New Bravo Owner Questions

[metdvm]

Got my '95 Brava 519MB a week ago. Spent 5 hours with a CFII getting familiarized with the Bravo, and learning to land again. Flew a 201 prior to that, so am learning about turbo chargers etc. I have come across a couple of threads commenting on ideal power settings, and I'm sure there are many opinions, but one that I took note of stated that 50 df ROP is a very bad power setting. Just flew from DVN to NQA and ironically was at 32" MP 2400 RPM and 50 df ROP at 16.4 gph. I thought this was great, but am I harming the engine?

Second question is about the kfc 150. I have had some problems flying approaches and having the AP pick up the GS. It flies the GPS flight plan without a problem and flies each leg of the approach. When I turn final I push the APR button and end up fighting the AP to follow the GS. 

Thoughts and advice are greatly appreciated.

 

[David Mazer]

When I got my Rocket in 06 the KFC 150 would fly left of course and porpoise around an altitude until it either mad me sick or I turned it off and reset it.  In the end, it took two avionics shops and a whole bunch of money to get it working reasonably well.  There were a couple software upgrades to the autopilot that have come out that may not have been installed in your Bravo that might help but my problem required lots of work in the end.  I hope your squawk is easier to fix then mine was.

[danb35]

There are a lot of threads that discuss engine power settings and leaning, and it seems that a lot of them get pretty emotional.  In point of fact, 50 ROP yields the highest CHTs and internal cylinder pressures, and setting your mixture richer or leaner than that will cool things down.  I haven't seen anybody try to dispute this, and Lycoming and Continental's own data agree.

Many authorities today recommend keeping CHTs below 380 at all times (some allow as high as 400, but cooler will almost always be better).  If your CHTs are hotter than that, you should do something (enrich, lean, open cowl flaps if available) to cool them off.  I trust you have a multiprobe engine monitor?

I'd recommend taking a look at John Deakin's Pelican's Perch series of articles on avweb.com; you can find them at http://www.avweb.com/news/pelican/list.html.  Pay particular attention to the 4-part "Where should I run my engine" discussion (starting with #63) and the Fire-Breathing Turbos, starting with #31, but there are several others that address engine operation.

[TLSDriver]

I have a Bravo.  Power in cruise is 32" and 2400 rpm if the extra knot or two is worth it or 30" and 2400 rpm.

Your fuel flow seems way to low.  Most Bravo guys are at 18-20 GPH.  At a miniumum I would fly it at 100 ROP (assuming ROP is where you want to be.)  

Most people would tell you that 50 ROP is about the worst place you an be.  Forget the POH.  That is all about making good marketing numbers..... not about having an engine making it to TBO.

400 should be max CHT.  I agree with previous poster that 380 is what you should try and target.

[jlunseth]

I have the KFC 200.  You don't say how your GPS is connected to the AP, maybe it is a direct connection.  I have roll steering in between.  However, to fly an approach down the GS I need to turn the roll steering off once I am on the final approach.  I find that it is necessary to put the AP in APPCH mode before the GS centers.  The indicator needs to be at least one line high.  If I wait until it centers, it either won't couple at all, or will be trying to fly the plane up to the glide slope rather then staying level until GS intercept. 

One thought I had that I have not checked out with my GPS manual, is that the GPS switches sensitivity somewhere during an approach, from "Terminal Mode" which is 1.0 NM per degree of deviation, to "Approach" mode, which is 0.3 NM.  If the switching goes on right at this point, it could be exacerbating the AP's ability to find and couple to the GS.  As I said, I have not checked it yet in the manual.  The cure seems to be to put the AP in APPCH mode a little earlier, then it "knows" where it is with respect to the GS.

 

PS it also seems to help, when flying a coupled approach, to not use the Final Approach Course heading on the approach plate.  The GPS will give you a DTK which is often a couple of degrees different from the plate, and it helps to use the GPS's DTK rather than the plate.  Takes you right to the runway.  Again, I don't know why this is, it may be that the GPS's understanding of magnetic variation is different from the plate's, in any event it is better to use the GPS's DTK.