Retractable gear assemblies are very attractive due to the better aerodynamics
and looks when in flight. They also imply a "coolness" factor that excites the
male ego and denotes a "real pilot".
Couple of points to keep in mind when thinking about retracts:
First: they tend to add considerably to the empty weight of the
airplane, something that all have found out drastically effects the KR.
Second: they tend to be complex in nature and require more frequent
attention than their opposite fixed gear.
Third: when they malfunction, and they will, it usually ends up a
bad day for the pilot unless a totally reliable manual failsafe is also
available like a gravity extension or manual crank handle.
Fourth: in our speed ranges they typically do NOT give
significantly more speed for the added weight and complexity, as compared to
the benefits of a well faired fixed gear.
Fifth: If you don't have considerable complex time, your insurance
if you can get it will be alot higher, and odds are that you will have a gear
up landing. The only gear up landing that I would look forward to in my KR
would be ditching in water. Any other time I want the gear down. You can't ever
forget to put the gear down in a fixed gear airplane.
Sixth: it will significantly increase construction time.
Seventh: it can drastically effect the CG in flight when retracted
due to the moving gear if the position changes relative to the down position.
Say your nose gear retracts backwards, you have to account for this rearward
movement of that weight when calculating your weight and balance for the
particular flight. This might require creating hard points on the aircraft and
weighing the plane with gear down, and then gear up to accurately know what
that changing moment is. An example of these calculations can be found in the
Piper Arrow, or Cessna 172RG Operating Manuals.
If the gear system does not completely leave the slipstream, like the
original KR2 does not, then you will be adding alot of weight without gaining
the aerodynamic benefits of the cleaner exterior, so no real speed gain will be
had, but the chances of problems have been increased. Best comparison I know
of that would be akin to a KR2 with retracts, vs one with a well faired fixed
gear is the Piper Arrow, vs the Piper Archer. Both have 200hp engines, with
constant speed props. However, the only real difference between the two is the
Arrow has retracts and the Archer does not. The Archer is faster than the
Arrow by about 7-10knots depending on altitude flown and climbs significantly
better, and has more payload due to the lower empty weight. So the overall fun
factor and utility of the aircraft is higher in the Archer than the Arrow AND
it insures for less, and uses fewer gallons per hour due to the lower overall
gross weight given the same cruise speed comparison to the Arrow.
Just some thoughts....
Colin & Bev Rainey
KR2(td) N96TA
Sanford, FL
crain...@cfl.rr.com
http://kr-builder.org/Colin/index.html
