Flying the Bearhawk - Takeoff and climb
These notes are no substitute for getting good tail-dragger instruction from an experienced instructor or an experienced Bearhawk pilot.
There wasn't a lot written initially about how to fly the Bearhawk and so most of what I've written below is gleaned from others with more experience, from the forums, or simply from hours of practice and finding first what doesn't work, before finding what does work and learning the eccentricity's of a capable STOL taildragger.
The notes pertain specifically to my own aircraft with an IO540, VG's, a 3-bladed composite prop, empty weight of 1500lbs and empty CG of 8.3 inches. Position error is measured at a maximum of 3 kts at 50 KIAS and 1 kt at 40 KIAS (where 40 KIAS = 39 KTAS).
Taking off in the Bearhawk is relatively straightforward. There are 3 additional considerations:
- Over-the-nose visibility
- Stress being transmitted to the airframe through the tailwheel
- Damage from stones on the tailplane.
For this reason I choose to bring the aircraft up onto the main wheels for most takeoffs. The main shock struts seem very capable and effective on rough ground.
The Bearhawk 4-place tail feels very heavy. Because of this I start the takeoff roll with light back stick pressure, then apply forward pressure at about 20 kts to lift the tail. I only let the tail rise until the wheel just clears the ground. As it accelerates, pressure required on the stick quickly reduces to neutral. At this point I apply light back pressure and it gets airborne at minimum speed. That works well for a standard short takeoff.
For a normal takeoff and particularly on longer runways, it is easy to hold the main wheels on the ground longer, then allow it fly off when ready. This seems to work well in crosswinds of 10-15kts.
The Bearhawk gets airborne easily with 0,1,2,3 stages of flap. F4 is probably overkill and the flap limit speed (55kts) becomes an immediate issue.
Practically I find that either 2 or 3 stages of flap work best for me as it allows it to come up onto the main wheels more readily. With the IO540 it is important to reduce the flap shortly after getting airborne to avoid exceeding the flap limit speeds.
The aircraft then quickly accelerates though to 90kts. In the unlikely event of an engine failure close to the ground I prefer to have flaps retracted and be at a speed where the aircraft will glide comfortably, knowing that I can always put the flaps back out.
If there are obstacles to clear in the takeoff path, the Bearhawk can be climbed at 60kts ( Flaps 2 or 3), which provides a very steep angle of climb at full power. However on most takeoffs, obstacles don't really pose an issue because of the great climb performance. A normal takeoff provides a very good level of obstacle clearance while the aircraft is accelerated to 90kts.
Incidentally, the nose can be raised (rather uncomfortably) to around 25° while still remaining well above the stall speed. I've only tried this at a safe altitude. In practice I don't consider it to be safe - if the engine were to stop, by the time the nose was lowered I think the aircraft would potentially be below its stall speed. Maintaining a minimum 60kts for obstacle clearance when needed initially balances the risks. Once clear of obstacles I then lower the nose and accelerate while retracting flaps.
One issue with the IO540 can be engine cooling. This is mostly prevalent on a warmer day (above 20°c) when flying at slower speeds and higher AOA. However it is dependent on how the individual aircraft was built. (Mine has 130 ² inches of cooling air outlet area, with a medium sized cooling exit lip).
It's particularly noticeable when flying circuits in the summertime, or when practicing stalls or slow flight for an extended amount of time. The CHT's will all increase gradually, as will the oil temperature. The fix is simple - apply cruise power setting and accelerate to around 120kts in level flight for about 2 minutes.
Some Bearhawks have cowl flaps fitted. I've chosen not to and so far I find the engine temperature easy to manage.
Typical takeoff sequence
I slowly apply full power (over a 3 second period) and after 2 more seconds push the stick forward. As the aircraft comes up on the main wheels, I move the stick rearward to hold the cowling visually on the end of the runway. This allows it to fly off just above the stall speed. Shortly after airborne I retract the flaps as it accelerates to 90kts. Next I set 2500 rpm (keep full power), fuel pump off (check pressure), and further accelerate if desired to 120kts.
An IO540 powered Bearhawk climbs comfortably at speeds from 70kts - 120kts. Practically, 90kts - 110kts provides a very good cruise climb depending on the rate of climb desired.
One of the main determinants of climb speed is engine cooling - specifically CHT's and oil temperature. Being Amateur Built aircraft, there is a variation between each aircraft. When my aircraft initially flew I needed to climb at 110 - 120kts on a warm day with mixture at full rich, to provide sufficient engine cooling. This gives a ROC of approximately 5-700 ft/min.
After fitting a larger exit cooling lip that decreased the CHT's, I was able to climb at 90kts and gain a higher rate of climb. At 90kts and 2300lbs the ROC is around 1500 ft/min, and fuel burn is 82 lph. Because the cruise altitude is reached much quicker it results in significantly lower fuel consumption overall.
Test flying wrap up
This post is from Neville's Bearhawk