DVA

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About DVA

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    Senior Member

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  • Website URL
    www.vanallenairmotive.com

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  • Gender
    Male
  • Location
    Allentown PA
  • Reg #
    N9153Z
  • Model
    M20M

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  1. I written a few posts on running the Bravo LOP, I think if you search for that you'll find them. I would love to hear your comments. Dave
  2. Hi! I'm at KXLL nearly everyday which should be a short hop for you. I'll let others attest to the fact that I'm very comfortable LOP and I'd be happy to help answer any questions you might have. Dave
  3. Lol. I'm not taking responsibility for your new FB addiction. :-) The picture of the wastegate is upside down due to the way the borescope entered the area. So you are seeing lubricant only on the top where the actuator connects to the valve. There is nothing to lubricate on the bottom side.
  4. Pete, that sounds like the normal variations you see. Mine is the same. It will really get jittery if its hot, indicating some vaporization. That's when you need to activate the electric boost pump to help clear it out.
  5. We use the borescope extensively to look at things that would otherwise require expensive and time consuming disassembly. I also believe in Mike Busch's theory of MIF - the maintenace induced failure, using the borescope can reduce the chances of MIFs while saving owners a lot of time and money. I thought I'd share a video borescope look at the hot section of a turbo on a M20M. https://www.facebook.com/vanallenairmotive/videos/463022524065352/ Enjoy. DVA
  6. This is the first time I've ever heard of a restriction like that from an insurance company on a particular aircraft. May I ask what insurance carrier?
  7. I'd be investigating a few things here, some of which others have pointed out. 1) Make sure your soft baffling is sealing properly and the inter-cylinder baffles are installed properly (and as odd this seems, also actually there) 2) Fly a test profile per SAVVY's instructions to do both an injector flow test (GAMI spread) and an in-flight lean Mag check. You can get the instructions to do that http://content.savvyanalysis.com/static/pdf/SavvyAnalysisFlightTestProfiles.pdf here. If you can, upload the results from your EDM to Savvy (it's free) and share the results to us. 2a) Confirm that at full throttle / full mixture during the ground roll you are making no more than 36-37" of MP, 2575ish RPM, and at least 30 GPH of fuel flow. Never lean this engine in the climb. You should be flowing at least 25 GPH as you ascent in a power climb. 3) I would not be concerned about going a bit over 400 on an occasional basis, such as during a climb. Do however have full throttle and open cowl flaps when doing it. What you want to watch for in CHT are quick and continually rising temps above 400. So if you get to say 410-420 in the climb and it settles there, no big deal. There is no absolute magic about the number "400" verses 410 or 402. The CHT temp guidance is based on some factual metallurgy centered around a half-way point in the specific yield strength of aluminum vs temp and it is good guidance. It is not however, exact guidance. 4) Please consider not arbitrarily setting TIT. 1625 may be correct, but prove it. TIT varies with a number of factors, altitude, fuel flow, MP, RPM, Trump, (there I go again!) etc. Without GAMI injectors, you should use run this engine ROP at 100 dF rich side of TIT. I would not trust Peak TIT without GAMIs or evidence that my individual EGTs are all peaking together as peak TIT can easily place some cylinders in a detonation zone at higher power settings. (28" MP and above) 5) After you confirm those things (others here may suggest more) fly it per the POH power settings and see if it makes the book numbers for speed? If it does, you're in fine shape. (Deduct a full 8-10 knots off book if you have TKS) Let us know what you find. Dave
  8. It sure was different! I'm taking a reading course next week, I'll get better at this ... lol Yes, when I lean I get a small change in MP, on the order of .5 +/- I ignore it.
  9. My other point was that the DC, when adjusted correctly, all else considered equal, will allow the Bravo to maintain MP pretty tightly up to the the FL20's. Sadly most are not adjusted correctly from the start.
  10. It’s not really a Bravo thing, but most of the Bravo’s are not set up using the procedure outlined in the Lycoming MM for adjusting the density controller - rather it is just eyeballed and set by a few ground runs. The density controller (DC) must be adjusted properly for the rest of the system to work well and track the changes in, well density, which can be influenced by a ton of things: temperature, humidity, mixture, Trump, (sorry that just blurted right out for some reason), etc. I have seen first hand people setting the DC so that (on that day of tweaking) they produce 38” at full throttle because they believe that’s what it should be because that is the “max”. They are dead wrong, they are setting the DC incorrectly and they are causing the system to be inherently unstable as a result. The DC is set by properly measuring inlet air temperature at the correct location and adjusting the DC to produce a MP in concert with that temp on the chart for the AF1B. This is most often no where near 38” on the ground roll and more often closer to 35” at WOT; I wrote extensively about this elsewhere. If your MP on a Bravo is 37-38” on take off on a standard day I can virtually guarantee that you will not make critical altitude before you run out of boost and start to bootstrap due to the incorrect DC setting. That said, the combination of turbo control systems on the Bravo make it more difficult to balance than single systems, hence the variations you see Bravo to Bravo. I lose/gain about .5” or so +/- as I ascend or descend from the low FL20’s to earth, and often will not adjust anything at all. Some birds are better some worse.
  11. We're in Allentown PA at KXLL which is right along your route. I'd be happy to chat if you'd like. Best regards, Dave 484-224-0105
  12. It's a Bravo, but this is where the probe is located.
  13. People often forget that the mixture knob is a perfect secondary source of power control. I would first use that to get my power down to an approach-flyable level and would only cut power by the mags in a much more dire set of straits. You can practice this easily.
  14. Thanks for the compliment! First, before I go down any paths (or rabbit holes lol) we have to remember that we do not have a direct “Manifold Pressure” control on our airplanes, we have an indirect throttle control that we choose to monitor via a MP gauge. So when we try to “lock” MP in one place we are using devices (density controllers, diff controllers, etc) that don’t actually adjust all the right stuff - just some stuff. That said, anyone who has flown a manual waste-gate engine (Twin Comanche) really appreciates the convenience and safety of the somewhat sloppy but mostly okay automatic boost controllers you and I fly behind. So why the drop in MP you see as fuel flow changes? ... mainly for the reason above. As you lean the mixture you change the dynamics of actually what propels the hot side of the turbo - pressure, air density and heat of the exhaust gases. All three combine to provide the energy, mostly thermodynamic, needed to spin the turbine. Add to that the tight relationship of the cold side changes that are made as a result of changing the hot side and you have an inherently unstable positive feedback loop. Tracking these different functions and how they affect the turbo system requires a lot more brain power than the simple density / differential and/or absolute controllers we fly with to provide precise control. I think I have my Bravo tuned up pretty well, and I get similar variations as you do. When I adjust mixture LOP and the MP drops an inch or two, I just bump it up with throttle and turn up the XM classic hits and fly on. There is a logarithmic widening of the detontion margin on the lean side of peak, so even 10-15 dF past peak on the lean side puts you in a fine safe area. Just a note, I don’t run LOP all of time, when I want to go TAS fast I run 100-125dF ROP in cruise, but I nearly always run LOP in the decent, approach and landing portions which is usually at least 1/3 of the trip time. I would say I have run 50/50 LOP vs ROP so far, and I’ve my Bravo now for over a year. A recent look with the bore scope showed a carbon free clean set of heads and pistons, no valve issues, and picture perfect spark plugs. I routinely run TiT at 1650dF up high and a little lower down below and the exhaust is in fine shape. DVA
  15. You'll likely get vectors east to OTT and then east out of the SFRA PALEO or WHINO gate if VFR to keep you clear of BWI south arrivals. Then you can turn north. If IRF you might be able to get more north.