The cruise speed is largely dependent on engine size, tire size, and whether operating lean of peak or rich of peak. These all have an effect on fuel economy. My aircraft has an IO540 with PMAG ignitions, with 29" Alaskan Bushwheel tires. How the aircraft has been rigged also affects its cruise speed.
Whenever possible I operate the engine Lean of Peak. This reduces power and speed, but vastly increases efficiency.
A typical cruise setting would be 2200rpm and 23" MP with a fuel burn of 38 lph LOP. At lower altitudes this gives about 115 KTAS, and about 130 KTAS at higher altitudes.
The Bearhawk with an IO540 can easily be flown in normal cruise between 100 kts and 130 kts TAS. Even at low altitudes the speed can be increased to 130 kts by flying ROP at 55 lph.
The Bearhawk has a low wing loading. Any turbulence is felt more than in aircraft with higher wing loading's, particularly at the higher end of its speed range. If flying through turbulence, reducing speed often improves comfort.
Slow flight configuration
The aircraft can be slowed to 70 kts and with F2 selected it flies well with good visibility for a low weather configuration.
My aircraft and many Bearhawks have a fuel system with a L-BOTH-R-OFF selector. BOTH is the preferred position. This allows fuel from one tank to flood the ports even when the opposite side tank becomes unported. However even when operating in the BOTH position it is important to maintain balanced flight for a number of reasons. If the aircraft is flown even slightly out of balance, it will burn more fuel from the side that provides the higher head pressure. This can result in a flow between tanks via the fuel selector.
The Bearhawk has a particularly powerful rudder. Flying for any length of time while out-of-balance (uncoordinated) can cause fuel to flow between tanks. The fuel system itself is robust, but it does require to be flown in balance.
A Bearhawk safety bulletin states:
The Bearhawk Fuel System as shown in the Bearhawk Book is designed for use without a fuel pump.
If a fuel pump is used, extra care in flying is required so that neither main tanks become unported, as a fuel pump would rather suck air than fuel.
If one tank is very low and the other is not very low, set the fuel selector on the fullest tank and fly the plan as not to unport that tank.
I always plan to land with at least 40 liters of fuel remaining. This reduces the chance that the fuel lines become unported inadvertently. This gives a range of approximately 4 hours at 115kts (460nm plus reserves).
Some Bearhawks have auxiliary fuel tanks. These are an optional extra available from the kitset manufacturer that hold an additional 80 liters.
Center of Gravity
The Bearhawk is pleasant to fly at a CG forward of 20 inches. Aft of 20 inches it becomes quite sensitive in pitch and more sensitive in yaw. When flying near the aft limit of 22.5" it demands constant attention. At aft CG settings the pitch trim doesn't need much adjustment.
The aircraft is also more sensitive in yaw when landing with an aft CG.
Lean of Peak - Efficiency
As a rule of thumb, I plan on an average of 42 lph to include takeoff, climb and landing.
A higher level cruise results in a higher TAS, whereas a low level cruise results in better efficiency. This is largely because the engine uses a lot more fuel to climb to altitude (particularly if climbing full rich). Therefore all else being equal shorter flights are more efficient at low altitudes and longer flights are more efficient (and faster) at higher altitudes.
A typical full rich/full power fuel burn is 82 lph on the IO540. Lycoming recommend maintaining the mixture full rich until 5000ft, then leaning to maintain a constant EGT.
LOP settings typically result in an additional 100nm per tank of fuel for a 10 - 15 kt reduction in cruise speed. For example when LOP and burning 38 lph at 115 kts the theoretical maximum range (including reserve fuel) from full fuel tanks (205 liters) is over 600nm. However when ROP at 55 lph and 125 kts the maximum range is less than 500nm. That's a significant difference of around a 20% increase in efficiency. In addition the engine runs a lot cleaner and doesn't produce Carbon Monoxide.