Bearhawk "XHawk" Patrol

[jaredyates]

This is awesome Stefan, thank you for sharing! When it comes to tailwheel shimmy, I would also toss out that Bob's plane designs are not well-suited for ground operarions with the stick full aft. Many folks who learn in light taildraggers establish this habit, and in those planes it is important. But in the Bearhawks, if you can keep the stick neutral unless you need more force down in a specific case, you'll take a lot of strain off of the whole tailwheel assembly. You probably already know this but since you are also having some trouble with the spring fit I thought I would make sure you knew.

Also with regard to cold starts, I have found that the lycoming tyoe of engines definitely start much worse below 10 c or so, unless I preheat. Even more so if you are going to continue to run a single weight oil. The anti-splat heated sump plug has been working great for me so far. It is good, fast, and cheap, acheiving the impossible triad of excellence.

Your approach to testing and validation embraces the true spirit of homebuilding and responsible plane ownership, which should be a model and inspiration to us all.

[noema]

Thanks Jared. The anti-splat heated sump plug does look interesting. Ordered!

[rodsmith]

I really enjoyed your testing write up Stefan. I think most of us have some of the same issues with our newly built airplanes. What a beautiful place you live and fly in, reminds me that there are places with green valleys instead of brown ones. As Jared mentioned, the anti-splat heated sump plug is great for preheating the engine. Personally I try to never start the engine colder than 50 deg F. I know this is very conservative, but cold starts are where a lot of wear occurs. Also it takes so long to warm up the oil for takeoff. I have an unheated hangar. If I plan to fly on a cold morning (15 to 30F) I plug in the anti-splat heater with the insulated engine blanket installed before I go to bed. In the morning the oil is about 100F and the cylinders are around 80F. By the time I taxi to the end of the runway and do the run up, its ready to fly.

[noema]

Preheating is good practice, for sure. Interestingly the local flying Club flies their Lycomings fairly cold. They start, let it warm up until the engine stops to stutter when they advance the throttle and they take off. I would think the oil is at ~80F at this point. They don't have any modern avionics and completely lack engine oil indication at lower temps (old Cessna temp gauges). My procedure is currently to get up to 100-130F. The 0C lower limit is from the Lycoming manual also seems to match what feels off. At OAT close to 0C the startup starts to sound a bit harsh.

[Nev]

Another thumbs up here for the Antisplat sump heater. I run it through a GSM plug and activate it remotely a few hours before heading to the hangar.

Mine is fuel injected so we're probably not really speaking the same language, but it likes to be primed according to density altitude (the Dynon displays it) meaning that on a cold high pressure day I'm giving it significantly more priming than a warm low pressure day. I do the first start of the day with the mixture full rich.

Adding to Jared's excellent thoughts on the Bearhawk tailwheel handling, my shimmy issues went away when I began landing using a tail-low wheeler, keeping the tailwheel off for as long as possible (and then avoiding stick full aft where possible).

Regarding CHT's in the climb, there's a number of factors that all affect it. Some Bearhawks have the airflow outlet area constrained by the aft edge of the Vans air intake fiberglass scoop. It's large enough, but just. I've currently got a movable cowl flap fitted, with very good results. The digital manometer shows pressure differential is now controllable through the speed range at between 1 - 5.6" H2O, and between 1.6 - 4" at 90kts.

Another factor that has a very large influence on mine is where the mag timing is set. A set point of 20° makes it run cooler than when set at 25° BTDC and is most noticeable in the climb at full power. With the Pmags, they then automatically advance up to 9° beyond the set point.

[noema]

Yes, was also thinking hooking that preheater up to the internet is the way to go. I think my engine starts fine now but I am wondering if there are improvements to the procedure. The slight advancement to the BTDC is interesting. I will look into this.Thanks Nev!

[huntaero]

Great looking aircraft well done now it’s time to have fun