D100 300xl and no hs34

[mobrien02]

Hello,

My RV7-A is completed and flying.  My panel wiring was completed using the excellent services of Approach FastStack using their Pro Hub.  When configuring my panel, my research (at that time) revealed that an HS34 was not required, so my panel does not include an HS34.

The following instrumentation is the subject of my post to the forum:
GNC 300XL
D100
MD41-1444
TruTrak A/P

(Note: I have other instrumentation: A 2nd D100 that is fed by an SL30.  The two Dynon's are not connected via DSAB)

My questions concern the situation when executing a GPS approach and a course reversal is required where a fix is crossed twice.  Once for the outbound course reversal, and then again on the inbound.

According to my GNC 300XL User manual, the instructions for this type of approach indicate:

1. Select the approach and confirm the GPS APR switch indicates an 'ARM' approach status
2. Fly towards the IAF (in this case for the course reversal)
3. Two nautical miles before crossing the fix, set the GPS SEQ switch to the HOLD position
4. After crossing the IAF, set the outbound course on the HSI
5. Initiate the procedure turn and set the inbound course on the HSI, then set the GPS SEQ switch to AUTO.  
6. Confirm the GPS APR switch indicates an 'ACTV' approach status within 2 nm of the FAF.  Complete the approach.

My D100 does not offer me any options (that I can find) to set the course on the HSI (as the 300XL user manual dictates in steps 4 & 5 above).

I am beginning to suspect that this will not be possible with this configuration (and my initial research missed this subtle point).  

Question 1) Can somebody confirm (or not) my suspicions please?

Question 2) In the event I won't be able to manually set course information on the HSI, what options do I have for course input during the procedure turn?

In all other scenarios, the GNC 300XL, MD41-1444, the SL30 and the pair of Dynon's perform flawlessly.

Your feedback is greatly appreciated.

 

[dynonsupport]

Without an HS34, there is no way to set the OBS on an external device. The 300Xl will only accept OBS via ARINC-429, which is what the HS34 gives you.

 

[mobrien02]

Ok, thanks for the confirmation.  I was afraid of that.  Hopefully others will learn from my mistake.  Onward...

In my configuration, the 300xl drives the 1st D100, and the SL30 drives the 2nd D100.

My research on the HS34 reveals multiple inputs so that a single HS34 can be used with two Dynon's -- which is my case.

A couple more questions  

1) If I add an HS34, and connect as required via DSAB, will I be able to use the NAV/GPS source button on the HS34 to control which HSI (Dynon #1 or Dynon #2) the HS34 is controlling?
2) Does this also imply a change in wiring to the MD41-1444?  (Today, it's only wired to the 300xl, and I'm not sure what value I get connecting the MD41 to the SL30...)

Your help is much appreciated, thanks!
Michael

 

[dynonsupport]

In a DSAB connected system, you can't show different data on one HSI vs the other. So if you buy an HS34 and hook all three units together, you get 1 HSI in the system. You can use the NAV SRC button to choose between the SL-30 and the 300XL, but not both at once. We do have bearing pointers, so you can display the Bearing (direct to line) from the second source if you wish.

If you hook the HS34 and one EFIS together and leave the other one off the bus, you can have them totally independent.

Don't know anything about the MD41-1444. It's an annunciator panel right? I believe you only hook those to certified GPS units.

 

[PhantomPholly]

Some additional thoughts.

My information may be out of date, but I believe they used to say you can hook up a single serial connection (as you have today) to an EFIS unit and, in the event that the HS34 fails, that may still give you basic course information from the GPS. Thus you would retain some of the "redundancy" safety even if the HS34 failed. This can be simulated in flight by pulling the CB for the HS34 only, and determining if you can then use the EFIS to select the serial feed from the GPS.

Secondly, I really can't think of a scenario that requires both devices (GPS & VOR/ILS) to be displaying course information at the same time - usually it's enough to have one course plus the second bearing needle. GPS guidance to a localizer invariably puts you close enough that when you switch the HSI to ILS you have needles between the outer dots - and with your TruTrak AP (you didn't mention which model) you can easily hold true course while waiting for the needles to come off the wall.

If your TT is a DigiFlight II and you are paranoid, you can hook up both the ARINC and Serial lines from the 300XL. That way you can at least get course guidance if the ARINC wires break in flight. Same holds true for the HS34 - you can connect both ARINC and Serial from the 300XL (set one up as "GPS 1" and the other as "GPS 2") - just don't forget which is which...