On 6/15/2023 4:53 PM, Flesner via KRnet wrote:
If one was to land with a cross wind in a slight crab - tail turned a
bit... if doing a 3 pointer, you would shoot off to the landing light
in microseconds if the wheel was not allowed to move differently from
the rudder.
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This went right over my head until I read it again this morning. If you
land with a slight crab, in relation to the aircraft movement over the
ground, in a tailwheel equipped airplane, you have just initiated a
ground loop. It doesn't matter which way the tailwheel is pointed. The
C.G. on a T.W. aircraft is behind the main gear and the farther off
center it is at touchdown the more difficult it is with control input /
braking to keep the airplane from switching ends. The heavy spot (C.G.)
wants to lead the pivot point (wheels on pavement). The narrower the
main gear and the greater the distance the C.G. is aft of the main gear
the more difficult it is to correct with control input / braking to
prevent a ground loop. The BF109 with it's narrow gear had a horrific
accident record on the ground. Cessna, in an attempt to tame the ground
handling of the C140, placed the main gear as close to the C.G. as
possible and in doing so lightened the load on the tailwheel to the
point that many pilots not used to using hydraulic toe brakes kept
putting the airplane on its nose. Cessna soon came out with a fix of
using a solid bar to mount the wheels several inches forward of the gear
legs. Some 140s carry that scar to this day while other were never
converted or were converted back to original and the pilot uses more
conservative braking pressures.
The only acceptable / safe way to land an airplane in a crab of any
amount is #1. in a trigear equipped airplane #2. with cross-wind or
beefed up gear designed to take the load. A trigear has the C.G. ahead
of the pivot point (wheels on pavement) and is self-aligning at
touchdown. That makes for lazy pilots. An Ercoupe without rudder
peddles has to land in a crab with crosswinds but the gear is beefed up
to handle the loads. Same on airliners with low slung engines. The B52
has main gear that rotate to allow the aircraft to land in a crabbed
position with the gear aligned with the direction of travel over the
ground. Some C195s have similar gear and possibly others. Many times
the pilot will align the aircraft with rudder moments before touchdown
to help eliminate the stress on the gear. This is very evident if you
watch airliners land in crosswinds.
Landing a tailwheel airplane in a crab can initiate a ground loop just
as pulling back on the stick can initiate a loop. A wing low side slip
with no lateral movement over the ground, nose pointed in the direction
of travel, is the only safe way to land a tailwheel airplane in a
crosswind and should be the practice of trigear pilots as well if the
aircraft is so designed.
Larry Flesner
Presented with the "Master Pilot Award" for 50 years of flying without
accident or incident. (this is the only time you'll see this tag line)
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