18:

An aircraft  that is approved to operate at night and is equipped with an EFIS must be provided with a battery[ch8209]powered back-up in the case of a failure of the aircraft electrical system, for the purpose of enabling the pilot to divert to and use a safe landing site.

If an aircraft equipped as required above has a battery-powered back[ch8209]up to an EFIS, the back-up must be of sufficient capacity to power the EFIS panel or other display for 90 minutes and must be fully charged before the commencement of a flight at night.

How can the 90-minute requirement be achieved on a single Skyview panel where you can only plug one (1) SV-BAT-320 and my understanding is that it only lasts just over 60-minutes ?  Can you couple two 320's ?

 

[jakej]

2 X Alternators is a better solution IMO [ch128077]

 

[jakej]

Pm me if you want to discuss this more.

 

[Basil]

Yes would like to discuss. You can text me your mobile # (if you are fine with that) or call me on mine 0412925300.

 

[jakej]

Will do

 

[KRviator]

If the alternator fails, wouldn't the ships battery power the backup for the 30minutes you need to bridge the gap between the Dynon battery, and CAO20.18's requirements? I know in my RV, with a single 10" screen, I am only drawing 4 amps in the cruise.

 

[dynonsupport]

If your SkyView system has 2 displays and each is equipped with a back-up battery, you have 120 minutes of on-battery time by using the displays in sequence.  When electrical system fails, both SkyView displays would enunciate they are on back-up battery.  You would power down one display to preserve its battery capacity for use if/when you deplete the battery on the primary display.

 

[Basil]

I agree if you have two screens you can comply with the 90-min rule, but if you only have one screen fitted (which is not unusual) then you have a problem. Just by coincidence we have a Sportstar with one screen and there is another LSA also with one screen; and we are facing the same issue.

 

[dynonsupport]

It sounds like you need to talk to Jake who is local.

90 minutes is really long for a backup battery- in the US we generally just require 30. If you are allowed to count the aircraft main battery, you're fine. If the assumption is that the whole main bus goes to zero volts, we don't have a great solution. You cannot wire up two Dynon batteries. You'd need to come up with some external solution.

 

[mmarien]

2 X Alternators is a better solution IMO

I agree with Jake (and my mechanic) that a second alternator is a better solution than a battery. Batteries are limited sources whereas an alternator can be considered unlimited. However, a second alternator doesn't solve the problem of an electrical system failure, just an alternator failure. And doesn't satisfy the regulations.

I have electronic fuel injection. If my electrical system quits so does my engine. The solution was to wire a completely separate bus for my essential equipment. All it does is switch the electrical source directly to the battery and bypasses VP-X. That gives me some grace time (limited to battery power) should the electrical system fail.

You could do the same thing. Use a toggle switch to power the EFIS directly from the ships battery. The ships battery would probably give you 90 minutes of power with or without the SV backup battery.

Nice thing about the system is that my engine runs happily with the toggle switch in either position. I used relays to switch between the regular bus (NC) and directly to the battery (NO). The relays switch so fast the ECU doesn't reset and the engine doesn't miss a beat. Checking the essential bus is an item on my runup checklist.

 

[Basil]

Thanks Murray - one of the options I was considering, and your diagram certainly helps. Another option I am also considering is TCW Technologies "Integrated Backup Battery System"; my first impression is a well considered and cost effective solution.

 

[jakej]

Hi Murray,
"The solution was to wire a completely separate bus for my essential equipment." That's what I always do, just didn't go into ALL the details with my 2nd Alt comment

 

[dynonsupport]

The largest TCW battery is 6AH, while the Dynon battery is 4.4AH. It's unlikely the TCW will get you to 90 minutes unless it's used in conjunction with the Dynon battery.

The Dynon battery lasts over an hour when brand new and over 1/2 the power is the screen backlight. Can you justify saying you will dim the screen in a failure? Do you need 90 minutes when first designed, or do you have to check it every annual?

 

[jakej]

DS - the real issue for us here is that CASA has changed/amended some regs & I feel they unintentially included Instruments & systems requirements for IFR with VFR rules.
The battery/battery life issue has never applied to VFR aircraft here beforethe latest rule change - IMO it will be changed

 

[KRviator]

What part of 20.18 requires the 90 minutes? Im having a blomd moment and cant find it. There was a requirement for ongoing power after the loss of the generating system to be found so the ships battery would fulfil that requirement.

 

[jakej]

There is no requirement for VFR, simple as that