曝光臺 注意防騙 網曝天貓店富美金盛家居專營店坑蒙拐騙欺詐消費者

tailwheel or the empennage as the line is deployed. Stiffening of the line may be accomplished by
working a 2-foot length of stiff plastic garden hose over the line. The hose is then carefully heat
formed over the knots at the ring. See Figure 2-1, Examples of a Plastic Garden Hose Installation.
Devices, such as spring keepers, can be used to hold the grapple line away from the tailwheel or the
tail control surfaces until the grapple line is released. The spring keeper is attached to the bottom of
the horizontal stabilizer or the empennage bracing wire into which the grapple line is connected.
The configuration of some aircraft may not permit the use of keepers to hold the grapple line away
from the airframe. As an alternate method, the use of a rudder guard or Vee bar (if a multiple rope
system is used), may be helpful. This device is attached to the aft fuselage and serves to guide the
grapple line away from the tailwheel or control surface horns during deployment. See Figure 2-2,
Examples of a Vee Bar.
The pilot should avoid uncoordinated or abrupt maneuvers during grapple line deployment. Trained
ground support personnel should be available during banner pickup operations, and be briefed to
observe the aircraft and inform the pilot if the line appears to be trailing abnormally. Picking up a
banner with a loosely, snarled line will only tighten it and complicate the problem.
BANNER PICKUP. The banner pickup is the most critical portion of a banner tow operation. A
typical flight begins by taking off with the grapple hook assembly stowed. Upon reaching a safe
altitude, the pilot will deploy the grapple hook and allow it to trail aft of the aircraft. See
Figure 2-3, Examples of Typical Towrope Configuration, Stowed for Deployment.
A shallow approach is conducted perpendicular to the pickup-masts in an effort to snag the towline
loop with the grapple hook. As the masts are reached, the airplane is rotated into a steep climb to
assure the banner will be peeled off the ground instead of jerked off at an acute angle, depending
upon aircraft performance capabilities. As the banner is peeled off the ground, back pressure is
gradually reduced until the airplane is climbing at a normal angle with the banner in tow.
The approach to the pickup-masts should be flown appropriate to the performance characteristics of
the aircraft. Care must be taken to avoid snagging the towline with the airframe. An approach that
is both too low and too slow may result in the grapple hook bouncing off the ground. The length of
2-1
the grapple hook and line assembly should be limited to a length that will not allow the hook to
strike the cockpit area of the airplane if it should come up over the fuselage. Grapples contacting a
hard surface have been known to bounce upward and forward, over the airplane, snarling the
horizontal stabilizer or a wing.
Stalls during the banner pickup procedure constitute one of the more frequent causes of banner tow
operational accidents. A stall occurs when an airfoil reaches a critical angle of attack and is a
function of wing loading, independent of airspeed. In fact, an excessively abrupt rotation of an
airplane during a pickup, or a snap or steep turn after a missed pickup, may be sufficient to
precipitate an accelerated stall.
NOTE: The formula for stall is the square root of the load factor times the normal stall speed.
Gradually reducing back pressure while in the climb as the banner is picked up increases the margin
from the stall threshold by decreasing the wing loading and consequently the angle of attack.
FLYING WITH A BANNER IN TOW. The accidental release of a banner in flight may not be
hazardous to the tow plane or crew but it may pose a threat to people and property on the surface.
Banner towlines should be examined carefully for flaws before each towing day. Grapple hooks
should also be examined for cleanliness and smoothness. Any surface irregularities on a hook can
act as an abrasive and degrade the towline loop during the pickup as the line moves laterally over
the hook while tension on the line is increased. Whenever possible, banner material and lines
should be of non-conductive material. This reduces the risk of shorting out power lines in the case
where a banner is released over power lines by accident.
LANDING WITH BANNER IN TOW. Should a malfunction make it impossible to release the
banner, it is generally uneventful if a hard surface runway is used. However, a special technique
can be used if the landing is attempted on a sod or dirt runway. If the masthead and banner lay
down on the sod runway, each blade of grass folds over the mast and each individual letter pole on
lettered banners causes drag. The pilot needs to be aware that the masthead may dig into the soft
　
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：Banner Tow Operations(3)